DPSS Green Laser Pointers
DPSS is an acronym for Diode Pumped Solid State and is used to categorize a type of laser. A DPSS laser has a solid state gain medium pumped by a diode light source. To understand what this mumble jumble means, let's dig deeper into how lasers work!
There are 3 basic components to a laser, a pump source, a gain medium, and an optical resonator. A laser will not operate if one of these components is missing. The pump source is an originating power source needed to excite the gain medium. A pump source can be in the form of an electric charge, a flash lamp or even light from another laser. The gain medium is the collection of atoms in its ground state waiting to be excited by the pump source. When atoms within the gain medium are excited, light or photons are emitted. The gain medium can be in the form of a gas, liquid or solid. The optical resonator is two mirrors (one reflective, and one semi-reflective) on opposite ends of the gain medium which allows light to bounce back and forth. Light builds up between the optical resonator and becomes the laser. To get an in-depth explanation of this, visit our website on how lasers work.
As we discussed above, a DPSS laser uses a diode as a pump source with a solid state gain medium. A perfect example of this is a green laser pointer. Below is a diagram of how a green laser pointer works along with a detailed explanation of each component and procedure.
1. Green laser pointers usually operate on 2 AAA batteries. The AAA batteries are used to power a laser diode. A diode is a device which converts electricity directly to a light source. In this case, the diode is an IRED or an Infra Red Emitting Diode with wavelength of 808nm.
2. The 808nm infrared light from the laser diode is used to pump a solid state Neodymium doped Yttrium Orthvanadate (Nd:YVO4) crystal. The resulting laser has a wavelength of 1064nm. As a green laser pointer has a wavelength of 532nm, there are still additional steps involved in producing a green laser beam.
3. The 1064nm wavelength light must now pass through a Potassium Titanium Oxide Phosphate (KTiOPO4 ) or KTP crystal in a process called frequency doubling. By doubling the frequency of a laser, you actually reduce the laser wavelength by one half. The resulting light is a 532nm green laser beam!
4. The final step to producing a green laser pointer is the addition of collimation lenses.
In general, DPSS green laser pointers are around 20% - 30% efficient. That is, only 20-30% of the original power from the infrared laser diode actually becomes the green laser beam. 70-80% of the power is lost in steps 2-4 above. The rule of thumb is every time the laser enters a crystal or lens, power will lost. For example, if we started the process with a 200mW 808nm pump diode (in step 1), the resulting green laser pointer will be around 40mW to 60mW. The only method of increasing efficiency rates is to use high quality crystals accompanied with properly coated glass collimation lenses.
While we do not offer blue laser pointers at this time, DPSS blue laser pointers use a similar process discussed above. The 808nm infrared laser diode is used to pump a Neodymium Yttrium Vanadium Oxide (Nd:YVO4) crystal. The outcome is an infrared 946nm wavelength laser. When frequency doubled via a Lanthanum Boron Oxide or LBO crystal, the 946nm laser is reduced to a 473nm blue laser beam. As efficiency rates for blue laser pointers are only around 3%-5%, blue laser pointers are relatively weak in power. This also makes high power blue lasers very expensive.