SwePub - sökning: L773:0740 3224 OR L773:1520 85...

Numrering	Referens	Omslagsbild	Hitta
1.	Adolfsson, Göran, 1981, et al. (författare) Spectral engineering of semiconductor Fabry–Perot laser cavities in the weakly and strongly perturbed regimes 2010 Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 27:1, s. 118-127 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.
2.	Akram, Nadeem, 1971-, et al. (författare) Experimental characterization of high-speed 1.55 mu m buried heterostructure InGaAsP/InGaAlAs quantum-well lasers 2009 Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 26:2, s. 318-327 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.
3.	Ali, Mona, et al. (författare) 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 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.
4.	Andersson, Dan, 1966, et al. (författare) 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.
5.	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.
6.	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
7.	Axner, Ove, et al. (författare) 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
8.	Baev, A., et al. (författare) 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)].
9.	Baev, Alexander, et al. (författare) 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.
10.	Basieva, Irina (författare) 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
11.	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.
12.	Björk, Gunnar, et al. (författare) 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.
13.	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 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.
14.	Cai, Yangjian, et al. (författare) 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 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.
15.	Castello-Lurbe, David, et al. (författare) 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.
16.	Cattani, F., et al. (författare) 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 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.
17.	Cui, Yanxia, et al. (författare) 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 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.
18.	Cui, Y. X., et al. (författare) 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.
19.	Dai, Daoxin, et al. (författare) 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
20.	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.
21.	Dalarsson, Mariana, et al. (författare) 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
22.	Ehlers, Patrick, 1981-, et al. (författare) 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.
23.	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.
24.	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
25.	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.
26.	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.
27.	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.
28.	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.
29.	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.
30.	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.
31.	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.
32.	Foltynowicz-Matyba, Aleksandra, 1981-, et al. (författare) 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
33.	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.
34.	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.
35.	Garnier, J., et al. (författare) 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.
36.	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.
37.	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.
38.	Guo, Shuwei, et al. (författare) Optical surface transformation for reshaping the field intensity distribution 2016 Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 33:9, s. 1847-1851 Tidskriftsartikel (refereegranskat)abstract In this study, we focus on how to reshape the field intensity distribution on the wavefront of an incident beam and produce special optical beams (e.g., asymmetric Gaussian beams, hollow beams, and zeroth-order Bessel beams) using optical surface transformation (OST). The key design method of this paper is based on OST, which is the extension of transformation optics. Numerical simulations are given to verify the performance of the proposed devices.
39.	Hall, Björn, 1973, et al. (författare) Pump-probe collision in optical fibers : Four-wave-mixing induced frequency jump 2001 Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America (OSA). - 0740-3224 .- 1520-8540. ; 18:11, s. 1652-1658 Tidskriftsartikel (refereegranskat)abstract An investigation is made of ultrafast pump-probe pulse collisions near the zero-dispersion wavelength in an optical single-mode fiber. A steplike probe frequency shift is observed when the pump power is gradually increased. The magnitude of this frequency jump is shown to depend on the phase difference between the pulses. This new effect is investigated numerically and experimentally and is attributed to four-wave mixing.
40.	Hansson, Tobias, 1983, et al. (författare) Frequency comb generation beyond the Lugiato-Lefever equation: multi-stability and super cavity solitons 2015 Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 32:7, s. 1259-1266 Tidskriftsartikel (refereegranskat)abstract The generation of optical frequency combs in microresonators is considered without resorting to the mean-field approximation. New dynamical regimes are found to appear for high intracavity power that cannot be modeled using the Lugiato-Lefever equation. Using the Ikeda map, we show the existence of multi-valued stationary states and analyze their stability. Period doubled patterns are considered, and a novel type of super cavity soliton associated with the multi-stable states is predicted.
41.	Hansson, Tobias, et al. (författare) Scalar Wigner theory for polarized light in nonlinear Kerr media 2013 Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:6, s. 1765-1769 Tidskriftsartikel (refereegranskat)abstract A scalar Wigner distribution function for describing polarized light is proposed in analogy with the treatment of spin variables in quantum kinetic theory. The formalism is applied to the propagation of circularly polarized light in nonlinear Kerr media, and an extended phase-space evolution equation is derived along with invariant quantities. The formalism is additionally used to analyze the modulational instability. (C) 2013 Optical Society of America
42.	Hansson, T., et al. (författare) Scalar Wigner theory for polarized light in nonlinear Kerr media 2013 Ingår i: Journal of the Optical Society of America B: Optical Physics. - : The Optical Society. - 1520-8540 .- 0740-3224. ; 30:6, s. 1765-1769 Tidskriftsartikel (refereegranskat)abstract A scalar Wigner distribution function for describing polarized light is proposed in analogy with the treatment of spin variables in quantum kinetic theory. The formalism is applied to the propagation of circularly polarized light in nonlinear Kerr media, and an extended phase-space evolution equation is derived along with invariant quantities. The formalism is additionally used to analyze the modulational instability
43.	Hansson, Tobias, 1983, et al. (författare) Single envelope equation modeling of multi-octave comb arrays in microresonators with quadratic and cubic nonlinearities 2016 Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 33:6, s. 1207-1215 Tidskriftsartikel (refereegranskat)abstract We numerically study, by means of the single envelope equation, the generation of optical frequency combs ranging from the visible to the mid-infrared spectral regions in resonators with quadratic and cubic nonlinearities. Phase-matched quadratic wave-mixing processes among the comb lines can be activated by low-power continuous wave pumping in the near infrared of a radially poled lithium niobate whispering gallery resonator. We examine both separate and coexisting intracavity doubly resonant second-harmonic generation and parametric oscillation processes and find that modulation instabilities may lead to the formation of coupled comb arrays extending over multiple octaves. In the temporal domain, the frequency combs may correspond to pulse trains or even to a single pulse circulating in the cavity.
44.	Harvey, Clarissa M., 1988-, et al. (författare) Specialty optical fiber fabrication : fiber draw tower based on a CO laser furnace 2021 Ingår i: Journal of the Optical Society of America. B, Optical physics. - : The Optical Society. - 0740-3224 .- 1520-8540. ; 38:12, s. F122-F129 Tidskriftsartikel (refereegranskat)abstract An experimental, laboratory-scale optical fiber drawing tower based on CO laser heating has been developed and used to fabricate speciality optical fiber. The CO laser was utilized in a symmetric four beam heating system. The localized and responsive heating time of the laser-based furnace was beneficial for manufacturing crystalline core fibers, specifically, silicon core optical fibers. Moreover, the specific absorption properties of the CO laser radiation in silica have been evaluated with the aid of finite element modeling. In comparison to the more traditional CO2 laser, CO lasers were found to improve temperature uniformity and heating times while minimizing surface evaporation.
45.	Hawkins, T. W., et al. (författare) Kilowatt power scaling of an intrinsically low Brillouin and thermo-optic Yb-doped silica fiber 2021 Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 38:12, s. F38-F49 Tidskriftsartikel (refereegranskat)abstract The performance of optical fibers is dependent on both the fiber design and the materials from which it is made. While much of the development over the past few decades has focused on fiber geometry and microstructuring, more recent analyses have shown clear benefits of addressing parasitic nonlinearities at the origins of their light–matter interactions. Reported here are results on intrinsically low Brillouin and thermo-optic core fibers, fabricated using modified chemical vapor deposition. Specifically, fibers in the Yb-doped Al2O3−P2O5−B2O3−SiO2 system are developed based on how each glass constituent affects the material parameters that enable both stimulated Brillouin scattering (SBS) and transverse mode instability (TMI). One fiber, developed to be very heavily doped, exhibited thermo-optic and Brillouin gain coefficients up to ∼3 dB and 6 dB below conventional laser fibers, respectively. A second fiber, designed to approximate a commercial double-clad laser fiber, which necessitated lower doping levels, was output power scaled to over 1 kW with an efficiency over 70% and no observed photodarkening under conventional testing. Design curves for the enabling material properties that drive TMI and SBS also are provided as functions of compositions as a tool for the community to further study and develop intrinsically low-nonlinearity fiber lasers.
46.	Helgason, Òskar Bjarki, 1989, et al. (författare) Superchannel engineering of microcombs for optical communications 2019 Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 36:8, s. 2013-2022 Tidskriftsartikel (refereegranskat)abstract Microresonator frequency combs (microcombs) are a promising technology for generating frequency carriers for wavelength division multiplexing (WDM) systems. Multi-terabit per second WDM coherent transmitters have recently been demonstrated using both dissipative Kerr solitons and mode-locked dark pulses in optical microresonators. These experiments have focused on microcombs designed to cover a large portion of the erbium-doped fiber window. However, the question of optimum bandwidth for microcombs in WDM systems has not been addressed. Here we show that segmenting the bandwidth into smaller microcomb-driven superchannels results in an improvement of power per line. Through numerical simulations we establish a quantitative comparison between dark-pulse and soliton microcombs in WDM systems, including aspects such as conversion efficiency, tolerance to intrinsic cavity loss, and group velocity dispersion engineering. We show that the improvement of minimum line power scales linearly with the number of superchannels for both types of microcombs. This work provides useful guidelines for the design of multi-terabit per second microcomb-based superchannel systems.
47.	Holmberg, Patrik, 1971-, et al. (författare) Thermometric study of CO2-laser heated optical fibers in excess of 1700 degrees C using fiber Bragg gratings 2013 Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:7, s. 1835-1842 Tidskriftsartikel (refereegranskat)abstract The thermal response of optical fibers during CO2 laser irradiation has been characterized by using thermally stable short-period fiber Bragg gratings, referred to as chemical composition gratings. CO2 laser beam profiling was performed by scanning the beam across a 1 mm long grating, providing a spatial resolution given by the fiber diameter. The thermal dynamics during square pulse irradiation has been recorded for temperatures in excess of 1700°C, with heating and cooling rates as high as 10,500°C s−1 and 6500°C s−1, respectively.
48.	Jelger, Pär, et al. (författare) Degradation free operation of 980 nm laser in Yb/Ce7Al-doped silica fiber 2010 Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 27:338 Tidskriftsartikel (refereegranskat)
49.	Jelger, Pär, et al. (författare) Degradation-resistant lasing at 980 nm in a Yb/Ce/Al-doped silica fiber 2010 Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 27:2, s. 338-342 Tidskriftsartikel (refereegranskat)abstract In this work we measure how photodarkening affects the optical efficiency for three different Yb/Al-doped silica fibers operating at 980 nm, one of which is codoped with cerium. A volume Bragg grating is used for linewidth control and added rejection of amplified spontaneous emission. Several hours of degradation-resistant operation is obtained with the Ce-codoped fiber, while for the Yb/Al doped fibers a large drop in efficiency is observed within the first hour of operation. Our results show that Yb/Ce/Al-doped fibers could be excellent candidates for high-power 980 nm fiber laser sources.
50.	Jeong, H., et al. (författare) Evolution of Sommerfeld and Brillouin precursors in intermediate spectral regimes 2009 Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 26:12, s. 2455-2460 Tidskriftsartikel (refereegranskat)abstract We study, numerically, the transitional behavior of precursors in the intermediate spectral regime between twocontrasting regimes for which analytical solutions exist. The two opposite regimes are, respectively, defined as(1) off-resonance carrier with a spectral pulse width comparable to the medium’s absorption linewidth and (2)on-resonance carrier with the spectral width of the pulse much narrower than the absorption linewidth. Beyondthese two regimes, there have been few studies of precursors. In this paper, we investigate precursordynamics for the intermediate spectral regime using the finite-difference time domain method. The parameterthat has the strongest influence on the precursor dynamics is found to be the plasma frequency, ωp. This researchis applicable for controlling transients in fast communication systems.

Skapa referenser, mejla, bekava och länka

Länka till träfflistan

Träfflista för sökning "L773:0740 3224 OR L773:1520 8540 "

Avgränsa träffmängd

År