Lasers, Spectrographs, and Detectors - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 10

[22]. This combination of dramatic cost and size reduction has resulted in
broad impact on Raman instrumentation. Raman microscopes, for example,
often now have multiple excitation lasers integrated into the microscope body
with little or no increase in the instrument footprint. There are a variety of
handheld Raman systems that can operate for many hours on battery packs
intended for handheld cameras. Instruments can be taken into the clinic for
in vivo measurements, or integrated into the manufacturing process on the
factory floor. This flexibility also allows facile choice of laser wavelength for
specific measurements; for instance, fluorescence from the heme complex can
be minimized by exciting at 830 nm rather than at 785 nm [23]. Laser wave-

length can also be selected for resonant enhancement of specific vibrational
bands, or to maximize the enhancement from different SERS substrates. The
expense, availability, and cumbersome nature of the laser are no longer limit-
ing factors in Raman spectroscopy; rather, selection of the laser is a key factor
in optimizing the results for a given application.

∼

1.4 Sample Presentation

Although the other components of the Raman spectrometer are always high-
lighted as the most technically important, many important innovations have
been applied to optimizing and amplifying the signal by improving how
the sample interfaces between the excitation laser and the spectrometer. In
Fig. 1.1, this component would be represented by the arrow connecting the
light source with the sample, and the sample with the dispersion element.
Because different variations will be treated in detail in upcoming chapters on

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1

0.1

200 400 600 800 1000 1200

Excitation Wavelength (nm)

Fig. 1.5. Correlation of laser wavelength with scattering intensity