Variable Beam Expander Research Articles

Variable magnification beam expander system based on semiconductor laser

Due to the different divergence angles in two perpendicular directions and the presence of astigmatism in edge-emitting semiconductor lasers, the communication distance and efficiency of underwater communication are seriously affected. Therefore, based on the fact that the semiconductor laser beam belongs to Gaussian beam, satisfying Gaussian characteristics and collimating and expanding characteristics, a system composed of fast-axis collimation mirror and variable magnification beam expander is designed. Simulation is performed, and the final divergence angle is calculated. Experimental results show that the divergence angles of the fast axis and the slow axis have been compressed from 49 and 9, respectively, to 0.315 mrad and 0.180 mrad. Simulation demonstrates that the system can achieve propagation over a distance of 100m underwater and solve the alignment difficulty of APT. The designed structure is compact, easy for processing and adjustment, with high practical value, which helps to solve the problems of optical energy loss and low coupling efficiency in underwater long-distance communication.

A continuously variable beam expander driven by ultrasonic motors.

A dynamic beam shaping system requires a variable beam expander. Three optical lenses form the core of the proposed beam expander, and two hollow ultrasonic motors are used to adjust the positions of two of the lenses. A polymer-based stator is introduced in the ultrasonic motors to decrease their weight, whereupon a prototype is machined and its performance is assessed. The beam expander starts and stops within 0.05 s, and the minimum positioning error is 0.03 µm by adjusting the motor speed. The presented expander can continuously expand a laser beam by between threefold and fivefold, and nanoscale positioning and high-precision beam shaping are realized by using ultrasonic motors as its actuators.

Focus on spectroscopy and photonics

Focus on spectroscopy and photonics

APPLICATION AND PERFORMANCE EVALUATION FOR THE DMS SYSTEM IN THE SLS PROCESS

A Solid Freeform Fabrication (SFF) system using Selective Laser Sintering (SLS) is currently recognized as a leading process and SLS extends the applications to machinery and automobiles due to the various materials employed. Especially, accuracy and processing time are very important factors when the desired shape is fabricated with Selective Laser Sintering (SLS), one of Solid Freeform Fabrication (SFF) system. In the convectional SLS process, laser spot size is fixed during laser exposing on the sliced figure. Therefore, it is difficult to accuracy and rapidly fabricates the desired shape. In this paper, to deal with those problems a SFF system having ability of changing spot size is developed. The system provides high accuracy and optimal processing time. Specifically, a variable beam expander is employed to adjust spot size for different figures on a sliced shape. Therefore, design and performance estimation of the SFF system employing a variable beam expander are achieved and the mechanism will be addressed to measure the real spot size generated from the variable beam expander. Also, the reduction of total processing time is an important issue in SFF system. A digital mirror system (DMS) is a system which scans the laser beam with different spot size. The spot size is selected based on the slicing section to decrease and accuracy of the process time and improve the processing efficiency. In this study, the optimal scan path generation for DMS will be addressed, and this development will improve the whole processing efficiency and accuracy through the scan efficiency by considering the existing scan path algorithm and heat energy distribution.

New Fluorescence Correlation Spectroscopy Enabling Direct Observation of Spatiotemporal Dependence of Diffusion Constants as an Evidence of Anomalous Transport in Extracellular Matrices

The potential of fluorescence correlation spectroscopy (FCS) is extended to enable the direct observation of anomalous subdiffusion (ASD) in inhomogeneous media that are of great importance particularly in many biological systems, such as membranes, cytoplasm, and extracellular matrices (ECMs). Because ASD can be confirmed by monitoring the spatiotemporal dependence of observable diffusion coefficients (D(obs)), the size of the effective confocal volume (V(eff)) for FCS sampling (sampling volume) was continuously changed on a scale of 300-500 nm using a motorized variable beam expander through which an illuminating laser beam passes. This new method, namely, sampling-volume-controlled (SVC)-FCS, was applied to the analysis of hyaluronan (HA) aqueous solutions where the D(obs) of light-emitting solute (Alexa 488) markedly changed, corresponding to the change in V(eff) (220-340 nm in the half-axis), because the network structure of HA of 7-33 nm (nanostructure) interferes with the material transport within it. The results indicate that moderate ASD may occur even in the presence of a small amount ( approximately 0.1 wt %) of HA in ECM. Because the change in D(obs) along with the traveling distance (the mean-square displacement) can be identified even in systems with no deformation of the autocorrelation function, this technique has a great potential for general applications to many biological systems in which ASD shows complex time and space dependences.