RESUMO
A sensitive chemical aerosol Raman detector (CARD) has been developed for the trace detection and identification of chemical particles in the ambient atmosphere. CARD includes an improved aerosol concentrator with a concentration factor of about 40 and a CCD camera for improved detection sensitivity. Aerosolized isovanillin, which is relatively safe, has been used to characterize the performance of the CARD. The limit of detection (SNR = 10) for isovanillin in 15 s has been determined to be 1.6 pg/cm3, which corresponds to 6.3 × 109 molecules/cm3 or 0.26 ppb. While less sensitive, CARD can also detect gases. This paper provides a more detailed description of the CARD hardware and detection algorithm than has previously been published.
RESUMO
Measurement of the key thermo-optic properties of AgGaSe2 in the temperature range below 300 K is reported. Values of these properties on cooling become favorable for the higher average-power operation of nonlinear optical frequency converters using this material.
RESUMO
Thermo-optic distortions often limit the beam quality and power scaling of high-average-power lasers. Cryogenically cooled Yb:YAG is used to efficiently generate 165 W of near-diffraction-limited beam from a power oscillator with negligible thermo-optic effects. End pumped with 215 W of incident pump power from two diode modules, the laser has an optical-optical efficiency of 76%, a slope efficiency of 85%, and an M2 value of 1.02.
RESUMO
Wavelength beam combining of five ytterbium fiber lasers is demonstrated in a master-oscillator power-amplifier configuration at combined powers up to 6 W. The combined beam profile has an M2 value of 1.14, which is equal to that of an individual fiber. Beam steering in one dimension over 140 resolvable spots is also demonstrated.
RESUMO
We have developed an efficient room-temperature ytterbium-doped YAG laser operating at 1.03 microm pumped by an InGaAs strained-layer diode laser operating at 968 nm. The threshold was 234 mW and 23 mW of output power was obtained for an absorbed pump power of 345 mW. This laser offers a number of advantages over AlGaAs pumped Nd:YAG lasers, such as broader absorption features, longer fluorescent lifetime, and lower thermal loading of the gain medium.
RESUMO
Changes in the refractive index of Ti:Al(2)O(3) induced by 10-nsec, 532-nm pump pulses from a frequency-doubled Nd:YAG laser have been measured interferometrically at 632.8 nm for signal polarizations parallel (pi) and perpendicular (sigma) to the c axis. The nonthermal portion of these changes decays on a 3-microsec time scale characteristic of the fluorescence lifetime of Ti(3+). For the sigma polarization, the nonthermal index change is equal to the concentration of excited Ti(3) ions times (4 +/- 2) x 10(-24) cm(3). The change for the pi polarization is lower by a factor of 3.7 +/- 0.6. The average change is consistent with the value estimated from a harmonic oscillator model that considers virtual transitions to a charge-transfer band.
RESUMO
The influence of amplified spontaneous emission on the time-dependent gain of a laser amplifier is considered by using a simple model. Experimental measurements of Ti:A1(2)O(3) amplifier gain are in excellent agreement with the model.
RESUMO
Room-temperature cw operation of a Ti:Al(2)O(3) laser has been demonstrated for the first reported time. Laser emission at 770 nm was excited with an all-line Ar-ion laser pump. The maximum output power was 1.6 W. Values of (64 +/- 10)% for the internal quantum efficiency and (2.4 +/- 0.5)% for the round-trip cavity loss are obtained from the thresholds and slope efficiencies measured with 0.7 and 4.9% output couplers. The cavity-loss value places an upper bound of 0.007 cm(-1) on the absorption coefficient of the laser rod for the pi polarization (E ||c) || at 770 nm, compared with 0.73 cm(-1) measured at 490 nm, the peak of the Ti(3+) pump band.
