A laser beam having desired properties is output at desired timings. A laser apparatus is a laser apparatus for use with an extreme ultraviolet light generating apparatus that generates extreme ultraviolet light at a repetition frequency which is set in advance, and may be equipped with: a semiconductor laser that outputs a laser beam when a trigger signal is input thereto; an optical switch that switches between a state in which the laser beam passes therethrough and a state in which the laser beam does not pass therethrough, provided along the optical path of the laser beam; and a control unit configured to output the trigger signal to the semiconductor laser at a frequency which is an integer multiple of the repetition frequency, and to control the optical switch such that the laser beam passes therethrough at the repetition frequency.

A laser device may include a light source configured to emit a laser beam in burst operation, an optical sensor configured to acquire a cross sectional image of the laser beam during a certain period for every certain cycle, an image processor configured to receive an input of an image signal of the cross sectional image outputted from the optical sensor and output beam relating information about the laser beam, a beam traveling direction adjuster configured to adjust a traveling direction of the laser beam, and a controller configured to control the beam traveling direction adjuster based on the beam relating information when at least a part of a period in which the optical sensor acquires the cross sectional image is overlapped with a period in which the light source emits a laser beam.

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.

Disclosed is a laser system including a source, for generating a source signal, and an optical amplifier system. The laser system includes a pulse selection or variation device configured to select or vary the source signal so as to form a main signal composed of one or more light pulses. The main signal is temporally variable in terms of rhythm and/or amplitude. The laser system is configured to inject the main signal and a secondary signal into the optical amplifier system. The secondary signal is varied on the basis of the temporal variation in terms of rhythm and/or amplitude of the main signal so as to stabilize the power stored in the optical amplifier system in a time-dependent manner, and the laser system is configured to spatially separate the amplified main signal from the amplified secondary signal.

An extreme ultraviolet light (EUV) generation system is configured to improve conversion efficiency of energy of a laser system to EUV energy by improving the efficiency of plasma generation. The EUV generation system includes a target generation unit configured to output a target toward a plasma generation region in a chamber. The laser system is configured to generate a first pre-pulse laser beam, a second pre-pulse laser beam, and a main pulse laser beam so that the target is irradiated with the first pre-pulse laser beam, the second pre-pulse laser beam, and the main pulse laser beam in this order. In addition, the EUV generation system includes a controller configured to control the laser system so that a fluence of the second pre-pulse laser beam is equal to or higher than 1 J/cm.sup.2 and equal to or lower than a fluence of the main pulse laser beam.

Direct diode-pumped Ti:sapphire laser amplifiers use fiber-coupled laser diodes as pump beam sources. The pump beam may be polarized or non-polarized. Light at wavelengths below 527 nm may be used in cryogenic configurations. Multiple diode outputs may be polarization or spectrally combined.

The present disclosure provides an excimer laser system. A master oscillator chamber may generate laser pulses with a narrowed line width and a small energy by means of a line width narrowing module, as a seed light. The seed light is refracted by a master oscillator wavefront engineering box and then incident into a power amplifier chamber through a beam splitting system. The beam splitting system, a first high reflectance mirror, a second high reflectance mirror and a third high reflectance mirror may constitute a quadrilateral annular optical path, The power amplifier chamber may have a first pair of Brewster windows and a second pair of Brewster windows, wherein the first pair of Brewster windows is located in a first optical path of the annular optical path along with a discharging electrode of the power amplifier chamber, and the second pair of Brewster windows is located in a second optical path of annular optical path which is parallel to a first amplification optical path. The present disclosure reduces the length of a ring cavity of an excimer laser system with a ring cavity structure, increasing the amplification times and achieving a deeper gain saturation amplification than a traditional structure, thereby improving the output characteristic of the excimer laser system.

A multipass laser amplifier includes a mirror, a mirror device, a gain crystal, and refractive or diffractive beam-steering element. The gain crystal is positioned on a longitudinal axis of the multipass laser amplifier between the mirror and the mirror device. The beam-steering element is positioned on the longitudinal axis between the gain crystal and the mirror device. The beam-steering element has no optical power and deflects a laser beam, by refraction or diffraction, for each of multiple passes of the laser beam between the first mirror and the mirror device, such that each pass goes through the gain crystal for amplification of the laser beam and goes through a different respective off-axis portion of the beam-steering element. The no optical power of the beam-steering element enables maintaining a large beam size in the gain crystal, thereby facilitating amplification to high average power.

Techniques for controlling an optical system include accessing a measured value of a property of a particular pulse of a pulsed light beam emitted from the optical system, the property being related to an amount of coherence of the light beam; comparing the measured value of the property of the light beam to a target value of the property; determining whether to generate a control signal based on the comparison; and if a control signal is generated based on the comparison, adjusting the amount of coherence in the light beam by modifying an aspect of the optical system based on the control signal to reduce an amount of coherence of a pulse that is subsequent to the particular pulse.

A high-efficiency high-power ring laser amplifier includes four polarizers, four amplifiers, fours lens, two filter apertures, two electro-optic switches, a mirror, a wavefront corrector. A bidirectional ring laser amplifier configuration with twin pulses is suitable for any type of gain media and pumping configurations. This amplifier configuration can effectively improve the extraction efficiency of the gain medium. The amplification configuration proposed by the present invention patent can realize the ring amplification for any number of rounds in principle, and can effectively control quality of the output laser beam and relax the restriction on the injected energy. The two spatial filters in the novel high-efficiency high-power ring laser amplifier of the present invention patent can effectively removing the spatial modulations in the laser beams, and the first and second spatial filters reimage the beam at wavefront corrector to mirror which can effectively inhibit the diffraction effect.