Spectral dynamics of picosecond gain-switched pulses from nitride-based vertical-cavity surface-emitting lasers
Chen, Shaoqiang; Ito, Takashi; Asahara, Akifumi; Yoshita, Masahiro; Liu, Wenjie; Zhang, Jiangyong; Zhang, Baoping; Suemoto, Tohru; Akiyama, Hidefumi; 刘文杰; 张江勇; 张保平
Short pulses generated from low-cost semiconductor lasers by a simple gain-switching technique have attracted enormous attention because of their potential usage in wide applications. Therein, reducing the durations of gain-switched pulses is a key technical point for promoting their applications. Therefore, understanding the dynamic characteristics of gain-switched pulses is highly desirable. Herein, we used streak camera to investigate the time-and spectral-resolved lasing characteristics of gain-switched pulses from optically pumped InGaN single-mode vertical-cavity surface-emitting lasers. We found that fast initial components with ultra-short durations far below our temporal resolution of 5.5 ps emerged on short-wavelength sides, while the entire pulses were down-chirped, resulting in the simultaneous broadening of the spectrum and pulse width. The measured chirp characteristics were quantitatively explained using a single-mode rate-equation model, combined with carrier-density-dependent gain and index models. The observed universal fast short-wavelength components can be useful in generating even shorter pulses from gain-switched semiconductor lasers.
MEXT KAKENHI [20104004, 20104006]; JSPS KAKENHI [23360135]; Photon Frontier Network Program of MEXT; JST-CREST
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