532nm and 520nm are two common wavelengths of green light. What is the difference between these two laser modules? Their green light is very similar, but the 520nm is more like grass green. The working principles of the 532nm and 520nm green lasers are also different. The 532nm laser is produced by the frequency doubling of the laser crystal. The 520nm laser is generated by a semiconductor laser diode. These two lasers have different spot modes. The 532nm laser is a TEM00 laser, and the beam quality is better.
532nm CW 4W DPSS Solid Laser High Output High Beam Quality.
Green: The brightest thing we have to offer the human eye!
Green light is perceived as the brightest light by the human eye! Thus, it makes sense that green lasers be used for applications in which the laser beam is meant to be observed by the naked eye. Using green cross-hairs and lines, we can position machines or parts; green dots show the doctor where the processing laser hits human tissue; in material processing, they show where material will be welded or separated.
Color sensitivity differs from person to person; however on a basic level, the 532 nm wavelength of the DPSS laser is perceived as a full and powerful green. The laser diodes currently available have a wavelength of 520 nm (i.e., a light blue streak that is perceived as colder).
Beam profile: Striking differences
If you continue to compare both technologies, the most striking differences can be found in the beam profile: Due to the underlying physics, the DPSS laser produces a uniform, round beam with a Gaussian-shaped power distribution and an M2 value of nearly 1.0. The semiconductor laser with its layer structure, however, emits an elliptical beam at a ratio of approximately 1:3. It is suited for making lines, and together with diffractive optical elements can generate diverse patterns. The DPSS laser remains the first choice for dot lasers – especially in the medical field.
Temperature range: Ice cold to hot
The first miniature DPSS lasers to enter the market had a very limited temperature range: values typically ranged between 10°C and 30°C or between 15°C and 40°C. The versions that are currently available range from -5°C to +50°C!
Laser diodes remain undefeated in our comparison:
Up to a power level of 50 mW, the 520 nm diodes offer a consistent operating temperature range of -20°C to +60°C.
The operating temperature applies to the laser source. If it is integrated into a housing, the additional heat produced in the housing must also be taken into consideration.
Power stability: Dependent upon heat generation
Heat generation significantly affects the power stability of the lasers: Miniature DPSS lasers are extremely temperature sensitive. With complex electronics, we are successful in stabilizing our FLEXPOINT® DPSS modules to power fluctuations of <5%. This requires DPSS lasers that are equipped with an additional photodiode by the manufacturer. This allows us to implement an effective control circuit to stabilize the optical power.
Power stabilization is unproblematic in modules with a directly-emitting laser diode: Monitoring diodes are integrated on a standard basis. In combination with the digital laser control developed by us, we can achieve power fluctuations of <2%.
Modulation behavior and Q-switch phenomenon
The digital modulation behavior and the analog power adjustment of miniature DPSS lasers are limited by the so-called Q-switch phenomenon: This is disruptive noise with very high peak intensities in the frequency range of 200 kHz to 2 MHz. In addition, another mode in the DPSS laser can develop, which results in a second output beam. This undesired effect occurs often at low power levels and, therefore, affects dimmable lasers. Both disruptive effects are very temperature dependent and often not reproducible. The maximum modulation frequencies of FLEXPOINT® DPSS laser modules are, therefore, limited to a few kHz and in some cases to less than 1 kHz.
Laser diodes of 520 nm do not exhibit the Q-switch phenomenon and can be modulated with >100 MHz depending on the control electronics. In simple laser modules, modulation frequencies with several hundred kHz to 2 MHz are common.
Dimensions: When size matters
If space is limited, you require laser diodes: The smallest available 520 nm laser diodes fit into a TO housing with a diameter of only 3.8 mm. The entire module, including control electronics, therefore, fits into a housing that has a diameter of 11.5 mm. It is possible to further miniaturize this module to just 6 mm! The housing length depends on the desired beam profile and the extent of the electronic controls.
The miniature DPSS lasers are largely available with a diameter of 10 mm or 12 mm. A few special versions have a reduced diameter of 5.6 mm. The housing length of DPSS lasers will always be larger than versions with a laser diode due to their complex design and the required beam shaping.
Laser diodes of 520 nm are currently available with an output power of up to 80 mW. Miniature DPSS lasers can achieve up to several hundred milliwatts.
The price of 520 nm laser diodes has been rapidly dropping since their market introduction. They are already less expensive than DPSS lasers with an output power of >10 mW. It can be assumed that the cost of green-emitting laser diodes will very soon match the cost of red-emitting laser diodes. Due to the electronic controls, which are much easier to handle than in DPSS lasers, the green laser diode is alrea