Abstract

A sensitive and versatile spectrophotometer for differential or absolute reflectance and transmittance measurements is described. Special sample configurations are not required, and the sample may be subjected to almost any type of external perturbation. A transparent refracting chopper is used to obtain separate sample and reference beams. A synchronous electronic circuit is used to measure the reference and sample signals while suppressing the intervening switching transients. The fractional absolute error is less than ±10−2. The peak-to-peak instrument noise is approximately 2 × 10−5 of the reference signal. Thus, changes in reflectance or transmittance as small as a few parts in 105 can be seen. In many cases this approaches the shot noise limit and is comparable to the sensitivity obtainable with modulation techniques. Examples of results for the reflectance of InP near 3.2 eV and GaAs near 1.8 eV are given.

© 1970 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. D. Beaglehole, Appl. Opt. 7, 2218 (1968).
    [CrossRef] [PubMed]
  2. U. Gerhardt, G. W. Rubloff, Appl. Opt. 8, 305 (1969).
    [CrossRef] [PubMed]
  3. Reference 2 claims a sensitivity of ±2 × 10−5. Reference 1 claims a sensitivity of better than 10−4. A similar apparatus for transmission studies discussed by D. R. Nicol, Rev. Sci. Instrum. 40, 1300 (1969), has a sensitivity of approximately 5 × 10−3.
    [CrossRef]
  4. Made by Laboratory Optical Co., Plainfield, New Jersey.
  5. S. O. Rice, Bell Telephone Laboratories, Murray Hill, N. J. 07974, personal communication; and unpublished application notes obtained from Princeton Applied Research Corp., Princeton, New Jersey.
  6. K. L. Shaklee, J. E. Rowe, Appl. Opt. 9, 627 (1970).
    [CrossRef] [PubMed]

1970 (1)

1969 (2)

U. Gerhardt, G. W. Rubloff, Appl. Opt. 8, 305 (1969).
[CrossRef] [PubMed]

Reference 2 claims a sensitivity of ±2 × 10−5. Reference 1 claims a sensitivity of better than 10−4. A similar apparatus for transmission studies discussed by D. R. Nicol, Rev. Sci. Instrum. 40, 1300 (1969), has a sensitivity of approximately 5 × 10−3.
[CrossRef]

1968 (1)

Beaglehole, D.

Gerhardt, U.

Nicol, D. R.

Reference 2 claims a sensitivity of ±2 × 10−5. Reference 1 claims a sensitivity of better than 10−4. A similar apparatus for transmission studies discussed by D. R. Nicol, Rev. Sci. Instrum. 40, 1300 (1969), has a sensitivity of approximately 5 × 10−3.
[CrossRef]

Rice, S. O.

S. O. Rice, Bell Telephone Laboratories, Murray Hill, N. J. 07974, personal communication; and unpublished application notes obtained from Princeton Applied Research Corp., Princeton, New Jersey.

Rowe, J. E.

Rubloff, G. W.

Shaklee, K. L.

Appl. Opt. (3)

Rev. Sci. Instrum. (1)

Reference 2 claims a sensitivity of ±2 × 10−5. Reference 1 claims a sensitivity of better than 10−4. A similar apparatus for transmission studies discussed by D. R. Nicol, Rev. Sci. Instrum. 40, 1300 (1969), has a sensitivity of approximately 5 × 10−3.
[CrossRef]

Other (2)

Made by Laboratory Optical Co., Plainfield, New Jersey.

S. O. Rice, Bell Telephone Laboratories, Murray Hill, N. J. 07974, personal communication; and unpublished application notes obtained from Princeton Applied Research Corp., Princeton, New Jersey.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (5)

Fig. 1
Fig. 1

Schematic representation of optical arrangement. Transparent chopper is shown in insert.

Fig. 2
Fig. 2

Schematic representation of the electronics.

Fig. 3
Fig. 3

Lower trace: signal at load resistor RL as a function of time. Middle and upper traces: voltage on sample and reference gates, respectively.

Fig. 4
Fig. 4

(a) Reflectance of InP at room temperature in the E1 and E1 + Δ1 region; (b) (dR/dE)/R obtained from reflectance; (c) wavelength modulation data for InP from Ref. 6.

Fig. 5
Fig. 5

Reflectance of GaAs at 90 K in the E0 + Δ0 region.

Equations (4)

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

P N = w / 4 R L C S .
w = 2 e V ¯ G ,
V N p p = 5 ( 2 P N R L ) 1 2 = 5 ( e V ¯ G / C S ) 1 2 .
( 1 / R m ) ( d R m / d E ) = ( 1 / R T ) ( d R T / d E ) .

Metrics