Resonant Mirror Research Articles

Hybrid rotational cavity optomechanics using an atomic superfluid in a ring

We introduce a hybrid optomechanical system containing an annularly trapped Bose-Einstein condensate (BEC) inside an optical cavity driven by Lauguerre-Gaussian (LG) modes. Spiral phase elements serve as the end mirrors of the cavity such that the rear mirror oscillates torsionally about the cavity axis through a clamped support. As described earlier in a related system [P. Kumar , ], the condensate atoms interact with the optical cavity modes carrying orbital angular momentum which create two atomic side modes. We observe three peaks in the output noise spectrum corresponding to the atomic side modes and rotating mirror frequencies, respectively. We find that the trapped BEC's rotation reduces quantum fluctuations at the mirror's resonance frequency. We also find that the atomic side modes-cavity coupling and the optorotational coupling can produce bipartite and tripartite entanglements between various constituents of our hybrid system. We reduce the frequency difference between the side modes and the mirror by tuning the drive field's topological charge and the condensate atoms' rotation. When the atomic side modes become degenerate with the mirror, the stationary entanglement between the cavity and the mirror mode diminishes due to the suppression of cooling. Our proposal, which combines atomic superfluid circulation with mechanical rotation, provides a versatile platform for reducing quantum fluctuations and producing macroscopic entanglement with experimentally realizable parameters. Published by the American Physical Society 2024

Analytical study of the beam quality of a diode-pumped alkali laser with unstable resonator

Analytical model of Cs diode-pumped alkali laser with unstable confocal resonator is reported. Two of the parameters characterizing the quality of the output beam were studied: the axial luminous intensity in the far field and the power in the bucket (PIB). The far-field axial light intensity and PIB were compared with their values for a truncated Gaussian reference beam whose aperture was limited by the aperture of the large resonator mirror and 99% of the Gaussian beam energy passed through the aperture of this mirror. For large values of the unstable resonator magnification factor m > 5, the far-field axial light intensity is approximately 40% larger than that of the Gaussian reference beam. Analysis of the PIB curves showed that for large m > 5, the values of the integrated fractional encircled power within a sufficiently large diffraction angles for the unstable resonator exceed its values for the reference Gaussian beam.

Out-coupling characteristics of partial resonator mirror for compact terahertz free-electron laser

Out-coupling characteristics of partial resonator mirror for compact terahertz free-electron laser

[formula omitted]: A versatile approach for unsupervised segmentation of calcium imaging data

Recent advances in calcium imaging, including the development of fast and sensitive genetically encoded indicators, high-resolution camera chips for wide-field imaging, and resonant scanning mirrors in laser scanning microscopy, have notably improved the temporal and spatial resolution of functional imaging analysis. Nonetheless, the variability of imaging approaches and brain structures challenges the development of versatile and reliable segmentation methods. Standard techniques, such as manual selection of regions of interest or machine learning solutions, often fall short due to either user bias, non-transferability among systems, or computational demand. To overcome these issues, we developed CalciSeg, a data-driven and reproducible approach for unsupervised functional calcium imaging data segmentation. CalciSeg addresses the challenges associated with brain structure variability and user bias by offering a computationally efficient solution for automatic image segmentation based on two parameters: regions’ size limits and number of refinement iterations. We evaluated CalciSeg efficacy on datasets of varied complexity, different insect species (locusts, bees, and cockroaches), and imaging systems (wide-field, confocal, and multiphoton), showing the robustness and generality of our approach. Finally, the user-friendly nature and open-source availability of CalciSeg facilitate the integration of this algorithm into existing analysis pipelines.

Investigations on cleavage fracture mechanism and surface damage of indium phosphide by molecular dynamics simulation

The quality and undamaged size in the resonant cavity surface directly affect the operational stability and output power of semiconductor lasers. To meet the demand for large-size and high-quality mirror facets, a deep understanding of fracture mechanisms of mechanical cleavage is essential. Nevertheless, 3D models of cleavage fracture are rarely investigated. In this work, a molecular dynamics study on the cleavage mechanisms of indium phosphide is reported through examining the effects of the cleavage gap, scratch depth, and cleavage rate on the cleavage damage morphology. The proposed molecular dynamics approach provides insights into the details of cleavage fracture at the atomic level. The simulation results reveal that the cleavage fracture mechanism includes the deviation of cracks between adjacent cleavage surfaces. The predominant damage manifestations on the cleavage surfaces are mainly characterized by cleavage terraces that begin at the bottom of the scratched groove. The cleavage terraces propagate along the [001] crystal direction on the (110) cleavage surface and deviate from their path. This phenomenon is essentially related to the stress released during the crack propagation process. Compared with the cleavage gap and scratch depth, the cleavage rate significantly affects the critical cleavage load. Additionally, a good correlation between the density of the cleavage terraces and the maximum undamaged length is achieved and reasonably explained. Mastering the correlation between various cleavage conditions and cleavage surface damage will facilitate and guide the fabrication of nanoscale resonant cavity mirrors and advance the development of mechanical cleaving processes.

Numerical simulation of RHIC polarized proton run 17 spin flipper experiments

RHIC nine-magnet spin flipper has been operated successfully during RHIC polarized proton Run 17, with 97% spin flip efficiency achieved. The results show the importance of mirror resonance removal, small spin tune spread, and proper spin flipper driving tune sweep speed. Detailed spin tracking simulations, based on a Lorentz force and Thomas-BMT differential equation numerical solver code for accuracy, have been carried out to understand the experimental results. Agreement within measurement accuracy is obtained at injection energy, 23.8 GeV. It is not as tight at 255 GeV, reasons for that are exposed. These measurements and numerical studies allow to determine the sensitivity of spin-flip efficiency to the dispersion slopes at the two Siberian snakes and to the ac dipole frequency sweep speed. They also provide guidance for future developments at BNL’s electron-ion collider. Published by the American Physical Society 2024

Random access vision: an imaging method to observe arbitrary and multiple gaze directions in frame-by-frame manner

In robot vision, it is often desired to measure an area larger than the field of view of the camera, so the camera tends to be mounted on a mechanical pan/tilt platform. However, such mechanisms have a non-negligible response time compared to the frame rate of the camera. In this paper, we describe what we believe to be a new method that allows arbitrary and multiple gaze directions to be observed in a frame-by-frame manner based on a resonant mirror and a lock-in pixel image sensor. In the proposed method, while the gaze direction oscillates due to the resonance mirror, the image sensor makes an exposure of several hundreds of nanoseconds every time the gaze passes through the direction to be captured, and accumulates the captured signals. A prototype system was developed using a lock-in pixel image sensor with four image storage units called taps and a resonant mirror with a resonant frequency of 12 kHz. The system achieved both arbitrary control of the gaze direction in a frame-by-frame manner, and simultaneous capturing of four images with arbitrary gaze directions also in a frame-by-frame manner.

Theoretical modeling and experimental investigation of in-phase resonant MEMS mirrors with cascaded structures

This paper proposes an efficient nonlinear one-dimensional (1D) compact mass-damper-spring model to predict the dynamic response of electrostatic resonant micro-electro-mechanical system (MEMS) mirrors with cascaded structures. The time-dependent damping moment due to viscous shear and pressure drag is computed using semi-empirical analytical equations for comb-drive structures and device frames. Nonlinear electrostatic force induced by the comb drives is efficiently acquired based on the hybrid method. The optimized device is fabricated using MEMS fabrication processes based on a 4-inch silicon-on-insulator wafer. The proposed compact model with the measured key parameters from the fabricated device shows excellent capability to accurately predict nonlinear dynamic responses of the fabricated device, including parametric excitation and hysteretic frequency response, with an average error of less than 5%. In particular, our 1D model is three orders of magnitude faster than the conventional finite element method model (0.8 s versus 1 h), enabling efficient system-level optimization of the critical design parameters. Based on the parametric study, electrode gap distance and torsion spring width are found to be two critical design parameters and dimensional analysis is conducted for design optimization with scan angle enhancing from 16.8° to 24° compared with the first design.

A RECONFIGURABLE METASURFACE IN THE FORM OF A FABRY-PÉROT RESONATOR, INVOLVING SEMI-TRANSPARENT MIRRORS AND A NONLINEAR DIELECTRICINSERT

Subject and Purpose. The paper is aimed at suggesting ways for implementing electromagnetic devices that would involve a nonlinear dielectric inside the structure for concentrating electromagnetic field within it at relatively low intensities of the excitation field. A representative example is offered by a Fabry-Pérot resonator with semi-transparent mirrors and a nonlinear dielectric inside. Methods and Methodology. The paper presents a fundamentally new approach to controlling the frequency response of a metasurface, and a method for protecting electronic modules from high excitation powers. The method is based on the use of nonlinear properties of a Fabry-Pérot "resonator-capacitor" containing a nonlinear dielectric in its volume. Thus, we propose a method for creating spatial filters and antenna protecting fairings capable of active reconfiguration. Results. Analysis of the results has shown that by changing the voltage across the resonator-capacitor plates it is possible to control the degree of electromagnetic field localization in the resonator volume. The frequency response of the metasurface based on the Fabry-Pérot resonator with a nonlinear dielectric inside can be reconfigured by changing the voltage applied to the resonator mirrors. The advantages provided by electrical control of the frequency-selective characteristics include an increased efficiency and possibility of integrating digitally controllable systems into antennas. Conclusions. The use of a Fabry-Pérot "resonator-capacitor"model, with a nonlinear dielectric inside, in the capacity of a reconfigurable metasurface, else as a power limiter in a variety of devices, has sufficient prospects for application in microwave transmitting systems. A special area of application for the reconfigurable Fabry-Pérot resonators is creation of broadband receive antenna systems for direction- finding. In essence, the proposed Fabry-Pérot resonator is a reflective antenna array with an ability to exhibit, conceal or alter its electrodynamic properties according to a certain algorithm. This opens up prospects for its application in "friend-or-foe" recognition systems, reflective beacons, navigation systems, etc.

Two-axial alignment mirror for optical-quantum generator resonator (Tomsk)

There are currently laser systems used at many stages of construction. They allow to solve engineering problems with great accuracy. The paper considers the design of a twoaxis alignment unit.Purpose: The aim of this work is to design the two-axial alignment mirror of the optical quantum oscillator resonator.Methodology: Deformation of elastic elements are determined by the energy method. The relation between rotation angles of the alignment screw and the resonator mirror normal is determined analytically.Research findings: The influence of design parameters of the assembly on its performance is evaluated. A comparative analysis is presented for the sensitivity of two-axial and uniaxial knots of the alignment mirror. The advantage of the two-axial knot is shown by calculations. The obtained results can be applied in laser construction technology.

Sapphire-based resonant waveguide-grating mirrors: advancing their intra-cavity power density capability

We report on the design, fabrication, and implementation of a single-layer resonant waveguide-grating (RWG) mirror on a sapphire substrate. Our goal is to enhance these optics capability to withstand high intra-cavity power densities by exploiting the superior thermal properties of sapphire. The RWG was implemented as an intra-cavity folding mirror in an Yb:YAG thin-disk laser to generate linearly polarized and spectrally stabilized radiation. A linearly polarized output power of 191 W with an optical efficiency of 39% was obtained in multi-mode operation. This corresponds to a power density of 52 kW/cm2 on the RWG, for which the increase of its surface temperature was measured to be 12 K, which resulted in a 46-fold reduction of the surface temperature rise dependence on the intra-cavity power density with respect to what has been reported for a RWG on a fused silica substrate. In near fundamental-mode operation, a linearly polarized emission with an output power of 90 W, an optical efficiency of 30%, and a spectral bandwidth of 28 pm FWHM was obtained.

Waveguide‐based Raman enhancement strategies

AbstractWaveguide‐enhanced Raman scattering (WERS) is a powerful branch of enhanced Raman technologies that has gained significant progress in recent years because of its advantages, such as reproducibility and robustness. As a complementary tool to surface‐enhanced Raman spectroscopy (SERS), WERS provides a powerful solution for reproducible quantification of analytes. According to different Raman enhancement mechanisms, five major WERS implementation strategies, namely, (1) single‐mode dielectric waveguide, (2) liquid core waveguide, (3) metal cladding waveguide, (4) resonance mirror waveguide, and (5) double metal cladding waveguide, are classified and described in detail in this review. The flexibility of WERS structures makes them easy to be integrated with 2D devices to obtain a complete on‐chip detection scheme, allowing the WERS chip to combine excitation, detection, and data analysis in integrated chips, providing a powerful prospect for real‐time and on‐site analysis of target samples. This article highlights the principles, implementations, and application scenarios of WERS techniques and evaluates their advantages and limitations, respectively. Finally, the strengths and weaknesses of WERS techniques are summarized, and promising future applications are proposed. This review provides a panoramic view for researchers interested in waveguide‐enhanced Raman technology.

Electrically Tunable Four-Mirror Gyrotron with Crossed Fields

In a four-mirror gyrotron, a wide multi-screw electron beam, being in crossed electric and longitudinal magnetic fields, drifts with a velocity vd = E0 /B0 in the direction of the T-wave propagation between the resonator mirrors (co-current wave) or in the opposite direction (counter-propagating wave). In this case, in accordance with the Doppler effect, the generation frequency ω is determined from the synchronism conditions as ω ≈ kωl(1±βd), βd = vd /с. Thus, a change in E0 changes ω, i. e. electrical frequency tuning is carried out. The article presents a diagram of the design of a two-beam four-mirror gyrotron. The calculations were carried out for βd = 0.5, q = β||/β⊥ = 2, the interaction was carried out at the frequency harmonic number k = 1. The tuning band was 20 %. The maximum efficiency is 48 %, the minimum is 33 %. Since the calculations were performed for dimensionless parameters, i.e., having a universal character, the physical characteristics of the gyrotron at a wavelength λ = 6 mm (f0 = 50 GHz) and a loaded resonator quality factor Ql = 200 were as follows: electron beam current I0 = 60 A, B0 = 2 T, voltage U0 = 79 kV, efficiency = 48 %.

Label-free image scanning microscopy for kHz super-resolution imaging and single particle tracking.

We report the modification of a label-free image scanning microscope (ISM) to perform asynchronous 2D imaging at up to 24kHz while keeping the lateral resolution gain and background rejection of a regular label-free ISM setup. Our method uses a resonant mirror oscillating at 12kHz for one-direction scanning and a chromatic line for instantaneous scanning in the other direction. We adapt optical photon reassignment in this scanning regime to perform fully optical super-resolution imaging. We exploit the kHz imaging capabilities of this confocal imaging system for single nanoparticle tracking down to 20 nm for gold and 50 nm for silica particles as well as imaging freely moving Lactobacillus with improved resolution.

Design and Characterization of a Frequency- and Amplitude-Controlled CMOS MEMS Resonant Scanning Mirror

Design and Characterization of a Frequency- and Amplitude-Controlled CMOS MEMS Resonant Scanning Mirror

Diode pumped compact single frequency cw ruby laser

Investigations on 405 nm diode-pumped cw ruby lasers operated in less than 3 mm plane-parallel resonators are reported. With 2.5 mm long ruby crystals TEM00 emission with output powers up to 40 mW are achieved. With an uncoated thin etalon of 0.13 mm thickness, single frequency emission on both ruby lines R1 and R2 is possible. With the piezoelectric shifting of one resonator mirror and corresponding tilting of the etalon, single frequency tuning of up to 400 GHz has been achieved. Details of the laser system are presented, and potential applications will be discussed.

Reflection characteristics of a cavity-resonator-integrated guided-mode resonance mirror for a microdiameter Gaussian beam.

A guided-mode resonance mirror was designed for reflecting a vertically incident Gaussian beam of 3.6-µm beam waist to a backpropagating Gaussian beam. A grating coupler (GC) is integrated in a waveguide resonance cavity consisting of a pair of distributed Bragg reflectors (DBRs) on a reflection substrate. An incident free-space wave is coupled by the GC into the waveguide, and the guided wave is resonated in the waveguide cavity and coupled out by the same GC to a free-space wave simultaneously in resonance condition. The reflection phase can vary by 2π rad, according to wavelength in a wavelength band of resonance. The grating fill factors of the GC were apodized to have a Gaussian profile in its coupling strength and resultantly maximize a Gaussian reflectance defined by the power ratio of backpropagating Gaussian beam to the incident Gaussian beam. The fill factors of the DBR were also apodized in the boundary zone to the GC in order to avoid discontinuity in equivalent refractive index distribution and resultant scattering loss. Guided-mode resonance mirrors were fabricated and characterized. The Gaussian reflectance of the mirror with the grating apodization was measured to be 90%, higher by 10% than that of the mirror without apodization. It is also demonstrated that the reflection phase changes more than π rad within wavelength band of 1nm. The fill factor apodization narrows the resonance band.

Heterogeneously integrated III–V-on-Si laser with embedded photonic molecule mirrors

We have designed, fabricated, and characterized a III–V-on-Si laser employing photonic molecule mirrors with high potential for laser tunability and control. Resonant mirrors are realized by tailoring supermodes of coupled microrings. A laser threshold of 40 mA (L-band), series resistance of 10 Ω, and side mode suppression ratio of 40 dB are demonstrated.

Compact, high-speed multi-directional selective plane illumination microscopy.

We present an elegant scheme for providing multi-directional illumination in selective plane illumination microscopy (SPIM). Light sheets can be delivered from one of two opposed directions at a time and pivoted about their center for efficient stripe artifact suppression using only a single galvanometric scanning mirror to perform both functions. The scheme results in a much smaller instrument footprint and allows multi-directional illumination with reduced expense compared with comparable schemes. Switching between the illumination paths is near instantaneous and the whole-plane illumination scheme of SPIM maintains the lowest rates of photodamage, which is often sacrificed by other recently reported destriping strategies. The ease of synchronization allows this scheme to be used at higher speeds than resonant mirrors typically used in this regard. We provide validation of this approach in the dynamic environment of the zebrafish beating heart, where imaging at up to 800 frames per second is demonstrated alongside efficient suppression of artifacts.

Study on the Acousto-Optic Coupling Effect of a One-Dimensional Hetero-Optomechanical Crystal Nanobeam Resonator

The optomechanical crystal nanobeam resonator has attracted the attention of researchers due to its high optomechanical coupling rate and small modal volume. In this study, we propose a high-optomechanical-coupling-rate heterostructure with a gradient cavity, and the optomechanical rates of the single mirror and hetero-optomechanical crystal nanobeam resonators are calculated. The results demonstrate that the heterostructure based on the utilization of two mirror regions realizes better confinement of the optical and mechanical modes. In addition, the mechanical breathing mode at 9.75 GHz and optical mode with a working wavelength of 1.17 μm are demonstrated with an optomechanical coupling rate g0 = 3.81 MHz between them, and the mechanical quality factor is increased to 3.18 × 106.