A low-cost and reliable laser shutter interlock using a software-command interface

Abstract

A simple and low-cost laser interlock is presented that operates via software commands issued by an ESP32 microcontroller. The architecture of the device is constructed to ensure the laser output is shut off in the event of either an open circuit on the interlock signal line from the laser enclosure or loss of power to the device. Unintentional exposure to the laser beam is prevented by overruling local controls (such as a keypad), until both the enclosure is re-interlocked and the user actively intervenes. The device presented is designed to close the mechanical shutter of a Spectra-Physics Millennia Pro pump laser while it continues to operate internally. The hardware and coding are versatile enough that only minor edits to the code would be necessary to deploy the device on any instrument that receives software commands via a serial interface.