We report on the fabrication of GaSb-based type-I quantum well distributed Bragg reflector (DBR) lasers operating in the 2-μm region. Second-order metallic gratings of chromium are patterned by electron beam lithography. The fabricated DBR lasers emit a single-mode continuous wave at 2.04 μm. The side mode suppression ratio (SMSR) is as high as 35dB with a narrow line-width of 37MHz. The devices show a stable single mode operation with current tuning rate of 0.006nm/mA.
The growth conditions and lasing characteristics of the optically barrier-pumped GaSb - based semiconductor disk laser (SDL) emitting near 2 μm in an external cavity configuration are reported. It is made of a GaSb/AlAsSb Bragg reflector, a Ga<sub>0.8</sub>In<sub>0.2</sub>Sb/GaSb multi quantum-well active region and an Al<sub>0.8</sub>Ga<sub>0.2</sub>As<sub>0.03</sub>Sb<sub>0.97</sub> window layer. Using an intracavity SiC heat spreader, a cw output power in excess of 1.12 W has been achieved at a heat sink temperature of 0 °C.
We report the optimum growth parameters of InAs/AlSb superlattices (SLs) for interband cascade lasers (ICL) grown by the solid-source molecular beam epitaxy(MBE). The InAs/AlSb superlattices samples were grown on GaSb substrate at different temperatures and characterized by high resolution X-ray diffraction (HRXRD), atomic force microscopy (AFM) and photoluminescence (PL). By changing the group-Ⅴ flux ratio during the SLs growth, the InAs/AlSb superlattices matched to GaSb substrate were obtained. Subsequently, the SLs were grown at different growth temperature. By photoluminescence we found the highest PL intensity was obtained when the SLs samples were grown at 458°C and the PL wavelength is at 1730 nm. From 10 × 10 μm<sup>2</sup> AFM image, we found the root mean square (RMS) of the sample grown at 458°C was 1.96 Å which indicates the low surface roughness and god surface morphology.
Here we report the growth method of InGa/GaAs quantum dot (QD) with differnet QD density by manipulating InAs deposition rate from 0.065 ML/s to 0.1 ML/s. Chose the highest density QD as the active region and grow multilayer InAs/GaAs QD with high uniform. Then fabricate a narrow ridge waveguide laser by semiconductor process. The rigid waveguide is 1.8 um high and 5 um wide, and the cavity length is 1mm. The output power of this narrow-rigid laser is 164 mW and central wavelength is 1204.6 nm when the injection current is 0.5 A at 15°C. The threshold current is as low as 35 mA, and threshold current density is 1939 A/cm<sup>2</sup>.
We demonstrated high power semiconductor diode lasers emitting around 2.1 μm with the micro-stripe broad area (MSBA) structure which was proposed to improve the broad area (BA) lasers’ lateral beam quality. 1.28W output power at 7A at continuous wave (CW) operation was achieved from the uncoated MSBA laser. It is shown that the micro-stripe structure would lead to worse threshold current and slope efficiency of the lasers because of the less-pumped lossy regions. However, the MSBA lasers would have better heat dissipation system with proper micro-stripe structure and gain advantages on power performance at high currents.
We report the wavelength tuning of type-II “W” quantum well of interband cascade laser. By changing the thickness of the InAs electron well, the wavelength of the active region is adjusted. We found that the whole 3-4 μm spectra can be realized and the intensity was basically the same by measuring the photoluminescence (PL) of the active region. It showed that the type-II “W” quantum well of interband cascade laser can achieve 3-4 μm range without attenuation. In addition, we calculated the wavelength of quantum well of different InAs thickness by the 8-band k·p method. And we found that the wavelength of the active region varies with the thickness of the InAs electron well, which is consistent with the theory. In addition, the measured wavelength was different from the theoretical wavelength, which may be due to the As incorporation. The incorporation of As into the InGaSb layer will lead to blue shift in the wavelength.
Special processing of rapid thermal annealing on the cavity coating films for 1950 nm wavelength antimonide quantum well Laser diodes are studied. The maximum output power of the laser is greatly improved by RTA process on cavity facet films from around 610mW to above 700mW. The power conversion efficiency is further improved by the simple process by 23.2% than that of the laser coated. And the laser devices become more reliable and have extended service life after the process.
Here we report the solid source molecular beam epitaxy (MBE) growth of high quality of InGaAs/ GaAs quantum dot (QD) structures. A laser device is fabricated by the semiconductor process, including Lithography, Inductively Coupled Plasma (ICP), Plasma Enhanced Chemical Vapor Deposition (PECVD) and Reactive Ion Etching (RIE). The rigid is 100μm wide and cavity is 2000um long. Room temperature continuous-wave (CW) operation with emission wavelength around 1.31μm is presented. Threshold current (I<sub>th</sub>) and threshold current density (J<sub>th</sub>) is 0.3A and 150A/cm<sup>2</sup> at 15°, and output power at I<sub>th</sub>=7A reached as high as 1.079W. We also observe that the spectrum shift from 1315nm to 1333nm when the injection currents increase from 1.5A to 3.5A, and the shift speed is 8.72 nm/A.
The semiconductor epitaxial design and lasing characteristics of an optically barrier-pumped GaSb -based semiconductor disk laser (SDL) emitting at 2.0 μm optimized for resonant optical barrier pumping around 1470 nm are presented. Compared to conventional barrier-pumped devices with pump wavelength of 980nm, the novel barrier-pumped device with the smaller quantum deficit reaches a significantly higher power efficiency, and thus a higher output power at a given pump power, due to the lesser internal heat generation. Using an intracavity SiC heat spreader, a cw output power in excess of 300 mW has been achieved at a heat sink temperature of +15 °C, and still more than 500 mW at +10 °C.
We report on successful fabricating of GaSb-based type-I quantum well distributed Bragg reflector (DBR) lasers emitting at 2080nm. Second-order Bragg gratings of chromium were patterned by electron beam lithography. For 1.5- mm-long laser diode, single mode continuous-wave operation with side mode suppression ratio (SMSR) as high as 30dB is obtained. The line-width of the lasing wave is kept as narrow as 70MHz. The devices show a stable single mode operation with current tuning rate of 0.01nm/mA.
The investigations on GaAs/AlGaAs multiple quantum well self electro-optic effect device (SEED) arrays for optoelectronic smart pixels are reported. The hybrid integration of GaAs/AlGaAs multiple quantum well devices flip-chip bonding directly over 1 micrometers silicon CMOS circuits are demonstrated. The GaAs/AlGaAs multiple quantum well devices are designed for 850 nm operation. The measurement result under applied biases show the good optoelectronic characteristics of elements in SEED arrays. The 4 X 4 optoelectronic crossbar structure consisting of hybrid CMOS- SEED smart pixels have been designed, which could be potentially used in optical interconnects for multiple processors.
We have developed a new MBE growth technique by using low- temperature-Si (LT-Si) or LT-GeSi buffer layers. Even if the Ge fraction up to 90%, the total thickness of fully relaxed Ge<SUB>x</SUB>Si<SUB>1-x</SUB> buffers can be reduced to 1.7 micrometer with dislocation density lower than 5 X 10<SUP>6</SUP> cm<SUP>-2</SUP>. The roughness is no more than 6 nm. According to the analysis of X-ray diffraction, the crystal quality of the top layer is very good, and the strain relaxation is quite inhomogeneous from the beginning of relaxation. By using high resolution cross section TEM, we observed that stacking faults are induced and form the misfit dislocations in the interface of GeSi/LT-Si. We propose that the formation of the stacking faults is due to the aggregation of the large amount of the vacant defects in the LT-Si layer.