Narrow output line from a distributed-feedback dye laser with broad-spectrum pumping

The direct dependence of the characteristics of the distributed-feedback laser on the pump spectrum greatly impedes the production of narrow spectral lines in the output from dye lasers and degrades the energy and spectral stability of these lasers. Even though methods have been described for producing a narrow output line from a distributed-feedback laser pumped by a broad spectrum, these approaches call for elaborate equipment and expensive optical elements. A new type of distributed-feedback laser is described which can generate a narrow output line when pumped by a broad spectrum. The design is both simple and inexpensive. It consists in a cell holding a dye solution and having a transmitting phase holographic grating on its entrance face. The pump beam is incident on this grating in a direction that is perpendicular to its surface; as it leaves the grating it is split into three parts, which correspond to the diffraction orders +1, 0, and -1 (there being no higher orders for the particular grating period used.