High extinction ratio, low insertion loss, optical switch based on an electrowetting prism

An optical switch based on an electrowetting prism coupled to a multimode fiber has demonstrated a large extinction ratio with speeds up to 300 Hz. Electrowetting prisms provide a transmissive, low power, and compact alternative to conventional free-space optical switches, with no moving parts. The electrowetting prism performs beam steering of &plusmn;3&deg; with an extinction ratio of 47 dB between the ON and OFF states and has been experimentally demonstrated at scanning frequencies of 100&ndash;300 Hz. The optical design is modeled in Zemax to account for secondary rays created at each surface interface (without scattering). Simulations predict 50 dB of extinction, in good agreement with experiment.</p

Enhancement of third-order nonlinearity of thermally evaporated GeSbSe waveguides through annealing

Chalcogenides are a promising platform for infrared nonlinear optics but are susceptible to structural changes during fabrication that affect their linear and nonlinear optical properties. We analyze the structure and optical properties of thermally evaporated and annealed chalcogenide films. Thermally evaporated Ge Sb Se has an increased selenium content, bandgap, and concentration of heteropolar bonds. The concentration of heteropolar bonds can be reduced by annealing above the glass transition temperature, resulting in improved optical nonlinearity. We demonstrate a 4-fold enhancement of third-order nonlinearity in Ge Sb Se chalcogenide waveguides by thermal annealing and a decrease in propagation loss from 2.5 dB/cm to 1 dB/cm as an added benefit.</p

Third-harmonic generation enhancement in an ITO nanoparticle-coated microresonator

We report a &sim;3-fold enhancement of third-harmonic generation (THG) conversion efficiency using indium tin oxide (ITO) nanoparticles on the surface of an ultra-high-Q silica microsphere. This is one of the largest microcavity-based THG enhancements reported. Phase-matching and spatial mode overlap are explored numerically to determine the microsphere radius (&sim;29 &micro;m) and resonant mode numbers that maximize THG. Furthermore, the ITO nanoparticles are uniformly bonded to the cavity surface by drop-casting, eliminating the need for complex fabrication. The significant improvement in THG conversion efficiency establishes functionalized ITO microcavities as a promising tool for broadband frequency conversion, nonlinear enhancement, and applications in integrated photonics.</p

Lidar system with nonmechanical electrowetting-based wide-angle beam steering

A light detection and ranging (lidar) system with &plusmn;90&deg; of steering based on an adaptive electrowetting-based prism for nonmechanical beam steering has been demonstrated. Electrowetting-based prisms provide a transmissive, low power, and compact alternative to conventional adaptive optics as a nonmechanical beam scanner. The electrowetting prism has a steering range of &plusmn;7.8&deg;. We demonstrate a method to amplify the scan angle to &plusmn;90&deg; and perform a one-dimensional scan in a lidar system.</p

Spectrally tunable liquid resonator based on electrowetting

We present a tunable on-chip liquid resonator in conjunction with a tapered fiber coupling scheme. The resonator consists of a glycerol droplet submerged within an immiscible liquid bath, which mitigates the effects of environmental fluctuations. The platform is fabricated using standard semiconductor techniques, which enable the future integration of photonic components for an on-chip liquid resonator device. The liquid resonator maintains its high Q-factor on chip (105) due to surface tension forming an atomically smooth liquid-liquid interface. Higher Q-factor resonance modes experienced linewidth broadening due to the random excitation of thermal capillary vibrations. Spectral tuning is demonstrated using the electrowetting effect, increasing the surface&rsquo;s wettability and an expansion in the droplet diameter. A maximum spectral tuning of 1.44 nm&thinsp;&plusmn;&thinsp;5 pm is observed by applying 35 V. The tuning range is twice the free spectral range (FSR) of 0.679 nm measured at a pumping wavelength range of 770-775 nm. A 2D axisymmetric finite-element simulation shows resonance modes in good agreement with experimentally measured spectra and with predicted tuning speeds of 20 nm/s. &nbsp;</p

Numerical analysis of wavefront aberration correction using multielectrode electrowetting-based devices.

We present numerical simulations of multielectrode electrowetting devices used in a novel optical design to correct wavefront aberration. Our optical system consists of two multielectrode devices, preceded by a single fixed lens. The multielectrode elements function as adaptive optical devices that can be used to correct aberrations inherent in many imaging setups, biological samples, and the atmosphere. We are able to accurately simulate the liquid-liquid interface shape using computational fluid dynamics. Ray tracing analysis of these surfaces shows clear evidence of aberration correction. To demonstrate the strength of our design, we studied three different input aberrations mixtures that include astigmatism, coma, trefoil, and additional higher order aberration terms, with amplitudes as large as one wave at 633 nm

Two-photon laser scanning microscopy with electrowetting-based prism scanning.

Laser scanners are an integral part of high resolution biomedical imaging systems such as confocal or 2-photon excitation (2PE) microscopes. In this work, we demonstrate the utility of electrowetting on dielectric (EWOD) prisms as a lateral laser-scanning element integrated in a conventional 2PE microscope. To the best of our knowledge, this is the first such demonstration for EWOD prisms. EWOD devices provide a transmissive, low power consuming, and compact alternative to conventional adaptive optics, and hence this technology has tremendous potential. We demonstrate 2PE microscope imaging of cultured mouse hippocampal neurons with a FOV of 130 × 130 μ

The Application Of Human Amniotic Membrane In Repairmen Of Dura Mater In Dogs

This study was conducted to show the comparison of efficacy and survival of amniotic membrane grafts and homologous dura grafts.&quot;nMethods and Materials: In this study, ten dogs (age 6-9 months &amp;amp; weight 15 lo 20 kg) have been chosen. The study was a single blind clinical trial. The dogs have been assigned into two groups by random allocation method. The amniotic membrane (A.M) was taken from a placenta belonging to a 38 weeks fetus delivered in a cesarean section surgery. In one group the graft was a peace of dura mater and in the other one the graft was a homologous dura graft. Maintenance of all cases was the same. Forty-five days later, another surgeon who was not aware of the assignment, conducted the second exploratory surgery for evaluation of the results.&quot;nResults: None of cases in two groups had any infection, abscess formation, fistula, CSF leakage or any toxic status. The healing process was normal in both groups.&quot;nConclusion: There seems to be no difference between the (A.M) grafts and homologous dura in the repairmen of dura mater. This is expected to occur only if the pregnant woman is carefully tested for the presence of certain clinical conditions and the preparation of A.M is contemplated in an ideal environment

Cascaded Forward Stimulated Brillouin Scattering in a Chalcogenide Microsphere

We report the first observation of cascaded forward Brillouin scattering in a microresonator platform. We have demonstrated 25 orders of intramodal Stokes beams separated by a Brillouin shift of 34.5 MHz at a sub-milliwatt threshold at 1550 nm. An As$_2$S$_3$ microsphere of diameter 125 $\\mu m$ with quality factor $1\times 10^6$ was used for this demonstration. Theoretical modeling is used to support our experimental observations of Brillouin shift and threshold power. We expect our work will advance the field of forward stimulated Brillouin scattering in integrated photonic

Wide-angle nonmechanical beam steering using liquid lenses

Nonmechanical beam steering is a rapidly growing branch of adaptive optics with applications such as light detection and ranging, imaging, optical communications, and atomic physics. Here, we present an innovative technique for one- and two-dimensional beam steering using multiple tunable liquid lenses. We use an approach in which one lens controls the spot divergence, and one to two decentered lenses act as prisms and steer the beam. Continuous 1D beam steering was demonstrated, achieving steering angles of ±39° using two tunable liquid lenses. The beam scanning angle was further enhanced to ±75° using a fisheye lens. By adding a third tunable liquid lens, we achieved 2D beam steering of ±75°. In this approach, the divergence of the scanning beam is controlled at all steering angles