Are there still open problems in classical wave optics?

[Seanskahn]

I have been revisiting my notes from my 2nd and 3rd year physics degree - especially the ones covering Fourier Optics, and other classical wave optics - and it is quite rewarding to revisit the historical / exploratory aspect of the series of discoveries, that built the foundations of this particular area.
I have been wondering :

1. Are there still unresolved problems in classical wave or geometrical optics, seen from a physical perspective (in contrast to an engineering perspective)?
2. If so, what would be the latest attempts to resolve that.

Thank you.
Edit : to release this from hold : I would define open problems as :

1. Observation confirms the existence of something, however, there is no explanation for it.
2. A value or parameter whose existence is expected, but can't be computed yet

I think this sufficiently narrows everything down. I posted the question in physics stack exchange, but is got put on hold..

 

[Charles Link]

I think most of the problems of classical optics have been solved. A few years ago, I thought I may have come up with something new, and later wrote this Insights article about it https://www.physicsforums.com/insights/fabry-perot-michelson-interferometry-fundamental-approach/ only to find from a couple others on this forum that J.Schwinger (around 1930-1940) invented the matrix methods for a beamsplitter that did the exact same thing I was doing.
Another Optics problem that puzzled me for a long time, (How could the focused intensity be proportional to $A^2$ and still have energy conservation ? where $A$ is the area of the incident beam) ,before I finally solved it, is written up in another Insights:
https://www.physicsforums.com/insights/diffraction-limited-spot-size-perfect-focusing/
There still may be some unsolved problems, but it takes much work to be up-to-date on everything that has been solved.
A couple other interesting problems have appeared on this Physics Forums regarding the Michelson interferometer: See https://www.physicsforums.com/threa...-laser-in-interferometer.951709/#post-6034537
And for a good exercise in scattering theory from a crystal, try this thread: https://www.physicsforums.com/threads/diffraction-on-periodic-structures.952210/#post-6036368
And if you want to read about diffraction grating spectrometers, see https://www.physicsforums.com/threads/spectrometer-bandpass-and-resolution.922304/#post-5819920 Hopefully some of this is helpful for you.

 

[Andy Resnick]

I have been revisiting my notes from my 2nd and 3rd year physics degree - especially the ones covering Fourier Optics, and other classical wave optics - and it is quite rewarding to revisit the historical / exploratory aspect of the series of discoveries, that built the foundations of this particular area.
I have been wondering :

1. Are there still unresolved problems in classical wave or geometrical optics, seen from a physical perspective (in contrast to an engineering perspective)?
2. If so, what would be the latest attempts to resolve that.

Thank you.
Edit : to release this from hold : I would define open problems as :

1. Observation confirms the existence of something, however, there is no explanation for it.
2. A value or parameter whose existence is expected, but can't be computed yet

I think this sufficiently narrows everything down. I posted the question in physics stack exchange, but is got put on hold..

For classical optics, not really- Maxwell's equations basically closed the book. That said, there is still plenty of useful research being done on the generation/engineering of partially coherent beams, photonic bandgap materials, adaptive optics, stuff like that.

For quantum optics, there are still 'open problems'.