HeNe laser

There are many potential paths for revitalizing old methods of test using new array detectors and powerful processors. The only reason most testing is done by unequal path interferometry is due to the invention of the HeNe laser. If its development had been delayed a year or two and computing capabilities had been a little more advanced, most optical testing would be done with slope measuring, common path techniques that are less sensitive to the environment. 

The theoretical lateral spatial resolution achievable with Raman imaging using the optical arrangements of our system (50 x objective with NA = 0.75, 633 nm HeNe laser) should be about 1 pm. In this investigation the resolution is worse than predicted. In practice, sample drift during long acquisition times, uneven surface structures and penetration of laser light into the material worsen the lateral spatial resolution to a value of about 2 pm (estimated). 

Image plates use stimulated luminescence from storage phosphor materials. The commercially available plates are composed of extremely fine crystals of BaFBrEu2+. X-rays excite an electron of Eu2+ into the conduction band, where it is trapped in an F-center of the barium halide with a subsequent oxidation of Eu2+ to Eu3+. By exposing the BaFBrEu" complex to light from a HeNe laser the electrons are liberated with the emission of a photon at 390 nm [38]. 

In conventional chip experiments, fluorescence scanners are used for chip read-out. In the case of laser scanners, HeNe lasers are used as excitation sources and photomultiplier tubes as detectors, whereas CCD-based scanners use white light sources. The optical system can be confocal or non-confocal. Standard biochip experiments are performed using two fluorescent labels as... 

Neon (Ne), 17 344. See also Helium-neon (HeNe) lasers commercial, 17 368t thermophysical properties, 8 Alt Neon atoms, 14 659-660 Neon column, 17 361... 

Excitation spectra of D API and Hoechst 3 3 342 are too short for most of the lasers and mirrors that are supplied with commercially available laser scanning microscopes, although these dyes can be imaged in conventional fluorescence microscopes with Xenon or Mercury arc discharge lamp or when using HeNe laser/UV system or multiple photon microscopy... 

CIR-FTIR spectroscopy provides a direct technique for studying in situ hydrous metal oxide surfaces and molecules adsorbed on these surfaces (37). By itself, FTIR spectrometry is a well established technique which offers numerous advantages over dispersive (grating) IR spectrometry (1) improved accuracy in frequency measurements through the use of a HeNe laser (2) simultaneous frequency viewing (3) rapid, repetitive scanning which allows many spectra to be collected in a small time interval (4) miriimal thermal effects from IR beam and (5) no detection of sample IR emissions (38). 

The dependence of spatial resolution on the charge state of the electrode in mode 4 is visualized in Fig. 4.17 d-g. A red HeNe laser and a slit have been used to project a diffraction pattern on an n-type sample surface as shown in the inset... 

The use of fluorescence from alexandrite for temperature sensing was first reported by Augousti etal.(57,5S) using a low-power LED or a HeNe laser with a rather inefficient modulation accessory made of a bulky, high-voltage controlled Pockels cell,... 

The helium-neon (HeNe) laser immediately comes to mind, having a very useful spectral line at 633 nm for steady-state red/near-IR fluorescence studies. Kessler and Wolfbeis have demonstrated the fluorescence assay of the protein human serum albumin using the probe albumin blue excited with a red HeNe laser.(71) Another useful wavelength available from the green HeNe laser is at 543.5 nm and this has been used with phase-modulation fluorometry by Lakowicz etal. to study probes such as carboxy seminaphtorhodafluor-6 (SNARF-6) as a means of measuring pH.(72)... 

However, unlike diode lasers, an external acousto-optic or electro-optic modulator is required for phase-modulation lifetime fluorometry to be performed with a HeNe laser. 

As demonstrated here, one can measure all the four analytes of interest with a green HeNe laser. Importantly, energy transfer concepts allow the use oflonger-wave-... 

FIAs can be based on steady-state intensity measurements without probe amplification, owing to the sensitivity of detection that is possible with fluorescence instrumentation, which exceeds that of spectrophotometers by two or three orders of magnitude. A sensitive fluorometer has been described for an estradiol assay(36) in which the limit of estradiol detection is 3 x KT11 M. Estradiol antibody labeled with rhodamine B is reacted with estradiol samples. Unreacted labeled antibody is removed with Sepharose-estradiol-casein beads, and the remaining fluorescence is directly proportional to the analyte concentration. The detection limit of rhodamine B on the same fluorometer is 5 x 1(T12 M. This instrument uses a 0.75 mW green helium-neon (HeNe) laser to irradiate the sample from above, at the air-liquid interface, to increase the light path and to decrease surface reflections. The sample compartment has a top-mounted photon trap, and a mirror mounted on the side of the sample compartment opposite the PMT to enhance detection. 

Fig. 7.18 (continued) (c) Light scattering apparatus used to detect polymer-polymer demixing 1 - HeNe laser, 2 - sapphire window, 3 - polymer film, 4 - photodiode array, 5 - copper block, 6 - resistance thermometer, 7 - temperature controlled jacket, (Reproduced with permission from Zywocinski, A., et al. J. Polymer Sci. Polym. Phys. 33, 595 (1995))... 

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