Steering light into logic patterns with two-dimensional cascaded multimode waveguide is demonstrated. By employing the imaging properties of 2D multimode interference （MMI） and partial phase modulation method, the design ideas and the implementing methods of the 2^（2×2） bits type spatial logic steering are discussed; therefore the structure of logical pattern is proposed. Numerical simulation is carried out to verify the design in detail by using the beam propagation method. It is expected to realize logic coders by using the integrated optical methods and exploit their potential applications in the field of optical logic.
An optically activated optical switch based on suppression of mode interference （SMI） is presented. The imaging properties of multi-mode interference （MMI） section in the switch with Y-branch can be modified by a controlling light injection. The switch was simulated by finite difference beam propagation method （FD-BPM） and fabricated on GaAlAs/GaAs epitaxial materials. At the wavelength of 1.31 μm, the primary experiment showed an extinction ratio of about 8 dB with controlling light power density of 73.5 W/mm^2.
We present a 1 × 4 Y-branch digital optical switch in which S-bend variable optical attenuators are integrated. The S-bend waveguides, which are always introduced to connect the switch and the standard fiber array, are made use of and designed as variable optical attenuators. A compact device with low crosstalk and larger branching-angle is obtained. The device is fabricated on the thermo-optic polymer materials,and the performance of the device is measured. With an applied driving power of less than 200mW, the device has a low crosstalk of less than - 35dB at a wavelength of 1.55 μm.
