Integrated optics beam deflectors and systems

A waveguide mode filter comprising:

• a gallium arsenide substrate comprising layers of materials arranged to confine an electrical field in a relatively small thickness and wherein the said layers include:
• an N-doped gallium arsenide substrate;
• an N-doped aluminum gallium arsenide layer formed over said substrate;
• an N-doped gallium arsenide layer formed over the N-doped aluminum gallium arsenide layer;
• a P-doped gallium arsenide layer formed over the N-doped gallium arsenide layer;
• a P-doped aluminum gallium arsenide layer formed over the P-doped gallium arsenide layer;
• and
• a P-doped gallium arsenide layer formed over the P-doped aluminum gallium arsenide layer;
• and
• a necked waveguide having:
• a relatively broad input end which receives light and allows propagation of multi-mode light waves therethrough;
• a narrowed neck portion at which higher modes radiate outside the waveguide and only the modes which can propagate therethrough pass therethrough providing mode filtering;
• and
• a relatively broad output end.