Measurement method for characterization of a photodetector

A measurement method for characterization of a photodetector, comprising the following steps:

• illuminating the photodetector with a variable electromagnetic radiation, the variable electromagnetic radiation having a temporally oscillating radiation intensity with a fixed period and amplitude,
• illuminating the photodetector with a first electromagnetic radiation having a temporally constant first radiation intensity, and measuring a first output signal at the photodetector,
• illuminating the photodetector with a second electromagnetic radiation having a temporally constant second radiation intensity different from the first radiation intensity and measuring a second output signal at the photodetector,
• determining a nonlinearity of the photodetector by comparing the measurements of the first and second output signals,
• wherein
• the photodetector is a photodiode connected in series with an ohmic resistor at which a photocurrent produces a measurable voltage drop,
• a bias voltage at the photodiode is kept constant by readjustment,
• the measurement of the first output signal and the second output signal at the photodetector is performed using a phase-sensitive rectifier which is fed with a reference signal of the same period and phase as the period and phase of the variable electromagnetic radiation, and
• the variable electromagnetic radiation has a temporal oscillation with a sinusoidal waveform and is provided by a light-emitting diode that is driven with a temporally oscillating voltage, and
• the temporally oscillating voltage is further used as the reference signal for the phase-sensitive rectifier.

A measurement method for characterization of a photodetector, comprising the following steps:

• illuminating the photodetector with a variable electromagnetic radiation, the variable electromagnetic radiation having a temporally oscillating radiation intensity with a fixed period and amplitude,
• illuminating the photodetector with a first electromagnetic radiation having a temporally constant first radiation intensity, and measuring a first output signal at the photodetector,
• illuminating the photodetector with a second electromagnetic radiation having a temporally constant second radiation intensity different from the first radiation intensity and measuring a second output signal at the photodetector,
• determining a nonlinearity of the photodetector by comparing the measurements of the first and second output signals,
• wherein
• the photodetector is a photodiode connected in series with an ohmic resistor at which a photocurrent produces a measurable voltage drop,
• a bias voltage at the photodiode is kept constant by readjustment,
• the measurement of the first output signal and the second output signal at the photodetector is performed using a phase-sensitive rectifier which is fed with a reference signal of the same period and phase as the period and phase of the variable electromagnetic radiation,
• wherein the nonlinearity of the photodetector is determined as a function of an electric current flowing through an illumination element while it provides the temporally constant second radiation intensity during measurement of the second output signal,
• the nonlinearity is determined by taking a difference between the second output signal and the first output signal and dividing this difference by the first output signal, and
• the method is self-referential in that an intensity of the illumination element is not externally calibrated.