Ion-exchanged tapered-waveguide laser in neodymium-doped BK7 glass

We report what is to our knowledge the first operation of a planar dielectr ic tapered-waveguide laser. The waveguide laser is fabricated by potassium- ion exchange in Nd3+-doped BK7 glass and consists of a single-mode channel waveguide of a few micrometers' width followed by a linear taper up to a br oad region with a width of similar to 180 mu m. A slope efficiency of 42% i s found both in the tapers and in standard channel waveguides fabricated up on the same substrate, indicating that the tapers and the channels have sim ilar internal losses; hence the low-loss nature of the tapered beam expansi on. The output from either end of the tapered structure is found to be near ly diffraction limited. (C) 2000 Optical Society of America.