Method for putting a cooled infrared detector into operation
In an infrared detector provided with a photodiode, when the temperature of the photodiode is lowered to its operating temperature, the photodiode is forward biased. During forward biasing of the photodiode, injection of a majority carrier current takes place through the photodiode. The majority carriers mask a part of the defects of the photodiode. The acquisition phase is then performed by reverse biasing the photodiode.
1. A method for putting an infrared detector into operation comprising:
providing the infrared photodetector having a photodiode and a readout circuit,
lowering the temperature of the photodiode from a first temperature to a working temperature lower than the first temperature,
applying a forward bias to the terminals of the photodiode during lowering the temperature of the photodiode from the first temperature to a second temperature higher or equal to the working temperature, and
applying a reverse bias condition to the terminals of the photodiode after the photodiode has reached the working temperature so as to cause the photodiode to transform an optical signal into an electric current while maintaining the temperature of the photodiode at the working temperature.
2. The method according to claim 1 , further comprising:
turning off a bias transistor that is connected in series with the photodiode of the infrared detector so as to place the bias transistor in an off state, and
switching an additional transistor having a first terminal connected to: (1) a
common terminal of the bias transistor, (2) a common terminal of the photodiode, and (3) a grounded second terminal so s to place the additional transistor in an on state.
3. The method according to claim 1 , further comprising:
an acquisition step for collecting an electrical current at a frequency of more than 100 Hz if the photodiode is reverse biased and is at the working temperature.
4. The method according to claim 3 , wherein the readout circuit includes a capacitive charge configured for storing the electric on provided by the photodiode,
the acquisition step including collecting a signal in the capacitive charge at a frequency of more than 100 Hz.
5. The method according to claim 1 , further comprising:
applying a forward bias to the terminals of the photodiode when the temperature is below −73° C. during the step of lowering the temperature of the photodiode from the first temperature to the working temperature.
6. The method according to claim 1 , further comprising:
applying a forward bias to the terminals of the photodiode between −73° C. and −225° C. during lowering the temperature from the first temperature to the working temperature.
7. A method for putting an infrared detector into operation comprising:
providing the infrared photodetector comprising a photodiode,
lowering continuously the temperature of the photodiode from a first temperature to a working temperature lower than the first temperature,
applying a forward bias to the terminals of the photodiode during lowering of the temperature from the first temperature down to a second temperature, the second temperature being lower than the first temperature and greater or equal to the working temperature,
applying a reverse bias to the terminals of the photodiode at the working temperature.
8. The method according to claim 7 , wherein the detector including a capacitive charge coupled to the photodiode,
the method further comprising:
storing a current coming from the photodiode into the capacitive charge so as to form a first data and analyzing the data by a read circuit coupled to the capacitive charge at the working temperature.
9. The method according to claim 8 , wherein the read circuit includes a reset circuit configured to reset charges carriers stocked in the capacitive charge,
the method further comprising:
performing the analysis of the data at a frequency of more than 100 Hz.