light activated silicon controlled rectifier (LASCR)
Light Activated Silicon Controlled Rectifiers (LASCR) are light activated thyristors(SCRs), Light Activated SCRs also known as Light Triggered Thyristor( LTT).
Once the light falling on the rectifier exceeds a certain threshold, the LASCR allows the current to pass in one direction.
In terms of construction, LASCRs consist of an anode, cathode and the control electrode, the gate. Functionally, the LASCR remains in its conducting state as long as light is incident on it. If the brightness of the incident light falls below a threshold value, the LASCR blocks the flow of current. LASCRs have the highest sensitivity when the gate is open. In addition, LASCRs can be triggered with a pulse on the gate and then operate comparably to conventional thyristors ( SCR). LASCRs are used in light-controlled devices and twilight switches.