Robust hybrid laser linewidth reduction using Si<sub>3</sub>N<sub>4</sub>-based subwavelength hole defect assisted microring reflector
Jiachen Li, Baoyu Zhang, Sigang Yang, Hongwei Chen, Minghua Chen
Abstract
We demonstrate a hybrid laser with a low intrinsic linewidth of 34.2 Hz and a high fiber-coupled output power of 11.7 dBm, by coupling a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m1"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>Si</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>3</mml:mn> </mml:mrow> </mml:msub> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">N</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>4</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> -based subwavelength hole defect assisted microring reflector (SHDA-MRR) to a commercially available distributed feedback semiconductor laser. The proposed SHDA-MRR structure features an accurately controlled reflection response, with the manipulated modal coupling between two degenerate counterpropagating modes induced by a subwavelength hole defect embedded in the microring waveguide. With further joint optimization of cavity parameters, this <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" id="m2"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>Si</mml:mi> </mml:mrow> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">N</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:mrow> </mml:math> SHDA-MRR structure is expected to reduce the laser intrinsic linewidth to a sub-hertz level. This work explores a low-cost and robust linewidth reduction scheme for the applications of high-speed coherent optical communications systems and high-resolution optical metrology.