Chemistry Reference
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the fi ber probe through one of the holes of an endoscope. The diameter
of the fi ber probe in this case must be smaller than 2.0 mm. The other
is to introduce the fi ber probe directly through a thoracoscope. It is
often necessary to use a thoracoscope in order to reach the deep
part of the lung far from the bronchi. The fi ber probe to be used
with a thoracoscope can have a considerably larger diameter, up to
10 mm.
Here we show a thick fi ber Raman probe that we use for routine
measurements of fresh human lung tissues and skins. It is based on a
custom - made 10 - mm Raman probe for 1064 -nm excitation (InPhoton-
ics, Inc., Norwood, MA; Figure 10.3) consisting of a 100-
μ
m excitation
m collection fi ber. For easier insertion into a human
body, the probe tube is made to be 25 cm long. A sapphire ball lens (1-
mm focal length) is attached to the end of the probe to measure Raman
scattering from a fi xed contact point. By assembling a band pass fi lter,
dichroic mirror, edge fi lter, and lenses, the Raman signals from the fi ber
itself can be completely blocked. The collection fi ber is directly con-
nected to the polychromator with a fi ber coupler.
With this thick 10- mm diameter probe, near - infrared Raman spectra
of fresh human lung tissues were measured under the conditions of
35-mW laser power and 10-minute exposure time. We have also tested
a short probe tube (
L
= 5 cm) assembled with an aspherical lens
(
f
= 4.5 mm). We were able to improve the experimental conditions to
22-mW laser power and 3-minute exposure time with the use of this
short version of the Raman probe. We are now developing a high-
throughput, long, thick fi ber probe without using a hollow tube.
fi ber and a 300-
μ
Laser beam
1064-nm
Nd:YAG
Polychromator
and NIR Raman
detector
Optics assembly
Optical fiber probe
InP/InGaAsP
Probe tube
Sample
Figure 10.3
Near-infrared (NIR) fi ber Raman spectroscopy with the long, thick
optical fi ber probe.
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