A laser system includes a multipass amplifier for amplifying laser light and providing an amplified output beam, and a control unit. The multipass amplifier includes a laser-active medium. The control unit is configured to keep a thermal load on the laser-active medium substantially constant over a range of a laser output power of the output beam. The thermal load is determined by at least two different power sources.

A multi-stage optical amplifier has an input port for receiving an optical signal and a relatively short erbium doped optical fiber is coupled to the input port. Complex costly pump feedback is not required as a constant non-varying saturation pump is configured to provide non varying output power pump light of a predetermined wavelength suitable for excitation and full saturation of the erbium ions such that a full population inversion occurs. The length of the short erbium doped fiber and rare earth doping concentration of the erbium doped fiber is such that when pumped by said pump provides amplification of the optical signal of less than 15 dB. Locating a gain flattening filter after the short erbium doped optical fiber provides a relatively flat amplified output signal. Multi-stages of similar short erbium doped fibers pumped and saturated by the same pump signal economically provide increased amplification of the signal and filters after each state flatten the gain.

An erbium doped block of glass has input port and reflective end faces arranged such that a signal is launched into the block and is amplified as it traverses the block following a zig-zag path. A laser diode pump is focused to excite erbium ions within the block thereby amplifying the input signal light traversing the block numerous times. A gain flattening filter flattens the gain of the signal being amplified numerous times as the filter is within the path upon each pass across the block.

A device may include a transient optical amplifier having stored energy associated with a lower boundary and an upper boundary of a dynamic equilibrium, and a target level defining stored energy for amplifying a high energy input pulse to a higher energy output pulse. The device may include a pump to increase the amplifier's stored energy, and a source to pass low energy control pulses or the high energy input pulse to the amplifier. The device may include a controller configured to maintain the amplifier's stored energy in the dynamic equilibrium by requesting low energy control pulses for the amplifier at a high repetition frequency. The controller may wait to receive a trigger. Based on receiving the trigger, the device may stop passing low energy control pulses to the amplifier, and may pass the high energy input pulse to the amplifier when the amplifier's stored energy reaches the target level.

There may be provided a laser amplifier including: a chamber containing a laser medium; a first window provided on the chamber, and configured to allow a laser light beam inputted from outside of the chamber to enter the chamber; an excitation unit configured to amplify, by exciting the laser medium, the laser light beam that has entered the chamber; a second window provided on the chamber, and configured to allow the laser light beam that has been amplified by the excitation unit to exit from the chamber to the outside; a mirror provided on a laser light path between the first window and the second window; and a wavelength selection film provided on one or more of the first window, the second window, and the mirror, and configured to suppress propagation of light beams of one or more suppression target wavelengths different from a desired wavelength.

There is provided a slab amplifier including an optical system (48, 51) provided in a chamber (47) to allow a seed beam having entered from a first window into the space between a pair of electrodes (42, 43) to be repeatedly reflected between the space so that the seed beam is amplified to be an amplified beam; a first aperture plate (61) provided between the first window and the electrodes, and having an opening of a dimension equal to or greater than a cross-section of the seed beam and equal to or smaller than a dimension of the first window; and a second aperture plate (62) provided between the second window and the electrodes, and having an opening of a dimension equal to or greater than a cross-section of the amplified beam and equal to or smaller than a dimension of the second window.

An optical rotating device for injecting a laser beam may include deflection devices between which the injected laser beam may rotate in the optical rotating device, and an extraction device that may extract the laser beam after carrying out a predetermined number of rotations in the rotating device. The deflection devices may be arranged such that the position of the laser beam during extraction is dependent on the number of rotations carried out in the optical rotating device.

A laser apparatus may include: an optical amplifier configured to amplify a laser beam outputted from a master oscillator; an optical-amplifier power supply configured to supply an alternating current for optical amplification to the optical amplifier; and a laser controller. The optical-amplifier power supply may include: an alternating current generation circuit including an inverter circuit configured to change output amplitude in accordance with a duty cycle, the alternating current generation circuit being configured to generate the alternating current from an output of the inverter circuit; and a power supply control circuit configured to hold control information defining correspondence relations between command values from the laser controller and duty cycles of the inverter circuit, determine a duty cycle corresponding to a command value received from the laser controller based on the control information, and provide the determined duty cycle to the inverter circuit.

An apparatus for generating and amplifying laser beams at approximately 1 micrometer wavelength is disclosed. The apparatus includes an ytterbium-doped gain-crystal pumped by an ytterbium fiber-laser. The fiber-laser enables a pump wavelength to be selected that minimizes heating of the gain-crystal. The apparatus can be configured for generating and amplifying ultra-fast pulses, utilizing the gain-bandwidth of ytterbium-doped gain-crystals.

Consolidated Master Oscillator Power Amplifier (MOPA) laser modules and method of fabrication thereof. A MOPA comprises a prefabricated chassis, comprising a plurality of surfaces, a master oscillator laser (MO), enduringly affixed to at least one first surface out of the plurality of surfaces, a power amplifier (PA), enduringly affixed to at least one second surface out of the plurality of surfaces, wherein a spatial relationship between the at least one first surface and the at least one second surface determines an alignment between the MO and the PA, and a beam transfer system (BTS), enduringly affixed to the prefabricated chassis, the BTS comprising a plurality of optical elements for transferring light outputted from the MO to the PA for amplification.