Dear Afshan Begum , I would say that SEM is still your best option given the relatively small area of your arrays and their repetitive pattern. There are two approaches, the first one would be sampling your array at different places, taking pictures of the array at these places (at the right magnification), analyze the regularity of these samples and then strapolate to the whole array. The second option would be to sample the whole 3x3mm2 array, recording a collection of images at the right magnification and further stiching them and perform the regularity studies on the whole array.

Another option, could be optical profilometry. 300nm is close to difraction limit, but you also have to take into account the pitch between your elements, if it is big enough probably the technique could do the job (at least at some level of definition of your elements, I mean, proabably the technique could define each individual element, but their roughness would be smoothed by the resolution)

If your 2D photonic crystal is designed to have a well defined bandgap, you could compare the results of simulation (perfect array) with the results from your real object, and study how far it is from the predicted behaviour and then try to relate that differences with some kind of irregularity on you real array. Probably this is what you already did, and now you are looking for an explanation of these differences, so back again to the previous techniques.

Hope it helps.

Dear Manuel Gómez thank you for 3 different ways to perform a check. You are right about having compared simulation results to measured results.

I will try optical profilometry (pitch is greater than 300 nm), it appears to be less time consuming than recording whole 3mm^2 array. I will update here when I have completed the analysis.

Have a nice day!

After some assessment, I did the following to resolve my question. For a quick check of regularity in nano featured large Photonic Crystal arrays:

1. Uniform intensity diffraction spot check:

After shining visible laser at normal incidence, the intensity of diffraction spots, should be almost uniform. Depending on lattice type, the number of spots will vary, for triangle lattice with C6v symmetry, 6 diffraction spots equidistant from centre and so on.

2. Uniform colour gradation in white light:

When you tilt array under white light, the colour gradation should be smooth, colours ranging in VIBGYOR at various angles. If it doesn't appear smooth, we may have to check our CAD files for various issues.

For a rigorous check, the methods mentioned by Manuel Gómez can be performed.

If there are more methods to check/any queries for above method, I am open to questioning.

Thank you

use the program ImageJ

many applications have been written to it. find what you need

Dear Afshan Begum I second the suggestions and thoughts given by Manuel Gómez

In addition, you may also look into:Article Bloch Surface Waves and Internal Optical Modes Driven Photon...

Good luck!