Showing papers in "IEEE Journal of Quantum Electronics in 1996"
TL;DR: In this paper, the authors describe a novel photonic oscillator that converts continuous-light energy into stable and spectrally pure microwave signals, which can be used for high-frequency reference regeneration and distribution, high gain frequency multiplication, comb frequency and pulse generation, carrier recovery, and clock recovery.
Abstract: We describe a novel photonic oscillator that converts continuous-light energy into stable and spectrally pure microwave signals. This optoelectronic oscillator (OEO) consists of a pump laser and a feedback circuit including an intensity modulator, an optical-fiber delay line, a photodetector an amplifier, and a filter. We present the results of a quasi-linear theory for describing the properties of the oscillator and their experimental verifications. Our findings indicate that the OEO can generate ultrastable, spectrally pure microwave-reference signals up to 75 GHz with a phase noise lower than -140 dBc/Hz at 10 KHz. We show that the OEO is a special voltage-controlled oscillator with an optical-output port and can be synchronized to a reference source by means of optical injection locking, electrical injection locking, and a phase-locked loop. Other OEO applications include high-frequency reference regeneration and distribution, high-gain frequency multiplication, comb frequency and pulse generation, carrier recovery, and clock recovery.
562 citations
TL;DR: In this article, the absorption and emission properties of transition metal (TM)-doped zinc chalcogenides have been investigated to understand their potential application as room-temperature, mid-infrared tunable laser media.
Abstract: The absorption and emission properties of transition metal (TM)-doped zinc chalcogenides have been investigated to understand their potential application as room-temperature, mid-infrared tunable laser media. Crystals of ZnS, ZnSe, and ZnTe, individually doped with Cr/sup 2+/, Co/sup 2+/, Ni/sup 2+/, or Fe/sup 2+/ have been evaluated. The absorption and emission properties are presented and discussed in terms of the energy levels from which they arise. The absorption spectra of the crystals studied exhibit strong bands between 1.4 and 2.0 /spl mu/m which overlap with the output of strained-layer InGaAs diodes. The room-temperature emission spectra reveal wide-band emissions from 2-3 /spl mu/m for Cr and from 2.8-4.0 /spl mu/m for Co, Cr luminesces strongly at room temperature; Co exhibits significant losses from nonradiative decay at temperatures above 200 K, and Ni and Fe only luminesce at low temperatures, Cr/sup 2+/ is estimated to have the highest quantum yield at room temperature among the media investigated with values of /spl sim/75-100%. Laser demonstrations of Cr:ZnS and Cr:ZnSe have been performed in a laser-pumped laser cavity with a Co:MgF/sub 2/ pump laser. The output of both lasers were determined to peak at wavelengths near 2.35 /spl mu/m, and both lasers demonstrated a maximum slope efficiency of approximately 20%. Based on these initial results, the Cr/sup 2+/ ion is predicted to be a highly favorable laser ion for the mid-IR when doped into the zinc chalcogenides; Co/sup 2+/ may also serve usefully, but laser demonstrations yet remain to be performed.
535 citations
TL;DR: The bound electronic nonlinear refractive index, n/sub 2/ and two-photon absorption coefficient, /spl beta/ were measured in a variety of inorganic dielectric solids at the four harmonics of the Nd:YAG laser using Z scan as discussed by the authors.
Abstract: The bound electronic nonlinear refractive index, n/sub 2/, and two-photon absorption (2PA) coefficient, /spl beta/, are measured in a variety of inorganic dielectric solids at the four harmonics of the Nd:YAG laser using Z scan. The specific materials studied are: barium fluoride (BaF/sub 2/), calcite (CaCO/sub 3/), potassium bromide (KBr), lithium fluoride (LiF), magnesium fluoride (MgF/sub 2/), sapphire (Al/sub 2/O/sub 3/), a tellurite glass (75%TeO/sub 2/+20%ZnO+5%Na/sub 2/O) and fused silica (SiO/sub 2/). We also report n/sub 2/ and /spl beta/ in three second-order, /spl chi//sup (2)/, nonlinear crystals: potassium titanyl phosphate (KTiOPO/sub 4/ or KTP), lithium niobate (LiNbO/sub 3/), and /spl beta/-barium berate (/spl beta/-BaB/sub 2/O/sub 4/ or BBO). Nonlinear absorption or refraction can alter the wavelength conversion efficiency in these materials. The results of this study are compared to a simple two-parabolic band model originally developed to describe zincblende semiconductors. This model gives the bandgap energy (E/sub g/) scaling and spectrum of the change in absorption. The dispersion of nl as obtained from a Kramers-Kronig transformation of this absorption change scales as E/sub g//sup -1/. The agreement of this theory to data for semiconductors was excellent. However, as could be expected, the agreement for these wide bandgap materials is not as good, although general trends such as increasing nonlinearity with decreasing bandgap energy can be seen.
356 citations
TL;DR: In this article, a theory for the electronic band structure and the free-carrier optical gain of wurtzite-strained quantum-well lasers is presented, taking into account the strain-induced band-edge shifts and the realistic band structures of the GaN-AlGaN wurtZite crystals.
Abstract: A theory for the electronic band structure and the free-carrier optical gain of wurtzite-strained quantum-well lasers is presented. We take into account the strain-induced band-edge shifts and the realistic band structures of the GaN wurtzite crystals. The effective-mass Hamiltonian, the basis functions, the valence band structures, the interband momentum matrix elements, and the optical gain are presented with analytical expressions and numerical results for GaN-AlGaN strained quantum-well lasers. This theoretical model provides a foundation for investigating the electronic and optical properties of wurtzite-strained quantum-well lasers.
227 citations
TL;DR: In this article, a super-structure-grating distributed Bragg reflector (SSG-DBR) was designed for broad quasicontinuous wavelength tuning with stable single-mode operation.
Abstract: The paper describes the design of a super-structure-grating distributed Bragg reflector (SSG-DBR) laser for broad quasicontinuous wavelength tuning with stable single-mode operation. The phase distributions and the effective coupling coefficients of SSG's are optimized to obtain both broad tuning range and high mode selectivity. A computer-aided simulation of wavelength tuning, where the effects of the waveguide loss increase and inhomogeneous gain spectrum are included, provides an optimum cavity structure and indicates the possibility of more than 70 mm quasicontinuous tuning in a 1.55 /spl mu/m InGaAsP-InP SSG-DBR laser. Experimental results for 34 nm quasicontinuous tuning with a properly designed device are also presented.
222 citations
TL;DR: In this paper, the fundamental mechanisms for nonlinear electro-optical effects in nematic liquid crystal films are discussed, and detailed expressions for the three principal mechanisms for space charge fields formation and various dielectric, conductivity and flow induced torques that are responsible for the liquid crystal director axis reorientation process are derived.
Abstract: We present a detailed theoretical discussion of the fundamental mechanisms for the recently observed nonlinear electro-optical effects in nematic liquid crystal films. Detailed expressions for the three principal mechanisms for space charge fields formation and various dielectric, conductivity and flow induced torques that are responsible for the liquid crystal director axis reorientation process are derived. We have observed strong optical wave mixing effects such as two-beam energy coupling and self-diffraction; the observed effects, their magnitude and dynamics, and dependencies on various physical parameters are found to be in good agreement with theories.
201 citations
TL;DR: In this paper, the authors present a theoretical model to analyze three nonlinear mechanisms that can lead to filamentation in broad-area semiconductor lasers: gain-saturation-induced changes in the refractive index through the linewidth-enhancement factor, self-focusing due to heat-induced index changes, and self-defocusing through intensity-dependent index changes in cladding layer.
Abstract: There are three nonlinear mechanisms that can lead to filamentation in broad-area semiconductor lasers: gain-saturation-induced changes in the refractive index through the linewidth-enhancement factor, self-focusing due to heat-induced index changes, and self-defocusing through intensity-dependent index changes in the cladding layer. We present a theoretical model to analyze these mechanisms and their relative roles in destabilizing the laser output. We find that there exists a critical value for the linewidth-enhancement factor below which broad area lasers are stable for wide stripe widths (as wide as 250 /spl mu/m) and high pumping levels (as high as 20 times threshold). We also find that broad-area lasers are less susceptible to filamentation through self-defocusing and show how an intensity-dependent index in the cladding layer may be used to suppress filamentation caused by the linewidth-enhancement factor.
195 citations
TL;DR: In this paper, the upconversion losses and ground-state depletion in both holmium and thulium-holmium-doped lasers were modeled for CW operation and the build-up of population inversion prior to lasing in pulsed modes of operation.
Abstract: Models for numerical simulations of laser-pumped thulium- and thulium-holmium-doped lasers have been developed. In the models, upconversion losses and ground-state depletion in both thulium and holmium are accounted for, as well as spatial dependencies of the pump and resonator modes. The models apply to CW operation and to the build-up of population inversion prior to lasing in pulsed modes of operation. It is shown that upconversion losses in Tm:Ho:YAG significantly reduce the output from the laser in both CW and Q-switched mode. Simulations of CW lasers show good agreement with experimental results.
191 citations
TL;DR: In this paper, two chaotic systems, each made by two coupled semiconductor lasers, can be synchronized using direct-optical feedback, and the robustness of the proposed synchronization scheme against mismatch of source parameters and difference in starting conditions is tested by numerical simulations.
Abstract: We demonstrate that two chaotic systems, each made by two coupled semiconductor lasers, can be synchronized using direct-optical feedback. The robustness of the proposed synchronization scheme against mismatch of source parameters and difference in starting conditions is tested by numerical simulations. Applications to secure data transmission are proposed, namely chaotic masking and chaotic shift keying (CSK).
181 citations
TL;DR: In this article, the threshold values of laser-induced optical breakdown (LIOB) on the surface of human corneal tissues, human enamel, and bovine brain tissues are presented.
Abstract: Threshold values of laser-induced optical breakdown (LIOB) on the surface of human corneal tissues, human enamel, and bovine brain tissues are presented. The data are obtained by using a regeneratively amplified Nd:YLF laser and a multistage dye laser system, respectively. The measured decrease in threshold fluence at shorter pulse durations is in good agreement with the authors' theoretical model.
181 citations
TL;DR: In this paper, the authors present a comprehensive numerical model for vertical-cavity surface-emitting lasers that includes all major processes affecting cw operation of axisymmetric devices.
Abstract: We present a comprehensive numerical model for vertical-cavity surface-emitting lasers that includes all major processes affecting cw operation of axisymmetric devices. In particular, our model includes a description of the 2-D transport of electrons and holes through the cladding layers to the quantum well(s), diffusion and recombination of these carriers within the wells, the 2-D transport of heat throughout the device, and a multilateral-mode effective index optical model. The optical gain acquired by photons traversing the quantum wells is computed including the effects of strained band structure and quantum confinement. We employ our model to predict the behavior of higher-order lateral modes in proton-implanted devices and to provide an understanding of index-guiding in devices fabricated using selective oxidation.
TL;DR: In this article, the authors proposed a technique for achieving mode-locking at very high repetition rates more than terahertz with high output power using a distributed-Bragg-reflector (DBR) laser, including an intracavity saturable absorber.
Abstract: We propose a technique for achieving mode-locking at very high repetition rates more than terahertz with high output power using a distributed-Bragg-reflector (DBR) laser, including an intracavity saturable absorber. This method is based on harmonic passive mode-locking at high gain levels and the selectivity of harmonic numbers related to the spectrum-filtering property of the intracavity Bragg reflector. Transform-limited pulses at repetition rates from 500 GHz to 1.54 THz were generated with an output power exceeding 15 mW. We studied stability of harmonic pulses by using conventional self-consistent mode-locking equations. We also discuss the effect of the spectrum-filtering properties of the intracavity Bragg reflector to the characteristics of mode-locked pulses.
ETSI1
TL;DR: In this paper, an iterative solution to the coupled Gel'Fand-Levitan-Marchenko integral equations is presented. But it is not proved that this new technique outstands other methods such as the exact GLM solution or the Fourier method.
Abstract: In this paper, we develop an iterative solution to the coupled Gel'Fand-Levitan-Marchenko integral equations. It will be proved that this new technique outstands other methods such as the exact GLM solution or the Fourier method. As one of its many applications, the synthesis of fiber gratings for dispersion equalization will be tackled.
TL;DR: In this article, the authors show that the detuning between the resonance frequencies of differently pumped DFB sections gives rise to two different pulsation mechanisms, dispersive self Q-switching of a singlemode and beating oscillations between two modes of nearly equal threshold gain.
Abstract: We show theoretically, that the detuning between the resonance frequencies of differently pumped DFB sections gives rise to two different pulsation mechanisms, 1) dispersive self Q-switching of a single-mode and 2) beating oscillations between two modes of nearly equal threshold gain. Our analysis is based on the dynamic coupled wave equations accomplished with carrier rate equations. We demonstrate the existence of certain isolated values of the detuning between both sections, at which two longitudinal eigenmodes become degenerate. In the degeneration point, the longitudinal excess factor of spontaneous emission has a singularity and the system of eigenmodes becomes incomplete. We derive reduced equations governing the dynamics in the vicinity of degeneration points. For an example device, the numerical integration of these equations clearly demonstrates the two different self pulsations with repetition rates of more than 100 GHz.
TL;DR: In this paper, the space-time profiles of ultrafast optical waveforms shaped by filtering of spatially separated frequency components are derived for single and double passes through a pulse shaping apparatus.
Abstract: A derivation of the space-time profiles of ultrafast optical waveforms shaped by filtering of spatially separated frequency components is presented. Closed form expressions for the space-time impulse response functions are given for the cases of single and double passes through a pulse shaping apparatus. For a single pass and a short unshaped pulse, diffraction by the mask filter gives rise to a translational spatial shift in the desired electric field profile that varies linearly with time along the shaped waveform. This result is completely general, and applies to frequency-domain pulse shaping with either continuous or discrete mask filters. It is also shown that double passing the apparatus does not generally reverse this effect but rather introduces further space-time coupling such as a time-varying spotsize. Examples of specific mask patterns are presented and implications for the generation of high-fidelity shaped optical waveforms are discussed.
TL;DR: The terahertz output energy saturates at a laser fluence of 40 /spl mu/J/cm/sup 2/ at low bias fields, while no clear saturation point was observed at high bias fields as mentioned in this paper.
Abstract: We report the generation of terahertz pulses with 0.4-/spl mu/J pulse energy at 1-kHz repetition rate using a large-aperture GaAs photoconductor with 3-cm gap aluminum electrodes, biased at voltages up to 45 kV. The terahertz output energy saturates at a laser fluence of 40 /spl mu/J/cm/sup 2/ at low-bias fields, while no clear saturation point was observed at high-bias fields. The output was found to be dependent on the repetition rate: at high fluences, pulse energy at 1 kHz is higher than that at 100 Hz by as much as 60%. A study of the behavior of the terahertz pulse energy and pulsewidth as a function of the pulsewidth of the laser excitation was conducted and compared with theoretical predictions. Propagation properties of the terahertz beam were also characterized, leading to a focal spot size as small as 800 /spl mu/m at the focus of a 2.5-in focal length parabolic mirror.
TL;DR: In this article, the authors present a simple method for checking the consistency of experimentally measured FROG data with the independently measured spectrum and autocorrelation of the pulse, which is a powerful way of discovering systematic errors in FROG experiments.
Abstract: We explore several practical experimental issues in measuring ultrashort laser pulses using the technique of frequency-resolved optical gating (FROG). We present a simple method for checking the consistency of experimentally measured FROG data with the independently measured spectrum and autocorrelation of the pulse. This method is a powerful way of discovering systematic errors in FROG experiments. We show how to determine the optimum sampling rate for FROG and show that this satisfies the Nyquist criterion for the laser pulse. We explore the low- and high-power limits to FROG and determine that femtojoule operation should be possible, while the effects of self-phase modulation limit the highest signal efficiency in FROG to 1%. We also show quantitatively that the temporal blurring due to a finite-thickness medium in single-shot geometries does not strongly limit the FROG technique. We explore the limiting time-bandwidth values that can be represented on a FROG trace of a given size. Finally, we report on a new measure of the FROG error that improves convergence in the presence of noise.
TL;DR: In this article, the first demonstration of laser emission from the /sup 3/F/sub 3/ to /sup 2.5/F 2/sub 2/ transition in the rare earth praseodymium was reported.
Abstract: We report the first demonstration of laser emission from the /sup 3/F/sub 3/ to /sup 3/F/sub 2/ transition in the rare earth praseodymium. This new 7-/spl mu/m solid-state laser operates with an optical efficiency of 2.3% at 293 K and 10% at 150 K using an upconversion pumping mechanism. A discussion of the dynamics in this new laser material is included.
TL;DR: In this paper, a small-signal analysis using the lumped element model shows that both the frequency and damping of the characteristic resonances of the coupled complex field and free carriers (gain medium) are modified.
Abstract: Injection locking of a semiconductor laser can induce major changes in the modulation characteristics of the laser. A small-signal analysis using the lumped element model shows that both the frequency and damping of the characteristic resonances of the coupled complex field and free carriers (gain medium) are modified. The detuning between the injected field and the free-running oscillating field, the amplitude of the injection field relative to the free-running field, the linewidth enhancement factor, the cavity photon and spontaneous carrier decay rates, and the field enhancement of the decay rate are all key parameters in determining the changes to the modulation characteristics. For a broad range of parameters, there is simultaneous enhancement of the modulation bandwidth and stable, locked operation. The enhancement is a cavity phenomena and does not occur in a traveling wave amplifier. It requires that the frequency of the locking field be detuned from the injection-modified frequency of the cavity resonance. This causes a resonant enhancement of the modulation sideband associated with the preferred frequency of the optical cavity. Bandwidth enhancements beyond the free-running laser limit are possible over a range of injection levels and injection frequency detunings.
TL;DR: In this paper, a CW pumped Nd:YAG laser using a Cr/sup 4+/:Y AG saturable absorber was achieved for the first time, providing pulses 80-300 ns wide (FWHM) with repetition rates ranging between 2 and 29 kHz.
Abstract: Repetitive Q-switching of a CW pumped Nd:YAG laser using a Cr/sup 4+/:YAG saturable absorber was achieved for the first time, providing pulses 80-300 ns wide (FWHM) with repetition rates ranging between 2 and 29 kHz. Different ranges of repetition rates and pulse widths are obtained by using absorbers of different optical densities. Satisfactory quantitative description of the experimental results is obtained by a full numerical solution of the system rate equations according to the theory of Powell and Wolga. These equations involve the dynamics of the laser population inversion, the absorber state population, and the photon density in the laser cavity.
TL;DR: In this article, the authors investigated quantum-well lasers in which electrons are injected into the quantum well ground state through tunneling, and they showed that the tunneling injection lasers are shown to have negligible gain compression, superior high-temperature performance, lower Auger recombination and wavelength chirp, and better modulation characteristics when compared to conventional lasers.
Abstract: In conventional quantum-well lasers, carriers are injected into the quantum wells with quite high energies. We have investigated quantum-well lasers in which electrons are injected into the quantum-well ground state through tunneling. The tunneling injection lasers are shown to have negligible gain compression, superior high-temperature performance, lower Auger recombination and wavelength chirp, and better modulation characteristics when compared to conventional lasers. The underlying physical principles behind the superior performance are also explored, and calculations and measurements of relaxation times in quantum wells have been made. Experimental results are presented for lasers made with a variety of material systems, InGaAs-GaAs-AlGaAs, InGaAs-GaAs-InGaAsP-InGaP, and InGaAs-InGaAsP-InP, for different applications. Both single quantum-well and multiple quantum-well tunneling injection lasers are demonstrated.
TL;DR: In this article, a stable phase locking of an electrically pumped vertical cavity surface-emitting semiconductor laser (VCSEL) was demonstrated experimentally by injecting light from an edge emitting master laser into the slave laser VCSEL cavity within a large detuning range (/spl sim/80 GHz).
Abstract: Stable phase locking of an electrically pumped vertical cavity surface-emitting semiconductor laser (VCSEL) was demonstrated experimentally by injecting light from an edge-emitting master laser into the slave laser VCSEL cavity within a large detuning range (/spl sim/80 GHz). By varying the injected power and frequency detuning, a variety of interesting nonlinear behavior was observed. A theoretical model based on two-field rate equations is presented and compared with experiment, showing good agreement.
TL;DR: In this article, the basic physical mechanisms determining the temperature dependence of the threshold current (I/sub th/) of InP-based strained-layer (SL) quantum-well (QW) lasers emitting at a wavelength of 1.3 /spl mu/m.
Abstract: We study the basic physical mechanisms determining the temperature dependence of the threshold current (I/sub th/) of InP-based strained-layer (SL) quantum-well (QW) lasers emitting at a wavelength of 1.3 /spl mu/m. We show that I/sub th/ exhibits a different temperature dependence above and below a critical temperature T/sub c/. It is indicated that T/sub c/ is the maximum temperature below which the threshold gain exhibits a linear relationship with temperature. We demonstrate that below T/sub c/ the Auger recombination current dominates the temperature dependence of I/sub th/. On the other hand, above T/sub c/ a significant increase in both the internal loss and radiative recombination current in the separate-confinement-heterostructure region, which is mainly due to electrostatic band-profile deformation, is found to play a major role in determining the temperature sensitivity of I/sub th/. On the basis of the comparison between the theoretical analysis and the experimental results, we conclude that the temperature dependence of the threshold current in 1.3-/spl mu/m InP-based SL-QW lasers is dominated by different mechanisms above and below T/sub c/.
TL;DR: In this article, the dependence of LIE irradiance thresholds on pulse duration, optical wavelength, and focal volume was examined, and the experimental data obtained is compared with a theoretical model.
Abstract: Laser-induced breakdown (LIE) thresholds are determined for pulse durations of 2.4 ps, 400 fs, and 100 fs at 580 mn in high purity water, saline and tap water. The dependence of LIE irradiance thresholds on pulse duration, optical wavelength, and focal volume is examined, and the experimental data obtained is compared with a theoretical model. The slopes of the probability curves calculated are compared with mechanisms for LIE, namely avalanche ionization, multiphoton initiated avalanche ionization, and multiphoton ionization. Lastly, the dependence of the peak breakdown electric field on pulse duration and focal volume is empirically determined and compared with previous work.
TL;DR: In this article, the basic physical mechanisms underlying tissue ablation and the laser-induced tissue effects using pulsed Er:YSGG (2.79 /spl mu/m) and Ho:YAG(2.12 ) laser radiation are presented and compared, Q-switched (/spl tau/=40 ns, E/spl les/50 mJ) and free-running (/spl τ/=250 and 400 /spl µ/s) laser energy was delivered in water via a 400-mm fiber.
Abstract: Erbium and holmium lasers are attractive for minimally invasive surgical applications as they operate at wavelengths where tissues exhibit strong absorption due to their water content and because these wavelengths are transmittable through optical fibers. In this study, the basic physical mechanisms underlying tissue ablation and the laser-induced tissue effects using pulsed Er:YSGG (2.79 /spl mu/m) and Ho:YAG (2.12 /spl mu/m) laser radiation are presented and compared, Q-switched (/spl tau/=40 ns, E/spl les/50 mJ) and free-running (/spl tau/=250 and 400 /spl mu/s) Er:YSGG (E=100 mJ) and Ho:YAG (E/spl les/1 J) laser energy was delivered in water via a 400-/spl mu/m fiber. The dimension and lifetime of the expanding and collapsing bubbles and the laser-induced pressure in water after each laser pulse were measured with fast-flash videography and time-resolved pressure measurements. Depending on the absorption coefficient, pulse energy, and pulse duration, three different regimes were distinguished: evaporation, tensile-stress-induced cavitation, and explosive vaporization. In vitro tissue effects, ablation depth, and extent of tissue damage on meniscus treated under water and on cornea treated in air were investigated and examined histologically. Er:YSGG radiation, due to its 100 times higher absorption than Ho:YAG radiation, exhibited a high tissue ablation efficiency with a relatively small zone of coagulated tissue (Q-switched 4-10 /spl mu/m, free-running less than 100 /spl mu/m), whereas the coagulated tissue zone was 300-1000 /spl mu/m after free-running and 100-120 /spl mu/m after Q-switched Ho:YAG laser impact.
TL;DR: In this paper, the authors explore the high-frequency capability of quantum-well infrared photodetectors using a microwave-rectification technique and show that the intrinsic photoconductive lifetime for these devices in the high biasing field regime is in the range of 5-6 ps.
Abstract: We explore the high-frequency capability of quantum-well infrared photodetectors using a microwave-rectification technique. We characterize a variety of devices with barrier thicknesses from 234 to 466 /spl Aring/ and number of wells from 4 to 32. Our packaged detectors have a relatively flat frequency response up to about 30 GHz. These experiments indicate that the intrinsic photoconductive lifetime for these devices in the high-biasing field regime is in the range of 5-6 ps.
TL;DR: In this paper, the quantized energy levels in quantum wells, the optical gain, the differential optical gain and the linewidth enhancement factor are presented based on a simple parabolic-band gain model.
Abstract: Analytical expressions for the quantized energy levels in quantum wells, the optical gain, the differential optical gain, and the linewidth enhancement factor are presented based on a simple parabolic-band gain model. Explicit formulas show clearly the dependence of these factors on well width, doping, and photon energy. The optical gain in the form of g=g/sub 0/ In(N/N/sub 0/) is derived using explicit approximations in the Fermi functions, where g/sub 0/ is the proportionality constant, N is the injected carrier density, and N/sub 0/ is the transparency carrier density. The approximate formulas are shown to provide not only an efficient way of computing the gain-related parameters but also a convenient way of getting physical insights into the overall interplay of quantum well parameters.
TL;DR: In this article, the authors developed a theory describing the operation of laser based on intersubband transitions in a quantum well, which combines a first-principles description of the inter-band lineshape and the optical gain with kinetic models for carrier heating.
Abstract: We have developed a theory describing the operation of lasers based on intersubband transitions in a quantum well. The theory combines a first-principles description of the intersubband lineshape and the optical gain with kinetic models for carrier heating. The theory is consistent with the experimental data available and suggests new ways of improving the laser design for room-temperature operation with high output power. At low carrier concentrations, it is possible to achieve positive values of the gain at room temperature even in the absence of an overall population inversion between quantum-well subbands. For higher (but still moderate) concentrations, the theory predicts a peculiar dependence of the output wavelength on the pump current, including a regime where the lasing wavelength switches "digitally" between two stable values.
TL;DR: Yb:BaCaBO/sub 3/F(Yb-BCBF) has been investigated as a new laser crystal with potential for self-frequency doubling, Yb/sup 3+/ in BCBF exhibits a maximum absorption cross section at 912 nm of 1.1/spl times/10/sup -20/ cm/sup 2/ with a bandwidth (FWHM) of 19 nm as mentioned in this paper.
Abstract: Yb:BaCaBO/sub 3/F(Yb:BCBF) has been investigated as a new laser crystal with potential for self-frequency doubling, Yb/sup 3+/ in BCBF exhibits a maximum absorption cross section at 912 nm of 1.1/spl times/10/sup -20/ cm/sup 2/ with a bandwidth (FWHM) of 19 nm. The maximum emission cross section at 1034 nm is 1.3/spl times/10/sup -20/ cm/sup 2/ with a transition bandwidth of 24 nm. The measured emission lifetime of Yb/sup 3+/ is 1.17 ms. An Yb:BCBF laser has been demonstrated with a Ti:sapphire pump source, and a measured slope efficiency of 38% has been obtained for the fundamental laser output. Single crystal powders of BCBF have been compared with KD/sup +/P for a relative measure of the second-harmonic generating potential, yielding d/sub eff/(BCBF)/spl sim/0.26 pm/V. The phasematching angle has been estimated from the refractive index data for type I second-harmonic generation of 0.517 /spl mu/m light; the predicted angle is 37/spl deg/ from the c-axis. The growth, spectroscopy, laser performance, and linear and nonlinear optical properties of Yb:BCBF are reported.
TL;DR: In this article, a Fabry-Perot-type Ti,Er:LiNbO/sub 3/ waveguide laser of optimized CW output power up to 63 mW at a pump power level of 210 mW and a slope efficiency of up to 37% is reported.
Abstract: The development of a Fabry-Perot-type Ti,Er:LiNbO/sub 3/ waveguide laser of optimized CW output power up to 63 mW (/spl lambda//sub s/=1561 nm) at a pump power level of 210 mW (/spl lambda//sub p/=1480 nm) and a slope efficiency of up to 37% is reported. The theoretical model for the waveguide laser is presented and applied to determine the optimum resonator configuration using waveguide parameters obtained from a detailed characterization of the laser sample. With pulsed pumping, waveguide laser pulses of up to 6.2 W peak power were observed. Apart from residual relaxation oscillations, the laser emission proved to be shot-noise limited.