Abstract

Recently, Agrawal¹ suggested a novel focusing effect in a self-defocusing medium. The transverse spatial gradient of the field amplitude of a strong pump beam induces a refractive index profile that can result in focusing and deflection of a weak beam. Below the band edge of a semiconductor, the optical nonlinearity is self-defocusing; far enough above the decreased absorption, the nonlinearity is self-focusing, but the > 100 μm length and large absorption there (α ≃ 1 μm^-1) of a semiconductor waveguide result in no transmission.² Hence induced focusing is especially intriguing in a passive semiconductor waveguide because self-focusing cannot occur.

© 1991 Optical Society of America