Nonlinear multiple quantum well hetero n-i-p-i structure for photonics.

A structure that combines the advantages of both n-i-p-i structures and multiple quantum wells is the hetero n-i-p-i, a periodic arrangement of n-type and p-type layers with undoped layers of smaller bandgap material inserted. In a conventional hetero n-i-p-i, single quantum wells are separated by doped wideband gap regions of comparable width. A multiple-quantum-well heterostructure (MQW H n-i-p-i) is presented in which several quantum wells are separated by doped regions much wider than each quantum well. The wide bandgap material is Al_0.32Ga_0.68As. The quantum wells are undoped GaAs; p- and n-type regions have nominal dopant concentrations of 2 × 10¹⁸ cm^-3. For light incident on the MQW H n-i-p-i with wavelengths longer than 700 nm, absorption takes place primarily in the quantum wells. Nonlinear transmission of the MQW H n-i-p-i between 700 and 880 nm has been measured, and the spectral dependence of the changing absorption is attributed to pump-induced changes in the index of refraction of the quantum wells.