Coherent light generators – Particular component circuitry – Optical pumping
Patent
1998-05-28
2000-11-21
Font, Frank G.
Coherent light generators
Particular component circuitry
Optical pumping
372 9, 372 29, 372 75, H01S 300
Patent
active
061513431
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to the field of reproduction technology, and concerns a method and an apparatus for driving diode-pumped solid-state lasers. Such solid-state lasers have a tendency to what are known as "relaxation oscillations," which are dependent on the resonator geometry and the pumping level. When the resonator is excited, oscillations arise in the laser output, which decay after a more or less long time. Although the amplitudes of these oscillations often lie only in the range of a few percent of the laser output, solid-state lasers cannot be unproblematically used in the area of reproduction technology in exposers (recorders) for exposing images and color separations, because they produce stripe-like or wood-grain-like impermissible image disturbances in the color separations. In order to produce a good reproduction quality, oscillation amplitudes of the solid-state laser in the value range 0.1 to 0.2% are just permissible.
In practice, it is thus attempted to avoid exciting the resonator of the solid-state laser, and a particular emphasisis given to freeing the operating current of the laser diode from spikes of the switched-mode power supplies. Nonetheless, sporadically occurring oscillations cannot be entirely avoided.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to improve a method and apparatus for driving diode-pumped solid-state lasers so that disturbing oscillations are suppressed, even during excitation.
This object is solved according to the invention in that the resonator is damped by introducing a fast light controlling in addition to the already-present slow light controlling, said fast controlling being designed only for the amplitude stability of the solid-state laser.
In the following, the invention is explained in more detail on the basis of FIGS. 1 to 3.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a drive circuit for a diode-pumped solid-state laser according to the prior art,
FIG. 2 shows a drive circuit for a diode-pumped solid-state laser according to the invention, and
FIG. 3 shows a characteristic of a laser diode.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a drive circuit or driver circuit for a diode-pumped solid-state laser, with a negative feedback branch for the lower frequency range according to the prior art. A laser generator 1 produces a laser beam 2 with the light power (P), said beam being deflected by a deflecting mirror 3. In the beam path of the laser beam 2, a beam divider 4 is arranged that divides off a measurement beam 5 from the laser beam 2, which measurement beam is a measure of the actual light power of the laser beam 2. The measurement beam 5 is supplied to a negative feedback branch or, respectively, to a control loop, and there falls on a light-measuring diode 6 that is connected downstream from a fast light measurement amplifier 7. A measurement signal produced in the light measurement amplifier 7 is forwarded to a control amplifier 8 that is connected to the light measurement amplifier 7. The light power actual value (P.sub.IST) determined in the light measurement amplifier 7 is supplied to the one input of the control amplifier 8, while the other input is charged with the light power target value (P.sub.SOLL). The control signal obtained in the control amplifier 8 is supplied to a voltage/current converter 9 connected downstream. The voltage/current converter (9), constructed for example from high-power transistors, serves for the production of, a driver current of e.g. 20 A, for a laser diode 10 that operates as a pump diode, and which excites a laser resonator 11 in the laser generator 1.
In the known solid-state lasers, the relaxation oscillations lie in the typical value range of 50 to 100, and sometimes even up to 200 kHz. These high-frequency relaxation oscillations cannot satisfactorily be eliminated using the specified drive circuit, because the bandwidth of the control loop, conditioned by the relatively low cutoff frequency of the high-power transistors used
REFERENCES:
patent: 4918704 (1990-04-01), Caprara et al.
patent: 5177755 (1993-01-01), Johnson
patent: 5226051 (1993-07-01), Chan
patent: 5303248 (1994-04-01), Gibbs
Patent Abstracts of Japan--JP 4217381--Aug. 7, 1992--vol. 16, No. 567 (E-1296)--Semiconductor Laser Drive Circuit.
Patent Abstracts of Japan--JP58102583--Jun. 18, 1983--vol. 7, No. 204 (E-197)--Circuit for Controlling Extinction Ratio of Detector Typelaser Diode.
Patent Abstracts of Japan--JP62169486--Jul. 25, 1987--vol.12, No. 9 (E-572)--Semiconductor Laser Driving Device.
Intensity Noise In Diode-Pumped Single-Frequency Nd: YAG Lasers and its Control by Electronic Feedback 8342 IEEE Photonics Technology Letters 2(1990) Apr., No. 4, New York, US--Thoms J. Kane.
Font Frank G.
Heidelberger Druckmaschinen AG
Inzirillo Gioacchino
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