Method and apparatus for producing isolated laser pulses having a fast rise time

Claim 1

Apparatus for producing fast rise time, high energy laser pulses comprising: a. means having mirrors for producing Q-switched pulses of laser energy from a linear laser oscillator capable of being operated as a mode locked device to produce round trip pulses between the mirrors in the oscillator and resulting output pulses, and which comprises: b. an optical cavity defining an optical axis between a first partially transmitting and partially reflecting mirror and a second fully reflecting mirror, c. a gain medium disposed along the axis between the mirrors, d. first polarizing means disposed in the optical cavity on the axis between the gain medium and the first mirror, for transmitting laser energy back and forth between said mirrors, e. second polarizing means disposed in the optical cavity on the axis between the gain medium and the second mirror for transmitting laser energy back and forth between said mirrors, and f. electro-optic modulation means disposed on the axis between the gain medium and the second polarizing means having: g. excitation terminals selectively carrying an excitation voltage that rotates the polarization direction of linearly polarized light passing therethrough 90*, said terminals removing the 90* rotation when short circuited; h. a gas filled spark gap between said excitation voltage terminals for short circuiting said excitation terminals for removing the 90* rotation for producing an output of laser energy in the cavity by reflection from said second polarizing means; and i. means for optically directing a sample of the Q-switched laser pulse energy in the oscillator through the first polarizing means and the first mirror in a direct path to the modulator means where the laser energy is concentrated in the form of a synchronized burst of energy in the spark gap to produce a plasma which short circuits the voltage on the terminals of the electro-optical modulation means and rapidly removes the excitation voltage of the modulator for producing a laser output pulse having a duration less than the round trip for pulses in the cavity and an energy content at least one to two orders of magnitude greater than the energy content of a single pulse from the oscillator when it is operated as a mode locked device.