Premium
Controlling Quantum Cascade Laser Optical Frequency Combs through Microwave Injection
Author(s) -
Schneider Barbara,
Kapsalidis Filippos,
Bertrand Mathieu,
Singleton Matthew,
Hillbrand Johannes,
Beck Mattias,
Faist Jérôme
Publication year - 2021
Publication title -
laser and photonics reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.778
H-Index - 116
eISSN - 1863-8899
pISSN - 1863-8880
DOI - 10.1002/lpor.202100242
Subject(s) - physics , optics , bandwidth (computing) , laser , quantum cascade laser , frequency comb , frequency modulation , cascade , modulation (music) , coherence (philosophical gambling strategy) , microwave , mode locking , telecommunications , chemistry , chromatography , quantum mechanics , computer science , acoustics
Abstract In this work, control over the precise state emitted by quantum cascade laser frequency combs through strong radio‐frequency current modulation close to their repetition frequency is demonstrated. In particular, broadening of the spectrum from about 20 cm −1 to an average bandwidth of 60 cm −1 can be achieved throughout most of the current dynamical range while preserving the coherence, as measured by shifted wave interference Fourier transform spectroscopy (SWIFTS). The required modulation frequency to achieve this broadening is red‐shifted compared to the free‐running beatnote frequency at increasing modulation powers starting from 25 dBm, whereas the range where it occurs narrows. Outside of this maximum‐bandwidth range, the spectral bandwidth of the laser output is gradually reduced and the new center frequency is red‐ or blue‐shifted, directly dependent on the detuning of the modulation frequency. By switching between two modulation frequencies detuned symmetrically with respect to the free‐running beatnote, two multiplexed spectral regions with negligible overlap from the same device at rates of at least 20 kHz can be generated. In the time‐domain, with both SWIFTS and interferometric autocorrelation (IAC) measurements a transition from quasi‐continuous output to long‐pulsed ( τ p ≈ 55 ps) output is shown by ramping up the injection power to 35 dBm.