It has three pins; two for connecting 5V and GND, and one for turning the laser on and off. The purpose of this laser diode tutorial is to provide the information necessary to create a long lifetime, stable laser diode system. You can see it the following drawing. If you buy a single laser diode as a standalone component, you need to set up a driver circuit that controls the current through the. ROHM refers to the pins of a three-pin package as pins 1, 2 and 3, clockwise when viewed from the top of the package (the side where the laser beam is emitted). This component is widely used in various applications, including but not limited to optical communications, barcode scanners, laser.