In general, Photo Triac is used in power control of two-way triac rectifier. It is applied in circuit as level voltage ideal insulator that separate high & low voltage.  It is applied in home appliance and Solid State Relay for controlling isolation voltage. 
COSMO Photo Triac KMOC series are available for DIP, SMD type. KTLP series are available for SOP type.  The characteristics are available for 2 major functions, one is with Zero Crossing, another is without function of Zero Crossing function. Voltage are available for 400V , 600V and 800V…etc.