Classical clock synchronization for quantum communications using the quantum channel.

We present a time synchronization method for correlation of photon arrival times for quantum communication. The method employs a low-power, low-frequency synchronization beacon that shares the quantum channel and is detected using the same single-photon detectors already present in the quantum communication system. We show experimentally that the system jitter approaches the system resolution limit with negligible impact on the quantum channel in realistic use cases. The presented method is particularly suitable for long distance quantum communication with large clock drifts, such as quantum links involving satellites.

The deep space quantum link: prospective fundamental physics experiments using long-baseline quantum optics.

The National Aeronautics and Space Administration's Deep Space Quantum Link mission concept enables a unique set of science experiments by establishing robust quantum optical links across extremely long baselines. Potential mission configurations include establishing a quantum link between the Lunar Gateway moon-orbiting space station and nodes on or near the Earth. This publication summarizes the principal experimental goals of the Deep Space Quantum Link. These goals, identified through a multi-year design study conducted by the authors, include long-range teleportation, tests of gravitational coupling to quantum states, and advanced tests of quantum nonlocality.

Reconfigurable optical spectra from perturbations on elliptical whispering gallery resonances.

Elastic strain, electrical bias, and localized geometric deformations were applied to elliptical whispering-gallery-mode resonators fabricated with lithium niobate. The resultant perturbation of the mode spectrum is highly dependant on the modal indices, resulting in a discretely reconfigurable optical spectrum. Breaking of the spatial degeneracy of the whispering-gallery modes due to perturbation is also observed.

Coherent backscattering in lithium niobate whispering-gallery-mode resonators.

Splitting of high-Q whispering gallery modes into a doublet of counterpropagating modes was observed in a resonator fabricated from LiNbO(3). An energy-transfer rate of 10 MHz was calculated by measuring the frequency detuning of the doublet structure. The splitting rate is also used to calculate the maximum variation in the internal index of refraction over one wavelength, which is of the order of 10(-7). This shows that the mechanical process used to fabricate whispering-gallery-mode resonators from LiNbO(3) is sufficient to achieve material-limited quality factors.

Ringdown spectroscopy of stimulated Raman scattering in a whispering gallery mode resonator.

We report experimental observations of power-dependent, nonexponential decay of light stored in whispering gallery modes caused by stimulated Raman scattering in the resonator host material. Specifically, we show that the instantaneous decay rate of whispering gallery modes of a calcium fluoride resonator increases as the amount of light stored in the resonator decreases.

High-Q optical whispering gallery modes in elliptical LiNbO(3) resonant cavities.

We have experimentally demonstrated the existence of optical whispering-gallery-modes (WGMs) with quality factors in excess of 10(8) in elliptical cavities fabricated with LiNbO(3). The efficiency of evanescent coupling to the modes through a diamond prism was as high as 97.3%. This is the best value ever achieved for evanescent coupling to a WGM resonator using a prism. The free spectral ranges of the WGMs are successfully modeled using an eikonal approximation.

Efficient generation of truncated Bessel beams using cylindrical waveguides.

In this paper we address efficient conversion between a Gaussian beam (a truncated plane wave) and a truncated Bessel beam of a given order, using cylindrical optical waveguides and whispering gallery mode resonators. Utilizing a generator based on waveguides combined with whispering gallery mode resonators, we have realized Bessel beams of the order of 200 with a conversion efficiency exceeding 10 %.

Measurement of the far field intensity distribution of a bent and cleaved fiber taper.

We have theoretically predicted and experimentally demonstrated mode conversion in fiber tapers subject to large adiabatic bending. The far field intensity distribution of the taper mode is imaged in part by cleaving the taper at the position of minimum diameter.

Morphology-dependent photonic circuit elements.

We theoretically propose and experimentally demonstrate the design of a novel one-dimensional ringlike macroscopic optical circuit element. The similarity between morphologies of an optical planar waveguide and a whispering-gallery axially symmetric solid-state resonator is used.

Calligraphic poling of Lithium Niobate.

We demonstrate a novel technique for instituting complex and arbitrary shaped micron-scale domain patterns in LiNbO3 at room temperature. Fabrication of continuous domains as narrow as 2 microm across and hexagonal patterns of the same order accompanied by real time visualization of the poling process are presented.

Low threshold optical oscillations in a whispering gallery mode CaF(2) resonator.

We have observed low-threshold optical hyperparametric oscillations in a high-Q fluorite whispering gallery mode resonator. The oscillations result from the resonantly enhanced four-wave mixing occurring due to Kerr nonlinearity of the material. We demonstrate that, because of the narrow bandwidth of the resonator modes as well as the high efficiency of the resonant frequency conversion, the oscillations produce stable narrow-band beat-note of the pump, signal, and idler waves. A theoretical model for this process is described.