A laser diode driver is a configuration used to drive a laser diode. A laser diode is a semiconductor device made of two different materials. One a P-material, the other an N-material, sandwiched together. Forward electrical bias across the P-N junction causes the respective holes and electrons from opposite sides of the junction to combine giving off a photon in the process of each combination. The junction area’s surfaces (cavity) are to a mirror-like finish. They are an important part of modern-day optics. In this project, we are going to design a simple Laser diode driver circuit using an LM317T voltage regulator IC.
LM317 is a three-terminal voltage regulator IC, with a high output current value of 1.5A. The LM317 IC has many features such as current limiting, thermal protection, and safe operating area protection. It can also provide a float function for high voltage uses. If we disconnect the adjustable terminal still, LM317 will be helpful in overload protection.
Hardware Components
The following components are required to make Laser Diode Driver Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Breadboard | – | 1 |
| 2. | Connecting Wires | – | 1 |
| 3. | Battery | 9v | 1 |
| 4. | IC | LM317 | 1,1 |
| 5. | Laser Diode | – | 1 |
| 6. | Diode | 1N4007 | 1 |
| 7. | Potentiometer | 200 ohms | 1 |
| 8. | Resistor | 3.9 ohms | 1 |
| 9. | Electrolyte Capacitor | 10uF | 1 |
LM317 Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of LM317
Laser Diode Driver Circuit
Working Explanation
The heart of the circuit is an LM317 IC that acts as a current limiter. The circuit is using a 200 ohms variable resistor to adjust the output current. Since. a laser diode receives damage on the accidental reverse connection of the battery, therefore a 1N4007 diode saves the laser diode from this problem. The 10uF electrolytic capacitor smoothes the output of the LM317 IC.
A laser diode is a sensitive device due to which it is important to take care of it when interfacing it with the circuit. It is better, to first disconnect the power supply or battery from the driver circuit and short the pins of the 10uF capacitor before connecting the laser diode with the circuit.
Applications
- Laser Diode Drivers are used to control laser diode optical output while protecting the laser diode from overcurrent conditions.
- Laser diode drivers provide protection to the lasing element from conditions such as Voltage spikes & surges.
