L. G. Helt

Bi-photon spectral correlation measurements from a silicon nanowire in the quantum and classical regimes.

We use classical stimulated four-wave mixing to directly characterize quantum spectral correlations generated in a silicon nanowire for two different pump durations. Signal to noise is increased and acquisition time reduced compared to coincidence detection.

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 refines the relationship between these quantum and classical second-order nonlinear optical processes in waveguides, and identifies the most accurate characterization of a waveguides quantum performance in the presence of loss based solely on classical measurements.

Phase-sensitive tomography of the joint spectral amplitude of photon pair sources

We present a novel measurement technique to perform full phase-sensitive tomography on the joint spectrum of photon pair sources, using stimulated four-wave mixing and phase-sensitive amplification. Applying this method to an integrated silicon nanowire source with a frequency chirped pump laser, we are able to observe a corresponding phase change in the spectral amplitude that would otherwise be hidden in standard intensity measurements. With a highly nonlinear fiber source, we show that phase-sensitive measurements have superior sensitivity to small spectral features when compared to intensity measurements. This technique enables more complete characterization of photon pair sources based on nonlinear photonics.

Domain engineering algorithm for practical and effective photon sources

We introduce a method for shaping the spectral response of nonlinear light sources by tailoring the quasi-phase matching. Our algorithm relies on engineering the poling to accurately trace a generated target signal field amplitude to determine the desired nonlinearity profile. The proposed poling algorithm results in a poling pattern that is more robust to manufacture, as all domain inversions are of equal width. The poling pattern is verified using a nonlinear beam propagation method simulation. This approach is applied to achieve Gaussian-shaped phase matching along a potassium titanyl phosphate (KTP) crystal in order to generate pure heralded single photons of spectral purity ~0.996-this is highly desirable for heralded single photon quantum optics.

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.

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

Parasitic Photon-Pair Suppression via Photonic Stop-Band Engineering

1.64\times~10^{-4}

Effects of filtering on the purity of heralded single photons from parametric sources

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

Parametric fluorescence in a sequence of resonators: An analogy with Dicke superradiance

5.05\times10^6

Circumventing spontaneous Raman noise in a correlated photon pair source

/s. The second order correlations indicate that the generated photon pairs are in a strongly non-classical regime.