Laser Radio wave Detector (thinking)

origin of idea -> Ultra sensitive detection of radio waves with lasers

I have been making Software Defined Radio in these years. SDR is amasing and intereting technology for amature radio hobbist. We can see radio waves spectrum on my PC display now. View of radio waves is very fun. But I think weak signals can not be seen on display.

I learned about thermal noise. There is thermal noise in radio circuit. Signals weaker than thermal noise can not be heard . This is common sense in technology.