An EUV collector mirror has a reflection surface (16) to reflect usable EUV light which impinges on the reflection surface (16) from a source region (17) to a subsequent EUV optics. The reflection surface (16) carries a pump light grating structure (19) configured to retroreflect pump light (22) which impinges upon the pump light grating structure (19) from the source region (17) back to the source region (17). The pump light (22) has a wavelength deviating from the wavelength of the usable EUV light. Such EUV collector mirror enables a high conversion efficiency between the energy of pump light of a laser discharged produced plasma (LDPP) EUV light source on the one hand and the resulting usable EUV energy on the other.

The present disclosure relates to a photolithography radiation source having an angled primary laser, and an associated method of formation. In some embodiments, the photolithography radiation source has a fuel droplet generator that provides fuel droplets to a source vessel along a first trajectory. A primary laser is configured to generate a primary laser beam along a second trajectory that intersects the first trajectory. The primary laser beam is configured to ignite a plasma from the plurality of fuel droplets that emits radiation. A collector mirror is configured to focus the radiation to an exit aperture of the source vessel. The primary laser beam does not intersect the exit aperture.

A reflective imaging optical system which forms, on a second plane, an image of a pattern arranged on a first plane and illuminated with light from an illumination optical system includes a plurality of reflecting mirrors including first and second reflecting mirrors by which the light reflected by the first plane is reflected first, second, respectively. An area on the first plane illuminated with the light from the illumination optical system is an illumination objective area, the illumination objective area is positioned on a predetermined side of an optical axis of the reflecting mirrors, and reflection areas of the first and second reflecting mirrors are positioned on the predetermined side of the optical axis of the reflecting mirrors; and the first and second reflecting mirrors are arranged so that an optical path of the light from the illumination optical system is positioned between the first and second reflecting mirrors.

A reflective EUV optic such as a collector mirror configured as an array of facets that are spaced apart to form respective gaps between adjacent facets. The gaps are used as inlets for gas flow across one of the facets such that flow is introduced parallel to the optic surface. The facets can be made with offsets such that loss of reflective area of the EUV optic can be minimized. The gas facilitates removal of target material from the surface of the facets.

A laser device for dentistry has a body, a light source group, and a light guiding pipe. The body has an outer casing, an operating module, and a controlling module. The light source group is disposed in the body and has multiple light-emitting elements, a reflector, a collimating lens, and a focusing lens. Each light-emitting element is a laser diode, is disposed at a connecting portion of the body and is electrically connected to the controlling module. The reflector is mounted around the light-emitting elements. The collimating lens is disposed on a side of the reflector away from the light-emitting elements. The focusing lens is disposed on a side of the collimating lens away from the reflector. The light guiding pipe is detachably connected to the connecting portion of the body and is located on a front side of the light source group.

An imaging EUV optical unit serves images an object field into an image field. The imaging optical unit has a plurality of mirrors for guiding EUV imaging light along an imaging beam path. The plurality of the mirrors includes at least two normal incidence mirrors and at least one grazing incidence mirror. The last two mirrors in the imaging beam path are normal incidence mirrors and lack an imaging light passage opening. A reflection surface of an antepenultimate mirror in the imaging beam path faces the last mirror in the imaging beam path. This EUV optical unit can have improved usability for an EUV projection exposure apparatus.