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Ultrafast response of harmonic modelocked THz lasers
Feihu Wang1, Valentino Pistore1, Michael Riesch2
1Laboratoire de Physique de l'Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France.
Light, Science & Applications
|April 8, 2020
Summary
Researchers demonstrate harmonic mode-locking in terahertz quantum cascade lasers (QCLs) for the first time. This breakthrough enables efficient generation of terahertz pulses and frequency combs, paving the way for advanced THz applications.
Area of Science:
- Optics and Photonics
- Semiconductor Lasers
- Terahertz Technology
Background:
- Fundamental mode-locking is established for generating terahertz (THz) pulses and frequency combs using quantum cascade lasers (QCLs).
- Harmonic mode-locking, generating multiple pulses per round trip, has not been demonstrated in THz QCLs.
Purpose of the Study:
- To demonstrate harmonic injection and mode-locking in THz QCLs.
- To explore the generation of harmonic electrical beatnotes and their translation to harmonic pulse generation.
- To investigate self-starting harmonic emission in THz QCLs.
Main Methods:
- Utilized time-resolved THz techniques to study harmonic injection and mode-locking.
- Employed active modulation at harmonics of the cavity's round-trip frequency.
- Conducted time-resolved simulations to analyze gain and loss dynamics.
Main Results:
- Successfully demonstrated harmonic injection and mode-locking in THz QCLs for the first time.
- Generated and injection-locked harmonic electrical beatnotes, leading to harmonic pulse generation.
- Observed self-starting harmonic emission up to the 15th harmonic without external modulation.
Conclusions:
- The study establishes harmonic mode-locking in THz QCLs, a significant advancement over fundamental mode-locking.
- Results highlight the crucial role of both electronic and photonic properties of QCLs.
- Opens prospects for passive harmonic mode-locking, THz pulse generation, and low-noise microwave generation.
