Y. H. Zhuang

Submilliampere threshold current pseudomorphic InGaAs/AlGaAs buried-heterostructure quantum well lasers grown by molecular beam epitaxy

We report on low threshold current strained InGaAs/AlGaAs single quantum well lasers grown by molecular beam epitaxy. Broad-area threshold current densities of 114 A/cm2 at 990 nm were measured for 1540-µm-long lasers. Threshold currents of 2.4 mA at 950 nm were obtained for an uncoated buried-heterostructure device with a 2-µm-wide stripe and 425-µm-long cavity. With reflective coatings the best device showed 0.9 mA threshold current (L=225 µm). Preliminary modulation measurements show bandwidths up to 5.5 GHz limited by the detector response.

Submilliamp threshold InGaAs-GaAs strained layer quantum-well laser

Strained-layer InGaAs-GaAs single-quantum-well buried-heterostructure lasers were fabricated by a hybrid beam epitaxy and liquid-phase epitaxy technique. Very low threshold currents, 2.4 mA for an uncoated laser (L=425 mu m) and 0.75 mA for a coated laser (R approximately 0.9, L=198 mu m), were obtained. A 3-dB modulation bandwidth of 7.6 GHz was demonstrated at low bias current (14 mA). Procedures for material preparation and device fabrication are introduced. >

Quantum well superluminescent diode with very wide emission spectrum

Superluminescent diodes (SLDs) employing single and multiple quantum wells were investigated. The diode structure includes a monolithic window and a gain and absorber section. Spectral widths 2–3 times that of conventional SLDs were demonstrated.

Direct measurement of linewidth enhancement factors in quantum well lasers of different quantum well barrier heights

The wavelength dependence of the linewidth enhancement factor (amplitude‐phase coupling factor) α in quantum well lasers of different quantum well barrier heights have been determined from the spontaneous emission spectra and the Fabry–Perot mode wavelength shifts. It is found that the α parameter at lasing wavelength in GaAs/Al0.15Ga0.85As lasers is about twice as large as that in GaAs/Al0.30Ga0.70As lasers. The observation is consistent with the previously observed spectral linewidth behavior in these lasers, which were attributed to the different state filling effects.

Ultralow threshold multiquantum well InGaAs lasers

Ultralow threshold currents have been obtained in multiquantum well strained‐layer InGaAs lasers. A cw threshold current of 1 mA in an uncoated double quantum well laser and a 0.35 mA (pulsed threshold current 0.25 mA) in a coated laser are demonstrated.

Formation of buried high-resistivity layers in InP crystals by MeV nitrogen ion implantation

We have studied the formation of buried high-resistivity layers in InP single crystals by MeV ion implantation. It was found that the implantation of MeV nitrogen ions plus subsequent thermal annealing can generate a deep burried layer with resistivity up to about 10^6 Ω cm in n-type InP crystals. This layer has exhibited implant dose dependence, high thermal stability and reproducibility over a dose range of 5 × 10^(14) − 1 × 10^(16) cm^(−2). The mechanism of insulating layer generation by implantation, based on cross sectional transmission electron microscopy (XTEM) and I–V curve measurements, as well as the application of this technique in device fabrication, will be discussed.

Cavity length dependence of the wavelength of strained‐layer InGaAs/GaAs lasers

The lasing wavelength of a strained‐layer InGaAs/GaAs single quantum well laser has been found to depend strongly on the cavity length. The relationship between the lasing wavelength and the cavity length was established experimentally and a cavity length tuning mechanism for a quantum well laser is thus made possible.

STOCHASTIC RESONANCE IN A SEMICONDUCTOR DISTRIBUTED FEEDBACK LASER

The observation of stochastic resonance in a semiconductor distributed feedback laser is reported. Bistable modal and intensity operation is obtained using the degenerate modes of the grating. Through an observation of longitudinal‐mode switching under current modulation, an enhancement in the signal‐to‐noise ratio of the laser’s output wavelength switching of 22 dB is measured.

Strained single quantum well InGaAs lasers with a threshold current of 0.25 mA

Strained layer single quantum well InGaAs lasers with a record low threshold current of 1 mA for as‐cleaved facets and 0.25 mA with high reflectivity coated facets have been demonstrated. In addition, these lasers display a weak dependence of threshold current, quantum efficiency, and lasing wavelength on cavity length in comparison with those single quantum well lasers previously reported.

A vertical monolithic combination of an InGaAsP/InP laser and a heterojunction bipolar transistor

A DH InGaAsP/InP mesa laser and a DH InGaAsP/InP mass-transport laser were successfully put together with an InGaAsP/InP heterojunction bipolar transistor in a vertical configuration. A laser threshold current as low as 17 mA and an output laser power of over 30 mW were achieved. Base injection current-controlled optical bistability and optical switching were demonstrated.