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SCHLIEREN PHOTOGRAPHY USING A MODE-LOCKED LASER AS THE LIGHT SOURCE,
NATIONAL RESEARCH COUNCIL OF CANADA OTTAWA (ONTARIO) DIV OF PURE CHEMISTRY
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The extremely short pulses of coherent radiation emitted by a mode-locked laser permit the extension of conventional Schlieren photography to events requiring exposure times of a few picoseconds and framing rates in the gigacycle range. The usefulness of this technique has been investigated by studying the initial development of a laser-produced plasma. The experimental set-up employed a Neodymium glass laser, Q-spoiled by means of a saturable dye, emitting a 400 nsec long train of pulses having a separation of 4nsec and a duration of approximately 5 picoseconds. By passing the laser beam through an index-matched ADP crystal it was possible to illuminate the Schlieren system with the more easily recorded second harmonic radiation. The photographs obtained, which show the growth of a plasma produced by a synchronized ruby laser, clearly demonstrate the potential of picosecond light pulses in Schlieren studies. Author
APPROVED FOR PUBLIC RELEASE