Impact of higher-order dispersion on frequency-modulated combs.

Frequency-modulated (FM) combs form spontaneously in free-running semiconductor lasers and possess a vast potential for spectroscopic applications. Despite recent progress in obtaining a conclusive theoretical description, experimental FM combs often exhibit non-ideal traits, which prevents their widespread use. Here we explain this by providing a clear theoretical and experimental study of the impact of the higher-order dispersion on FM combs.

Nozaki-Bekki solitons in semiconductor lasers.

Optical frequency-comb sources, which emit perfectly periodic and coherent waveforms of light, have recently rapidly progressed towards chip-scale integrated solutions. Among them, two classes are particularly significant-semiconductor Fabry-Perót lasers and passive ring Kerr microresonators. Here we merge the two technologies in a ring semiconductor laser and demonstrate a paradigm for the formation of free-running solitons, called Nozaki-Bekki solitons.

Active mid-infrared ring resonators.

High-quality optical ring resonators can confine light in a small volume and store it for millions of roundtrips. They have enabled the dramatic size reduction from laboratory scale to chip level of optical filters, modulators, frequency converters, and frequency comb generators in the visible and the near-infrared. The mid-infrared spectral region (3-12 μm), as important as it is for molecular gas sensing and spectroscopy, lags behind in development of integrated photonic components.

High-responsivity operation of quantum cascade detectors at 9 µm.

Quantum cascade detectors (QCDs) are devices operating at zero external bias with a low dark-current. They show linear detection and high saturation intensities, making them suitable candidates for heterodyne detection in long-wave infrared (LWIR) free space optical communication systems. We present an approach to mitigate the performance limitation at long wavelengths, by a comparison of similar single and multi-period QCDs for optimizing their responsivity and noise behaviour.

Synchronization of frequency combs by optical injection.

Optical frequency combs based on semiconductor lasers are a promising technology for monolithic integration of dual-comb spectrometers. However, the stabilization of offset frequency f remains a challenging feat due the lack of octave-spanning spectra. In a dual-comb configuration, the uncorrelated jitter of the offset frequencies leads to a non-periodic signal resulting in broadened beatnotes with a limited signal-to-noise ratio (SNR).