Heat-resistant flexible-film optical waveguides from fluorinated polyimides

Heat-resistant flexible-film optical waveguides were fabricated from fluori nated polyimides. These waveguides operated in single mode and had low opti cal loss (0.3 dB/cm) at a wavelength of 1.3 mu m for TE and TM polarization s. They also had good flexibility: The optical loss did not signifcantly ch ange above a minimum radius of curvature of less than 20 mm. The birefringe nce of 9 x 10(-5) between the TE and TM polarizations is 2 orders of magnit ude smaller than that for a waveguide upon a substrate. Moreover, these wav eguides had high thermal stability and moisture resistance: The optical los s and single-mode behavior changed little after heating the waveguides at 4 20 degrees C for 1 h or after their exposure to 85% relative humidity at 85 degrees C for more than 350 h. (C) 1999 Optical Society of America.