A photonic integrated circuit for heterogeneous second harmonic generation

TL;DR

This paper introduces a photonic integrated circuit that combines GaAs lasers and frequency doubling waveguides to efficiently generate visible light in a compact, scalable device, advancing integrated nonlinear optical sources.

Contribution

It presents a novel PIC design integrating gain sections with frequency conversion, using thin film lithium niobate and bonded GaAs lasers for visible light generation.

Findings

Successful integration of GaAs lasers with frequency doubling waveguides

Generation of visible light in the 515-595 nm range

Potential for scalable coherent visible light sources

Abstract

Heterogeneous integration of GaAs-based lasers with frequency doubling waveguides presents a clear path to scalable coherent sources in the so-called green gap, yet frequency doubling systems have so far relied on separately manufactured lasers to deliver enough power for second harmonic generation. In this work, we propose a photonic integrated circuit (PIC) which alleviates the performance requirements for integrated frequency doublers. Two gain sections are connected by waveguides, with a frequency converter and a wavelength separator in between. The fundamental light circulates between the gain sections until it is converted and emitted through the wavelength separator. Variants of this separated gain PIC are discussed, and the PIC is implemented with thin film lithium niobate and directly bonded GaAs-based lasers, coupled by on-chip facets and adiabatic tapers, realizing visible light generation in the 515-595 nm range.