The law of the polarization state of Raman fiber amplifier switch in single-core feedback structures is unknown. In this paper, two kinds of optical paths with single-core feedback structures are ...constructed, namely the Raman amplified Faraday rotating mirror single-core feedback structure (RFA-FRMOP) and the Raman amplified ordinary flat mirror single-core feedback structure (RFA-RMOP). In the process of optical signal amplification involving Raman fiber amplifiers, the polarization dependent gain (PDG) generated by Raman switches is affected by the polarization state, and RFA-FRMOP shows better stability. Surprisingly, polarization analysis of the RFA-FRMOP structure shows that both the ellipticity angle and the long-axis azimuth of the output feedback structure changed less than that of the signal entering the feedback structure. The consistency of the long-axis azimuth variation is the main characteristic of the RFA-FRMOP structure. It is found that the variation of the azimuth of the long axis of the RFA-FRMOP structure is obviously greater than that of the ellipticity. These conclusions provide a theoretical basis for the polarization dependent application of Raman fiber amplifiers in single-core feedback structures.
Quantum entanglement will play an important role in future quantum technologies. Here, we theoretically study the steady-state entanglement between a cavity field and a macroscopic rotating mirror in ...a Laguerre–Gaussian-(LG)-cavity optomechanical system with cross-Kerr nonlinearity. Logarithmic negativity is used to quantify the steady-state entanglement between the cavity and mechanical modes. We analyze the impacts of the cross-Kerr coupling strength, the cavity detuning, the input laser power, the topological charge of the LG-cavity mode, and the temperature of the environment on the steady-state optomechanical entanglement. We find that cross-Kerr nonlinearity can significantly enhance steady-state optomechanical entanglement and make steady-state optomechanical entanglement more robust against the temperature of the thermal environment.
Quantum entanglement in macroscopic systems plays an important role in quantum information processing. Here, we show that the steady-state entanglement between the two cavity modes in the macroscopic ...Laguerre–Gaussian (L–G) cavity optorotating system can be enhanced by placing a degenerate optical parametric amplifier (OPA) inside the cavity. The two L–G cavity modes are coupled to the same rotating mirror and are respectively driven at the red and blue mechanical sidebands. We use the logarithmic negativity to quantify the steady-state entanglement between the two cavity modes. We study the influences of the nonlinear gain and phase of the OPA, the temperature of the environment, and the angular momentums of the two cavity modes on the entanglement between the two cavity modes. In the cryogenic environment temperatures, when the angular momentums of the two cavity modes are identical, the enhancement of the entanglement between the two cavity modes by the OPA is the most significant.
A quantum efficiency test system based on dynamic scanning of a rotating mirror has been created to measure various linear array image sensors (referred to as linear array cameras or cameras). The ...system has been used to measure the quantum efficiency of CMOS cameras, and the uncertainty of the measurement results was evaluated. Firstly, a system consisting of a monochromatic source, a collimated optical system, a rotating mirror, and a standard detector was found. A periodic dynamic spot was generated by reflecting from the rotating mirror and was scanned by cameras. Then, the spot’s energy is captured and measured by switching the position between the camera and the standard detector. Finally, using the formula of the dynamic scanning method, the quantum efficiency of the system can be obtained. Test results show that the dynamic scanning method is feasible with high repeatability for measuring quantum efficiency. By evaluating the uncertainty of the measurement results, the system can give a quantum efficiency accuracy of 2.68%. This design provides an innovative method different from the conventional method of using a monochromator coupled with an integrating sphere, which has low accuracy. In addition, this technique can be conducted on various types of cameras.
In order to improve the tracking accuracy and robustness of the rotating mirror servo system, a modified sliding mode-active disturbance rejection control (MSM-ADRC) strategy is proposed. Firstly, ...the structure and working principle of the rotating mirror servo system are analysed, and its mathematical model is established to prepare for the design of the controller. Then, a MSM-ADRC is proposed to reduce the influence of unknown disturbance and improve the tracking accuracy. Among them, the modified sliding mode extended state observation (MSM-ESO) is designed by replacing the traditional nonlinear function with the designed optimal control function, which enhances the observation accuracy of the system state quantity and total disturbance. Meanwhile, an improved approach law is proposed, and an improved sliding mode nonlinear error feedback control law (MSM-NLSEF) is designed based on this approach law, which improves the convergence speed and accuracy of the control law. In addition, the stability of the designed MSM-ESO and MSM-NLSEF is proved. Finally, the proposed control method is validated by simulation and experimental comparison with other state-of-the-art controllers. Results reveal that the proposed control method has satisfying tracking performance and strong disturbance rejection ability.
On the basis of theory of dynamic modification and the finite element method, a numerical analysis modal of the response sensitivity of a mirror structure is established, and the influence of the ...random variables of the rotating mirror on the various order modals of the mirror is obtained. The structural size and material properties of the rotating mirror are used as random variables, and the rotating mirror feature value and feature vector are considered the response volumes. Results show that the radius R2 of axis segment 1 is the largest random variable that affects the first-order modal of the rotating mirror, the density D2 of the mirror body has the greatest influence on the first-order bending of the mirror, and the radius R3 of axis segment 2 has the greatest influence on the second-order bending of the mirror. The density of the spinning axis and mirror body are negatively correlated with each order modal, and R2 and R3 are positively correlated with the various order modals. Results provide theoretical guidance and basis for the selection of rotating mirror materials and the optimisation of the directional orientation of the dynamic parameters of a rotating mirror.
We theoretically and numerically studied the properties of a high-strength magnesium alloy rotating mirror (Mg-RM) as a novel potential candidate for an ultra-high speed camera. The maximum lateral ...deformation of the Mg-RM was reduced to 0.92 times that of a high-strength aluminium alloy rotating mirror (Al-RM) at a rotating speed of 5×105 revolutions per minute (rpm). Meanwhile, compared to the Al-RM, the limit edge linear velocity of the Mg-RM was improved by 1.11 times, indicating that the limit time resolution could be improved by 11% when used for an ultra-high speed camera. According to our theoretical and numerical investigations, the remarkable properties of the Mg-RM, indicate that the high-strength magnesium alloy is another ideal and novel RM material for ultra-high speed cameras.
We develop a novel compressive coded rotating mirror (CCRM) camera to capture events at high frame rates in passive mode with a compact instrument design at a fraction of the cost compared to other ...high-speed imaging cameras. Operation of the CCRM camera is based on amplitude optical encoding (grey scale) and a continuous frame sweep across a low-cost detector using a motorized rotating mirror system which can achieve single pixel shift between adjacent frames. Amplitude encoding and continuous frame overlapping enable the CCRM camera to achieve a high number of captured frames and high temporal resolution without making sacrifices in the spatial resolution. Two sets of dynamic scenes have been captured at up to a 120 Kfps frame rate in both monochrome and colored scales in the experimental demonstrations. The obtained heavily compressed data from the experiment are reconstructed using the optimization algorithm under the compressive sensing (CS) paradigm and the highest sequence depth of 1400 captured frames in a single exposure has been achieved with the highest compression ratio of 368 compared to other CS-based high-speed imaging technologies. Under similar conditions the CCRM camera is 700× faster than conventional rotating mirror based imaging devices and could reach a frame rate of up to 20 Gfps.
We theoretically and numerically investigated the modal properties of three different kinds of cross-section rotating mirrors. At the same facet size, the fundamental frequency of ...equilateral-triangle cross-section rotating mirror (ET-RM) was 8725.4 Hz, which was 1.81 times and 4.60 times higher than that of equilateral-square and equilateral-hexagonal rotating mirrors. The displacement response curves of the three kinds rotating mirrors show that the amplitude of the first peak is further larger than the second one. The first bending modal of rotating mirror is the main reason of the damage for rotating mirrors. The maximum working speed of ET-RM with face size of 17.32 mm × 36 mm is 44,400 rpm. That of the other two kinds of rotating mirror are 37,800 rpm and 27,000 rpm respectively. The equilateral-triangle cross-section as an ideal structure of rotating mirror for ultra-high-speed cameras based on the dynamic properties.
Effective support ways can contribute to the good performance of a large-scale optical system. An adjustable three-segment surface-contact radial support way is proposed to facilitate the movement ...process of a large-scale rotating mirror. Under a most dangerous working condition, the supporting angle is optimized by a two-step optimization method, which makes the maximum PV value reduce by 10.26% relative to that before optimization and that the maximum von Mises stress has a very little increase. Moreover, the coupling analysis of thermal stress in the rotating mirror caused by some thermal factors, such as motor heat, is carried out to validate the assembly design. The supporting way, as an effective radial mounting for dynamic optical elements, can be valuable for the reference of similar opto-mechanical design.
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