A laser resonator includes a pair of optical elements forming a first optical path having a focused beam waist, one or more mirrors forming a second optical path of approximately parallel light connected to the first optical path, and a laser medium arranged in the second optical path. Induced emission light generated from the laser medium reciprocates or circles in a path formed by the first optical path and the second optical path. A distance between the pair of optical elements is adjustable, and a beam diameter at the second optical path is adjusted by adjusting the distance between the pair of optical elements.

A resonator is provided that includes opposing mirrors arranged substantially parallel to each other and separated to confine reflections for gain. A gain medium is between the opposing mirrors. A pump pumps the gain medium. At least one microrefractive element, or tens, hundreds, thousands, millions or more, stabilizes the resonator. The refractive element is disposed between the opposing mirrors and is configured to support a laser beam at a position of the refractive element. A method for producing laser light directs pump light onto one or a plurality of microrefractive elements. Reflections from the one or a plurality of microrefractive elements are confined in a resonator volume. Gain is provided in the resonator volume. Laser energy is emitted from the resonator volume.

Methods, systems and apparatus are disclosed for delivery of pulsed treatment radiation by employing a pump radiation source generating picosecond pulses at a first wavelength, and a frequency-shifting resonator having a lasing medium and resonant cavity configured to receive the picosecond pulses from the pump source at the first wavelength and to emit radiation at a second wavelength in response thereto, wherein the resonant cavity of the frequency-shifting resonator has a round trip time shorter than the duration of the picosecond pulses generated by the pump radiation source. Methods, systems and apparatus are also disclosed for providing beam uniformity and a sub-harmonic resonator.

A polarisation and mode selection technique for a gas waveguide laser is described in which a surface of the waveguide is formed to be substantially dielectric with a localised metallic region therein. The metallic region provides linear polarisation while the dielectric surface provides for low order mode selection. Embodiments are described to channel and planar waveguides with various resonator configurations. Ranges are provided for the size and location of the metallic region on the waveguide surface.

Methods, systems and apparatus are disclosed for delivery of pulsed treatment radiation by employing a pump radiation source generating picosecond pulses at a first wavelength, and a frequency-shifting resonator having a lasing medium and resonant cavity configured to receive the picosecond pulses from the pump source at the first wavelength and to emit radiation at a second wavelength in response thereto, wherein the resonant cavity of the frequency-shifting resonator has a round trip time shorter than the duration of the picosecond pulses generated by the pump radiation source. Methods, systems and apparatus are also disclosed for providing beam uniformity and a sub-harmonic resonator.

Methods, systems and apparatus are disclosed for delivery of pulsed treatment radiation by employing a pump radiation source generating picosecond pulses at a first wavelength, and a frequency-shifting resonator having a lasing medium and resonant cavity configured to receive the picosecond pulses from the pump source at the first wavelength and to emit radiation at a second wavelength in response thereto, wherein the resonant cavity of the frequency-shifting resonator has a round trip time shorter than the duration of the picosecond pulses generated by the pump radiation source. Methods, systems and apparatus are also disclosed for providing beam uniformity and a sub-harmonic resonator.

A method for designing a non-circular dielectric resonator is provided. The method includes obtaining a conformal transformation coordinate of the non-circular dielectric resonator to correspond to a rectangular coordinate system of a circular dielectric resonator, mapping the obtained conformal transformation coordinate to the non-circular dielectric resonator, and setting a refractive index in the non-circular resonator and allowing an incident angle of light to satisfy a condition for total reflection in each of boundary areas in a non-circular dielectric resonator to which the conformal transformation coordinate is mapped.

There are provided: a planar waveguide in which claddings (2) and (3) each having a smaller refractive index than a laser medium for absorbing pump light (5) are bonded to an upper surface (1a) and a lower surface (1b) of a core (1) which is formed from the laser medium; pump light generation sources (4a) and (4b) for emitting pump light (5) to side surfaces (1c) and (1d) of the core (1); and laser light high reflection films (6a) and (6b) formed on side surfaces (1e) and (1f) of the core (1). Each of side surfaces (2e) and (2f) of the cladding (2) corresponding to the side surfaces (1e) and (1f) of the core (1) has a ridge structure (20) in which a part thereof is recessed.

Both of multi-mode laser beam 8A and excitation beam 34A for amplification are imputed to an amplification gain medium 62 in a relationship in which their optical axes match each other and an effective beam diameter of the excitation beam for amplification is smaller than an effective beam diameter of the multi-mode laser beam. As a result, laser beam of a part of modes progressing in a radiation range of the excitation beam 34A for amplification is selectively amplified. Laser beam 40A subjected to mode cleaning is thereby outputted.

Provided is a laser resonator for generating a laser light by absorbing energy from outside. The laser resonator includes a metal body and a gain medium layer having a ring shape. The gain medium layer of a ring shape may be provided on the metal body and may generate the laser light by a plasmonic effect.