研究目的
Demonstrating polarization control in GaN-based micro-cavity lasers using a rigid high-contrast grating reflector.
研究成果
GaN-based microcavity lasers with high reflectance TiO2 HCGs were successfully fabricated and demonstrated under optical pumping at room temperature. The output laser emission was polarized perpendicularly to the HCG, with a small divergence angle of 14°. This demonstrates the feasibility of using robust and easily fabricated TiO2 HCG on the GaN surface for GaN-based light emitters in the wavelength range between green and ultraviolet regimes.
研究不足
The study is limited by the fabrication challenges of creating a free-standing grating surrounded by air with a low refractive index in the III-nitride material system. Additionally, the optical absorption losses in the GaN bulk layers and nonideal HCG (surface roughness, nonvertical sidewalls) in the real laser cavity may affect the quality factor.
1：Experimental Design and Method Selection:
The study involved designing and fabricating GaN microcavity lasers with a TiO2 high-contrast grating (HCG) structure as the output mirror. The HCG was designed to yield high reflectance for TM- or TE-polarized light.
2：Sample Selection and Data Sources:
The samples were GaN-based microcavity structures with a TiO2 HCG reflector. Data was collected through optical pumping and emission measurements.
3：List of Experimental Equipment and Materials:
Equipment included a pulsed laser (Nd:YVO4), a near UV infinity-corrected objective lens, a liquid-nitrogen-cooled charge-coupled device, and a single monochromator. Materials included GaN, TiO2, and SiO2/Ta2O5 DBR.
4：Experimental Procedures and Operational Workflow:
The TiO2 HCG MC was optically excited through the HCG using a pulsed laser. The output emission was collected and analyzed for polarization and divergence.
5：Data Analysis Methods:
The data was analyzed for lasing threshold, polarization degree, and divergence angle using standard optical measurement techniques.
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