Phys.org March 28, 2023
Optical parametric oscillators are widely used to generate coherent light at frequencies not accessible by conventional laser gain. However, chip-based parametric oscillators operating in the visible spectrum have suffered from pump-to-signal conversion efficiencies typically less than 0.1%. A team of researchers in the US (NIST, University of Maryland) demonstrated efficient optical parametric oscillators based on silicon nitride photonics that address frequencies between 260 and 510 THz. Pumping silicon nitride microrings near 385 THz yielded monochromatic signal and idler waves with unprecedented output powers in this wavelength range. They estimated on-chip output powers (separately for the signal and idler) between 1 and 5 mW and conversion efficiencies reaching ≈15% . Underlying this improved performance was their development of pulley waveguides for broadband near-critical coupling, which exploited a fundamental connection between the waveguide-resonator coupling rate and conversion efficiency. They found that mode competition reduces conversion efficiency at high pump powers, thereby constraining the maximum realizable output power. According to the researchers their work proved that optical parametric oscillators built with integrated photonics could produce useful amounts of visible laser light with high efficiency… read more. Open Access TECHNICAL ARTICLE  1 ,  2
Achieving high conversion efficiency (CE) across a wide spectral band… Credit: APL Photonics, Volume 7, Issue 12, 10.1063/5.0117691Â