Claims
- 1. A passively Q-switched laser system having an optical cavity for resonating laser radiation, including an optical gain medium comprising:
- RF means for applying RF power to said gain medium;
- Q-switch absorbing means disposed within said optical cavity; and
- means for coupling radiation out of said cavity, characterized in that:
- said laser system includes a detector responsive to laser radiation resonated within said cavity for generating a signal;
- controller means responsive to said signal for controllig said RF means for applying RF power to turn off said RF means for a predetermined off period commencing after a predetermined delay from said signal.
- 2. A laser according to claim 1, further characterized in that said controller includes means for turning off said RF means for one of a plurality of predetermined off periods, in accordance with a selection signal applied to said controller, whereby said output radiation will emerge from said laser with a variable pulse format dependent on said selection signal.
- 3. A laser according to claim 2, further characterized in that said predetermined delay permits at least two radiation pulses to emerge from said laser.
DISCLOSURE OF THE INVENTION
The Government has rights in this invention pursuant to Contract No. DAAK80-79-C-0302 awarded by the Department of the Army.
1. Technical Field
The field of the invention is that of a Q-switched laser having a variable repetition rate.
2. Background Art
It is known to construct a passively Q-switched laser using SF.sub.6 or another saturable absorber, and that such a laser produces a train of optical pulses having a repetition rate that depends on the gain of the laser medium and hence on the optical cavity length. The dependence of repetition rate on cavity length in prior art passively Q-switched lasers has made the repetition rate both unstable and difficult to change, especially at low repetition rates. Actively Q-switched lasers using electro-optical modulators are known and are able to change the repetition rate quickly to accommodate differing system requirements, but the use of the electro-optical modulator requires additional expense, additional system complexity and additional power consumption.
U.S. Pat. No. 3,641,459 discloses stabilization of the repetition rate of a diode laser by feeding back a signal on a CW basis that is harmonically related to the repetition rate. This patent does not disclose variation of the repetition rate that is stabilized by this method.
The invention relates to a passively Q-switched laser in which the repetition rate is made variable by detecting the output of the laser beam and controlling an RF amplifier supplying power to the gain medium in accordance with the desired repetition rate.
One feature of the invention is the ability to provide pulses at a low repetition rate in a stable manner. Another feature of the invention is the ability to modify quickly the pulse format of the system.
US Referenced Citations (6)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| WO8100330 |
Feb 1981 |
WOX |
Non-Patent Literature Citations (1)
| Entry |
| Berdahl, "Short-Range Self-Pulsed Optical Radar", NASA Tech. Briefs, vol. 5, No. 4, Winter 1980, p. 433. |
Patent Grant
4539685
