Surely, most of you have used a laser pointer at some point. Whether purchased at a dollar store, online or pet store, they're always fascinating and entertaining to play with. Even though laser diodes do not have the potential "pulse" power as a flashlamp laser, they do have many benefits. For example, where a high-powered flashlamp laser requires a high voltage source, capacitors, flashtubes, etc., laser diodes simply require a regulated current source and a heat sink. This means portability, control, hours of use on single battery charge, and a small size.
There are several different types of semiconductor diodes. I'll only be covering the simplest concept, however you can read more about these types here. Basically, a simple diode has an "n" junction and a "p" junction. These junctions are "pumped" electrically and produce light. Here's a visual representation:
The light produced from the n-p junctions is then "refined" with the use of crystal, then emitted. Diodes can produce a spectrum of wavelengths, depending on their configuration and physical components. Here's a photo of a DVD burner diode:
The semiconductor inside:
Hard to believe that little chip has the power to light matches and melt through tape. Imagine a larger version! Sadly, there are drawbacks; primarily heat and current issues. However, there are ways around this, such as large heat sinks and large LiPo battery packs supplying large amounts of current into a voltage/current regulator, i.e. the driver.
"Drivers" can range from as simple as a resistor, to as complex as a two story building in a power station. For lasers, these drivers primarily regulate current, since laser diodes are current hungry. Generally, this can be done with a simple semiconductor regulator such as LM317:
This semiconductor can be used to regulate a wide voltage/current by simply adding a resistor between the adjust and output.
Depending on what you're looking to accomplish with a laser, a diode-based device is generally the best way to go for some entertaining balloon-popping fun. In fact, it may be easier than you think to build one of these.
There is a very simple laser driver circuit consisting of just three parts, all available for under three dollars. The laser can put out about 150-200mW, easily enough to light matches and cut through tape. All you need is an LM317 voltage regulator, a 3- to 10-ohm resistor (depending on your diode), and a laser diode from a DVD burner. Here's a useful visual representation schematic:
Basically, voltage (ideal voltage) is connected to the regulator and ground, and the diode receives the regulated voltage/current, allowing it to operate smoothly at at maximum output. Here's a video tutorial!
- LASERS ARE VERY DANGEROUS. You should always wear eye protection OF THE RIGHT WAVELENGTH! This means if you are using a red laser, use RED GOGGLES, etc.
- If using a soldering iron, be careful! Soldering irons are hot.
- DON'T LET THE LASER OVERHEAT! The heat sink is there for a reason. Don't run the device without it.
- NEVER shine the laser at anything living/of value! It can do serious harm/damage!