INSPIRE results presented at Photonics West 2024: Micro-transfer printed III-V on silicon nitride narrow-linewidth laser with extended frequency chirp capability for distributed acoustic sensing (DAS) measurements

At Photonics West 2024, Guénolé Dandé presented recent achievement of INSPIRE project: experimental results of OFDR distributed fiber sensing obtained with micro-transfer printed laser.
INSPIRE consortium fabricated hybrid tunable laser based on the micro-transfer printing of a pre-fabricated InP gain section on the IMEC low-loss silicon nitride platform.

The laser incorporates a dual-ring Vernier frequency selective mirror, with a loaded Q-factor of 46k, and delivers -3dB optical power (in fiber) with a Lorentzian linewidth of 3 kHz. At such Q-factor, by solely modulating the SOA drive current, the frequency chirp amplitude of the laser is limited by mode hopping at 4-5 GHz, which is still insufficient for sub-cm DAS resolution. To overcome this issue we simultaneously modulated the rings of the Vernier filter through thermo-optic tuning, and obtained a FM chirp amplitude of 20 GHz at 1kHz repetition rate, with limited phase noise penalty. Thales showed DAS measurement with this laser, concluding that INSPIRE laser overperform all lasers in terms of spatial resolution.

Tunable lasers and photonic integrated circuits are a promising technology to provide compact and high performance solutions for coherent remote sensing applications such as Lidar, and distributed acoustic fiber sensing (DAS). INSPIRE project enables such applications by establishing world´s first PIC platform capable of hosting all optical functions while remaining scalable for mass production.