A multiple frequency laser system and method for treating skin conditions via a handpiece features a pump laser module having a single laser beam at a first frequency. A dual laser module receives the laser beam at the first frequency and includes dual free running laser resonators to produce a laser beam at a second frequency and a laser beam at a third frequency. A frequency conversion module receives as inputs the laser beam at the second frequency and the laser beam at the third frequency and is configured to selectively provide laser beams to the handpiece including a second harmonic generation of the second frequency, a second harmonic generation of the third frequency, a summed frequency generation of the second frequency and the third frequency, the laser beam at the first frequency, the laser beam at the second frequency, and/or the laser beam at the first frequency combined with the laser beam at the second frequency. The handpiece receives the laser beams from the frequency module and delivers them to skin for treatment.

A laser including a solid state laser gain medium having a D-shaped cross section and an unstable resonator laser cavity including the solid state laser gain medium configured with a geometric magnification in a range of 1 to 5 under the intended operating conditions, including the effects of thermal lensing in the gain medium. An optical switching device in the unstable resonator laser cavity generates a pulse duration in the range of 0.05 to 100 nanoseconds. A diode-pump source is configured to inject pump light through the curved or barrel surface of the D-shaped gain medium.

An amplifier may include a chamber, and first and second mirrors. The chamber may include a pair of discharge electrodes opposed to each other in a first direction, a laser exciting medium, an input window allowing seed light to pass therethrough into the chamber, and an output window allowing amplified laser light to pass therethrough to outside in a second direction intersecting with the first direction. The first and second mirrors may each include a reflection region, and be opposed to each other in a third direction intersecting with the first direction with the pair of discharge electrodes in between. A projected image of the reflection region of the first mirror in the second direction and a projected image of the reflection region of the second mirror in the second direction may provide a gap of a size equal to or greater than zero in between.

An external resonator-type semiconductor laser device 1A includes an external resonator formed of one or a plurality of laser diode light sources and a VBG; an optical fiber which outputs output light La from the laser diode light source toward the VBG, and into which return light Lb from the VBG is input; and a displacement unit that displaces a disposition position of the VBG with respect to an input and output end surface of the optical fiber.

A CO.sub.2 laser that generates laser-radiation in just one emission band of a CO.sub.2 gas-mixture has resonator mirrors that form an unstable resonator and at least one spectrally-selective element located on the optical axis of the resonator. The spectrally-selective element may be in the form of one or more protruding or recessed surfaces. Spectral-selectivity is enhanced by forming a stable resonator along the optical axis that includes the spectrally-selective element. The CO.sub.2 laser is tunable between emission bands by translating the spectrally-selective element along the optical axis.

A laser system for generating a series of laser pulses comprising a laser generator that supplies an injection pulse to an amplifier; said amplifier comprising: a gain medium enclosed between a first mirror and a second, output, mirror opposite to said first mirror; and an optical switch set in the proximity of said first mirror; said laser system being characterized in that said amplifier is an unstable laser resonator and said injection pulse is supplied to said laser resonator in synchronism with opening of said optical switch; said series of laser pulses comprises at least one pulse having a duration shorter than or equal to 2 ns and an energy higher than 100 mJ and at least three times higher than the energy of any other pulse of said series of pulses.

A semiconductor laser device includes: a semiconductor laser array in which a plurality of active layers that emit laser lights with a divergence angle .sub.S (>4) in a slow axis direction are arranged; a first optical element that reflects first partial lights by a first reflecting surface and returns the first partial lights to the active layers; and a second optical element that reflects partial mode lights of second partial lights by a second reflecting surface and returns the partial mode lights to the active layers, the first reflecting surface forms an angle equal to or greater than 2 and less than (.sub.S/2) with a plane perpendicular to an optical axis direction of the active layers, and the second reflecting surface forms an angle greater than (.sub.S/2) and equal to or less than 2 with the plane perpendicular to the optical axis direction of the active layers.

Gaseous laser systems and related techniques are disclosed. Techniques disclosed herein may be utilized, in accordance with some embodiments, in providing a gaseous laser system with a configuration that provides (A) pump illumination with distinct edge surfaces for an extended depth and (B) an output beam illumination from a resonator cavity with distinct edges in its reflectivity profile, thereby providing (C) pump beam and resonator beam illumination on a volume so that the distinct edge surfaces of its pump and resonator beam illumination are shared-edge surfaces with (D) further edge surfaces of the amplifier volume at the surfaces illuminated directly by the pump or resonator beams, as defined by optical windows and (optionally) by one or more flowing gas curtains depleted of the alkali vapor flowing along those optical windows. Techniques disclosed herein may be implemented, for example, in a diode-pumped alkali laser (DPAL) system, in accordance with some embodiments.

A MOPA laser system that includes a seed laser configured to output pulsed laser light, an amplifier configured to receive and amplify the pulsed laser light emitted by the seed laser; and a pump laser configured to deliver a pump laser beam to both the seed laser and the amplifier.

A device includes a first sensor configured to generate a first output signal corresponding to an energy of a portion of a forward beam transmitted by a mirror of a laser resonator system. The device further includes a second sensor configured to generate a second output signal corresponding to an energy of a portion of a return beam transmitted by the mirror. A ratio of the energy of the portion of the forward beam and the energy of the portion of the return beam corresponds to a measurement of a feedback ratio of the laser resonator system.