Methods and apparatus for laser mode transformation

A method for generating a spatial transformation of the internal mode of a laser, the method comprising:

• disposing a laser gain medium within a laser cavity structure;
• arranging an interferometric device comprising optical components to complete the laser cavity structure, wherein the interferometric device receives an input beam from laser oscillation in the laser cavity structure, splits the input beam into two sub-beams, and recombines the two sub-beams to provide an optical feedback beam to sustain laser oscillation;
• configuring the optical components that comprise the interferometric device to provide relative misalignment of the two sub-beams that are produced internally to the interferometric device;
• using at least a first output port of the interferometric device to provide an output beam of the laser that due to the misalignment is a spatial transformation of the internal mode structure of the laser;
• and
• using at least a second output port of the interferometric device to provide the optical feedback beam to the laser cavity structure that sustains laser oscillation with a spatial structure that substantially preserves the internal mode structure of the laser;
• wherein the misalignment of the optical components in the interferometric device causes a symmetric lateral displacement of each of the two sub-beams in one plane that is less than half the beam field waist radial size and a symmetric angular offset of each the two sub-beams in an orthogonal plane that is less than half the divergence angle of the internal mode of the laser;
• when the internal mode of the laser is a Gaussian beam;
• and
• wherein a mode transformed vortex Laguerre-Gaussian beam LG01 or LG0-1 is generated from the first output port of the interferometric device.

An apparatus for generating a spatial transformation of the internal mode of a laser, the apparatus comprising:

• a laser gain medium disposed within a laser cavity structure;
• and
• an interferometric device comprising optical components arranged to complete the laser cavity structure, wherein the interferometric device is configured to receive an input beam from laser oscillation in the laser cavity structure, to split the input beam into two sub-beams, and to recombine the two sub-beams to provide an optical feedback beam to sustain laser oscillation;
• wherein the optical components that comprise the interferometric device are configured to provide relative misalignment of the two sub-beams that are produced internally to the interferometric device;
• at least a first output port of the interferometric device is configured to provide an output beam of the laser that due to the misalignment is a spatial transformation of the internal mode structure of the laser;
• and
• at least a second output port of the interferometric device is configured to provide the optical feedback beam to the laser cavity structure to sustain laser oscillation with a spatial structure that substantially preserves the internal mode structure of the laser,
• wherein the misalignment of the optical components in the interferometric device causes a symmetric lateral displacement of each of the two sub-beams in one plane that is less than half the beam field waist radial size, or a symmetric angular offset of each of the two sub-beams in one plane that is less than half the divergence angle of the internal mode of the laser;
• wherein the internal mode of the laser is a Gaussian beam;
• and
• wherein a mode transformed Hermite-Gaussian beam HG01 or HG10 is generated and emitted from the first output port of the interferometric device.