Temperature insensitive type II quasi-phasematched spontaneous parametric downconversion

Abstract

The temperature dependence of the refractive indices of potassium titanyl phosphate (KTP) is shown to enable quasi-phasematched type II spontaneous parametric downconversion (SPDC) with low temperature sensitivity. Calculations show the effect to be maximized for emission of photons at around 1165 nm, as well as producing similar plateaus for wavelengths throughout the telecommunications bands. We experimentally demonstrate the effect, observing temperature-insensitive degenerate emission between 20 °C and 100 °C at 1327 nm, within the telecommunications O band. This result has practical implications for the development of entangled photon sources for resource-constrained environments, and we demonstrate a simple polarization entangled source as a proof of concept.