| 1. |
- Adolfsson, Göran, 1981, et al.
(författare)
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Spectral engineering of semiconductor Fabry–Perot laser cavities in the weakly and strongly perturbed regimes
- 2010
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 27:1, s. 118-127
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Tidskriftsartikel (refereegranskat)abstract
- By inserting index perturbations at certain positions along a semiconductor Fabry–Perot laser cavity thethreshold gain for one or several of the longitudinal cavity modes can be selectively lowered to facilitate, e.g.,single-mode or two-color operation. Previous design methods were limited to a fairly small number of perturbations,leading to only weakly perturbed cavities and thus a limited freedom in tailoring the spectral propertiesof the laser. In our approach we fully account for all multiple-reflection events and use a search spacethat permits any distribution of the locations and lengths of the perturbations. We are therefore able to designcavities with almost arbitrary spectral properties with very low threshold gain values for, e.g., the lasingmodes of a two-color cavity. Constraining the design by reducing the geometrical freedom, which can be used toincrease the smallest feature size to simplify fabrication, we seamlessly approach the weakly perturbed regimewhile maintaining much of the freedom for spectral engineering.
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| 2. |
- Akram, Nadeem, 1971-, et al.
(författare)
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Experimental characterization of high-speed 1.55 mu m buried heterostructure InGaAsP/InGaAlAs quantum-well lasers
- 2009
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 26:2, s. 318-327
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Tidskriftsartikel (refereegranskat)abstract
- Detailed experimental characterization is performed for 1550 nm semi-insulating regrown buried heterostructure Fabry-Perot (FP) lasers having 20 InGaAsP/InGaAlAs strain-balanced quantum wells (QWs) in the active region. Light-current-voltage performance, electrical impedance, small-signal response below and above threshold, amplified spontaneous emission spectrum below threshold and relative intensity noise spectrum are measured. Different laser parameters such as external differential quantum efficiency eta(d), background optical loss alpha(i), K-factor, D-factor, characteristic temperature T-0, differential gain dg/dn, gain-compression factor epsilon, carrier density versus current, differential carrier lifetime tau(d), optical gain spectrum below threshold, and chirp parameter alpha are extracted from these measurements. The FP lasers exhibited a high T-0 (78-86.5 degrees C) and very high-resonance frequency (23.7 GHz). The results indicate that appropriately designed lasers having a large number of InGaAsP well/InGaAlAs barrier QWs with shallow valence-band discontinuity can be useful for un-cooled high-speed direct-modulated laser applications.
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| 3. |
- Ali, Mona, et al.
(författare)
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Measuring the nonlinear optical properties of indium tin oxide thin film using femtosecond laser pulses
- 2020
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 37:11, s. A139-A146
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the nonlinear optical properties of indium tin oxide (ITO) thin film coated on soda-lime glass substrate using the z-scan technique. With 100 fs laser pulses, the nonlinear absorption coefficient and nonlinear refractive index are measured at different excitation wavelengths and at different incident intensities. The nonlinear optical absorption shows a competition between saturable absorption and reverse saturable absorption at the different excitation wavelengths and incident intensities. A transition from saturable to reverse saturable absorption was observed with increasing excitation wavelengths. The measured nonlinear refractive index was found to be dependent on wavelength with a maximum value of 5.34 x 10(-12) cm(2)/W at wavelength of 900 nm.
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| 4. |
- Andersson, Dan, 1966, et al.
(författare)
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Wave-breaking-free pulses in nonlinear-optical fibers
- 1993
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Ingår i: Journal of the Optical Society of America B: Optical Physics. - 1520-8540 .- 0740-3224. ; 10:7, s. 1185-1190
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Tidskriftsartikel (refereegranskat)abstract
- A qualitative as well as quantitative investigation is made of the conditions for avoiding wave breaking during pulse propagation in optical fibers. In particular, it is shown that pulses having a parabolic intensity variation are approximate wave-breaking-free solutions of the nonlinear Schrodinger equation in the high-intensity limit. A simple expression for the compression factor of a fiber-grating compressor based on parabolic pulses is also derived.
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| 5. |
- Axner, Ove, et al.
(författare)
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Ability of gas modulation to reduce the pickup of drifts in refractometry
- 2021
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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
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Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology for assessment of gas refractivity, molar density, and pressure that, by a rapid gas modulation, exhibits a reduced susceptibility to various types of disturbances. Although previously demonstrated experimentally, no detailed analysis of its ability to reduce the pickup of drifts has yet been given. This work provides an explication of to what extent modulated refractometry in general, and GAMOR in particular, can reduce drifts, predominantly those of the cavity lengths, gas leakages, and outgassing. It is indicated that the methodology is insensitive to the linear parts of so-called campaign-persistent drifts and that it has a significantly reduced susceptibility to others. This makes the methodology suitable for high-accuracy assessments and out-of-laboratory applications.
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| 6. |
- Axner, Ove, et al.
(författare)
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Ability of gas modulation to reduce the pickup of drifts in refractometry
- 2021
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optica Publishing Group. - 0740-3224 .- 1520-8540. ; 38:8, s. 2419-2436
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Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology for assessment of gas refractivity, molar density, and pressure that, by a rapid gas modulation, exhibits a reduced susceptibility to various types of disturbances. Although previously demonstrated experimentally, no detailed analysis of its ability to reduce the pickup of drifts has yet been given. This work provides an explication of to what extent modulated refractometry in general, and GAMOR in particular, can reduce drifts, predominantly those of the cavity lengths, gas leakages, and outgassing. It is indicated that the methodology is insensitive to the linear parts of so-called campaign-persistent drifts and that it has a significantly reduced susceptibility to others. This makes the methodology suitable for high-accuracy assessments and out-of-laboratory applications
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| 7. |
- Axner, Ove, et al.
(författare)
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Ability of gas modulation to reduce the pickup of fluctuations in refractometry
- 2020
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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
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Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry is a technique for assessment of gas refractivity, density, and pressure that, by a rapid modulation of the gas, provides a means to significantly reduce the pickup of fluctuations. Although its unique feature has previously been demonstrated, no detailed explication or analysis of this ability has yet been given. This work provides a theoretical explanation, in terms of the length of the modulation cycle, of the extent to which gas modulation can reduce the pickup of fluctuations. It is indicated that a rapid modulation can significantly reduce the influence of fluctuations with Fourier frequencies lower than the inverse of the modulation cycle length, which often are those that dominate. The predictions are confirmed experimentally
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| 8. |
- Baev, A., et al.
(författare)
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Bi-directional description of amplified spontaneous emission induced by three-photon absorption
- 2005
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 22:2, s. 385-393
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Tidskriftsartikel (refereegranskat)abstract
- A semiclassical dynamic theory of the nonlinear propagation of a few interacting intense light pulses is applied to study the nonlinear counterpropagation of amplified spontaneous emission (ASE) induced by three-photon absorption of short intense laser pulses in a chromophore solution. Several important results from the modeling are reached for the ASE process developing in the regime of strong saturation. Accounting for ASE in both forward and backward directions with respect to the pump pulse results in a smaller efficiency of nonlinear conversion for the forward ASE compared with the case in which forward emission is considered alone, something that results from the partial repump of the absorbed energy to the backward ASE component; the overall efficiency is nevertheless higher than for the forward emission considered alone. The efficiency of nonlinear conversion of the pump energy to the counterpropagating ASE pulses is strongly dependent on the concentration of active molecules so that a particular combination of concentration versus cell length optimizes the conversion coefficient. Under certain specified conditions, the ASE effect is found to be oscillatory; the origin of oscillations is dynamical competition between stimulated emission and off-resonant absorption. This result can be considered one of the possible explanations of the temporal fluctuations of the forward ASE pulse [Nature 415, 767 (2002)].
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| 9. |
- Baev, Alexander, et al.
(författare)
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Upconverted lasing based on many-photon absorption : an all dynamic description
- 2004
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 21:2, s. 384-396
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Tidskriftsartikel (refereegranskat)abstract
- A theory is developed for the propagation through a nonlinear medium of strong pump and amplifiedspontaneous-emission pulses. The theory is based on a solution of the density matrix equations that aims at providing an adequate treatment of the nonlinear polarization of the material without addressing the Taylor expansion over the powers of intensity. The theory has been applied for modeling of three-photon absorption induced upconverted stimulated emission of organic molecules in solvents. Numerical results are presented for the organic chromophore 4-[N-(2-hydroxyethyl)-N-(methyl)amino phenyl]-4'-(6-hydroxyhexyl sulfonyl) stilbene dissolved in dimethyl sulfoxide. The results are in good agreement with available experimental results.
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| 10. |
- Basieva, Irina
(författare)
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Theoretical method for states dynamics and entanglement optimization in bichromatically driven clusters of two and four resonantly interacting particles
- 2013
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 30:7, s. 1804-1814
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Tidskriftsartikel (refereegranskat)abstract
- Bichromatic laser pumping is an effective tool to control (e. g., to drive into an entangled state) solid-state quantum bits of different nature. For clusters of resonantly interacting ions under bichromatic laser pumping, we present a theoretical approach and approximate analytical solution for quantum states dynamics. The solution provides an optimal ratio of laser pulse intensities needed for creating the maximally entangled states and performing quantum gates. Numerical simulation corroborates the analytical results. (C) 2013 Optical Society of America
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