Extension of second-harmonic phase-matching range in lithium niobate guides

Correlated twin-photon generation in a silicon nitride loaded thin film PPLN waveguide

Photon-pair sources based on thin film lithium niobate on insulator technology have a great potential for integrated optical quantum information processing. We report on such a source of correlated twin-photon pairs generated by spontaneous parametric down conversion in a silicon nitride (SiN) rib loaded thin film periodically poled lithium niobate (LN) waveguide. The generated correlated photon pairs have a wavelength centred at 1560 nm compatible with present telecom infrastructure, a large bandwidth (21 THz) and a brightness of ∼2.5 × 10⁵ pairs/s/mW/GHz. Using the Hanbury Brown and Twiss effect, we have also shown heralded single photon emission, achieving an autocorrelation g H(2)(0)≃0.04.

Integrated high quality factor lithium niobate microdisk resonators

Lithium Niobate (LN) is an important nonlinear optical material. Here we demonstrate LN microdisk resonators that feature optical quality factor ~10(5), realized using robust and scalable fabrication techniques, that operate over a wide wavelength range spanning visible and near infrared. Using our resonators, and leveraging LN's large second order optical nonlinearity, we demonstrate on-chip second harmonic generation with a conversion efficiency of 0.109 W(-1).

LiNbO(3) waveguide second-harmonic-generation device phase matched with a fan-out domain-inverted grating

A LiNbO(3) waveguide optical second-harmonic-generation (SHG) device, consisting of a channel waveguide array and a ferroelectric domain-inverted grating in a fan pattern for quasi-phase matching, is proposed. The structure has redundancy to absorb the residual phase mismatch caused by design uncertainties and fabrication errors. A SHG device of 3-mm interaction length was fabricated by domain inversion by Ti indiffusion and channel waveguide formation by annealed proton exchanging and reactive ion etching. A normalized SHG efficiency of 17%/W was experimentally obtained for pumping by a cw Nd:YAG laser.

Secondary-ion mass spectroscopy characterization of proton-exchanged LiNbO(3) waveguides

Channel waveguides fabricated in LiNbO(3) substrates by proton exchange in melts of benzoic acid have been analyzed by secondary-ion mass spectroscopy. The depletion of lithium from the waveguide regions, owing to proton exchange, was found to depend to a strong degree on guide width as well as diffusion time for common (249 degrees C) ion-exchange temperatures. In addition to a reduced depth, a guide formed by diffusing through a 6-microm-wide metallic aperture for 10 min suffered 60% less lithium depletion near its surface than one formed by diffusing through a 12-microm aperture for the same time. Optical measurements were performed at 1060 and 1320 nm in guides of width ranging from 5 to 10 microm.