Etalon structure

The invention discloses an etalon structure which comprises two substrates, a circular isolating block and an index-matching fluid of an etalon, wherein the side face of the circular isolating block is provided with a small hole; reflecting films and antireflection films are plated on the two substrates partially; and an optical cement or deepened optical cement circular isolating block is arranged between the two substrates, the index-matching fluid is injected into a cavity from a side wall hole and then the side wall hole is solidified and packaged by use of glues. An FSR (free spectral range) value of the etalon can be achieved by changing a refractive index via adjusting the index-matching fluid. According to different FSR value requirements, different index-matching fluids can be prepared. The etalon structure is easily adjusted, conveniently processed and easily controlled and is suitable for volume production.