Abstract

In a series of previous experiments,^1-3 we have established the tapered single-mode optical fiber, surrounded by a circulating dye solution, as a practical and versatile nonlinear device. At the first integrated photonics meeting in 1990,¹ we presented results that demonstrated both efficient optical amplification and saturable absorption at optical power levels of only tens to hundreds of milliwatts. Conventional dye laser amplifiers and saturable absorbers more commonly require power levels of tens to hundreds of watts. Our ability to fabricate tapers with submicrometer waist diamters results in high optical power intensities at the taper waist for modest pump powers. For example, a taper waist of 0.5 μm (typical of our packaged devices) produces a power intensity of approximately 1 MW/cm² at the waist for an input power of only 10 mW. From these results, we have established that low pump power, all-fiber, dye laser and superfluorescent sources are feasible. As a preliminary, we have conducted a series of experiments on the superfluorescent or amplified spontaneous emission from a tapered fiber surrounded by a circulating solution of DOTCI. The choice of this particular dye was dictated by the convenience of being able to use a visible 650-nm pump source. Peak pump powers of approximately 1 W with a 10-ns pulse width were used to excite a tapered fiber with a waist diameter of approximately 1 μm. Amplified spontaneous emission, centered on the fluroescent peak at about 720 nm, was measured with a spectral width of 40 nm (Fig. 1).

© 1991 Optical Society of America