A laser system may include a controller configured to direct a plurality of temporally spaced-apart electrical pulses to a device that optically pumps a lasing medium, and a lasing medium configured to output a quasi-continuous laser pulse in response to the optical pumping. The plurality of temporally spaced-apart electrical pulses may include (a) a first electrical pulse configured to excite the lasing medium to an energy level below a lasing threshold of the lasing medium, and (b) multiple second electrical pulses following the first electrical pulse. The quasi-continuous laser pulse is output in response to the multiple second electrical pulses.

A plate-like laser medium has a through-hole for providing a flow of a cooling medium. The laser medium unit includes the plurality of laser media. A laser beam amplification device includes a laser medium unit 10, an excitation light source 21 that causes excitation light to enter the laser medium unit 10, a through-hole 16a of a window member as a unit for supplying the cooling medium in a through-hole 14a of the laser medium 14, and a cooling medium flow path F1 arranged around the laser medium unit 10.

A plate-like laser medium has a through-hole for providing a flow of a cooling medium. The laser medium unit includes the plurality of laser media. A laser beam amplification device includes a laser medium unit 10, an excitation light source 21 that causes excitation light to enter the laser medium unit 10, a through-hole 16a of a window member as a unit for supplying the cooling medium in a through-hole 14a of the laser medium 14, and a cooling medium flow path F1 arranged around the laser medium unit 10.

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.

The laser device includes a laser crystal, a resonator including a pair of mirrors between which the laser crystal is interposed, a Q switch that is disposed on an optical path of the resonator and controls a Q value of the resonator, and a Brewster thin-film polarizer that is disposed on the optical path of the resonator and transmits selectively p-polarized light. The thin-film polarizer has wavelength selectivity in which a p-polarized light transmittance at a first wavelength exhibiting a maximum gain of the laser crystal is 5% or more to 25% or less, the p-polarized light transmittance monotonically increases as a wavelength becomes longer than the first wavelength, and a maximum transmittance is exhibited at a third wavelength. The laser device oscillates laser light at a second wavelength that is a wavelength longer than the first wavelength and shorter than or equal to the third wavelength.

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.

In a solid-state laser device and a photoacoustic measurement device including the solid-state laser device, the distance between a laser rod and a flash lamp is narrowed. A shielding lid shields mirrors and an optical path of laser light from the outside. A first portion of a frame body of a laser chamber is exposed from the shielding lid. A flash lamp stored in the frame body of the laser chamber is able to be removed from and inserted into the first portion of the frame body. A thin film portion having a thickness smaller than the thickness of other portions of the shielding lid is provided in at least a part of a region of the shielding lid covering the optical path of a light beam on the outside in a longitudinal direction from the first portion of the frame body of the laser chamber.

In a solid-state laser device and a photoacoustic measurement device including the solid-state laser device, the distance between a laser rod and a flash lamp is narrowed. A shielding lid shields mirrors and an optical path of laser light from the outside. A first portion of a frame body of a laser chamber is exposed from the shielding lid. A flash lamp stored in the frame body of the laser chamber is able to be removed from and inserted into the first portion of the frame body. A thin film portion having a thickness smaller than the thickness of other portions of the shielding lid is provided in at least a part of a region of the shielding lid covering the optical path of a light beam on the outside in a longitudinal direction from the first portion of the frame body of the laser chamber.

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 solid-state laser device includes a laser rod made of an alexandrite crystal; a flash lamp that outputs excitation light for exciting the laser rod, a glass tube for a lamp being made of quartz glass that at least blocks deep ultraviolet light having a wavelength of 200 nm to 300 nm, and transmits visible light having a wavelength of 400 nm or more; and a laser chamber that contains a tubular reflector that includes a hole part containing at least a portion of the laser rod or a portion of the flash lamp and is made of a porous material of polytetrafluoroethylene, an inner wall surface of the hole part being as a reflecting surface that reflects the excitation light.