We propose a new method of phase matching in nonlinear waveguides, using th
e higher-order waveguide mode as an intermediary for efficient second-harmo
nic or difference-frequency generation, and show that high conversion effic
iencies can be achieved with this scheme. (C) 2000 Optical Society of Ameri
ca. OCIS codes: 230.7370, 190.2620, 190.4390, 030.1640.