Detector array for measuring far-field energy density distribution of repetitively pulsed laser

Abstract

A system based on detector array is developed to measure the far-field temporal and spatial distribution and absolute pulse energy density of the laser beam. In this experiment, the duration of the laser pulse is about 15ns, the repetition rate is 400Hz, and the diameter of the far-field beam is about 60cm. The detector array is composed of 112 Si-PIN photodiode detectors and arranged to be a disk with spatial sample rate of 0.4cm -1 . Charge sensitive amplifiers and baseline restoration circuits are used to collect photocurrent of the detectors, and current-input AD converters with integrator front-end are used to digitalize the multi channel signals. The far-field laser beam profile is reconstructed with the spatial sample data using special arithmetic of spatial interpolation. The system is capable for absolutely measuring far-field energy density distribution of repetitively pulsed laser, with response wavelength between 400nm and 1100nm, minimal detectable pulse duration of about 10ns, and energy density of 0.1-100μJ/cm 2 .