Laser-induced damage (LID) to optical glass has become a growing problem in high-power laser systems. It is well known that the main reason of glass being damaged is due to defects and impurities in the material. Damage caused by subsurface defects (SSDs) is especially common in actual system running. Accordingly, in the presence of SSDs, a simple and alternative calculation method is developed to evaluate the enhancement of light field around the incident and exit surface. This ray tracing approach, based on the classical optics theory, is very direct and clear to show the optical phenomena of light intensity enhancement. Some basic SSD shapes have been studied and investigated here, which reveals the importance and boundary condition of controlling the size and density of SSDs in grinding and polishing process. Finally, to achieve optimal breadth depth ratio, the least etching amounts by hydrofluoric (HF) acid is investigated. The theoretical analysis and simulation results provide an appropriate range of removal amounts, which is very important in the HF etching process.
A 100 W-class all-fiber linearly-polarized single-mode fiber laser at 1120 nm with an optical pump efficiency of 50% was demonstrated. Linearly polarized output with a polarization extinction ratio of 15 dB is achieved by a cavity that selects both wavelength and polarization. Macro pulse operations with square shaped pulses from 100 μs to 1 ms are achieved without relaxation oscillation. The exact wavelength of pump diode is found to be crucial for amplified spontaneous emission and parasitic oscillation in high power 1120 nm fiber laser. Effects of inhomogeneous spectral broadening and temperature dependent absorption are proposed to explain experimental observations.
Because PAT (pointing-acquisition-tracking) parameters and integrated technical specifications of laser communication terminals for inter-satellite link must be pre-verified and assessed thoroughly on a ground-based test-bed before launched into the space, it is necessary to develop a system as a primary part of the test bed to simulate the relative trajectory between the satellites. In this paper, an original high-precision satellite relative-trajectory simulating servosystem is introduced in detail as well as its structures and characteristics. The system is used to simulate the motion of relative-trajectory between satellites in different orbits. The principle of the system is to import the data of two satellites’ orbits into a computer-based control system in advance. After processed and analyzed, the data is transformed into the angular displacement of the servomotor which drives the gimbal directly. The angular displacement of the two axes of the gimbal can simulate precisely the relative-trajectory, namely elevation angle and azimuth angle of the two satellites in communication. A laser communication terminal mounted on the gimbal then performs the PAT mechanisms to evaluate the system’s capacity.
There is often large optics of several hundreds millimeters aperture in the laser communications transceiver which is nearly diffraction-limited laser beam at the same time. A revised Mach-Zehnder double-shearing interferometer is designed with 300 millimeters aperture which can be used for wave front analysis. Compare to the aperture-divided double lateral-shearing interferometer presented before, which is based on Jamin interferometer, this structure is easy to achieve for large aperture measurement without thick Jamin plates. In this paper, the interferometer with six same size plates is explained. One plate of them occupied as reflection is aperture-divided. Three changeable schemes are attained to get different wave front measurement ranges through adjusting angle between half-aperture plates. The interferometer is a white light interferometer. The interferometer is so designed that the equal optical path interference is hold though the shear is changing. It is useful for the short coherent length such as laser diode. The wave front aberration is deduced from the interferogram. The calibration is important especially for the Mach-Zehnder structure. Here two interferometers are adopted. One is Fisuea type used for parallel or angle adjustment, another generates plane wave better than 0.2λ with the laser and the high-quality plates. The method to use these apparatus is also explained in detail.