1.625-μm high-power strained multiple quantum well lasers for optical time-domain reflectometers

An optical output power exceeding 210 mW has been achieved using 1.625-μm strained multiple quantum well lasers at a forward current of 800 mA under pulsed operation. We introduced tensile-strained barrier layers to increase internal quantum efficiency. High quantum efficiency is attributed to improved of hole injection efficiency and suppressed electron overflow from wells. The 1.625-μm high-power lasers are expected to be applied to optical time-domain reflectometers, which enable regular communication light to be used.     

Stripe-geometry lasers and their properties

Design types of the stripe-geometry heterojunction laser are reviewed. Various methods for providing an electrical confinement, and/or optical confinement, are explained. The strong lateral confinement is shown to be important to stabilize the lasing filament in the cavity. Planar stripe-geometry lasers (without strong lateral optical confinement) have sometimes anomalous light output characteristics, containing kinks, discontinuities, or hysteresis loops. These irregularities are discussed in terms of optical nonlinear (self-focusing) mechanism. Problems of the electrical characterization of the continuously operating stripe-geometry lasers are considered.The author sincerely thanks his colleagues M. Osinski, A. P. Bogatov, O. G. Okhotnikov, G. T. Pak and G. G. Kharisov for their cooperation.     

λ／4相移分布反馈半导体激光器在高输出功率时的特性分析

从光场限制因子周期性主烨这一概念出发，指出在纯折射率耦合分布反馈激光器中存在着增益耦合作用，这种作用在阈值附近较小，但在输出功率增加时迅速大，并因此使λ／４相移分布反馈激光器的单模特性主。量子效应对这种增益耦合作用影响不大。在λ／４相移量子阱分布反馈激光器中，量子效应对空间烧孔效应有很强的抑制作用，因此在其高力功率值出特性出中，增益耦合的影响将变得比较明显。     

Detailed large-signal dynamic modelling of DFB laser structures and comparison with experiment

This paper describes the first general large-signal dynamic multiple-mode laser model that incorporates all the main mechanisms known to influence the dynamic behaviour of DFB laser structures with the exception of thermal effects: longitudinal mode spatial hole burning, carrier transport effects, nonlinear gain, and laser and submount parasitics. The time evolution of the output power and wavelength of all modes is predicted, and full spectra can be plotted as a function of time. The model has been extended to include an approximation to the effects of propagation down dispersive fibre, thereby allowing the simulation of filtered received eye diagrams. Detailed comparison of the model with the experimental performance of 2×/8 DFB lasers has shown good agreement, allowing the performance to be optimized, particularly with respect to longitudinal hole burning and carrier transport. The model is also applied to gain-switched operation of 2×/8 DFB structures, fast pulsing of three-section /4 DFB lasers, and the dynamic behaviour of complex coupling coefficient DFB laser structures.     

Band structures and characteristics of InGaAs/InGaAsP strain-compensated quantum well lasers

Analysis is performed for valence band structures and some characteristics of InGaAs/InGaAsP strain-compensated quantum well lasers lattice-matched to InP substrate. The computed results show that band offsets are functions of strain compensation instead of constants; strain compensation changes the band structures and the density of states, and hence affects the optical gain and the threshold current density. Under the condition of zero net strain, the values of the well width, cavity length and relative threshold carrier density and threshold current density are determined for realization of 1.55 m wavelength emission.     

Numerical study of optical properties of InGaN multi-quantum-well laser diodes with polarization-matched AlInGaN barrier layers

The optical properties of InGaN multi-quantum-well laser diodes with different polarization-matched AlInGaN barrier layers have been investigated numerically by employing an advanced device simulation program. The use of quaternary polarization-matched AlInGaN barrier layers enhances the electron–hole wave function overlap due to the compensation of polarization charges between InGaN quantum well and AlInGaN barrier layer. According to the simulation results, it is found that, among the polarization-matched quantum-well structures under study, lower threshold current and higher slope efficiency can be achieved simultaneously when the aluminum composition in AlInGaN barrier layers is about 10–15%. The optimal polarization-matched InGaN/AlInGaN laser diode shows lower threshold current and higher slope efficiency compared to conventional InGaN/InGaN laser diodes.     

Performance characteristics of deep violet InGaN DQW laser diodes with InGaN/GaN superlattice waveguide layers

The effect of the indium (In) composition of In_xGa_1−xN (GaN) waveguide layers on the performance of deep violet In_0.082Ga_0.918N/GaN double quantum well (DQW) laser diodes (LDs) emitting at 390 nm output emission wavelength has been numerically investigated. Simulation results indicated that by increasing In composition of the In_xGa_1−xN waveguide layers, the threshold current decreases, the slope efficiency, and differential quantum efficiency (DQE) increase, whereas the output power decreases. The increase in the In composition of the InGaN waveguide layers increases the refractive index and consequently increases the optical confinement factor (OCF) which result in the increase in the slope efficiency and DQE and the decrease in the threshold current. The decreasing movement of electron and hole carriers from the bulk waveguide layers to the active regions also causes to decrease the output power. A new LD structure with InGaN/GaN superlattice (SL) waveguide layers has been proposed to exploit the increased OCF of InGaN waveguide structures, and the enhanced electron and hole mobilities and the tunneling effect of the periodic structure of the SL structures. The results also showed that the use of InGaN/GaN SL waveguide structures effectively improves the output power, slope efficiency and DQE and decreases the threshold current of the LD compared with (In)GaN bulk waveguide structure.     

Optical gain analysis of strain-compensated InGaN–AlGaN quantum well active regions for lasers emitting at 420–500 nm

Strain-compensated InGaN quantum wells with tensile AlGaN barriers are analyzed as improved gain media for laser diodes emitting at 420–500 nm. The band structure is calculated using the 6-band k ·p formalism, taking into account valence band mixing, strain effect, and spontaneous and piezoelectric polarizations. The optical gain analysis exhibits significant improvement in the peak optical gain and differential gain for the strain-compensated structures. The calculation also shows a significant reduction of threshold carrier density and current density for diode lasers employing the strain-compensated InGaN–AlGaN QW active regions.     

1.55-μm InGaAs/InGaAlAs MQW vertical-cavity surface-emitting lasers with InGaAlAs/InP distributed Bragg reflectors

High-performance InGaAs/InGaAlAs multiple-quantum-well vertical-cavity surface-emitting lasers (VCSELs) with InGaAlAs/InP distributed Bragg reflectors are proposed for operation at the wavelength of . The lasers have good heat diffusion characteristic, large index contrast in DBRs, and weak temperature sensitivity. They could be fabricated either by metal-organic chemical vapor deposition (MOCVD) or by molecular beam epitaxy (MBE) growth. The laser light-current characteristics indicate that a suitable reflectivity of the DBR on the light output side in a laser makes its output power increase greatly and its lasing threshold current reduce significantly, and that a small VCSEL could output the power around its maximum for the output mirror at the reflectivity varying in a broader range than a large VCSEL does.     

Simulation studies of DFB laser longitudinal structures for narrow linewidth emission

The paper presents simulation studies targeting high-power narrow-linewidth emission from semiconductor distributed feedback (DFB) lasers. The studies contain analytic and numerical calculations of emission linewidth, side mode suppression ratio and output power for DFB lasers without phase shifts and with \(1\times \lambda /4\) and \(2\times \lambda /8\) phase shifts, taking into account the grating and facets reflectivities, the randomness of the spontaneous emission and the longitudinal photon and carrier density distributions in the laser cavity. Single device structural parameter optimization is generally associated with a trade-off between achieving a narrow linewidth and a high output power. Correlated optimization of multiple structural parameters enables the evaluation of achievable ranges of narrow linewidth and high power combinations. Devices with long cavities and low grating coupling coefficients, \(\kappa\) (keeping \(\kappa L\) values below the levels that promote re-broadening), with AR-coated facets and with a distributed phase-shift have the flattest longitudinal photon and carrier density distributions. This flatness enables stable single-longitudinal-mode operation with high side-mode-suppression ratio up to high injection current densities, which facilitates narrow linewidths and high output powers. The results reported in the paper indicate that Master-Oscillator Power-Amplifier laser structures are needed for achieving W-level high-powers with sub-MHz linewidths because most single-cavity DFB laser structural variations that reduce the linewidth also limit the achievable output power in single-mode operation.     

Semiconductor lasers with unconventional cladding structures for small beam divergence and low threshold current

Quantum well semiconductor lasers with a novel cladding design to achieve small output beam divergence and low threshold current, simultaneously are discussed. Cladding structures that cause expansion in the optical mode, while maintaining a good confinement factor, are reviewed. The design criteria and compromises are discussed in detail. The new structures offer much improved beam divergence along with low threshold current compared with conventional graded-index separate confinement heterostructure (GRINSCH) lasers. An optimized structure with the new cladding design can yield a far-field angle as low as 14.6° and a low threshold current density of 180 A cm^-2.     

利用51微米激光器测量中红外光波导损耗(英文)

一种新型的采用AlGaAs材料设计制成的光波导显示了其在中红外激光器方面的应用。波导部分包含在两个GaAs的包层之间,两个包层的掺杂材料限制光场在波导中传播并且降低损耗。三个不同长度的波导经过切入式测量得到它们的内部传播损耗为1 5dB/cm和耦合损耗为9dB。所采用的中红外激光器的波长是5 1μm,输出功率在45毫瓦以上。从光波导输出的光功率只有几个毫瓦。     

基于掩埋光栅一级分布反馈结构的太赫兹量子级联激光器

结合理论和实验研究了掩埋光栅一级分布反馈太赫兹量子级联激光器中的模式竞争和功率特性。理论计算得到掩埋光栅腐蚀深度与两个带边模式的波导损耗、光学限制因子、辐射损耗以及辐射效率的关系。理论计算表明,掩埋光栅分布反馈结构可以通过改变腐蚀深度,保证激光器稳定单模工作在高频带边模式的同时,调节激光器的阈值增益以及辐射效率。实验和测试结果表明,激光器辐射波长和掩埋光栅的周期成正比,激光器可以在整个动力学范围内稳定单模工作。单模激光器的波长范围可覆盖86.2~91.7μm的范围,边模抑制比可达25 dB,最大输出功率为9.1 mW。该工作有助于高性能单模太赫兹激光器及锁相耦合激光器阵列的研制。     

Carrier Dynamics and Saturation Effect in (113)B InAs/InP Quantum Dot Lasers

Quantum dot (QD) lasers exhibit many interesting and useful properties such as low threshold current, temperature insensitivity or chirpless behavior. In order to reach the standards of long-haul optical transmissions, 1.55 μm InAs QD lasers on InP substrate have been developed. Based on time resolved photoluminescence (PL) measurements, carrier dynamics behavior is at first investigated. Electroluminescence (EL) results are then shown at room temperature exhibiting a laser emission centered at 1.61 μm associated to a threshold current density as low as 820 A/cm² for a six InAs QD stacked layers. Finally, a rate equation model based on the reservoir theory is used to model both time-resolved photoluminescence (TRPL) and electroluminescence results. It is shown that carrier dynamic calculations are in a good agreement with measurements since the saturation effect occurring at high injected power is clearly predicted. P. Miska: Previously at Laboratoire d’Etude des Nanostructures à Semiconducteurs.     

Organic Materials for Optical Technologies

Photophysical processes in pyrane substitutes excited by high-power laser radiation are investigated. It is demonstrated that the examined molecules offer promise as active media of tunable lasers (including solid-state lasers), optical radiation limiters with = 532 nm, and emitting layers of organic light diodes.     

碟型量子阱微腔激光器的低阈值激射

利用反应离子刻蚀(RIE)和湿法腐蚀方法在InGaAs/InGaAsP多量子阱材料上研制出直径为8μm、4.5μm和2μm的碟型半导体微腔激光器。其中2μm直径的微碟在液氮温度下其光泵浦激射阈值仅为3μW左右。对高光功率密度下泵浦时出现的多模激射、跳模和激射光谱强度饱和现象进行了研究。并对微碟激光器的激射光谱线宽特性进行了初步的分析。     

Injection lasers based on AlGaAsSb/GaSb and InGaAsSb/GaSb heterostructures

The isoperiodic heterostructures AIGaAsSb/GaSb and InGaAsSb/GaSb and injection lasers based on them are investigated. It is shown that in the heterostructures of the first type it is possible to obtain very low threshold currents at room temperature at wavelengths 1.72–1.78 m. Analysis of the experimental data and interpolation characteristics show that considerable optical confinement in the investigated heterostructures of the first type. Estimates show that the minimum threshold current in heterolasers for the spectral range 1.75–1.78 m is approximately 1 kA/cm². An investigation of the InGaAsSb/GaSb heterostructures shows that a case unusual for heterostructures of III-V compounds is realized in them when the material indicated has a smaller refractive index than the wideband layers. The antiwaveguide anomaly may be useful for the development of laser structures of new types.Translated from Trudy Ordena Lenina Fizicheskogo Instituta im. P. N. Lebedeva, Vol. 141, pp. 46–61, 1983.     

Lateral Current Injection (LCI) Multiple Quantum-Well 1.55 μm Laser with Improved Gain Uniformity Across the Active Region

A simulation study of lateral current injection 1.55 m laser with strain-compensated multiple quantum-well (MQW) active region (InGaAsP well, InGaAlAs barrier) is presented using self-consistent 2D numerical simulations. The effects of different mesa width and p-doping in the QWs on the carrier and gain uniformity across the active region are explored. A high p-doping in the quantum wells is found to increases the carrier and gain non-uniformity across the active region. The QW region close to the n-contact side does not provide much gain at high optical powers. An asymmetric optical waveguide design is proposed to help reduce the gain non-uniformity across the active region. By shifting the optical modal peak toward the p-side, the modal overlap between the gain region and the optical mode is improved and a more even carrier and gain distribution is obtained. However, due to reduced bandgap of the quaternary InGaAsP p-cladding, an enhanced electron leakage out of the QWs into the p-cladding degrades the laser efficiency and increases the threshold current. Transient time–domain simulations are also performed to determine the small-signal modulation response of the laser promising a simulated high modulation bandwidth suitable for direct-modulation applications.