Photodetectors

Quantum efficiency

The quantum efficiency is defined as fraction of incident photons which are absorbed by photoconductor and generated electrons which are collected at the detector terminal. Practical formula for quantum efficiency can be derived from responsivity on a given wavelength: $R = \frac{e n_{e} }{ n_{ph} \hbar c/\lambda}$ Thus $\eta =\frac{n_{e}}{n_{ph}} = R/\lambda \frac{\hbar c}{ e} \approx 1240 \frac{R}{\lambda}$, where responsivity is given in Amperes per Watt (A/W), while wavelength is in nanometers (nm).

Detectors by wavelenght

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The different detectors are used depending on a wavelength of interest

Slow photodetectors

Characteristics:

Photodetector, #	Estimated Bandwidth (kHz)	Responsivity (mV/µW)	Saturation Power (µW)
1	23	1.97	N/A
2	23	445	34.9
3	23	460.8	31.9
4	23	8.96	N/A
5	23	11.79	N/A
6	58	1.44	N/A

Spectrum of Photodector No.1
Electronic Noise vs. Noise + Signal
(Beam Intensity 2.018 mW)

Spectrum of Photodector No.2
Electronic Noise vs. Noise + Signal
(Beam Intensity 22.33 µW)

Spectrum of Photodector No.3
Electronic Noise vs. Noise + Signal
(Beam Intensity 22.33 µW)

Spectrum of Photodector No.4
Electronic Noise vs. Noise + Signal
(Beam Intensity 0.21 mW)

Spectrum of Photodector No.5
Electronic Noise vs. Noise + Signal
(Beam Intensity 1.2 mW)

Spectrum of Photodector No.6
Electronic Noise vs. Noise + Signal
(Beam Intensity 1.2 mW)