Solid state laser with positive thermal lens

Details Solid state laser with positive thermal lens Solid state laser with positive thermal lens

1996-11-06

1998-05-05

Healy, Brian

Coherent light generators

Particular pumping means

Pumping with optical or radiant energy

372 10, 372 39, 372 40, 372 43, 372 71, H01S 3091

Patent

active

057486646

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to a solid state laser particularly to the type pumped by a semiconductor diode laser. More particularly, but not exclusively, the invention relates to an end pumped solid state laser.
2. Discussion of Prior Art
The combination of a solid state gain medium pumped by a semiconductor diode laser shall hereinafter be referred to as an all-solid-state laser.
It is well established (e.g. D. C. Shannon and R. W. Wallace, Optics Letters, Volume 16, Number 5, pages 318 to 320, Mar. 1st 1994 S. C. Tidwell, J. F. Seamans and M. S. Bowers, Optics letters, Volume 18, Number 2 Pages 116 to 118, Jan. 15 1993) that there are a number of advantages in using end pumping schemes as compared to side pumping schemes when using diode lasers to pump solid state gain media. In particular these advantages result from the ability to deposit the pump energy into a smaller volume of the gain medium when using end pumping as opposed to side pumping schemes. These advantages are twofold, namely: firstly, for a given diode laser power (energy input) higher single pass gains are attained which has the benefit of making the optical resonator of the laser less susceptible to loss thereby leading to an improved external efficiency for the end pumped all-solid-state laser; secondly, a better overlap between the volume of the gain medium that is optically pumped by the diode laser and the cavity mode of the all-solid-state laser is attained thereby improving the slope efficiency as compared with the side pumped all-solid-state laser.
Despite these advantages a number of difficulties are encountered in applying end pumping schemes to an all-solid-state laser, particularly these relate to thermal effects induced in the gain medium by the absorption of the diode laser pump energy and include thermally induced birefringence, thermally induced lensing and thermal fracture of the solid state gain medium. Such difficulties are more severe in the case of end pumping than in the case of side pumping because of the smaller volume in which the pump energy is absorbed in the former compared with the latter case.


SUMMARY OF THE INVENTION

According to the present invention there is provided an all-solid-state laser comprising a slab of gain medium (1), a diode laser pump system (3) configured in an end pumping geometry with the gain medium and a heat sink thermally contacted to the gain medium characterised in that the gain medium exhibits a negative bulk thermal lensing effect and that the diode laser pump system and the gain medium are cooperably arranged so that in use a positive thermal lens is capable of being formed at the surface of the gain medium and is such that the negative bulk thermal lensing effect within the gain medium is overwhelmed, and further characterised in that the gain medium has a thickness which is as small as possible while permitting the unhindered passage of a laser mode through the slab.
Nd:YLF is an example of a gain medium having a negative bulk thermal lensing effect but other such media which may be used in conjunction with this invention will be readily apparent to the skilled person. The use of a thin slab geometry of a gain medium of this type, has the advantage that the residual thermal energy remaining in the gain medium after extraction of the coherent optical output is better dissipated, so reducing the thermal loading in the medium. This permits the use of higher pump energies per unit volume of gain medium before reaching the limits of thermal fracture.
Additionally, the diode laser pump system and the gain medium are cooperably arranged so that in use a positive thermal lens is capable of being formed within the medium. In this configuration a surface dominated positive thermal lensing effect (converging lens behaviour) in the gain medium overwhelms any volume dominated negative thermal lensing effect (diverging lens behaviour) in the gain medium with the advantage that the resulting overall positive lensing effect present in the op

REFERENCES:
patent: 3577098 (1971-05-01), Winston
patent: 4199735 (1980-04-01), Chadwick et al.
patent: 4713820 (1987-12-01), Morris et al.
patent: 4730324 (1988-03-01), Azad
patent: 4782495 (1988-11-01), Azad
patent: 4912713 (1990-03-01), Langhans
patent: 5181214 (1993-01-01), Berger et al.
patent: 5235610 (1993-08-01), Finch et al.
patent: 5325390 (1994-06-01), Tidwell
patent: 5561547 (1996-10-01), Keirstead et al.
Optics Letters, vol. 16, No. 5, 1 Mar. 1991, New York, US, pp. 318-320, D.C. Shannon et al., "High Power Nd: YAG Laser End Pumped by a CW, 10 mm x 1 .mu.m Aperture, 10-W Laser-Diode Bar".
Optics Letters, vol. 18, No. 2, 15 Jan. 1993, New York, US, pp. 116-118, S.C. Tidwell et al., "Highly Efficient 60-W TEMoo CW Diode-End-Pumped Nd:YAG Laser".
IEEE Journal of Quantum Electronics, vol. 26, No. 5, May 1990, New York, US, pp. 827-829, C. Pfistner et al., "Efficient Nd:YAG Slab Longitudinally Pumped by Diode Lasers".
IEEE Journal of Quantum Electronics, vol. 29, No. 6, Jun. 1993, New York, US, pp. 1515-1519, R. Scheps et al., "Efficient, Scalable, Internally Folded Nd:YAG Laser End-Pumped by Laser Diodes".
Laser Focus World, vol. 30, No. 6, Jun. 1994, Tulsa, US, pp. 20-22, Y.A. Carts, "Diode-Pumpted Slab Lasers Operate at High Frequencies".

Affiliated with

Also associated with

Rating

Solid state laser with positive thermal lens does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Solid state laser with positive thermal lens, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Solid state laser with positive thermal lens will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-63518