研究目的
To study the optical regimes and feedback mechanisms in terahertz quantum cascade lasers with dense arrays of active micropillars, and to identify the transition from photonic crystal resonators to subwavelength micropillar arrays forming photonic metamaterials.
研究成果
The study demonstrates the scaling of active pillar arrays for terahertz photonic crystal lasers and subwavelength micropillar array lasers, achieving single-mode emission across the spectral gain bandwidth. However, effective medium devices are limited to high filling factors, and further improvements in planarization materials and waveguide layer smoothness are needed for nanowire-based terahertz lasers.
研究不足
The study is limited by the minimum filling factors and waveguide losses achievable in subwavelength micropillar arrays, which affect the realization of nanowire-based terahertz lasers. Additionally, the mechanical stability of free-standing structures and the roughness of top waveguide layers pose challenges.
1：Experimental Design and Method Selection:
The study involves theoretical and experimental analysis of terahertz quantum cascade lasers with micropillar arrays. Theoretical models include finite element analysis for eigenmodes calculation and effective medium approximation for subwavelength structures. Experimental methods involve fabrication of micropillar arrays and characterization of their emission spectra.
2：Sample Selection and Data Sources:
The study uses GaAs pillars in a BCB host material embedded in a double-metal waveguide. Data is sourced from emission spectra measurements and theoretical calculations.
3：List of Experimental Equipment and Materials:
Equipment includes electron beam lithography for micropillar definition, reactive ion etching for pillar fabrication, and Fourier transform infrared spectrometer for emission spectra measurement. Materials include GaAs, BCB, and Ti/Au metal layers.
4：Experimental Procedures and Operational Workflow:
Fabrication involves defining micropillar arrays, etching the active region, filling spaces with BCB, and depositing top waveguide metal layers. Characterization involves measuring emission spectra at cryogenic temperatures.
5：Data Analysis Methods:
Analysis includes calculating eigenmodes, waveguide losses, and transparency gain using finite element models and comparing with experimental emission spectra.
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