LiNbO3TE-TM mode converter using collinear acoustooptic interaction

A highly efficient TE-TM mode conversion device utilizing the acoustooptic effect has been demonstrated. Mode conversion has been made by an acoustic surface wave propagating collinearly with an optical guided wave. The maximum mode conversion, although the fraction was restricted to 70 percent, has been obtained with an acoustic power of only 55 mW (electrical input 0.55 W). Effective interaction length of the present device is limited to 5 mm due to optical and/or acoustic inhomogeneity of the waveguides. For selecting TE and TM waves, a polarizer is constructed monolithically and the extinction ratio is improved by up to 21 dB. Performance characteristics of a tunable optical filter of this type of the mode conversion are also discussed.