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Simple and Efficient Method for Rejecting Elastic Light Scatter Background in Inelastic, Polarized Light Scattering Microprobe Spectroscopy

IP.com Disclosure Number: IPCOM000110139D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 86K

Publishing Venue

IBM

Related People

Epperlein, PW: AUTHOR

Abstract

Raman microprobe spectroscopy, i.e., inelastic light scattering spectroscopy with high spatial resolution (< 2 mm), requires to use lenses with high numerical apertures (> 0.5). This leads to employ the same optics for focussing the probe laser beam as well as for collecting the scattered light. This scheme therefore suffers from the fact that the strong elastically scattered Rayleigh light and the extremely weak, inelastically scattered Raman light, which carries the information of interest, enter together the detection system. Different filter systems are commercially available to extract the low Raman response signal from the large elastic scatter background. However, these filter systems have a lot of severe drawbacks, such as: 1. rejection of Rayleigh scattered light in notch region of filter is not sufficient 2.

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Simple and Efficient Method for Rejecting Elastic Light Scatter Background in Inelastic, Polarized Light Scattering Microprobe Spectroscopy

       Raman microprobe spectroscopy, i.e., inelastic light
scattering spectroscopy with high spatial resolution (< 2 mm),
requires to use lenses with high numerical apertures (> 0.5).  This
leads to employ the same optics for focussing the probe laser beam as
well as for collecting the scattered light.  This scheme therefore
suffers from the fact that the strong elastically scattered Rayleigh
light and the extremely weak, inelastically scattered Raman light,
which carries the information of interest, enter together the
detection system.  Different filter systems are commercially
available to extract the low Raman response signal from the large
elastic scatter background.  However, these filter systems have a lot
of severe drawbacks, such as:
1.   rejection of Rayleigh scattered light in notch region of filter
is not sufficient
2.   spectral bandwidth of notch region is not sufficiently narrow
3.   edges at notch region are not sufficiently sharp
      Consequences of 1.-3.: only Raman signal with larger energy
shifts is accessible, i.e. essential parts of the Raman spectrum in
the low energy regime cannot be revealed.
4.   transmission outside the notch region (stop band) is nonuniform
and different in the Stokes and anti-Stokes energy regime of the
Raman spectrum.
      Consequences of 4.: correction of Raman spectra with the filter
transmission curves, especially necessary for quantitative
measurements, such as temperature measurements on mirror facets of
operating semiconductor diode lasers.
5.   each filter is designed for only one specific probe laser
wavelength
6.   expensive, limited use, not easy-to-handle

      A novel, efficient method is proposed to reject the interfering
Rayleigh light from detection in Raman microprobe spectroscopy, e.g.,
on (110)-o...