NIR laser

From these vievqjoints, we have developed a femtosecond NIR laser microscope with a home-built cavity dumped chromium forsterite (Cr F) laser as an excitation light source whose output wavelength is centered at 1260 run. In the following the set-up of the NIR laser microscope and its application to multiphoton imaging are presented. 

Figure 8.2a-c shows optical transmission images of organic microcrystals of perylene, anthracene, and pyrene, excited at a laser power of 1.7 nj pulse under similar excitation conditions as in Figure 8.1c. The bright spots <2 pm in diameter at the center of each microcrystal were areas irradiated with the NIR laser pulse.

Figure 8.8 Typical fluorescence autocorrelation curves of R6G in ethylene glycol (a) and R123 in water (b) without the NIR laser light with calculated curves (solid line) based on Eq. (8.1) and residuals. Fluorescence autocorrelation curves of R6G in ethylene glycol (c) and R123 in water (d) under irradiation of the NIR laser at several powers up to 240 mW. The inset of Figure 8.8d shows a magnified view of a partofthe figure enclosed by a rectangle.

With the aim of elucidating molecular dynamics in a small domain, we have constmcted several microspectroscopic systems, that is, (i) the confocal microscope with the excitation light source being a femtosecond NIR laser emitting a 35 fs pulse, and (ii) the fluorescence correlation spectroscopic system with optical tweezers. 

The NIR fluorescent 2,3-dihydroperimidine-squaraines 35a,b were synthesized and used as biological labels [99]. Dye 35b including four sulfopropyl groups exhibits high water-solubility, an emission maximum at 812 nm (protein ratio D/P = 1), and 817 nm in the presence of BSA, which indicates compatibility with commercially available NIR laser diodes. 

Bis( 1,2-dithiolene) complexes are generally thermally and photochemically very stable, and their Vis-NIR absorption can be tuned in order to reach the wavelength ranges of interest for NIR lasers, such as Nd YAG, Nd YLF, and Er Glass solid-state lasers (emission wavelengths A.em = 1064, 1053, and 1540 nm, respectively). In this context, many groups of researchers have devoted their efforts to synthesising 1,2-dithiolene complexes for this type of application, and indeed some of them have been patented and are commercially... 

Raman signal intensity is proportional to the fourth power of the inverse of the incident wavelength. As Table 7.1 illustrates, the use of a 785nm NIR laser instead of an ultraviolet (UV) one at 480nm means that only 14% of the possible photons could be generated. It is desirable to use the shortest laser wavelength possible to maximize the number of Raman photons available for detection. 

Luminescence of Mn " " was not detected in minerals yet, but is well known in phosphors. The first possibility will be barite (Fig. 5.39), because BaS04-Mn has IR luminescence and is considered as a potential material for a tunable NIR laser (Brunold and Giidel 1997 Brunold et al. 1997). 

Consequently such a microvaporizer uses a glass-silicon-glass stack with a microstructured silicon evaporator. This evaporator is heated up by a pulsed NIR-laser diode. Thus, the liquids which are in contact with the evaporator within a very short period of time are heated beyond their evaporation temperature. This arrangement not only requires a low energy to evaporate in comparison to the commonly used resistive heating, but the very rapid heating of the silicon vaporizer also allows for simultaneous evaporation of sample mixtures with components of different evaporation temperatures and partial pressures, respectively. Furthermore,... 

Since NIR laser radiation is invisible, it is advisable - while wearing. safety glasses -to employ an infrared night vision instrument with a macro lens for the fine-adjustment of the sample. 

The excitation of the surface plasmon effect also induces strongly enhanced fluorescence properties of gold nanoparticles due to the enhanconent in the radiative rate of the inter-band electronic transitions relative to that in bulk metals. Metal nanoparticles, especially gold nanorods exhibit enhanced two-photon luminescence (TPL) and multi-photon luminescoice (MPL) [7, 8]. Strongly-enhanced TPL has been observed from individual particles [9, 10] and particle solutions [11] under femtosecond NIR laser excitation. This observation raises the possibility of nonlinear optical imaging in the NIR region, where water and biomolecules have... 

Although metal nanoparticles experience strong radiation pressure and scattering forces due to their high absorption and polarizability, stable trapping of such particles has been demonstrated in both two and three dimensions [74, 85, 86]. As for cells and dielectric particles, a NIR laser is usually used to trap metal nanoparticles while a separate laser, or the trapping laser itself, excites the... 

For larger aggregates, stronger enhancement is expected. The work by Tanaka et al. [89] showed that silver nanoparticles simultaneously trapped by a NIR laser beam also tend to ahgn parallel to the linear polarization, and it exhibited pronounced SERS signal at a very low concentration of probe molecules, 10 " M pseudoisocyanine (PIC) excited by a separate laser beam, whereas no SERS appeared if the trapping laser was not focused in the solution. 

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