# Laser Pointer FAQ



## clearlove (Dec 1, 2017)

What is the difference between red and green laser pointer? 1.Wavelength difference. Red laser wavelength is between 635nm to 780nm. Green laser wavelength is 515nm, 520nm and 532nm. 2.Different light emitting mode. Red laser pointer emit light directly from laser diode, without extract devices. It emits bright light directly from red laser diode. 532nm green laser light is emitting from 808nm laser diode pump crystal. Why violet laser pointer light spot is very weak? According to the principle of lasers, in case of same power, the shorter wavelength laser pointer can emit brighter light than longer wavelength one. However, the perspective of 532nm wavelength light is more easily absorbed and more sensitive, light emitting from 405nm violet laser looks much weaker to human eyes. Why red laser beam is not as visible as green laser? Shorter wavelength laser has great loss in the atmosphere, thus green laser is more easily visible than red laser beam. Green laser light is more easily absorbed by dust in the air, green laser pointer is more easily reflective, and thus beam of green laser pointer is much more visible than red laser pointer. How long can green laser pointer can be lighted? The continuous lighting time of green laser pointers will vary depending on output power. Portable green laser can be lighted within 10 seconds under formal working temperature of 298K. If operating time is extended, the output power might be increased in attenuation, until not bright. Long operation time can destroy laser diode and crystal, or even burn out laser diode. Industrial alignment laser can be operated 24 hours continuously a day under room temperature and correct cooling system. The portion of alignment laser should be fixed in operation. Why laser diode and crystal of laser pointer can be easily burnt out? Long working hours is a key point which can cause laser diode burnt out. Due to long working hours, laser temperature increases with the increase of working hours, resulting in damage to the laser diode and crystal. When laser pointers require preheating? Laser pointer crystal is composed of yttrium vanadate crystals (YVO4), of which yttrium vanadate crystals are very sensitive to temperature, stable operating temperature at 293K - 303K, yttrium vanadate crystals stimulate operating temperature 293K. When the outside temperature is below 293K, yttrium vanadate crystal would be difficult to start. The lower the ambient temperature, the longer startup time will be spent on laser pointers. Why green laser pointer power will decay at a high temperature? Green laser pointer consists of 808nm laser diode and crystal, operating temperature of 298K, laser diode wavelength 808nm±2nm. When operating temperature is up 298K, laser diode wavelength will be shorter, thus laser power reduces along with wavelength change. The longer the operation time of laser pointer, the higher the temperature and the power will also decay. How much is laser pointer speed? Ordinary light propagation speed in the air is 300,000 meters per second. Laser propagation velocity in air is 300,000,000 meters per second. Laser propagation velocity in the air is 3/4 of vacuum. Laser propagation velocity in the glass is 2/3 of vacuum.


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## Accutronitis (Dec 5, 2017)

The speed of light in vacuum is 299,792,458 meters per second


The speed of light in air is about 299,700,000 meters per second


For visible light the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200,000,000 meters per second


But in an experiment by researchers at NEC developed a device that fired a laser pulse into a glass chamber filled with a vapor of cesium atoms, The laser light through the cesium vapor seemed to travel 310 times the distance it would have covered if the chamber had contained a vacuum. But doubts have been raised...


*[FONT=q_serif]But all laser beams are light and travel at the speed of light...[/FONT]*


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## CobraMan (Dec 6, 2017)

Just in case you are not already aware of/familiar with the website - check this one out: https://laserpointerforums.com/

Enjoy,
Tim


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## Accutronitis (Dec 6, 2017)

I'm not really into pointers (cat toys), I'm high power or nothing, If I point my laser at something and it doesn't burst into flames then it needs more power ! lol


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## FRITZHID (Dec 27, 2017)

Then there's the laser god's handbook...

http://www.repairfaq.org/sam/lasersam.htm

Most coherent laser manual out there!


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