Abstract: A gas laser apparatus includes an enclosure, a window holder, a window, and a sealing member. The window holder further having an extending surface located on the side toward which reflected light travels, the reflected light being reflected off the window, the extending surface being continuous with the end surface and extending in a direction away from the window, the extending surface irradiated with the reflected light. A line is obtained by symmetrically folding back the optical axis of the reflected light at the position, on the extending surface, that is irradiated with the reflected light with respect to a reference line passing through the irradiated position and perpendicular to the extending surface. The line 602 extends across a normal to the window in the direction from the extending surface toward the window from the side facing the outer circumference of the window toward the center axis of the window.

Abstract: A laser apparatus including an optical element made of a CaF2 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 CaF2 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 CaF2 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.

Abstract: A gas laser apparatus may include a chamber filled with a laser gas; a window provided in the chamber and through which a laser beam passes; an optical path tube connected to the chamber to surround a position of the window in the chamber; a heated gas supply port configured to supply a heated purge gas into a closed space including a space in the optical path tube; and an exhaust port configured to exhaust a gas in the closed space.

Abstract: A gas laser apparatus includes a chamber; a window provided in the chamber; an optical path tube connected to the chamber; a gas supply port that supplies a purge gas into the optical path tube; an exhaust port that exhausts a gas in the optical path tube; and a control unit, the exhaust port including a main exhaust port provided in the optical path tube, and an auxiliary exhaust port provided in the optical path tube upstream of a flow of the gas in the optical path tube with respect to positions of the window and the main exhaust port, the control unit causing the gas to be exhausted through the main exhaust port before a laser beam is emitted from the chamber and causing the gas to be exhausted through the auxiliary exhaust port in at least a partial period when the laser beam is emitted.

Abstract: A laser apparatus including an optical element made of a CaF2 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 CaF2 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 CaF2 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.

Abstract: A laser apparatus includes: an oscillator configured to output seed light; an amplifier including a laser chamber provided in an optical path of the seed light and a pair of discharge electrodes provided inside the laser chamber; and a transform optical system provided in the optical path of the seed light between the oscillator and the amplifier and configured to transform the seed light in a way that suppresses a decrease in purity of polarization of a laser beam that is outputted from the amplifier.