Coherent light generators – Optical fiber laser
Patent
1990-10-11
1992-01-28
Davie, James W.
Coherent light generators
Optical fiber laser
372 40, H01S 306, H01S 317
Patent
active
050848810
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the general subject of glass lasers, and, in particular to an apparatus for producing visible lasing emission from a rare earth doped optical fibre.
BACKGROUND OF THE INVENTION
Glass lasers were invented in 1961 (Snitzer E., "Optical Maser Action of Nd.sup.3+ in a Barium Crown Glass," Phys Rev., 1961, 7, p 444) and are now widely used. Glass lasers are advantageous because they have high gain, long fluorescence life times and can be simply made in a variety of geometries.
There is a reported observation of visible laser action from a samarium doped crystal (Kazakov B. N., Orlov M. S., Petrov M. V., Stolov A. L., Tkachuk A. M.; "Induced Emission of Sm.sup.3+ Ions in the Visible Region," Opt. Spectrosc (USSR) 1979, 47, p 676-677). However, laser emission due to the .sup.4 G.sub.5/2 to .sup.6 H.sub.9/2 transition in Sm.sup.3+ ions has not previously been observed in any material, particularly glass.
SUMMARY OF THE INVENTION
The glass laser of the invention is characterised by a glass gain medium which contains trivalent samarium Sm.sup.3+ ions and which, when optically pumped on one or a number of absorption bands to achieve excitation to the metastable .sup.4 G.sub.5/2 level, radiates light at a wavelength substantially corresponding to transitions from the .sup.4 G.sub.5/2 level of samarium.
The laser of the invention is a glass laser which is capable of producing visible red light, as well as yellow, orange and infrared light. According to a preferred embodiment of the invention, the glass gain medium is an optical fibre waveguide containing Sm.sup.3+ ions in its core, the cladding, or both.
BRIEF DESCRIPTION OF THE DRAWINGS
An embodiment of the invention will now be described in detail, by way of example, with reference to the drawings, in which:
FIG. 1(a) is an energy level diagram;
FIG. 1(b) is an absorption spectrum for samarium-doped silica;
FIG. 2 shows the fluorescence spectrum of silica glass doped with Sm.sup.3+ ions;
FIG. 3 is a schematic diagram of a Fabry-Perot resonator forming the basis for an operative glass laser;
FIG. 4 shows the lasing characteristics of a glass laser based on the resonator of FIG. 3; and
FIG. 5 shows an oscilloscope trace of a Q-switched pulse from the laser of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The optical properties of silica doped with Sm.sup.3+ ions are illustrated by the energy level diagram of FIG. 1(a) and by the absorption spectrum of FIG. 1(b). Samarium Sm.sup.3+ doped silica has been found to be a particularly attractive lasing medium by virtue of the long meta-stable life-time combined with the high branching ratio and narrow line-width (3.3 nm) of the radiative transition (see FIG. 2). These properties are more usually a characteristic of rare-earth ions in crystals rather than an amorphous glass host.
An operative glass laser based on a Fabry-Perot resonator is shown in FIG. 3. Dielectric mirrors 1 and 2 have reflectances at the laser wavelength of 651 nm of 99% and 60% respectively. Both mirrors have reflectances less than 10% at the pump wavelenght 488 nm. A samarium-doped fibre 3 is cleaved and butted up to the mirrors. The mirrors 1 and 2 provide optical feedback at the lasing wavelength and the fibre provides the gain medium.
Preferably, a waveguide confines the optical field to a high intensity region which results in a lower threshold for laser action. Recent work (Mears R. J., Reekie L., Poole S. B., Payne D. N.; "Neodymium-doped silica single mode fibre lasers," Electron. Lett., 1986, 21, pp 738-740) has produced a single mode glass fibre laser with a threshold below 1 mW. Preferably, therefore, the glass laser of the invention is made from single mode silica fibre doped with samarium.
In particular, a silica optical fibre preform, containing more than 80 mole % silica (SiO.sub.2), is doped with 250 molar ppm of Sm.sup.3+ ions using a solution doping process (Stone, Burrus; "Nd-doped SiO.sub.2 Lasers in End Pumped Fibre Geometry," Appl Phys Lett., 23, pp 388-389). The preform
REFERENCES:
patent: 3729690 (1973-04-01), Snitzer
patent: 4825444 (1989-04-01), Johna et al.
Kazakov et al., "Induced Emission of Sm.sup.3+ ions in the Visible Region of the Spectrum", Opt. Spectrosc. (USSR), 47(6), Dec. 1979, pp. 676-677.
T. T. Basieu et al., "Selective Laser Excitation of the Luminescence of Sm.sup.3+ ions in Lanthanum Aluminum Silicate Glass", Opt. Spectrosc. (USSR) 46(5) May 1979, pp. 510-512.
Farries Mark C.
Morkel Paul R.
Townsend Janet E.
Amoco Corporation
Davie James W.
Gabala James A.
Magidson William H.
Medhurst Ralph C.
LandOfFree
Glass laser does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Glass laser, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Glass laser will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1865674