This invention generally relates to solid state laser devices. More particularly, this invention relates to such a laser device which has an output at two distinct wavelengths. Specifically, this two frequency output is achieved by using an array of two different solid state plate like elements, one of which lases at one wavelength and the other at a second wavelength.
It is known that most solid state lasing materials are pumped by only a small spectral fraction of the white light used to pump these materials. The overall efficiency of such lasers is therefore rather low since most of the pump light is wasted. One attempted solution to this problem has been to try co-doping such materials with sensitizers which absorb light not absorbed by the lasing species and transfer some of this absorbed energy to the lasing species. Unfortunately, the sensitizers used to date often tend to quench the lasing species.
One way to increase the efficiency of a laser is to use materials which absorb in different spectral regions of the white pump light. This then gives a laser with two wavelengths as an output beam. Two wavelength lasers are valuable in several instances: two wavelength holography; two-step isotope separation or photochemical processing; increasing the tunable range of the laser; minimizing the interference effects of monochromatic laser radiation; and pollution monitoring with laser beams. U.S. patent application Ser. No. 727,826, filed Sept. 29, 1976, and having an assignee and one inventor in common with this application, discloses a hybrid laser structure in which a liquid coolant lases at one wavelength and a solid element lases at a second wavelength.
We have found that a similar result may be obtained using two solid state plate like elements. An all solid state laser of this type avoids the complexity of a liquid circulation and containment system, as well as the inaccuracies imparted by the variable expansion experienced by a liquid laser. In our invention, a plurality of solid state plate like elements are arranged in an array. The array has two different plate like elements arranged in an alternating pattern. One series of plate elements absorb light in one spectral region of white pump light while the other plate elements absorb in a second spectral region of white pump light. The two plate elements then lase at two distinct wavelengths. It is critical that the material for the plate elements be selected so that neither absorbs light in the wavelength at which the other lases.