Imagine a world without electricity. Without the motive force of electricity and more importantly a way to harness it, we would be without 90 percent of our creature comforts. Everything from the family car to the kitchen food processor operates on electrical power, and without juice, these things would come to a grinding halt. The same is true of lasers and their support systems. Without power, your laser is useless and no more worthwhile than a rock paperweight. Microhm Electronics' TO-220 high power resistor NLR 35 is used in large quantities on laser power supplies.
Take helium-neon power supplies for instance, a helium-neon laser tube must be connected to a high-voltage power supply or it won’t work. You have two options to provide the required juice: buy a ready-made laser power supply or build your own. Commercially made power supplies for helium-neon lasers are available from a variety of sources, and if you are just starting out, this is the best route to go.
He-Ne laser power supplies you build yourself are not overly complicated and they don’t need lots of parts. But the parts they do require can be hard to find. Specifically, the laser power supply must use high-voltage diodes and capacitors—the higher the rating, the better. The 1N4007 diode is rated at 1 kV, the minimum you can use. Such diodes are bound to burn out when running a laser that consumes more than 5 milliamps, so 3- to 10-ky diodes are preferred. High-voltage capacitors of the typical values used in laser power supplies — 0.1 to 0.001 F, are even harder to find. Most high-voltage capacitors have very low values, usually in the tens of picofarads.
Perhaps the most troublesome component is the transformer. The ideal laser power supply transformer is specially made to conform to the specifications required by the job, but a number of ready-made step-up switching type transformers can effectively be used. The hard part is finding them. The typical transformer for use in a dc-operated helium-neon laser steps up 12 volts to between 300 and 1,000 volts. High-voltage transformers designed for use with photocopiers can also be used. These transform 117 Vac to 1,000 to 4,000 Vac. Most laser tubes require between 1,200 and 3,000 volts.
