Abstract
Harmonic comb states have proven to be ubiquitous in mid-IR quantum cascade lasers. We report here on robust, pure, self-starting harmonic mode locking in Copper-based double-metal THz quantum cascade lasers. Different harmonic orders can be excited in the same laser cavity depending on the pumping condition, and stable harmonic combs spanning more than 600 GHz at 80 K are reported. Such devices can be RF injected, and the free running coherence is assessed by means of a self-mixing technique performed at 50 GHz. A theoretical model based on Maxwell-Bloch equations including an asymmetry in the gain profile is used to interpret the data.
Highlights
In this Letter, we present results on robust, self-starting harmonic frequency combs in double-metal Cu–Cu THz Quantum Cascade Lasers (QCLs) up to temperatures of 80 K
Harmonic comb states have proven to be ubiquitous in mid-IR quantum cascade lasers
We report here on robust, pure, self-starting harmonic mode locking in Copper-based double-metal THz quantum cascade lasers
Summary
In this Letter, we present results on robust, self-starting harmonic frequency combs in double-metal Cu–Cu THz QCLs up to temperatures of 80 K. We discuss different THz QCLs, which show at multiple bias points self-starting and pure harmonic comb states and report on their experimentally observed differences with respect to mid-IR
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