Single-mode, All-Solid-State Nd:YAG Laser Pumped UV Converter
In this paper, the status of a high-energy, all solid-state Nd:YAG laser pumped nonlinear optics based UV converter development is discussed. The high-energy UV transmitter technology is being developed for ozone sensing applications from space based platforms using differential lidar technique. The goal is to generate greater than 200 mJ/pulse with 10-50 Hz PRF at wavelengths of 308 nm and 320 nm. A diode-pumped, all-solid-state and single longitudinal mode Nd:YAG laser designed to provide conductively cooled operation at 1064 nm has been built and tested. Currently, this pump laser provides an output pulse energy of >1 J/pulse at 50 Hz PRF and a pulsewidth of 22 ns with an electrical-to-optical system efficiency of greater than 7% and a M(sup 2) value of <2. The single frequency UV converter arrangement basically consists of an IR Optical Parametric Oscillator (OPO) and a Sum Frequency Generator (SFG) setups that are pumped by 532 nm wavelength obtained via Second Harmonic Generation (SHG). In this paper, the operation of an inter cavity SFG with CW laser seeding scheme generating 320 nm wavelength is presented. Efforts are underway to improve conversion efficiency of this mJ class UV converter by modifying the spatial beam profile of the pump laser.
Single-frequency 355 nm source for direct-detection wind lidar
We have developed a laser based on an oscillator/amplifier design that uses diode-pumped, conductively cooled Nd:YAG slabs as the gain media. The oscillator is a telescopic ring resonator design that can be easily configured for a range of operational scenarios. An unstable version of the oscillator achieved 125 mJ/pulse with >10% electrical to optical efficiency and an M2 of 2.5. Operated in a stable TEM00 mode, the ring laser demonstrated >30 mJ/pulse at 100 Hz with an M2 of 1.3. We used the 30 mJ TEM00 output to extract the amplifiers and achieved 300 mJ/pulse of single frequency output at 50 Hz with an M2 of 1.5. We also investigated operation of an injection-seeded version of the ring resonator operated in the marginally stable regime without the use of graded reflectivity mirrors. With this approach we demonstrated single-frequency, 50 mJ/pulse operation at 50Hz with an M2 of 1.4 and a square, supergaussian profile. Initial third harmonic generation measurements have achieved over 40% conversion to 355 nm.
Evaluation of antioxidants by a rapid polarographic method
A simple, rapid, precise, and reproducible method and an adaptable apparatus for polarographic measurement of lipid peroxidation and antioxidant activity is described. This method measures antioxidant activity within a few min time as compared to the hours or days needed for several widely used methods. Peroxidation rates were measured for different lipids as a function of amount of lipid, and amount of biocatalyst. The method is applicable to the detection and measurement of the antioxidant effects exhibited by weak antioxidants and has been satisfactorily used for the measurement of the antioxidant activity of different concentrations of powerful antioxidants.