Wei C. Jiang

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.

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.

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.

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.

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.

Twin photon pairs in a high-Q silicon microresonator

We report the generation of high-purity twin photon pairs in a high-Q silicon microdisk resonator, with a pair flux of 5.31 × 10s pairs/s within a bandwidth of 0.73 GHz, and a high CAR as large as 155, the highest value reported to date for twin photon pairs.

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.

Dispersion engineering of high-Q silicon microresonators via thermal oxidation

Abstract : We propose and demonstrate a convenient and sensitive technique for precise engineering of group-velocity dispersion in high-Q silicon microresonators. By accurately controlling the surface-oxidation thickness of silicon microdisk resonators, we are able to precisely manage the zero-dispersion wavelength, while simultaneously further improving the high optical quality of our devices, with the optical Q close to a million. The demonstrated dispersion management allows us to achieve parametric generation with precisely engineerable emission wavelengths, which shows great potential for application in integrated silicon nonlinear and 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.

Selective engineering of cavity resonance for frequency matching in optical parametric processes

We propose to selectively engineer a single cavity resonance to achieve frequency matching for optical parametric processes in high-Q microresonators. For this purpose, we demonstrate an approach, selective mode splitting (SMS), to precisely shift a targeted cavity resonance, while leaving other cavity modes intact. We apply SMS to achieve efficient parametric generation via four-wave mixing in high-Q silicon microresonators. The proposed approach is of great potential for broad applications in integrated nonlinear photonics.