Deep Ultraviolet Laser Diode for UV-Resonance Enhanced Raman Identification of Biological Agents

"This proposal addresses the need for deep UV semiconductor lasers for use in UV resonance enhanced Raman spectroscopic identification of biological agents. The proposed approach avoids the problems of p-doping and ohmic contacts by using subminiaturedirect electron injection excitation of an InAlGaN heterostructure. We have demonstrated 238nm emission using this concept from AlGaN bulk material with 64% aluminum. High levels of chemical specificity can be obtained using Raman spectroscopy without sample preparation, contact, or destruction. When Raman excitation occurs within the electronic resonance band of a material the scatter cross-sections canmuch as eight orders of magnitude. For organic molecules such as nucleic and amino acids and other biochemicals these absorption bands are very strong in the deep UV between about 220nm and 280nm. In addition, when Raman excitation below about 250nm isemployed, there is a fluorescence-free region extending > 4000 wavenumbers above the excitation wavelength providing very high detection sensitivities and low background noise. It is the goal of this proposed program to demonstrate deep UV LED and laser emission from a semiconductor device and the ability to obtain deep UV resonance Raman spectra of analogs of hazardous biological agents. The electron beam semiconductor ultraviolet optical source (ESUVOS) being developed here will enable a revolutionary reduction in size, wei