Direct writing of gratings in GaInAs/GaInAsP quantum wells using pulsed laser irradiation

A new quantum well intermixing technique, which involves irradiating multiple quantum well material with high energy laser pulses and producing transient heating, has been developed. A Q-switched Nd:YAG laser with pulse length of /spl sim/7 ns, repetition rate of 10 Hz and pulse energy density /spl sim/5 mJ mm/sup -2/ is used to generate a localised increase in the density of point defects. After subsequent annealing in a rapid thermal processor bandgap shifts of over 100 nm were observed. The spatial resolution was investigated by masking the sample with a metal mask. Spatially resolved photoluminescence measurements showed that the resolution of the process was 25 /spl mu/m or better, this measurement being limited by the resolution of the photoluminescence set up. Gratings, with a pitch of 2.5 /spl mu/m, were wet-etched into the back of waveguide samples, and the samples were irradiated through the grating and annealed as before. Waveguide transmission spectra showed a dip in the transmitted intensity around a wavelength of 1.525 /spl mu/m indicating that a grating had been formed.