In this work we show Frequency Comb (FC) and short pulsed operation of mid-infrared Interband Cascade Lasers (ICLs) in a single long section. This is through the use of an adapted ultrafast Quantum Well Infrared Photodetectors (QWIPs), and correlating the microwave beatnotes with high resolution spectra of the ICL. In particular, we will show active mode-locking (ML) of single-section ICL that does not require RF optimisation of the ICL device and highlight its temporal characteristics using Shifted Wave Infrared Fourier Transform Spectroscopy (SWIFTS) analysis to reconstruct the intensity in the time domain.

We report on a multi-GHz repetition rate, femtosecond fiber laser operating in the burst mode, achieved by nonlinearly shaping and amplifying a phase-only modulated electro-optic comb at 1.03 μm. The system delivers an average power of 1.2 W with pulses compressible down to sub 100 fs.

Electro-optic frequency-comb is an interesting method for comb generation as it offers the possibility to electrically tune the generated frequency-comb by simply tuning the electrical signal applied on the modulator. Integrated modulators operating in a wide spectral range in the mid-IR have been demonstrated recently, relying on free carrier plasma dispersion effect in a Schottky diode embedded in a Ge-rich graded SiGe waveguide. Such integrated mid-infrared modulators have been used to generate electro-optic frequency-combs with more than 200 lines around the 8 µm wavelength optical carrier.

We present a planarized waveguide cavity with an integrated broadband output coupler that improves both the output power and far-field properties of THz quantum cascade laser frequency combs. The laser mirror reflectivity can be tuned by the shape of the end facet, which is obtained with an efficient inverse design algorithm, where the structure is iteratively updated to match the desired figure of merit. Surface emission is achieved with a broadband patch-array antenna, and all the components have been optimized for octave-spanning emission spectra (2-4 THz). Experimentally, we demonstrate a broadband surface-emitting THz quantum cascade laser frequency comb with optical bandwidths of up to 800 GHz, surface emission into a narrow beam with divergence below (20° x 20°) and a peak power of 13 mW.

This paper reports the development of a dual-comb spectroscopy system based on gain-switched single-mode laser diodes emitting at 1572 nm. The switching is performed by a train of short electrical pulses at a repetition rate of 100 MHz while the lasers are subjected to external optical injection. Under these conditions, broad and flat optical frequency combs (OFC) are generated, showing 100 tones within 10 dB and a line spacing fixed by the repetition rate of the switching pulses. The dual-comb generated by the interference of two such combs with slightly different line spacing, is used for measuring the absorption line of CO2 at 1572.02 nm. The transmission spectrum is analyzed and fitted to a Voigt profile. A deviation of 3% in the residuals of the fitting is obtained, denoting the high spectral performance of the spectroscopy system.

While the opportunity to perform fast and broadband spectroscopy in the Mid-IR portion of the electromagnetic spectrum is very appealing, it requires the use of compatible light-sources. Here, we strongly modulate a Mid-Infrared Quantum Cascade Laser at a frequency in the RF domain, which is low compared to the natural repetition frequency of the device. In this way, we demonstrate that it is possible to obtain an emission bandwidth of up to 250𝐜𝐦−𝟏. Finally, we employ it as a light source in an FTIR based on a rotational delay line, performing fast and broadband FTIR spectroscopy.