Abstract

Because large third-order refractive nonlinearities, γ, are expected, much study on nanocrystal doped glasses has focused on the nonlinear optical properties at or near the single photon resonance.¹ Although γ is smaller in the single-photon transparent region, its temporal response is expected to be pulse-width limited. More importantly, since the potential use of these materials as optical devices depends on the figure-of-merit ratio proportional to γ/(ατ or (βτ), where α and β are the linear and nonlinear absorption coefficients, respectively, and τ is the response time, a possibly larger figure of merit in the transparent region warrants studies far from the absorption edge. Recent studies²,³,⁴ performed on photodarkening CuBr nanocrystal doped glasses in the transparent region indicate a sizable two-photon enhanced nonlinearity which should scale with the concentration of CuBr nanocrystals in the glass. Time-resolving the nonlinear optical response³ with 60 fs, 620 nm optical pulses revealed a nearly pulse-width limited response followed by a subpicosecond decay. The CuBr and CuCI nanocrystals with the band edge in the 370-400 nm region are single-photon-transparent to the 620 nm light, but are two-photon-resonant at this wavelength or at 800 nm, the wavelength of interest in this study.

© 1996 Optical Society of America