To realize all-optical switches such as Mach-Zehnder switch, it is a key to induce the refractive index changes enough for π-phase shift in the probing light through optical nonlinearity by a pumping pulse. Self-assembled quantum dots (QDs) are one of the attracting candidates for achieving large nonlinearity. 1 In this paper we demonstrate a method of estimating the optical phase shift of probing pulse in a waveguide with QD core layers by a resonant pumping pico second pulse. We utilize a large polarization-dependent property of the optical nonlinearity arising from a flat-dome-like shape of the QDs. Measurement set up is shown in Fig.1. For the pumping light, we used a ~1.5ps pulse of 1220nm in wavelength from an optical parametric oscillator (OPO) with the repetition rate of 80MHz. For the probing light we used ~150fs pulse of 1270nm from the second OPO system synchronized with the first one. Each wavelength can be changed independently. The pump was TE-polarized, while the probe was 45 deg. polarized. Polarization angle dependence of the transmission was measured by rotating the polarizer in front of the photo receiver.
© 2003 Optical Society of AmericaPDF Article