Entangled photon pairs are an important resource for quantum cryptography schemes that go beyond point-to-point communication. Semiconductor Bragg-reflection waveguides are a promising photon-pair source due to mature fabrication, integrability, large transparency window in the telecom wavelength range, integration capabilities for electro-optical devices as well as a high second-order nonlinear coefficient. To increase performance we improved the fabrication of Bragg-reflection waveguides by employing fixed-beam-moving-stage optical lithography, low pressure and low chlorine concentration etching, and resist reflow. The reduction in sidewall roughness yields a low optical loss coefficient for telecom wavelength light of alpha_reflow = 0.08(6)mm^(-1). Owing to the decreased losses, we achieved a photon pair production rate of 8800(300)(mW*s*mm)^(-1) which is 15-fold higher than in previous samples.
@article{arxiv.2309.00936,
title = {Fabrication of low-loss III-V Bragg-reflection waveguides for parametric down-conversion},
author = {Hannah Thiel and Marita Wagner and Bianca Nardi and Alexander Schlager and Robert J. Chapman and Stefan Frick and Holger Suchomel and Martin Kamp and Sven Höfling and Christian Schneider and Gregor Weihs},
journal= {arXiv preprint arXiv:2309.00936},
year = {2023}
}