Fig. 1. Basic optical route of instrument

Fig. 2. MZ interference curves of different materials. (a) K9 glass; (b) YAG crystal; (c) RTP crystal

Fig. 3. Additional phase item in sample branch

Fig. 4. Phase-modulation to eliminate FP interference effect. (a) F and 2F signals; (b) ellipses drawn by two signals; (c) solved phase; (d) solved amplitude

Fig. 5. Monitoring curves of zero drift. (a) Constant temperature condition; (b) variable temperature condition

Fig. 6. Zero drift curves after installing thermal shield

Fig. 7. Modified MZ optical route to monitor zero drift

Fig. 8. Zero drifts in two detectors without samples. (a) Two zero drifts; (b) zero drift difference

Fig. 9. Raw test data of quartz glass sample. (a) MZ background interference; (b) MZ sample interference; (c) FP interference

Fig. 10. Data processing for quartz glass MZ interference results. (a) Sample interference ellipse curve; (b) background interference ellipse curve; (c) solution results of phase; (d) temperature-phase curve; (e) best polynomial fitting order

Fig. 11. Data processing for quartz glass FP interference results. (a) Extreme point search; (b) temperature-optical path curve; (c) best polynomial fitting order

Fig. 12. Thermal expansion coefficient of quartz glass

Fig. 13. Temperature coefficient of refractive index of quartz glass at 632.8 nm