Heterodyne coherent detection of the electric field temporal trace emitted by frequency-modulated comb lasers

Abstract

Frequency-modulated (FM) combs are produced by mode-locked lasers in which the electric field has a linearly chirped frequency and nearly constant amplitude. This regime of operation occurs naturally in certain laser systems and constitutes a valuable alternative to generate spectra with equidistant modes. Here, we use a low-noise fs-pulse comb as the local oscillator and combine dual comb heterodyne detection with time domain analysis of the multi-heterodyne signal to reveal the temporal trace of both amplitude and phase quadratures of FM comb lasers' electric field. This technique is applied to both a dense and a harmonic mid-infrared free-running quantum cascade laser frequency comb and shows direct evidence of the FM behavior together with the high degree of coherence of these sources. Our results furnish a deeper insight on the origin of the FM combs and pave the way to further improvement and optimization of these devices.

6 pages, 5 figures

References in corpus (10)

• Frequency comb spectroscopy
• Single-mode instability in standing-wave lasers: The quantum cascade laser as a self-pumped parametric oscillator
• Dissipative Kerr solitons in semiconductor ring lasers
• Retrieval of phase relation and emission profile of quantum cascade laser frequency combs
• Femtosecond pulses from a mid-infrared quantum cascade laser
• Self-starting Harmonic Comb Emission in THz Quantum Cascade Lasers
• Synchronization of frequency combs by optical injection
• Highly coherent phase-lock of an 8.1 $\mu$m quantum cascade laser to a turn-key mid-IR frequency comb
• Heterodyne coherent detection of phase modulation in a mid-infrared unipolar device
• Ultra-sensitive heterodyne detection at room temperature in the atmospheric windows

Cited by in corpus (1)

• Non-resonant Optical Injection Locking in Quantum Cascade Laser Frequency Combs