PHOTOLUMINESCENCE FROM POROUS SILICON BY INFRARED MULTIPHOTON EXCITATION

Visible photoluminescence from porous silicon induced by infrared multiphoton excitation was observed at room temperature, Luminescence resulted from carrier excitations in the surface region of the sample. With the pump in the mid-infrared, excitation was effective only when the pump frequency was near resonance with the stretch vibrations of the surface species, SiHx. For each visible photon emitted, at least seven or eight infrared photons were absorbed. The excitation is believed to occur via pumping up a vibrational ladder, followed by conversion to electronic excitation. The process is similar to infrared multiphoton excitation of polyatomic molecules.