Electroluminescent and radiant power spectra

[chrisewolf]

Hello everyone!

I am having a bit of a problem understanding a paper. Usually the authors use the electroluminescent spectrum to describe an emitter, but in this paper the radiant power is constantly cited.

What is the relation of these two?

Usually the EL spectrum is a.u. vs wavelength and radiant power is (in this paper!) W/(sr m^2) (usually called radiance).

Can these two quantities be converted (as the time information is not known)?

best regards,
Chris

[swansont]

No. They are not directly related.

[chrisewolf]

Thank you for your swift reply!

 

I wonder if you could tell me in short how the method of measurements differ? Both are (presumably) measured using a photodetector (Si-diode etc), right?

 

Thank you in advance!

[swansont]

For the spectrum you'd use something to split up the wavelength, like reflecting off of a grating. Then you could scan the detector position and measure what wavelengths were present. Si works if the wavelengths are shorter than ~1.1 microns. The detector need not be absolutely calibrated (and isn't if the output is in arbitrary units, a.u., though the wavelength sensitivity should have been taken into account)

 

For the radiance, you need a calibrated detector, and have to know the solid angle of detection and area of the source. You'd probably use a bolometer for this.

 

It's possible you could combine the two measurements with the proper setup, (e.g. use a lens to collect the light in a solid angle and then send it through the spectrometer) but that's not indicated in this case and seems (from my experience) to be much harder to do than the two individual measurements.

[chrisewolf]

Thank you very much for your explanation! Radio/Photometry is one of most confusing topics I have ever worked on, especially when authors are mixing up the quantities, symbols and units!