Near-infrared pulse

M. Kohl, C. Nolte, H. R. Heekeren, S. Horst, U. Scholz, H. Obrig, and A. Vill-ringer. Determination of the wavelength dependence of the differential path-length factor from near-infrared pulse signals. Physics in Medicine and Biology, 43 1771-1782, 1998. 

The spatial feature is in excellent agreement with the calculated photonic LDOS at the excitation wavelength. The spatial feature of the image is assigned to the plasmon wavefunction of w = 2 mode. Similarly, a near-tield transmission image taken at 900 nm (Fig. 4.1 Id) is assigned the plasmon wavefunction of w = 1 mode. To examine the ultrafast dynamics in the nanorod, the one-color EPC method was adopted, with near-infrared pulses as the excitation sources. At the excitation wavelength, both the w = 1 and m = 2 modes were excited at the same time. In EPC, the... 

Prevo, B. G. Esakoff, S. A. Mikhailovsky, A. Zasadzinski, J. A. Scalable routes to gold nanoshells with tunable sizes and response to near-infrared pulsed-laser irradiation. SmalllOOS, 4, 1183-1195. 

Shirakawa A, Sakane I and Kobayasi T 1998 Pulse-front-matched optical parametric amplification for sub-10 fs pulse generation tunable in the visible and near infrared Opt. Lett. 23 1292-4... 

Figure 8.1 (a) Block diagram of the femtosecond near-infrared laser microscope system, (b) Spectrum ofthe light pulse from the Cr F laser, (c) Interferometric autocorrelation trace of SHG signal with envelope curve calculated assuming a chirp-free Gaussian pulse with 35 fs fwhm. 

Hare DE, Rhea ST, Dlott DD, D Amato RJ, Lewis TE. 1998. Pulse duration dependence of lithographic printing plate imaging by near-infrared lasers. J Imag Soc Technol 42 90 97. 

The bleaching of carotenoids was simultaneous with the formation of near-infrared absorbing intermediates in the microsecond timescale. The formation of an adduct ion-pair is instantaneous during the laser pulse (<10ns) with maximum absorption in the region 830-950 nm, depending on... 

Even more elegantly, the local resolution is improved by irradiation with very intense focused femtosecond laser pulses outside the absorption range of the fluoro-phore (e.g., in the near-infrared). The very intense focus of the laser beam—and only this—will excite the fluorophore by nonresonant two-photon absorption. Artifacts by scattered primary radiation are ruled out and the local resolution is comparable to a confocal microscope. In addition, the damage of the sample by laser light absorption is reduced to a minimum. 

Experiments were conducted in our laboratory to evaluate many of the dynamical expectations for rapid laser heating of metals. One of the aims of this work was to identify those population distributions which were characteristic of thermally activated desorption processes as opposed to desorption processes which were driven by nontbennal energy sources. Visible and near-infrared laser pulses of nominally 10 ns duration were used to heat the substrate in a nonspecific fashion. Initial experiments were performed by Burgess etal. for the laser-induced desorption of NO from Pt(foil). Operating with a chamber base pressure 2 x 10 torr and with the sample at 200 K, initial irradiation of a freshly cleaned and dosed sample resulted in a short time transient (i.e. heightened desorption yield) followed by nearly steady state LID signals. The desorption yields slowly decreased with time due to depletion of the adsorbate layer at the rate of ca. 10 monolayer... 

The observations of complex dynamics associated with electron-stimulated desorption or desorption driven by resonant excitation to repulsive electronic states are not unexpected. Their similarity to the dynamics observed in the visible and near-infrared LID illustrate the need for a closer investigation of the physical relaxation mechanisms of low energy electron/hole pairs in metals. When the time frame for reaction has been compressed to that of the 10 s laser pulse, many thermal processes will not effectively compete with the effects of transient low energy electrons or nonthermal phonons. It is these relaxation channels which might both play an important role in the physical or chemical processes driven by laser irradiation of surfaces, and provide dramatic insight into subtle details of molecule-surface dynamics. 

Konig, K., Becker, T. W., Fischer, R, Riemaim, L, and Halbhuber, K. J. 1999. Pulse-length dependence of cellular response to intense near-infrared laser pulses in multiphoton microscopes. Opt. Lett. 24 113-15. 

Petrov, G. L, Yakovlev, V. V., and Minkovski, N. I. 2003. Near-infrared continuum generation of femtosecond and picosecond pulses in doped optical fibers. Appl. Phys. B 77 219-25. 

Tunable operation with bandwidth-limited sub-10-fs pulses in the visible (550-700 nm) and near infrared (900-1300 nm) was also performed by changing the seed delay with respect to the pump after increasing the seed chirp [10]. The NOPA is one of most useful light sources for ultrafast spectroscopy in the present stage on an extremely short time scale. 

THG measurements on poly- -butylCOT films, referenced to a bare fused silica plate, were made using 1064 nm pulses. These measurements showed that the l/(3)l values of films of poly-rt-butylCOT, lxl0 10 esu, were comparable to that for unoriented polyacetylene at the same wavelength (39). However, comparison of the linear transmission spectra of these materials in the near infrared shows that the partially substituted polyacetylene has greatly improved optical quality. (See Figure 7.)... 

The complex quantity, y6br = e (y(3)r) + i Im (x r), represents the nuclear response of the molecules. The induced polarization is resonantly enhanced when the Raman shift wp — ws matches the frequency Qr of a Raman-active molecular vibration (Fig. 6.1A). Therefore, y(3)r provides the intrinsic vibrational contrast mechanism in CRS-based microscopies. The nonresonant term y6bnr represents the electronic response of both the one-photon and the two-photon electronic transitions [30]. Typically, near-infrared laser pulses are used to prevent the effect of two-photon electronic resonances. With input laser pulse frequencies away from electronic resonances, y(3)nr is independent of frequency and is a real quantity. It is important to realize that the nonresonant contribution to the total nonlinear polarization is simply a source for an unspecific background signal, which provides no chemical contrast in some of the CRS microscopies. While CARS detection can be significantly effected by the nonresonant contribution y6bnr [30], SRS detection is inherently insensitive to it [27, 29]. As will be discussed in detail in Sects. 6.3 and 6.4, this has major consequences for the image contrast mechanism of CARS and SRS microscopy, respectively. 

By taking advantage of the deep penetration depth offered by CARS microscopy with near-infrared laser pulses, CARS tissue imaging has been demonstrated to complement other label-free optical techniques, such as auto-fluorescence that is limited to a few chemical species and optical tomography, second harmonic generation (SHG), and third harmonic generation (THG)... 

Low energy initiation techniques [179, 180, 181] (near infrared, ultrasonic radiation and line tuneable pulse laser) have lately emerged to be better alternatives to the high-energy radiations (y-irradiation and e-beam). Laser-induced polymerisation of monomers have attracted significant attention in recent years generating a considerable literature published on both pulsed... 

Yamakoshi K, Yamakoshi Y. Pulse glucometry a new approach for noninvasive blood glucose measurements using instantaneous differential near-infrared spectrophotometry. Journal of Biomedical Optics 2006, 11, 054028. 

Figure 8.11 (a) Emission of second-harmonic signal from transferred MONHP4 nanofibers and from p6P nanofibers on muscovite mica after excitation with femtosecond near-infrared laser pulses (lOOfs, 4.5 mW) at 790nm. (b) Emission of second-harmonic signal from MOCLP4... 

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