Distributed coupled resonator laser
A laser system involving coupled distributed resonators disposed serially, with the lasing gain medium located in the main resonator and the output of that resonator being directed into a free space resonator, such that the main resonator output mirror is effectively the free space resonator. The distributed resonators end mirrors are retroreflectors. Interference occurs between light traveling towards the remote mirror of the free space resonator and light reflected therefrom, generating regions of high reflectivity. The coupling of the free space resonator to the regions of high reflectivity of the free space resonator enables the first resonator to lase efficiently, even though the true reflectivity of the main resonator output mirror outside of those regions is insufficient to enable efficient lasing, if at all. This coupled resonator structure enables lasing to occur with a high field of view and the high gain engendered by the high reflectivity regions.
1. A distributed laser comprising:
a first retroreflector acting as a back mirror of said distributed laser;
a gain medium, positioned within the field of view of said first retroreflector;
a second retroreflector having a partially reflective surface;
a third retroreflector comprising said partially reflective surface, said third retroreflector being disposed on the opposite side of said partially reflective surface to said first retroreflector and said gain medium; and
a fourth retroreflector,
wherein said retroreflectors are serially disposed, with said fourth retroreflector facing said third retroreflector and remotely located from said third retroreflector.
2. The distributed laser according to claim 1 , wherein said second retroreflector is disposed within the field of view of said first retroreflector.
3. The distributed laser according to claim 1 , wherein said gain medium is within the field of view of said second retroreflector.
4. The distributed laser according to claim 1 , wherein the power through the entrance pupil to said fourth retroreflector divided by the area of said gain medium is not more than 10% of the saturation intensity of said gain medium.
5. The distributed laser according to claim 1 , wherein the diameter of said fourth retroreflector is smaller than the beam diameter as measured at its 1/e 2 point, on said fourth retroreflector.