Generation of heralded single photons beyond 1100 nm by spontaneous four-wave mixing in a side-stressed femtosecond laser-written waveguide

We demonstrate a monolithically integrable heralded photon source in a femtosecond laser direct written glass waveguide. The generation of photon pairs with a wide wavelength separation requires a concomitant large birefringence in the normal dispersion regime. Here, by incorporation of side-stress tracks, we produce a waveguide with a birefringence of 1.64×10−4 and propagation loss as low as 0.21 dB/cm near 980 nm. We measure photon pairs with 300 nm wavelength separation at an internal generation rate exceeding 5.05×106/s. The second order correlations indicate that the generated photon pairs are in a strongly non-classical regime.