Abstract

With their strong quantum confinement, semiconductor quantum dots offer the potential for application as efficient nonlinear optical elements. Recently, their use for saturable absorber mode locking has been successfully demonstrated.¹ Previous work on the nonlinear response of quantum dots has been mainly concentrated on Cd-compound nanocrystallites, which exhibit strong nonlinearities in the visible spectrum. Recently quantum dots of PbTe in glass matrices have been fabricated.² The lower bandgap of lead compounds provides an opportunity to produce quantum dots absorbing in the wavelength range from 1 to 2 pm, so they can be tailored to the gain spectra of virtually all solid-state lasers in that range. Of particular interest are dots optimized for the 1.55-μηι communication band. Also, with their large bulk exciton Bohr radius, PbTe quantum dots allow strong quantum confinement with relatively large nanocrystals. A typical absorption trace is shown in Fig. 1. In this example, the quantum-confined state corresponds to a wavelength of 1230 nm, which relates to an average nanocrystallite diameter of 4.3 nm.

© 1998 Optical Society of America