Several experimental demonstrations of laser giant pulsing using a saturable absorber inside the laser cavity as a fast switch have recently been reported. In the present work giant pulse parameters such as pulse rise and fall times and peak power are calculated as a function of σ, the ratio of absorber to laser ion cross sections; nai, the normalized inversion prior to switching; and the laser mirror transmission Tr. It is shown that there is an optimum Tr for the extraction of maximum peak power. A criterion for the minimum σ for giant pulsing to occur is derived. The largest output occurs when σ → ∞ in which case the theory approaches that of Wagner and Lengyel. Some numerical examples are presented as well as a discussion of the range of validity of the theory.

Theory of Laser Giant Pulsing by a Saturable Absorber

Giant Pulse Laser Operation by a Passive, Reversibly Bleachable Absorber

A solution of cryptocyanine in methanol has been used as a self‐synchronizing, nondestructive, passive Q‐switch in a ruby laser. A symmetric giant pulse of ∼10 nsec width and 5–10 MW peak power is produced with a standard ruby laser system. This pulse is comparable with pulses generated by other Q‐switching techniques.

Photosensitive Liquid used as a Nondestructive Passive Q‐Switch in a Ruby Laser

: A summary of studies carried on during the year on (1) Anterior chamber measurements on CO2 corneal irradiation; (2) corneal calcification on CO2 laser irradiation; (3) ocular injury from CO2 laser irradiation; (4) application of thermal models to retinal threshold injury; (5) toxic and explosive hazards associated with lasers; (6) pathology of internal viscera following laser irradiation; (7) a method for detecting and measuring frequency of surface vibrations using a helium neon laser; (8) exploration of potential carcinogenic effects of pulsed laser irradiation; (9) lasers in biology and medicine; and (10) rupture and tensile strength measurements of fresh and treated canine aortic tissue. (Author)

Biological effects of laser radiation.

A powerful light pulse propagation through an optical amplifier driven at saturation was studied theoretically and experimentally. It was shown that the maximum light pulse of a Q -switched laser propagates through amplifying medium with velocity much higher than the light velocity without any essential decrease of pulse duration. Conditions of reducing pulse duration by nonlinear amplification were found. It was found necessary to increase the leading edge rise time of the light pulse. "Superlight" velocity of propagation was measured in experiments. Appreciable reduction of pulse duration by nonlinear amplification was achieved experimentally when the leading edge of the input light pulse had been cut down by an additional Kerr cell.

5A10(a) - Short-pulse Q-switched laser with variable pulse length

Q‐spoiling is observed when an easily vaporized absorbing film located within the resonant structure of a ruby laser is destroyed by initial stimulated emission. Two features of this new technique are operational simplicity and no severe power handling limitations. The resulting laser output is characterized by a single giant pulse of micro‐second duration whose rise time (in the 20‐ to 40‐nsec range) is at least as fast as reported for Q‐spoiling by Kerr‐cell shutters.

J. Ward

Papers

Laser Q‐Spoiling Using an Exploding Film