Showing papers on "Semiconductor optical gain published in 2002"
TL;DR: A redshift that is strongly dependent on pump power supports the idea that the electron–hole plasma mechanism is primarily responsible for the gain at room temperature and is a considerable advance towards the realization of electron-injected, nanowire-based ultraviolet–blue coherent light sources.
Abstract: There is much current interest in the optical properties of semiconductor nanowires, because the cylindrical geometry and strong two-dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale electronics and optoelectronic devices, including lasersand nonlinear optical frequency converters. Gallium nitride (GaN) is a wide-bandgap semiconductor of much practical interest, because it is widely used in electrically pumped ultraviolet-blue light-emitting diodes, lasers and photodetectors. Recent progress in microfabrication techniques has allowed stimulated emission to be observed from a variety of GaN microstructures and films. Here we report the observation of ultraviolet-blue laser action in single monocrystalline GaN nanowires, using both near-field and far-field optical microscopy to characterize the waveguide mode structure and spectral properties of the radiation at room temperature. The optical microscope images reveal radiation patterns that correlate with axial Fabry-Perot modes (Q approximately 10(3)) observed in the laser spectrum, which result from the cylindrical cavity geometry of the monocrystalline nanowires. A redshift that is strongly dependent on pump power (45 meV microJ x cm(-2)) supports the idea that the electron-hole plasma mechanism is primarily responsible for the gain at room temperature. This study is a considerable advance towards the realization of electron-injected, nanowire-based ultraviolet-blue coherent light sources.
1,207 citations
TL;DR: In this paper, the influence of p-type modulation doping on the gain characteristics of 1.3 μm InAs quantum dot lasers was investigated. But the performance of ground state lasing was not evaluated.
Abstract: Data are presented on the influence of p-type modulation doping on the gain characteristics of 1.3 μm InAs quantum dot lasers. The improvement in optical gain leads to very high characteristic temperatures for the lasing threshold that reach 161 K in the temperature range between 0 and 80 °C. 1.3 μm ground state lasing is obtained up to a temperature of 167 °C.
338 citations
TL;DR: A monolithic, mid-infrared ‘supercontinuum’ semiconductor laser is presented with a quantum cascade configuration, where a number of dissimilar intersubband optical transitions are made to cooperate in order to provide broadband optical gain from 5 to 8 µm wavelength.
Abstract: The fundamental mechanism behind laser action leads in general only to narrowband, single-wavelength emission. Several approaches for achieving spectrally broadband laser action have been put forward, such as enhancing the optical feedback in the wings of the gain spectrum, multi-peaked gain spectra, and the most favoured technique at present, ultrashort pulse excitation. Each of these approaches has drawbacks, such as a complex external laser cavity configuration, a non-flat optical gain envelope function, or an inability to operate in continuous mode, respectively. Here we present a monolithic, mid-infrared 'supercontinuum' semiconductor laser that has none of these drawbacks. We adopt a quantum cascade configuration, where a number of dissimilar intersubband optical transitions are made to cooperate in order to provide broadband optical gain from 5 to 8 microm wavelength. Laser action with a Fabry-Perot spectrum covering all wavelengths from 6 to 8 microm simultaneously is demonstrated with this approach. Lasers that emit light over such an extremely wide wavelength range are of interest for applications as varied as terabit optical data communications or ultra-precision metrology and spectroscopy.
271 citations
TL;DR: In this paper, a large diameter ridge-guided semiconductor laser weakly coupled to a straight output waveguide showed unidirectional operation and directional bistability at currents up to about twice the threshold.
Abstract: Large-diameter ridge-guided semiconductor lasers weakly coupled to a straight output waveguide show unidirectional operation and directional bistability at currents up to about twice the threshold. The direction of lasing in the ring may be controlled by biasing contacts at either end of the coupled guide.
174 citations
TL;DR: In this article, it was shown that the population of wetting-layer states leads to saturation of the population inversion in dot states and hence to the saturation of gain in a quantum-dot laser.
Abstract: Using experimental measurements of the gain–current characteristic as a function of temperature in InGaAs quantum-dot lasers, we demonstrate that it is the population of wetting-layer states that leads to a saturation of the population inversion in dot states and hence to the saturation of gain in a quantum-dot laser. At 300 K, the maximum modal gain for a three-layer structure is reduced from 53 to 14 cm−1.
158 citations
TL;DR: By using optical injection near the transparency wavelength of semiconductor optical amplifiers, the authors in this paper showed that both the saturation output power and the gain recovery can be greatly improved.
Abstract: By using optical injection near the transparency wavelength of semiconductor optical amplifiers, we show experimentally that both the saturation output power and the gain recovery can be greatly improved. By injecting 80 mW of pump power, we observe a 3-dB increase in saturation output power. For 73 mW of pump power, we find a reduction in gain recovery time from over 200 ps down to below 40 ps, while maintaining 14 dB of fiber-to-fiber gain at 1555-nm wavelength.
137 citations
TL;DR: In this paper, gain in current-driven semiconductor heterostructure devices is calculated within the theory of nonequilibrium Green functions, without relying on any sort of Kadanoff-Baym ansatz.
Abstract: Gain in current-driven semiconductor heterostructure devices is calculated within the theory of nonequilibrium Green functions. In order to treat the nonequilibrium distribution self-consistently the full two-time structure of the theory is employed without relying on any sort of Kadanoff-Baym ansatz. The results are independent of the choice of the electromagnetic field if the variation of the self-energy is taken into account. Excellent quantitative agreement is obtained with the experimental gain spectrum of a quantum cascade laser. Calculations for semiconductor superlattices show that the simple two-time miniband transport model gives reliable results for large miniband widths at room temperature.
127 citations
TL;DR: In this article, a compact variable all-optical buffer using semiconductor quantum dot structures is proposed, which is achieved by slowing down the optical signal using an external control light source to vary the dispersion characteristic.
Abstract: A compact variable all-optical buffer using semiconductor quantum dot structures is proposed. The buffering effect is achieved by slowing down the optical signal using an external control light source to vary the dispersion characteristic of the medium. The theoretical model shows that a slow-down factor of more than 10/sup 4/ with negligible group velocity dispersion is achievable.
97 citations
TL;DR: In this article, the complete synchronization of a semiconductor laser to the injection of a chaotic oscillating optical signal that is generated by a similar SLL with external optical feedback was demonstrated.
Abstract: We experimentally demonstrate the complete synchronization of a semiconductor laser to the injection of a chaotic oscillating optical signal that is generated by a similar semiconductor laser with external optical feedback. The synchronization is characterized by sensitive dependencies on frequency detuning and injection strength and a time lag that varies reversely with the variation of the delay time in the external optical feedback of the master laser.
92 citations
Patent•
17 Jan 2002
TL;DR: A gallium nitride semiconductor laser device has an active layer composed of two quantum well layers ( 14 ) and a barrier layer ( 15 ) interposed between the two well layers, and constitutes an oscillating section as discussed by the authors.
Abstract: A gallium nitride semiconductor laser device has an active layer ( 6 ) made of a nitride semiconductor containing at least indium and gallium between an n-type cladding layer ( 5 ) and a p-type cladding layer ( 9 ) The active layer ( 6 ) is composed of two quantum well layers ( 14 ) and a barrier layer ( 15 ) interposed between the quantum well layers, and constitutes an oscillating section of the semiconductor laser device The quantum well layers ( 14 ) and the barrier layer ( 15 ) have thicknesses of, preferably, 10 nm or less In this semiconductor laser device, electrons and holes can be uniformly distributed in the two quantum well layers ( 14 ) In addition, electrons and holes are effectively injected into the quantum well layers from which electrons and holes have already been disappeared by recombination Consequently, the semiconductor laser device has an excellent laser oscillation characteristic
90 citations
TL;DR: In this article, it was shown that the pattern effect inherent in semiconductor optical amplifiers can be eliminated by using self-assembled quantum dots in the active region, which can respond as fast as < 3 ps due to intra-dot carrier relaxation, enabling operation up to 160 Gbit/s.
Abstract: It is experimentally shown that the pattern effect inherent in semiconductor optical amplifiers can be eliminated by using self-assembled quantum dots in the active region. This property comes from the ultrafast response of the dominant gain nonlinearity, or spectral-hole burning, which can respond as fast as < 3 ps due to intra-dot carrier relaxation, thereby enabling operation up to 160 Gbit/s.
TL;DR: In this paper, the influence of several design parameters on the temperature stability of the emission wavelength of 980 nm GaInAs/(Al)GaAs quantum-dot lasers was studied and the results obtained agree well with a simplified model based on the inhomogeneously broadened transitions of a quantum dot ensemble.
Abstract: The influence of several design parameters on the temperature stability of the emission wavelength of 980 nm GaInAs/(Al)GaAs quantum-dot lasers was studied. The results obtained agree well with a simplified model based on the inhomogeneously broadened transitions of a quantum-dot ensemble. Using this model, the optimum cavity design for a given gain function can be determined. Following this approach, quantum-dot lasers with low wavelength shifts of 0.16 nm/K were realized, which is only half the value of a typical GaInAs/(Al)GaAs quantum well laser.
TL;DR: In this article, a two-cascaded semiconductor optical amplifiers (SOAs) in a counter-propagating feedback configuration were used for all-optical logic NOR gates.
Abstract: The authors present a novel all-optical logic NOR gate using two-cascaded semiconductor optical. amplifiers (SOAs) in a counterpropagating feedback configuration. This configuration accentuates the gain nonlinearity due to the mutual gain modulation of the two SOAs. The all-optical NOR gate feasibility has been demonstrated delivering an extinction ratio higher than 12 dB over a wide range of wavelength.
TL;DR: In this paper, a technique called PISIC (pre-impulse step-injected current) was proposed to reduce the SOA switching time from almost 2 ns (simple-step current response) to little more than 200 ps (step with prepulse response).
Abstract: A practical way to implement a technique for the reduction of the semiconductor optical amplifier electrooptic switching time is presented. The technique, called PISIC (preimpulse step-injected current), was tested and achieved a reduction of the SOA switching times from almost 2 ns (simple-step current response) to little more than 200 ps (step with prepulse response). Forecasts obtained through simulations, using optimized values of current step and prepulse, showed even a faster optical switch response, with switching time reduction to values around 10 ps.
TL;DR: In this paper, the anisotropy of the modal gain and the linewidth enhancement factor was experimentally measured in InAs/AlGaInAs/InP semiconductor lasers with an active region composed of short wires called quantum dashes.
Abstract: The anisotropy of the modal gain and the linewidth enhancement factor was experimentally measured in InAs/AlGaInAs/InP semiconductor lasers with an active region composed of quantum confined structures in the form of short wires called quantum dashes. This anisotropy is due to the polarization dependence of the transition matrix element in these quantum nanostructures. The spectral dependence of the gain and linewidth enhancement factor was investigated in a wavelength range from 1540 to 1640 nm at subthreshold current densities. The largest gain and the smallest linewidth enhancement factor were obtained when the quantum dashes were oriented perpendicular to the axis of the laser cavity.
TL;DR: In this article, a self-consistent method that solves the Schrodinger's equation and Poisson's equation simultaneously to obtain the band structure and calculate the optical gain for type-II quantum cascade lasers is presented.
Abstract: The interband Sb-based quantum cascade lasers at mid-IR range are studied. A self-consistent method that solves the Schr\"odinger's equation and Poisson's equation simultaneously to obtain the band structure and calculate the optical gain for type-II quantum cascade lasers is presented for the first time to the best of our knowledge. We start with the formulation of band structure based on the $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ method with the inclusion of the conduction-band--valence-band coupling effect. The 8\ifmmode\times\else\texttimes\fi{}8 Hamiltonian for the k\ensuremath{\cdot}p method is block diagonalized into two 4\ifmmode\times\else\texttimes\fi{}4 blocks under the axial approximation. Explicit expressions for momentum-matrix elements for interband transitions are given. The optical gain formulation including many-body effects is then presented. The carrier accumulation in different layers and its screening effects are shown. For the lasers of our study, the carrier screening affects the peak gain wavelength by about 0.3 \ensuremath{\mu}m and the peak gain magnitude by 10%. The self-consistent model is shown to be important to give a good agreement with experimental data. The temperature dependence of the optical gain is also examined for the regular and the W-shaped type-II quantum-well structures. The optical gain for the W-shaped type-II quantum well is found to have a 50% enhancement over the regular type-II quantum well. Our model is important for designing high-power, high-efficiency, and high-temperature type-II interband cascade lasers.
TL;DR: Measurements of the optical spectra of semiconductor injection lasers with deformed cylinder resonators show strong indications of the classical Kolmogorov-Arnold-Moser transition from integrability to chaos for devices with small deformation.
Abstract: Measurements of the optical spectra of semiconductor injection lasers with deformed cylinder resonators show strong indications of the classical Kolmogorov-Arnold-Moser transition from integrability to chaos for devices with small deformation. At larger deformation, evidence for laser action on scar modes is obtained. The diode lasers operate with TE polarization, resulting in laser action on (partially) chaotic whispering-gallery modes for all deformations.
Patent•
30 Sep 2002TL;DR: In this paper, the authors describe a multi-layer structure that includes a first active semiconductor multilayer and a second semiconductor multilayer, which are configured to both absorb light of the lasing frequency and produce one of parametric light and harmonic light in response to absorbing light.
Abstract: A monolithic apparatus has a laser optical cavity. The laser optical cavity has a multi-layer structure that includes a first active semiconductor multi-layer and a second semiconductor multi-layer. The second semiconductor multi-layer is located laterally adjacent to the first active semiconductor multi-layer. The first active semiconductor multi-layer includes a sequence of quantum well structures that produce light of a lasing frequency in response to being electrically pumped. The second semiconductor multi-layer includes a sequence of quantum well structures and is configured to both absorb light of the lasing frequency and produce one of parametric light and harmonic light in response to absorbing light of the lasing frequency.
TL;DR: In this article, the authors reviewed the progress of the semiconductor arrayed waveguide gratings (AWGs) and the integrated semiconductor optical devices including the AWGs, and proposed a method to make semiconductor AWGs with sufficiently low insertion loss and polarization dependence.
Abstract: This paper reviews recent progress of the semiconductor arrayed waveguide gratings (AWGs) and the integrated semiconductor optical devices including the semiconductor AWGs. Recent research enables us to make semiconductor AWGs with sufficiently low insertion loss and polarization dependence. Using the semiconductor AWGs as core components, the integrated semiconductor optical devices are developing by integrating with the other semiconductor devices including photodetectors, optical amplifiers, and electroabsorption modulators.
TL;DR: In this article, the relationship between threshold current and optical confinement factor was investigated in order to minimize the beam divergence angle perpendicular to the junction plane (θ⊥), and it was found that θ ⊥ decreased with reduction of the optical confinement factors, whereas threshold current density increased.
Abstract: High-power blue-violet laser diodes with aspect ratio as low as 2.3 and threshold current down to 33 mA have been realized. The relationship between threshold current and optical confinement factor was investigated in order to minimize the beam divergence angle perpendicular to the junction plane (θ⊥). θ⊥ was found to decrease with reduction of the optical confinement factor, whereas threshold current density increased. A new layer structure, in which a p-typed cladding layer was located next to an AlGaN electron blocking layer, and a GaInN guiding layer was inserted between the active and the AlGaN electron blocking layer, was effective for obtaining small θ⊥ while maintaining low threshold current.
TL;DR: In this article, the authors used nonidentical quantum wells made of InGaAsP-InP materials in the external-cavity configuration of a semiconductor laser to achieve a sidemode suppression ratio better than 30 dB.
Abstract: Using semiconductor optical amplifiers with properly designed nonidentical quantum wells made of InGaAsP-InP materials in the external-cavity configuration, the semiconductor laser is broadly tunable. The tuning range covers from 1.3 /spl mu/m to 1.54 /spl mu/m. Without additional filtering techniques, the laser beam emitted from the linear external cavity has the sidemode suppression ratio better than 30 dB. Also, the power ratio of the lasing mode to the total output power is 90%-99%, indicating the dominance of the lasing mode in the amplification process due to the broad gain spectrum.
TL;DR: In this article, the results of two techniques for optical carrier regeneration and wavelength reuse using semiconductor optical amplifiers (SOAs) are presented, where the main objective is to recover an optical carrier by erasing its amplitude modulation.
Abstract: The results of two techniques for optical carrier regeneration and wavelength reuse using semiconductor optical amplifiers (SOAs) are presented in this paper. The main objective is to recover an optical carrier by erasing its amplitude modulation. The first technique employs gain compression of deeply saturated SOAs. The second technique uses a feed-forward approach, where a delayed current signal is injected into the SOA with the same shape of the incoming optical pulse. The second technique could be capable to recover the optical carrier with less than 3-dB noise. However, it was observed that the SOA gain recovery time limits the maximum usable bit rate. Theoretical simulation showed good agreement with experimental results.
TL;DR: In this paper, a novel technique to improve an analog optical transmission performance by reducing both the nonlinearity and chromatic dispersion induced carrier suppression has been proposed, where the intrinsic nonlinear distortion component of MZM was reduced by gain saturation characteristics of semiconductor optical amplifier (SOA).
Abstract: A novel technique to improve an analog optical transmission performance by reducing both the nonlinearity and chromatic dispersion induced carrier suppression has been proposed. The intrinsic nonlinear distortion component of Mach-Zehnder modulator (MZM) was reduced by gain saturation characteristics of semiconductor optical amplifier (SOA). The composite triple beat (CTB) of MZM was reduced as much as 9 dB at the quadratic bias point and the following enhancement of dynamic range by 4.5 dB was obtained. The RF carrier suppression for the transmission length and operating frequency was reduced by a negative chirp characteristic of semiconductor optical amplifier (SOA) and the enhancement of CTB after transmission were also achieved as a result of the linearization using SOA.
TL;DR: In this article, the Coulomb coupling of localized discrete states in a quantum dot to extended continuum states in the surrounding quantum well region strongly influences optical properties under high excitation conditions.
Abstract: The complex optical susceptibility in a quantum-dot active medium is investigated theoretically. It is found that the Coulomb coupling of the localized discrete states in a quantum dot to extended continuum states in the surrounding quantum well region strongly influence optical properties under high excitation conditions. As a result, the behavior of the carrier-induced refractive index change $\ensuremath{\delta}n$ differs significantly from that expected from the often used atomlike description, where the interaction between a quantum dot and the surrounding region involves only the transfer of electrons and holes. Furthermore, there is the possibility of increasing $\ensuremath{\delta}n$ with increasing carrier density under conditions where laser gain is present, which is a distinct departure from bulk and quantum well behavior. Therefore, quantum-dot lasers may not show beam filamentation tendency, which has been a long-standing problem in semiconductor lasers.
TL;DR: In this article, an actively modelocked fiber ring laser based on cross-gain modulation in a semiconductor optical amplifier (SOA) employed as both the gain medium and modelocking element has been demonstrated.
Abstract: A novel actively modelocked fibre ring laser based on cross-gain modulation in a semiconductor optical amplifier (SOA) employed as both the gain medium and modelocking element has been demonstrated. Stable uniform pulse trains with pulse-widths about 21 ps at 5 GHz repetition frequency were obtained. The entire laser was operated in the optical domain with a large tuning range that could probably span the whole gain region of the gain medium employed.
TL;DR: Numerically the synchronization of external-cavity semiconductor lasers in a master-slave configuration, based on a Lang-Kobayashi-type model, is studied, showing that these two types of synchronization present different robustness with respect to the noise, frequency detuning, and current modulation of the master laser.
Abstract: We study numerically the synchronization of external-cavity semiconductor lasers in a master-slave configuration, based on a Lang-Kobayashi-type model. Depending on the feedback and coupling strengths, the slave laser synchronizes with the injected optical field or with the injected field but lags in time. We show that these two types of synchronization present different robustness with respect to the noise, frequency detuning, and current modulation of the master laser.
TL;DR: In this paper, the authors demonstrate the operation of optical bistability in a widely tunable semiconductor fiber ring laser, using a semiconductor optical amplifier (SOA), using the theory of twomode competition through gain saturation in the SOA.
Abstract: We demonstrate the operation of optical bistability in a widely tunable semiconductor fiber ring laser, using a semiconductor optical amplifier (SOA). The laser can be operated in two bistable states: the spectrum of the first state has one main lasing peak with very narrow linewidth, and the second state has simultaneous oscillation of two main peaks at different wavelengths. The two bistable states can be switched to each other using either electrical or optical methods. We further explain the bistable operation using the theory of two-mode competition through gain saturation in the SOA.
Patent•
NEC1
TL;DR: In this paper, a method of irradiation of plural pulse laser beams onto one position of a non-single crystal semiconductor was proposed, where the pulses are not higher in energy density than an energy density threshold value necessary for causing a micro-crystallization of the semiconductor.
Abstract: A method of irradiation of plural pulse laser beams onto one position of a non-single crystal semiconductor, wherein the pulse laser beams are not higher in energy density than an energy density threshold value necessary for causing a micro-crystallization of the non-single crystal semiconductor.
TL;DR: In this article, the authors investigate experimentally and numerically the gain recovery time and gain compression resulting from intraband effects induced by sub-picosecond optical pulses in bulk semiconductor optical amplifiers.
Abstract: We investigate experimentally and numerically the gain recovery time and gain compression resulting from intraband effects induced by sub-picosecond optical pulses in bulk semiconductor optical amplifiers. With the help of data produced by pump-probe measurements, the dependence of the intraband gain dynamics on pulse energy, device bias current, and length is discussed. The simulation results show a good agreement with the experimental data.
Patent•
21 Jun 2002TL;DR: In this paper, the authors proposed a light source apparatus capable of realizing stable higher harmonic even when the ambient temperature is changed or the output power fluctuates, which includes a semiconductor laser light source (4), an optical waveguide type QPM-SHG device (5), and means for detecting a change of the output light power when the wavelength of the light emitted from the SLL light source is changed.
Abstract: A light source apparatus capable of realizing stable higher harmonic even when the ambient temperature is changed or the output power fluctuates. The light source apparatus includes a semiconductor laser light source (4), an optical waveguide type QPM-SHG device (5) generating a second higher harmonic from the light emitted from the semiconductor laser light source (4), wavelength control means (7) for controlling the wavelength of the light emitted from the semiconductor laser light source (4), wavelength fine fluctuation means (8) for changing the wavelength of the light emitted from the semiconductor laser light source (4), and means for detecting a change of the output light power of the optical waveguide type GPM-SHG device (5) when the wavelength of the light emitted from the semiconductor laser light source (4) is changed. In this case, according to the change of the output light power of the optical waveguide type GPM-SHG device (5) when the wavelength of the light emitted from the semiconductor laser light source (4) is changed, the wavelength of the light emitted from the semiconductor laser light source (4) is controlled so as to be optimal for the optical waveguide type QPM-SHG device (5).