Multi-wavelength beam profile analysis of near-infrared nanosecond pulses

We report on measurements of beam profiles of near-infrared idler pulses from an optical parametric oscillator (OPO) using an infrared (IR) camera for wavelengths ranging from 1850 nm to 2050 nm, wavelengths of particular interest for optical pumping of mid-IR semiconductor lasers. The observed variations in the intensity profiles recorded correlate well with the decrease in idler intensity and simultaneous increase in IR camera sensitivity as the output wavelengths increase from 1850 nm to 2050 nm. Data is collected in both unsynchronized and synchronized configurations of the OPO and camera. Synchronization of the pump beam and camera is shown to increase the measured intensity of the output beam and also to reduce pixel-to-pixel intensity variation. Choice of an appropriate threshold value is seen to be more critically important at wavelengths where the signal is low. We are able to distinguish and track the peak center position as it varies with wavelength. The technique presented is applicable to beam profile measurements in the near-infrared not readily accessible by CCD and streak cameras or other existing instrumentation. It is the first step in the development of a technique for synchronizing and correlating spatio-temporal measurement of optical pump and output beams in the near- and mid-IR.