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Visible Laser on Silicon Optofluidic Microcavity
摘要： Optical readout within microfluidic chips is a bottleneck limiting their industrial development. The integration of lasers operating in the visible range within a microfluidic platform is crucial for enabling in situ optical measurements in lab-on-a-chip applications. In principle, microstructured single-crystal silicon is an excellent optofluidic platform, which allows integration of microfluidic channels together with optical circuits including micro-optics, waveguides, and resonant cavities. However, the silicon absorption below 1.1 μm is a fundamental limit that prohibits the use of silicon-based micro-cavities as the feedback element for visible lasers and restricts their use to the infrared only. In this work, an ultra-wide band silicon cavity enabled by two deeply etched hollow-core planar waveguides is demonstrated. The proposed microcavity shows a broad bandwidth extending from 500 to 1600 nm with quality factors up to 2067. A tubular microfluidic channel is inserted between the mirrors of the optofluidic cavity. The microfluidic channel is filled with Rhodamine 6G (R6G) at 20 μL min?1 flow rate allowing successful demonstration of lasing on silicon at 562.4 nm. The laser beam propagates in-plane (along the chip surface) and is handled with monolithically integrated input/output optical fiber grooves. This provides a unique silicon platform integrating hollow core optofluidic channels together with optical cavities, which is suitable for implementing optical readout in lab-on-a-chip devices.
关键词： visible lasers,microcavities,silicon,optofluidics,lab on a chip
更新于2025-09-23 15:21:01
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Emergent biaxiality in nematic microflows illuminated by a laser beam
摘要： Anisotropic fluids (e.g. liquid crystals) offer a remarkable promise as optofluidic materials owing to the directional, tunable, and coupled interactions between the material, flow, and the optical fields. Here we present a comprehensive in silico treatment of this anisotropic interaction by performing nonequilibrium molecular dynamics simulations. We quantify the response of a nematic liquid crystal (NLC) undergoing a Poiseuille flow in the Stokes regime, while being illuminated by a laser beam incident perpendicular to the flow direction. We adopt a minimalistic model to capture the interactions, accounting for two features: first, the laser heats up the NLC locally; and second, the laser polarises the NLC and exerts an optical torque that tends to reorient molecules of the nematic phase. Because of this reorientation the liquid crystal exhibits small regions of biaxiality, where the nematic director is one symmetry axis and the axis of rotation for the reorientation of the molecules is the other one. We find that the relative strength of the viscous and the optical torques mediates the flow-induced response of the biaxial regions, thereby tuning the emergence, shape and location of the regions of enhanced biaxiality. The mechanistic framework presented here promises experimentally tractable routes toward novel optofluidic applications based on material-flow-light interactions.
关键词： optofluidics,Liquid crystal,biaxiality,nematic phase,nonequilibrium molecular dynamics
更新于2025-09-12 10:27:22
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2D resolution improvement via 1D scanning Space-Time Digital Holography (STDH) in Optofluidics
摘要： Space-Time Digital Holography (STDH) exploits the object motion to record the hologram in a hybrid space-time domain. This representation adds new capabilities to conventional DH, such as unlimited extension of the Field of View (FoV) and tunable phase shifting. Here we show that STDH is able to improve the spatial resolution as well. Differently from other super-resolution approaches, stitching between holograms or their spectra is no longer required. Moreover, we introduce a new STDH modality to record and process hybrid space-time representations. This allows improving resolution with one single object scan, paving the way to the use of STDH for superresolution imaging onboard Lab on a Chip devices.
关键词： Space-Time Digital Holography,STDH,Lab on a Chip,optofluidics,super-resolution
更新于2025-09-11 14:15:04
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Infiltrated Photonic Crystal Fibers for Sensing Applications
摘要： Photonic crystal ?bers (PCFs) are a special class of optical ?bers with a periodic arrangement of microstructured holes located in the ?ber’s cladding. Light con?nement is achieved by means of either index-guiding, or the photonic bandgap effect in a low-index core. Ever since PCFs were ?rst demonstrated in 1995, their special characteristics, such as potentially high birefringence, very small or high nonlinearity, low propagation losses, and controllable dispersion parameters, have rendered them unique for many applications, such as sensors, high-power pulse transmission, and biomedical studies. When the holes of PCFs are ?lled with solids, liquids or gases, unprecedented opportunities for applications emerge. These include, but are not limited in, supercontinuum generation, propulsion of atoms through a hollow ?ber core, ?ber-loaded Bose–Einstein condensates, as well as enhanced sensing and measurement devices. For this reason, in?ltrated PCF have been the focus of intensive research in recent years. In this review, the fundamentals and fabrication of PCF in?ltrated with different materials are discussed. In addition, potential applications of in?ltrated PCF sensors are reviewed, identifying the challenges and limitations to scale up and commercialize this novel technology.
关键词： optical fiber sensors,photonic crystal fibers,optofluidics,plasmonic sensors,liquid crystals
更新于2025-09-09 09:28:46