Dispersion compensation

The potential of broadband laser excitation and fs-pulse shaping for different microspectroscopy techniques ranges from pure dispersion compensation (in the case of SHG, THG), to highly functional pulse shaping (in the case of CARS), as summarized in Table 7.2. It is worth mentioning again that all techniques can be implemented in the same approach—broadband laser and pulse shaper. The detection technique of choice is just selected by the corresponding pulse shapes. 

Dispersion compensation to ensure highest peak intensities... 

It is important to realize that dispersion compensation can eliminate the high-order phase distortions (in the spectral domain) introduced by the objective lens, as discnssed above, but it cannot eliminate the scattering (in the spatial domain) that occnrs in depth imaging. Here we explore the nse of laser pulses that are dispersion compensated only before the medinm. In principle, it is possible to compensate for dispersion at greater depths, bnt if the dispersion of tissues is similar to that of pure water, it should be insignificant. Finally, we could titrate the amount of laser power nsed, increasing the intensity as the focal plane moves deeper into the tissue. 

The resnlts from the depth-resolved imaging strongly support our hypothesis that dispersion compensation, especially when nsing pulses shorter than 20 fs, can... 

FIGURE 8.5 Effect of dispersion compensation in two-photon depth imaging. Image acquisition of thick mouse kidney sample collected in a series of z-sections at different depths, which demonstrates that MIIPS compensated pulses attain better signal, and deeper penetration than those with GDD-only compensation. The image size is about 100 pm. The objective used is Nikon 60 x 1.45 NA, with working distance of 130 pm. (From Xi et al. Opt. Comm. 281(7) 1841-1849, 2008. Used with permission.)... 

Various types of optical fibers are used for specific applications. For example, multimode fibers are used primarily in enterprise systems buildings, offices, campuses. Special single-mode transmission fibers exist for submarine applications, and for metropolitan and long-haul terrestrial applications. And in addition to these transmission fibers, there are various specialty fibers for performing dispersion compensation (dispersion compensating fiber), optical amplification (erbium-doped fiber), and other special functions. 

The beam was passed through a pulse picker (4). In order to compensate pulse broadening ( chirp ) introduced by the pulse picker and to precompensate that caused by other bulky optics (lenses, polarizers etc.), the beam was passed through a group velocity dispersion compensation line (5), consisting of a pair of Brewster prisms and a mirror [20], The temporal width of the pump and probe pulses was checked with a fringe-resolved... 

Figure 1 OHD-RIKES experimental setup. DX = Doubling crystal GLP = Gian laser polarizer GTP = Glan-Thompson polarizer HWP = half-wave plate PD = photodiode PDC = prism dispersion compensator QWP = quarter-wave plate SF = spatial filter. (From Ref. 34.)...

Time resolved hole burning spectra were measured by means of a femtosecond transient absorption spectrometer system. A second harmonics of a mode locked cw Nd + YAG laser (Quantronix, 82MHz) was used for a pumping source. A synchronously pumped rhodamine 6G dye laser with a saturable absorber dye jet (DODCl/DQOCI) and dispersion compensating prisms in the cavity was used. The output of the dye laser (lOOfs fwhm, 600pJ/pulse) was... 

Griiner-Nielsen, L., Knudsen, S., Edvold, B. et al.. Dispersion compensating fibers. Opt. Fiber TechnoL, 6, 164, 2000. 

Birks, T., Mogilevtsev, D., Knight, J. et al.. Dispersion compensation nsing single-material fibers, IEEE Photon. TechnoL Lett., 11, 674, 1999. 

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