Date of Award
5-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Electrical and Computer Engineering (Holcomb Dept. of)
Committee Chair/Advisor
Dr. Lin Zhu
Committee Member
Dr. Hai Xiao
Committee Member
Dr. Judson D. Ryckman
Committee Member
Dr. Lianfeng Zhao
Abstract
This thesis presents the comprehensive design, fabrication, and demonstration of advanced high-power, high-efficiency single-mode semiconductor lasers operating at a wavelength of 9xxnm. We begin with the design of the laser epitaxial structure, serving as the cornerstone for achieving high-power high-efficiency lasers. Our methodology integrates a semi-analytical calculation model, which accounts for Longitudinal Spatial Hole Burning (LSHB) and Two-Photon Absorption (TPA) effects, facilitating a thorough exploration of how design parameters influence output power and conversion efficiency. This approach offers an effective and time-efficient epitaxial structure optimization strategy compared to conventional full 3D simulation models.
Subsequently, we demonstrate high-power, high-efficiency ridge waveguide (RW) lasers leveraging the optimized epitaxial structure. The RW lasers, with ridge width of 7μm and cavity length of 4mm, exhibit kink-free output and near-Gaussian far-field profiles with the maximum power outputs surpassing 1.6W. Notably, their efficiency demonstrates minimal decline with increasing current, maintaining a remarkable efficiency of 60.2% at 1.52W. Additionally, we introduce narrower RW lasers fabricated with an optimized epitaxial structure featuring reduced aluminum content in the p-cladding layer. The RW lasers, with ridge width of 5μm and cavity length of 5mm, exhibit kink-free near diffraction limit single-mode laser output up to 1W, accompanied by a high efficiency of 59.3%.
To achieve single-transverse-mode laser output in wider emission aperture for higher maximum achievable output power, we propose the triple ridge waveguide (TRW) laser structure, utilizing the principle of unbroken supersymmetry (SUSY). This innovative design incorporates lossy auxiliary waveguides to effectively suppress unwanted higher-order modes within the laser cavity. By precisely engineering the structural parameters of the TRW, we achieve significant modal discrimination, ensuring stable single-mode lasing. Experimental results demonstrate near-diffraction-limited output in the proposed TRW laser, validating the efficacy of our mode filtering mechanism. To further enhance mode discrimination in practical applications, we propose the introduction of trapezoidal deep-etched trenches in the auxiliary waveguide. These trenches serve to convert guided modes into leaky modes, effectively increasing propagation loss for undesired higher-order modes. This enhancement facilitates more stable single-mode operation, particularly at high power outputs.
Moreover, in response to the increasing demand for highly coherent, low phase noise on-chip laser beams within integrated optics, we employ the self-injection locking technique to combine our demonstrated high-power ridge waveguide Fabry–Pérot (FP) lasers with silicon nitride photonic integrated circuits (PICs). Our experiments yield a stable narrow-linewidth single-frequency laser output with a fiber-coupled power of up to 3.5mW, accompanied by an impressive SMSR exceeding 48dB and an intrinsic linewidth smaller than 25kHz.
Our research provides valuable insights into the advancement of high-power, high-efficiency, single-mode semiconductor lasers, with promising applications across the field of photonics and telecommunications.
Recommended Citation
Zhao, Xiaolei, "Design, Fabrication, and Characterization of Advanced High-power Single-mode 9xxnm Semiconductor Lasers" (2024). All Dissertations. 3601.
https://tigerprints.clemson.edu/all_dissertations/3601
Author ORCID Identifier
https://orcid.org/0000-0003-0676-5840