GaAs-chip-based mid-infrared supercontinuum generation

The mid-infrared spectral region opens up new possibilities for applications such as molecular spectroscopy with high spatial and frequency resolution.For example,the mid-infrared light provided by synchrotron sources has helped for early diagnosis of several pathologies.However,alternative light sources at the table-top scale would enable better access to these state-of-the-art characterizations,eventually speeding up research in biology and medicine.Midinfrared supercontinuum generation in highly nonlinear waveguides pumped by compact fiber lasers represents an appealing alternative to synchrotrons.Here,we introduce orientation-patterned gallium arsenide waveguides as a new versatile platform for mid-infrared supercontinuum generation.Waveguides and fiber-based pump lasers are optimized in tandem to allow for the group velocities of the signal and the idler waves to match near the degeneracy point.This configuration exacerbates supercontinuum generation from 4 to 9μm when waveguides are pumped at 2750 nm with few-nanojoule energy pulses.The brightness of the novel mid-infrared source exceeds that of the thirdgeneration synchrotron source by a factor of 20.We also show that the nonlinear dynamics is strongly influenced by the choice of waveguide and laser parameters,thus offering an additional degree of freedom in tailoring the spectral profile of the generated light.Such an approach then opens new paths for high-brightness mid-infrared laser sources development for high-resolution spectroscopy and imaging.Furthermore,thanks to the excellent mechanical and thermal properties of the waveguide material,further power scaling seems feasible,allowing for the generation of watt-level ultra-broad frequency combs in the mid-infrared.

Broadband supercontinuum generation in nitrogen-rich silicon nitride waveguides using a 300 mm industrial platform

We report supercontinuum generation in nitrogen-rich(N-rich)silicon nitride waveguides fabricated through back-end complementary-metal-oxide-semiconductor(CMOS)-compatible processes on a 300 mm platform.By pumping in the anomalous dispersion regime at a wavelength of 1200 nm,two-octave spanning spectra covering the visible and near-infrared ranges,including the O band,were obtained.Numerical calculations showed that the nonlinear index of N-rich silicon nitride is within the same order of magnitude as that of stoichiometric silicon nitride,despite the lower silicon content.N-rich silicon nitride then appears to be a promising candidate for nonlinear devices compatible with back-end CMOS processes.

Laser sources for microwave to millimeter-wave applications [Invited]

We present several laser sources dedicated to advanced microwave photonic applications.A quantum-dash mode-locked laser delivering a high-power,ultra-stable pulse train is first described.We measure a linewidth below 300 kHz at a 4.3 GHz repetition rate for an output power above 300 mW and a pulse duration of 1.1 ps after compression,making this source ideal for microwave signal sampling applications.A widely tunable(5–110 GHz),monolithic millimeter-wave transceiver based on the integration of two semiconductor distributed feedback lasers,four amplifiers,and two high-speed uni-traveling carrier photodiodes is then presented,together with its application to the wireless transmission of data at 200 Mb∕s.A frequency-agile laser source dedicated to microwave signal processing is then described.It delivers arbitrary frequency sweeps over 20 GHz with high precision and high speed(above 400 GHz∕ms).Finally,we report on a low-noise(below 1 kHz linewidth),solid-state,dual-frequency laser source.It allows independent tuning of the two frequencies in the perspective of the implementation of a tunable optoelectronic oscillator based on a high-Q optical resonator.