Studies and Development of Fast Imaging Devices

Abstract

Ultra short laser pulses with sub Pico second duration play important role in many applications, such as laser plasma interaction, Equation of state experiment etc. Methods enabling precise measurement of such pulse duration are therefore essential. There are various indirect measurements techniques such as auto-correlation and photo-diodes which gives only 1-D information. Common silicon photodiodes used in combination with oscilloscopes cannot be used for a precise temporal measurement because of the limited bandwidth. Therefore methods based on optical and electro-optical effect such as streak camera have been developed in the past decades and are still widely used. In contrast to the indirect method, measurement with streak camera provides direct measurement of the temporal profile of the fast optical events. Streak camera is the only device which provides 2D and 3D information. The spectral response of the S-20 streak camera ranges from 350nm-850nm, whereas spectral response for S1 streak camera ranges from 200 nm-1200 nm. The streak camera has been widely used for capillary discharge experiment, bunch length measurement of synchrotron radiation source etc. The streak camera consists of a streak tube and an image intensifier tube followed by CCD. The operation of streak camera can be developed in three modes viz. static mode, gate mode and dynamic mode. In static mode the testing of various electrodes is checked by applying suitable DC voltages to them. For this purpose high voltage biasing network will be developed. Gated mode operation is introduced in order to improve the signal to noise ratio. For this purpose Micro Channel Plate (MCP) of the image intensifier tube will be activated with a gated signal. In dynamic mode streak camera is operated in streak mode for capturing streak images. For this purpose a high voltage fast and linear ramp voltages will be generated along with a beam bias unit to select the desired linear portion of the ramp. The streak image will be captured with a synchronized CCD camera and frame grabber combination. The images thus obtained will be displayed, analyzed and corrected using LABVIEW software. The schematic diagram as well as PCB layout will be fabricated using ORCAD software.