Optimization of GaAsP/AlGaAs-based QW laser structures for high power 800 nm operation

We present a detailed study of the MOVPE growth of 800 nm diode laser structures based on the combination of a GaAsP quantum well with well-established AlGaAs waveguide structures. By optimizing the strain and thickness of the quantum well highly-reliable diode lasers with low threshold current and high efficiency were demonstrated. 100 μm aperture “broad area” devices mounted epi-side up achieve a CW output power of 8.9 W with a wall-plug efficiency of 50%. These output powers represent record values for diode lasers in this wavelength range. Reliability measurements at 1.5 W and 50°C ambient temperature suggest lifetimes >10 000 h.     

Influence of oxygen in AlGaAs-based laser structures with Al-Free active region on device properties

AlGaAs-based lasers with GaAsP active regions for emission wavelengths near 730 nm and 800 nm were studied. Trimethyl aluminum sources with different levels of oxygen concentration were used for the deposition of the laser structures. The laser data show that the oxygen level in the AlGaAs wave guides is very critical for the performance of the 730 nm devices, even for the use of an Al-free active region, while its influence is weak for the 800 nm devices. Using the TMAl source leading to the lowest O-uptake in the AlGaAs wave guides from such structures, 7 W output power and a degradation rate of 1 10⁻⁵h⁻¹ at 2 W cw (100 μm stripe width × 4 mm, 25°C, 2000 h) are achieved for 730 nm emission.     

High-power laser diodes of wavelength 808 nm based on various types of asymmetric heterostructures with an ultrawide waveguide

The parameters of high-power multimode laser diodes featuring a radiation wavelength of 808 nm obtained on the basis of asymmetric heterostructures with an ultrawide waveguide in the systems of AlGaAs/GaAs and (Al)GaInP/GaInAsP/GaAs are compared. In the lasers based on an AlGaAs/GaAs system, the maximum optical power was limited by optical degradation of the SiO₂/Si mirrors and amounted to 4.7 W. In the lasers based on an (Al)GaInP/GaInAsP/GaAs system, the maximum optical power was limited by thermal saturation and equaled 7 W. The obtained results show that the (Al)GaInP/GaInAsP/GaAs system is more reliable from the standpoint of an increase in both the maximum optical power and operation life of lasers.     

Low-threshold, strained-layer, GaInP/AlGaInP GRINSCH visible diode lasers

Graded-index, separate-confinement heterostructure (GRlNSCH) semiconductor diode visible lasers employing a strained-layer GaInP single quantum well were fabricated from metalorganic chemical-vapor deposition (MOCVD)-grown epitaxial material. CW threshold current densities as low as 650 A/cm/sup 2/ were measured for uncoated, 1200- mu m-long, 15- mu m-wide ridge structures operating at 30 degrees C and emitting at 655-670 nm. A maximum output under quasi-CW conditions (100 mu s pulse length, 1% duty factor) as high as 320 mW/facet was achieved before catastrophic failure. This threshold current density is believed to be the lowest reported to date for visible light diode lasers.<>     

AlInGaAs/AlGaAs strained quantum-well ridge waveguide lasers grownby metalorganic chemical vapor deposition

AlInGaAs/AlGaAs strained quantum-well ridge waveguide diode lasers with an emission wavelength of 890 nm are presented. These devices exhibit both single spatial and longitudinal mode operation up to 30 mW of optical output power. A CW threshold current of 13 mA was obtained for a 5-μm-wide ridge waveguide having a cavity length of 500 μm. The differential quantum efficiency was 52%. The lateral and perpendicular far-field radiation patterns (FWHM) from the laser were 6° and 51°, respectively. Reliability testing on uncoated gain-guided lasers made from the same wafer showed no sudden death failures and degradation rates as low as 4.6%/kh     

Low-threshold continuous-wave 1.5-/spl mu/m GaInNAsSb lasers grown on GaAs

We present the first continuous-wave (CW) edge-emitting lasers at 1.5 /spl mu/m grown on GaAs by molecular beam epitaxy (MBE). These single quantum well (QW) devices show dramatic improvement in all areas of device performance as compared to previous reports. CW output powers as high as 140 mW (both facets) were obtained from 20 /spl mu/m /spl times/ 2450 /spl mu/m ridge-waveguide lasers possessing a threshold current density of 1.06 kA/cm/sup 2/, external quantum efficiency of 31%, and characteristic temperature T/sub 0/ of 139 K from 10/spl deg/C-60/spl deg/C. The lasing wavelength shifted 0.58 nm/K, resulting in CW laser action at 1.52 /spl mu/m at 70/spl deg/C. This is the first report of CW GaAs-based laser operation beyond 1.5 /spl mu/m. Evidence of Auger recombination and intervalence band absorption was found over the range of operation and prevented CW operation above 70/spl deg/C. Maximum CW output power was limited by insufficient thermal heatsinking; however, devices with a highly reflective (HR) coating applied to one facet produced 707 mW of pulsed output power limited by the laser driver. Similar CW output powers are expected with more sophisticated packaging and further optimization of the gain region. It is expected that such lasers will find application in next-generation optical networks as pump lasers for Raman amplifiers or doped fiber amplifiers, and could displace InP-based lasers for applications from 1.2 to 1.6 /spl mu/m.     

Single heterostructure lasers of PbS1-xSexand Pb1-xSnxSe with wide tunability

Single-heterostructure diode lasers formed by compositional interdiffusion in PbS1-xSexand Pb1-xSnxSe and by liquid-phase-epitaxy (LPE) in Pb1-xSnxSe show Performance characteristics significantly better than those observed in conventional homostructure lasers. Higher operating temperatures were obtained for all compositions, with CW operation above 77 K being achieved for compositions corresponding to wavelengths from 4.1 to 12.7 μm. Single-ended, CW powers as high as 70 mW, corresponding toeta_{ext} = 44percent were observed in PbS1-xSexdevices.     

Vertical cavity surface-emitting semiconductor laser with CWinjection laser pumping

Room-temperature CW operation of a GaAs/AlGaAs vertical cavity surface-emitting laser with a resonant periodic gain medium, using a GaAs/AlGaAs diode laser array as a pump source, is discussed. Pumping thresholds as low as 11 mW at 730 nm, output powers as high as 10 mW at 856 nm, and external quantum efficiencies as high as 70% are obtained, with considerably improved temporal and spatial coherence properties compared to the pump laser. This is the first reported operation of such a laser with an efficient, compact pump source, demonstrating its suitability for efficient integration     

Electrically injected visible (639-661 nm) vertical cavity surface emitting laser

The first electrically injected visible InAlGaP/AlGaAs vertical cavity surface emitting lasers are reported. The devices consist of an InAlGaP optical cavity active region surrounded by AlAs/AlGaAs distributed Bragg reflectors. Pulsed room temperature lasing has been observed at wavelengths from 639 to 661 nm. At 650 nm, thresholds of 30 mA at 2.7 V were measured on test devices with a 20 mu m emission diameter. Peak output power exceeds 3.3 mW.<>     

High-power single longitudinal mode operation of twin-channel substrate mesa guide (TCSM) lasers

Improved TCSM lasers with antireflection coatings have been developed that operate in a stable zero-order mode to output powers of 80 mW CW. The devices operated in a stable single longitudinal mode to powers >65 mW. This is believed to be the highest single-mode power ever reported from an individual diode laser.     

多单元半导体激光器的高亮度光纤耦合输出

设计并研制了一种多单元半导体激光器的高亮度光纤耦合输出模块.激光器芯片采用分子束外延(MBE)方法生长的宽波导、双量子阱结构AlGaAs/GaAs激光器外延材料,激光器模块采用4只准直的单条形大功率半导体激光器,器件腔长为2 mm,发光区宽度为100μm,单条形器件的连续输出功率为5.0 W,每两只单条形器件的准直输出光束经过空间合束后再通过偏振合束,实现了多单元器件输出的高光束质量功率合成,采用简单的平凸透镜实现了合束光束与100μm芯径、数值孔径(NA)0.22石英光纤的高效耦合,耦合效率高达79%,输出功率达10.17 W,光纤端面功率密度达1.0×105W/cm2.     

808 nm大功率无铝有源区非对称波导结构激光器

采用分别限制非对称波导结构,将光场从对称分布变为非对称分布,降低了载流子光吸收损耗,并允许p型区具有更高的掺杂水平,从而使器件电阻降低.对GaAsP/GaInP张应变单量子阱(SQW)非对称波导结构激光器的光场特性进行了理论分析,设计了波导层厚度,并制作了波长为808 nm的无铝有源区大功率半导体激光器.器件综合特性测试结果为:腔长900μm器件的阈值电流密度典型值为400 A/cm2,内损耗低至1.0 cm-1;连续工作条件下,150μm条宽器件输出功率达到6 W,最大斜率效率为1.25 W/A.器件激射波长为807.5 nm,平行和垂直结的发散角分别为3.0°和34.8°.20~70℃范围内特征温度达到133 K.结果表明,分别限制非对称波导结构是降低内损耗,提高大功率半导体激光器特性的有效措施.     

High-power lasers (λ = 940–980 nm) based on asymmetric GaInAs/GaInAsP/AlGaAs separate-confinement heterostructure

Asymmetric GaInAs/GaInAsP/AlGaAs heterostructures with the emission wavelength of 940 and 980 nm were grown by MOCVD. The composition of solid solution in the waveguide layer, Ga_0.74In_0.26As_0.47P_0.53, was chosen based on the calculations of the escape energy of electrons from the quantum well of the active region into the waveguide. Semiconductor lasers with the emission aperture of 100 μm were fabricated from these heterostructures. The CW output optical power of 12 W was achieved at room temperature. The internal optical loss was 0.6 and 0.3 cm^?1 for 940 and 980 nm wavelengths, respectively.     

GaInAsP/GaInP/AlGaInP MOCVD-grown diode lasers emitting at 808 nm

The MOCVD epitaxy has been used to grow the GaInAsP/GaInP/AlGaInP laser heterostructures with a narrow symmetric waveguide and broad asymmetric waveguide. Mesa stripe 100 μm aperture diode lasers emitting at 808 nm were manufactured. It is shown that a SiO₂/Si dielectric mirror coating of Fabry-Perot faces of Al-free semiconductor lasers does not result in catastrophic optical mirror damage. It is found that the maximum optical output power of Al-free diode lasers is limited by catastrophic optical damage of the laser heterostructure. Maximum values of optical output power of 5.1 and 9.9 W have been attained in diode lasers with a narrow symmetric waveguide and broad asymmetric waveguide, respectively.

     

Hollow cathode metal ion lasers

A new class of metal ion lasers with significant CW output power in the UV (220-320 nm) and near IR (800-2000 nm) spectral regions is described. In a hollow cathode discharge the upper laser levels are excited via charge transfer collisions between ground state buffer gas ions and ground state metal atoms. At the present stage of development, hollow cathode metal ion lasers are shown to be comparable in UV output power to rare-gas ion lasers but with lower threshold currents by a factor of more than twenty. Visible output powers are lower than rare-gas ion lasers. In the text we present device progress to date, measurements of important plasma parameters, and an outline of potential applications of hollow cathode metal ion lasers.     

High-power laser diodes with an emission wavelength of 835 nm on the basis of various types of heterostructures

Optical and electrical characteristics of different high-power multimode laser diodes with an emission wavelength of 835 nm are compared; the diodes were obtained on the basis of three systems of solid solutions: AlGaAS/GaAs, AlGaAs/GaAsP, and (Al)GaInP/GaInAsP. An output continuous optical power of 5 W is attained in lasers with a stripe width of 80 μm irrespective of the chosen material system. The highest optical power, 7 W, is attained in the lasers based on the (Al)GaInP/GaInAsP system.     

High-performance 670-nm AlGaInP/GaInP visible strained quantum welllasers

We have grown high-performance AlGaInP/GaInP visible (670 mn) strained quantum well lasers by low-pressure metalorganic chemical vapor deposition. With AlInP cladding layer, a high-power AlGaInP/GaInP visible laser diode is achieved. Its threshold current is about 30 mA. The output power of this laser diode can maintain, at least, at 32 mW under continuous-wave (CW) operation at room temperature. High slope efficiency (0.8 mW/mA) and differential quantum efficiency (0.87) can be achieved. To improve beam quality, AlGaInP/GaInP visible lasers with and without depressed index cladding layer are theoretically and experimentally studied. From experimental results, the transverse beam divergence can be reduced from 41.4° to 26.2° while maintaining a low threshold current (from 36 mA to 46 mA). By using the transfer matrix method, our theoretical calculations are in good agreement with the experimental results     

High-performance 980 nm quantum dot lasers for high-powerapplications

High-performance quantum dot lasers emitting at 980 nm with output powers of up to 4 W CW from a single facet (AR/HR coating, 100 μm stripe width) have been fabricated. Wall-plug efficiencies >50%, were achieved at room temperature. Owing to an improved carrier confinement output powers as high as 1 W CW can be obtained from the fundamental dot transition even at temperatures as high as 110°C     

High speed performance of 2-D vertical-cavity laser diode arrays

We have fabricated and tested 10×10 independently addressable vertical-cavity surface-emitting laser diode arrays. Arrays with 55 μm active diameter devices show an average threshold current density of 590 A/cm² and an excellent homogeneity of the output characteristics over the full array size with maximum CW output powers of 12 mW. Broad area laser diodes with active diameters of 75 μm reach output powers of 18 mW for CW operation and 180 mW under pulsed conditions. Small-signal modulation bandwidths are beyond 10 and 8 GHz for the 55 and 75 μm devices, respectively     

Towards high performance GaInAsN/GaAsN laser diodes in 1.5 μmrange

GaInAsN/GaAsN/AlGaAs double quantum well lasers with emission at 1.49 μm grown by solid source molecular beam epitaxy is investigated. The devices show the lowest threshold currents (120 mA) and highest output powers (130 mW pulsed) reported to date for GaAs-based 1.5 μm lasers