Wavelength-locked quasi-unidirectional ring cavity with diffraction grating output coupler

A ring-laser system for generating coherent optical radiation, comprising:

• a ring cavity comprising:
• three or more reflectors configured to provide a forward-circulation pathway delineating a forward circulation within the ring cavity and a reverse-circulation pathway delineating a reverse circulation within the ring cavity, the forward-circulation pathway and the reverse-circulation pathway being overlapping, counter-directional optical pathways;
• and
• a gain medium disposed within the ring cavity that is bidirectionally incorporated into the forward-circulation pathway and the reverse-circulation pathway;
• a forward-drain optical pathway for tapping a portion of light from the forward-circulation pathway;
• a reverse-drain optical pathway for tapping a portion of light from the reverse-circulation pathway as optical feedback;
• a forward-source optical pathway for inserting additional light into the forward-circulation pathway;
• and
• an optical feedback component configured to optically couple the reverse-drain optical pathway to the forward-source optical pathway,
• wherein the optical feedback, redirected from the reverse-drain optical pathway to the forward-source optical pathway by the optical feedback component, is configured to augment an optical signal in the forward-circulation pathway such that an optical mode in the forward-circulation pathway attains preferential gain in the gain medium relative to a corresponding optical mode in the reverse-circulation pathway.

A free-space ring-cavity laser system for generating coherent optical radiation at a wavelength, comprising:

• a ring cavity configured to provide a forward-circulation pathway delineating a forward circulation within the ring cavity and a reverse-circulation pathway delineating a reverse circulation within the ring cavity;
• a gain medium disposed within the ring cavity that is bidirectionally incorporated into the forward-circulation pathway and the reverse-circulation pathway;
• an output pathway for coupling a portion of light from the forward-circulation pathway to a laser-system output;
• and
• a feedback pathway for unilaterally redirecting a portion of light from the reverse-circulation pathway into the forward-circulation pathway,
• wherein optical feedback on the feedback pathway is configured to establish a cavity mode of the forward circulation pathway at the wavelength as a dominant-power mode of the free-space ring-cavity laser system, and establish a cavity mode of the reverse-circulation pathway at the wavelength as an idle-power mode of the free-space ring-cavity laser system.