Broadband indistinguishability from bright parametric downconversion in a semiconductor waveguide

T Günthner,K Laiho,S Höfling,M Kamp,C Schneider,G Weihs,B Pressl,J Geßler

doi:10.1088/2040-8978/17/12/125201

Abstract

Parametric downconversion (PDC) in semiconductor Bragg-reflection waveguides (BRW) is routinely exploited for photon-pair generation in the telecommunication range. Contrary to many conventional PDC sources, BRWs offer possibilities to create spectrally broadband but nevertheless indistinguishable photon pairs in orthogonal polarizations that simultaneously incorporate high frequency entanglement. We explore the characteristics of co-propagating twin beams created in a type-II ridge BRW. Our PDC source is bright and efficient, serving as a benchmark of its performance and justifies its exploitation for further use in quantum photonics. We then examine the coalescence of the twin beams and investigate the effect of their inevitable multi-photon contributions on the observed photon bunching. Our results show that BRWs have a great potential for producing broadband indistinguishable photon pairs as well as multi-photon states.

Highlights

Versatile quantum light sources are needed for a variety of quantum communication tasks, and we would like to develop them for the telecommunication wavelengths
We further examined the coalescence between the twin beams filtered to a few tens of nanometers bandwidth in order to assess their indistinguishability
The visibility of the measured fringes is diminished by the multi-photon contributions of signal and idler, but we can extract a high degree of indistinguishability, which is quantified by their spectral overlap

Summary

Introduction

Versatile quantum light sources are needed for a variety of quantum communication tasks, and we would like to develop them for the telecommunication wavelengths. The state-ofthe-art BRW sources provide high entanglement in the spectral degree of freedom [30,31,32] They offer broadband spectral indistinguishability for signal and idler that are created in orthogonal polarizations. The former is desired in applications requiring multimode PDC characteristics—or higher dimensional states [33, 34], whereas the latter is a building block for many quantum optical networks that usually base on photon interference [35,36,37]. Our results show that BRWs are bright and efficient photon sources

Sample design and experiment

Source efficiency and brightness

Coalescence of signal and idler

Findings

Conclusion