A spectral feature selection apparatus includes a dispersive optical element arranged to interact with a pulsed light beam; three or more refractive optical elements arranged in a path of the pulsed light beam between the dispersive optical element and a pulsed optical source; and one or more actuation systems, each actuation system associated with a refractive optical element and configured to rotate the associated refractive optical element to thereby adjust a spectral feature of the pulsed light beam. At least one of the actuation systems is a rapid actuation system that includes a rapid actuator configured to rotate its associated refractive optical element about a rotation axis. The rapid actuator includes a rotary stepper motor having a rotation shaft that rotates about a shaft axis that is parallel with the rotation axis of the associated refractive optical element.

A pulse width extension device includes a first delay optical system having a first loop optical path formed on a first plane and configured by a first beam splitter and a plurality of first concave mirrors, a second delay optical system having a second loop optical path formed on a second plane parallel to and different from the first plane and configured by a second beam splitter and a plurality of second concave mirrors, and a first beam rotation mechanism arranged on an optical path between the first delay optical system and the second delay optical system and configured to rotate a beam of pulse laser light having passed through the first delay optical system so that a longitudinal direction of a beam cross-sectional shape of the pulse laser light traveling on the second loop optical path is perpendicular to the second plane.

A laser apparatus may include: a quantum cascade laser outputting, based on a supplied current, laser light at an oscillation start timing when a first delay time elapses from a current rising timing of the supplied current: an amplifier disposed in a laser light optical path, and selectively amplifying light of a predetermined wavelength to output the amplified laser light to a chamber including a plasma generation region into which a target is fed; and a laser controller controlling a third delay time, from an output timing of a laser output instruction to the current rising timing, to cause a laser light wavelength to be equal to the predetermined wavelength at an aimed timing when a second delay time elapses from the oscillation start timing, based on oscillation parameters including the first delay time, a supplied current waveform, and a device temperature of the quantum cascade laser.

A laser system for amplifying laser light generated from a laser light source and emitting the laser light includes an optical element in an optical path of the laser light and transmits the laser light, a control device to control power to be supplied to the laser system, an imager to capture an image of the optical element, and an image processing circuitry to process the image of the optical element captured by the imager. The image processing circuitry in which reference images of the optical element corresponding to power information relating to the power are prepared in advance includes a comparison unit to compare a captured image of the optical element captured by the imager with a reference image selected by a reference image selection unit, the reference image corresponding to the power information at a time of image capturing by the imager.

A laser apparatus may include a beam splitter configured to split a pulse laser beam into a first beam path and a second beam path, an optical sensor provided in the first beam path, an amplifier including an amplification region provided in the second beam path and being configured to amplify and emit the pulse laser beam incident thereon along the second beam path, a wavefront controller provided in the second beam path between the beam splitter and the amplifier, and a processor configured to receive an output signal from the optical sensor and transmit a control signal to the wavefront controller.

A laser system including: A. a laser apparatus configured to output a pulse laser beam; B. an optical pulse stretcher including a delay optical path for expanding a pulse width of the pulse laser beam; and C. a phase optical element included in the delay optical path and having a function of spatially and randomly shifting a phase of the pulse laser beam. The phase optical element includes a plurality of types of cells providing different amounts of phase shift to the pulse laser beam and arranged irregularly in any direction.

A light beam measurement device includes: a polarization measurement unit including a first measurement beam splitter provided on an optical path of a laser beam and configured to measure a polarization state of the laser beam having been partially reflected by the first measurement beam splitter; a beam profile measurement unit including a second measurement beam splitter provided on the optical path of the laser beam and configured to measure a beam profile of the laser beam having been partially reflected by the second measurement beam splitter; and a laser beam-directional stability measurement unit configured to measure a stability in a traveling direction of the laser beam, while the first measurement beam splitter and the second measurement beam splitter are made of a material containing CaF.sub.2.

A laser apparatus including an optical element made of a CaF.sub.2 crystal and configured to transmit an ultraviolet laser beam obliquely incident on one surface of the optical element, the electric field axis of the P-polarized component of the laser beam propagating through the optical element coinciding with one axis contained in <111> of the CaF.sub.2 crystal, with the P-polarized component defined with respect to the one surface. A method for manufacturing an optical element, the method including causing a seed CaF.sub.2 crystal to undergo crystal growth along one axis contained in <111> to form an ingot, setting a cutting axis to be an axis inclining by an angle within 14.18±5° with respect to the crystal growth direction toward the direction of another axis contained in <111>, which differs from the crystal growth direction, and cutting the ingot along a plane perpendicular to the cutting axis.

A method of manufacturing a semiconductor includes generating plasma in an amplifying tube using gas as a gain medium; detecting a state of the plasma generated in the amplifying tube; determining a virtual laser gain based on the detected state of the plasma; controlling the state of the plasma such that the virtual laser gain is within a target range; and manufacturing the semiconductor device including performing an exposure process on a substrate using a laser beam output from the amplifying tube adjusted to have the virtual laser gain within the target range.

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.