The color wavelength of the laser pointer knowledge
Laser pointer, also known as laser pointer, pointer, etc., is a pen-shaped emitter designed to be portable, easy to hold in the hand, and processed into a laser module (diode). Common laser pointers include red (650-660nm), green (532nm), blue (445-450nm), and blue-violet (405nm). It is usually used by newspapers, teachers, and docents to project a point of light or a ray of light directed at an object.
A physical picture of a common laser pointer
Early laser pointers (HeNe) HeNe gas lasers produce a laser wavelength of 633nm, typically 1mW. The cheapest laser pointers use a deep red laser diode with a wavelength of nearly 670/650nm. Slightly more expensive with red, orange 635nm diodes. Other colors are also possible, with the green laser at 532 nm being the most common alternative. Later, an orange-yellow laser pointer with a wavelength of 593.5 nm appeared. In 2005, a 473nm blue laser pointer appeared, which was introduced in September. At the beginning of 2010, a blue-violet laser pointer with a wavelength of 405 nm appeared.
The brightness of the laser beam on the spot depends on the laser power, the reflectivity of the surface. For the same power, the spectrum of the human eye in the green region (wavelength 520-570nm) is most sensitive and appears to be brighter than other colors. The sensitivity of the wavelength of red or blue decreases.
A laser pointer that typically represents the output power of milliwatts (mW). In the United States, lasers are classified by the National Standards Institute and the Food and Drug Administration (FDA). Visible laser pointers (400-700nm) operate at less than 1mW of power, Class 2 or II, visible 1-5mW laser pointers, are Class 3A or IIIa. Class 3B or IIIb lasers produce 5 to 500 mW; Class 4 or 4 lasers produce more than 500mW. The U.S. FDA regulations state that "demonstration laser products" must meet applicable requirements for Class I, IIA, or IIIA devices. 
Measured laser map
Red and orange laser pointers
This is the simplest laser because there are red diodes. No more than one battery-powered laser diode. The first red laser pointer, released in the early 80s of the 20th century, sold for a few hundred dollars. Today, they are much smaller and generally cost very little. Diode-pumped solid-state (DPSS) red lasers at 671nm are common.
Yellow laser pointer
Yellow laser pointers are extremely rare in the market. DPSS technology is obtained by adding two laser beams with wavelengths of 1064 nm and 1342 nm through a nonlinear crystal. The complexity of the process makes the yellow laser pointer unstable and inefficient, with an output power of 1-10mW depending on the temperature, and a pattern jump if it is overheated or too cold. This is because the size of the laser pointer does not provide the required temperature stabilization and cooling parts. In addition, most 593.5nm laser pointers operate in pulsed mode to allow for the use of pump diodes with smaller size and power.
Green laser pointer
The nonlinear crystal is excited by an infrared laser with a wavelength of 808nm to produce 1064nm infrared light, and then 532nm green light is generated by frequency doubling, which belongs to solid-state lasers. Some green lasers operate in pulsed or quasi-continuous mode to reduce cooling problems and extend battery life. Green lasers, which do not require frequency doubling, have higher efficiency. At night, even low-power green light can be seen due to Rayleigh scattering of atmospheric molecules, and this laser pointer is often used by astronomy enthusiasts to point to stars and constellations. Green laser pointers can have a variety of output powers. The 5mW (IIIA) is the safest to use and is also visible in dim lighting, so no more power is required for pointing purposes.
Blue light laser pointer
Blue laser pointers such as a specific wavelength of 473 nm usually have the same infrastructure as green lasers. Many factories in 2006 began to produce blue laser modules, mass storage devices, these used laser pointers. This is the type of equipment that pumps the frequency doubling with semiconductors. They most often emit 473 nm, which is doubled by a frequency multiplied by a diode-pumped laser at 946 nm ND:YAG laser or yttrium neodymium vanadate crystals. The BBO crystal with high output power is used for KTP crystals as a lower power doubling.
Visible wavelength green laser pointer
Some manufacturers are selling indicators of parallel blue laser diodes measuring power over 1500 milliwatts. However, since the claimed power of the "laser pointer" product also includes infrared power (only in semiconductor pumping technology) is still in the beam (for reasons discussed below), the laser is still problematic on the basis of the DPSS-type elements of the more strict visual blue, and is usually not applicable. Due to the use of higher neodymium harmonics, the frequency doubling conversion efficiency is low, and the infrared power is a small fraction of the optimal configuration of the semiconductor pump module, and the conversion of a blue laser at 473 nm is typically 10-13%, which is about half of that typical of green lasers (20-30%).
The blue laser can also directly fabricate indium gallium nitride semiconductors, producing frequency-grabby blue light. There are blue laser diodes on the market (447±5 nm), and the device is a bright same violet laser diode with a power of less than 405 nm, because the longer wavelength is closer to the peak sensitivity of the human eye. The mass production of laser projectors for commercial equipment, such as laser diodes, has driven down prices. The use of popular high-power (1W) 447 nm indicators, which also have improved optical versions of better collimation and lower divergence, comparable to the use of these portable devices, has reduced the sensitivity of green lasers with the intention and cost of human harm.
