Photoluminescence Spectroscopy- Two individual spots, different colors, but same emission spectra my apologies in advance if I'm not posting at the right site, but StackExchange-Physics is the closest one that relates to this question.
Method: Photoluminescence spectroscopy
Sample being studied: a mm-size crystal with rough surface, and unequal height
What's confusing me: On the same crystal, a spot that emits purple light and another spot that emits blue light have the same PL spectra. Why?
Here're my guesses and I was hoping someone could suggest other/a more concrete causes with reference.
Guess 1. [Premise: the purple spot has a much brighter PL intensity than the blue spot] The blue and the purple spots have different emission spectra, and the blue area has some faint purple emission that's unnoticeable by eye, but since the purple emission lot more intense than the blue emission, the spectrum for the blue spot is shadowed by that of the purple spot, so for each spot I see the same spectrum.
Guess 2. Blue and the purple spots are exactly the same so they should have the same spectrum, but since the crystal has an uneven surface some of the blue/purple light gets scattered, resulting in a different color than what's originally emitting.
Thanks!
 A: A few questions that might be useful for us


*

*How are you measuring the PL, many spectroscopy tools have difficulty resolving small areas, so what does your set-up or tool look like?

*How do you observe the spots?

*What do you use to induce the PL?

*Do you wear glasses (possibly with anti-glare filter)?

*For guess 2, is the surface roughness at some point maybe periodic, have you observed it under high magnification, possibly an electron microscope?

*Very importantly does the PL tool/set-up use any optical filter and what is the orientation of the crystal with regards to the spots?

*Also can you see the 2 spots under most angles or only if you hold the crystal under a specific angle?


I have an idea of what be happening maybe but I need most of those first.
If optical filters are involved I can exactly tell you what's going on, there are some other options but there are less likely.
Edit, if you don't have all the answers immediately start by answering some of the questions. Someone might already be able to tell you what's going on or at least take an educated guess.
Edit 2, reply to comments:
Something that I mentioned and that is quite critical is the distance between the spots. Doesn't have to be exact but if it's less than 2 or 3 mm, chances are high that you exciting both at the same time. Explain precisely what's going on and update it in your main post please.
Lasers usually end up creating spotsizes of about 0.5 to 1mm in diameter, however dimension down to 0.1mm or up to 5 mm are not all that uncommon. 
Calculate the spotsize and take it into account
SAED is not necessary, normal or high-res (immersion) SEM is completely fine and easily allows for samples of several mm, and often even up to a few cm. I don't want you to go down to the crystal lattice (several nm) but I want to see if there are periodic structures in the hundreds of nm range or a few um. Look up how a butterfly wing works:

Now optical filters (interference ones especially) do not act the same when light hits it from different angles. If light comes in from a different angle than incidence it does not block/pass the exact same light. Many normal glasses have anti-glare polarizers and coatings which can affect color(-perception) when viewing things under an angle. Laser goggles might block more than they say if light hits it under a specific angle (not a 100% sure about this, probably depends on the laser goggles used). Interference filters that are supposed to block the laser-light (and possibly other background light) can block additional/different wavelengths if the spot isn't straight under (perpendicular) the objective and the lenses. 
Now the first thing you can do to check if it's due to your eyes/goggles, is when you see the spot move around the sample and see if the spot is visible from different angles at the same location. If it is, good then you've most likely confirmed that it's actually there. Then decrease the power of the laser and see if it disappears at the same time as the purple spot. If it disappears earlier, then we know it's weaker most likely and it probably indicates that it's a secondary induced PL. Which can sometimes actually be excited by it's own PL at a lower wavelength.
As you can see in these paper some crystal can also have multiple PL wavelengths at the same time. 
If by this time we still don't know what's causing it, put it under a SEM and check if the surface is periodic or not.
