M. A. Chin

Subpicosecond monolithic colliding‐pulse mode‐locked multiple quantum well lasers

Ultrafast subpicosecond optical pulse generation is achieved by passive colliding‐pulse mode locking of monolithic multiple quantum well InGaAsP semiconductor lasers. Transform‐limited optical pulses with durations of 1.1, 0.83, 1.0, and 0.64 ps are achieved at repetition rates of 40, 80, 160, and 350 GHz, respectively, without using any external ac sources.

Transform‐limited 1.4 ps optical pulses from a monolithic colliding‐pulse mode‐locked quantum well laser

We report the generation of short optical pulses from novel monolithic colliding‐pulse mode‐locked quantum well lasers. Transform‐limited pulses with durations of 1.4 ps at a repetition rate of 32.6 GHz have been achieved, with nearly 100% intensity modulation depth and a peak optical power of 10 mW. This is the shortest transform‐limited pulse directly generated from monolithic mode‐locked lasers (time‐bandwidth product =0.3).

A periodic index separate confinement heterostructure quantum well laser

A novel edge‐emitting periodic index separate confinement heterostructure (PINSCH) semiconductor quantum well laser is proposed and demonstrated for the first time. Periodic semiconductor multilayers are used as optical confinement layers to simultaneously reduce the transverse beam divergence and increase the maximum output power. Self‐aligned ridge‐waveguide InGaAs/GaAs/AlGaAs PINSCH quantum well lasers emitting at 980 nm are fabricated. The 5×750 μm device has far‐field angles of 10° by 20°, a threshold current of 45 mA, an external differential quantum efficiency of 1.15 mW/mA (90%), and an output power exceeding 620 mW, all measured at room temperature under CW operation. A record high fiber coupling efficiency of 51% has been achieved with a lensed fiber of 5 μm core diameter.

Self‐aligned InGaAs/GaAs/InGaP quantum well lasers prepared by gas‐source molecular beam epitaxy with two growth steps

Index‐guided self‐aligned InGaAs/GaAs/InGaP quantum well lasers are fabricated by gas‐source molecular beam epitaxy in two growth sequences on a GaAs substrate for the first time. The use of aluminum‐free InGaP as cladding layers permits regrowth steps without the problem with the oxidation of aluminum alloys. A patterned n‐InGaP current confinement layer is used to provide index guiding as well as current blocking. Preliminary results from coated 2.5‐μm‐wide and 508‐μm‐long devices show a room temperature continuous wave lasing threshold current of 12 mA with an external differential quantum efficiency of 0.68 mW/mA and a characteristic temperature of 130 K from 30 to 75 °C.

InGaAs/GaAs/InGaP multiple-quantum-well lasers prepared by gas-source molecular beam epitaxy

We report on the first room‐temperature operation of aluminum‐free In0.2Ga0.8As/GaAs/ In0.49Ga0.51P multiple‐quantum‐well lasers grown by gas‐source molecular beam epitaxy. These lasers have low threshold current density Jth of 177 A/cm2, high internal quantum efficiency of 91%, and low internal waveguide loss of 9.1 cm−1. The characteristic temperature T0 is 150 K, which is the highest value ever reported. These results demonstrate that gas‐source molecular beam epitaxy is suitable for growing high‐quality In0.2Ga0.8As/GaAs/In0.49Ga0.51P lasers.

High-power 980-nm AlGaAs/InGaAs strained quantum-well laser grown by OMVPE

High-power lattice-strained AlGaAs/InGaAs graded index separate-confinement heterostructure (GRINSCH) quantum-well lasers emitting at a 980-nm wavelength have been grown by organometallic vapor phase epitaxy (OMVPE) and fabricated with a self-aligned ridge-waveguide structure. Using a 3- mu m-wide and 750- mu m-long AR-HR coated laser, 30 mV of optical power was coupled into optical fibers with 28.6% efficiency. A dominating single-lobe far-field radiation pattern was obtained from a wedge-shaped ridge-waveguide laser for output power as high as 240 mW with a maximum output power of 310 mW.<<ETX>>

Multicolor single-wavelength sources generated by a monolithic colliding pulse mode-locked quantum well laser

The authors report on the separation of single longitudinal modes from the mode-locked program spectrum of a 300-GHz monolithic colliding pulse mode-locked (CPM) semiconductor quantum-well laser. Experimentally, the selected longitudinal mode shows a 10-dB reduction of low-frequency relative intensity noise compared to that of the selected mode from the same laser in continuous-wave (CW) lasing conditions. The strong phase coherence among the passively mode-locked longitudinal modes reduces the partition noise of the unlocked CW laser.<<ETX>>

Direct determination of symmetry of Cr ions in semi‐insulating GaAs substrates through anisotropic ballistic‐phonon propagation and attenuation

We report ballistic phonon experiments in semi‐insulating GaAs as a function of polarization and propagation direction and of the concentration of chromium in the crystal. The data provide direct evidence for a tetragonally distorted site symmetry of the Cr ions and a ground‐state splitting at ∼14 K.

High temperature, high power InGaAs/GaAs quantum-well lasers with lattice-matched InGaP cladding layers

The authors report the high-temperature and high-power operation of strained-layer InGaAs/GaAs quantum well lasers with lattice-matched InGaP cladding layers grown by gas-source molecular beam epitaxy. Self-aligned ridge waveguide lasers of 3- mu m width were fabricated. These lasers have low threshold currents (7 mA for 250- mu m-long cavity and 12 mA for 500- mu m-long cavity), high external quantum efficiencies (0.9 mW/mA), and high peak powers (160 mW for 3- mu m-wide lasers and 285 mW for 5- mu m-wide laser) at room temperature under continuous wave (CW) conditions. The CW operating temperature of 185 degrees C is the highest ever reported for InGaAs/GaAs/InGaP quantum well lasers, and is comparable to the best result (200 degrees C) reported for InGaAs/GaAs/AlGaAs lasers.<<ETX>>

Chemical Beam Epitaxy of GalnP on GaAs(l 00) Substrates and its Application to 0.98/spl mu/m Lasers

Abstract We present results on the growth, doping, and application to lasers of GaInP on GaAs(100) substrates using chemical beam epitaxy (CBE). The growth studies were performed in the substrate temperature range of 490–555°C. We were able to obtain lattice-matching with good surface morphology over the entire substrate range investigated. For a fixed triethylgallium (TEGa) flow, a sharp increase in the trimethylindium (TMIn) flow required to obtain lattice-matching for T sub above 520°C is observed. This can be attributed to an increase in GaP growth rate and a decrease in InP growth rate due to desorption of TMIn species. The p-type and n-type doping of Ga 0.51 In 0.49 P was investigated using diethylzinc (DEZn) and hydrogen sulfide (H 2 S), respectively. It was found that low substrate temperature (≲ 510°C) was necessary to obtain high p-type doping. Separate confinement heterostructure (SCH) lasers with strained In 0.2 Ga 0.8 As/GaAs multiple-quantum-well (MQW) active layers and Ga 0.51 In 0.49 P cladding layers for operation at 0.98 μm were grown. Broad-area lasers show extremely low threshold current densities, J th , of 70 A/cm 2 . Ridge waveguide lasers with 4 μm stripe width have a threshold of 7.8 mA and gave linear CW output powers upto 100 mW. High external quantum efficiency of 0.9 mW/mA and a very low internal waveguide loss of 2.5 cm -1 were obtained from these lasers.