Q-switched Nd : YAG laser

A Q-switched Nd YAG laser (7 ns pulse duration, Quanta-Ray DRC-1A) operated at 10 Hz was used as a light source. The 1064 nm fundamental was frequency doubled to 532 nm for some experiments. In all experiments reported here a geometry was used which focused the laser beam in front of the entrance window of the sample cell such that the laser beam was diverging as it passed through the sample cell. In this geometry the laser beam was about 3 mm in diameter at the region viewed by the light detection system. 

Figure 19. A set of 6 frequency-doubled, Q-switched Nd YAG lasers are used to pump the DM0, preamplifier and power amplifier.

Fe(6-Mepy)2(py)tren] (004)2 Doped in PSS. Magnetic susceptibilities measured for a microcrystalline sample of the complex produce a magnetic moment value = 0.36 pg at 10 K and 0.61 pg at 150 K, followed by a gradual increase to Peff = 2.80 pe at 311 K [138]. Thus 26% of the complexes are in the HS state at 300 K if a magnetic moment of 5.1 Pe is assumed for the pure HS compound. On the other hand, the complex doped into a polystyrene sulfonate (PSS) film does not provide any evidence for a thermal population of the HS state up to 340 K as demonstrated by variable-temperature UV-VIS and Mossbauer spectra. In fact, all the complexes doped into the PSS film are in the LS state at temperatures below 340 K. However, if irradiated by a single pulse of a Q-switched Nd/YAG laser (532 mp), the complex is excited from the LS ground state to the HS J2 states via an intermediate MLCT state and the metal states. The subsequent back relaxation from the excited T2 state to the... 

For comparison purposes, two other MS systems have been used with in vitro grown parasite cultures. In the first case, a home-built miniaturized linear TOF multi-array analyzer1718 was interfaced to the frequency-tripled output at 355nm of a Q-switched Nd-YAG laser ( Polaris, New Wave Research, Fremont, CA). In this experiment the laser beam was not scanned, and the estimated laser fluence after attenuation was similar to that of the commer-... 

To determine optical damage in bulk benzil crystals a Q-switched Nd YAG laser with 1KW peak power, pulse width of 0.1 ps and pulse repetition rate of 500Hz was used. The laser power was attenuated using a set of neutral density filters and focussed onto a bulk benzil crystal using a x10 microscope objective. No optical damage was observed with optical intensities of upto 100MW/cm - Also, no optical damage was observed in benzil cored fibres with similar optical intensities. 

Second-order nonlinearity and molecular orientation in the alternating LB films were evaluated by the SHG measurement using a Q-switched Nd YAG laser. The detailed evaluation procedure was described in the section 1.3. In this measurement, we used the samples in which one of the LB films deposited on both surfaces of a substrate was removed by wiping it of with a cloth soaked with chloroform. 

Third-order susceptibilities of the PAV cast films were evaluated with the third-harmonic generation (THG) measurement [31,32]. The THG measurement was carried out at fundamental wavelength of 1064 nm and between 1500 nm and 2100 nm using difference-frequency generation combined with a Q-switched Nd YAG laser and a tunable dye laser. From the ratio of third-harmonic intensities I3m from the PAV films and a fused quartz plate ( 1 thick) as a standard, the value of x(3) was estimated according to the following equation derived by Kajzar et al. [33] ... 

One which produces pulses of the order of 10 ns and is usually pumped by a Q-switched Nd-YAG laser. 

The nonlinear optical properties of the films were subsequently investigated using second-harmonic generation. A Q-switched Nd YAG laser (A = 1064 nm) with a pulse width of 8 ns and a pulse... 

The experimental apparatus used to measure SHG intensities has been previously described (4-6). Light was generated by a q-switched Nd YAG laser with a 1.064 pm fundamental (yielding the SHG signal wavelength of 532 nm). The beam was split so that a y-cut quartz reference and the sample were tested simultaneously. 

Fig. 3.2. SH rotational anisotropy from a Si(lll) surface in air. Excitation was with p-polarized 532 nm light from a Q-switched Nd YAG laser incident at 45° from the surface normal. The rotation angle lies between the x axis in the plane of incidence and the [100] projection axis on the surface. (a) S-polarized SH data (solid line) and theoretical fit (dashed line) to Eq. (3-10) (with A = 0). (b) P-polarized SH data and theoretical fit to Eq. (3-10) (with B = -A). From Ref. 67 and also shown in Ref. 68 with a different definition of the angle of rotation.

The T-jump pulse is generated by Raman shifting the fundamental output of a Q-switched Nd YAG laser (1 = 1.064 pm) in a 1-m-long Raman cell filled with H2 at 500 psi. The laser operates at a repetition rate of 10 Hz and has a pulse temporal width of <10 ns (FWHM). The Stokes shift in H2 is 4155 cm-1. As a result, the first Stokes line is at a wavelength of 1.9 pm that is partially absorbed by the D20 solvent, and thus serves as the T-jump pulse. A Pellin-Broca prism is used to separate the... 

An example of quasi CW THz detection [86] uses a THz wave parametric oscillator (TPO) consisting of a Q-switched Nd YAG laser and parametric oscillator [87,88], In this technique, MgO LiNb3 is employed as a non-linear material to generate CW THz. Silicon prisms couple the THz radiation from the non-linear crystal where it is detected using a pyroelectric detector. THz images are collected at discrete THz frequencies and then spectroscopically analyzed using a component spatial pattern analysis method to determine sample composition. 

Figure 4-12 Lower trace ground-state RR spectrum of Rh2b obtained by CW excitation at 530.9 nm. Upper trace excited-state RR spectra of Rh2b4+ obtained by pulsed laser excitation with the second harmonic of the Q-switched Nd YAG laser (531.8 nm). (Reproduced with permission from Ref. 28. Copyright 1981 American Chemical Society.)...

We have performed Raman echo experiments using synchronously pumped dye lasers, followed by dye amplifiers pumped by a Q-switched Nd YAG laser (Fig. 7). These systems are standard (127-129), but several... 

Figure 6 Block diagram of the two-color optical parametric amplifier (OPA) and IR-Raman apparatus. CPA = Chirped pulse amplification system Fs OSC = femtosecond Ti sapphire oscillator Stretch = pulse stretcher Regen = regenerative pulse amplifier SHGYAG = intracavity frequency-doubled Q-switched Nd YAG laser YAG = diode-pumped, single longitudinal mode, Q-switched Nd YAG laser KTA = potassium titanyl arsenate crystals BBO = /J-barium borate crystal PMT = photomultiplier tube HNF = holographic notch filter IF = narrow-band interference filter CCD = charge-coupled device optical array detector. (From Ref. 96.)...

Technological advances, i. e. cw pumped acousto-optically Q-switched Nd YAG lasers with repetition rates of up to 5 kHz combined with multichannel detection systems have increased the ease of obtaining hyper Raman signals. By making use of this advanced technology, hyper Raman spectra of benzene and pyridine could be obtained by Ned-dersen et al. (1989). Spectra from benzene, deuterated benzene and carbon tetrachloride have been obtained with high signal-to-noise ratios by Acker et al. (1989). As example, we show in Fig. 6.1-17 the hyper-Raman spectra of benzene and deuterated benzene. 

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