Dyerhackett5821

This paper introduces a fiber-optic microelectromechanical system (MEMS) seismic-grade accelerometer that is fabricated by bulk silicon processing using photoresist/silicon dioxide composite masking technology. The proposed sensor is a silicon flexure accelerometer whose displacement transduction system employs a light intensity detection method based on Fabry-Perot interference (FPI). The FPI cavity is formed between the end surface of the cleaved optical fiber and the gold-surfaced sidewall of the proof mass. The proposed MEMS accelerometer is fabricated by one-step silicon deep reactive ion etching with different depths using the composite mask, among which photoresist is used as the etching-defining mask for patterning the etching area while silicon dioxide is used as the depth-defining mask. Noise evaluation experiment results reveal that the overall noise floor of the fiber-optic MEMS accelerometer is 2.4 ng/H z at 10 Hz with a sensitivity of 3165 V/g, which is lower than that of most reported micromachined optical accelerometers, and the displacement noise floor of the optical displacement transduction system is 208 fm/H z at 10 Hz. Therefore, the proposed MEMS accelerometer is promising for use in high-performance seismic exploration applications.We developed an inter-chip optical link using direct optical wire (DOW) bonding by open-to-air polymerization. An arch-shaped wire was drawn from a tip in a similar way to a metal wire, but the wire was formed from a polymer solution that solidified in the air during wiring. The DOW bonding was examined for silicon photonic chips where grating couplers are integrated for input/output coupling. Cone-shaped studs were formed at the ends of the wire, and their geometry was optimized using finite-difference time-domain simulation to give a mode conversion function. Although the polymer wire had a multimode scale of 7 µm, the wire bonding between the grating couplers showed a relatively low insertion loss of 5.8 dB at a wavelength of 1590 nm compared to a conventional connection using single-mode fiber blocks. It also showed a larger wavelength tolerance within the range of ∼1520-1590 nm. DOW bonding between a grating coupler and a single-mode fiber were also examined to verify the feasibility of out-of-plane connection with edge-coupling devices. The grating-to-fiber wire link also exhibited a large wavelength tolerance.We investigate the optical trapping of polystyrene microspheres in optical tweezers. selleck chemicals The transverse capture gradient forces of polystyrene microspheres with different numerical aperture are theoretically and experimentally evaluated by the power spectral density roll-off method. It is found that the trapping force of the experimental measurement is much stronger than that of the theoretical results. The discordance is attributed to the slow light effect near the focus, which has been found in recent years [Science347, 857 (2015)10.1126/science.aaa3035; Opt. Express18, 10822 (2010)10.1364/OE.18.010822; Opt. Commun.332, 164 (2014)10.1016/j.optcom.2014.06.057]. The modified trapping force of the theoretical results by considering the slow light effect near the focus is well consistent with that of the experimental results.We report experimental studies of the bending strain impact on the upconversion processes in Yb3+, Er3+, and Mn2+ co-doped BaTiO3 (BTO) thin films with mica as the flexible substrate. Bending strain induces strong enhancement and modulation of the upconversion emission in doped BTO thin films. Because the unshielded 3d5 configuration of Mn2+ is more susceptible to crystal field changes, the introduction of an Mn2+ ion further promotes the strain-induced modulation effect. The upconversion intensity is amplified by six times at bending strain ε = 1.83% in BTOYb3+/Er3+/Mn2+ thin films. These results demonstrate the opportunity of rendering an upconversion emission through integrating lanthanide-doped ferroelectric films with flexible mica, especially by incorporating an Mn2+ ion.Complex optical systems such as deterministic aperiodic Mathieu lattices are known to hinder light diffraction in a manner comparable to randomized optical systems. We systematically incorporate randomness in our complex optical system, measuring its relative contribution of randomness, to understand the relationship between randomness and complexity. We introduce an experimental method for the realization of disordered aperiodic Mathieu lattices with numerically controlled disorder degree. Added disorder always enhances light transport. For lower disorder degrees, we observe diffusive-like transport, and in the range of highest light transport, we detect Anderson localization. With further increase of disorder degree, light transport is slowly decreasing and localization length decreases indicating more pronounced Anderson localization. Numerical investigation at longer propagation distances indicates that the threshold of Anderson localization detection is shifted to lower disorder degrees.The use of a higher-order HE12-like mode to produce weak normal dispersion over a substantial wavelength range in a microstructured optical fiber is investigated numerically. It is shown that the effective area, and thereby the pulse energy, can in this way be scaled by an order of magnitude compared to using the fundamental mode in a single-mode fiber. Multimode nonlinear simulations indicate that nonlinear mode coupling will not disturb single-mode operation in the HE12 mode at least up to the threshold where polarization modulation instability sets in.All known realizations of optical wave packets that accelerate along their propagation axis, such as Airy wave packets in dispersive media or wave-front-modulated X-waves, exhibit a constant acceleration; that is, the group velocity varies linearly with propagation. Here we synthesize space-time wave packets that travel in free space with arbitrary axial acceleration profiles, including group velocities that change with integer or fractional exponents of the distance. Furthermore, we realize a composite acceleration profile the wave packet accelerates from an initial to a terminal group velocity, before decelerating back to the initial value. These never-before-seen optical-acceleration phenomena are produced using the same experimental arrangement that precisely sculpts the wave packet's spatio-temporal spectral structure.In this Letter, we demonstrate a third-order cascaded Raman shift in an all-solid fluorotellurite fiber pumped by a 1550 nm nanosecond laser. The fluorotellurite glass with a composition of TeO2-BaF2-Y2O3 (TBY) has a usable Raman shift of ∼785 cm-1 and a Raman gain coefficient of ∼1.65 × 10-12 m/W at 1550 nm, which is approximately 25.4 times larger than that of silica glass. By using a 5.38 m fluorotellurite fiber as the Raman gain medium and a 1550 nm nanosecond laser as the pump light, a third-order cascaded Raman shift is obtained via spontaneous cascaded Raman amplification in the fluorotellurite fiber, causing the generation of the first-, second-, and third-order Stokes emissions that peak at 1765, 2049, and 2438 nm, respectively. For an average pump power of ∼491.5 mW, the output power of the generated first-, second-, and third-order Stokes light is approximately 14.1, 67.4, and 31.6 mW, respectively. The corresponding conversion efficiency is approximately 2.87%, 13.70%, and 6.43%, respectively. Our results show that fluorotellurite fibers are promising Raman gain media for constructing cascaded Raman fiber lasers with a wide range of wavelengths.A novel method to detect a low-power radio-frequency (RF) signal with ultra-wide frequency range based on an optically injected optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. The optical injection to a distributed feedback (DFB) laser has the advantages of amplifying one sideband of the modulated optical signal selectively and a wide tunable frequency range. The detection upper range that reaches up to 26 GHz and can be improved theoretically. To the best of the authors' knowledge, this is the widest detection range based on an OEO. At the same time, the detection characteristics are good. The sensitivity of the system is -92 dBm and the maximum gain is 12.18 dB at 15.047 GHz. Considering the real application of the detection system, the properties such as dynamic range and performance for detecting a modulated RF signal are also investigated.We report a silicate-clad heavily Tm3+-doped germanate core multimaterial fiber that is successfully drawn by using a rod-in-tube method. This new fiber has a high gain per unit length of 6.11 dB/cm at 1.95 µm, which is, to the best of the authors' knowledge, the highest gain per unit length reported so far for Tm3+-doped glass fibers. By virtue of this high-gain glass fiber, an all-fiber-integrated passively mode-locked fiber laser with a fundamental repetition rate up to 4.3 GHz is demonstrated. Remarkably, the generated pulse operating at 1968 nm exhibits a signal-to-noise ratio of >76 dB in the radio-frequency domain. These results suggest that the silicate-clad heavily Tm3+-doped germanate core multimaterial fiber can act as a key building block for high repetition rate mode-locked fiber lasers at 2 µm.Recently, terahertz (THz) nonreciprocal and functionality-switchable devices have drawn much attention. Here we report a magnetic-free THz unidirectional perfect absorber as well as a functionality-switchable device between the band-pass filter and perfect absorber based on dielectric-graphene multilayers containing a VO2 defect layer. We provide a theoretical explanation for the nonreciprocal transmission properties. The working frequencies of these devices can be tailored by using graphene layers of different chemical potentials.A NdYAG single-crystal fiber amplifier for the amplification of continuous-wave single-frequency laser end-pumped by a laser diode (LD) is investigated. With a two-stage amplification configuration, an output power of 60.4 W under the total incident pump power of 200 W is achieved, which is, to our knowledge, the highest power from a continuous-wave single-frequency laser achieved with a single-crystal fiber scheme. The extraction efficiency reaches 41.6% in the second amplification stage, which is comparable with Innoslab amplifiers. The beam quality factors M2 at the maximum output power in the horizontal and vertical direction are measured to be 1.51 and 1.38, respectively. The long-term power instability for 1 hour is 0.97%.We report an effective strategy to promote the near-infrared surface-enhanced Raman scattering spectroscopy (NIR-SERS) activity by boosting the photon-induced charge transfer (PICT) efficiency at cryogenic temperature. Based on as-prepared Au/Ag nano-urchins (NUs) with abundant surface defects, the extremely low temperature (77 K) can significantly weaken the metallic lattice vibration and reduce the recombination of thermal phonons and photoexcited electrons, then accelerate the migration of energetic electrons. It enables the NIR-SERS detection limit of dye molecules to be achieved at 10-17 M, which is nearly three orders of magnitude better than that at room temperature. The present work provides a new, to the best of our knowledge, approach for ultra-trace NIR-SERS bioanalysis.