Your First Green Laser

What is a Green Laser?

Green lasers work slightly differently from your standard ‘keyring’ low powered red pointers that you can pick up for less than a £1. Green lasers are DPSS lasers. DPSS stands for Diode-Pumped Solid State. In a nutshell, this means the green laser light is made from another frequency of light first, rather than just producing green light straight away.

Now let's get the physics out of the way:
Green DPSS lasers work by having a higher powered Infra-red laser diode which emits 808nm light. This is said to ‘pump’ light into a crystal. Usually the crystal is a neodymium doped yttrium orthvanadate (Nd:YVO4) crystal which produces 1064 nm wavelength light. This is then frequency doubled using a nonlinear optical process in a KTP crystal, producing 532 nm light. Green DPSS lasers are usually around 20% efficient, although some lasers have been reported to be 35% efficient. In other words, a green DPSS laser using a 2.5 W pump diode would be expected to output around 500 mW of 532 nm light.

So now you know how they work, which one should you buy?

Typically, most first time buyers, as with anything, don’t have the money to commit to a top of the range super high powered laser. So we tend to start off on a fairly low to mid powered laser.

DealExtreme is a fantastic place to buy a cheap low/mid spec’d laser, making it ideal for first time buyers. All products are free shipping (which take about 10-14 days typically to arrive).

There are better shops to buy lasers from out there, e.g. you can’t go wrong with anything from Nova Lasers. But the prices are higher, as you will receive a high quality laser with excellent specifications and a decent warranty. All lasers I suggest for first time buyers will be from DealExtreme, as they offer the best value for money.

Now, several factors will affect which model you wish to purchase:

Do you have a preference for rechargeables?
What style of battery? AA / AAA / CR123A / CR2
If you chose rechargeables, do you have the right charger?

Pen style – small and compact, but have short duty cycles, as only limited amounts of heat can be dissipated. These lasers tend to take single use AAA or AA batteries

Flashlight style – usually a bit bulkier, the advantage of this is that they can operate with a higher duty cycle. These are most likely to take rechargeable batteries such as lithium 3.6V CR123A’s, or CR2 type.

What’s a Duty Cycle?
Put simply a duty cycle is the time you can safely operate the laser before it heats up too much, possible damaging the laser unit, or artefacts in the beam, or mode hopping starts to occur. Typically 2 mins on, 1 min off etc. Usually the better heatsinking or cooling the diode assembly has, the longer it can be continuously operated. Large laser modules in big aluminium heatsinks can be operated at 100% duty cycle i.e. they can be switched on indefinitely. But this is not usually the case for portable lasers.

IR Filters
Personally I think too much of a fuss it made about IR filters, but they are nice to have, especially on higher powered models. Some people refuse to buy a low powered laser because it doesn’t have an IR filter, but I don’t think it’s too much of a problem. But anything less and 100mW of green should be fine without one. An IR filter blocks ‘stray’ unconverted infra-red light from the DPSS assembly. In large amount this can damage your eyes. But diverges very quickly and is minimal at low powered lasers.