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To address the challenge of laser beam distortion induced by thermal effects in high-power slab laser amplifiers, a coupled thermal–mechanical–optical model for a face-pumped Yb:YAG multi-pass amplifier was developed. The thermal effects under different thermal management strategies were systematically investigated using the finite element method. Firstly, the temperature distribution, thermal stress, and deformation within the Yb:YAG crystal were analyzed and compared under both room-temperature (293 K) and cryogenic (150 K) cooling conditions using a microchannel cooling structure. The results demonstrate that under a pump power of 100 W and room-temperature cooling, the peak temperature of the gain medium reaches 363 K, with a peak thermal stress of 1.04 MPa and a maximum thermal deformation of 1.44 μm. In contrast, under cryogenic cooling at 150 K, the maximum temperature is reduced to 188 K, and both thermal stress and deformation exhibit a more uniform distribution within the pumped region. Subsequently, the thermal lensing of bonded and non-bonded Yb:YAG crystals was compared and analyzed by ray-tracing. It was found that under a pump power of 100 W, the thermal focal lengths of non-bonded Yb:YAG are 1112 mm and 2559 mm at cooling temperatures of 293 K and 150 K, respectively. For bonded crystals with a 3 mm undoped YAG thickness under identical pumping and cooling conditions, the corresponding thermal focal lengths measure 1508 mm and 3044 mm. When the undoped YAG thickness increases to 6 mm, the thermal focal lengths further extend to 1789 mm and 4206 mm, respectively.

We present a spatiotemporal model of pulse amplification in the double-pass active mirror (AM) geometry. Three types of overlap condition are studied, and the spatiotemporal scaling under the four-pulse overlapping (4PO) condition is fully characterized for the first time, by mapping the temporal and spatial segments of beam to the instantaneous gain windows. Furthermore, the influence of spatiotemporal overlaps on the amplified energy, pulse distortion and intensity profile is unraveled for both AM and zigzag configurations. The model, verified by excellent agreement between the predicted and measured results, can be a powerful tool for designing and optimizing high energy multi-pass solid-state laser amplifiers with AM, zigzag and other geometries.

In this paper, we will discuss the performances of a 4-pass diode-pumped 4-active-mirrors laser amplifier. Numerical simulations along with experimental characterization paves the way to reach 1 J at 10 Hz pulse rate at 1053 nm. Both Nd :glass and Nd :Lu :CaF 2 amplifier medium performances will be compared in this amplifier.

The Wide Field Survey Telescope (WFST) is a dedicated photometric surveying facility being built jointly by University of Science and Technology of China (USTC) and the Purple Mountain Observatory (PMO). It is equipped with a 2.5-meter diameter primary mirror, an active optics system, and a mosaic CCD camera with 0.73 gigapixels on the primary focal plane for high-quality image capture over a 6.5-square-degree field of view. The installation of WFST near the summit of Saishiteng mountain in the Lenghu region is scheduled in summer of 2023, and the operation is planned to start three months later. WFST will scan the northern sky in four optical bands ( u, g, r and i ) at cadences from hourly/daily in the deep high-cadence survey (DHS) program, to semi-weekly in the wide field survey (WFS) program. During a photometric night, a nominal 30 s exposure in the WFS program will reach a depth of 22.27, 23.32, 22.84, and 22.31 (AB magnitudes) in these four bands, respectively, allowing for the detection of a tremendous amount of transients in the low- z universe and a systematic investigation of the variability of Galactic and extragalactic objects. In the DHS program, intranight 90 s exposures as deep as 23 ( u ) and 24 mag ( g ), in combination with target of opportunity follow-ups, will provide a unique opportunity to explore energetic transients in demand for high sensitivities, including the electromagnetic counterparts of gravitational wave events, supernovae within a few hours of their explosions, tidal disruption events and fast, luminous optical transients even beyond redshift of unity. In addition, the final 6-year co-added images, anticipated to reach g ≃ 25.8 mag in WFS or 1.5 mags deeper in DHS, will be of fundamental importance to general Galactic and extragalactic science. The highly uniform legacy surveys of WFST will serve as an indispensable complement to those of the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) that monitors the southern sky.

In order to design an active deformation mirror for projection objective aberration imaging quality control, a topology optimization design method of active deformation mirrors based on discrete orthogonal Zernike polynomials is proposed in this paper. Firstly, in order to solve the problem that continuous Zernike polynomials do not have orthogonality on the discrete coordinates inside the unit circle, which causes the instability of topology optimization results, discrete orthogonal Zernike polynomials are used to characterize the active deformation mirror wave aberrations. Then, the optical and structural deformations are combined to establish an optical-mechanical coupling topology optimization model with the help of the variable density method to derive the sensitivity of the mathematical model. Finally, a wave aberration corrected deformation mirror in an optical machine system is used as an arithmetic example for topology optimization, and the results show that the absolute value of the Zernike coefficient Z4 after optimization is improved by nearly one order of magnitude compared with the value before optimization, and the vibration characteristics of the optimized structure meet the design requirements. The optimization effect is significant, which improves the optical performance of the deformed mirror and provides a new scheme for the design of the deformed mirror structure which has a certain practical value for engineering.

Timescale comparison between optical atomic clocks over ground-to-space and terrestrial free-space laser links will have enormous benefits for fundamental and applied sciences. However, atmospheric turbulence creates phase noise and beam wander that degrade the measurement precision. Here we report on phase-stabilized optical frequency transfer over a 265 m horizontal point-to-point free-space link between optical terminals with active tip-tilt mirrors to suppress beam wander, in a compact, human-portable set-up. A phase-stabilized 715 m underground optical fiber link between the two terminals is used to measure the performance of the free-space link. The active optical terminals enable continuous, cycle-slip free, coherent transmission over periods longer than an hour. In this work, we achieve residual instabilities of 2.7 × 10 −6  rad 2  Hz −1 at 1 Hz in phase, and 1.6 × 10 −19 at 40 s of integration in fractional frequency; this performance surpasses the best optical atomic clocks, ensuring clock-limited frequency comparison over turbulent free-space links. Atomic clocks and their networks are useful tools for optical communications and frequency metrology. Here the authors use phase stabilization and active tip-tilt to suppress atmospheric effects and enable optical frequency transfer through free-space.

The Optics & Metrology group at Diamond Light Source has recently published a description of a bimorph deformable X-ray mirror operating in closed-loop using multi-beam interferometric feedback. This “adaptive” mirror can make fast and stabilised changes to the X-ray beam profile. Beam shaping at a rate of 1 Hz was achieved, a contrast to the now usual “set and forget” operation of “active” bimorph mirrors at synchrotrons. However, this breakthrough cannot be applied to synchrotron beamlines without a robust control system that allows the mirror to be rapidly and controllably deformed. Diamond has now responded to this need by taking an integrated approach, considering: the bimorph power supplies, the beamline control software, the beam imaging camera, the bimorph mirror optimisation software, and the bimorph mirror itself as part of a single system. In collaboration with CINEL, new HV-ADAPTOS high-voltage power supplies have been made available. The latest models contain new firmware that adds features not previously available, such as piezo-elastic creep compensation. Communication with the HV-ADAPTOS power supplies over Ethernet has been made more reliable by a new EPICS asynPortDriver interface developed at Diamond and rolled out to all appropriate Diamond beamlines. A new Bluesky/Ophyd plan for the measurement of the bimorph mirror’s piezo response functions is under development and has undergone its preliminary tests. This plan is expected to be less affected by upgrades of the beamline control software than previous solutions. It relies on beam images produced by Gigabit Ethernet cameras and processed by the EPICS areaDetector driver. Finally, the need for strain-free clamping of the mirror has now been fully recognized and procedures for ensuring it have been put into practice. Although such a system is more complex than that required for a mechanically bent mirror, it gives bimorph mirrors an ability to operate rapidly and repeatably that other optics do not offer, and it lays a foundation for more advanced beam-shaping functions.

In this work, active current mirrors using sensing resistors and a pass transistor in a feedback loop will be examined in detail. First, several non-idealities in this family of circuits, such as offset, noise, output impedance, or bandwidth, are addressed, showing no performance degradation under certain circumstances. Then, the design and measurement results of a 10- μ A (nominal) active current mirror that can operate down to just 80 mV voltage drop are presented. Finally, two simple amplifier stages using classic and active current mirrors are compared, the latter operating almost at a third of the supply voltage. It is possible to conclude that active current mirrors can be a very valuable building block for low-voltage analog circuits.

Addressing the demand for high stability of beamline instruments at the SHINE facility, a high stability mirror regulating mechanism has been developed for mirror adjustments. Active mass damping was adopted to attenuate pitch angle vibrations of mirrors caused by structural vibrations. An internal absolute velocity feedback was used to reduce the negative impact of spillover effects and to improve performance. The experiment was conducted on a prototype structure of a mirror regulating mechanism, and results showed that the vibration RMS of the pitch angle was effectively attenuated from 47 nrad to 27 nrad above 1 Hz. Active damping with internal absolute velocity feedback was implemented to damp the angular vibration of a mirror holder for free‐electron laser beam transportation.

An ambient pressure / UHV X-ray photoelectron spectroscopy beamline is designed to study critical physical and chemical processes, including catalysis, energy storage, and environmental science. The source of the beamline is from an elliptically polarizing undulator to cover the photon energy range from 200 to 3000 eV. In this optical design, the grating paired with the active mirror is applied to improve the impact of the optical aberrations and keep the light at the exit slit in focus. All parameters of optical components at the beamline are verified by a ray-tracing method and the expected performances are discussed.