Optical cross couplers based on wet-etch processing of benzocyclobutene polymer

In this paper, a characterization process of benzocyclobutene (BCB 4024-40) polymer and its realization into optical devices are described. By using the prism coupling technique, the polymer film thickness for various coating speed and the refractive index have been measured. Based on these results, the optical waveguides and couplers have been fabricated using the wet-chemical etch processing technique to take advantage of the photosensitive nature of the polymer. By adopting the multimode interference technique (MMI), the fabricated 2 × 2 optical cross couplers have been testified to demonstrate a maximum crosstalk of −17.81 dB and maximum loss of 3.37 dB.