| 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. |
- Augulis, Ramunas, et al.
(författare)
-
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
-
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
|
|
| 3. |
- 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
|
|
| 4. |
- 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.
|
|
| 5. |
- Chen, Shihua, et al.
(författare)
-
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
-
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
|
|
| 6. |
- 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.
|
|
| 7. |
- 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.
|
|
| 8. |
- 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.
|
|
| 9. |
- 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
|
|
| 10. |
- 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.
|
|
| 11. |
- 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.
|
|
| 12. |
- 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
|
|
| 13. |
- 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.
|
|
| 14. |
- 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.
|
|
| 15. |
- 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
|
|
| 16. |
- 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
|
|
| 17. |
- 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.
|
|
| 18. |
|
|
| 19. |
- 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.
|
|
| 20. |
- Jiao, Yuqing, et al.
(författare)
-
Accurate and efficient simulation for silicon-nanowire-based multimode interference couplers with a 3D finite-element mode-propagation analysis
- 2010
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of American (OSA). - 0740-3224 .- 1520-8540. ; 27:9, s. 1813-1818
-
Tidskriftsartikel (refereegranskat)abstract
- A three-dimensional (3D) finite-element mode-propagation analysis is presented to give an accurate and efficient simulation for silicon-nanowire- based multimode interference (MMI) couplers. For the presented numerical method, a finite-element method mode solver is used to calculate the mode profiles and the propagation constants in a multimode section. The comparison between the presented method and some other numerical methods [e.g., finite-difference time-domain (FDTD) method, beam propagation methods, etc.] is also shown. It is shown that the presented numerical method gives simulation results very close to those from the 3D FDTD (with a deviation less than 1%). Therefore, it is very convenient for the design of Si-nanowire-based MMI couplers.
|
|
| 21. |
- Kabakova, Irina V., et al.
(författare)
-
Switching and dynamic wavelength conversion in a fiber grating cavity
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 29:1, s. 155-160
-
Tidskriftsartikel (refereegranskat)abstract
- Switching and dynamic wavelength conversion of light are demonstrated in a fiber grating cavity detuned by high-voltage electrical pulses. The cavity dynamics is studied using a heterodyne technique in which the frequency-shifted light, trapped by the cavity, mixes with the backreflected light at the incident frequency. We find that the frequency shift scales linearly with the energy of the electric driving pulses.
|
|
| 22. |
- Kolliopoulos, G., et al.
(författare)
-
Single-shot autocorrelator for extreme-ultraviolet radiation
- 2014
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 31:5, s. 926-938
-
Tidskriftsartikel (refereegranskat)abstract
- A novel single-shot second-order autocorrelation scheme for extreme-ultraviolet radiation (XUV) is proposed. It is based on an ion-imaging technique, which provides spatial information of ionization products in the focal volume of the XUV beam. Using simple analytical and detailed numerical modeling, an evaluation toward selecting an optimum configuration has been performed. The implementation of the concept to characterize attosecond pulses is discussed, and the proposed setups are assessed.
|
|
| 23. |
- Korhonen, Minna, et al.
(författare)
-
Elementary field representation of supercontinuum
- 2013
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:1, s. 21-26
-
Tidskriftsartikel (refereegranskat)abstract
- We describe the second-order coherence functions of supercontinuum (SC) in terms of elementary fields that can be obtained from measurable average quantities. The representation is based on the partition of the second-order correlation functions of SC into quasi-coherent and quasi-stationary contributions. Numerical simulations of statistical ensembles of SC pulses with different coherence properties are used to illustrate the elementary field model. Comparison with the SC coherent-mode expansion is presented, and we also simulate the propagation of the elementary fields in a dispersive fiber to demonstrate the benefits of the model.
|
|
| 24. |
- Safavi, Sohrab, et al.
(författare)
-
Physical specifications of photonic crystal slab lenses and their effects on image quality
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 29:7, s. 1829-1834
-
Tidskriftsartikel (refereegranskat)abstract
- Photonic crystal (PhC) lenses with negative refractive index have attractedintense interest because of their application in optical frequencies. In thispaper, 2-D PhC lenses with triangular lattice of cylindrical holes in dielectricmaterial are investigated. Variant physical parameters of the lens are introducedand their effects on the lens response are studied in detail. The effect ofthe surface termination is investigated by analyzing the power flux within thePhC structure. A new lens formula has been obtained which shows a linearrelation between source distance (distance between the source and the lens)and image distance (distance between the image and the lens) for any surfacetermination of the PhC lens. It is observed that the excitation of surfacewaves does not necessarily pull the image closer to the lens. The effects of thethickness and the lateral width of the lens are also analyzed.
|
|
| 25. |
- Shen, Jian Qi
(författare)
-
Double-negative atomic vapor assisted by two-photon quantum coherence
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : The Optical Society. - 0740-3224 .- 1520-8540. ; 29:11, s. 3192-3200
-
Tidskriftsartikel (refereegranskat)abstract
- A scenario for realizing simultaneously negative permittivity and permeability of a two-photon quantum-coherent atomic vapor is suggested in order to achieve a left-handed atomic medium with a negative refractive index. One of the remarkable features of the present scheme is that it can lead to a controllable manipulation of the negative refractive index of the atomic vapor. Since the electric- and magnetic-dipole allowed transitions of atoms can be excited by visible and infrared lightwaves, the refractive index of the atomic vapor can exhibit its negative refractive index at optical and near-optical frequency bands. This may be a new scheme to fabricate a negatively refracting material based on the quantum optical approach. Such a three-dimensionally isotropic negative refractive index at visible and infrared wavelengths induced by the two-photon-resonant quantum coherence would find a potential application in fabrication of superlenses for perfect imaging and subwavelength focusing.
|
|
| 26. |
- Shirai, Tomohiro, et al.
(författare)
-
Temporal ghost imaging with classical non-stationary pulsed light
- 2010
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 27:12, s. 2549-2555
-
Tidskriftsartikel (refereegranskat)abstract
- Temporal ghost imaging with classical pulses is described as a temporal counterpart of conventional ghost imaging with thermal light. A temporal object to be imaged is located in the test arm, while the reference arm consists of some simple temporal optical elements. It is shown by illustrative examples that, when a certain condition is satisfied, the correlation between intensity fluctuations in these two arms gives basically the squared modulus of the object, but it is generally distorted by the effect of the incident pulse. The resultant temporal image depends only on the single temporal variable in the reference arm, although the light in this arm never interacts with the object. Potential applications of this system are briefly discussed.
|
|
| 27. |
- Silander, Isak, 1980-, et al.
(författare)
-
Frequency modulation background signals from fiber-based electro optic modulators are caused by crosstalk
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:5, s. 916-923
-
Tidskriftsartikel (refereegranskat)abstract
- Frequency modulated spectroscopy (FMS) performed by the use of fiber-coupled electro optic modulators (FC-EOMs) is often plagued by background signals that bring in noise and, by their temperature dependence, cause severe drifts. These signals cannot be zeroed out by the conventional technique of using a carefully adjusted polarizer that can be applied to free space electro optic modulators (EOMs). This can limit the use of FC-EOMs in high performance detection techniques. Here we provide an explanation to these background signals that is based upon crosstalk between various polarization directions of light in the fixed mounted polarization-maintaining fibers and the electro optic crystal. The description provides a basis for the previously demonstrated technique that utilizes an EOM regulated simultaneously by temperature and DC voltage to eliminate background signals from systems encompassing FC-EOMs. (C) 2012 Optical Society of America
|
|
| 28. |
- Strömqvist, Gustav, et al.
(författare)
-
Temporal coherence in mirrorless optical parametric oscillators
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 29:6, s. 1194-1202
-
Tidskriftsartikel (refereegranskat)abstract
- One of the unique features of mirrorless optical parametric oscillators based on counterpropagating three-wave interactions is the narrow spectral width of the wave generated in the backward direction. In this work, we investigate experimentally and numerically the influence that a strong phase modulation in the pump has on the spectral bandwidths of the parametric waves and on the efficiency of the nonlinear interaction. The effects of group-velocity mismatch and group-velocity dispersion are elucidated. In particular, it is shown that the substantial increase in temporal coherence of the backward-generated wave can be obtained even for pumping with a temporally incoherent pump. A configuration of a mirrorless optical parametric oscillator is proposed where this gain in spectral coherence is maximized without a penalty in conversion efficiency by employing group-velocity matching of the pump and the forward-generated parametric wave.
|
|
| 29. |
- Tjörnhammar, Staffan, 1980-, et al.
(författare)
-
Numerical modeling and determination of limiting powers for volume Bragg gratings used in lasers for spectral control
- 2013
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:8, s. 2326-2332
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a model to investigate the thermal limitations of volume Bragg gratings (VBGs) used in lasers for spectral control. Also presented are the limiting optical powers, to which intracavity VBGs of different length could be subjected, before the laser operation rapidly deteriorates. The results revealed that the power limit of a VBG-locked laser is highly dependent on the length of the employed VBG. Furthermore, the power limit expressed in incident power related linearly to the radius of the laser beam irradiating the VBG.
|
|
| 30. |
- Tjörnhammar, Staffan, 1980-, et al.
(författare)
-
Thermal limitations of volume Bragg gratings used in lasers for spectral control
- 2013
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:6, s. 1402-1409
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we present experiments and calculations of the property changes of a highly reflecting volume Bragg grating (VBG) when it is used as a laser cavity mirror. A small absorption of the reflected laser beam resulted in a laser output power roll-off, increased coupling through the VBG, and a change of the spectrum from a single to a double peak at high power. The simulations revealed that an inhomogeneous temperature distribution deformed the grating such that the diffraction efficiency was reduced and the light penetrated deeper into the VBG, which accelerated the deteriorating effects. We extrapolated the power limit found in our investigations for various beam radii and absorption coefficients.
|
|
| 31. |
- Wang, Junyang, et al.
(författare)
-
Dicke narrowing in the dispersion mode of detection and in noise-immune cavity-enhanced optical heterodyne molecular spectroscopy-theory and experimental verification
- 2011
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - Washington, D. C. : The Optical Society of America. - 0740-3224 .- 1520-8540. ; 28:10, s. 2390-2401
-
Tidskriftsartikel (refereegranskat)abstract
- Dicke narrowing in both the absorption and dispersion modes of detection have been scrutinized by noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) using an isolated transition in the v(1) + v(3) + v(4)(1) - v(4)(1) band of acetylene [P(e)(33) at 6439.371 cm(-1)] at room temperature. The results represent the first (to our knowledge) demonstration of Dicke narrowing detected in dispersion, as well as by NICE-OHMS, and the paper provides thereby the first comparison of the Dicke narrowing phenomenon for the two modes of detection. It is shown that Dicke narrowing in dispersion can be described by the dispersive counterparts to the conventional Galatry and Rautian absorption line-shape functions, which are explicitly given. Spectroscopic parameters for the targeted transition were extracted in both absorption and dispersion and found to be in agreement with those previously reported for other lines and bands. The shortcomings of the Galatry model to provide physically relevant parameters in this pressure range are discussed.
|
|
| 32. |
- Wang, Junyang, et al.
(författare)
-
Speed-dependent effects in dispersion mode of detection and in noise-immune cavity-enhanced optical heterodyne molecular spectrometry : experimental demonstration and validation of predicted line shape
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - Washington : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:10, s. 2980-2989
-
Tidskriftsartikel (refereegranskat)abstract
- Speed-dependent effects (SDEs) in both the absorption and dispersion modes of detection have been detected and scrutinized by the noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) technique. The present paper achieves four objectives: (i) it provides the first demonstration of SDEs detected in dispersion, (ii) it validates the expression for a speed-dependent Voigt (SDV) dispersion line-shape function that is derived in an accompanying paper, (iii) it illustrates the influence of SDEs on the NICE-OHMS technique, and (iv) it gives the first experimental comparison of SDEs for the absorption and dispersion modes of detection. Experiments were performed using an isolated transition in the v(1) + v(3) + v(4)(1) - v(4)(1) band of acetylene [P-e (33) at 6439.371 cm(-1)] in the 100-250 Torr range at room temperature. It is shown that SDEs appear in both the absorption and dispersion modes of detection, that they can be well described by the suggested SDV dispersion line-shape function, and that they need to be taken into account if NICE-OHMS signals detected under optimal pressures are to be properly assessed. (c) 2012 Optical Society of America
|
|
| 33. |
- Wang, Junyang, et al.
(författare)
-
Speed-dependent Voigt dispersion line-shape function : applicable to techniques measuring dispersion signals
- 2012
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - Washington : Optical Society of America. - 0740-3224 .- 1520-8540. ; 29:10, s. 2971-2979
-
Tidskriftsartikel (refereegranskat)abstract
- An analytical expression for a Voigt dispersion line-shape function that incorporates speed-dependent effects (SDEs) on the collision broadening, applicable to spectroscopic techniques that measure dispersion signals, is presented. It is based upon a speed-dependent Voigt (SDV) model for absorption spectrometry that assumes that the molecular relaxation rate has a quadratic dependence on molecular speed. The expression is validated theoretically in the limit of small SDEs by demonstration that it reverts to the ordinary Voigt dispersion line-shape function and experimentally in a separate work by experiments performed by the noise-immune cavity-enhanced optical heterodyne molecular spectrometry technique. A comparison is given between the SDEs in the SDV absorption and dispersion line-shape functions. It is shown that both line shapes are affected significantly but differently by SDEs. The expression derived provides, for the first time to our knowledge, a possibility also for the techniques that measure dispersion signals to handle SDEs. (c) 2012 Optical Society of America
|
|
| 34. |
- Ye, Y. Q., et al.
(författare)
-
Omnidirectional, polarization-insensitive and broadband thin absorber in the terahertz regime
- 2010
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 27:3, s. 498-504
-
Tidskriftsartikel (refereegranskat)abstract
- A nearly omnidirectional THz absorber for both transverse electric (TE) and transverse magnetic (TM) polarizations is proposed. Through the excitation of the magnetic polariton in a metal-dielectric layer, the incident light is perfectly absorbed in a thin thickness that is about 25 times smaller than the resonance wavelength. By simply stacking several such structural layers with different geometrical dimensions, the bandwidth of this strong absorption can be effectively enhanced due to the hybridization of magnetic polaritons in different layers.
|
|
