The dynamic behavior of a monolithic dual-wavelength distributed feedback laser was fully investigated and mapped. The combination of different driving currents for master and slave lasers can generate a wide range of different operational modes, from single mode, period 1 to chaos. Both the optical and microwave spectrum were recorded and analyzed. The detected single mode signal can continuously cover from 15GHz to 50GHz, limited by photodetector bandwidth. The measured optical four-wave-mixing pattern indicates that a 70GHz signal can be generated by this device. By applying rate equation analysis, the important laser parameters can be extracted from the spectrum. The extracted relaxation resonant frequency is found to be 8.96GHz. With the full operational map at hand, the suitable current combination can be applied to the device for proper applications.

The InN dot-like layer was applied in the gallium nitride based material for the purpose of infrared photodetectors (PDs). This InN layer was grown by a low-pressure metal organic chemical vapor deposition technology under different growth temperatures. The X-ray diffraction patterns provide the information of crystal structure and the hexagonal orientation was detected. The Raman shifts and photoluminescence were also used to characterize the quality of InN film. Finally, the fabricated Schottky-type photodetector was tested under a solar simulator and a longwavelength laser (λ = 1550nm). The measurements show a highly linear relation between photo-generated currents and laser powers for the wavelength of 1550 nm. In the photonic detection range suitable for optical fiber communiation, a quantum efficiency of 9.2% can be observed.

A linearly graded band gap design in the intrinsic layer of a p-i-n solar cell is studied numerically. An ideal model using Matlab ® is built and the device performance is calculated using continuity equations and an effective band gap model under various band gap combinations. The power conversion efficiency (PCE) can be as high as 30.21%, while the abrupt junction reference device only exhibits 29.25% under the same parameters. This design is also evaluated using the commercial TCAD software APSYS ® , and the calculations show optimal efficiency enhancements of about 1.14-fold that of the abrupt junction device in an AlAs/GaAs system and 2.05-fold that in an InGaN/GaN system.

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