Abstract

Use of an optical local oscillator with a photoconductor can modify its conductance sufficiently to have a considerable effect on both the effective responsivity of the detector and its interaction with the signal processing circuitry. These effects are analyzed and formulations for the signal-to-noise ratio (SNR) are derived for both constant voltage bias and constant current bias. It was found that the SNR peaks at a finite optimum local oscillator power for the voltage bias case. For the current bias case, there is a saturationlike effect rather than a true maximum when operating the photoconductor in the linear region and a true maximum when operating in the quadratic region.

© 1988 Optical Society of America

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References

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  1. M. C. Teich, R. J. Keyes, R. H. Kingston, “Optimum Heterodyne Detection at 10.6 μm in Photoconductive Ge:Cu,” Appl. Phys. Lett. 9, 357 (15 Nov. 1966).
  2. R. H. Kingston, Detection of Optical and Infrared Radiation (Springer-Verlag, New York, 1978).
  3. R. J. Keyes, Optical and Infrared Detectors (Springer-Verlag, New York, 1977).
  4. F. R. Arams, E. W. Sard, B. J. Peyton, F. P. Pace, “Infrared 10.6-Micron Heterodyne Detection with Gigahertz IF Capability,” IEEE J. Quantum Electron. QE-3, 484 (1967).
    [CrossRef]
  5. N. A. Penin, N. Sh. Khaykin, B. V. Yurist, “Investigation of the Noise Factor of an Optical Heterodyne Receiver with an Extrinsic Photoresistor,” Radiotekh. Elektron. [Radio Eng. Electron. Phys. USSR 792 (May1972)].

1972 (1)

N. A. Penin, N. Sh. Khaykin, B. V. Yurist, “Investigation of the Noise Factor of an Optical Heterodyne Receiver with an Extrinsic Photoresistor,” Radiotekh. Elektron. [Radio Eng. Electron. Phys. USSR 792 (May1972)].

1967 (1)

F. R. Arams, E. W. Sard, B. J. Peyton, F. P. Pace, “Infrared 10.6-Micron Heterodyne Detection with Gigahertz IF Capability,” IEEE J. Quantum Electron. QE-3, 484 (1967).
[CrossRef]

Arams, F. R.

F. R. Arams, E. W. Sard, B. J. Peyton, F. P. Pace, “Infrared 10.6-Micron Heterodyne Detection with Gigahertz IF Capability,” IEEE J. Quantum Electron. QE-3, 484 (1967).
[CrossRef]

Keyes, R. J.

M. C. Teich, R. J. Keyes, R. H. Kingston, “Optimum Heterodyne Detection at 10.6 μm in Photoconductive Ge:Cu,” Appl. Phys. Lett. 9, 357 (15 Nov. 1966).

R. J. Keyes, Optical and Infrared Detectors (Springer-Verlag, New York, 1977).

Khaykin, N. Sh.

N. A. Penin, N. Sh. Khaykin, B. V. Yurist, “Investigation of the Noise Factor of an Optical Heterodyne Receiver with an Extrinsic Photoresistor,” Radiotekh. Elektron. [Radio Eng. Electron. Phys. USSR 792 (May1972)].

Kingston, R. H.

M. C. Teich, R. J. Keyes, R. H. Kingston, “Optimum Heterodyne Detection at 10.6 μm in Photoconductive Ge:Cu,” Appl. Phys. Lett. 9, 357 (15 Nov. 1966).

R. H. Kingston, Detection of Optical and Infrared Radiation (Springer-Verlag, New York, 1978).

Pace, F. P.

F. R. Arams, E. W. Sard, B. J. Peyton, F. P. Pace, “Infrared 10.6-Micron Heterodyne Detection with Gigahertz IF Capability,” IEEE J. Quantum Electron. QE-3, 484 (1967).
[CrossRef]

Penin, N. A.

N. A. Penin, N. Sh. Khaykin, B. V. Yurist, “Investigation of the Noise Factor of an Optical Heterodyne Receiver with an Extrinsic Photoresistor,” Radiotekh. Elektron. [Radio Eng. Electron. Phys. USSR 792 (May1972)].

Peyton, B. J.

F. R. Arams, E. W. Sard, B. J. Peyton, F. P. Pace, “Infrared 10.6-Micron Heterodyne Detection with Gigahertz IF Capability,” IEEE J. Quantum Electron. QE-3, 484 (1967).
[CrossRef]

Sard, E. W.

F. R. Arams, E. W. Sard, B. J. Peyton, F. P. Pace, “Infrared 10.6-Micron Heterodyne Detection with Gigahertz IF Capability,” IEEE J. Quantum Electron. QE-3, 484 (1967).
[CrossRef]

Teich, M. C.

M. C. Teich, R. J. Keyes, R. H. Kingston, “Optimum Heterodyne Detection at 10.6 μm in Photoconductive Ge:Cu,” Appl. Phys. Lett. 9, 357 (15 Nov. 1966).

Yurist, B. V.

N. A. Penin, N. Sh. Khaykin, B. V. Yurist, “Investigation of the Noise Factor of an Optical Heterodyne Receiver with an Extrinsic Photoresistor,” Radiotekh. Elektron. [Radio Eng. Electron. Phys. USSR 792 (May1972)].

Appl. Phys. Lett. (1)

M. C. Teich, R. J. Keyes, R. H. Kingston, “Optimum Heterodyne Detection at 10.6 μm in Photoconductive Ge:Cu,” Appl. Phys. Lett. 9, 357 (15 Nov. 1966).

IEEE J. Quantum Electron. (1)

F. R. Arams, E. W. Sard, B. J. Peyton, F. P. Pace, “Infrared 10.6-Micron Heterodyne Detection with Gigahertz IF Capability,” IEEE J. Quantum Electron. QE-3, 484 (1967).
[CrossRef]

Radiotekh. Elektron. (1)

N. A. Penin, N. Sh. Khaykin, B. V. Yurist, “Investigation of the Noise Factor of an Optical Heterodyne Receiver with an Extrinsic Photoresistor,” Radiotekh. Elektron. [Radio Eng. Electron. Phys. USSR 792 (May1972)].

Other (2)

R. H. Kingston, Detection of Optical and Infrared Radiation (Springer-Verlag, New York, 1978).

R. J. Keyes, Optical and Infrared Detectors (Springer-Verlag, New York, 1977).

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Figures (12)

Fig. 1
Fig. 1

Constant voltage bias circuit.

Fig. 2
Fig. 2

Small-signal equivalent circuit.

Fig. 3
Fig. 3

Normalized heterodyne signal current, voltage bias case.

Fig. 4
Fig. 4

Normalized SNR, voltage bias case, g–r noise dominant.

Fig. 5
Fig. 5

Optimum local oscillator level for maximum SNR, voltage bias case, g–r noise dominant. G′/G is in units of mW−1.

Fig. 6
Fig. 6

Constant current bias circuit.

Fig. 7
Fig. 7

Normalized heterodyne signal voltage, current bias case.

Fig. 8
Fig. 8

Normalized SNR, current bias case, g–r noise dominant.

Fig. 9
Fig. 9

Normalized noise voltage, current bias case, g–r noise dominiant.

Fig. 10
Fig. 10

Calculated SNR, g–r noise dominant, voltage bias case, HgCdTe detector. In this configuration, coupling into a relatively low input impedance (current mode) amplifier (GLG) is desirable.

Fig. 11
Fig. 11

Calculated SNR, g–r noise dominant, current bias case, HgCdTe detector. Coupling into an amplifier with relatively high input impedance (GLG) is desirable in this configuration.

Fig. 12
Fig. 12

Conductance as a function of local oscillator power, HgCdTe detector.

Equations (47)

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G detector = G + G P in ,
V = I B G + G P in .
ρ v = V P in | P i n = 0 ,
ρ v = I B G G 2 ,
G = G 2 ρ v I B .
i = V B G P in = η e P in g h ν ,
g = V B G h ν η e ,
I = V B G tot ( ω , P in ) = I dc + i Het + i n + higher order terms ,
P in = P dc + P Het + P nLO = P LO + 2 P LO P S + α ( ω ) P LO ,
G tot = G + G P LO for ω = 0 ,
G tot = G L ( G + G P in ) ( G + G L + G P in ) for ω = ω Het ,
I dc + i Het = V B ( G + G P LO ) + 2 V B G P LO P S G L 2 ( G + G L + G P LO ) 2 ,
i Het = V B [ G tot ( ω , P in ) P in ] P in = P LO P in P Het P Het .
i s = 2 V B G P LO P S G L G + G L + G P LO .
normalized i Het = i Het 2 V B G P S G = y 2 x 1 / 2 ( 1 + y + x ) 2 ,
y = G L G ,
x = G P L O G .
P LO = G + G L 3 G .
g - r noise variance = 4 I dc e B g = 4 B h ν η V B 2 G ( G + G P LO ) ,
i n LO = V B [ G tot ( ω , P in ) P in ] P in = P LO · P in P n LO P n LO = V B α ( ω ) G P LO G L 2 ( G + G L + G P LO ) 2 .
i S n LO = V B α ( ω ) G P LO G L ( G + G L + G P LO ) ,
i n 2 = [ B V B 2 G 2 P LO 2 G L 2 α ( ω ) 2 ( G + G L + G P LO ) 2 + 4 B V B 2 ( G + G P LO ) h ν G η + 4 B k T D ( G P LO ) + 4 B k T e G L ] . G L 2 ( G + G L + G P LO ) 2 ,
SNR = V B 2 ( G ) 2 P L O P S B [ V B 2 G 2 P LO 2 G L 2 α ( ω ) 2 4 + ( G + G P LO ) ( V B 2 h ν G η + k T e G L ) ] · G L 2 ( G + G L + G P LO ) 2 .
G ( ω ) = G ( ω = 0 ) ( 1 + ω 2 τ 2 ) - 1 / 2 ,
SNR = P S η B h ν · G P LO G + G P LO · G L 2 ( G + G L + G P LO ) 2 .
normalized SNR = SNR · B h ν P s η = y 2 x ( 1 + x ) ( 1 + y + x ) 2 ,
P LO = G 4 G [ 9 + ( 8 G L / G ) - 1 ] .
V = I B G tot ( ω , P in ) = V dc + v Het + v n + higher order terms .
V dc + v Het = I B G + G P LO + 2 I B G P LO P S ( G + G L + G P LO ) 2 .
i s = 2 I B G P LO P S ( G + G L + G P LO ) ,
normalized v Het = v Het 2 I B G P S / G 3 = x 1 / 2 ( 1 + y + x ) 2 ,
i S n LO = I B G α ( ω ) P LO ( G + G L + G P LO ) .
v n 2 = [ B I B 2 G 2 α 2 ( ω ) P LO 2 ( G + G L + G P LO ) 2 + 4 I B 2 B G h ν η ( G + G P LO ) + 4 B k T D ( G + G P LO ) + 4 B k T e G L ] 1 ( G + G L + G P LO ) 2 .
SNR = I B 2 ( G ) 2 P LO P S B [ I B 2 G 2 P LO 2 α ( ω ) 2 4 ( G + G L + G P LO ) 2 + I B 2 h ν G η ( G + G P LO ) + k T D ( G + G P LO ) + k T e G L ] · 1 ( G + G L + G P LO ) 2 .
SNR = P S η B h ν · G P LO G + G P LO · ( G + G P LO G + G L + G P LO ) 2 .
normalized SNR = SNR · B h ν P S η = x ( 1 + x ) ( 1 + y + x ) 2 .
normalized v n 2 = η G 3 4 I B 2 B G h ν v n 2 = 1 ( 1 + x ) ( 1 + y + x ) 2 ,
G D = G + G P in + G P in 2 .
G + G P LO G + G P LO + G P LO 2 ;
G G + 2 G P LO .
voltage bias case i Het = 2 V B ( G + 2 G P LO ) P LO P S · ( G L G + G L + G P LO + G P LO 2 ) 2 ,
volatage bias case SNR = V B 2 ( G + 2 G P LO ) 2 P LO P S B [ V B 2 ( G + 2 G P LO ) 2 G L 2 α ( ω ) 2 4 + ( G + G P LO + G P LO 2 ) ( V B 2 h ν G η + k T D ) + k T e G L ] · G L 2 G + G P LO + G P LO 2 ,
current bias case v Het = 2 I B ( G + 2 G P LO ) P LO P S ( G + G L + G P LO + G P LO 2 ) 2 .
current bias case SNR = I B 2 ( G + 2 G P LO ) 2 P LO P S B [ I B 2 G 2 P LO 2 α ( ω ) 2 4 ( G L + G + G P LO + 2 G P LO 2 ) 2 + I B 2 h ν ( G + 2 G P LO 2 ) η ( G + G P LO + 2 G P LO 2 ) 2 + k T D ( G + G P LO + G P LO 2 ) + k T e G L ] · 1 ( G L + G + G P LO + 2 G P LO 2 ) 2 .
voltage bias case , g - r noise dominant SNR = P S η B h ν · G P LO + 2 G P LO 2 G + G P LO + 2 G P LO 2 · ( G L G L + G + G P LO + 2 G P LO 2 ) 2 ,
current bias case , g - r noise dominant SNR = P S η B h ν · G P LO + 2 G P LO 2 G + G P LO + 2 G P LO 2 · ( G + G P L O + 2 G P L O 2 G L + G + G P LO + 2 G P LO 2 ) 2 .
G D = 0.0276 + 0.0175 P LO - 0.003 P LO 2 ,

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