Coupling ratio control of polymeric waveguide couplers by bending
Directional couplers are successfully fabricated on acrylic substrates using polymers synthesised from deuterated meth-acrylate and deuterated fluoromethacrylate monomers. The excess loss of a 50 mm long coupler is about 0-7 dB including waveguide and fibre coupling losses. A novel method is proposed for tuning the coupling ratio. By bending the coupler, high precision control of within 1% is attained without optical polarisation dependence.