講演情報
[11a-C213-3]Near-Transform-Limited-Picosecond-Pulse Generation in Gain-Switched DFB Lasers with Chirp Compensation and Spectral Filtering
〇Fuyi Cao1, Yihan Qi1, Cong Wang1, Masataka Kobayashi1, Shaoqiang Chen1,2, Hidefumi Akiyama1 (1.ISSP, Univ. of Tokyo, 2.Dept. of Elec. Eng., East China Normal Univ.)
キーワード：
semiconductor、laser、Ultrafast
We investigate short pulse generation and waveform shaping of gain-switched (GS) distributed-feedback (DFB) semiconductor lasers using a time-domain traveling-wave (TDTW) model. The objective is to clarify the chirp characteristics of GS pulses and evaluate simple approaches for generating high-quality ultrashort pulses. A quarter-wave-shifted DFB laser is analyzed under impulsive pumping conditions, and the temporal amplitude and phase of the output field are used to evaluate pulse evolution and chirp dynamics. Linear chirp compensation and spectral filtering are subsequently examined using single-mode fibers (SMFs) and high-pass filters (HPFs).
As the injected carrier density increases, the pulse width of directly generated GS pulses decreases and eventually saturates at approximately 3.6 ps, whereas the spectral width and chirp rate continue to increase. Although the transient chirp exhibits nonlinear behavior, it is dominated by a linear down-chirp component. As a result, chirp compensation using SMFs with optimal length is highly effective, compressing the pulse width to 1.18 ps. Further pulse shortening and waveform purification are achieved by introducing an HPF to suppress low-energy spectral components, resulting in near-transform-limited pulse widths as short as 1.15 ps. Weak trailing structures following the main pulse peak are also partially suppressed by the HPF.
These results demonstrate that the transient chirp in GS-DFB lasers does not fundamentally limit transform-limited-pulse generation. Simple combinations of SMFs and HPFs provide an experimentally accessible route to generating near-transform-limited picosecond pulses from compact semiconductor laser sources.
As the injected carrier density increases, the pulse width of directly generated GS pulses decreases and eventually saturates at approximately 3.6 ps, whereas the spectral width and chirp rate continue to increase. Although the transient chirp exhibits nonlinear behavior, it is dominated by a linear down-chirp component. As a result, chirp compensation using SMFs with optimal length is highly effective, compressing the pulse width to 1.18 ps. Further pulse shortening and waveform purification are achieved by introducing an HPF to suppress low-energy spectral components, resulting in near-transform-limited pulse widths as short as 1.15 ps. Weak trailing structures following the main pulse peak are also partially suppressed by the HPF.
These results demonstrate that the transient chirp in GS-DFB lasers does not fundamentally limit transform-limited-pulse generation. Simple combinations of SMFs and HPFs provide an experimentally accessible route to generating near-transform-limited picosecond pulses from compact semiconductor laser sources.