RESUMEN
A photonic crystal fiber-based chirped pulse amplification delivering 272 fs pulses of 66.4 µJ energy at a repetition rate of 500 kHz is presented, resulting in an average/peak power of 33.2 W/244 MW. A single grating is adopted for the pulse width stretching and compression, which leads to high-compactness and low cost of the system. The output beam is near-diffraction-limited (M2 = 1.1 ± 0.05) with a power stability better than 0.5%. The cutting of alumina ceramic substrate and flexible printed circuit are demonstrated by using the laser system. The results indicate that the laser is competent for industrial applications.
RESUMEN
The Rb(5Dj )+H2-->RbH[X 1sigma+(v"==0)]+H photochemical reaction was studied in a cell experiment applying a laser pump-absorption technique. Using two-photon excitation of the Rb5 (2)D atomic level in a Rb-H2 vapor mixture, the resulting fluorescence includes a direct component arising from the optically excited state and a sensitized component due to the collisionally populated fine-structure state. The RbH molecules are formed in three-body reactive collisions between excited Rb5 (2)D atoms and ground state H2 molecules. Near-infrared absorption band RbH X (1)sigma+ (v"==0-->v'==17) near 852 nm by using a diode laser was measured. The absorbed intensity of laser beam through a length L of the RbH vapor is defined as deltaI' and deltaI" where deltaI' and deltaI" are the absorbed intensity of pumping 5D(3/2) and 5D(5/2) levels, respectively. The ratio of deltaI' to deltaI" contains information on reactivity. w5D(3/2) and W5D(3/2) are the production rates of Rb in the 5D(5/2) and 5D(3/2) levels by direct laser excitation from the 5S(1/2) level. Using a second experiment in which pump laser is used to pump the 5D(3/2) and 5D(5/2) states in a pure Rb vapor (T = 290 K), and the i'/i" where i' and i" are measured intensities of the 5D(3/2)-->5P(1/2) and 5D(5/2)-->5P(3/2) transition, respectively, is determined. At low density of Rb atoms, the 5D mixing rate is neglect. The rate of 5D(3/2) and 5D(5/2) fluorescence yields the ratio of 5D(3/2) to 5D(5/2) pump production rate. The rate equations were solved, and the authors estimate the value of the cross section at T=385 K and P(H2) =400 Pa for collisional energy transfer from Rb5D(3/2) to 5D(5/2), from Rb(5D)to Rb states other than Rb(5D)to be 9.8 x 10(-16) cm2 and 2.0 x 10(-16) cm2, respectively. The reaction cross sections [i.e., Rb(5Dj)+H2-->RbH+H] for j being 3/2 and 5/2 are 5.4 x 10(-7) and 2.3 x 10(-17) cm2, respectively. The relative reactivity with H2 for two studied atoms is in an order of Rb(5D(3/2)>Rb(5D(5/2)), and this is consistent with the result obtained from a laser pump-probe technique.