We are concerned with the similarity and scaling law of the thermal effects of windows subjected to laser propagation and influences on laser beam quality. Using characteristic physical quantities and dimensionless equations, appropriate similarity relations are derived, independent of the specific properties of the materials and beams. As an example, a full-scale and a half-scale window are numerically analyzed to verify the relations. It is concluded that the phase aberration resulting from thermal deformation and thermo-optic effects comply completely with similarity-based scaling, while the phase aberration resulting from elasto-optic effects scales approximately. From the results of a model window, the performances of a full-scale window can be obtained using the similarity relations.

Wave activities in tailward flows have been explored in the distant magnetotail at ~54 RE, where the coupling between whistler mode waves and ion‐scale waves was observed. The whistler mode waves periodically appeared at each cycle of the ion‐scale waves, and the electron distribution functions associated with the whistler mode waves showed enhancement in the direction parallel to background magnetic field. Wave analyses show that the field‐aligned electron components act as the energy source of the whistler mode waves. The ion‐scale waves are generated by the interaction of the hot ion beam with background ions. A likely candidate of the ion‐scale wave is the kinetic Alfven wave, which can generate the enhanced field‐aligned electron populations by the parallel electric field.

EasyLaser is component-based laser system simulation software. Beam control system simulation is a main part of EasyLaser, which can be used for systems with multi-optical paths, multi-wavelength beams, and multi-controllers. A new numerical method about general kinematics separation is proposed for beam control system simulation. It provides axis rotation conversion relationships due to orientation data of apparatus of system, such as gimal, sensor and optical mirror. It gives their coupling and uncoupling matrixes in kinematics and controller model. The matrixes could change every iterative time automatically during the dynamic tracking process. The main advantage of the method is more suitable to solve the problems that the gimbal movement and geometry optical transmission are considered simultaneously. By using the method, sensor images and undershoot data are updated automatically. And further the kinematic driver or controller signals are separated automatically. Therefore the tracking and beam control can be designed without consideration of the system kinematical composition. Then the beam control system simulation has the virtues of generality, flexibility, and usability. No matter what kinds of gimbal and optical path, designer needs only to consider tracking and beam control aspects. In addition, a union beam control example for atmosphere transmission correction is given. It includes tracking tilt mirror and adaptive optics system. Simulation results show that the low-frequency fluctuation is restrained effectively and the high-frequency fluctuation is corrected obviously.

High-energy laser systems include an optical train and a gas medium that must be capable of transporting and directing the beam. The optical train is termed a laser beam tube. Because of the finite absorption of laser energy, the thermal effects of the beam tube make the beam diffuse and cause degradation of the laser beam's quality. We study systematically a beam tube consisting of a laser window made from white bijou (i.e., Al2O3) or fused silica and a tube of nonflowing nitrogen or helium gas. The results show that the thermal effects of the window and the gas on the beam neutralize each other; in particular, in some cases they compensate for each other completely, such that the beam tube has no effect on the beam quality in spite of the fact that separately each has a severe effect. We explain how to acquire the specific cases.

Abstract-Pointing on a certain point of a dynamic target is demanded by beam director system. Compound-axis servo system must be adopted. A component-based compound axis servo system simulation method is proposed, denoted as the CCASS method. Compound-axis tracking system simulation is an effective expansion on EasyLaser, a primary general software platform for laser system simulation. The circumstance nest of Matlab/Simulink makes the CCASS method adaptive to concrete transfer function as well as complex control system. Furthermore, CCAS method aims at searching out a solution for coupling and decoupling simulation of the main-axis and the sub-axis servos, because there are kinematics coupling and driver decoupling problem in a general beam director. Otherwise, a joint simulation with adaptive optical system is derived, which improves tracking precise forwardly. By CCAS method, no matter how the detectors and controlled mirrors are sited in the optical path, kinematical coupling and driver decoupling are resolved automatically. Simulation results indicate that the proposed CCAS method has the capacity of retaining simulative quality and enhancing the simulative facility and adaptability.