| Summary: | 博士 === 國立交通大學 === 光電工程學系 === 99 === Wide and direct bandgap of GaN-based materials have been attracted much attention for applications such as light emitting diodes (LED) and laser diodes (LD). The high brightness GaN-based light emitting diodes (LEDs) have made it possible to apply in traffic signals, backlight in liquid crystal displays, and solid state lighting. Besides, the blue LD can serve as the light source of high density data storage in high definition digital versatile disk(HD-DVD) which is one of the popular data storage tools. In this thesis, we are focus on the design and fabrication of the optical pumped ultraviolet GaN-based microdisk and square lattice of photonic crystal lasers with 25 pair AlN/AlGaN distributed Bragg reflectors. The distributed Bragg reflector provides a high reflectivity of 85%. We demonstrated a 4.7 μm GaN-based microdisk laser in ultraviolet range without undercut or deeply-etching procedures. Under optical pumping conditions, the lasing action was observed with a low threshold power density of 0.03 kW/cm2. We also characterized the whispering gallery mode(WGM) profiles of the microdisk with finite-different time-domain simulation. About square lattice of photonic crystal lasers, a strong lasing emission was observed from GaN photonic crystals within high reflectivity region of DBR. The photonic crystal bandedge mode was also characterized with three-dimensional plane-wave expansion (PWE) and finite-difference time-domain (FDTD) simulation. And large-area GaN-based photonic quasicrystal (PQC) nanopillars structure was fabricated on an n-GaN layer by using nanoimprint lithography technology.
The regrown InGaN/GaN multiple quantum wells (MQWs) form nano-pyramid structure on the top of PQC nanopillars. Under optical pump condition, a lasing action was observed at ultra-violet wavelength with an ultralow threshold power, and the green color emission from InGaN/GaN MQWs was also achieved simultaneously. We characterized the lasing mode with finite-element method (FEM) simulation. Then a metal-coated GaN nanostripe laser was operated at room temperature. The ultraviolet lasing mode was observed at a wavelength of approximately 370 nm with a low threshold power density of 0.042 kW/cm2. The lasing mode and band diagram of the metal-coated nanostripe were also characterized using FEM simulation. We believed that this lasing mode was a combination of waveguide mode and surface plasmon mode.
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