I'm looking at the time reversed laser and I was having trouble understanding why we call this device a laser. To me this device is more like the absorbers found in FDTD codes, something like a CPML.
I am having trouble finding the analogs to the following processes in traditional lasers.
- What is the mechanism for feedback. In a laser we have stimulated emission producing an exponential increase in output intensity, until the system saturates. In the reverse laser I only see an attenuation constant, whose constant value to me seems exactly like an absorber and not a laser.
- Does this device have modes, does the feedback select an absorption width that narrows? The claims of an absorb band corresponding to the visible range (200nm-800nm) is a rather broad range that is characteristic of mostly everything?
- What does population inversion and threshold mean for the reverse laser? If it is an absorber doesn't that mean that even a single photon knocks it out stability. In one paper the authors described a 2 state reverse laser system, we know that a 2 state laser is not possible....
Some images of time reversed lasers.
Where is the lasing?