Mid-infrared photonic integrated platform on III-V semiconductors

Photonic Integrated Circuits (PICs) operating in the mid-IR represent a rapidly developing field. The goal is to fill the technological gap with respect to the very well developed visible and near-IR PICs, thus enlarging the types of chip-integrated mid-IR photonic devices in view of applications. Recent developments on on low-loss passive waveguides on III-V semiconductor platforms are presented, optimized to operate in both the mid-IR atmospheric transparent windows (3-5 and 8-12 µm). We report on two material systems: GaAs/Al0.5Ga0.5As waveguides grown on GaAs substrate and In0.53Ga0.47As/InP waveguides grown on InP substrate. Different approaches have been investigated for the fabrication: ICP-RIE (in view of developing integrated racetrack resonators) and wet etching (to gauge the minimum loss value). The measurements, in TE and TM polarizations are based on the Fabry-Perot approach using a DFB laser at λ=8.5 µm and λ=4.6 µm. We will discuss how to further reduce the losses (0.1cm^-1 or less) and how to leverage on such low losses to develop two separate applications: ultra-high Q-factor resonators for Kerr comb generation, and integrated ultra-fast mid-IR modulators.