Monolithic, linear glass polarizer and attenuator
The disclosure is directed to an element that is capable of acting as both an optical polarizer and an optical attenuator, thus integrating both functions into a single element. The element comprises a monolithic or one piece glass polarizer (herein also call the “substrate”), a multilayer “light attenuation or light attenuating” (“LA”) coating that has been optimized for use at selected wavelengths and attenuations deposited on at least one polarizer facial surface, and a multilayer anti-reflective (AR) coating on top of the LA coating. The disclosure is further directed to an integrated optical isolator/attenuator comprising a first and a second polarizing elements and a Faraday rotator for rotating light positioned after the first polarizing element and before the second polarizing element, the integrated optical isolator/attenuator both polarizing and attenuation a light beam from a light source.
1. A method for making an integrated monolithic linear polarizer/attenuator element comprising:
providing a monolithic linear glass polarizer containing elongated metallic polarizing particles therein;
depositing on at least one surface of the monolithic linear glass polarizer a multilayer inorganic light attenuating (LA) coating comprising at least one silicon layer as a high refractive index material H and at least one layer of an oxide selected from the group consisting of metal and mixed metal oxides having a refractive index greater than 1.7 as low refractive index material L; and
depositing a multilayer anti-reflection (AR) coating on top of the multilayer inorganic light attenuating (LA) coating, the multilayer anti-reflection (AR) coating comprising at least one period H′L′ where H′ is a high refractive index material having an index of refraction greater than 1.7 and L′ is a low refractive index material having an index of refraction less than or equal to 1.7 to thereby form an integrated monolithic linear polarizer/attenuator element;
wherein during the deposition of the multilayer inorganic light attenuating (LA) coating and the multilayer anti-reflection (AR) layer, the temperature of the monolithic linear glass polarizer is below the temperature at which the elongated metallic polarizing particles will contract or respheroidize.
2. The method according to claim 1 , wherein the low refractive index material L is selected from the group consisting of ITO, Cr 2 O 3 , ZnO, Nb 2 O 3 and GeO 2 .
3. The method according to claim 2 , wherein at least one low refractive index material L has an index of refraction greater than 2.
4. The method according to claim 1 , wherein the multilayer inorganic light attenuating (LA) coating comprises an ITO layer having a thickness in the range of 250 nm to 600 nm, a Cr 2 O 3 layer having a thickness in the range of 20 nm to 200 nm and at least one silicon layer having a thickness in the range of 20 nm to 700 nm; and
the multilayer anti-reflection (AR) coating comprises a plurality of the periods H′L′, where H′ is selected from the group consisting of ZrO 2 , HfO 2 , Ta 2 O 5 , Nb 2 O 5 , TiO 2 , Y 2 O 3 , Si 3 N 4 , SrTiO 3 and WO 3 , and L′ is selected from the group consisting of SiO 2 , F-doped SiO 2 , and Al 3 O 3 , and fluorides MgF 2 , CaF 2 , BaF 2 , YbF 3 and YF 3 .