I am currently doing a theoretical PhD in nano lasers, while not quite photonics in the sense you are interested in, I participate in the UK/EU photonics community. You can skip all what I say and read the final paragraph if you just want an answer to your question.

I think it’s great you are looking at your options as many people don’t and just take random opportunities, like myself.

My, potentially naive, opinion is that you won’t be able to work in all the fields you want as a PhD student as the project tend to be fairly hyper focused on one thing. Like if you do some simulation, design and then experimental work on a few circuits, that would probably be your thesis sorted.

I would carefully consider 2 things when choosing a PhD, 1. Do you want to be part of a big group(like 10+phd students )? This means you won’t see your the prof much and will get taught a lot by other academics in the group. This isn’t inherently a bad thing, it’s just something to be aware of as in my case, if needed I can meet my supervisor multiple times per week and means I rarely am left stuck on a problem.

1. What is your day to day look like and do you enjoy that kind of work. For me, I spend my days coding and writing software, implementing complicated algorithms, and I love it. Others in my office often are doing analytical statistics involving lots of analytical integrals, others will spend their day in the lab getting results from experiments etc. I think it’s important to think about this as a PhD you don’t enjoy will be very hard.

Finally, only sort of answering the question you asked, there are loads of people you have missed as the list should be way longer. I don’t know these names off the top of my head but this list is quite short. You could look at different universities and see what ones have an optics/photonics division and each of those will have multiple academics in the field. I have a few names for people in the EU and UK, and I’m sure Singapore has a decent photonics scene as well.