Chapter 4 Operation; Theory Of Operation; Responsivity; Modes Of Operation - THORLABS DET01CFC User Manual

InGaAs Biased Detector Chapter 4: Operation

Chapter 4 Operation

4.1. Theory of Operation

A junction photodiode is an intrinsic device, which behaves similarly to an
ordinary signal diode, but it generates a photocurrent when light is absorbed in
the depleted region of the junction semiconductor. A photodiode is a fast, linear
device that exhibits high quantum efficiency based upon the application used in a
variety of different applications.
It is necessary to be able to determine correctly the level of the output current to
expect and the responsivity based upon the incident light. Depicted in Figure 1 is
a junction photodiode model with basic discrete components to help visualize the
main characteristics and gain a better understanding of the operation of Thorlabs'
photodiodes.
Figure 1 Photodiode Model

4.2. Responsivity

The definition of photodiode responsivity is the ratio of generated photocurrent
(I ) to the incident light power (P) at a given wavelength:
PD

4.3. Modes of Operation

The photodiode can operate in one of two modes: photoconductive (reverse bias)
or photovoltaic (zero-bias). Mode selection depends upon the applications speed
requirements and the amount of tolerable dark current (leakage current).
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