| 1. |
- Adolfsson, Göran, 1981, et al.
(författare)
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Spectral engineering of semiconductor Fabry–Perot laser cavities in the weakly and strongly perturbed regimes
- 2010
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 27:1, s. 118-127
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Tidskriftsartikel (refereegranskat)abstract
- By inserting index perturbations at certain positions along a semiconductor Fabry–Perot laser cavity thethreshold gain for one or several of the longitudinal cavity modes can be selectively lowered to facilitate, e.g.,single-mode or two-color operation. Previous design methods were limited to a fairly small number of perturbations,leading to only weakly perturbed cavities and thus a limited freedom in tailoring the spectral propertiesof the laser. In our approach we fully account for all multiple-reflection events and use a search spacethat permits any distribution of the locations and lengths of the perturbations. We are therefore able to designcavities with almost arbitrary spectral properties with very low threshold gain values for, e.g., the lasingmodes of a two-color cavity. Constraining the design by reducing the geometrical freedom, which can be used toincrease the smallest feature size to simplify fabrication, we seamlessly approach the weakly perturbed regimewhile maintaining much of the freedom for spectral engineering.
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| 2. |
- Akram, Nadeem, 1971-, et al.
(författare)
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Experimental characterization of high-speed 1.55 mu m buried heterostructure InGaAsP/InGaAlAs quantum-well lasers
- 2009
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 26:2, s. 318-327
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Tidskriftsartikel (refereegranskat)abstract
- Detailed experimental characterization is performed for 1550 nm semi-insulating regrown buried heterostructure Fabry-Perot (FP) lasers having 20 InGaAsP/InGaAlAs strain-balanced quantum wells (QWs) in the active region. Light-current-voltage performance, electrical impedance, small-signal response below and above threshold, amplified spontaneous emission spectrum below threshold and relative intensity noise spectrum are measured. Different laser parameters such as external differential quantum efficiency eta(d), background optical loss alpha(i), K-factor, D-factor, characteristic temperature T-0, differential gain dg/dn, gain-compression factor epsilon, carrier density versus current, differential carrier lifetime tau(d), optical gain spectrum below threshold, and chirp parameter alpha are extracted from these measurements. The FP lasers exhibited a high T-0 (78-86.5 degrees C) and very high-resonance frequency (23.7 GHz). The results indicate that appropriately designed lasers having a large number of InGaAsP well/InGaAlAs barrier QWs with shallow valence-band discontinuity can be useful for un-cooled high-speed direct-modulated laser applications.
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| 3. |
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| 4. |
- Ali, Mona, et al.
(författare)
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Measuring the nonlinear optical properties of indium tin oxide thin film using femtosecond laser pulses
- 2020
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 37:11, s. A139-A146
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the nonlinear optical properties of indium tin oxide (ITO) thin film coated on soda-lime glass substrate using the z-scan technique. With 100 fs laser pulses, the nonlinear absorption coefficient and nonlinear refractive index are measured at different excitation wavelengths and at different incident intensities. The nonlinear optical absorption shows a competition between saturable absorption and reverse saturable absorption at the different excitation wavelengths and incident intensities. A transition from saturable to reverse saturable absorption was observed with increasing excitation wavelengths. The measured nonlinear refractive index was found to be dependent on wavelength with a maximum value of 5.34 x 10(-12) cm(2)/W at wavelength of 900 nm.
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| 5. |
- Altucci, C, et al.
(författare)
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Influence of atomic density in high-order harmonic generation
- 1996
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 13:1, s. 148-156
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated how high-order harmonics generated in rare gases depend on the atomic density. The peak and the profile of the atomic density in the interaction region were measured as a function of the backing pressure and the distance from the nozzle by a differential interferometry technique, The conversion efficiency for the harmonics in the plateau was found to increase approximately quadratically over the entire range of peak pressures investigated (3-80 mbar). The intensity of the harmonics in the cutoff region, in contrast, increased only until an optimum peak pressure was reached, beyond which it decreased. This optimum peak pressure was found to be dependent on both the laser intensity and the process order. To understand this effect, we have performed extensive propagation calculations of both the fundamental and the harmonic fields, using ionization rates and dipole moments from a tunnel ionization model. We obtained good agreement with the experimental results. The observed effect is attributed to ionization-induced defocusing of the fundamental laser beam, which reduces the peak intensity obtained in the medium and shortens the extent of the plateau. (C) 1996 Optical Society of America
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| 6. |
- Andersson, Dan, 1966, et al.
(författare)
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Wave-breaking-free pulses in nonlinear-optical fibers
- 1993
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 10:7, s. 1185-1190
-
Tidskriftsartikel (refereegranskat)abstract
- A qualitative as well as quantitative investigation is made of the conditions for avoiding wave breaking during pulse propagation in optical fibers. In particular, it is shown that pulses having a parabolic intensity variation are approximate wave-breaking-free solutions of the nonlinear Schrodinger equation in the high-intensity limit. A simple expression for the compression factor of a fiber-grating compressor based on parabolic pulses is also derived.
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| 7. |
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| 8. |
- Augulis, Ramunas, et al.
(författare)
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Detector and dispersive delay calibration issues in broadband 2D electronic spectroscopy
- 2013
-
Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 30:6, s. 1770-1774
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Tidskriftsartikel (refereegranskat)abstract
- Precision of two-dimensional (2D) electronic spectroscopy can be affected by imprecise calibration of the optical spectrometer and coherence time delay line. This would result in 2D spectral line shapes with twisted phase, where absorptive and dispersive parts of the signal are mixed and unrecoverable. We demonstrate two efficient and easily implementable techniques for precise spectrometer and wedge-based delay line calibration that assure acquisition of correct spectral phase in 2D spectroscopy measurements. (C) 2013 Optical Society of America
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| 9. |
- Axner, Ove, et al.
(författare)
-
Ability of gas modulation to reduce the pickup of drifts in refractometry
- 2021
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 38:8, s. 2419-2436
-
Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology for assessment of gas refractivity, molar density, and pressure that, by a rapid gas modulation, exhibits a reduced susceptibility to various types of disturbances. Although previously demonstrated experimentally, no detailed analysis of its ability to reduce the pickup of drifts has yet been given. This work provides an explication of to what extent modulated refractometry in general, and GAMOR in particular, can reduce drifts, predominantly those of the cavity lengths, gas leakages, and outgassing. It is indicated that the methodology is insensitive to the linear parts of so-called campaign-persistent drifts and that it has a significantly reduced susceptibility to others. This makes the methodology suitable for high-accuracy assessments and out-of-laboratory applications.
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| 10. |
- Axner, Ove, et al.
(författare)
-
Ability of gas modulation to reduce the pickup of drifts in refractometry
- 2021
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optica Publishing Group. - 0740-3224 .- 1520-8540. ; 38:8, s. 2419-2436
-
Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology for assessment of gas refractivity, molar density, and pressure that, by a rapid gas modulation, exhibits a reduced susceptibility to various types of disturbances. Although previously demonstrated experimentally, no detailed analysis of its ability to reduce the pickup of drifts has yet been given. This work provides an explication of to what extent modulated refractometry in general, and GAMOR in particular, can reduce drifts, predominantly those of the cavity lengths, gas leakages, and outgassing. It is indicated that the methodology is insensitive to the linear parts of so-called campaign-persistent drifts and that it has a significantly reduced susceptibility to others. This makes the methodology suitable for high-accuracy assessments and out-of-laboratory applications
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| 11. |
- Axner, Ove, et al.
(författare)
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Ability of gas modulation to reduce the pickup of fluctuations in refractometry
- 2020
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : OSA - The Optical Society. - 0740-3224 .- 1520-8540. ; 37:7, s. 1956-1965
-
Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry is a technique for assessment of gas refractivity, density, and pressure that, by a rapid modulation of the gas, provides a means to significantly reduce the pickup of fluctuations. Although its unique feature has previously been demonstrated, no detailed explication or analysis of this ability has yet been given. This work provides a theoretical explanation, in terms of the length of the modulation cycle, of the extent to which gas modulation can reduce the pickup of fluctuations. It is indicated that a rapid modulation can significantly reduce the influence of fluctuations with Fourier frequencies lower than the inverse of the modulation cycle length, which often are those that dominate. The predictions are confirmed experimentally
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| 12. |
- Baev, A., et al.
(författare)
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Bi-directional description of amplified spontaneous emission induced by three-photon absorption
- 2005
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 22:2, s. 385-393
-
Tidskriftsartikel (refereegranskat)abstract
- A semiclassical dynamic theory of the nonlinear propagation of a few interacting intense light pulses is applied to study the nonlinear counterpropagation of amplified spontaneous emission (ASE) induced by three-photon absorption of short intense laser pulses in a chromophore solution. Several important results from the modeling are reached for the ASE process developing in the regime of strong saturation. Accounting for ASE in both forward and backward directions with respect to the pump pulse results in a smaller efficiency of nonlinear conversion for the forward ASE compared with the case in which forward emission is considered alone, something that results from the partial repump of the absorbed energy to the backward ASE component; the overall efficiency is nevertheless higher than for the forward emission considered alone. The efficiency of nonlinear conversion of the pump energy to the counterpropagating ASE pulses is strongly dependent on the concentration of active molecules so that a particular combination of concentration versus cell length optimizes the conversion coefficient. Under certain specified conditions, the ASE effect is found to be oscillatory; the origin of oscillations is dynamical competition between stimulated emission and off-resonant absorption. This result can be considered one of the possible explanations of the temporal fluctuations of the forward ASE pulse [Nature 415, 767 (2002)].
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| 13. |
- Baev, Alexander, et al.
(författare)
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Upconverted lasing based on many-photon absorption : an all dynamic description
- 2004
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 21:2, s. 384-396
-
Tidskriftsartikel (refereegranskat)abstract
- A theory is developed for the propagation through a nonlinear medium of strong pump and amplifiedspontaneous-emission pulses. The theory is based on a solution of the density matrix equations that aims at providing an adequate treatment of the nonlinear polarization of the material without addressing the Taylor expansion over the powers of intensity. The theory has been applied for modeling of three-photon absorption induced upconverted stimulated emission of organic molecules in solvents. Numerical results are presented for the organic chromophore 4-[N-(2-hydroxyethyl)-N-(methyl)amino phenyl]-4'-(6-hydroxyhexyl sulfonyl) stilbene dissolved in dimethyl sulfoxide. The results are in good agreement with available experimental results.
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| 14. |
- Basieva, Irina
(författare)
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Theoretical method for states dynamics and entanglement optimization in bichromatically driven clusters of two and four resonantly interacting particles
- 2013
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:7, s. 1804-1814
-
Tidskriftsartikel (refereegranskat)abstract
- Bichromatic laser pumping is an effective tool to control (e. g., to drive into an entangled state) solid-state quantum bits of different nature. For clusters of resonantly interacting ions under bichromatic laser pumping, we present a theoretical approach and approximate analytical solution for quantum states dynamics. The solution provides an optimal ratio of laser pulse intensities needed for creating the maximally entangled states and performing quantum gates. Numerical simulation corroborates the analytical results. (C) 2013 Optical Society of America
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| 15. |
- Berezovsky, Vladimir, et al.
(författare)
-
Effect of dipole-dipole interactions between atoms in an active medium
- 2008
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 25:3, s. 458-462
-
Tidskriftsartikel (refereegranskat)abstract
- On the basis of the results of numerical modeling, it is shown that dipole-dipole interactions among atoms in the active medium strongly influences the character of the associated superradiation. The main effect is to make the nuclear subsystem behave chaotically. Its strength increases with the atom density and leads to the suppression of distant collective correlations and superradiation. Near correlations between the atoms are established, causing a confinement effect: a shielding of radiation in the active medium.
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| 16. |
- Berg, R, et al.
(författare)
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Medical Transillumination Imaging Using Short-pulse Diode-lasers
- 1993
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 32:4, s. 574-579
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Tidskriftsartikel (refereegranskat)abstract
- The recently introduced time-resolved technique for enhanced medical transillumination imaging has been demonstrated for the important case of a diode laser transmitter. This type of gated-viewing technique utilizes early received light only to reject multiply scattered, delayed light, normally blurring the image. Human breast-cancer detection is demonstrated in vitro, and the observations are explained by using theoretical modeling and tissue phantom experiments.
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| 17. |
- Björk, Gunnar, et al.
(författare)
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Mutually unbiased bases and discrete Wigner functions
- 2007
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 24:2, s. 371-378
-
Tidskriftsartikel (refereegranskat)abstract
- Mutually unbiased bases and discrete Wigner functions are closely but not uniquely related. Such a connection becomes more interesting when the Hilbert space has a dimension that is a power of a prime N=d(n), which describes a composite system of n qudits. Hence, entanglement naturally enters the picture. Although our results are general, we concentrate on the simplest nontrivial example of dimension N=8=2(3). It is shown that the number of fundamentally different Wigner functions is severely limited if one simultaneously imposes translational covariance and that the generating operators consist of rotations around two orthogonal axes, acting on the individual qubits only.
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| 18. |
- Boudrioua, A., et al.
(författare)
-
Nonlinear optical properties of (H+,He+)-implanted planar waveguides in z-cut lithium niobate : annealing effect
- 2001
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 18:12, s. 1832-1840
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Tidskriftsartikel (refereegranskat)abstract
- Reflection second-harmonic generation from the polished waveguide end face was used to investigate the nonlinear properties of LiNbO3-implanted waveguides fabricated by use of 2-MeV He+ and 1.5-Mev H+ beams. Results were compared with waveguides obtained by protonic exchange in benzoic acid, In contrast to the exchanged sample where the nonlinearity is strongly reduced, the implanted samples showed that the guiding region presents rather the same response as the substrate. The area where the optical barrier is located showed a strongly enhanced second-harmonic signal that was likely to be due to structural modifications in this area. Moreover, the investigation of the annealing effect showed strong interaction of protons with the lattice compared with that of He+ ions.
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| 19. |
- Cai, Yangjian, et al.
(författare)
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Coherent and partially coherent dark hollow beams with rectangular symmetry and paraxial propagation properties
- 2006
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 23:7, s. 1398-1407
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Tidskriftsartikel (refereegranskat)abstract
- A theoretical model is proposed to describe coherent dark hollow beams (DHBs) with rectangular symmetry. The electric field of a coherent rectangular DHB is expressed as a superposition of a series of the electric field of a finite series of fundamental Gaussian beams. Analytical propagation formulas for a coherent rectangular DHB passing through paraxial optical systems are derived in a tensor form. Furthermore, for the more general case, we propose a theoretical model to describe a partially coherent rectangular DHB. Analytical propagation formulas for a partially coherent rectangular DHB passing through paraxial optical systems are derived. The beam propagation factor (M-2 factor) for both coherent and partially coherent rectangular DHBs are studied. Numerical examples are given by using the derived formulas. Our models and method provide an effective way to describe and treat the propagation of coherent and partially coherent rectangular DHBs.
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| 20. |
- Castello-Lurbe, David, et al.
(författare)
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Inverse dispersion engineering in silicon waveguides
- 2014
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 31:8, s. 1829-1835
-
Tidskriftsartikel (refereegranskat)abstract
- We present a numerical tool that searches an optimal cross section geometry of silicon-on-insulator waveguides given a target dispersion profile. The approach is a gradient-based multidimensional method whose efficiency resides on the simultaneous calculation of the propagation constant derivatives with respect to all geometrical parameters of the structure by using the waveguide mode distribution. The algorithm is compatible with regular mode solvers. As an illustrative example, using a silicon slot hybrid waveguide with 4 independent degrees of freedom, our approach finds ultra-flattened (either normal or anomalous) dispersion over 350 nm bandwidth in less than 10 iterations.
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| 21. |
- Cattani, F., et al.
(författare)
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Effect of self-phase modulation in chirped-pulse-amplification-like schemes
- 1999
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America (OSA). - 0740-3224 .- 1520-8540. ; 16:11, s. 1874-1879
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Tidskriftsartikel (refereegranskat)abstract
- A detailed analytical investigation is made of the effect of nonlinear self-phase modulation in chirped-pulse-amplification-like schemes. It is demonstrated that self-phase modulation in the amplifier between the stretcher and the compressor breaks the dispersive sign symmetry of the configuration. This implies that, although self-phase modulation is usually considered a deleterious effect, different situations are possible, depending on the parameter regimes considered. In particular, the influence of self-phase modulation on the low-intensity wings of the compressed pulse may be more or less deleterious, depending on the dispersive sign combination of the stretcher and the compressor; in certain parameter regimes, it may in fact even enhance the pulse compression.
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| 22. |
- Cavalcanti, GH, et al.
(författare)
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Vacuum ultraviolet spectrum of six-times ionized xenon, Xe VII
- 1997
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Ingår i: JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS. - : OPTICAL SOC AMER. - 0740-3224. ; 14:10, s. 2459-2462
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The theta-pinch spectrum of six-times ionized xenon, Xe VII, has been recorded in the vacuum ultraviolet region of 300-1300 Angstrom, and 27 new transitions have been identified as combinations between levels of the 5p2-5p5d and 5s5d-5p5d transition array
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| 23. |
- Chen, Shihua, et al.
(författare)
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Compression of high-energy ultrashort laser pulses through an argon-filled tapered planar waveguide
- 2011
-
Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 28:5, s. 1009-1012
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Tidskriftsartikel (refereegranskat)abstract
- We propose a hollow tapered planar waveguide for compression of high-energy ultrashort laser pulses. Direct measurements suggest that it seems to find a very good trade-off among the energy throughput, the beam focusability, and the pulse compressibility. With a Ti:sapphire laser pulse of 12.0 mJ and 40 fs, our experiment produces an output pulse of 9: 4 fs duration with energy 9: 1 mJ (transverse magnetic mode) or 10: 0 mJ (transverse electric mode) in argon, each exhibiting a nice spatial mode. To evaluate such a tapered waveguide, the linear wave propagation theory and the solution to its complex propagation constant are also presented. c 2011 Optical Society of America
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| 24. |
- Cui, Yanxia, et al.
(författare)
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Exciting multiple plasmonic resonances by a double-layered metallic nanostructure
- 2011
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 28:11, s. 2827-2832
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Tidskriftsartikel (refereegranskat)abstract
- By placing a metallic layer of a periodic nanostrip array above a metallic layer of a periodic nanogroove array with a separation of 120nm, we obtain a triple-band thin film absorber with all its resonant wavelengths displaying absorptivity greater than 90%. Through a systematic study of the current compound structure, we find these three absorption peaks mainly depend on some simple resonances, i.e., the modes supported by the nanostrip array in the top layer, the nanogroove array in the bottom layer, and the horizontal cavity between the two layers. In addition, we show that this kind of absorber is quite robust and fairly insusceptible to the parallel shift between the two different layers. This study should contribute to the design of thin film absorbers/ emitters.
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| 25. |
- Cui, Y. X., et al.
(författare)
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Nanocavity antenna array for enhancing extraordinary optical transmission of light through a metallic nanoslit
- 2009
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 26:11, s. 2131-2135
-
Tidskriftsartikel (refereegranskat)abstract
- The transmission of light through a single nanoslit milled in the metallic film is enhanced by using an array of nanocavity antennas. It is shown that transmission efficiency through a 25-nm-wide silver nanoslit can be enhanced to eta = 151 when six pairs of nanostrips are placed 50 nm away from the input surface of the silver film at wavelength lambda(0) = 1 mu m. The influences of both the nanoslit position and the slit-to-strip distance on the extraordinary transmission are investigated, and the physical mechanism is explained.
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| 26. |
- Dai, Daoxin, et al.
(författare)
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Highly sensitive sensor based on an ultra-high-Q Mach-Zehnder interferometer-coup led microring
- 2009
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 26:3, s. 511-516
-
Tidskriftsartikel (refereegranskat)abstract
- A high-Q Mach-Zehnder interferometer (MZI)-coupled microring is presented for optical sensing with high sensitivity and a large measurement range. By optimizing the length difference, between the two arms of the MZI coupler, the MZI-coupled microring with a high-Q factor and high extinction ratio is obtained. In the present example, the Q factor of the designed silicon-nanowire-based microring is as high as 1.8 x 10(5) when the silicon nanowire has a propagation loss L=2 dB/cm. Due to this high-Q factor, the sensitivity for the change Delta n of the effective refractive index is about 10(-5)-10(-6) by measuring the shift of the resonant wavelength. Because of the wavelength dependence of the coupling ratio of the MZI coupler, it is possible to have only one resonant wavelength with a high extinction ratio in a very large wavelength span [i.e., the quasi-free spectral range of the MZI-coupler microring], which offers a very large measurement range covering the refractive index change
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| 27. |
- Dai, Daoxin, et al.
(författare)
-
Numerical analysis of silicon-on-insulator ridge nanowires by using a full-vectorial finite-difference method mode solver
- 2007
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 24:11, s. 2853-2859
-
Tidskriftsartikel (refereegranskat)abstract
- The characteristics of silicon-on-insulator (SOI) ridge waveguides are analyzed by using a cylindrical full-vectorial finite-difference method mode solver with a perfectly-matched layer treatment. First, the single-mode condition for an SOI ridge nanowire with different Si core thicknesses is obtained. The obtained single-mode condition is different from that for the conventional micrometrical SOI ridge waveguides with a large cross section. By adjusting the cross section (the core width and the etching depth), one can have a nonbirefringent SOI ridge nanowire. The analysis on the bending loss of S01 ridge nanowires shows that one can have a relatively small bending radius even with a shallow etching (i.e., a small ratio γ between the etching depth and the total thickness). For example, even when one chooses a small ratio γ= 0.4, one still has a low bending loss with a small bending radius of 15 μm for an SOI nanowire with a thin core h∞= 250 nm, which is very different from a conventional large SOI ridge waveguide.
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| 28. |
- Dalarsson, Mariana, et al.
(författare)
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Wave propagation in waveguides with graded plasmonic obstacles
- 2021
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : OPTICAL SOC AMER. - 0740-3224 .- 1520-8540. ; 38:1, s. 104-113
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, wave propagation in a hollow waveguide with a graded dielectric layer is studied. Analytic formulas are derived for the electric field components as well as general analytical results for the reflection and transmission coefficients for propagating waves. These results are all valid for waveguides of arbitrary cross sections, and the derived reflection and transmission coefficients are in exact asymptotic agreement with those obtained for a wry thin homogeneous dielectric layer using cascading and mode-matching techniques. Furthermore, the power transmission, reflection, and absorption coefficients, as functions of frequency and layer width, are studied, showing the expected behavior of these parameters. The method proposed in this paper gives directly applicable results that do not require cascading and mode matching, while at the same time having the ability to model smooth transitions that are more realistic in several applications. (C) 2020 Optical Society of America
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| 29. |
- Dyke, T.R., et al.
(författare)
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Experimental demonstration of data erasure for time-domain optical memories
- 1999
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 16:5, s. 805-811
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Tidskriftsartikel (refereegranskat)abstract
- Data erasure is considered an essential requirement for a practical optical time-domain memory, and it requires that the laser used have very good frequency stability. Such a laser is developed for this work, and data erasure is demonstrated with a sample of YSiO5:Eu3+ for write/rewrite pulse sequences of up to a duration of 100 μs. This is two orders of magnitude longer than had been achieved previously. Phase-sensitive detection is introduced and is shown to be invaluable for monitoring the write, rewrite, and read processes.
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| 30. |
- Edner, H, et al.
(författare)
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Differential Optical-absorption Spectroscopy (doas) System For Urban Atmospheric-pollution Monitoring
- 1993
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 32:3, s. 327-333
-
Tidskriftsartikel (refereegranskat)abstract
- We describe a fully computer-controlled differential optical absorption spectroscopy system for atmospheric air pollution monitoring. A receiving optical telescope can sequentially tune in to light beams from a number of distant high-pressure Xe lamp light sources to cover the area of a medium-sized city. A beam-finding servosystem and automatic gain control permit unattended long-time monitoring. Using an astronomical code, we can also search and track celestial sources. Selected wavelength regions are rapidly and repetitively swept by a monochromator to sensitively record the atmospheric absorption spectrum while avoiding the detrimental effects of atmospheric turbulence. By computer fitting to stored laboratory spectra, we can evaluate the path-averaged concentration of a number of important pollutants such as NO2, SO2, and O3. A measurement of NH3 and NO close to the UV limit is also demonstrated.
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| 31. |
- Edner, H, et al.
(författare)
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Fluorescence Lidar Multicolor Imaging of Vegetation
- 1994
-
Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 33:13, s. 2471-2479
-
Tidskriftsartikel (refereegranskat)abstract
- Multicolor imaging of vegetation fluorescence following laser excitation is reported for distances of 50 m. A mobile laser-radar system equipped with a Nd:YAG laser transmitter and a 40-cm-diameter telescope was utilized. The laser light was Raman shifted to 397 nm with pulse energies of approximately 30 mJ. An image-intensified CCD camera with a specially designed split-mirror Cassegrainian telescope was utilized for the simultaneous recording of fluorescence images of leaves and branches in four different spectral bands. Additionally, fluorescence spectra at selected points within the detection area were measured with an image-intensified diode array system. Image processing permits extraction of information related to the physiological status of the vegetation and might prove useful in forest decline research.
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| 32. |
- Ehlers, Patrick, 1981-, et al.
(författare)
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Doppler broadened NICE-OHMS beyond the triplet formalism : assessment of optimum modulation index
- 2014
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 31:7, s. 1499-1507
-
Tidskriftsartikel (refereegranskat)abstract
- The dependence of Doppler broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) on the modulation index, beta, has been investigated experimentally on C2H2 and CO2, both in the absence and the presence of optical saturation. It is shown that the maximum signals are obtained for beta that produce more than one pair of sidebands: in the Doppler limit and for the prevailing conditions (unsaturated transition and the pertinent modulation frequency and Doppler widths) around 1 and 1.4 for the dispersion and absorption detection phases, respectively. The results verify predictions given in an accompanying work. It is also shown that there is no substantial broadening of the NICE-OHMS signal for beta < 1. The use of beta of unity has yielded a Db-NICE-OHMS detection sensitivity of 4.9 x 10(-12) cm(-1) Hz(-1/2), which is the lowest (best) value so far achieved for NICE-OHMS based on a tunable laser. The number of sidebands that needs to be included in fits of the line-shape function to obtain good accuracy has been assessed. It is concluded that it is enough to consider three pairs of sidebands whenever the systematic errors in a concentration assessment should be below 1% when beta < 2 are used and <1 parts per thousand for beta < 1.5.
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| 33. |
- Ehlers, Patrick, 1981-, et al.
(författare)
-
Doppler broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry : optimum modulation and demodulation conditions, cavity length, and modulation order
- 2014
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : The Optical Society of America. - 0740-3224 .- 1520-8540. ; 31:9, s. 2051-2060
-
Tidskriftsartikel (refereegranskat)abstract
- Doppler broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry (Db-NICE-OHMS) has been scrutinized with respect to modulation and demodulation conditions (encompassing the modulation frequency,nu(m), the modulation index, beta, and the detection phase, theta), the cavity length, L, and the modulation order, k (defined as nu(m)/nu(FSR), where nu(FSR) is the free-spectral range of the cavity), primarily in the Doppler limit but also for two specific situations in the Voigt regime (for equal Doppler and homogeneous width and for purely Lorentzian broadened transitions), both in the absence and presence of optical saturation (the latter for the case in which the homogeneous broadening is smaller than the modulation frequency). It is found that, for a system with a given cavity length, the optimum conditions (i.e., those that produce the largest NICE-OHMS signal) for an unsaturated transition in the Doppler limit comprise nu(m)/Gamma(D) = 1.6 (where Gamma(D) is the half-width at half-maximum of the Doppler width of the transition), beta = 1.3, and theta = 0.78 pi. It is also found that the maximum is rather broad; the signal takes 95% of its maximum value for modulation frequencies in the entire 0.4 less than or similar to nu(m)/Gamma(D) less than or similar to 2.4 range. When optical saturation sets in, theta shifts toward the dispersion phase. The optimum conditions encompass k > 1 whenever L > 0.35L(D) and 2.6L(D) for the dispersion and absorption modes of detection, respectively [where L-D is a characteristic length given by c/(2 Gamma(D))]. Similar conditions are found under pressure broadened conditions.
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| 34. |
- Ehlers, Patrick, 1981-, et al.
(författare)
-
Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrumentation for Doppler-broadened detection in the 10-12 cm-1 Hz-1/2 region
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:6, s. 1305-1315
-
Tidskriftsartikel (refereegranskat)abstract
- A fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry (FL-NICE-OHMS) system for white-noise-limited Doppler-broadened detection down to 5.6 x 10(-12) cm(-1) Hz(-1/2) is demonstrated. The system is based on a previous FL-NICE-OHMS instrumentation in which the locking of the laser frequency to a cavity mode has been improved by the use of an acousto-optic modulator (AOM) and provision of a more stable environment by the employment of a noise-isolating enclosed double-layer table, a temperature regulation of the laboratory, and an ultra-high-vacuum (UHV) gas system. White-noise behavior up to 10 s provides the instrument with a minimum detectable on-resonance absorbance per unit length of 1.8 x 10(-12) cm(-1) and a relative single-pass absorption (Delta I/I) of 7.2 x 10(-11). The system was applied to detection of acetylene on a transition at 1531.588 nm, yielding a detection sensitivity of C2H2 in atmospheric pressure gas of 4 ppt (measured over 10 s). (C) 2012 Optical Society of America
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| 35. |
- Ehlers, Patrick, 1981-, et al.
(författare)
-
Use of etalon-immune distances to reduce the influence of background signals in frequency-modulation spectroscopy and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy
- 2014
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 31:12, s. 2938-2945
-
Tidskriftsartikel (refereegranskat)abstract
- The detection sensitivity of phase-modulated techniques such as frequency-modulation spectroscopy (FMS) and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is often limited by etalon background signals. It has previously been shown that the impact of etalons can be reduced by the use of etalon-immune distances (EIDs), i.e., by separating the surfaces that give rise to etalons by a distance of q. L-m, where L-m is given by c/2n nu(m), where, in turn, n and nu(m) are the index of refraction between the components that make up the etalon (thus most often that of air) and the modulation frequency, respectively, and where q is an integer (i.e., 1, 2, 3,.) or half-integer (i.e., 1/2, 1, 3/2,.) for the dispersion and absorption modes of detection, respectively. An etalon created by surfaces separated by an EID will evade detection and thereby not contribute to any background signal. The concept of EIDs in FMS and NICE-OHMS is in this work demonstrated, scrutinized, and discussed in some detail. It is shown that the influence of EIDs on the absorption and dispersion modes of detection is significantly different; signals detected at the dispersion phase are considerably less sensitive to deviations from exact EID conditions than those detected at the absorption phase. For example, the FM background signal from an etalon whose length deviates from an EID by 2.5% of L-m (e.g., by 1 cm for an L-m of 40 cm), detected in dispersion, is only 9% of that in absorption. This makes the former mode of detection the preferred one whenever a sturdy immunity against etalons is needed or when optical components with parallel surfaces (e.g., lenses, polarizers, or beam splitters) are used. The impact of the concept of EIDs on NICE-OHMS is demonstrated by the use of Allan-Werle plots.
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| 36. |
- El-Kallassi, Pascale, et al.
(författare)
-
Optical tuning of planar photonic crystals infiltrated with organic molecules
- 2007
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 24:9, s. 2165-2171
-
Tidskriftsartikel (refereegranskat)abstract
- The optical tuning of InP-based planar photonic crystals (PhCs) infiltrated with a photoresponsive liquid crystal system is presented. Photoinduced phase transitions of a liquid crystal blend doped with azobenzene molecules are used to tune the optical response of PhC cavities. This process is found to be reversible and stable. Several tuning conditions are analyzed in terms of the blend phase diagram.
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| 37. |
- Elman, U., et al.
(författare)
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Influence of laser phase and frequency fluctuations on photon-echo data erasure
- 1996
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Ingår i: Optical Society of America. Journal B: Optical Physics. - 0740-3224. ; 13:9, s. 1905-1915
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Tidskriftsartikel (refereegranskat)abstract
- Erasure of data stored by use of photon echoes has been investigated as a function of data writing time and data storage time. The results clarify the requirements on laser phase and frequency stability for performing photon-echo data erasure. The analysis of phase and frequency stability of a light source by the photon-echo erasure process is illustrated. A theoretical analysis emphasizing the physical processes that affect the erasure efficiency as well as an extensive discussion of possible error sources are given. Finally, an approach to bit-selective photon-echo data erasure that is insensitive to laser phase and frequency fluctuations is suggested.
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| 38. |
- Escoto, Esmerando, et al.
(författare)
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Temporal quality of post-compressed pulses at large compression factors
- 2022
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 39:7, s. 1694-1702
-
Tidskriftsartikel (refereegranskat)abstract
- Post-compression of ultra-short laser pulses via self-phase modulation is routinely employed for the generation of laser pulses with optical bandwidths reaching far beyond the laser gain limitations. Although high compression factors can be routinely achieved, the compressed pulses typically suffer from temporal quality degradation. We numerically and experimentally analyze the deterioration of different measures of temporal quality with increasing compression factor and show how appropriate dispersion management and cascading of the post-compression process can be employed to limit the impact of this effect. The demonstrated saturation of pulse quality degradation at large compression factors puts novel femtosecond laser architectures based on post-compressed picosecond or even nanosecond laser systems in sight.
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| 39. |
- Faldon, M. E, et al.
(författare)
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Studies of time-resolved harmonic generation in intense laser fields in xenon
- 1992
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 0740-3224. ; 9:11, s. 2094-2099
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Tidskriftsartikel (refereegranskat)abstract
- We report preliminary experimental and computational studies of the temporal evolution of the harmonics, generated in xenon, by 50-ps pulses from a Nd: YLF laser, amplified in Nd: glass amplifiers, and focused to produce intensities in the range 1013--5 {\texttimes} 1013 W cm{\textminus}2. Measurements were made of the temporal profiles of the seventh- and ninth-order harmonics using a specially modified VUV streak camera with better than 7-ps temporal resolution. These results were compared with predictions of a numerical model that included the effects of neutral atom depletion and photoelectron dispersion in the calculation of the harmonic output as a function of time.
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| 40. |
- Fallah, Hoorieh, et al.
(författare)
-
Excitation of core modes through side coupling to multimode optical fiber by hydrothermal growth of ZnO nanorods for wide angle optical reception
- 2014
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 31:9, s. 2232-2238
-
Tidskriftsartikel (refereegranskat)abstract
- Side coupling to core modes through zinc oxide (ZnO) nanorods grown around the fiber is demonstrated in this work. The scheme utilizes wet etching of the cladding region followed by hydrothermal growth of the nanorods. The combination of nanostructures and the optical fiber system is used to demonstrate a simple wide field of view (FOV) optical receiver. Core modes are excited by the light scattered in the region where the fiber core is exposed. The angular response of the receiver was tested using a nephlometer. Light coupling efficiency was extracted by deconvoluting the finite beam extinction from the measured power. The results were compared to a first-order analytical model in which the phase function is assumed to linearly shift with the incident angle. The trend of the experimental measurements agrees with the model. 180 degrees FOV is verified, and maximum coupling efficiency of around 2.5% for a single fiber is reported. Excitation of core modes through side coupling shows potential for the application of these devices in optical receivers and sensors.
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| 41. |
- Ferrini, R., et al.
(författare)
-
Radiation losses in planar photonic crystals : two-dimensional representation of hole depth and shape by an imaginary dielectric constant
- 2003
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 20:3, s. 469-478
-
Tidskriftsartikel (refereegranskat)abstract
- Waveguide modes in two-dimensional (2-D) photonic crystals (PhCs) deeply etched through monomode slab waveguides, e.g., AlGaAs/GaAs, GaAs/AlOx, or InP/GaInAsP, suffer from radiation losses that are strongly affected by the air hole depth and shape. The issue of three-dimensional (3-D) out-of-plane losses is addressed analytically by means of an incoherent approximation. Assuming separability both for the dielectric map and for the electric field, this approach is valid for defects such as in-plane microcavities, PhC-based waveguides, bends and couplers. Out-of-plane scattering is translated into an effective imaginary index in the air holes, so that 3-D losses can be cast in a simple 2-D calculation. The case of cylindroconical holes is treated, and the validity of this approach is experimentally confirmed by transmission measurements through simple PhC slabs.
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| 42. |
- Fokine, Michael
(författare)
-
Formation of thermally stable chemical composition gratings in optical fibers
- 2002
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 19:8, s. 1759-1765
-
Tidskriftsartikel (refereegranskat)abstract
- Experimental results and a discussion of possible chemical pathways in the formation of thermally stable chemical composition gratings in optical fibers are presented. Gratings are formed through high-temperature treatment of UV-exposed hydrogen-loaded fibers. The final refractive-index modulation is ascribed to variations in fluorine concentration attained by periodically increased diffusion of fluorine. The mechanism behind this increase is the formation of mobile hydrogen fluoride from chemical reactions of fluorine and UV-induced hydroxyl, which occur with the spatial periodicity of the UV pattern. A hydroxyl-assisted increase in fluorine diffusion has been verified by time-of-flight secondary-ion mass spectroscopy. Formation of ultrastable grating by periodic variation of oxygen concentration through diffusion of molecular water is also discussed.
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| 43. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
-
Doppler-broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry signals from optically saturated transitions under low pressure conditions
- 2008
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 25:7, s. 1156-1165
-
Tidskriftsartikel (refereegranskat)abstract
- The influence of optical saturation on noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) signals from purely Doppler-broadened transitions is investigated experimentally. It is shown that the shape and the strength of the dispersion signal are virtually unaffected by optical saturation, whereas the strength of the absorption signal decreases as (1+G+-1)-1/2, where G+-1 is the degree of saturation induced by the sideband of the frequency modulated triplet, in agreement with theoretical predictions. This implies, first of all, that Doppler-broadened NICE-OHMS is affected less by optical saturation than other cavity enhanced techniques but also that it exhibits nonlinearities in the power and pressure dependence for all detection phases except pure dispersion. A methodology for assessments of the degree of saturation and the saturation power of a transition from Doppler-broadened NICE-OHMS signals is given. The implications of optical saturation for practical trace species detection by Doppler-broadened NICE-OHMS are discussed.
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| 44. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
-
Wavelength modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy signal line shapes in the Doppler limit
- 2009
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 26:7, s. 1384-1394
-
Tidskriftsartikel (refereegranskat)abstract
- A thorough analysis of the shape and strength of Doppler-broadened wavelength modulated noise-immune cavity-enhanced optical heterodyne molecular spectroscopy signals is presented and their dependence on modulation frequency, modulation amplitude and detection phase is investigated in detail. The conditions that maximize the on-resonance signal are identified. The analysis is based on the standard frequency modulation spectroscopy formalism and the Fourier description of wavelength modulation spectroscopy and verified by fits to experimental signals from C2H2 and CO2 measured at 1531 nm. In addition, the line strengths of two CO2 transitions in the v2→3v1+v2+v3 hot band [Pe(7) and Pe(9)] were found to differ by ~20% from those given in the HITRAN database.
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| 45. |
- Foltynowicz-Matyba, Aleksandra, 1981-, et al.
(författare)
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Reduction of background signals in fiber-based NICE-OHMS
- 2011
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - Washington, D.C. : Optical Society of America. - 0740-3224 .- 1520-8540. ; 28:11, s. 2797-2805
-
Tidskriftsartikel (refereegranskat)abstract
- Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) based on a fiber-coupled electro-optic modulator (EOM) provides a compact and versatile experimental setup. It has, however, been limited by background signals originating from an imbalance of the phase modulated triplet created by a cross-coupling between the principal axes of the polarization maintaining fibers and the extraordinary axis of the EOM. Two strategies for reducing these background signals are investigated: (i) using an EOM with a titanium diffused waveguide, in which the balance of the triplet is controlled by active feedback, and (ii) using an EOM with a proton exchanged waveguide that does not support light propagation along the ordinary axis. It is shown that both approaches significantly reduce drifts and noise in the system. Using a cavity with a finesse of 5700, an absorption sensitivity of 3: 2 x 10(-12) cm(-1) in 1 min of integration time (i.e., 1: 8 x 10(-11) cm(-1) Hz(-1/2)) is demonstrated for Doppler-broadened detection, the lowest reported so far for Doppler-broadened NICE-OHMS. For sub-Doppler detection, a minimum detectable optical phase shift of 1: 3 x 10(-12) cm(-1) in 400s of integration time is obtained. (C) 2011 Optical Society of America
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| 46. |
- Fu, Ying, et al.
(författare)
-
Optical transmission and waveguiding by excitonic quantum dot lattices
- 2006
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 23:11, s. 2441-2447
-
Tidskriftsartikel (refereegranskat)abstract
- Metal-dielectric-metal configurations of optical waveguides have a very high laterally packaging density at the cost of high optical loss. Photonic crystals based on refractive-index-modulation materials have been used in optics, e.g., two materials having different refractive indices form a well-defined Bragg refraction mirror. Such a waveguide has lower loss but also lower packaging density. From the outset of these two notions, we propose a photonic-crystal device based on the exciton-polariton effect in a three-dimensional array of semiconductor quantum dots (QDs) for ultradense optical planar circuit applications. Excitons are first photogenerated in the QDs by the incident electromagnetic field, the exciton-polariton effect in the QD photonic crystal then induces an extra optical dispersion in QDs. The high contrast ratio between the optical dispersions of the QDs and the background therefore creates clear photonic bandgaps. By carefully designing the QD size and the QD lattice structure, perfect electromagnetic field reflection can be obtained at a specific wavelength in the lossless case, thus providing the fundamental basis for ultradense optical waveguide applications.
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| 47. |
- Gao, Shiming, et al.
(författare)
-
Two channels of entangled twin photons generated by quasi-phase-matched spontaneous parametric down-conversion in periodically poled lithium niobate crystals
- 2008
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 25:5, s. 734-740
-
Tidskriftsartikel (refereegranskat)abstract
- We propose the generation of two-channel time-energy entangled twin photons based on two simultaneous first-order quasi-phase-matched (QPM) spontaneous parametric down-conversion processes in a periodically poled lithium niobate (PPLN) with a monochromatic pump. The theoretical model for the generation of the entangled photons is established, and the analytical solution is obtained in a lossless crystal with an undepleted pump assumption. The generated condition of entangled photons is achieved in terms of the QPM grating period and the pump wavelength. It is shown that two channels of entangled twin photons with different wavelengths can be created by suitably choosing the PPLN grating period once the pump wavelength is fixed, which provides the potential to introduce the wavelength division multiplexed technique into quantum information systems.
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| 48. |
- Garnier, J., et al.
(författare)
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Toward a wave turbulence formulation of statistical nonlinear optics
- 2012
-
Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 29:8, s. 2229-2242
-
Tidskriftsartikel (refereegranskat)abstract
- During this last decade, several remarkable phenomena inherent to the nonlinear propagation of incoherent optical waves have been reported in the literature. This article is aimed at providing a generalized wave turbulence kinetic formulation of random nonlinear waves governed by the nonlinear Schrodinger equation in the presence of a nonlocal or a noninstantaneous nonlinear response function. Depending on the amount of nonlocal (noninstantaneous) nonlinear interaction and the amount of inhomogeneous (nonstationary) statistics of the incoherent wave, different types of kinetic equations are obtained. In the spatial domain, when the incoherent wave exhibits fluctuations that are statistically homogeneous in space, the relevant kinetic equation is the wave turbulence (Hasselmann) kinetic equation. It describes, in particular, the process of optical wave thermalization to thermodynamic equilibrium, which slows down significantly as the interaction becomes highly nonlocal. When the incoherent wave is characterized by inhomogeneous statistical fluctuations, different forms of the Vlasov equation are derived, which depend on the amount of nonlocality in the system. This Vlasov approach describes, in particular, the processes of incoherent modulational instability and the formation of localized incoherent soliton structures. In the temporal domain, the noninstantaneous nonlinear response function is constrained by the causality condition. It turns out that the relevant kinetic equation has a form analogous to the weak Langmuir turbulence equation, which describes, in particular, the formation of nonlocalized spectral incoherent solitons. In the regime of a highly noninstantaneous nonlinear response and a stationary statistics of the incoherent wave, the weak Langmuir turbulence equation reduces to the Korteweg-de Vries equation. Conversely, in the regime of a highly noninstantaneous response in the presence of a nonstationary statistics, we derive a long-range Vlasov-like kinetic equation in the temporal domain, whose self-consistent potential is constrained by the causality condition. From a broader perspective, this work indicates that the wave turbulence theory may constitute the appropriate theoretical framework to formulate statistical nonlinear optics.
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| 49. |
- Gel'mukhanov, Faris, et al.
(författare)
-
Dynamics of two-photon absorption by molecules and solutions
- 2002
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 19:5, s. 937-945
-
Tidskriftsartikel (refereegranskat)abstract
- A dynamic density-matrix based theory of two-photon absorption (TPA) of molecules and solutions is presented. The theory highlights the influence of pulse duration, dephasing, and resonant conditions on the final TPA cross section as well as that of saturation, including a hierarchy of saturation intensities. A breakdown of the conventional identification of TPA with coherent one-step TPA is predicted for the long-pulse regime in which incoherent two-step TPA can even dominate the coherent one-step TPA process. The major role of the solvent is to enhance the off-resonant contributions to TPA furnished by collisional dephasing.
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| 50. |
- Genty, Goery, et al.
(författare)
-
Complete characterization of supercontinuum coherence
- 2011
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 28:9, s. 2301-2309
-
Tidskriftsartikel (refereegranskat)abstract
- Using second-order coherence theory of nonstationary light we examine in detail the coherence properties of supercontinuum radiation generated in nonlinear fibers. We show that the supercontinuum can be divided into quasi-coherent and quasi-stationary parts and that the relative contributions depend on the dynamics involved in the spectral broadening process. We establish the correspondence between the quasi-coherent part of the two-frequency correlation function of the second-order theory and the usual Dudley-Coen degree of coherence used to characterize the shot-to-shot stability of supercontinuum sources. Experimental implementation for measuring separately the quasi-coherent and quasi-stationary contributions is further addressed. Our results open the route for complete characterization of supercontinuum coherence.
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