Alaskan
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A troll came in here and asked which laser goes the furthest, I took quite a bit of time answering him to have every thread he created today deleted, due to showing he was no doubt, 100% troll breathed.
Not to have my work go to waste, I'm reposting for the newbies. Sometimes I will answer a newbie I suspect might be a troll because the information could be useful to others new to the hobby, so I'm reposting my thoughts here. Was able to recapture the text by back arrowing my viewed web pages, fortunately:
Which laser can go a further distance?
They all can go the same distance, it's the power density at distance which matters, that is directly related to both power and divergence. In general, if you stick with DPSS lasers they will have decent divergence, diode lasers usually have poor divergence (compared to DPSS) unless relatively low power single mode, the beam is expanded, or you buy a beam expander for them. For what you stating you desire, the highest power DPSS laser you can find is probably going to give you what you want.
To sum up what I believe you are asking for, you are looking for a laser which has the brightest beam for the furthest distance. Now you have another variable to deal with and that is the sensitivity of the eye to different wavelengths. Compared to either violet, blue or red colors, DPSS green is going to be the brightest to the eye for the power. You can buy cheap 10 dollar (or less) 532nm green DPSS laser pointers off of ebay which will produce 30-100 mw of output (luck of the draw, same model can be low or high output, regardless of their claim they are 5mw, or less) and they advertise they can go a specific distance in km, but that is BS, the light doesn't just go a certain distance, it keeps on going forever until it is absorbed or stopped by something, but as the beam spreads it appears to disappear due to becoming too weak to see very well from particles in the air, or having traveled beyond the lower layers of the atmosphere which have lots of particles to reflect off of... otherwise you would never see any beam at all, not from the side, at any power level.
If you want a good laser pointer check out JetLasers, not cheap compared to those low power luck of the draw laser pointers, but quality and can be counted on to produce a guaranteed amount of power output at higher levels than those ebay lasers. There are other DPSS laser pointer manufacturers which also provide quality green DPSS laser pointers at good prices, perhaps even less than JL prices, but for a dependable quality laser pointer at good prices, my preference is JetLasers.
Another important thing I need to mention is that DPSS laser pointers are temperature sensitive, if too cold or warm (due to ambient temperature, or just using them too long) they commonly vary by 50%, or more, below their rated full power output. That's the draw back for DPSS lasers put into a small package we can casually afford, if you want high stability in a low divergence DPSS laser pointer you are going to pay a lot more for it, but they can be purchased from LaserGlow, if you live outside of the US, there are also some other countries they won't ship them to. Find a used LaserGlow 800mw Hercules 532nm laser pointer or a 1.4 watt 532nm pointer made by Optotronics and now you are cooking with gas. Optotronics is top of the line for beam specs and stability, but even their output power will vary. However, they produce a far narrower beam at lower divergence and higher power than any other 532nm green laser pointer ever made. I believe I am correct on that statement, if there is anyone else who produces something as good, please post, I'd like to know.
Optotronics RPL Portable Green Lasers
Regarding the sensitivity of the eye to different wavelengths, here are some rules of thumb, all relative to a 532 nm DPSS green beam and some of the more common laser diodes we can buy, although I shouldn't say 470 is common yet:
405 nm blue-violet: 1% as bright (Not UV, but not far from it).
450 nm blue: 10% as bright
465 nm blue: 14% as bright
470 nm blue: 17% as bright
520 nm green: 88% as bright
638 nm red: 10% as bright
650 nm red: 5% as bright
660 nm red: 2% as bright
670 nm red: 1% as bright (Not IR, but not far from it).
You can do your own calc's at this URL: http://lsrtools.1apps.com/relativebrightness
My opinion, just generalisations:
For a laser pointer, if you want the beam to be visible in the dark at 100mw or more, I'd stay with lasers between 638 and 450nm. Go to a shorter wavelength than 450 nm and the beam is very dim to non-existent, a longer wavelength above 638 nm same problem. You very well may see the beam from a 650 or 405 nm laser pointer in the dark at 50 mw or less, but it all depends upon how many particulates are in the air etc:
A few variables:
Not to have my work go to waste, I'm reposting for the newbies. Sometimes I will answer a newbie I suspect might be a troll because the information could be useful to others new to the hobby, so I'm reposting my thoughts here. Was able to recapture the text by back arrowing my viewed web pages, fortunately:
Which laser can go a further distance?
They all can go the same distance, it's the power density at distance which matters, that is directly related to both power and divergence. In general, if you stick with DPSS lasers they will have decent divergence, diode lasers usually have poor divergence (compared to DPSS) unless relatively low power single mode, the beam is expanded, or you buy a beam expander for them. For what you stating you desire, the highest power DPSS laser you can find is probably going to give you what you want.
To sum up what I believe you are asking for, you are looking for a laser which has the brightest beam for the furthest distance. Now you have another variable to deal with and that is the sensitivity of the eye to different wavelengths. Compared to either violet, blue or red colors, DPSS green is going to be the brightest to the eye for the power. You can buy cheap 10 dollar (or less) 532nm green DPSS laser pointers off of ebay which will produce 30-100 mw of output (luck of the draw, same model can be low or high output, regardless of their claim they are 5mw, or less) and they advertise they can go a specific distance in km, but that is BS, the light doesn't just go a certain distance, it keeps on going forever until it is absorbed or stopped by something, but as the beam spreads it appears to disappear due to becoming too weak to see very well from particles in the air, or having traveled beyond the lower layers of the atmosphere which have lots of particles to reflect off of... otherwise you would never see any beam at all, not from the side, at any power level.
If you want a good laser pointer check out JetLasers, not cheap compared to those low power luck of the draw laser pointers, but quality and can be counted on to produce a guaranteed amount of power output at higher levels than those ebay lasers. There are other DPSS laser pointer manufacturers which also provide quality green DPSS laser pointers at good prices, perhaps even less than JL prices, but for a dependable quality laser pointer at good prices, my preference is JetLasers.
Another important thing I need to mention is that DPSS laser pointers are temperature sensitive, if too cold or warm (due to ambient temperature, or just using them too long) they commonly vary by 50%, or more, below their rated full power output. That's the draw back for DPSS lasers put into a small package we can casually afford, if you want high stability in a low divergence DPSS laser pointer you are going to pay a lot more for it, but they can be purchased from LaserGlow, if you live outside of the US, there are also some other countries they won't ship them to. Find a used LaserGlow 800mw Hercules 532nm laser pointer or a 1.4 watt 532nm pointer made by Optotronics and now you are cooking with gas. Optotronics is top of the line for beam specs and stability, but even their output power will vary. However, they produce a far narrower beam at lower divergence and higher power than any other 532nm green laser pointer ever made. I believe I am correct on that statement, if there is anyone else who produces something as good, please post, I'd like to know.
Optotronics RPL Portable Green Lasers
Regarding the sensitivity of the eye to different wavelengths, here are some rules of thumb, all relative to a 532 nm DPSS green beam and some of the more common laser diodes we can buy, although I shouldn't say 470 is common yet:
405 nm blue-violet: 1% as bright (Not UV, but not far from it).
450 nm blue: 10% as bright
465 nm blue: 14% as bright
470 nm blue: 17% as bright
520 nm green: 88% as bright
638 nm red: 10% as bright
650 nm red: 5% as bright
660 nm red: 2% as bright
670 nm red: 1% as bright (Not IR, but not far from it).
You can do your own calc's at this URL: http://lsrtools.1apps.com/relativebrightness
My opinion, just generalisations:
For a laser pointer, if you want the beam to be visible in the dark at 100mw or more, I'd stay with lasers between 638 and 450nm. Go to a shorter wavelength than 450 nm and the beam is very dim to non-existent, a longer wavelength above 638 nm same problem. You very well may see the beam from a 650 or 405 nm laser pointer in the dark at 50 mw or less, but it all depends upon how many particulates are in the air etc:
A few variables:
The diameter of the beam, whether at infinity focus or not, how dark the room, the amount of particulates in the air and your own sensitivity to different wavelengths may give different results.
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