Semiconductor optical device having an optical confinement structure

Claim 1

A planar semiconductor optical device for modulating an optical beam, comprising: a substrate of a semiconductor material doped to a first conductivity type and having upper and lower major surfaces; an active layer having an upper major surface and provided on said upper major surface of said substrate, said active layer having a quantum structure for confining carriers in at least one of three mutually perpendicular directions, such that discrete quantum levels appear in said quantum structure, said active layer being laterally defined by a side wall extending in a direction generally vertical to said upper major surface of said substrate; a contact layer of a semiconductor material doped to a second, opposite conductivity type and having upper and lower major surfaces and provided on said upper major surface of said active layer; an optical confinement region provided adjacent to said active layer in intimate contact with said side wall, said optical confinement region having a refractive index smaller than an effective refractive index of said active layer for confining the optical beam in said active layer; first electrode means provided on said upper major surface of said contact layer for biasing said active layer to induce a change in an optical property therein, said first electrode means being provided with a first passage for an optical beam such that said optical beam can pass through first electrode means freely in a direction substantially perpendicular to said upper major surface of said contact layer; and second electrode means provided on said lower major surface of said substrate for biasing said active layer together with said first electrode means.