Multiwavelength DFB laser array transmitters for ONTCreconfigurable optical network testbed

We discuss the design, fabrication, and performance of experimental multiwavelength laser array transmitters that have been used in the reconfigurable optical network testbed for the Optical Network Technology Consortium (ONTC). The experimental four-node multiwavelength network testbed is SONET/ATM compatible. It has employed multiwavelength DFB laser arrays with 4 nm wavelength spacing for the first time. The testbed has demonstrated that multiwavelength DFB laser arrays are indeed practical and reproducible. For the DFB laser arrays used in such a network the precise wavelength spacing in the array and the absolute wavelength control are the most challenging tasks. We have obtained wavelength accuracy better than ±0.35 nm for all lasers, with some registered to better than ±0.2 nm. We have also studied the array yield of our devices and used wavelength redundancy to improve the array yield. Coupling efficiencies between -2.1 to -4.5 dB for each wavelength channel have been obtained. It is achieved by using specially designed lensed fiber arrays placed on a silicon V-grooved substrate to exactly match the laser spacing. The transmitter consisted of a multichip module containing a DFB laser array, an eight-channel driver array based on GaAs IC's, and associated RF circuitry     

Highly uniform vertical-cavity surface-emitting lasers integratedwith microlens arrays

In this paper, work is described on the fabrication of highly uniform 8×8 arrays of GaAs-AlGaAs vertical-cavity surface-emitting lasers (VCSEL's). Oxide-confined VCSEL arrays show an average threshold current of 0.74±0.02 mA, an average output power of 2.05±0.03 mW at 8 mA and an average power conversion efficiency of 14.3%. Their wavelength is measured to be 967±0.35 nm over the array. In addition, we describe the alignment and integration of these device arrays with arrays of refractive microlenses to allow beam shaping typically required in system applications     

Monolithic multiple wavelength surface emitting laser arrays

A two-dimensional (2-D) surface emitting laser array emitting 140 unique, nonredundant, uniformly separated, single-mode wavelengths in the 980-nm regime is described. The wavelength separation between neighboring lasers is as small as 0.3 nm. A large total wavelength span of 43 nm was obtained without compromising the performance of the lasers. All 140 lasers have nearly the same threshold currents, voltages, and resistances. The techniques used are generic and can be readily extended to both longer and shorter wavelength lasers. The authors also report the first wavelength division multiplexing system experiment using part of this laser array. A BER (bit-error ratio) of 10 ^-9 at 155 Mb/s was obtained with simultaneous operation of four lasers at a wavelength separation of 1.5 nm. Negligible optical and electrical crosstalk was observed between the lasers     

High T0 long-wavelength InGaAsN quantum-well lasersgrown by GSMBE using a solid arsenic source

We demonstrate high performance, λ=1.3- and 1.4-μm wavelength InGaAsN-GaAs-InGaP quantum-well (QW) lasers grown lattice-matched to GaAs substrates by gas source molecular beam epitaxy (GSMBE) using a solid As source. Threshold current densities of 1.15 and 1.85 kA/cm² at λ=1.3 and 1.4 μm, respectively, were obtained for the lasers with a 7-μm ridge width and a 3-mm-long cavity. Internal quantum efficiencies of 82% and 52% were obtained for λ=1.3 and 1.4 μm emission, respectively, indicating that nonradiative processes are significantly reduced in the quantum well at λ=1.3 μm due to reduced N-H complex formation. These Fabry-Perot lasers also show high characteristic temperatures of T₀ =122 K and 100 K at λ=1.3 and 1.4 μm, respectively, as well as a low emission wavelength temperature dependence of (0.39±0.01) nm/°C over a temperature range of from 10°C to 60°C     

Temperature dependence of the properties of DBR mirrors used insurface normal optoelectronic devices

The variation in the center wavelength of distributed Bragg reflectors used in optoelectronic devices, such as surface emitting lasers and Fabry-Perot modulators, is measured as the temperature of the mirrors changes over the range 25°C to 105°C. An analytic expression for the shift in center wavelength with temperature is presented. The mirrors measured are made of InP/InGaAsP (λ_gap=1.15 μm), GaAs/AlAs, and Si/SiN_x. The linear shifts in center wavelength are 0.110±0.003 nm/°C, 0.087±0.003 nm/°C, and 0.067±0.007 nm/°C for the InP/InGaAsP, GaAs/AlAs, and Si/SiN mirrors, respectively. Based on these data, the change in penetration depth with temperature is calculated     

Resonant cavity-enhanced InGaAs-AlGaAs heterojunctionphototransistors with an optical design for high uniformity and yield

We present uniformity data on resonant cavity-enhanced InGaAs-AlGaAs heterojunction phototransistors (HPT's) with an optical design that promotes high uniformity and yield. The HPT's operate in the wavelength region where the GaAs substrate is transparent and the data show the HPT's to be suitable for vertical integration with optical emitters or modulators to form two-dimensional arrays of smart pixels operating in transmission mode. The absorbing region of the HPT consists of an InGaAs multiple-quantum-well structure where the quantum wells (QW's) have been distributed to make the total absorption in the cavity insensitive to growth variations as well as the spatial matching of the standing wave and absorbing QW's. Theoretically, we estimate the absorption to be 39%±1% of the incident optical power, even at wafer nonuniformities of 12.5%. With these nonuniformities, the resonant wavelength moves ±25 nm, making postgrowth tuning of the wavelength necessary. Experimentally, we show postgrowth tuning of the resonance wavelength without loss in uniformity. The arrays have good uniformity as well as very high responsivities. The average responsivity is 160 A/W ±15% from 927-955 nm. The standard deviation of a typical array is 0.5 nm in resonant wavelength and about 5% of the average responsivity. The difference between maximum and minimum values for an array is typically 3 nm in resonant wavelength and ±10% of the average responsivity     

宽谱平面阵列激光器的设计与实现

在二极管泵浦的固体激光器中,由于泵源的输出波长具有温漂特性,造成了与激光晶体吸收光谱的匹配性问题,使得泵浦效率降低,影响固体激光器的输出能量。为了避免该影响,项目组采用拓宽发射光谱覆盖范围的设计思路,开展了宽光谱平面阵列的研制工作。本文分别完成了6芯平面阵列的建模、阵列中心波长的设计、以及基于高斯光谱模型的双波长叠加的仿真工作;同时采用(2.0 nm、2.4 nm、2.8 nm、3.2 nm)四个波长间隔的芯片进行了实验验证。结果表明：在波长间隔为2.0 nm和2.4 nm时,叠加后光谱呈现单一峰状态;在波长间隔为2.8 nm和3.2 nm时,叠加光谱呈现峰谷分布,相应峰谷比的测试值分别为1.03和1.14,设计仿真与实验结果基本一致。本文为宽光谱阵列激光器非温控泵浦结构的量化计算提供了思路。     

Aging-induced wavelength shifts in 1.5-μm DFB lasers

We report measured wavelength shifts of over one hundred 1.5-μm DFB lasers aged under three different conditions far a period corresponding to the system's lifetime (~25 years). The results show that the lasers aged at lower temperature (thus higher optical power) have wider spread of wavelength shifts than the lasers aged at higher temperature. No correlation was observed between the wavelength shifts and the aging rates or the aging-induced changes in the threshold currents. The aging-induced wavelength shifts were relatively small (±1 Å) for most lasers. However, about 10% of the lasers exhibit larger wavelength shifts of up to about ±4 Å     

200°C, 96-nm wavelength range, continuous-wave lasing fromunbonded GaAs MOVPE-grown vertical cavity surface-emitting lasers

We report record temperature and wavelength range attained using MOVPE-grown AlGaAs vertical cavity surface-emitting lasers (VCSEL's). Unbonded continuous-wave lasing is achieved at temperatures up to 200°C from these top-emitting VCSEL's and operation over a 96-nm wavelength regime near 850 nm is also achieved from the same nominal design. Temperature and wavelength insensitive operation is also demonstrated; threshold current is controlled to within a factor of 2 (2.5-5 mA) for a wavelength range exceeding 50 nm and to within ±30% (5-10 mA) for a temperature range of 190°C at 870 nm     

Vertical-cavity surface-emitting laser diodes with post-growthwavelength adjustment

A novel vertical-cavity surface-emitting laser design enables the post-growth determination of the emission wavelength. The lasers employ a hybrid top mirror consisting of a semiconductor Bragg mirror and a metal reflector. The laser cavity length of each element in a 2-D array can be precisely adjusted after epitaxial growth by anodic oxidation and etching. An emission wavelength range of 25 nm is experimentally observed. Lasers operate under continuous wave conditions with threshold currents of about 6 mA and output powers up to 0.5 mW     

光纤激光器的相干输出

研究了两路光纤激光的相位锁定和相干输出, 用融锥光纤耦合器实现了两路高掺铒光纤激光之间的相互耦合。提出了在激光器高反射率前腔镜的前面加融锥光纤耦合器的方法构成简单的共振腔, 从而实现两路光纤激光的相干叠加。开展了基于融锥光纤耦合器互注入锁相的两路光纤激光器的相干合成实验, 成功实现了两路光纤激光器的注入锁定, 观察到了波长锁定（中心波长稳定在1549.8 nm, 线宽为0.08 nm）、远场干涉条纹和线宽压缩现象。分析了单个激光器和激光器阵列的斜率效率, 当反射率为70%, 抽运功率均为145 mW时, 获得最大合成功率为127 mW。     

Random lasing in vertical ZnO nanorods

Random lasing with coherent feedback is detected in the array of vertical ZnO nanorods synthesized on a Si(100) substrate. Under high-intensity optical pumping at the wavelength of 337.1 nm at room temperature, several narrow laser peaks with the width of 0.1 nm are observed in the wavelength region around 392 nm. The laser radiation is emitted in a direction orthogonal to the axis of the nanorods. Study of the behavior of the laser spectrum with the excited area shows good agreement of the data with the theory of random lasers. The mechanism of laser emission is related to the formation of closed paths of light due to multiple coherent scattering at the vertically oriented ZnO nanorods.     

Sampled grating DBR laser arrays with adjustable 0.8/1.6 nmwavelength spacing

The difficulty in fabricating multiwavelength laser arrays with uniform wavelength spacing is overcome by using sampled grating distributed Bragg reflector (DBR) lasers as the constituent of a laser array. The sampling periods of the DBR mirrors are varied from laser to laser to provide reflection combs with different spacings in wavelength. Arrays of twelve lasers have been successfully fabricated with a single holographic exposure step. The wavelength spacing among the lasers can be adjusted to be around 0.8 or 1.6 nm with a simple tuning mechanism     

Packaged frequency-stable tunable 20 kHz linewidth 1.5 ?m InGaAsP external cavity laser

Packaged grating-tuned external cavity InGaAsP/InP lasers have been developed for use in coherent transmission systems that operate at a wavelength of 1.5 ?m. The emission wavelength can be selected within a 60 nm range during manufacture, and can subsequently be tuned over 0.5 nm (63 GHz). The lasers have linewidths better than 20 kHz and show long-term relative frequency stability of better than 150 MHz.     

High-power quantum dot lasers with improved temperature stability of emission wavelength for uncooled pump sources

915 nm quantum dot lasers with temperature stable emission wavelengths have been realised for uncooled high-power applications. Broad area lasers with optimised dot geometry exhibit a thermal induced wavelength shift of 0.09 nm/K, which is 3.5 times lower than for quantum well lasers. Despite this improvement the lasers show high output powers of more than 3 W and wallplug efficiencies of 55% in continuous-wave operation.     

半导体激光器输出波长随工作电流变化的实验研究

以2W连续红外(980nm)半导体激光器(InGaAs)和120mW连续红外(980nm,带制冷器与尾纤)半导体激光器(InGaAsP)为例,测量激光器输出光束的波长随工作电流变化的规律。实验结果表明:工作电流增加,光束波长向长波红移,斜率分别近似为0.374nm/100mA、0.220nm/10mA;工作电流大时的红移现象比电流小时明显。     

GaInAs/AlGaInAs DH and MQW lasers with 1.5-1.7 mu m lasing wavelengths grown by atmospheric pressure MOVPE

The first successful growth and fabrication of long wavelength (1.5-1.7 mu m) DH and MQW lasers by atmospheric pressure MOVPE in a 'phosphorus-free' material system is reported. The GaInAs/AlGaInAs DH and MQW lasers were grown on InP substrates. DH lasers emitting at around 1690 nm exhibit threshold current densities down to 2.8 kA/cm/sup 2/ at 25 degrees C; the characteristic temperature is 50 K in the 15-55 degrees C range. First MQW lasers with 1565 nm emission wavelength have threshold current densities around 3.2 kA/cm/sup 2/.<>     

Anticompetition Between Laser Modes in Quantum-Dot Laser

Anticompetition behavior is observed in a InAs quantum-dot (QD) laser with external wavelength control. Unlike the competition behavior observed in other QD lasers, in this experiment, the laser emission induced by external feedback at the ground state wavelength improves the excited-state emission at 1170 nm by 13 dB. Such an anticompetition phenomenon is most obvious as the feedback wavelength differs from 1250 nm, the original lasing wavelength, by 15 nm. This anticompetition behavior is explained by the sharing of QDs between the laser emission induced by the feedback and the original laser oscillation     

Multiwavelength array of single-frequency stabilized Fabry-Perot lasers

We characterize the influence of controlled perturbations (slots) in the ridge waveguide of Fabry-Perot lasers emitting around 1550 nm. The slots are etched simultaneously with the ridge and each slot introduces an additional loss of 2.3 cm/sup -1/. The lasers emit with a single wavelength when more than three slots are introduced, in which case the interslot spacing strongly influences the lasing spectrum. An array of devices with differing slot arrangements are fabricated on a single chip where each laser emits at a single wavelength across a 30-nm band each with side-mode suppression ratios greater than 28 dB. The emission wavelengths are simulated with a model for lossy slots where each slot has an effective in-phase reflectivity of 0.7%.     

High efficiency AlGaInP-based 650 nm vertical-cavitysurface-emitting lasers

Record high continuous-wave output power of 3.1 mW and peak wall-plug efficiency of 14% at the wavelength of 650 nm have been achieved from oxide-confined AlGaInP-AlGaAs vertical-cavity surface-emitting lasers. At a wavelength of 657 nm laser emission is detected up to 60°C