Open AccessSuppression of substrate mode in GaN-based green laser diodes
Author(s) -
Lijin Jiang,
Jianping Liu,
Liqun Zhang,
Bocang Qiu,
Lei Hu,
Deyao Li,
Siyi Huang,
Wei Zhou,
Masao Ikeda,
Hui Yang
Publication year - 2020
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.389880
Subject(s) - materials science , cladding (metalworking) , optics , refractive index , laser , optoelectronics , diode , substrate (aquarium) , semiconductor laser theory , composite material , oceanography , physics , geology
Parasitic substrate mode readily appears in GaN-based laser diodes (LDs) because of insufficient optical confinement, especially for green LDs. Substrate modes affect the behavior of a LD severely, including the laser beam quality, the optical output power, the longitudinal mode stability, and the maximum modulation speed. In this article, systematic studies on the n-cladding layer (CL) design to suppress the substrate mode of GaN-based green LDs were carried out. We established a contour map to describe the relationship between the optical confinement (determined by the thickness and the refractive index) of n-CL and the substrate mode intensity by simulating the near-field pattern and the far-field pattern. We found that it was difficult to obtain the Gaussian-shape far-field pattern using AlGaN as a cladding layer due to the appearance of cracks induced by tensile strain. However, this can be realized by introducing quaternary AlInGaN as a cladding layer since refractive index and strain can be tuned separately for quaternary alloy.