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We demonstrated a 20.97 GHz regeneratively mode-locked Er fiber laser that has a short ring length of 5.84 m. The short active ring enabled large filter-rejection of adjacent supermodes during extraction of its clock signal for regenerative feedback. Very stable mode locking was observed with the generation of ∼5.5ps Gaussian pulses. [https://www.selleckchem.com/products/zebularine.html this website] A characterization of the noise pedestals in the photodetected first and second harmonics of the mode-locked pulses indicated there was cross-correlated coupling between the timing and amplitude jitter. From an analysis of the noise pedestals in these harmonics, as well as the noise spectrum at baseband, we estimated an amplitude jitter of ∼0.19%, and a timing jitter of ∼60fs. Using a generalized harmonic analysis approach, we estimated a cross correlation of 0.11% between the timing and amplitude jitter.For passive support of large aperture telescopes, geometric layout optimization of the support structure is one of the most critical tasks because it determines the deformation of the mirror under gravity, which affects the wavefront aberration and image quality of the system. Due to a lack of symmetry, the optimization of an elliptical mirror support can be much more complex compared with circular mirrors. We optimize the geometric layout of axial and lateral support for the tertiary mirror of the Thirty Meter Telescope (TMT). Based on a theoretical analysis of the whiffletree principle, a parametric model of axial support is established based on the multi-point constraint equation. The mirror deformation SlopeRMS of the tertiary mirror under vertical gravity is used as the optimization target of the support points. The axial support point position is optimized by means of a simulated annealing algorithm and a mirror-deformed post-processing script written in Python. The TMT tertiary mirror lateral support also uses the whiffletree structure, and its in-plane layout affects the system's resonant modal frequency and the maximum load at each point. According to the dynamic equation and the static principle, the lateral support optimization model is established. The first-order resonant frequency and maximum load of the support point are the objective function. Through optimization of the axial and lateral support, the overall mirror distortion of the system is improved.A traditional beacon location method is difficult to apply to a deep space optical communications link due to the high laser power required for long distances. The use of natural celestial bodies as beacon images can solve this problem. The correct location of the beacon is critical to establish and maintain an optical communications link. Therefore, in this paper we propose an approach to determine the location of a natural celestial beacon. To identify a beacon in an uncertain region, the phase correlation between the detected and reference images is applied. The influence of an image translation is eliminated through a Fourier transform, and the scaling and rotation are converted into the translation and solved using a log-polar transformation and phase correlation, respectively. The availability of a new approach is verified by the experiment. A field-programmable gate array embedded processing system is designed to realize the proposed algorithm. When the image noise is considered, the success probability of the algorithm can reach more than 96%. We believe this work is beneficial for deep space optical communications system design.In the present work, we analyze acousto-optic (AO) interactions between acoustic waves (AW) and circularly polarized optical eigenwaves in gyrotropic crystals. We find that the AO diffraction of circularly polarized eigenwaves can be divided into six different interaction types. Contrary to the AO interactions analyzed earlier for the case of linearly polarized optical eigenwaves, we distinguish three isotropic interaction types and three anisotropic ones. Moreover, unlike the isotropic AO interactions of linearly polarized eigenwaves of no-no and ne-ne interaction types, the effective elasto-optic coefficient (EEC) in the case of interactions between circularly polarized eigenwaves does not depend on the sign of an incident circular optical wave. The anisotropy of the EEC and AO figure of merit is analyzed for a particular case of lead germanate crystals, Pb5Ge3O11. We demonstrate that the maximal AO figures of merit are achieved for type I isotropic diffraction at the quasi-longitudinal AW. Our calculations are confirmed by the experimental data obtained for the EEC using the Dixon-Cohen method. The experiment is concerned with the AO interactions of circular eigenwaves in Pb5Ge3O11.Two-dimensional-material-based photodetectors are gaining prominence in optoelectronic applications, but there are certain factors to consider with bulk material usage. The demand for a highly responsive and highly efficient device with an inexpensive fabrication method is always of paramount importance. Carbon nanotubes (CNT) are well known, owing to their upheld vigorous structural and optoelectronic characteristics, but to fabricate them at a large scale involves multifarious processes. A visible range photodetector device structure developed using a simple and inexpensive drop-casting technique is reported here. The optoelectronic characteristics of the device are studied with IV measurements under the light and dark conditions by incorporating a thin CNT layer on top of tungsten-disulfide-based heterojunction photodetector to enhance the overall characteristics such as detectivity, responsivity, photocurrent, rise time, and fall time in the visible range of the light spectrum with a violet light source at 441 nm. In the DC bias voltage range of -20 to 20 V, IV measurements are carried out under dark and illumination conditions with different incident power densities. The threshold voltage is recognized at 2.0 V. Photocurrent is found to be highly dependent on the state of the incident light. For 0.3074mW/cm2 illuminated power, the highest responsivity and detectivity are determined to be 0.57 A/W and 2.89×1011 Jones. These findings encourage an alternative fabrication method at a large scale to grow CNTs for the enhancement of optoelectronic properties of present two-dimensional-material-based optoelectronic and photonics applications.