A system is provided for determining a binary codeword for a symbol representing a transform coefficient within transform units that divide up coding units in a High Efficiency Video Coding system. By making current blocking layer 19 at the light-emission end large enough that carriers flowing from a current injection region do not reach the light-emission end surface, the light intensity distribution in the near field at the light-emission end surface is strongly concentrated, allowing the horizontal divergence angle of an emerging laser beam to be enlarged. Since there is no offset of the lens at the time of shifting to the tracking, a track hold processing is carried out stably.