Abstract

A new fibre-optic coupled polarization-resolved Raman spectroscopic system was developed for simultaneous collection of orthogonally polarized Raman spectra in a single measurement. An application of detecting incipient dental caries based on changes observed in Raman polarization anisotropy was also demonstrated using the developed fibre-optic Raman spectroscopic system. The predicted reduction of polarization anisotropy in the Raman spectra of caries lesions was observed and the results were consistent with those reported previously with Raman microspectroscopy. The capability of simultaneous collection of parallel-and cross-polarized Raman spectra of tooth enamel in a single measurement and the improved laser excitation delivery through fibre-optics demonstrated in this new design illustrates its future clinical potential.

© 2008 Optical Society of America

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References

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  1. J. Bader, "Diagnosis and management of dental caries," Number 36. AHRQ Publication No.01-E055, February 2001. Rockville, MD: Agency for Healthcare Research and Quality.
  2. A. I. Ismail, "Visual and Visuo-tactile detection of dental caries," J. Dent Res. 83, C56-C66 (2004).
    [CrossRef] [PubMed]
  3. A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
    [CrossRef] [PubMed]
  4. E. de Josselin de Jong, F. Sundström, H. Westerling, S. Tranaeus, J. J. ten Bosch and B. Angmar-Månsson; "A new method for in vivo quantification of changes in initial enamel caries with laser fluorescence," Caries Res. 29, 2-7 (1995).
    [CrossRef] [PubMed]
  5. G. K. Stookey, R. D. Jackson, A. G. Zandona, and M. Abaloui, "Dental caries diagnosis," Dent. Clin. North Am. 43, 665-677 (1999).
    [PubMed]
  6. J. M. Girkin, A. F. Hall, and S. L. Creanor, "Two-photon imaging of intact dental tissue," Dental Caries 2, 317-325 (2000).
  7. K. Kaneko, K. Matsuyama, and S. Nakashima, "Quantification of early carious enamel lesions by using an infrared camera in vitro," in Proceedings of the 4th annual Indiana conference, G. K. Stookey, ed., (Indiana University School of Dentistry, Indianapolis, Indiana 1999) pp. 83-100.
  8. D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
    [CrossRef] [PubMed]
  9. B. T. Amaechi, S. M. Higham, A. G. Podoleanu, J. A. Rogers, and D. A. Jackson, "Use of optical coherence tomography for assessment of dental caries: quantitative procedure," J. Oral Rehabil. 28, 1092-1093 (2001).
    [CrossRef]
  10. W. Hill and V. Petrou, "Caries detection by diode laser Raman spectroscopy," Appl. Spectrosc. 54, 795-799 (2000).
    [CrossRef]
  11. A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
    [CrossRef] [PubMed]
  12. R. S. Jones, G. D. Huynh, G. C. Jones, and D. Fried, "Near-infrared transillumination at 1310-nm for the imaging of early dental decay," Opt. Express 11, 2259-2265 (2003).
    [CrossRef] [PubMed]
  13. C. M. Bühler, P. Ngaotheppitak, and D. Fried, "Imaging of occlusal dental caries (decay) with near-IR light at 1310-nm," Opt. Express 13, 573-582 (2005).
    [CrossRef] [PubMed]
  14. G. K. Stookey, "Optical Methods??Quantitative Light Fluorescence," J. Dent. Res. 83, C84-C88 (2004)
    [CrossRef] [PubMed]
  15. A. C. -T. Ko, L. -P. Choo-Smith, M. Hewko, M. G. Sowa, C. C. S. Dong, and B. Cleghorn, "Detection of early dental caries using polarized Raman spectroscopy," Opt. Express 14, 203-215 (2006).
    [CrossRef] [PubMed]
  16. G. A. Thomson, K. J. Baldwin, and D. N. Batchelder, "Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectra," J. Raman Spectrosc. 34, 345-349 (2003).
    [CrossRef]
  17. C. Bremard, P. Dhamelincourt, J. Laureynes, and G. Turrell, "The effect of high-numerical-aperture objectives on polarization measurements in micro-Raman spectrometry," Appl. Spectrosc. 39, 1036-1039 (1985).
    [CrossRef]

2006

2005

C. M. Bühler, P. Ngaotheppitak, and D. Fried, "Imaging of occlusal dental caries (decay) with near-IR light at 1310-nm," Opt. Express 13, 573-582 (2005).
[CrossRef] [PubMed]

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

2004

G. K. Stookey, "Optical Methods??Quantitative Light Fluorescence," J. Dent. Res. 83, C84-C88 (2004)
[CrossRef] [PubMed]

A. I. Ismail, "Visual and Visuo-tactile detection of dental caries," J. Dent Res. 83, C56-C66 (2004).
[CrossRef] [PubMed]

2003

G. A. Thomson, K. J. Baldwin, and D. N. Batchelder, "Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectra," J. Raman Spectrosc. 34, 345-349 (2003).
[CrossRef]

R. S. Jones, G. D. Huynh, G. C. Jones, and D. Fried, "Near-infrared transillumination at 1310-nm for the imaging of early dental decay," Opt. Express 11, 2259-2265 (2003).
[CrossRef] [PubMed]

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

2001

B. T. Amaechi, S. M. Higham, A. G. Podoleanu, J. A. Rogers, and D. A. Jackson, "Use of optical coherence tomography for assessment of dental caries: quantitative procedure," J. Oral Rehabil. 28, 1092-1093 (2001).
[CrossRef]

2000

W. Hill and V. Petrou, "Caries detection by diode laser Raman spectroscopy," Appl. Spectrosc. 54, 795-799 (2000).
[CrossRef]

J. M. Girkin, A. F. Hall, and S. L. Creanor, "Two-photon imaging of intact dental tissue," Dental Caries 2, 317-325 (2000).

1999

G. K. Stookey, R. D. Jackson, A. G. Zandona, and M. Abaloui, "Dental caries diagnosis," Dent. Clin. North Am. 43, 665-677 (1999).
[PubMed]

1997

A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
[CrossRef] [PubMed]

1995

E. de Josselin de Jong, F. Sundström, H. Westerling, S. Tranaeus, J. J. ten Bosch and B. Angmar-Månsson; "A new method for in vivo quantification of changes in initial enamel caries with laser fluorescence," Caries Res. 29, 2-7 (1995).
[CrossRef] [PubMed]

1985

Abaloui, M.

G. K. Stookey, R. D. Jackson, A. G. Zandona, and M. Abaloui, "Dental caries diagnosis," Dent. Clin. North Am. 43, 665-677 (1999).
[PubMed]

Amaechi, B. T.

B. T. Amaechi, S. M. Higham, A. G. Podoleanu, J. A. Rogers, and D. A. Jackson, "Use of optical coherence tomography for assessment of dental caries: quantitative procedure," J. Oral Rehabil. 28, 1092-1093 (2001).
[CrossRef]

Arnone, D.

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

Baldwin, K. J.

G. A. Thomson, K. J. Baldwin, and D. N. Batchelder, "Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectra," J. Raman Spectrosc. 34, 345-349 (2003).
[CrossRef]

Batchelder, D. N.

G. A. Thomson, K. J. Baldwin, and D. N. Batchelder, "Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectra," J. Raman Spectrosc. 34, 345-349 (2003).
[CrossRef]

Bremard, C.

Bühler, C. M.

Choo-Smith, L. P.

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

Choo-Smith, L. -P.

Ciesla, C. M.

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

Cleghorn, B.

A. C. -T. Ko, L. -P. Choo-Smith, M. Hewko, M. G. Sowa, C. C. S. Dong, and B. Cleghorn, "Detection of early dental caries using polarized Raman spectroscopy," Opt. Express 14, 203-215 (2006).
[CrossRef] [PubMed]

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

Cole, B. C.

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

Crawley, D. A.

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

Creanor, S. L.

J. M. Girkin, A. F. Hall, and S. L. Creanor, "Two-photon imaging of intact dental tissue," Dental Caries 2, 317-325 (2000).

Dhamelincourt, P.

Dong, C. C. S.

A. C. -T. Ko, L. -P. Choo-Smith, M. Hewko, M. G. Sowa, C. C. S. Dong, and B. Cleghorn, "Detection of early dental caries using polarized Raman spectroscopy," Opt. Express 14, 203-215 (2006).
[CrossRef] [PubMed]

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

Driller, J.

A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
[CrossRef] [PubMed]

Elbaum, M.

A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
[CrossRef] [PubMed]

Fried, D.

Girkin, J. M.

J. M. Girkin, A. F. Hall, and S. L. Creanor, "Two-photon imaging of intact dental tissue," Dental Caries 2, 317-325 (2000).

Greenebaum, M.

A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
[CrossRef] [PubMed]

Hall, A. F.

J. M. Girkin, A. F. Hall, and S. L. Creanor, "Two-photon imaging of intact dental tissue," Dental Caries 2, 317-325 (2000).

Hewko, M.

A. C. -T. Ko, L. -P. Choo-Smith, M. Hewko, M. G. Sowa, C. C. S. Dong, and B. Cleghorn, "Detection of early dental caries using polarized Raman spectroscopy," Opt. Express 14, 203-215 (2006).
[CrossRef] [PubMed]

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

Higham, S. M.

B. T. Amaechi, S. M. Higham, A. G. Podoleanu, J. A. Rogers, and D. A. Jackson, "Use of optical coherence tomography for assessment of dental caries: quantitative procedure," J. Oral Rehabil. 28, 1092-1093 (2001).
[CrossRef]

Hill, W.

Huynh, G. D.

Ismail, A. I.

A. I. Ismail, "Visual and Visuo-tactile detection of dental caries," J. Dent Res. 83, C56-C66 (2004).
[CrossRef] [PubMed]

Jackson, D. A.

B. T. Amaechi, S. M. Higham, A. G. Podoleanu, J. A. Rogers, and D. A. Jackson, "Use of optical coherence tomography for assessment of dental caries: quantitative procedure," J. Oral Rehabil. 28, 1092-1093 (2001).
[CrossRef]

Jackson, R. D.

G. K. Stookey, R. D. Jackson, A. G. Zandona, and M. Abaloui, "Dental caries diagnosis," Dent. Clin. North Am. 43, 665-677 (1999).
[PubMed]

Jones, G. C.

Jones, R. S.

Keem, S.

A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
[CrossRef] [PubMed]

Ko, A. C. -T.

Ko, A. C.-T.

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

Laureynes, J.

Leonardi, L.

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

Longbottom, L.

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

Ngaotheppitak, P.

Pepper, M.

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

Petrou, V.

Podoleanu, A. G.

B. T. Amaechi, S. M. Higham, A. G. Podoleanu, J. A. Rogers, and D. A. Jackson, "Use of optical coherence tomography for assessment of dental caries: quantitative procedure," J. Oral Rehabil. 28, 1092-1093 (2001).
[CrossRef]

Rogers, J. A.

B. T. Amaechi, S. M. Higham, A. G. Podoleanu, J. A. Rogers, and D. A. Jackson, "Use of optical coherence tomography for assessment of dental caries: quantitative procedure," J. Oral Rehabil. 28, 1092-1093 (2001).
[CrossRef]

Schneiderman, A.

A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
[CrossRef] [PubMed]

Schultz, T.

A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
[CrossRef] [PubMed]

Sowa, M. G.

A. C. -T. Ko, L. -P. Choo-Smith, M. Hewko, M. G. Sowa, C. C. S. Dong, and B. Cleghorn, "Detection of early dental caries using polarized Raman spectroscopy," Opt. Express 14, 203-215 (2006).
[CrossRef] [PubMed]

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

Stookey, G. K.

G. K. Stookey, "Optical Methods??Quantitative Light Fluorescence," J. Dent. Res. 83, C84-C88 (2004)
[CrossRef] [PubMed]

G. K. Stookey, R. D. Jackson, A. G. Zandona, and M. Abaloui, "Dental caries diagnosis," Dent. Clin. North Am. 43, 665-677 (1999).
[PubMed]

Thomson, G. A.

G. A. Thomson, K. J. Baldwin, and D. N. Batchelder, "Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectra," J. Raman Spectrosc. 34, 345-349 (2003).
[CrossRef]

Turrell, G.

Wallace, V. P.

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

Williams, P.

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

Zandona, A. G.

G. K. Stookey, R. D. Jackson, A. G. Zandona, and M. Abaloui, "Dental caries diagnosis," Dent. Clin. North Am. 43, 665-677 (1999).
[PubMed]

Appl. Spectrosc.

Caries Res.

A. Schneiderman, M. Elbaum, T. Schultz, S. Keem, M. Greenebaum, and J. Driller, "Assessment of Dental caries with Digital Imaging Fiber-Optic Transillumination (DIFOTI): in vitro study," Caries Res. 31, 103-110 (1997).
[CrossRef] [PubMed]

E. de Josselin de Jong, F. Sundström, H. Westerling, S. Tranaeus, J. J. ten Bosch and B. Angmar-Månsson; "A new method for in vivo quantification of changes in initial enamel caries with laser fluorescence," Caries Res. 29, 2-7 (1995).
[CrossRef] [PubMed]

D. A. Crawley, L. Longbottom, B. C. Cole, C. M. Ciesla, D. Arnone, V. P. Wallace, and M. Pepper, "Tetrahertz pulse imaging: a pilot study of potential applications in dentistry," Caries Res. 37, 352-359 (2003).
[CrossRef] [PubMed]

Dent. Clin. North Am.

G. K. Stookey, R. D. Jackson, A. G. Zandona, and M. Abaloui, "Dental caries diagnosis," Dent. Clin. North Am. 43, 665-677 (1999).
[PubMed]

Dental Caries

J. M. Girkin, A. F. Hall, and S. L. Creanor, "Two-photon imaging of intact dental tissue," Dental Caries 2, 317-325 (2000).

J. Biomed. Opt.

A. C.-T. Ko, L. P. Choo-Smith, M. Hewko, L. Leonardi, M. G. Sowa, C. C. S. Dong, P. Williams, and B. Cleghorn, "Ex vivo detection and characterization of early dental caries by optical coherence tomography and Raman spectroscopy," J. Biomed. Opt. 10, 031118 (2005).
[CrossRef] [PubMed]

J. Dent Res.

A. I. Ismail, "Visual and Visuo-tactile detection of dental caries," J. Dent Res. 83, C56-C66 (2004).
[CrossRef] [PubMed]

J. Dent. Res.

G. K. Stookey, "Optical Methods??Quantitative Light Fluorescence," J. Dent. Res. 83, C84-C88 (2004)
[CrossRef] [PubMed]

J. Oral Rehabil.

B. T. Amaechi, S. M. Higham, A. G. Podoleanu, J. A. Rogers, and D. A. Jackson, "Use of optical coherence tomography for assessment of dental caries: quantitative procedure," J. Oral Rehabil. 28, 1092-1093 (2001).
[CrossRef]

J. Raman Spectrosc.

G. A. Thomson, K. J. Baldwin, and D. N. Batchelder, "Raman spectroscopy with simultaneous measurement of two orthogonally polarized Raman spectra," J. Raman Spectrosc. 34, 345-349 (2003).
[CrossRef]

Opt. Express

Other

J. Bader, "Diagnosis and management of dental caries," Number 36. AHRQ Publication No.01-E055, February 2001. Rockville, MD: Agency for Healthcare Research and Quality.

K. Kaneko, K. Matsuyama, and S. Nakashima, "Quantification of early carious enamel lesions by using an infrared camera in vitro," in Proceedings of the 4th annual Indiana conference, G. K. Stookey, ed., (Indiana University School of Dentistry, Indianapolis, Indiana 1999) pp. 83-100.

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Figures (7)

Fig. 1.
Fig. 1.

Schematic overview of the developed fibre-optic coupled polarization-resolved Raman spectroscopic system. Inset shows a view of the distal end of the bifurcated fibre bundle. These two fibres transmit orthogonally polarized Raman signals simultaneously and separately. Spectra shown are parallel- and cross-polarized Raman spectra of sound enamel.

Fig. 2.
Fig. 2.

Representative parallel- (upper trace) and cross-polarized (lower trace) Raman spectra of (A) Si wafer acquired with a ×40 objective lens and (B) CCl4 acquired with a ×10 objective lens. Spectra were slightly offset for clarity.

Fig. 3.
Fig. 3.

Spectra acquired from the fibre-optic coupled Raman system as a function of the Raman signal’s polarization state (A) before and (B) after a polarization scrambler was inserted into the Raman collection path in between the collection PBS and the collection fibre. Spectra shown are parallel-polarized Raman spectra of CCl4. Variation of the Raman signal polarization state was achieved by rotating a λ/2 plate placed immediately after the PBS in the Raman collection path.

Fig. 4.
Fig. 4.

Representative parallel- (upper trace) and cross- (lower trace) polarized Raman spectra of (A) sound enamel (B) caries lesions acquired with the developed system.

Fig. 5.
Fig. 5.

Representative CCD image read-outs of the Raman spectra of (A) sound enamel and (B) caries lesions containing both parallel- (upper channel) and cross- (lower channel) polarized components. Only the area on the CCD detector containing the Raman band at 959 cm-1 was shown.

Fig. 6.
Fig. 6.

Bar graphs of (A) depolarization ratio (ρ959) and (B) polarization anisotropy (A959) obtained from sound enamel versus carious lesion. Mean +/- standard deviation values are shown. N=47 and N=27 for sound enamel and caries lesion, respectively.

Fig. 7.
Fig. 7.

Orthogonally polarized Raman spectra of sound enamel acquired with (A) ×10, N.A.=0.25 (B) ×20, N.A.=0.50 and (C) ×50, N.A.=0.75 objective lens. Only the spectral region between 700 cm-1 and 1300 cm-1 was shown. Increased spectral contrast between the parallel- and cross-polarized Raman spectra of sound enamel was demonstrated with increasing objective lens magnification power with increasing N.A.

Equations (2)

Equations on this page are rendered with MathJax. Learn more.

ρ 959 = I 959 ( ) I 959 ( )
A 959 = ( I 959 ( ) I 959 ( ) ) ( I 959 ( ) + 2 I 959 ( ) )

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