Re: two rays of different wavelength will generate the same electric current ?

I have 2 different light rays which have different wavelengths (for
instance one is red and the other is green).

I'm sending these rays to 2 photodiodes.

Is the electric current generated by those photodiodes the same? Are
there any differences (power, intensity) ?

Photodiodes are made from semiconductors such as silicon, germanium,
and InGaAs (indium gallium arsenide). Each of these semiconductors has
a bandgap energy, Eg. Typically, a photodiode will work for any
wavelength (within reason...see below) where the corresponding photon
energy, given by E=hc/lambda, is greater than Eg. So, if two
wavelengths are not separated by much, the same photodiode will
generate the roughly same amount of current for hc/lambda > Eg. (h =
Planck's constant, c = speed of light, and lambda is the wavelength.)

If, however, the wavelengths are seperated by a significant amount such
as red (say lambda=650nm) and green (say lambda=514nm), then one will
see a difference for sure. But first, one must ask if the given
photodiode will even work for photon energies much larger than Eg?
Take for example silicon. A silicon detector will detect both of these
wavelengths, but germanium and InGaAs won't.

Next, one must consider the responsivity of the detector. Responsivity
measures how many amps of current will be generated per watt of
incident light. Moreover, responsivity is wavelength dependent.
Therefore, given equal incident powers of red and green light, a
silicon photodiode will generate different currents.

Regards

.