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Cavity optomechanical systems enable interactions between light and mechanical resonators, providing a platform both for fundamental physics of macroscopic quantum systems and for practical applications of precision sensing. The resonant enhancement of both mechanical and optical response in the cavity optomechanical systems has enabled precision sensing of multiple physical quantities, including displacements, masses, forces, accelerations, magnetic fields, and ultrasounds. In this article, we review the progress of precision sensing applications using cavity optomechanical systems. The review is organized in the following way: first we will introduce the physical principles of optomechanical sensing, including a discussion of the noises and sensitivity of the systems, and then review the progress in displacement sensing, mass sensing, force sensing, atomic force microscope (AFM) and magnetic resonance force microscope (MRFM), accelerometry, magnetometry, and ultrasound sensing, and introduce the progress of using quantum techniques especially squeezed light to enhance the performance of the optomechanical sensors. Finally, we give a summary and outlook.

We propose two designs of low-loss and temperature-insensitive single-mode waveguide crossing on silicon-on-insulator (SOI) platform with 415-nm operation bandwidth covering all optical communication bands. Both designs are enabled by subwavelength grating (SWG) modeled as an anisotropic metamaterial. The initial design applies straight SWG as the lateral cladding of the waveguide crossing to minimize the refractive index contrast and reduce the insertion loss (IL), but needs a relatively long taper. An improved design is then proposed where the curved SWG is introduced to replace the straight SWG to decrease the taper length and improve the performance. The waveguide crossing with the improved design achieves a calculated maximum IL of 0.229 dB and maximum crosstalk of −35.6 dB over a 415-nm wavelength range from 1260 nm to 1675 nm. The proposed devices are fabricated and characterized. Measured results of the improved design show a maximum IL of 0.264 dB and maximum crosstalk of −30.9 dB over a 230-nm wavelength range including O-, C-, and L-bands, which accord well with the simulation. Low temperature sensitivity has also been demonstrated in both simulations and experiments.

The demand for point-of-care biosensors capable of rapid, accurate, and specific detection has grown significantly, particularly in the wake of the COVID-19 pandemic. Silicon photonics-based biosensors, based on evanescent wave sensing, have positioned as competitive candidates to meet these needs due to their high index contrast, compact size, high sensitivity and specificity, CMOS compatibility, and low cost. Among various configurations, the bimodal waveguide (BiMW) interferometer stands out for its high sensitivity and compact footprint. Meanwhile, subwavelength grating (SWG) waveguides offer enhanced sensitivity by providing a larger active sensing area compared to conventional waveguides. In this work, we propose integrating SWG waveguides with BiMW interferometers, using silicon nitride (Si 3 N 4 ) as the guiding material in the visible wavelength range to improve sensing performance through enhanced sensitivity and compactness. Si 3 N 4 offers advantages such as low scattering losses and chemical stability in biological environments, while operation in visible range increases compatibility with biological assays, making this approach novel. We present a comprehensive device design, optimization, and analysis of the SWG-based BiMW interferometer for refractive index sensing applications. Three-dimensional full vectorial simulations were conducted using the finite element method in COMSOL Multiphysics for the device design and optimizations. The proposed device demonstrates notable improvements in sensing performance, with an intrinsic bulk sensitivity of 0.1479 RIU/RIU, intrinsic surface sensitivity of 2.41 × 10 −4 RIU nm −1 , and a theoretical phase sensitivity of 1318 rad RIU −1 mm −1 , all achieved within a compact footprint.

We investigate the performance of Opticks, a NVIDIA OptiX API 7.5 GPU-accelerated photon propagation tool compared with a single-threaded Geant4 simulation. We compare the simulations using an improved model of the NEXT-CRAB-0 gaseous time projection chamber. Performance results suggest that Opticks improves simulation speeds by between 58.47 ± 0.02 and 181.39 ± 0.28 times relative to a CPU-only Geant4 simulation and these results vary between different types of GPU and CPU. A detailed comparison shows that the number of detected photons, along with their times and wavelengths, are in good agreement between Opticks and Geant4.

Integration of multiple diversified functionalities into an ultracompact platform is crucial for the development of on-chip photonic devices. Recently, a promising all-dielectric two-dimensional platform based on Bloch surface waves (BSWs) sustained by dielectric multilayer has been proposed to enable various functionalities and provide novel approach to photonic devices. Here, we design and fabricate a multifunctional directional coupler to achieve both spectral and polarimetric routing by employing asymmetric nanoslits in a dielectric multilayer platform. Due to the dispersion property of BSWs, the directional coupling behavior is sensitive to wavelength and polarization. We demonstrate numerically and experimentally the wavelength selective directional coupling of TE BSW mode with an intensity ratio of the BSW excitation in opposite directions reaching 10 dB. Polarization selective directional coupling is also achieved at specific operating wavelength due to different response to a nanoantenna for TE and TM BSWs. The proposed two-dimensional photonic device opens new pathway for a wide range of practical applications such as molecular sensing, imaging with different polarization, and spectral requirements.

Realizing large-scale single-mode, high-power, high-beam-quality semiconductor lasers, which rival (or even replace) bulky gas and solid-state lasers, is one of the ultimate goals of photonics and laser physics. Conventional high-power semiconductor lasers, however, inevitably suffer from poor beam quality owing to the onset of many-mode oscillation 1 , 2 , and, moreover, the oscillation is destabilized by disruptive thermal effects under continuous-wave (CW) operation 3 , 4 . Here, we surmount these challenges by developing large-scale photonic-crystal surface-emitting lasers with controlled Hermitian and non-Hermitian couplings inside the photonic crystal and a pre-installed spatial distribution of the lattice constant, which maintains these couplings even under CW conditions. A CW output power exceeding 50 W with purely single-mode oscillation and an exceptionally narrow beam divergence of 0.05° has been achieved for photonic-crystal surface-emitting lasers with a large resonant diameter of 3 mm, corresponding to over 10,000 wavelengths in the material. The brightness, a figure of merit encapsulating both output power and beam quality, reaches 1 GW cm −2  sr −1 , which rivals those of existing bulky lasers. Our work is an important milestone toward the advent of single-mode 1-kW-class semiconductor lasers, which are expected to replace conventional, bulkier lasers in the near future. We developed large-scale photonic-crystal surface-emitting lasers with controlled Hermitian and non-Hermitian couplings inside the photonic crystal and a pre-installed spatial distribution of the lattice constant, which leads to the realization of a continuous-wave brightness of 1 GW cm −2  sr −1 .

Propagation of light beams through scattering or multimode systems may lead to the randomization of the spatial coherence of the light. Although information is not lost, its recovery requires a coherent interferometric reconstruction of the original signals, which have been scrambled into the modes of the scattering system. Here we show that we can automatically unscramble optical beams that have been arbitrarily mixed in a multimode waveguide, undoing the scattering and mixing between the spatial modes through a mesh of silicon photonics tuneable beam splitters. Transparent light detectors integrated in a photonic chip are used to directly monitor the evolution of each mode along the mesh, allowing sequential tuning and adaptive individual feedback control of each beam splitter. The entire mesh self-configures automatically through a progressive tuning algorithm and resets itself after significantly perturbing the mixing, without turning off the beams. We demonstrate information recovery by the simultaneous unscrambling, sorting and tracking of four mixed modes, with residual cross-talk of −20 dB between the beams. Circuit partitioning assisted by transparent detectors enables scalability to meshes with a higher port count and to a higher number of modes without a proportionate increase in the control complexity. The principle of self-configuring and self-resetting in optical systems should be applicable in a wide range of optical applications. Silicon photonics: unscrambling scrambled light A silicon photonics chip featuring a mesh of tunable beam splitters can unscramble mode mixing that occurs in multimode waveguides. Scattering or multimode systems can randomize the spatial coherence of light beams. Francesco Morichetti and co-workers from Politecnico di Milano, Italy, and Stanford University, USA, have fabricated a chip-based descrambler that can automatically unscramble optical beams. A progressive tuning algorithm that monitors the output of the chip enables the mesh to self-configure so that it can unscramble and sort different spatial modes. In a demonstration of the device, four optical beams containing mixed modes were unmixed and separated into outputs with a residual crosstalk of less than −20 dB between the modes. The approach is scalable to a higher number of modes and is promising for optical communication systems employing mode division multiplexing.

The combination of integrated optics technologies with nonlinear photonics, which has led to the growth of nonlinear integrated photonics, has also opened the way to groundbreaking new devices and applications. Here we introduce the main physical processes involved in nonlinear photonics applications, and we discuss the fundaments of this research area, starting from traditional second-order and third-order phenomena and going to ultrafast phenomena. The applications, on the other hand, have been made possible by the availability of suitable materials, with high nonlinear coefficients, and/or by the design of guided-wave structures, which can enhance the material’s nonlinear properties. A summary of the most common nonlinear materials is presented, together with a discussion of the innovative ones. The discussion of fabrication processes and integration platforms is the subject of a companion article, also submitted for publication in this journal. There, several examples of nonlinear photonic integrated devices to be employed in optical communications, all-optical signal processing and computing, or quantum optics are shown, too. We aimed at offering a broad overview, even if, certainly, not exhaustive. We hope that the overall work could provide guidance for those who are newcomers to this field and some hints to the interested researchers for a more detailed investigation of the present and future development of this hot and rapidly growing field.

Superconducting cavity electro-optics presents a promising route to coherently convert microwave and optical photons and distribute quantum entanglement between superconducting circuits over long-distance. Strong Pockels nonlinearity and high-performance optical cavity are the prerequisites for high conversion efficiency. Thin-film lithium niobate (TFLN) offers these desired characteristics. Despite significant recent progresses, only unidirectional conversion with efficiencies on the order of 10 −5 has been realized. In this article, we demonstrate the bidirectional electro-optic conversion in TFLN-superconductor hybrid system, with conversion efficiency improved by more than three orders of magnitude. Our air-clad device architecture boosts the sustainable intracavity pump power at cryogenic temperatures by suppressing the prominent photorefractive effect that limits cryogenic performance of TFLN, and reaches an efficiency of 1.02% (internal efficiency of 15.2%). This work firmly establishes the TFLN-superconductor hybrid EO system as a highly competitive transduction platform for future quantum network applications. Coherent conversion between optical and microwave photonics is needed for future quantum applications. Here, the authors combine thin-film lithium niobate and superconductor platforms as a hybrid electro-optic system to achieve high-efficiency frequency conversion between microwave and optical modes.

This work aims to explore the structural, dielectric and optical properties of titanium nitride (TiN)/silicon dioxide (SiO 2 ) nanostructures doped polyvinyl alcohol(PVA) to utilize in several electronics and photonics nanodevices. The dielectric characteristics were investigated in frequency (f) range from 100 Hz to 5 × 10 6  Hz. The results of dielectric properties displayed that the dielectric constant and conductivity of PVA increased about 17.4% and 58.7% respectively at f = 1 kHz when the content of TiN-SiO 2 NPs reached 6wt.% with low values of dielectric loss which made it can be considered as a key for various nanodielectrics devices and energy storage fields. The dielectric parameters of PVA/TiN-SiO 2 nanocomposites were changed as the frequency increased. The optical properties were studied at wavelength (λ) ranged (200–800) nm. The absorbance of PVA was rise about 97.5% with adding of 6 wt.% of TiN-SiO 2 NPs and the optical conductivity increased about 98.7% at λ = 500 nm, this performance make them as promising materials in various optical and electronics fields like photocatalysis, optoelectronics and solar cells applications. The energy gap was reduced from 4.5 eV for pure polymer to 1.8 eV when the content of TiN-SiO 2 NPs reached 6wt %. The results of other optical parameters enhanced with rise in the concentration of TiN-SiO 2 NPs. Finally, the results demonstrated that the (PVA-TiN-SiO 2 ) nanostructures can be considered as promising materials in the nanodielectrics and photonics applications with individual characteristics included low cost, flexible, lightweight, excellent optical and electronic properties compare with other nanocomposites.