“…Another type of pressure sensor is based on cavity-length change, where the membrane with large size and small thickness is usually used as the reflective surface of the FP interferometer (FPI) for achieving a higher sensitivity. Membranes of different materials, such as silica [8,9], sapphire [10], diamond [11], silver [12], graphene [13,14] and polymer [15], have been used in building this FPI pressure sensors. Sensors made with silica and sapphire membranes have low sensitivities, however, they can be applied in a high temperature environment above 1000 • C [10].…”