Showing papers on "Semiconductor optical gain published in 2005"
TL;DR: In this paper, a model describing passive mode locking, a set of differential equations with time delay, was derived and analyzed in a parameter range typical of semiconductor lasers and the limit of a slow saturable absorber was analyzed analytically.
Abstract: We derive and study a model describing passive mode locking---a set of differential equations with time delay. Unlike classical mode locking models based on the Haus master equation, this model does not assume small gain and loss per cavity round trip. Therefore, it is valid in a parameter range typical of semiconductor lasers. The limit of a slow saturable absorber is analyzed analytically. Bifurcations responsible for the appearance and breakup of the mode locking regime are studied numerically.
284 citations
TL;DR: S semiconductor injection Raman laser based on triply resonant stimulated Raman scattering between quantum-confined states within the active region of a quantum cascade laser that serves as an internal optical pump leads to an enhancement of orders of magnitude in the Raman gain, high conversion efficiency and low threshold.
Abstract: The Raman effect, in which a material shifts the wavelength of an incident light beam by absorbing part of the photon's energy, has found widespread use as a powerful diagnostic tool in chemistry and materials science. Raman lasers that are currently available, used in applications such as spectroscopy and microscopy, have only a small gain (or signal amplification) and require external pumping with powerful optical lasers. A new electrically driven semiconductor laser described in this issue uses the Raman effect to shift the wavelength of an internally Raman effect to shift the wavelength of an internally generated optical beam. This low-power compact Raman laser functions through most of the infrared wavelengths, and holds promise for extending the tunability, available range and applications of semiconductor lasers. Stimulated Raman scattering is a nonlinear optical process that, in a broad variety of materials, enables the generation of optical gain at a frequency that is shifted from that of the incident radiation by an amount corresponding to the frequency of an internal oscillation of the material1,2. This effect is the basis for a broad class of tunable sources known as Raman lasers2,3. In general, these sources have only small gain (∼ 10-9 cm W-1) and therefore require external pumping with powerful lasers, which limits their applications. Here we report the realization of a semiconductor injection Raman laser designed to circumvent these limitations. The physics underlying our device differs in a fundamental way from existing Raman lasers3,4,5,6,7,8: it is based on triply resonant stimulated Raman scattering between quantum-confined states within the active region of a quantum cascade laser that serves as an internal optical pump—the device is driven electrically and no external laser pump is required. This leads to an enhancement of orders of magnitude in the Raman gain, high conversion efficiency and low threshold. Our lasers combine the advantages of nonlinear optical devices and of semiconductor injection lasers, and could lead to a new class of compact and wavelength-agile mid-and far-infrared light sources.
121 citations
TL;DR: In this paper, a theory for describing nonequilibrium dynamics in a semiconductor quantum-dot laser is presented, which is applied to a microcavity laser with a gain region consisting of an inhomogeneous distribution of quantum dots, a quantum well wetting layer, and injection pumped bulk regions.
Abstract: A theory for describing nonequilibrium dynamics in a semiconductor quantum-dot laser is presented. This theory is applied to a microcavity laser with a gain region consisting of an inhomogeneous distribution of quantum dots, a quantum-well wetting layer, and injection pumped bulk regions. Numerical results are presented and the effects of spectral hole burning, plasma heating, and many-body effects are analyzed.
102 citations
TL;DR: In this article, the authors demonstrate the reduction of the laser threshold of a commercial GaAs∕(AlGa)As vertical-cavity surface-emitting laser (VCSEL) by optical injection of spin-polarized electrons at room temperature.
Abstract: We experimentally demonstrate the reduction of the laser threshold of a commercial GaAs∕(AlGa)As vertical-cavity surface-emitting laser (VCSEL) by optical injection of spin-polarized electrons at room temperature. Calculations with a rate-equation model reproduce the measured reduction of 2.5% for injected electrons with 50% spin polarization. The model predicts an improved threshold reduction of 50% in otherwise identical VCSELs grown on a (110) substrate due to the enhanced spin lifetime in such structures.
99 citations
TL;DR: These pulses represent, to the authors' knowledge, the highest peak power generated from an all semiconductor ultrafast laser system.
Abstract: The concept of eXtreme Chirped Pulse Amplification (X-CPA) is introduced as a novel method to overcome the energy storage limit of semiconductor optical amplifiers in ultrashort pulse amplification. A colliding pulse mode-locked semiconductor laser is developed as a master oscillator and generates 600fs pulses with 6nm bandwidth at 975nm. Using a highly dispersive chirped fiber Bragg grating (1600ps/nm) as an extreme pulse stretcher and compressor, we demonstrate ~16,000 times extreme chirped pulse amplification and recompression generating optical pulses of 590fs with 1.4kW of peak power. These pulses represent, to our knowledge, the highest peak power generated from an all semiconductor ultrafast laser system.
88 citations
TL;DR: In this article, the authors reported sub-500-fs operation of a passively mode-locked diode-pumped external-cavity surface-emitting semiconductor laser at a repetition rate of 10.014 GHz.
Abstract: We report sub-500-fs operation of a passively mode-locked diode-pumped external-cavity surface-emitting semiconductor laser at a repetition rate of 10.014 GHz. For an incident pump power of 706 mW, the laser produced 486-fs soliton-like pulses, with an average output power of 30.3 mW. The role of the ac Stark effect in shaping subpicosecond pulses is demonstrated.
72 citations
TL;DR: In this paper, a fully microscopic model is used to calculate the carrier losses in semiconductor lasers due to Auger recombination and spontaneous emission, and the results show that the commonly assumed power-law dependencies of these loss processes on the plasma density break down already below the transparency point.
Abstract: A fully microscopic model is used to calculate the carrier losses in semiconductor lasers due to Auger recombination and spontaneous emission. The results show that the commonly assumed power-law dependencies of these loss processes on the plasma density break down already below the transparency point. Most significantly, the density dependent increase of the spontaneous emission changes from quadratic to linear, while the increase of the Auger recombination is reduced from cubic to approximately quadratic or even less.
68 citations
TL;DR: In this paper, a simple semianalytical model for evaluating the free-carrier loss in the waveguide layer of large-cavity semiconductor lasers is presented, which proves that these losses may become an important factor at high bias currents.
Abstract: We present a simple semianalytical model for evaluating the free-carrier loss in the waveguide layer of large-cavity semiconductor lasers, which proves that these losses may become an important factor at high bias currents. It is shown that nonbroadened asymmetric waveguide structures can significantly reduce these losses when compared to broadened symmetric waveguides, with little or no degradation in threshold, near- and far-field properties, and are thus a promising configuration for high-power lasers operating high above threshold.
65 citations
TL;DR: In this article, the authors investigated the laser gain for AlGaN wurtzite quantum-well structures emitting in the wavelength range from ∼270to340nm, and showed that gain properties vary notably with aluminum concentration in the quantum well.
Abstract: Laser gain is investigated for AlGaN wurtzite quantum-well structures emitting in the wavelength range from ∼270to340nm. The calculations show that gain properties vary notably with aluminum concentration in the quantum well. The TE gain dominates over the entire spectral range, although an enhancement of TM gain is observed for AlGaN quantum wells with the high aluminum mole fraction. The calculations also predict an increase in threshold current density for the shorter-wavelength lasers.
62 citations
Patent•
14 Jul 2005TL;DR: In this article, a first conductive type semiconductor region is provided on a surface of GaAs, and an active layer has a pair of side surfaces on the sides and top of the active layer.
Abstract: In a semiconductor optical device, a first conductive type semiconductor region is provided on a surface of GaAs. The first conductive type semiconductor region has a first region and a second region. An active layer is provided on the first region of the first conductive type semiconductor region. The active layer has a pair of side surfaces. A second conductive type semiconductor region is provided on the sides and top of the active layer, and the second region of the first conductive type semiconductor region. The bandgap energy of the first conductive type semiconductor region is greater than that of the active layer. The bandgap energy of the second conductive type semiconductor region is greater than that of the active layer. The second region of the first conductive type semiconductor region and the second conductive type semiconductor region constitute a pn junction.
60 citations
TL;DR: Optical in-well pumping has been shown to lead to highly efficient operation of semiconductor disk-lasers using resonant absorption or using external optics as mentioned in this paper, where the output power was 1.9 W with slope efficiency up to 35% based on the incident power.
Abstract: Optical in-well pumping is shown to lead to highly efficient operation of semiconductor disk-lasers using resonant absorption or using external optics. Pump radiation absorption of 70% at 940 nm is demonstrated for a laser emitting around 980 nm. Laser output power was 1.9 W with slope efficiencies up to 35% based on the incident power.
Book•
20 Jan 2005TL;DR: In this paper, the authors describe the properties of materials from stimulated emission and absorption, as well as solid state and gas laser amplifier and oscillator, and the index of the Semiconductor Laser Index.
Abstract: Preface 1. Scalar wave equations and diffraction of laser radiation 2. Gaussian modes in optical laser cavities and Gaussian beam optics 3. Guided wave modes and their propagation 4. Guided wave interactions and photonic devices 5. Macroscopic properties of materials from stimulated emission and absorption 6. Solid state and gas laser amplifier and oscillator 7. Semiconductor lasers Index.
TL;DR: In this paper, an analytical treatment for carrier distribution in optical confinement layers (OCLs) of semiconductor lasers with bimolecular recombination is developed, and the effect of OCL recombination on the internal quantum efficiency of a laser is evaluated.
Abstract: An analytical treatment for carrier distribution in optical confinement layers (OCLs) of semiconductor lasers with bimolecular recombination is developed. On the basis of this approach, the effect of OCL recombination on the internal quantum efficiency of a laser is evaluated. It is shown that this effect can lead to a rapid deterioration in efficiency with increased waveguide thickness at high enough currents, and also contributes to the efficiency decrease with current in a given structure. An asymmetric, narrow waveguide structure is shown to avoid this problem while still providing a good-quality beam.
TL;DR: In this paper, an experimental demonstration of chaotic masking, transmission, and recovery of a 3.5GHz message using an external-cavity semiconductor laser operating at 1550 nm is presented.
Abstract: We report an experimental demonstration of chaotic masking, transmission, and recovery of a 3.5-GHz message using an external-cavity semiconductor lasers operating at 1550 nm.
Patent•
15 Mar 2005TL;DR: In this article, the authors proposed an oscillation mode of a semiconductor laser can be fixed to a single mode by feeding back beams projected from the wide stripe SLL to an active layer of the SLL, after having the beams permeate a mode transducer and a wavelength selecting filter.
Abstract: High power output can be easily obtained from a wide stripe laser, however, since its transverse mode is a multimode and an efficiency of coupling with a single mode waveguide and a single mode fiber is low, there have been problems in application to high-coherence devices. An oscillation mode of a semiconductor laser can be fixed to a single mode by feeding back beams projected from the wide stripe semiconductor laser to an active layer of the semiconductor laser, after having the beams permeate a mode transducer and a wavelength selecting filter.
TL;DR: In this article, the optical bistability of a vertical-cavity semiconductor optical amplifier (VCSOA) operated in reflection is investigated and the dependences of the optical Bistability in VCSOAs on the initial phase detuning and on the applied bias current are analyzed.
Abstract: The characteristics of optical bistability in a vertical-cavity semiconductor optical amplifier (VCSOA) operated in reflection are reported. The dependences of the optical bistability in VCSOAs on the initial phase detuning and on the applied bias current are analyzed. The optical bistability is also studied for different numbers of superimposed periods in the top distributed bragg reflector (DBR) that conform the internal cavity of the device. The appearance of the X-bistable and the clockwise bistable loops is predicted theoretically in a VCSOA operated in reflection for the first time, to the best of our knowledge. Moreover, it is also predicted that the control of the VCSOA's top reflectivity by the addition of new superimposed periods in its top DBR reduces by one order of magnitude the input power needed for the assessment of the X- and the clockwise bistable loop, compared to that required in in-plane semiconductor optical amplifiers. These results, added to the ease of fabricating two-dimensional arrays of this kind of device could be useful for the development of new optical logic or optical signal regeneration devices.
TL;DR: In this paper, a slab-coupled optical waveguide laser array with high brightness was constructed and shown to achieve linear continuous-wave power densities of 98 W/cm along the array emission aperture.
Abstract: We have constructed high brightness slab-coupled optical waveguide laser arrays. Devices in the array emit in large nearly circular single-spatial modes. We have shown that optical cross-coupling in closely spaced devices is not an issue for maintaining single-mode output, including the effects of slab-coupling. By appropriate heat-sinking, we have shown linear continuous-wave power densities of 98 W/cm along the array emission aperture.
29 Aug 2005
TL;DR: In this article, the Lamb-Dick regime of optical lattice is used as a gain medium to build a laser and the gain medium can be the alkaline-earth species, Magnesium, Calcium, and Strontium, including Ytterbium.
Abstract: Atoms with narrow-linewidth transition trapped within the Lamb-Dick regime of optical lattice are proposed be used as laser gain medium to build a laser. The gain medium atoms can be the alkaline-earth species, Magnesium, Calcium, and Strontium, including Ytterbium. These atoms possess promising super-narrow optical clock transitions, but here, this clock transition is proposed to be used as the lasing transition of the output laser. This optical lattice laser with expected super-narrow linewidth is an active optical clock with high accuracy and stability.
TL;DR: In this article, an all-optical flip-flop based on two coupled actively mode-locked fiber ring laser is described. But the flip-FLOP operation is not discussed.
Abstract: We report an all-optical flip-flop that is based on two coupled actively mode-locked fiber ring lasers. The lasers are coupled so that when one of the lasers lases, it quenches lasing in the other laser. The state of the flip-flop is determined by the wavelength of the laser that is currently lasing. The concept of the flip-flop is explained and experimental results are presented that indicate a flip-flop operation over 25-dB contrast ratio and less than 0.3-mW switching power.
TL;DR: In this article, the gain saturation dynamics of semiconductor optical amplifiers when inserted into an analog optical link is investigated. And the frequency response is shown to be a peculiar high-pass filter exhibiting two characteristic frequencies.
Abstract: We evaluate both theoretically and experimentally the gain saturation dynamics of semiconductor optical amplifiers when inserted into an analog optical link. Its impact in terms of radio frequency response, nonlinearity, and noise is investigated. In particular, the frequency response is shown to be a peculiar high-pass filter exhibiting two characteristic frequencies.
TL;DR: In this paper, a 10GHz passively mode-locked vertical external-cavity surface-emitting semiconductor laser (VECSEL) with 1.4W average output power in 6.1ps pulses is presented.
Abstract: We present a 10GHz passively mode-locked vertical external-cavity surface-emitting semiconductor laser (VECSEL) with 1.4W average output power in 6.1ps pulses. The output features a very good pulse quality with a time–bandwidth product of 0.42 in a nearly diffraction-limited beam. This demonstrates that passively mode-locked VECSELs are suitable for generating high powers in high-repetition-rate pulse trains.
12 Jun 2005
TL;DR: In this article, a multiple time scale analysis of the mode-locked laser equations is proposed for all class B (solid state and semiconductor) lasers and is detailed for a four-level laser with fast saturable losses.
Abstract: This study proposes a new multiple time scale analysis of the mode-locked laser equations. The analysis is valid for all class B (solid state and semiconductor) lasers and is detailed for a four-level laser with fast saturable losses. This work also presents the stability diagram of class B lasers, which is defined as the laser relaxation oscillation frequency.
TL;DR: In this paper, optical gain from InAs nanocrystal quantum dots which emit at 1.55microns and are imbedded in a novel polymer platform is reported. But the measurements are based on a three-beam time resolved pump-probe technique, which enables extracting the intrinsic gain cross section, lifetime, and recovery time.
Abstract: We report on the observation of optical gain from InAs nanocrystal quantum dots which emit at 1.55microns and are imbedded in a novel polymer platform. The measurements are based on a three-beam time resolved pump-probe technique, which enables extracting the intrinsic gain cross section, lifetime, and recovery time. These experiments are another step toward the realization of active optical devices based on InAs nanocrystals.
08 Apr 2005
TL;DR: In this article, a new numerical model for calculating the steady-state gain properties of asymmetrical multiple quantum well (MQW) optical amplifiers (SOAs) is presented, consisting of a rate-equation system for carriers in each quantum well, with an integrated gain model.
Abstract: A new numerical model for calculating the steady-state gain properties of asymmetrical multiple quantum well (MQW) semiconductor optical amplifiers (SOAs) is presented. The model consists of a rate-equation system for carriers in each quantum well, with an integrated gain model. Using this model, the calculated gain spectra and saturation characteristics of an asymmetrical 6-QW SOA are compared with those for symmetrical MQW SOAs. The asymmetrical MQW SOA is found to have a gain bandwidth of about 137 nm and a saturation power of -8.8 dB m at 202 mA, both greater than conventional symmetrical MQW SOAs at the same gain.
TL;DR: A methodology for treating the semiconductor laser as a current-controlled oscillator in an optical phase-lock loop is presented and the formalism is applied to phase demodulation of optical beams, reduction of phase noise by self-homodyning, and phase locking of a semiconductor lasers array.
Abstract: A methodology for treating the semiconductor laser as a current-controlled oscillator in an optical phase-lock loop is presented. The formalism is applied to phase demodulation of optical beams, reduction of phase noise by self-homodyning, and phase locking of a semiconductor laser array.
06 Mar 2005
TL;DR: Sub-picosecond timing jitter is demonstrated for 5 GHz, <10 ps optical pulses generated from monolithic passively mode-locked quantum dot lasers in this article, which makes them ideal for high speed optical interconnects.
Abstract: Sub-picosecond timing jitter is demonstrated for 5 GHz, <10 ps optical pulses generated from monolithic passively mode-locked quantum dot lasers. Their low cost, compact size and DC-biased operation make them ideal for high speed optical interconnects.
TL;DR: In this article, an experimental characterization of gain recovery is presented for a semiconductor optical amplifier saturated by a holding beam in co-and counter-propagating configurations at various wavelengths.
Abstract: We present a model for calculating the optical gain in a midinfrared GaAs∕AlGaAs quantum cascade laser in a magnetic field, based on solving the set of rate equations that describe the carrier density in each level, accounting for the optical- and acoustic-phonon scattering processes. The confinement caused by the magnetic field strongly modifies the lifetimes of electrons in the excited state and results in pronounced oscillations of the optical gain as a function of the field. Numerical results are presented for the structure designed to emit at λ∼11.4μm, with the magnetic field varying in the range of 10–60T. The effects of band nonparabolicity are also included.
03 Jun 2005
TL;DR: In this paper, a variety of mixed frequency-time-domain travelling wave models have been developed for the performance simulation of semiconductor laser optical amplifiers, and a systematic study on those models is carried out in the context of the signal-noise beating in optical amplifier, which is found that only the full wave model, which treats the beating between the signal and ASE noise in an incoherent manner, can provide the correct results, whereas the half-wave and the full-power models fail in cases where the interaction between signal and noise becomes significant.
Abstract: A variety of mixed frequency-time-domain travelling wave models have been developed for the performance simulation of semiconductor laser optical amplifiers. One of the key differences among these models lies in their treatment of the phase of the interacting optical waves (signals and noises). Based on this criterion, the models are classified into the full-wave (phases of both signal and noise considered), the half-wave (only signal phase considered), and the full-power (all phases neglected) models. A systematic study on those models is carried out in the context of the signal-noise beating in optical amplifiers. It is found that only the full-wave model, which treats the beating between the signal and ASE noise in an incoherent manner, can provide the correct results, whereas the half-wave and the full-power models fail in cases where the interaction between the signal and ASE noise becomes significant.
TL;DR: It is demonstrated that active mode-locking can be achieved for moderate alpha parameter values andSimulations indicate that large alpha parameters may destabilize the mode- locking behavior and result in irregular pulsations, which nevertheless can be effectively suppressed by incorporating detuning of individual cavity resonant frequencies in the device design.
Abstract: We investigate the operational principle of mode-locking in monolithic semiconductor lasers incorporating coupled-resonator optical waveguides. The size of mode-locked lasers operating at tens of GHz repetition frequencies can be drastically reduced owing to the significantly decreased group velocity of light. The dynamics of such devices are analyzed numerically based on a coupled-oscillator model with the gain, loss, spontaneous emission, nearest-neighbor coupling and amplitude phase coupling (as described by the linewidth enhancement factor alpha) taken into account. It is demonstrated that active mode-locking can be achieved for moderate alpha parameter values. Simulations also indicate that large alpha parameters may destabilize the mode-locking behavior and result in irregular pulsations, which nevertheless can be effectively suppressed by incorporating detuning of individual cavity resonant frequencies in the device design.