Fabrication and Optical Measurements of Microdisks Embedded with InGaAs Quantum Dots
Date Issued
2007
Date
2007
Author(s)
Chen, Chien-An
DOI
zh-TW
Abstract
Owing to the geometrical symmetry of microdisk (MD) cavities, they support whispering gallery modes (WGMs) in which light circulates around the periphery of the structure and is confined by total internal reflections at both the sidewall and the top and bottom surfaces of the MD. Being cladded symmetrically by the air at both surfaces, light is well confined inside the MD due to the large refractive index difference. With the InGaAs quantum dots (QDs) as the active region in the MD, the much broader gain spectrum allows more resonant WGMs to be observed due to the inhomogeneous broadening of size-dispersed QDs. By e-beam lithography, we defined MDs of 2 μm and 5 μm in radius, respectively.
After carefully applying both dry and wet etching processes, we successfully fabricated both single-layer and double-layer MDs. We performed micro-photoluminescence experiments at both room temperature (RT) and 77K. At RT, we observed radial modes in both sizes of MDs. The mode spacing for 2 μm and 5 μm MDs is 30 nm and 12.7 nm, respectively. As the temperature is reduced to 77K, we observed several WGMs with the mode spacing 9~11nm and 3~4 nm on average for 2 μm and 5 μm MDs, which agree very well with our simulation results of 11.1 nm and 4.4 nm, respectively. Limited by the resolution of the spectrometer, the minimum full width at half maximum (FWHM) of 70 pm was obtained, which corresponds to a high Q-factor of 14000. The real Q-factor will be even larger. By varying the pumping power at low temperature, we observed the lasing behavior in 5-μm MD with the lasing threshold of 394 μW and 417 μW for single and double-layer MDs, respectively.
Subjects
量子點
微碟
共振腔
砷化鎵銦
Microdisks
InGaAs
Quantum Dots
QDs
Resonator
Type
thesis