High-power high-repetition-rate UV light at 355 nm generated by a diode-end-pumped passively Q-switched Nd:YAG laser.

We describe experimental results with a diode-pumped, passively Q-switched extracavity second- and third-harmonic generation. Cr:YAG is used as a saturable absorber for pulse generation. Taking into account the thermal effects of Nd:YAG at high incident pump power, we use a short plane-to-plane cavity configuration to take advantage of the maximum pump power and obtain the compactness structure. At the same time, we use the type-I critical phase-matched lithium triborate crystal to generate light at 532 nm and mix the residual fundamental at 1064 nm and the second-harmonic wave at 532 nm in the type-II critical phase-matched lithium triborate crystal for UV light generation at 355 nm. A third-harmonic-generation output power of 1.32 W is achieved at the incident pump power of 27.5 W, corresponding to an optical-to-optical efficiency of 4.8%. The instability of the UV laser power is less than 5% for 4 h.

[Carotenoid levels measured by resonance Raman in vivo].

Carotenoid molecules are powerful antioxidants which can act as scavengers for free radicals, singlet oxygen, and other harmful reactive oxygen species in human body. Studies have shown an inverse correlation between the level of carotenoid and the risk of cancers, cardiovascular diseases, and degenerative diseases. High-performance liquid chromatography is used for measuring carotenoid levels as a standard method, but it is not noninvasive and real-time detecting. The authors have developed a novel noninvasive optical technology to measure carotenoid level in vivo by detecting the resonance Raman spectra, which can be used for high sensitivity and real-time detecting. When a low noise 473 nm laser with power less than the exposure limit set by ANSI Z136. 1-2000 standards, a clearly distinguishable low resonance Raman spectra superimposed on a strong fluorescence background is produced. The carotenoid level is assessed by measuring the resonance Raman intensity. Using penetrating tissue technology, the authors improved the signal-to-noise ratio in the setup. The experimental results from different volunteers confirmed that the carotenoid level is proportional to the intake of it. The technology provided important values for clinic applications and science research.

High-repetition rate Q-switched Nd:YVO4 laser with a composite semiconductor absorber.

A diode-pumped Nd:YVO4 laser passively Q switched by a semiconductor absorber is demonstrated. The Q-switched operation of the laser has an average output power of 135 mW with a 1.6 W incident pump power. The minimum pulse width is measured to be about 8.3 ns with a repetition rate of 2 MHz. To our knowledge, this is the first demonstration of a solid-state laser passively Q-switched by such a composite semiconductor absorber.