A laser system includes a beam shaping unit, a random phase plate, and a collimating optical system in an optical path between a solid-state laser device and an excimer amplifier. When a traveling direction of a laser beam entering the excimer amplifier is a Z direction, a discharge direction of a pair of discharge electrodes is a V direction, a direction orthogonal to the V and Z directions is an H direction, a shaping direction of the beam shaping unit corresponding to the V direction is a first direction, a shaping direction of the beam shaping unit corresponding to the H direction is a second direction, an expansion rate in the first direction is E1, and an expansion rate in the second direction is E2, the beam shaping unit expands a beam section of the laser beam such that an expansion ratio defined by E2/E1 is higher than 1.

The present invention relates to an optical module configured to be optically coupleable to a laser amplifier module, the optical module comprising an inner optical element having a plurality of M inner reflective elements arranged around a center of the inner optical element; and a plurality of N outer reflective elements arranged around the inner optical element, the plurality of N outer reflective elements being configured to face the inner optical element, wherein the plurality of M inner reflective elements and the plurality of N outer reflective elements are configured to provide an optical path for a laser beam.

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.

A laser processing method of performing laser processing on a transparent material that is transparent to ultraviolet light by using a laser processing system includes: performing relative positioning of a transfer position of a transfer image and the transparent material in an optical axis direction of a pulse laser beam so that the transfer position is set at a position inside the transparent material at a predetermined depth ΔZsf from a surface of the transparent material in the optical axis direction; and irradiating the transparent material with the pulse laser beam having a pulse width of 1 ns to 100 ns inclusive and a beam diameter of 10 μm to 150 μm inclusive at the transfer position.

A titanium-sapphire laser apparatus may include a continuous wave oscillation laser unit, an amplification oscillator, a pulsed laser unit, an error detector, an error controller, and an optical path length corrector. The amplification oscillator may include an optical resonator and a titanium-sapphire crystal that is provided in an optical path in the optical resonator. The error detector may be provided in an optical path of leak light of seed light from the optical resonator, and may detect an optical path length error between an optical path length in the optical resonator and a positive integer multiple of a wavelength of the seed light and output an optical path length error signal. The optical path length corrector may vary the optical path length in the optical resonator on a basis of a signal resulting from adding a correction value to the optical path error signal.

An example laser apparatus of the disclosure may include an oscillator capable of outputting a laser beam, a slab optical amplifier capable of amplifying the laser beam outputted by the oscillator by passing the laser beam through an optical amplification region shaped like a slab and outputting the amplified laser beam, and a mirror disposed on an optical path of the laser beam to enter the slab optical amplifier or the amplified laser beam outputted from the slab optical amplifier, the mirror being movable in a direction parallel to a plane where the laser beam travels in the slab optical amplifier.

The invention relates to a discoidal or cuboidal solid body for a laser amplification system of a solid-state laser, which solid body contains at least one laser-active material, has an upper side defining an upper side plane and a lower side defining a lower side plane, wherein the upper side plane and the lower side plane are inclined in relation to each other and enclose an angle of inclination, wherein the lower side is provided with a first reflective coating, wherein the upper side is provided with a second reflective coating, and wherein at least one of the upper side and the lower side has at least one optical input coupling opening for input coupling at least one of a seed laser radiation field and a pump laser radiation field into the solid body between the first and the second reflective coating.

Devices and methods for generating EUV light are disclosed. The device comprises an oscillator having an oscillator cavity length, L.sub.o, and defining an oscillator path and a multi-pass optical amplifier coupled with the oscillator to establish a combined optical cavity including the oscillator path, the combined cavity having a length, L.sub.combined, where L.sub.combined=(N+x)*L.sub.o, where “N” is an integer and “x” is a number between 0.4 and 0.6. The amplifier comprises a polarization discriminating optic inputting light traveling along a first beam path from the oscillator and having substantially a first linear polarization into the amplifier and outputting light having substantially a linear polarization orthogonal to the first polarization out of the amplifier along a second beam path.

A laser processing method of performing laser processing on a transparent material that is transparent to ultraviolet light by using a laser processing system includes: performing relative positioning of a transfer position of a transfer image and the transparent material in an optical axis direction of a pulse laser beam so that the transfer position is set at a position inside the transparent material at a predetermined depth ΔZsf from a surface of the transparent material in the optical axis direction; and irradiating the transparent material with the pulse laser beam having a pulse width of 1 ns to 100 ns inclusive and a beam diameter of 10 μm to 150 μm inclusive at the transfer position.

A gas laser device includes a shielding plate that is a first shielding member, and a shielding plate that is a second shielding member. The first shielding member includes a first opening, and a second opening. A laser beam that is to be propagated to discharge regions passes through the first opening. The laser beam that has taken a round trip through the discharge regions after passing through the first opening passes through the second opening. The second shielding plate faces the first shielding member the discharge regions located therebetween. The shielding plate includes an opening that is a third opening. The laser beam that has been propagated through the first opening and the discharge regions, and the laser beam that is to be propagated to the second opening through the discharge regions pass through the third opening. A plane shape of the third opening includes a rectilinear segment.