Ultrastable and Compact Deep UV Laser Source for Raman Spectroscopy

Deep-ultraviolet (DUV) Raman spectroscopy is a powerful method to isolate and extract the unique signatures of numerous chemical bonds present within complex samples. DUV (&#955; < 250 nm) excitation is critical for NASA missions because it shows an over 200-fold greater efficiency compared to commonly used 785 nm excitation and illumination as such short wavelengths minimizes the fluorescence background in the Raman spectra. The unavailability of compact, robust, and reliable deep-UV laser sources has constrained implementing DUV Raman spectroscopy in NASA's space-borne exploration and research. TIPD proposes to develop an ultrastable, compact, and robust DUV laser source for Raman spectroscopy based on our demonstrated capability in developing single-frequency fiber lasers and solid-state DUV laser sources. Cooperating with the University of Arizona, TIPD developed an ultrastable and compact single-frequency linearly polarized fiber laser system operating at 976 nm during the Phase I program. The team also developed a single-frequency fiber amplifier at 976 nm and single-pass frequency doubling of 976 nm light to demonstrate the viability of the compact design. Separately, the team has designed and delivered a 150 mW DUV laser for Raman spectroscopy operating at 244 nm using a BBO crystal and a resonant bow-tie cavity based upon a 976 nm VECSEL source. In phase II, the team will scale the power of the 976 nm fiber amplifier to achieve a 5-watt single-frequency output. The 5-watt single-frequency 976nm master oscillator power amplifier (MOPA) will act as the pump to build a 100-mW deep-UV laser prototype that will be delivered to NASA.