Dual-wavelength (GaAl)As laser

A monolithic structure integrating two stripe-geometry (GaAl)As lasers emitting at 8500 and 8850 ? is described. The threshold currents for both lasers are in the 50?70 mA range. The spacing between the stripes for the device reported here is 25 ?m; it can be reduced to 10 ?m in order to optimise the direct coupling to a 50 ?m diameter fibre.     

A new monolithic composite- cavity (GaAl)As laser

A new composite-cavity (GaAl)As laser comprising a monolithically integrated pair of a laser and reflector has been developed on the basis of the chemical etching technique reported by the present authors. The rear facet of the laser and the reflector are separated by a small air gap. As a result, the new laser showed low threshold and high mode stability operation without mode jumping in a temperature range as wide as 25°C.     

A stabilized zinc diffused-proton bombarded (GaAl)As laser

A new (GaAl)As stripe laser in which a refractive index step is created by a zinc diffusion on both sides of a conventional proton stripe structure, called a diffused bombarded stripe (DBS) laser, is presented. This diffusion provides passive transverse guiding with a relatively simple technology. The index step can be adjusted by controlling the diffused zinc concentration in relation to the active region doping level. A self-alignment technique for the diffused and bombarded stripes reduces the current leakage through the diffused regions. Lasing threshold currents as low as those of conventional proton stripe lasers are obtained. A significant improvement of light-current linearity, transverse mode stability and longitudinal mode structure are observed with the DBS lasers.     

An analytic study of (GaAl)As gain guided lasers at threshold

An analysis of gain-guided diode lasers at threshold is presented. After describing the formulation, the effects of charge induced real refractive index antiguiding and gain-charge density relations are studied in detail. Their influence on the threshold current, modal distributions, and the lateral fax-field radiation patterns is discussed. Next a "model" laser is defined and each parameter including dimensions, compositions, stripewidth, diffusion constants, current spreading resistance, and facet reflectivities is individually varied to determine the resulting modifications in laser properties.     

Fundamental transverse and longitudinal mode oscillation in terraced substrate GaAs-(GaAl)As lasers

A new, simple structure for a stripe-geometry laser is proposed. A double heterostructure is fabricated on a terraced substrate, providing a modified rib-waveguide structure in the active layer. A lasing mode is confined and stabilized in the narrow area between two adjacent bends of the active layer. The terraced substrate laser exhibits a stable, single longitudinal mode oscillation as well as a fundamental transverse mode oscillation in CW operation. No kinks have been observed in light-output versus current characteristics. The linearity continues up to ten times the threshold in the pulsed operation at which the power output is 150 mW per facet.     

Low threshold-current density in 5-layer-heterostructure (GaAl)As/GaAs localised-gain-region injection lasers

Injection lasers have been constructed in which an active GaAs layer is sandwiched between a pair of (GaAl)As layers for carrier confinement and an outer pair of (GaAl)As layers of higher AlAs content for optical confinement. The minimum threshold-current density measured at 300 K. is 575±15 A/cm2 for 0.5 mm-long devices and 390 A/cm2 for lasers with four reflecting faces.     

Phase-locked (GaAl)As laser diode emitting 2.6 W CW from a single mirror

A phase-locked multiple-quantum-well (GaAl)As injection laser with a highly reflective rear facet coating and a low reflective front facet coating is reported to emit 2.6 W CW at room temperature from the front facet.     

Channelled substrate narrow stripe GaAs/(GaAl)As lasers with quarter-wavelength facet coatings

Channelled substrate narrow stripe GaAs/(GaAl)As lasers with quarter-wavelength antireflection coatings are described. These devices have low thresholds, broad spectra, high external quantum efficiencies and operate up to 10 mW in the fundamental transverse mode.     

Predicted performance of quantum-well GaAs-(GaAl)As opticalamplifiers

The gain, noise, and saturation performance of GaAs-(GaAl)As quantum-well laser amplifiers is calculated. A single-quantum-well amplifier with 100-mA injection should achieve similar gains to those of present devices with bulk active regions, but with improved saturation output powers and near-ideal noise performance. A low-current amplifier with a 2.5-mA injection current is investigated for varying well thickness and number of wells     

High-reflectivity cavity mirrors for high-performance (GaAl) As diode lasers

Effects of the high-reflectivity mirrors on the performance of (GaAl)As diode lasers are investigated by using a laser diode model. An optimum value for the mirror reflectivity is obtained by using a figure of merit which reflects low threshold and high slope efficiency. An optimum reflectivity valueR = 0.75is obtained for a laser with a cavity lengthl= 300 mum and an internal loss coefficientgamma_{i} = 10cm^-1. A higher internal photon flux density relative to the output photon flux density is shown to occur with the high-reflectivity mirror. High-reflectivity mirrors are shown to reduce optical feedback effect from external devices and the lowered threshold value to reduce the thermal effects on the modulation characteristics and the degradation.     

High-peak-power asymmetric double-heterostructure (GaAl)As-GaAs injection laser

An asymmetric double-heterostructure pulsed-power laser is described. This laser exhibits low-temperature sensitivity of optical power in the operating temperature range of ?40 to +90°C. The threshold current is below 10 A at 90°C. The power loss at 40 A and 90°C operation is at least a factor of two less severe for this structure compared to that of the single heterostructure.     

D_2~ 轰击隔离条形(GaAl)As/GaAs双异质结构激光器

在室温至600℃退火D_2~ 轰击过的GaAs单晶片,只要退火温度低于200℃,得到的电阻率可达(1～2)×10~8欧姆·厘米。用D_2~ 轰击(GaAl)As/GaAs双异质结构片,制成的隔离条形激光器,近场、光谱、频率响应及退火等特性都与H~ 轰击激光器差不多。     

Novel hemispherical vertical cavity 1.3 mu m surface-emitting laser on semi-insulating substrate

A vertical cavity GaInAsP/InP surface-emitting laser at 1.3 mu m wavelength is demonstrated with a hemispherical cavity structure. The laser consists of a circular mesa buried (passivated) in polyimide and is made on a semi-insulating InP substrate. CW operation was obtained at 77 K with a threshold current density of 90 kA/cm/sup 2/.<>     

GaInAsP/InP DH laser on semi-insulating InP substrate with terrace structure

GaInAsP/InP DH lasers for the 1.3 ?m region were fabricated through a single LPE process on semi-insulating InP substrates with a terrace structure. The threshold current of the mounted lasers was typically 65 mA under CW operation at room temperature. Light output of 450 mW per facet was achieved at a pulsed injection current of 4.2 A.     

Transparent, highly sensitive GaAs/(GaAl)As photodiode

The letter describes the performance and properties of a transparent GaAs/(GaAl)As photodiode. The diodo can be inserted directly into an optical-fibre transmission line. By this means, it becomes possible to couple out a small amount of the light power guided within the fibre in tho form of an electrical signal.     

Dislocations as the origin of threshold voltage scatterings for GaAs MESFET on LEC-grown semi-insulating GaAs substrate

This paper describes the extended results on the influence of dislocations in liquid-encapsulated Czochralski (LEC) grown semi-insulating GaAs substrates on threshold voltage of GaAs MESFET's. MESFET's located less than about 50 µm from a dislocation exhibit threshold voltage lower than those far from a dislocation and threshold voltage scatters at less than about 30 µm from a dislocation. The scattering is considered briefly from anisotropy of stress field around dislocations. Particular interest is devoted to the electrical properties around dislocations because of their detrimental influence on the FET threshold voltage.     

(GaAl)As/GaAs heterojunction bipolar transistors with graded composition in the base

The first fabrication and high-speed operation of a three-terminal (AlGa)As/GaAs heterojunction bipolar transistor with graded bandgap base is reported. Cutoff frequencies up to 16 GHz have been achieved in devices fabricated from material made by molecular beam epitaxy. This work demonstrates the feasibility of using a graded (AlGa)As base to enhance the speed of heterojunction bipolar transistors.     

High-speed GaAs-(GaAl)As DH LED's with output waveguide structure for optical communications

High-speed GaAs-(GaAl)As DH edge-emitting LED's with an output waveguide structure and a reversed p-n junction for current confinement are described. A cutoff frequency of 115 MHz and a radiance of 1100 W/sr cm²at a diode current of 200 mA have been measured. The output power at the end of a fiber pigtail is about 200 µw with a driving current of 200 mA (core diameter of fiber = 60 µm and numerical aperture NA = 0.2). The coupling efficiency between the diode and a single fiber amounts to 10 percent. Factors affecting both the radiative output and the modulation characteristics are analyzed and discussed.     

Low threshold injection laser in HgCdTe

Narrow-stripe transverse injection lasers in HgCdTe have been successfully fabricated and operated. The double heterostructure of the laser was grown by molecular beam epitaxy on a {111} CdZnTe substrate. The n type base was extrinsically indium doped but other p type layers were only doped by deviation from stoichiometry. Laser emission at 3.4 μm and 3.56 μm was obtained at 78K under pulsed current conditions. Threshold current density as low as 90 A/cm² at 40K was achieved. Over 65K, the threshold current variation with temperature showed a sharp increase due to a drift-current leakage in the structure.     

Voltage comparators implemented with GaAs/(GaAl)As heterojunction bipolar transistors

The first voltage comparators implemented with GaAs/(GaAl)As heterojunction bipolar transistors (HBTs) are reported. The offset voltage of these circuits was found to be generally below 4 mV, and hysteresis below 1 mV; both voltages stayed quite constant over a range of reference voltage of about 1 V. The preliminary circuit yield was high. This work demonstrated the suitability of these HBT comparators for use in a flash A/D convertor of high accuracy (up to 8 bits).