Beam expander

As said earlier in this chapter, the use of properly arranged ilkunination will improve the visibility of the smoke markedly. Extra light should be arranged so that the light beams ace directed almost directly into the eyes of the observer or into the lens of a camera. Direct dazzling must be avoided with tlie help of some shield. The use of a laser beam expanded to a sheet makes it possihle to isualize the airflow in a special layer in the room. This technique makes it possible to study the airflow in more detail, e.g, near an enclosure or around a machine. ... 

The particle size analyzer, based on laser light diffraction, consists of a laser source, beam expander, collector lens, and detector (Fig. ] 3.45). The detector contains light diodes arranged to form a radial diode-array detector. The particle sample to be measured can be blown across the laser beam (dry sample), or it can be circulated via a measurement cell in a liquid suspension. In the latter case, the beam is direaed through the transparent cell. 

Fia. 13. (a) Raman spectrum of a pretreated Cab-O-Sil disk recorded using a laser beam expander (b) infrared spectrum of a newly pressed Cab-O-Sil disk. From Hendra and Gilson, Laser Raman Spectroscopy, p. 186. Wiley, New York, 1970. 

Fig, 23. The Oriel model B-34-40 laser beam expander. (Courtesy Oriel Corp.)... 

The use of a laser beam expander as a spatial filter has also been found to be satisfactory 42). The beam expander consists of an interchangeable negative input lens and a positive output lens. Both the input and output lenses are designed for minimum spherical aberration. The expansion power may be varied by using a different input lens (Fig. 23.) The laser beam... 

Fig. 24. The laser beam expander in the Cary 81 spectrometer (exaggerated). Only that part of the expanded plasma light transmitted through the expander is shown.

The laser beam expander will also be used to minimize local heating which may result from absorption by either colored adsorbates (e.g. some carbonium ions) or colored adsorbents (e.g. some vanadium oxides). 

Obviously, the lowering in intensity of the laser beam incident through the beam expander must be compensated for by increasing the source output power. However, it has been found that the intensity loss when using the beam expander is less than that encountered with interference filters. 

FIGURE 10.10 An experimental system of tip-enhanced CARS microscopy. See the text for detail. ND nentral-density filter, P polarizer, DM dichroic mirror, BE beam expander, BS beam splitter, APD avalanche photo diode. 

Figure 6. Instrumental schematic for vacuum UV photofragmentation-laser induced fluorescence measurement of ammonia SHGC, second harmonic generation crystal SFMC, sum frequency mixing crystal BS, beam splitter BD, beam dump TP, turning prism CL, cylindrical lens R, reflector TD, trigger diode OSC, oscillator cell AMP, amplifier cell BE, beam expander G, grating OC, output coupler M, mirror BC, beam combiner L, lens A, aperture PD, photodiode SC, sample cell RC, reference cell FP, filter pack SAM.PMT, sample cell photomultiplier REF.PMT, reference cell photomultiplier PP, additional photomultiplier port EX, exhaust and CGI, calibration gas inlet to flow line. (Reproduced with permission from reference 15. Copyright 1990 Optical Society of America.)...

The LPA instrument of Mount (42) uses a XeCl laser to monitor absorption near the Qi(S) line group. The laser beam, expanded in a telescope to an initial area of 150 cm2, is reflected from a retroreflector array for a total optical path of 20.6 km. The returned beam and a portion of the outgoing beam follow symmetric paths through an echelle spectrograph to a pair of photodiode array detectors, thus providing both I and Z0 spectra for the... 

Artifacts in our instrument can arise from a variety of sources [110,118]. Consequently, before ROA measurements are carried out, a careful alignment of the scattering geometry and optical path is essential. Further reduction of artifacts is achieved by adjustment of the polarization states, the position of the beam expander, the focusing lens and the two QWPs. The beam expander reduces the likelihood that small, local imperfections in optical components will... 

Fig. 14.6. Three-dimensional view of the Teramobile. (L) Laser system Ti Sa oscillator and its Nd YAG pump laser LI), stretcher (L2), regenerative amplifier, multipass preamplifier (L3) and their Nd YAG pump laser (LJ,) Multipass main amplifier (L5) pumped by two Nd YAG units (L6) Compressor (L7). (5), Beam expanding system (C), Power supplies D), Lidar detection system [14]...

Fig. 14. Optical arrangement for holographic experiment (after Qu et al., 1985). 1, ruby laser 2, beam expander 3, collimating lens 4, mirror 5, particle field 6, lens 1 7, lens 2 8, recording film.

Each sample has its own independent interferometer associated with it. A 5 mW red HeNe laser [Spectra Physics] is used as the energy source for the four interferometers that are in the system. The incident beam is split twice in order to provide incident beams to each of the independent interferometers. Each interferometer consists of a 50/50 beamsplitter, four mirrors [including two mirrors at 45°under the reactor to direct the beam into the reactor], and a beam expander in addition to the sample and reference mirrors located in the reactor. All of the optics have a flatness specification of X/10. The mirrors which make up the interferometer components outside of the reactor are enhanced aluminum. The 45° mirrors have adjustment screws so that the sample and reference beams can be aligned from outside the system once a run is started. 

Spike filter / Spatial filter / Pre-monochromator Beam expander... 

Figure 3.19. Absolute determination of 8 by in situ autocorrelation. Experiments were performed with a mode locked femtosecond Ti sapphire laser. A prism pair (PC) was used to compensate the group delay dispersion (GDD) of the microscope objective. A long-pass filter eliminates residual argon pump light and Ti sapphire fluorescence. After two sequential beam expanders (BE), the beam was approximately 25 mm in diameter, which was sufficient to overfill the back aperture (10-mm diameter) of the objective. A long-pass dichroic mirror (DC) with reflectivity separates fluorescence from excitation light. The incident power at the sample was measured by recollimating the transmitted beam onto a calibrated power meter. Fluorescence was detected by a photomultiplier tube and recorded as a function of the interferometer delay. (From Ref. [366] with permission of the Optical Society of America.)...

Figure 35.3 Schematic layout for a dual-trap optical tweezers system. BE, beam expander WP, half-wave plate PBS, polarizing beam-splitting cube LI, L2, lenses 1,2 M, Mirror OL, objective lens DM, dichromic mirror.

Figure 4. Prototype blushmeter (1) laser (2) beam expander (3) mirror (4) panel on sample table (5) lens (6) photoamplifier...

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