Abstract

A sensitivity of 0.03-mμ birefringence is achieved by the introduction of a plastic disk (~6-mμ birefringence) rotated at 30 Hz to modulate the birefringence at 60 Hz and a suitable detector. Two components are found in the detector signal: the one (120 Hz) that depends on the modulator birefringence is rejected; the other (60 Hz) which depends linearly on the compensator birefringence and changes phase at extinction is utilized. An A.E.I. BTH compact mercury arc (with interference filter for 546 mμ) operated on dc is the light source; a photomultiplier 1P21 is the detector. The signal is first fed into a parallel T notch filter which reduces the 120-Hz component five-hundred-fold and then into a three-stage narrow-band (5-Hz) active filter (utilizing three integrated-circuit operational amplifiers) that provides possible gain of 151 dB for the 60-Hz component. To obviate tedious manual setting of the compensator for the required traverse of the specimen, a 60-Hz servo motor is linked to the tangent screw of the analyzer and operated by a power amplifier for the active filter-output signal. Potentiometers on the specimen-translation screw and on the analyzer tangent screw permit the data to be plotted on an x-y For vitreous silica specimens 1 cm deep, 3 mm wide, irradiated with electrons of 1-mm range recorder. (0.6 MeV), the effect of a radiation-induced dilatation as small as 3 × 10−8 can be observed, equivalent to inserting an atomic sheet into a 1-cm long specimen. Alternatively, 1% dilatation of a surface layer 30 Å thick can be detected.

© 1971 Optical Society of America

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References

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  1. M. F. Merriam, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 125, 52 (1962).
    [CrossRef]
  2. S. Mascarenhas, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 134, A485 (1964).
    [CrossRef]
  3. S. Costa Ribeiro, Rev. Sci. Instrum. 38, 705 (1967).
    [CrossRef]
  4. J. Badoz, J. Phys. Radium 17, 143A (1956).
    [CrossRef]
  5. N. M. Bashara, A. B. Buckman, A. C. Hall, Eds., Recent Developments in Ellipsometry (North-Holland, Amsterdam, reprinted from Surface Science, Vol. 16, 1969).
  6. Reference 5, pp. 398–427.
  7. Reference 5, p. 419.

1967 (1)

S. Costa Ribeiro, Rev. Sci. Instrum. 38, 705 (1967).
[CrossRef]

1964 (1)

S. Mascarenhas, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 134, A485 (1964).
[CrossRef]

1962 (1)

M. F. Merriam, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 125, 52 (1962).
[CrossRef]

1956 (1)

J. Badoz, J. Phys. Radium 17, 143A (1956).
[CrossRef]

Badoz, J.

J. Badoz, J. Phys. Radium 17, 143A (1956).
[CrossRef]

Costa Ribeiro, S.

S. Costa Ribeiro, Rev. Sci. Instrum. 38, 705 (1967).
[CrossRef]

Mascarenhas, S.

S. Mascarenhas, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 134, A485 (1964).
[CrossRef]

Merriam, M. F.

M. F. Merriam, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 125, 52 (1962).
[CrossRef]

Smoluchowski, R.

S. Mascarenhas, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 134, A485 (1964).
[CrossRef]

M. F. Merriam, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 125, 52 (1962).
[CrossRef]

Wiegand, D. A.

S. Mascarenhas, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 134, A485 (1964).
[CrossRef]

M. F. Merriam, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 125, 52 (1962).
[CrossRef]

J. Phys. Radium (1)

J. Badoz, J. Phys. Radium 17, 143A (1956).
[CrossRef]

Phys. Rev. (2)

M. F. Merriam, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 125, 52 (1962).
[CrossRef]

S. Mascarenhas, D. A. Wiegand, R. Smoluchowski, Phys. Rev. 134, A485 (1964).
[CrossRef]

Rev. Sci. Instrum. (1)

S. Costa Ribeiro, Rev. Sci. Instrum. 38, 705 (1967).
[CrossRef]

Other (3)

N. M. Bashara, A. B. Buckman, A. C. Hall, Eds., Recent Developments in Ellipsometry (North-Holland, Amsterdam, reprinted from Surface Science, Vol. 16, 1969).

Reference 5, pp. 398–427.

Reference 5, p. 419.

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Figures (6)

Fig. 1
Fig. 1

Optical train of the polarimeter: P polarizer, M modulator, S specimen, Q λ/4 plate, A analyzer.

Fig. 2
Fig. 2

Poincaré sphere: S specimen axis, A linear polarization after passing the polarizer, λ/4 axis of the λ/4 plate, B elliptical polarization after passing the specimen, C linear polarization after passing the λ/4 plate. The bilobed figure at A results from the modulator whose axis rotates about the equatorial plane at a rate ωt.

Fig. 3
Fig. 3

Plan of the system: S-1, light source; L-1, condenser lens; F, filter; A-1, collimator aperture; L-2, collimator lens; P-1, polarizer; M-1, modulator; A-2, field aperture; A-3 slit; S-2, specimen; P-2, linear potentiometer transducer for specimen translation; Q, λ/4 plate; S-3, tangent screw; P-3 tangent screw ten-turn potentiometer; A-4, analyzer; L-3, objective lens; M-2, mirror; M-3, mirror; OC-1, ocular; OC-2, auxiliary ocular; D, photomultiplier and housing.

Fig. 4
Fig. 4

Servo photoelastimeter filter and amplifier circuits.

Fig. 5
Fig. 5

Tangent screw servo analyzer.

Fig. 6
Fig. 6

Examples of data sheets obtained from the photoelastimeter recorder for vitreous silica specimens subjected to ion bombardment on one face. The heavily accented lines were centimeter rulings. The analyzer azimuth is plotted vertically, the traverse horizontally (4-cm markings correspond to 1-mm traverse). The zero analyzer setting can be obtained from the portions of the tracing beyond the edges of the specimens. (a) The upper sheet is for the most sensitive setting currently employed, 0.05° rotation of the analyzer per centimeter marking. The horizontal set of dots at the top correspond to 0.5-mm movement of the specimen carriage; the vertical dots to 1/20 turn of the voltage divider serving the tangent screw potentiometer and equivalent to the same rotation of the tangent screw. (b) The lower sheet is for a less sensitive setting, 0.25° rotation of the analyzer per centimeter marking, for a specimen showing a greater effect. Lines showing the specimen edges have been ruled; and, also, a line has been ruled through the retardation curve to aid in obtaining its mean slope.

Equations (5)

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φ = A sin ω t .
I = g ( ξ + φ ) 2 ,
J 2 = k A 2 cos 2 ω t ,
if ξ + , J 1 = 2 k ξ A sin ω t , if ξ - , J 1 = - 2 k ξ A sin ω t ,
( A C ) = ( A B ) ,

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