Dugandue8223

A tunable metamaterial (MM)-based silicon (Si) waveguide is presented that is composed of an MM nanodisk array on a Si-on insulator substrate. A significant modulation efficiency of transmission intensity could be realized by elevating individually or simultaneously the column number of MM nanodisks. For a convenient description, an MM-based Si waveguide with one, two, three, four, and five columns of MM nanodisks are denoted as MM-1, MM-2, MM-3, MM-4, and MM-5, respectively. Transmission intensity of MM-based Si waveguides could be switched between on and off states by driving different columns of MM nanodisks on the Si waveguide surface. Transmission intensities could be attenuated from 100% to 56%, 24%, 6%, 1%, and 0% for MM-1, MM-2, MM-3, MM-4, and MM-5, respectively, at the wavelength of 1.525 µm. Furthermore, the MM-5 device is exposed to an ambient environment with different refraction indices. It exhibits a linear relationship of resonance dips and refraction indexes. The proposed design of the MM-based Si waveguide provides potential possibilities in an optical switch, variable optical attenuator, and sensor applications.We demonstrate the generation of 1.1 J pulses of picosecond duration at 1 kHz repetition rate (1.1 kW average power) from a diode-pumped chirped pulse amplification YbYAG laser. The laser employs cryogenically cooled amplifiers to generate λ=1030nm pulses with average power of up to 1.26 kW prior to compression with excellent beam quality. Pulses are compressed to 4.5 ps duration with 90% efficiency. This compact picosecond laser will enable a variety of applications that require high energy ultrashort pulses at kilohertz repetition rates.A novel (to the best of our knowledge), fast method to measure in-plane object motion in 1D with sub-pixel accuracy which complements the correlation technique is proposed. The method is verified experimentally using both visible and terahertz images. The absolute sum of grey level accumulated change is used to quantify object motion. The method requires calibration for each target, but only addition and subtraction operations. This results in a decrease of two orders of magnitude in the computation time.The waist diameter of a tapered optical fiber (TOF) has been determined using the modal evolution during the tapering process of a single-mode optical fiber (SMF28) through the short-time Fourier transform (STFT) analysis. The STFT was utilized to calculate the cutoff moment of the different modes. By the knowledge of the cutoff diameter, the final diameter of the waist with accuracy better than 5 nm was measured. The TOF shape depends on the flame parameters, the material properties, and the stretching conditions. By calculating the TOF deformation rate of the TOF, the diameter of TOFs near the waist has been measured with an accuracy of 6.1%; moreover, the TOFs were fabricated with a non-uniform flame.Multimode optical fibers (MMFs), combined with wavefront control methods, have achieved minimally invasive in vivo imaging of neurons in deep-brain regions with diffraction-limited spatial resolution. Here, we report a method for volumetric two-photon fluorescence imaging with a MMF-based system requiring a single transmission matrix measurement. Central to this method is the use of a laser source able to generate both continuous wave light and femtosecond pulses. The chromatic dispersion of pulses generated an axially elongated excitation focus, which we used to demonstrate volumetric imaging of neurons and their dendrites in live rat brain slices through a 60 µm core MMF.Over the past two decades, integrated photonic sensors have been of major interest to the optical biosensor community due to their capability to detect low concentrations of molecules with label-free operation. Among these, interferometric sensors can be read-out with simple, fixed-wavelength laser sources and offer excellent detection limits but can suffer from sensitivity fading when not tuned to their quadrature point. Recently, coherently detected sensors were demonstrated as an attractive alternative to overcome this limitation. Here we show, for the first time, to the best of our knowledge, that this coherent scheme provides sub-nanogram per milliliter limits of detection in C-reactive protein immunoassays and that quasi-balanced optical arm lengths enable operation with inexpensive Fabry-Perot-type lasers sources at telecom wavelengths.Optical ionization of N2 and subsequent population redistribution among the ground and excited states of N2+ in an intense laser field are commonly accepted to be fundamentally responsible for the generation of N2+ lasing. By finely controlling this two-step process, the optimization of N2+ lasing is possibly achieved. Here, we design a waveform-controlled polarization-skewed (PS) pumping pulse, in which the leading and falling edges are orthogonally polarized, and their relative field strength and phase can be well controlled. We demonstrate that precise manipulation of the N2+ lasing at 391 nm and 428 nm emissions can be achieved by modulating both the relative phase and amplitudes of the two orthogonally polarized components of the pumping PS pulse. We find that the optimization of N2+ lasing depends not only on the competitive balance between the ionization and post-ionization coupling that varies in different pumping energies but also on the phase with the maximum intensity appearing at the phase of nπ. Orders of magnitude enhancement in the N2+ lasing intensity is observed as the phase changes from (n+1/2)π to nπ. The PS pulse with a controllable spatiotemporal waveform provides us a robust and straightforward tool to efficiently enhance the N2+ lasing emission.Motivated by the hot debate on the mechanism of laser-like emission at 391 nm from N2 gas irradiated by a strong 800 nm pump laser and a weak 400 nm seed laser, we theoretically study the temporal profile, optical gain, and modulation of the 391 nm signal from N2+. Our calculation sheds light on the long standing controversy on whether population inversion is indispensable for optical gain and show the Ramsey fringes of the emission intensity at 391 nm formed by additionally injecting another 800 nm pump or 400 nm seed, which provides strong evidence for the coherence driven modulation of transition dipole moment and population transfer between the A2Πu(ν=2)-X2Σg+ states and the B2Σu+(ν=0)-X2Σg+ states. Our results show that the 391 nm optical gain is susceptible to the population inversion within N2+ states manipulated by the Ramsey technique and thus clearly reveal their symbiosis. This study reveals not only the physical picture of producing N2+ population inversion but also versatile control of the N2+ air laser.Hyperspectral imaging provides spatially resolved spectral information. Utilizing dual-frequency combs as active illumination sources, hyperspectral imaging with ultra-high spectral resolution can be implemented in a scan-free manner when a detector array is used for heterodyne detection. Here, we show that dual-comb hyperspectral imaging can be performed with an uncooled near-to-mid-infrared detector by exploiting the detector array's high frame rate, achieving 10 Hz acquisition in 30 spectral channels across 16,384 pixels. Artificial intelligence (AI) enables real-time data reduction and imaging of gas concentration based on characteristic molecular absorption signatures. Owing to the detector array's sensitivity from 1 to 5 µm wavelength, this demonstration lays the foundation for real-time versatile imaging of molecular fingerprint signatures across the infrared wavelength regime with high temporal resolution.Optical sensors developed for the assessment of oxygen in tissue microvasculature, such as those based on near-infrared spectroscopy, are limited in application by light scattering. Optoacoustic methods are insensitive to light scattering, and therefore, they can provide higher specificity and accuracy when quantifying local vascular oxygenation. However, currently, to the best of our knowledge, there is no low-cost, single point, optoacoustic sensor for the dedicated measurement of oxygen saturation in tissue microvasculature. This work introduces a spectroscopic optoacoustic sensor (SPOAS) for the non-invasive measurement of local vascular oxygenation in real time. LC-2 datasheet SPOAS employs continuous wave laser diodes and measures at a single point, which makes it low-cost and portable. The SPOAS performance was benchmarked using blood phantoms, and it showed excellent linear correlation (R2=0.98) with a blood gas analyzer. Subsequent measurements of local vascular oxygenation in living mice during an oxygen stress test correlated well with simultaneous readings from a reference instrument.We demonstrate the three-fold post-chirped-pulse-amplification (post-CPA) pulse compression of a high peak power laser pulse using allyl diglycol carbonate (CR39), which was selected as the optimal material for near-field self-phase modulation out of a set of various nonlinear plastic materials, each characterized with respect to its nonlinear refractive index and optical transmission. The investigated materials could be applied for further pulse compression at high peak powers, as well as for gain narrowing compensation within millijoule-class amplifiers. The post-CPA pulse compression technique was tested directly after the first CPA stage within the POLARIS laser system, with the compact setup containing a single 1 mm thick plastic sample and a chirped mirror pair, which enabled a substantial shortening of the compressed pulse duration and, hence, a significant increase in the laser peak power without any additional modifications to the existing CPA chain.Two-dimensional (2D) semiconductors of graphene, as well as transition-metal dichalcogenides, have performed strong interaction with light. Here the strong light-matter interaction between monolayer tungsten disulphide (WS2) excitons and microcavity photons at room temperature is well studied by the introduction of a gain material embedded dielectric optical microcavity structure. A Rabi splitting of about 36 meV is observed in angle-resolved reflectance spectra at room temperature, which agrees well with the theoretical results simulated by using the transfer matrix method. Since the cavity structures and 2D semiconductors can be prepared, the cavity and the gain materials, respectively, can be optimized separately in this platform. An all-dielectric Fabry-Pérot microcavity provides a simple but effective way to study the room temperature strong coupling between cavity photons and 2D excitons.The World Health Organization (WHO) included gaming disorders in International Classification of Disease-11th (ICD-11) on May 25, 2019. Since then, some academics and the gaming industry have continued to argue over the health system's response to online addictive behaviors. Under these circumstances, a framework involving groups representing various interests is needed to derive a reasonable solution to the dispute over the inclusion of gaming disorders in ICD-11. For this framework to work effectively, it is necessary to agree on consistent and advanced research findings that harms related to the excessive use of digital devices or content continue to occur empirically all over the world and that addictive use constitutes a primary addictive disorder. The problematic risk taking involving emerging technologies may include not only health risks from addictive use, but also more general harms associated with digital ethics and norms such as privacy and transparent money transactions. An understanding of a public health model of addiction is required to reduce harms associated with online addictive behavior that exist behind risk taking.