Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1978-06-19
1981-09-29
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
357 19, 455612, 455613, G01J 132
Patent
active
042925126
ABSTRACT:
The tracking problems of prior art optical monitoring (e.g., feedback stabilization) schemes are substantially alleviated by positioning a photodiode (PD 130) directly in the light path of the optical source (100) to be stabilized. The active (light-absorbing) layer (104) of the PD samples (absorbs) only a small portion of the light beam (140) emanating from the source and converts that portion to a photocurrent used in a feedback loop (120, 101) to control the excitation supplied to the source. The remaining, major portion (140') of the beam is transmitted unabsorbed through the PD active layer to utilization means (e.g., through an optical fiber 108 to a remote receiver). Advantageously, in one embodiment the PD is a double heterostructure (DH) in which the photocurrent is linearly related to the beam intensity. The use of discrete or integrated lens means (110, 110', 164, 166) to enhance coupling from the source to PD is described. In addition, tandem DH-PDs (150, 152) are also described which perform both detection, for demodulating encoded information at one optical frequency, and sampling, for feedback stabilization at another optical frequency.
REFERENCES:
patent: 4181901 (1980-01-01), Heyke
Merz et al., "J. Applied Physics," Aug. 1977, pp. 3580-3587.
"Laser Focus, " May 1978, p. 109.
Miller Richard C.
Schwartz Bertram
Bell Telephone Laboratories Incorporated
Hostetter Darwin R.
Nelms David C.
Urbano Michael J.
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