Hybrid Integration of Silicon Photonic Devices on Lithium Niobate for Optomechanical Wavelength Conversion

Unveiling Efficient Acousto-Optic Modulation in Silicon Photonic Devices via Lithium Niobate Using Transfer Printing

Piezo-optomechanics presents a promising route to convert microwave signals to the optical domain, implementing processing tasks that are challenging using conventional electronics. The surge of integrated photonics facilitates the exploitation of localized light-sound interactions toward new technological paradigms. However, efficient acousto-optic interaction has yet to be fully exploited in silicon due to the absence of piezoelectricity, despite its maturity in photonic integrated circuits. Here, we introduce a distinctive acousto-optic scheme to supplement silicon photonic devices through heterogeneous integration with lithium niobate (LN). Utilizing LN as an efficient acoustic pump to harness the inherently exceptional photoelasticity in silicon, we demonstrate efficient microwave-to-acoustic transduction, ultimately achieving a modulation figure-of-merit of VπL ∼ 0.496 V·cm. This efficient modulation scheme is further extended to implement non-reciprocal intermodal modulation. The proposed hybrid integration route opens new possibilities for tailoring photon-phonon interactions in silicon, consolidating acousto-optic technology in multifunctional integrated photonics.

A Fiber-Coupled Scanning Magnetometer with Nitrogen-Vacancy Spins in a Diamond Nanobeam

Magnetic imaging with nitrogen-vacancy (NV) spins in diamond is becoming an established tool for studying nanoscale physics in condensed matter systems. However, the optical access required for NV spin readout remains an important hurdle for operation in challenging environments such as millikelvin cryostats or biological systems. Here, we demonstrate a scanning-NV sensor consisting of a diamond nanobeam that is optically coupled to a tapered optical fiber. This nanobeam sensor combines a natural scanning-probe geometry with high-efficiency through-fiber optical excitation and readout of the NV spins. We demonstrate through-fiber optically interrogated electron spin resonance and proof-of-principle magnetometry operation by imaging spin waves in an yttrium-iron-garnet thin film. Our scanning-nanobeam sensor can be combined with nanophotonic structuring to control the light-matter interaction strength and has potential for applications that benefit from all-fiber sensor access, such as millikelvin systems.

Integrated optical-readout of a high-Q mechanical out-of-plane mode

The rapid development of high-Q_M macroscopic mechanical resonators has enabled great advances in optomechanics. Further improvements could allow for quantum-limited or quantum-enhanced applications at ambient temperature. Some of the remaining challenges include the integration of high-Q_M structures on a chip, while simultaneously achieving large coupling strengths through an optical read-out. Here, we present a versatile fabrication method, which allows us to build fully integrated optomechanical structures. We place a photonic crystal cavity directly above a mechanical resonator with high-Q_M fundamental out-of-plane mode, separated by a small gap. The highly confined optical field has a large overlap with the mechanical mode, enabling strong optomechanical interaction strengths. Furthermore, we implement a novel photonic crystal design, which allows for a very large cavity photon number, a highly important feature for optomechanical experiments and sensor applications. Our versatile approach is not limited to our particular design but allows for integrating an out-of-plane optical read-out into almost any device layout. Additionally, it can be scaled to large arrays and paves the way to realizing quantum experiments and applications with mechanical resonators based on high-Q_M out-of-plane modes alike.