Embodiments relate to a glass composition which can allow for realizing beautiful bluish green colors therein even upon the use of a trace amount of a colorant such as Ti, Co, and Cr, securing high visible light transmittance suitable for window glass, and effectively reducing transmittance of solar heat radiation to help reduce a cooling load in buildings and vehicles.

A glass substrate for EUVL includes a first main surface having a rectangular shape; a second main surface having a rectangular shape on an opposite side to the first main surface; four end surfaces orthogonal to the first and second main surfaces; four first chamfered surfaces formed on boundaries between the first main surface and the end surfaces; and four second chamfered surfaces formed on boundaries between the second main surface and the end surfaces. The glass substrate for EUVL is formed of quartz glass containing TiO.sub.2. The end surfaces include fluorine (F) and an element (A) other than fluorine that forms a gas cluster with fluorine, and satisfy relations:

S1=∫.sub.0.sup.x=50[nm]{D1(x)−(a1x+b1)}dx>0.2  (1)

S2=∫.sub.0.sup.x=50[nm]{D2(x)−(a2x+b2)}dx>0.03  (2)

A glass has a low ratio of density ρ and refractive index n.sub.d. The glass has a refractive index n.sub.d in a range of 1.80 to 2.00, an internal transmission of at least 80% (450 nm, 10 mm), a dispersion v.sub.d of 19.0 to 27.0, and a ratio ρ/n.sub.d of <1.97.

A process for producing a glass body, the process including flowing oxygen gas from a burner in a furnace at a flow rate of greater than 12.0 standard liters per minute and flowing a precursor gas mixture from the burner. The process further including oxidizing the precursor gas mixture with the oxygen gas to form glass particles and depositing the glass particles on a collection cup to form the glass body.

An optical element reflects radiation, such as EUV radiation. The optical element includes a substrate with a surface to which a reflective coating is applied. The substrate has at least one channel through which a coolant can flow. The substrate is formed from fused silica, such as titanium-doped fused silica, or a glass ceramic. The channel has a length of at least 10 cm below the surface to which the reflective coating is applied. The cross-sectional area of the channel varies by no more than +/−20% over the length of the channel.

Provided is a method for producing a glass substrate that can reduce the dimensional change during heat treatment while avoiding shortening of facilities' service lives. A method for producing a glass substrate includes melting and forming a glass raw material to produce a glass substrate having a strain point of 690 to 750° C., wherein an average cooling rate in a temperature range from (an annealing point plus 150° C.) to (the annealing point minus 200° C.) in a cooling process during the forming is adjusted to 100 to 400° C./min to obtain the glass substrate having a degree of thermal contraction of 15 ppm or less when subjected to a heat treatment at 500° C. for an hour.

A silica-titania glass substrate comprising: (i) a composition comprising 5 weight percent to 10 weight percent TiO.sub.2; (ii) a coefficient of thermal expansion (CTE) at 20° C. in a range from −45 ppb/K to +20 ppb/K; (iii) a crossover temperature (Tzc) in a range from 10° C. to 50° C.; (iv) a slope of CTE at 20° C. in a range from 1.20 ppb/K.sup.2 to 1.75 ppb/K.sup.2; (v) a refractive index variation of less than 140 ppm; and (vi) 600 ppm OH group concentration or greater. The substrate can have a mass of 1 kg or greater and less than 0.05 gas inclusions per cubic inch via a method comprising (i) forming the substrate from soot particles comprising SiO.sub.2 and TiO.sub.2, and (ii) subjecting the substrate to an environment having an elevated temperature and an elevated pressure for a period of time until the substrate comprises less than 0.05 gas inclusions per cubic inch.

A glass composition comprising: Al.sub.2O.sub.3, ZnO, and SiO.sub.2; TiO.sub.2, in the amount of at least 10 mol % and not greater than 20 mol %; and alkaline metal oxide selected from the group consisting of MgO, CaO, SrO, BaO, or any combination thereof, such that the molar sum of MgO, CaO, SrO, BaO, and ZnO, in the amount in the glass composition is least 20 mol % and not greater than 35 mol %, and such that: the amount of BaO is 0 to 10 mol %; the amount of MgO is 0 to 10 mol %
the amount of CaO is 0 to 10 mol %, and the molar sum of CaO and MgO in the glass composition is less than 12.5 mol %; and rare earth metal oxides (ΣRE.sub.mO.sub.n), in the amount of at least 1.5 mol % and not greater than 10 mol %; alkali metal oxides (ΣAlk.sub.2O), in the amount of greater than or equal to 0 mol % and less than or equal to 5 mol %; and not greater than 5 mol % of other components; and wherein −5 mol %≤Al.sub.2O.sub.3 (mol %)−1.5 ΣRE.sub.mO.sub.n (mol %)−ΣAlk.sub.2O (mol %)≤+5 mol %.

Glasses containing silicon dioxide (SiO.sub.2) and/or boron oxide (B.sub.2O.sub.3) as glass formers and having a refractive index n.sub.d of greater than or equal to 1.80, as measured at 587.56 nm, a density of less than or equal to 5.5 g/cm.sup.3, as measured at 25° C., and a high transmittance to, particularly to blue light, are provided. Optionally, the glasses may be characterized by a high transmittance in the visible and near-ultraviolet (near-UV) range of the electromagnetic spectrum and/or good glass forming ability.

In order to reduce the degree of relaxation after an optical substrate has been compacted, in particular after a longer period, substrates (51) or reflective optical elements (50), in particular for EUV lithography, with substrates (51) of this type, are proposed. These substrates (51), which have a surface region (511) with a reflective coating (54), are characterised in that, at least near to the surface region (511), the titanium-doped quartz glass has a proportion of Si—O—O—Si bonds of at least 1*10.sup.16/cm.sup.3 and/or a proportion of Si—Si bonds of at least 1*10.sup.16/cm.sup.3 or, along a notional line (513) perpendicular to the surface region (511), over a length (517) of 500 nm or more, a hydrogen content of more than 5×10.sup.18 molecules/cm.sup.3.