Event
【GIR Open Seminar】 Dr. Li Hua / Shanghai Institute of Microsystem and Information Technology, CAS (China)
| Date | 2024.10.16 (15：00 - 16：00) |
|---|---|
| Venue | |
| Google Classroom Code | 25wce2h |
| Speaker | Dr. Li Hua |
| Affiliation | Shanghai Institute of Microsystem and Information Technology, CAS (China) |
| Title | "Broadband terahertz frequency comb and dual-comb operation under microwave injection" ＜Abstract＞ Broadband frequency comb and dual-comb sources are of great importance for high precision applications, e.g., spectroscopy, imaging, communications, etc. Specifically, the dual-comb technique can allow retrieving Fourier spectra without the need of moving interferometric components, thereby offering new possibilities for real-time and high-resolution spectroscopic measurements. In the terahertz (THz) frequency range, broadband quantum cascade lasers (QCLs) are the most powerful chip-scale sources for frequency comb and dual-comb operation. However, the limited gain bandwidth and chromatic dispersion of THz QCLs have constrained the comb-based applications. In this presentation, I will review the broadband THz QCL frequency comb and dual-comb sources by employing microwave injection techniques. For frequency comb operation, it is shown that the resonant microwave injection is a powerful tool to stabilize the repetition frequency and broaden the emission spectrum of the THz QCL combs. Regarding the dual-comb operation, we experimentally implement the microwave injection onto two THz QCL combs and broadband dual-comb operation is achieved. In the dual-comb experiment, a THz QCL structure with a stacked active region which shows a calculated gain bandwidth spanning from 3.35 to 3.83 THz is used. The measured lasing bandwidth in free-running is broadened from 250 GHz (single active region) to 470 GHz (stacked active region) which agrees well with the simulation. Although broad THz emission can be obtained at relatively high drive currents, the laser normally demonstrates chaotic emission behavior due to the high phase noise introduced by the strong electrical pumping. Herein, by employing a microwave injection technique, we observe a clear transition from chaos to broadband dual-comb operation in the THz QCL with the stacked active region. The measured optical bandwidth is ∼400 GHz, which reaches 73% of the lasing bandwidth of the THz QCL (550 GHz under microwave injection). The mechanism of the phase noise compression induced by the external microwave injection can be associated with the modulation of group velocity dispersion and phase matching in the THz QCL, which further enhances the four-wave mixing locking effect for the broadband dual-comb operation. |
| Language | English |
| Intended for | Everyone is welcome to join. |
| Co-Organized by | Institute of Global Innovation Research "LIFE SCIENCE" Umebayashi Team Excellent Leader Development for Super Smart Society by New Industry Creation and Diversity |
| Contact | Institute of Global Innovation Research, Institute of Engineering Assoc. Prof. Ya Zhang Email: zhangya (at) go.tuat.ac.jp |
| Remarks | This seminar will only be held face-to-face. |
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