CARRIER-DEPENDENT NONLINEARITIES AND MODULATION IN AN INGAAS SQW WAVE-GUIDE

We report measurements of optically induced carrier-dependent refractive index changes and their saturation in an InGaAs single quantum well centered within a linear multiple quantum well guided-wave Fabry-Perot resonator using diode laser sources. A low-excitation nonlinear refractive cross-section sigma(n) = -1 X 10(-19) cm3 was deduced for probe wave-lengths near the TM absorption edge, falling only to sigma(n) = -3.1 X 10(-20) cm3, over 0.16 mum from the bandedge. For an incident irradiance of 18 kW/cm2 , refractive index changes in the InGaAs quantum well as large as -0.16 were deduced near the absorption edge, while the index change at a wavelength 0.16 mum from the absorption edge was -0.055. This large off-resonant index change is attributed to an enhanced free-carrier contribution within a 2-D system.