Amorphous fluoropolymer micromembrane for variable optical attenuation

In this paper, we report a cost-effective variable optical attenuator made by an amorphous fluoropolymer micromembrane. More passive optical components are made by polymer materials due to its easy fabrication processes. The deformable mirror consists of a 2.15 μm-thick polymeric membrane and is actuated by electrostatic force from an electrode underneath it. The polymer membrane roughness is less than 10 nm. The Young's modulus is about 9.98 GPa, which is about 20 times less than popular silicon material. The polymer deformable mirror is aligned with a dual fiber collimator in free-space configuration to perform three-dimensional light beam spoiling for light attenuation. The maximum displacement of the polymer micromembrane is 12 μm, which corresponding to 22 diopter optical power adjustment. The maximum attenuation is 33 dB with 0.22 dB/V resolution. The actuation voltage is 150 V and the power consumption is 125 μW. The 0.46 dB insertion loss is achieved at 1550 nm wavelength, including dual fiber collimators. There are photoresist pillars between the polymeric membrane and the bottom electrode to cause squeeze damping so that the response time is reduced to 1.2 ms. The polarization dependent loss is less than 0.25 dB. The wavelength dependent loss is 0.4 dB and 0.5 dB in the C band and L band, respectively.