Proposal for an Integrated Raman-free Correlated Photon Source

We propose a dual-pump third-order nonlinear scheme for producing pairs of correlated photons that is less susceptible to Raman noise than typical spontaneous four wave mixing methods (SFWM). Beginning with the full multimode Hamiltonian we derive a general expression for the joint spectral amplitude, from which the probability of producing a pair of photons can be calculated. As an example, we demonstrate that a probability of 0.028 pairs per pulse can be achieved in an appropriately designed fused silica microfiber. As compared with single pump SFWM in standard fiber, we calculate that our process shows significant suppression of the spontaneous Raman scattering and an improvement in the signal to noise ratio.Comment: 7 pages, 3 figures (two containing 2 subfigures

Tuneable quantum interference in a 3D integrated circuit

Integrated photonics promises solutions to questions of stability, complexity, and size in quantum optics. Advances in tunable and non-planar integrated platforms, such laser-inscribed photonics, continue to bring the realisation of quantum advantages in computation and metrology ever closer, perhaps most easily seen in multi-path interferometry. Here we demonstrate control of two-photon interference in a chip-scale 3D multi-path interferometer, showing a reduced periodicity and enhanced visibility compared to single photon measurements. Observed non-classical visibilities are widely tunable, and explained well by theoretical predictions based on classical measurements. With these predictions we extract a Fisher information approaching a theoretical maximum, demonstrating the capability of the device for quantum enhanced phase measurements.Comment: 11 pages, 24 figure

The effect of scattering loss on connections between classical and quantum processes in second-order nonlinear waveguides

We show that a useful connection exists between spontaneous parametric downconversion (SPDC) and sum frequency generation in nonlinear optical waveguides with arbitrary scattering loss, while the same does not hold true for SPDC and difference frequency generation. This result deepens the relationship between quantum and classical second-order nonlinear optical processes in waveguides, and identifies the most accurate characterization of their quantum performance in the presence of loss based solely on classical measurements

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 $1.64\times~10^{-4}$ 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 $5.05\times10^6$/s. The second order correlations indicate that the generated photon pairs are in a strongly non-classical regime.Comment: 5 pages, 5 figure

Parasitic nonlinearities in photon pair generation via integrated spontaneous four-wave mixing: critical problem or distraction?

We consider integrated photon pair sources based on spontaneous four-wave mixing and derive expressions for the pump powers at which various nonlinear processes become relevant for a variety of source materials and structures. These expressions serve as rules of thumb in identifying reasonable parameter regimes for the design of such sources. We demonstrate that if pump powers are kept low enough to suppress cross-phase modulation, multi-pair events as well as many other nonlinear effects are often also constrained to negligible levels

Tailoring second-harmonic generation in birefringent poled fiber via Twist

We predict theoretically and demonstrate experimentally the ability to generate and control the strengths of various second-harmonic signals in birefringent poled fiber. This is done by simply twisting the fiber