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.

A light emitting unit includes a light emitting sealed body and a voltage application circuit. The light emitting sealed body includes a container to which laser light for maintaining plasma is incident and from which light from the plasma is emitted, a first electrode which includes a first discharge portion, and a second electrode which includes a second discharge portion. An end portion of the first discharge portion has a shape in which a thickness is thinned as it goes toward the second discharge portion and an end surface of the second discharge portion extends along a plane perpendicular to an extending direction of the first discharge portion. The voltage application circuit controls a potential difference between the first electrode and the second electrode by adjusting a voltage applied to at least the first electrode.

A light emitting unit includes a light emitting sealed body and a voltage application circuit. The light emitting sealed body includes a container to which laser light for maintaining plasma is incident and from which light from the plasma is emitted, a first electrode which includes a first discharge portion, and a second electrode which includes a second discharge portion. An end portion of the first discharge portion has a shape in which a thickness is thinned as it goes toward the second discharge portion and an end surface of the second discharge portion extends along a plane perpendicular to an extending direction of the first discharge portion. The voltage application circuit controls a potential difference between the first electrode and the second electrode by adjusting a voltage applied to at least the first electrode.

A laser chamber of an excimer laser apparatus includes a container including a first member and a second member and configured to accommodate a laser gas in the container and a seal member disposed between two seal surfaces facing each other, a seal surface of the first member and a seal surface of the second member. A laser-gas-side surface of the seal member is made of fluorine-based rubber, and an atmosphere-side surface of the seal member is formed of a film configured to suppress atmosphere transmission.

A laser chamber of an excimer laser apparatus includes a container including a first member and a second member and configured to accommodate a laser gas in the container and a seal member disposed between two seal surfaces facing each other, a seal surface of the first member and a seal surface of the second member. A laser-gas-side surface of the seal member is made of fluorine-based rubber, and an atmosphere-side surface of the seal member is formed of a film configured to suppress atmosphere transmission.

Discharge electrodes include a cathode and an anode. The anode is disposed to face the cathode in a discharge direction perpendicular to a longitudinal direction of the cathode, and includes an electrode base 1, and a coating layer that covers a portion of a surface of the electrode base. First corners in a cross section perpendicular to the longitudinal direction connect first straight sections formed of first side surfaces that are side surfaces of the electrode base to a first curved section formed of a first discharge surface that is a discharge surface of the electrode base. The first corners are closer to the cathode in the discharge direction than second corners connecting second straight sections formed of second side surfaces that are side surfaces of the coating layer to a second curved section formed of a second discharge surface that is a discharge surface of the coating layer.

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 device includes a laser oscillator that generates a laser beam, condenser lens that condenses laser beam emitted from the laser oscillator, transmission fiber that includes at least core that transmits laser beam condensed by condenser lens, and cladding provided around core, and a lens driving unit that adjusts a position of condenser lens. The lens driving unit automatically adjusts the position of condenser lens to reduce light intensity of laser beam incident on cladding.

A laser device includes a laser oscillator that generates a laser beam, condenser lens that condenses laser beam emitted from the laser oscillator, transmission fiber that includes at least core that transmits laser beam condensed by condenser lens, and cladding provided around core, and a lens driving unit that adjusts a position of condenser lens. The lens driving unit automatically adjusts the position of condenser lens to reduce light intensity of laser beam incident on cladding.

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.