A Heterodyne Interferometer with Separated Beam Paths for High-Precision Displacement and Angular Measurements

As standard concepts for precision positioning within a machine reach their limits with increasing measurement volumes,inverse concepts are a promising approach for addressing this problem.The inverse principle entails other limitations,as for high-precision positioning of a sensor head within a large measurement volume,three four-beam interferometers are required in order to measure all necessary translations and rotations of the sensor head and reconstruct the topography of the reference system consisting of fixed mirrors in the x-,y-,and z-directions.We present the principle of a passive heterodyne laser interferometer with consequently separated beam paths for the individual heterodyne frequencies.The beam path design is illustrated and described,as well as the design of the signal-processing and evaluation algorithm,which is implemented using a System-On-a-Chip with an integrated FPGA,CPU,and A/D converters.A streamlined bench-top optical assembly was set up and measurements were carried out to investigate the remaining non-linearities.Additionally,reference measurements with a commercial homodyne interferometer were executed.

Principle demonstration of fine pointing control system for inter-satellite laser communication

Due to high data rates and reliability,inter-satellite laser communication has developed rapidly in these days.However,the stability of the laser beam pointing is still a key technique which needs to be solved;otherwise,the beam pointing jitter noise would reduce the communication quality or,even worse,would make the inter-satellite laser communication impossible.For this purpose,a bench-top of the fine beam pointing control system has been built and tested for inter-satellite laser communication.The pointing offset of more than 100rad is produced by the steering mirror.With beam pointing control system turned on,the offset could be rapidly suppressed to lower than 100 nrad in less than 0.5 s.Moreover,the pointing stability can be kept at 40 nrad for yaw motion and 62 nrad for pitch motion,when the received beam jitter is set at 20rad.

A comprehensive simulation of weak-light phase-locking for space-borne gravitational wave antenna

A comprehensive simulation was performed to better understand the impacts and effects of the additional technical noises on weak-light phase-locking for LISA. The result showed that the phase of the slave laser tracked well with the received transmitting light under different noise level, and the locking precision was limited by the phase readout noise when the laser frequency noise and clock jitter noise were removed. This result was then confirmed by a benchtop experimental test. The required LISA noise floor was recovered from the simulation which proved the validity of the simulation program. In order to convert the noise function into real time data with random characteristics, an algorism based on Fourier transform was also invented.