Dazzler

Abstract: A novel method for high power optical amplification of ultrashort pulses in IR wavelength range (0.7-20 Am) is disclosed. The method is based on the optical parametric chirp pulse amplification (OPCPA) technique where a picosecond or nanosecond mode locked laser system synchronized to a signal laser oscillator is used as a pump source or alternatively the pump pulse is created from the signal pulse by using certain types of optical nonlinear processes described later in the document. This significantly increases stability, extraction efficiency and bandwidth of the amplified signal pulse. Further, we disclose five new practical methods of shaping the temporal and spatial profiles of the signal and pump pulses in the OPCPA interaction which significantly increases its efficiency. In the first, passive preshaping of the pump pulses has been made by a three wave mixing process separate from the one occurring in the OPCPA. In the second, passive pre-shaping of the pump pulses has been made by spectral filtering in the pump mode-locked laser or in its amplifier. In the third, the temporal shape of the signal pulse optimized for OPCPA interaction has been actively processed by using an acousto-optic programmable dispersive filter (Dazzler) or liquid crystal light modulators. In the fourth alternative method, the signal pulse intensity envelope is optimized by using passive spectral filtering. Finally, we disclose a method of using pump pulses which interact with the seed pulses with different time delays and different angular orientations allowing the amplification bandwidth to be increased. In addition we describe a new technique for high power IR optical beam delivery systems based on the microstructure fibres made of silica, fluoride or chalcogenide glasses as well as ceramics. Also we disclose a new optical system for achieving phase matching geometries in the optical parametric interactions based on diffractive optics. All novel methods of the ultrashort optical pulse amplification described in this disclosure can be easily generalized to other wavelength ranges.

Abstract: We report the design, implementation, and characterization of a grism-pair stretcher in a near-infrared noncollinear optical parametric chirped-pulse amplifier (OPCPA) that is capable of controlling a bandwidth of 440 nm. Our dynamic dispersion control scheme relies on the grism stretcher working in conjunction with an acousto-optic programmable dispersive filter (Dazzler) to jointly compensate large amount of material dispersion. A spectral interference technique is used to characterize the spectral phase of the grism stretcher. This ultra-broadband device opens up the way to generate sub-2-cycle laser pulses.

Abstract: We report the recent progress on the Shanghai Superintense Ultrafast Laser Facility (SULF) project. The schematic design of SULF is described. The upgrade information from SULF laser prototype to SULF 10 PW laser user facility is presented in detail. A high contrast front is developed to generate high-quality clean seed pulses which are then stretched to about 2 ns by a new double-grating Offner stretcher. A Dazzler is used to control the high-order phase distortions and shape the spectrum of the laser pulses simultaneously. The laser pulses are amplified to 7 J energy in the 1 Hz pre-amplifiers system before injected into the three stages large aperture main amplifiers system. The first two main amplifiers are pumped by five commercial lasers which can be operated at 1 shot/min. The final main amplifier is pumped by six home-built high energy frequency doubled Nd:glass lasers at a repetition rate of 1 shot/3 min. The final amplifier output energy is ~408 J with high stability under a pump energy of ~530 J. Compressed pulse duration of the amplified laser and the total transport efficiency for compression is measured to be 22.4 fs and 70.52% respectively. The experimental results demonstrate that SULF user facility has the capacity to deliver 10 PW peak power femtosecond pulses.

Abstract: A simple model has been developed and implemented in Matlab code, predicting the over-exposed pixel area of cameras caused by laser dazzling. Inputs of this model are the laser irradiance on the front optics of the camera, the Point Spread Function (PSF) of the used optics, the integration time of the camera, and camera sensor specifications like pixel size, quantum efficiency and full well capacity. Effects of the read-out circuit of the camera are not incorporated. The model was evaluated with laser dazzle experiments on CCD cameras using a 532 nm CW laser dazzler and shows good agreement. For relatively low laser irradiance the model predicts the over-exposed laser spot area quite accurately and shows the cube root dependency of spot diameter on laser irradiance, caused by the PSF as demonstrated before for IR cameras. For higher laser power levels the laser induced spot diameter increases more rapidly than predicted, which probably can be attributed to scatter effects in the camera. Some first attempts to model scatter contributions, using a simple scatter power function f(θ), show good resemblance with experiments. Using this model, a tool is available which can assess the performance of observation sensor systems while being subjected to laser countermeasures. © 2014 SPIE.