The approximate Strehl Ratio expressions that need only the wave phase distribution is not appropriate in the laser fusion system when the phase has great aberration. The accurate Strehl Ratio value need both the phase and the amplitude distribution information. The paper provide a method of reconstructing wave phase and amplitude
distribution by a single radial shearing interferogram. The radial shearing interferometer based on spatial phase modulation is simple and stable, needs only one interferogram. The principle and structure of cyclic radial shearing interferometer are briefly discussed and the process of spatial phase modulation, Fourier transform method and wavefront reconstruction are analyzed. It also illluminates the physical meaning and establish the mathematical model. The process of getting SR value is simulated by computer. The simulation result indicates that the RMS error of the reconstructing wavefront can achieve λ/100.
VISAR is an effective tool to measure very high-speed motion objects. However, because of the limitation of response speed of the detector, it is unable to resolve the number of shifting fringes in
a very short time at the beginning of motion of the object, which lead to a question of fringe lost. The Double-sensitivity VISAR is one of ways to solve the question. In this article, we advance an
improved double-sensitivity VISAR that only uses a set of velocity interferometer and detection system.
It is an important part to measure the distortion and divergence of laser pulse wavefront in ICF (Inertial Confinement Fusion). The paper described a radial shearing interference system with spatial phase modulation. It can be used for testing the wavefront distortion and control the beam quality. Because it is a cyclical common path interference system and no any reference surface, both radial sheared wavefront are formed by a Galilean optical system. A 512x512 pixels CCD camera recorded interference pattern. The wavefront reconstructed is finished by means of optical information processing method and software. The software procedure consists of the Fourier transform, shifting frequency, inverse Fourier transform, unwrapping 2π and wave iterations reconstructed. The interferometer has been used for testing a wavefront distortion of laser pulse with 1064nm near-infrared wavelength and 10 ns pulse time width. Results of the pulse wavefront quality and distribution of energy can be displayed by a perfect software procedure. Diameter of beam be measured is up to 150 mm. The testing precision of RMS(root-mean-square) is better than 1/15 wavelength.