Integrated polarizer based on 45° tilted gratings.

We report the first integrated implementation of a polarizer based on the use of 45° tilted gratings in planar waveguides. The waveguides and gratings are fabricated by direct UV writing in a hydrogenated germanium-doped silica-on-silicon chip. We experimentally demonstrate a polarization extinction ratio per unit length of 0.25 dB mm -1 with a modelled wavelength dependence smaller than 0.3 dB for a 20 mm device over the C band from 1530-1570 nm. We also present a novel numerical study and analytical description of the architecture that are in good agreement with each other and the experimental data.

High-birefringence direct UV-written waveguides for use as heralded single-photon sources at telecommunication wavelengths.

Direct UV-written waveguides are fabricated in silica-on-silicon with birefringence of (4.9 ± 0.2) × 10-4, much greater than previously reported in this platform. We show that these waveguides are suitable for the generation of heralded single photons at telecommunication wavelengths by spontaneous four-wave mixing. A pulsed pump field at 1060 nm generates pairs of photons in highly detuned, spectrally uncorrelated modes near 1550 nm and 800 nm. Waveguide-to-fiber coupling efficiencies of 78-91 % are achieved for all fields. Waveguide birefringence is controlled through dopant concentration of GeCl4 and BCl3 using the flame hydrolysis deposition process. The technology provides a route towards the scalability of silica-on-silicon integrated components for photonic quantum experiments.

Wideband and continuously-tunable fractional photonic Hilbert transformer based on a single high-birefringence planar Bragg grating.

We propose and experimentally demonstrate wideband and continuously tunable fractional-order photonic Hilbert transformers (FrHT). These are realized by a single apodized planar Bragg grating within a high-birefringence planar substrate. The fractional order of the FrHT is continuously tuned and precisely controlled by changing the polarization state of the input light. The experimental characterization demonstrates an operating bandwidth up to 120 GHz with amplitude ripples below 3 dB. The optical phase shift response is directly measured to verify the proposed tuning property, demonstrating transform orders of around 1, 0.7, and 0.5. This approach is simple, stable, and compact compared to other existing methods and has great potential in the fields of ultrafast all-optical signal processing.