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Laser Power Calculations:

Using the photodetector's Responsivity at a given wavelength and Ohm's Law; V = IR, the output of EOT's photodetectors can be used to calculate the power of the laser incident on the active area of the detector:

For example, if an ET-2030 is producing an output of 20mV, the laser wavelength is 632.8nm and the detector is terminated into 50Ω, the incident power can be derived as follows:

I = 0.02V/50Ω, or I = 0.0004A

From the responsivity curve contained in the silicon photodetector data sheet, the responsitivity of the ET-2030 @ 632.8nm is 0.4A/W. Therefore,

0.0004A ÷ 0.4A/W = 1mW of incident power

Note: This is the amount of power incident on the detector, not necessarily the actual power of the beam as not all of the beam may be incident on the detector.