How are Ballast Resistors Used in Laser Applications?

A ballast resistor is used to maintaining a constant flow of electrical current, irrespective of the variations in the applied voltage or rest of the circuit. These resistors consist of a resistive element, which increases with temperature.

Ballast resistors are used in fluorescent lamps, laser circuits and vapor lamps for compensating for fluctuations in line voltages.

In laser circuits, it is very important to have components between the actual voltage and the tube to stabilize the discharge and limit the current. Laser circuits which do not have a ballast resistor will produce a flashing or flickering discharge.

In the case of a helium-neon laser, the ballast is a simple resistance. The ballast in HeNe laser serves two purposes: stabilization and limiting the tube current. The ballast resistance that is commonly chosen for most HeNe lasers is around 75 KΩ.

References

• HeNe Laser Power Supplies- Sam’s Laser
• Properties of a coaxial cw CO₂ laser - Portland State University
• Ballast Resistor – McGraw Hill Science and Technology Dictionary