I have deposited ZnO nanowires upon glass substrates. The photoluminescence spectrum shows broad emission features in visible region (400 to 700nm). To my knowledge, the y-axis PL intensity is excitation source dependent and the (cps) value increases when the excitation source bandwidth increases.
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However, I was asked by a journal reviewer to calculate the PL intensity in terms of W/cm2. Is there any standard method to calculate the y-axis PL intensity (cps) in terms of W/cm2? If yes please help.
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Excitation source conditions are as follows:
Excitation wavelength: 325nm
Measurement range: 350 to 700 nm.
excitation bandwidth: 5nm,
emission bandwidth: 5nm,
sensitivity : medium
Source : Xe lamp.
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(A sampl PL graph is attached)
I don't think this is a good reviewer comment, unless your application uses the light produced this way for some reason. For example if you were making an LED, then it would be reasonable to make a calibrated measurement.
1st option: call the manufacturer of the instrument, they may be able to tell you some details, but basically this will still be a poor answer. Since most of the light is not likely collected by the instrument and assumptions still need to be made about the size of the sample, the size of the illuminated spot, how the light leaves the sample etc.
2nd option, which may not be possible would be to use a know light source calibrated light source, or sample that emits a calibrated amount of light.
3rd option, point out to the reviewer that you are interested in the relative intensity and that this is common practice.
Hope this helps, with out seeing the paper, I can't tell why the reviewer thought that W/cm2 was important. But in almost all cases I can think of it is probably not a good reason for photoluminescence measurements.
Wanting to know the power of the excitation is a common question, but wanting to know the PL intensity of the emission spectra, which is what the question was asking is not common at all.
Also the question Amiruddin posted did not use an argon ion laser. he was using a Xe lamp. Argon lasers do not operate at 325 nm. HeCad lasers have a 325 line and are sometimes used.
Be careful about how you measure the spot size, if you want to have accurate measures of laser power, it is not necessarily that simple to do properly.
In general making good radiometric measurements is more tricky than people assume.
Thanks for your kind reply, John Muthu and Subhrajit Mukherjee, There are few literature which calculates PL intensity in terms of W/cm2
For eg.,
Journal of Cluster Science 23, 649659 (2012).
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What I understood is there is little chance in calculating the PL intensity (W/cm2) when the samples were excited using LASER source. The above paper also explains the same ie., using LASER source. And obviously it is very tricky. Thanks once again for your help John Muthu and Subhrajit Mukherjee.
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