CLEO (Conference on Lasers and Electro-Optics) will be online this year, May 5th -11th. This conference is a nice mix of science and engineering, focusing on applications of optics. You do have to register, but the conference itself is free for attendees. Details about registration and sessions can be found here: https://www.cleoconference.org/home/.
The plenary talks should be accessible to a broad audience. You can check out the line up here: https://www.cleoconference.org/home/program/plenary-speakers/. All times are Pacific Time Zone.