REGIONAL ATMOSPHERIC PROFILING CENTER FOR DISCOVERY

DIfferential Absorption Lidar

DIAL PHOTO GALLERY

CURRENT RESEARCH

The Huntsville transmitter consists of two identical dye lasers pumped by separate Nd:YAG lasers.  The characteristics of the DIAL system are listed in Table 1. Each pump laser has a fundamental wavelength of 1064 nm, electro-optically Q-switched at 20 Hz using a plate polarizer, quarter waveplate, and pockels cell. Each pulse is 5-7 ns Full Width at Half Maximum (FWHM) with a line-width of 1.0 cm-1 and ~300 mJ of optical power. The output of each pump laser is frequency doubled by angle tuned Potassium Dihydrogen Phosphate (KDP) crystals. The fundamental and frequency doubled pulses (532 nm) are separated using dichroic mirrors (separators) where the fundamental is transmitted and absorbed by a beam dump.  The 532 nm pulses are reflected and redirected for use as a pump source for each tunable, pulsed, dye laser as shown in Fig. 1.  The dye lasers are software controlled with external computer systems that select the user defined wavelength by rotating a reflection grating used to select a wavelength to be amplified in the master oscillator.  The dyes used as the gain medium are Rhodamine (R) 590 and 610.  R590 is used to produce 570 nm output and a combination of both R590 and R610 is used to produce 582nm output. The output of each dye laser is frequency doubled using a Beta Barium Borate (BBO) crystal to produce pulses with energies of 3-5 mJ at 285 and 291nm and a divergence less than 1mrad.  The divergences of both laser beams have been checked using a knife edge method (33). UV mirror configuration separates the UV pulses from their visible fundamentals while redirecting the UV pulses to a turning mirror which is aligned to reflect the pulses vertically into the atmosphere. Each laser pulse is externally triggered by a function generator #1 such that there is a 25 ms temporal separation between the firing of alternate pulses.