Hybridization of circular and rectangular transverse profiles of nanophotonic modes for nonlinear optics.

Nanophotonic modes within rectangular cross sections are typically considered to have transverse rectangular field profiles. In this work, we show that, despite the rectangular cross section of most integrated waveguides and microring resonators, there exists considerable hybridization of transverse rectangular modes and transverse circular modes. These hybridized modes can be advantageous in nonlinear wave mixing processes. We use third-harmonic generation as an example to confirm that such a hybridized mode is advantageous in combining reasonable mode overlap and waveguide coupling to a fundamental mode in a silicon nitride microring. Our work illuminates the potential of using transverse circular modes in nanophotonic applications.

Ultra-low-power four-wave mixing wavelength conversion in high-Q chalcogenide microring resonators.

A compact Ge11.5As24Se64.5 chalcogenide microring resonator is fabricated with an intrinsic quality factor of 3.0×105 in the telecom band. By taking advantage of the strong nonlinearity and cavity enhancement, highly efficient wavelength conversion via four-wave mixing is demonstrated using a microring resonator. Conversion efficiency of -33.7dB is obtained by using an ultra-low pump power of 63.8 µW. This work shows that Ge11.5As24Se64.5 chalcogenide microring devices are promising for quantum photonics.

Nonlinear optical oscillation dynamics in high-Q lithium niobate microresonators.

Recent advance of lithium niobate microphotonic devices enables the exploration of intriguing nonlinear optical effects. We show complex nonlinear oscillation dynamics in high-Q lithium niobate microresonators that results from unique competition between the thermo-optic nonlinearity and the photorefractive effect, distinctive to other device systems and mechanisms ever reported. The observed phenomena are well described by our theory. This exploration helps understand the nonlinear optical behavior of high-Q lithium niobate microphotonic devices which would be crucial for future application of on-chip nonlinear lithium niobate photonics.

Silicon-chip source of bright photon pairs.

Integrated quantum photonics relies critically on the purity, scalability, integrability, and flexibility of a photon source to support diverse quantum functionalities on a single chip. Here we report a chip-scale photon-pair source on the silicon-on-insulator platform that utilizes dramatic cavity-enhanced four-wave mixing in a high-Q silicon microdisk resonator. The device is able to produce high-quality photon pairs at different wavelengths with a high spectral brightness of 6.24×10(7) pairs/s/mW(2)/GHz and photon-pair correlation with a coincidence-to-accidental ratio of 1386 ± 278 while pumped with a continuous-wave laser. The superior performance, together with the structural compactness and CMOS compatibility, opens up a great avenue towards quantum silicon photonics with capability of multi-channel parallel information processing for both integrated quantum computing and long-haul quantum communication.

Compact suspended silicon microring resonators with ultrahigh quality.

We propose and demonstrate compact suspended silicon microring resonators with ultra-high optical quality. We achieve an intrinsic quality factor of 9.2 × 10(5) for the resonator with a radius of 9 µm. The high optical quality factor, high optical confinement together with the suspended structure of our device enable great potential for broad applications in biosensing, quantum photonics, nonlinear photonics, cavity optomechanics, and optical signal processing.

Coherent optomechanical oscillation of a silica microsphere in an aqueous environment.

We report the observation of optomechanical oscillation by immersing a silica microsphere in liquid. Due to the ultra high quality factor of the microsphere in the aqueous environment, sufficient optical force was established to quiver the microsphere at a pump laser power around 1 mW.

Tuning group-velocity dispersion by optical force.

We propose an optomechanical approach for dispersion dynamic tuning and microengineering by taking advantage of the optical force in nano-optomechanical structures. Simulations of a suspended coupled silicon waveguide show that the zero-dispersion wavelength can be tuned by 40 nm by an optical pump power of 3 mW. Our approach exhibits great potential for broad applications in dispersion-sensitive processes, which not only offers a new root toward versatile tunable nonlinear photonics but may also open up a great avenue toward a new regime of nonlinear dynamics coupling between nonlinear optical and optomechanical effects.

High-frequency silicon optomechanical oscillator with an ultralow threshold.

We demonstrate a highly efficient optomechanical oscillator based upon a small silicon microdisk resonator with a 2-µm radius. The device exhibits a strong optomechanical coupling of 115 GHz/nm and a large intrinsic mechanical frequency-Q product of 4.32 × 10(12) Hz. It is able to operate at a high frequency of 1.294 GHz with an ultralow threshold of 3.56 µW while working in the air environment. The high efficiency, high frequency together with the structural compactness and CMOS compatibility of our device enables great potential for broad applications in photonic-phononic signal processing, sensing, and metrology.

Chip-scale cavity optomechanics in lithium niobate.

We develop a chip-scale cavity optomechanical system in single-crystal lithium niobate that exhibits high optical quality factors and a large frequency-quality product as high as 3.6 × 1012 Hz at room temperature and atmosphere. The excellent optical and mechanical properties together with the strong optomechanical coupling allow us to efficiently excite the coherent regenerative optomechanical oscillation operating at 375 MHz with a threshold power of 174 µW in the air. The demonstrated lithium niobate optomechanical device enables great potential for achieving electro-optic-mechanical hybrid systems for broad applications in sensing, metrology, and quantum physics.

Cavity optomechanical spring sensing of single molecules.

Label-free bio-sensing is a critical functionality underlying a variety of health- and security-related applications. Micro-/nano-photonic devices are well suited for this purpose and have emerged as promising platforms in recent years. Here we propose and demonstrate an approach that utilizes the optical spring effect in a high-Q coherent optomechanical oscillator to dramatically enhance the sensing resolution by orders of magnitude compared with conventional approaches, allowing us to detect single bovine serum albumin proteins with a molecular weight of 66 kDa at a signal-to-noise ratio of 16.8. The unique optical spring sensing approach opens up a distinctive avenue that not only enables biomolecule sensing and recognition at individual level, but is also of great promise for broad physical sensing applications that rely on sensitive detection of optical cavity resonance shift to probe external physical parameters.