A review of the status of research and development on direct modulation of semiconduc-tor lasers is presented. Basic theory based on conventional rate equations, dynamics of laser output involving resonance like phenomena, a damping relaxation oscillation and suppression of the oscillation, and spectrum behavior are included. New features appeared in the direct modulation of transverse mode stabilized injection lasers are given. The general problems likely to be encountered in high speed pulse modulation for opti-cal fibre transmissions are also discussed.
The dispersion characteristic of the magnetostatic surface wave propagating through periodic magnetic-structures has been analyzed by using a Rayleigh assumption which is well known as one of the approximation techniques, where-in a YIG film wave guide with periodic circuits of three different types are considered: One is a wave guide which consists of a YIG film with corrugation grooved against one of the faces, whilst the others are a corrugated YIG film with a metal plate placed against one of the faces and a YIG film backed by a corrugated metal plate. The Brillouin diagrams, close to the intersection point (ω, β) of m=0 and m=-1 space harmonics, have been evaluated numerically for the case of small modulation indexes of cor-rugation. The stop band frequency was found to be several tens of mega-hertz for a modulation index of the order of a few hundredths Moreover, the phase matching condition of Bragg type was not valid for the case of nonreciprocal propagation of the magnetostatic surface wave, but, is given by the relation: β_??_1.5π/d.