Athermal conditions of optical elements and properties of optical materials
Abstract
In precision interferometry, as in interferometry for the determination of the refractive index of gas, the temperature dependence of optical path length of a transparent window is important. The temperature coefficients of optical path length of transparent windows are calculated for various optical materials in vacuum and several gases. The conditions where temperature coefficients are equal to zero are studied using generalized athermal conditions. As the result, it is found that LHG-10 is good for normal incident window in air and for Brewster window in vacuum, and athermal glass 3036 and another athermal glass 3038 are good for normal incident window in vacuum and Brewster window in air, respectively. For these windows the temperature coefficients normalized by the thickness of the window are of the order of 10 to the -7 power C, so that temperature tolerance of the order of 0.1C can be allowed in the interferometric system which has the solution of 10 to the -4 power lambda. In the last stage, the athermal condition independent of incident angle is checked with material constants of optical materials and gases and it is found that the condition is, at this moment, far from that required. Material meeting these conditions should be developed.
- Publication:
-
Hokkaido University Faculty Engineering Bulletin
- Pub Date:
- October 1985
- Bibcode:
- 1985HUFEB.........M
- Keywords:
-
- Interferometry;
- Optical Materials;
- Optical Paths;
- Optical Properties;
- Refractivity;
- Temperature Dependence;
- Temperature Gradients;
- Thermodynamic Properties;
- Transparence;
- Windows (Apertures);
- Brewster Angle;
- Glass;
- Incidence;
- Vacuum Effects;
- Optics