Calibrating External Photodetectors

Calibrate the responsivity and dark current of an external photodetector (ePD) with calibration utilities provided by the Optoelectronic Component Test Software. The calibration utilities use a single SMU channel to calibrate the ePD.

Calibrating Responsivity

The responsivity of an ePD is the ratio of the ePD current to the incident optical power at a given wavelength. The responsivity reflects an ePD's sensitivity to light. NI recommends using ePD responsivity when analyzing light-current-voltage (LIV) curves.

To calibrate the responsivity of an ePD, place a light-emitting device in front of the ePD. Ensure that the wavelength of the light-emitting device is the same as the DUT wavelength and you are aware of how much optical power the light-emitting device generates and sends to the ePD. Then, run the Calibrate PD Responsivity Utility. The utility measures the ePD current and calculates the ePD responsivity with the measured ePD current and the optical power generated by the light-emitting device.

The Calibrate PD Responsivity Utility is located in the following directories:
  • LabVIEW: LabVIEW version\ProjectTemplates\Source\Optoelectronic\Examples\Calibrate PD Responsivity.vi
  • C#: C:\Users\Public\Documents\National Instruments\Optoelectronic Component Test Software\Examples\DotNET\CalibratePDResponsivity
Note To calibrate the responsivity of an ePD, you can also measure the wavelength of the DUT and then find the ePD responsivity at the measured wavelength in the ePD specifications provided by the ePD vendor.

Calibrating Dark Current

The dark current of an ePD is the leakage current generated when the ePD is reverse biased and no light is incident on the ePD. NI recommends subtracting ePD dark current from the measured ePD current when analyzing LIV curves.

Measure the dark current of an ePD with the Calibrate PD Dark Current Utility.

The Calibrate PD Dark Current Utility is located in the following directories:
  • LabVIEW: LabVIEW version\ProjectTemplates\Source\Optoelectronic\Examples\Calibrate PD Dark Current.vi
  • C#: C:\Users\Public\Documents\National Instruments\Optoelectronic Component Test Software\Examples\DotNET\CalibratePDDarkCurrent