Abstract

Structure at and near the surface of a transparent sample or in a film on a transparent substrate can be observed by illuminating the sample from within using a well-collimated polarized laser beam incident at an angle equal to or greater than the critical angle of the sample material and examining the air side of the surface using an optical microscope. Although the technique is similar to dark-field microscopy, additional information can be obtained here concerning the size and depth of scattering sites on or near the surface. This technique, total internal reflection microscopy (TIRM), is complementary to phase contrast (Nomarski) microscopy. Two TIRM microscopes are shown, one of which is used as an attachment to a commercial Nomarski microscope and the second of which is used in laser damage measurements. This surface inspection technique had been used to study surface polishing and cleaning methods, laser damage nucleation sites, ion milling of optical surfaces, and thin film inclusions. A biological application for liquid medium studies is suggested. A description of the electric fields present at and near the air sample interface is given.

© 1981 Optical Society of America

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References

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  1. This configuration has been used by Parks's group.2 However, they have primarily monitored the transmitted beam intensity for changes induced by a disrupted surface caused by laser-induced damage. Their observation of the externally scattered light appears to have been fairly casual.
  2. N. Alyassini, J. H. Parks, in Laser Induced Damage in Optical Materials: 1975, (NBS Special Publication, 435, A. J. Glass, A. H. Guenther, Eds. (U.S. GPO, Washington D.C., 1975), p. 284.
  3. P. A. Temple, Proc. Soc. Photo-Opt. Instrum. Eng. 190, 44 (1979).
  4. P. A. Temple, in Laser Induced Damage in Optical Materials: 1979, NBS Special Publication 568, H. E. Bennett, A. J. Glass, A. H. Guenther, B. E. Newnam, Eds. (U.S. GPO, Washington D.C., 1980), p. 333.
  5. P. A. Temple, D. Milam, W. H. Lowdermilk, Ref. 4 p. 229.
  6. F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1950), p. 564.
  7. O. Wiener, Ann. Phys. 40, 203 (1890).
  8. F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1950), p. 578.
  9. C. L. Andrews, Optics of the Electromagnetic Spectrum (Prentice-Hall, Englewood Cliffs, N.J., 1960), p. 417.
  10. The author would like to thank R. A. Ferrante (Naval Weapons Center) for suggesting the use of matching oil to allow one to distinguish between surface irregularities and other types of scattering sites.
  11. J. M. Elson, Naval Weapons Center; private communication.

1979

P. A. Temple, Proc. Soc. Photo-Opt. Instrum. Eng. 190, 44 (1979).

1890

O. Wiener, Ann. Phys. 40, 203 (1890).

Alyassini, N.

N. Alyassini, J. H. Parks, in Laser Induced Damage in Optical Materials: 1975, (NBS Special Publication, 435, A. J. Glass, A. H. Guenther, Eds. (U.S. GPO, Washington D.C., 1975), p. 284.

Andrews, C. L.

C. L. Andrews, Optics of the Electromagnetic Spectrum (Prentice-Hall, Englewood Cliffs, N.J., 1960), p. 417.

Elson, J. M.

J. M. Elson, Naval Weapons Center; private communication.

Jenkins, F. A.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1950), p. 578.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1950), p. 564.

Lowdermilk, W. H.

P. A. Temple, D. Milam, W. H. Lowdermilk, Ref. 4 p. 229.

Milam, D.

P. A. Temple, D. Milam, W. H. Lowdermilk, Ref. 4 p. 229.

Parks, J. H.

N. Alyassini, J. H. Parks, in Laser Induced Damage in Optical Materials: 1975, (NBS Special Publication, 435, A. J. Glass, A. H. Guenther, Eds. (U.S. GPO, Washington D.C., 1975), p. 284.

Temple, P. A.

P. A. Temple, Proc. Soc. Photo-Opt. Instrum. Eng. 190, 44 (1979).

P. A. Temple, in Laser Induced Damage in Optical Materials: 1979, NBS Special Publication 568, H. E. Bennett, A. J. Glass, A. H. Guenther, B. E. Newnam, Eds. (U.S. GPO, Washington D.C., 1980), p. 333.

P. A. Temple, D. Milam, W. H. Lowdermilk, Ref. 4 p. 229.

White, H. E.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1950), p. 564.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1950), p. 578.

Wiener, O.

O. Wiener, Ann. Phys. 40, 203 (1890).

Ann. Phys.

O. Wiener, Ann. Phys. 40, 203 (1890).

Proc. Soc. Photo-Opt. Instrum. Eng.

P. A. Temple, Proc. Soc. Photo-Opt. Instrum. Eng. 190, 44 (1979).

Other

P. A. Temple, in Laser Induced Damage in Optical Materials: 1979, NBS Special Publication 568, H. E. Bennett, A. J. Glass, A. H. Guenther, B. E. Newnam, Eds. (U.S. GPO, Washington D.C., 1980), p. 333.

P. A. Temple, D. Milam, W. H. Lowdermilk, Ref. 4 p. 229.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1950), p. 564.

F. A. Jenkins, H. E. White, Fundamentals of Optics (McGraw-Hill, New York, 1950), p. 578.

C. L. Andrews, Optics of the Electromagnetic Spectrum (Prentice-Hall, Englewood Cliffs, N.J., 1960), p. 417.

The author would like to thank R. A. Ferrante (Naval Weapons Center) for suggesting the use of matching oil to allow one to distinguish between surface irregularities and other types of scattering sites.

J. M. Elson, Naval Weapons Center; private communication.

This configuration has been used by Parks's group.2 However, they have primarily monitored the transmitted beam intensity for changes induced by a disrupted surface caused by laser-induced damage. Their observation of the externally scattered light appears to have been fairly casual.

N. Alyassini, J. H. Parks, in Laser Induced Damage in Optical Materials: 1975, (NBS Special Publication, 435, A. J. Glass, A. H. Guenther, Eds. (U.S. GPO, Washington D.C., 1975), p. 284.

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Figures (14)

Fig. 1
Fig. 1

Physical setup used to illuminate transparent surfaces for microscopic examination. Not shown is a microscope slide manipulator used to grasp the sample and to slide it about on the oil-covered prism face. The coordinate system shown is used in the discussions in the text. The Babinet-Soleil plate is used to change the plane of polarization of the illuminating laser beam.

Fig. 2
Fig. 2

Fixture designed to implement the setup shown in Fig. 1. This fixture is shown mounted on the sample stage of a Nomarski microscope. The microscope slide manipulator, not shown in Fig. 1, can be seen grasping a 1.5-in. diam, 0.25-in. thick sample.

Fig. 3
Fig. 3

The TIRM in situ laser damage microscope as configured for TIRM viewing and photography. In this figure can be seen the 3-mW He–Ne laser, the microscope viewing optics, the sample holding stage, and the Polaroid camera. The base had adjustable feet for positioning the instrument in the high intensity laser beam.

Fig. 4
Fig. 4

Sample configuration for the in situ TIRM microscope shown in Fig. 3. The two coupling prisms are in optical contact with the sample through a small drop of coupling fluid. Frequently, the second (exit) prism is not used. The coupling prisms are held fixed to the microscope body, and the sample is moved by a manipulator which is similar to that in Fig. 2.

Fig. 5
Fig. 5

Three photos of the same region of a laser-damaged, conventionally polished piece of fused silica. The view on the left is a Nomarski photo showing several pits caused by a 15-J/cm2,1.06-μm wavelength, 1-nsec pulse length exposure. Photo on the right is a TIRM view. Since the part is mechanically polished, it has many features visible in this view which are not related to the damage shown in the left photo. Center view shows the Nomarski and TIRM illuminations simultaneously. It can be seen here that few of the TIRM features are actually identified with damage sites. Most of these features are mechanical damage due to the polishing process.

Fig. 6
Fig. 6

Standing wave pattern at the surface of fused silica when illuminated from within by an s-polarized beam. The ordinate is the ratio of the time average of the square of the resultant electric field to the time average of the square of the electric field of the incident beam. The angle of incidence is 43°, while the critical angle is 42.86°.

Fig. 7
Fig. 7

The value E 2 / E 0 2 of for internal and external illumination using s-polarized light for various angles of incidence. As in Fig. 6, the maximum value for E 2 / E 0 2 is 4 and occurs at the critical angle for internal illumination.

Fig. 8
Fig. 8

(a) The tangential component standing wave pattern setup at the surface of fused silica when illuminated from within by a p-polarized beam. As in Fig. 6, E 2 / E 0 2 is shown as a function of depth. (b) The normal component standing wave pattern setup at the surface of fused silica when illuminated from within by a p-polarized beam. As in Fig. 6, E 2 / E 0 2 is shown as a function of depth. Notice the very intense evanescent component in this case.

Fig. 9
Fig. 9

The surface of a superpolished fused silica substrate under s- and p-polarized illumination showing the increased visibility of surface features illuminated by s-polarized light. The surface has an rms roughness of 3.5 Å, as measured by Talystep profilometry. The surface has been illuminated at just beyond the critical angle.

Fig. 10
Fig. 10

The value of E 2 / E 0 2 for internal and external illumination as a function of illumination angle of incidence for p-polarization. The value of E 2 / E 0 2 for internal illumination is as shown for either the air or glass side of the interface. The value E 2 / E 0 2 of shown is for the glass side of the interface, and the value of E 2 / E 0 2 for the air side is n glass 4 times the value of E 2 / E 0 2 on the glass side.

Fig. 11
Fig. 11

The nodal spacing just below the surface for s- and p-polarized illumination as a function of angle of incidence. The positions of the first and second nodes and first antinode are shown for s-polarized illumination. The positions of the first node and first and second antinodes are shown for the tangential component for p-polarized illumination.

Fig. 12
Fig. 12

The TIR-illuminated surface of a highly polished BK-7 sample with matching oil on a portion of the surface. There are one bright and several dim features which were not removed by the matching oil. Most of the scattering features were, however, removed by the oil, indicating that their origin is surface roughness.

Fig. 13
Fig. 13

A fused silica surface half of which has been coated with a 0.35-μm thick SiO2 film. The site density seen here, ∼1000/mm2, is abnormally large for a film of SiO2 but is shown to demonstrate the sensitivity of TIR-illuminated microscopy to internal film defects.

Fig. 14
Fig. 14

The value of E 2 / E 0 2 as a function of depth for s- and p-polarized internal illumination for a film of index 1.3 and 0.22 μm thick on a substrate of index 1.47. Only the tangential component is shown for p-polarization.

Equations (7)

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δ = 4 π nl λ 0 cos ϕ + Δ ref ( rad ) .
tan Δ ref 2 = n 2 sin 2 ϕ 1 n cos ϕ ( s polarization ) ,
tan Δ ref 2 = n n 2 sin 2 ϕ 1 cos ϕ ( p polarization ) ,
Γ = λ 0 2 n cos ϕ c .
d = Γ 2 + m Γ .
d = Γ 2 + ( m + 1 ) Γ ,
d = λ 0 λ 2 n cos ϕ c ( λ 0 λ ) .

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