To provide an optical glass having the optical characteristics of a high refractive index and low dispersion, and moreover, which makes it possible to further reduce devitrification and which can be stably obtained, and a preform and an optical element using the same. The optical glass comprises, expressed in cation % (mol %), 17.0% to 42.0% of P.sup.5+, 7.0% to 30.0% of Al.sup.3+, more than 0% to 22.0% of Mg.sup.2+, more than 0% to 25.0% Ca.sup.2+, more than 0% to 30.0% of Sr.sup.2+, more than 0% to 35.0% Ba.sup.2+, and expressed in anion % (mol %), a content ratio of F.sup.− of 37.0 to 64.0%, a content ratio of O.sup.2− of 36.0 to 63.0%, a refractive index (nd) of 1.48 to 1.58, and having an Abbe number (vd) of 70 to 88, and a liquidus temperature of 800° C. or less.

To provide an optical glass having the optical characteristics of a high refractive index and low dispersion, and moreover, which makes it possible to further reduce devitrification and which can be stably obtained, and a preform and an optical element using the same. The optical glass comprises, expressed in cation % (mol %), 17.0% to 42.0% of P.sup.5+, 7.0% to 30.0% of Al.sup.3+, more than 0% to 22.0% of Mg.sup.2+, more than 0% to 25.0% Ca.sup.2+, more than 0% to 30.0% of Sr.sup.2+, more than 0% to 35.0% Ba.sup.2+, and expressed in anion % (mol %), a content ratio of F.sup.− of 37.0 to 64.0%, a content ratio of O.sup.2− of 36.0 to 63.0%, a refractive index (nd) of 1.48 to 1.58, and having an Abbe number (vd) of 70 to 88, and a liquidus temperature of 800° C. or less.

Disclosed is fluorophosphate glasses for an active device, the fluorophosphate glasses including: a metaphosphate composition including Mg(PO.sub.3).sub.2 of about 20 mol % to about 60 mol %; a fluoride composition including BaF.sub.2 of about 20 mol % to about 60 mol % and CaF.sub.2 of about 0 mol % to about 40 mol %; and dopants including rare earth elements, in which there is an effect of increasing a carrier lifetime at a metastable state energy level that is stimulated-emitted due to an efficient energy transfer phenomenon by composition optimization of dopants (e.g. Er and Yb).

Disclosed is fluorophosphate glasses for an active device, the fluorophosphate glasses including: a metaphosphate composition including Mg(PO.sub.3).sub.2 of about 20 mol % to about 60 mol %; a fluoride composition including BaF.sub.2 of about 20 mol % to about 60 mol % and CaF.sub.2 of about 0 mol % to about 40 mol %; and dopants including rare earth elements, in which there is an effect of increasing a carrier lifetime at a metastable state energy level that is stimulated-emitted due to an efficient energy transfer phenomenon by composition optimization of dopants (e.g. Er and Yb).

A dental glass includes, in terms of oxide:phosphorus (P.sub.2O.sub.5) by greater than or equal to 40% by mass and less than or equal to 70% by mass; potassium (K.sub.2O) by greater than or equal to 20% by mass and less than or equal to 40% by mass; and calcium (CaO) by greater than or equal to 1% by mass and less than or equal to 20% by mass, wherein the dental glass does not substantially contain silicon and aluminum.

The disclosed fluorophosphate glasses for an active device include: a metaphosphate composition including Al(PO.sub.3).sub.3; a fluoride composition including BaF.sub.2 and SrF.sub.2; and a dopant composed of ErF.sub.3 and YbF.sub.3, and have thermal and mechanical properties to be able to be used as a glass base material for an active device (e.g., optical fiber laser), have a high emission cross-section characteristic, have a reinforced upconversion and downconversion emission characteristic, and have high sensitivity S in a cryogenic environment.

The disclosed fluorophosphate glasses for an active device include: a metaphosphate composition including Al(PO.sub.3).sub.3; a fluoride composition including BaF.sub.2 and SrF.sub.2; and a dopant composed of ErF.sub.3 and YbF.sub.3, and have thermal and mechanical properties to be able to be used as a glass base material for an active device (e.g., optical fiber laser), have a high emission cross-section characteristic, have a reinforced upconversion and downconversion emission characteristic, and have high sensitivity S in a cryogenic environment.

A dental glass includes: phosphorus; sodium and/or potassium; and calcium, wherein the dental glass contains, in terms of oxide, phosphorus (P.sub.2O.sub.5) by greater than or equal to 40% by mass and less than or equal to 70% by mass, sodium and/or potassium (Na.sub.2O, K.sub.2O) by greater than or equal to 20% by mass and less than or equal to 40% by mass, and calcium (CaO) by greater than or equal to 1% by mass and less than or equal to 20% by mass, and wherein the dental glass does not substantially contain silicon and aluminum.

The invention provides an optical glass having excellent precision molding performance and having a refractive index of 1.46-1.53 and an Abbe number of 77-84. The optical glass comprises the following components based on cations in the molar percentage: P.sup.5+: 10-35%, Al.sup.3+: 10-35%, Ba.sup.2+: 1-20%, Sr.sup.2+: 10-35%, Ca.sup.2+: 1-20%, Gd.sup.3+: 0-10%, and Na.sup.+: 0-10%; the ratio of Sr.sup.2+/(Gd.sup.3++Na.sup.+) being 1-30; anions comprising F.sup. and O.sup.2, wherein the ratio F.sup./P.sup.5+ of F.sup. content relative to the total molar percentage of anions to P.sup.5+ content relative to the total molar percentage of cations is 2.5 or more. The invention by rationally adjusting the proportions of the components, the molding performance of the optical glass is improved, and the problem that glass is broken and forms fogs during the molding process is solved, thereby the yield in manufacturing optical elements is improved.

The invention provides an optical glass having excellent precision molding performance and having a refractive index of 1.46-1.53 and an Abbe number of 77-84. The optical glass comprises the following components based on cations in the molar percentage: P.sup.5+: 10-35%, Al.sup.3+: 10-35%, Ba.sup.2+: 1-20%, Sr.sup.2+: 10-35%, Ca.sup.2+: 1-20%, Gd.sup.3+: 0-10%, and Na.sup.+: 0-10%; the ratio of Sr.sup.2+/(Gd.sup.3++Na.sup.+) being 1-30; anions comprising F.sup. and O.sup.2, wherein the ratio F.sup./P.sup.5+ of F.sup. content relative to the total molar percentage of anions to P.sup.5+ content relative to the total molar percentage of cations is 2.5 or more. The invention by rationally adjusting the proportions of the components, the molding performance of the optical glass is improved, and the problem that glass is broken and forms fogs during the molding process is solved, thereby the yield in manufacturing optical elements is improved.