High Quantum Efficency Extended Wavelength Vacuum Photocathodes

50197-98-I High Quantum Efficency Extended Wavelength Vacuum Photocathodes--Nano Systems Inc., 83 Prokop Road, Oxford, CT 06478-1108; (203) 811-2827 Dr. Charles P. Beetz, Principal Investigator Mr. Robert Boerstler, Business Official DOE Grant No. DE-FG02-98ER82625 Amount: $75,000 Existing vacuum photocathodes have limited quantum efficiencies in the visible spectrum and limited wavelength response in the near infrared. The intrinsic photoemission mechanism extends to nearly 3¿m radiation, but the low optical absorption of the photocathode material, when balanced against the short photoelectron escape depth, prevents high effective quantum efficiency. The effective quantum efficiency can be improved by forming vacuum photocathodes on a substrate which is shaped in such a way that the effective optical thickness to incident photons is large, but the effective escape depth for electrons remains small. This will be accomplished by forming a silicon/silica micromachined channel surface with very high aspect ratio channels on which the photocathode is formed; then the photoelectrons will be emitted into the channels, but the photons will continue to cross more thicknesses of photocathode. Commercial Applications and Other Benefits as described by the awardee: Vacuum photocathodes with quantum efficiencies approaching 50 % between 350 nm - 2.5¿m should result. This should greatly improve low light level detectors and imagers, resulting in more sensitive spectrometers, night vision devices, medical diagnostic imagers and equipment, including DNA analysis, and fiber optic communications._