Fig. 2: MEMS processes for the optomechanical geophone.
From: An optomechanical MEMS geophone with a 2.5 ng/Hz1/2 noise floor for oil/gas exploration
a MEMS process for the sensing element and hemispherical micromirror. b As-fabricated optomechanical F‒P microcavity comprising a fixed hemispherical micromirror and a movable mirror on the sensing element. c Diagram of the sensing element with a size of 10 mm. d Deviation of the beams of the sensing element in the MEMS process. e Finite element simulation of the sensing element with the first mode at 325 Hz and the second mode at 790 Hz. f Diagram of the hemispherical micromirror with a diameter of 700 μm and a depth of 350 μm. g Optical microscopy image of a hemispherical micromirror. h SEM images of the hemispherical micromirror at various etching times
