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Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
Hi guys,
I have been looking into making a 445nm, or similar, laser for a gun sight. However I have read in scattered places, without citations unfortunately, that the very popular and easy to obtain Casio 445nm laser diodes will not even lase below 25mW.
I found one laser from a trusted vendor that is 5mW (at ThinkGeek) but that has a $300+ price tag just to take it apart and potentially break it.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
Weston wrote ...
Why can't you use a Casio diode at the lowest possible lasing threshold and then further attenuate the beam with a filter?
I'm hoping to minimize optics as the laser will take a LOT of abuse (12ga shotguns don't exactly have the best recoil and parts stress of the gun lots). Essentially the last thing I want is for a filter to break while in use and end up with a higher power beam. Also, I was asking for clarification about the actual lasing threshold for the casio diodes if I didn't make that clear enough.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
Weston wrote ...
A filter would be as simple as 2 cut plastic polarizers at any point in the beam path. Not much to go wrong with that.
I guess not, I'd have to get access to the school's laser lab to do a power test anyways, I'd probably be able to get some time to work on it and tweak it right.
Registered Member #2628
Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627
The crapio diodes (A-130/A-140/M-140) have a threshold current of about 150mA or so (-/+ 50ma diode to diode) and can well do those low powers, a diode can be had for ~40$.
Problem is, for gunsight use with those diodes is two things.
First, <50mw of 445nm still isn't very visable unless in the dark, in daylight or a well lit room you will not see the dot clearly if at all. This makes 405nm even less suitable, you will need much more power from it to even get close to 100mw of 445nm in terms of visability. so IMO, <25mw of 445nm, or any lower wavelenth such as 405nm, is absolutely useless for what you are trying to do anyways. (at that point, your dollarstore 5mw 650nm is brighter.)
Second is the beam profile of the crapios, even lasing at such a low threshold (which it will singlemode, rather then multimode at higher powers) will still result in fairly undesirable divegance. (in comparison to a 660nm (LPC-815) with a much nicer gaussian profile).
Thinkgeek a trusted vendor? LOL. A 300$ price tag is a complete rip-off for ANY 445nm laser.. you can find some lasers ~80$ that out 50mw-80mw, but you will need to look for ones that use the osram/opnex diode (3.8mm 450nm diode, single mode and better beam profile). And likewise for crapio diode lasers, the pricing is a bit higher, but not by much (DIY for instance)
In all I can't see why you would spend more then 100$ for this.
Im personally for the LPC-815 660nm diodes, cheap (can buy a new sled for ~7$), excellent beam profile and not much optics to go along with it so it will take abuse, a simple Ar coated 3 element lens will do you well. (and at the end of the day, 200mw of 660nm is still brighter then 50mw of 445nm)
But if you *really* must have blue, these diodes are probably better then the crapios, it will output the power range you are looking for, has a higher wavelenth so its more visable, and a single mode output with a nicer beam profile then the A-140s.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
Doomguy wrote ...
The crapio diodes (A-130/A-140/M-140) have a threshold current of about 150mA or so (-/+ 50ma diode to diode) and can well do those low powers, a diode can be had for ~40$.
Problem is, for gunsight use with those diodes is two things.
First, <50mw of 445nm still isn't very visable unless in the dark, in daylight or a well lit room you will not see the dot clearly if at all. This makes 405nm even less suitable, you will need much more power from it to even get close to 100mw of 445nm in terms of visability. so IMO, <25mw of 445nm, or any lower wavelenth such as 405nm, is absolutely useless for what you are trying to do anyways. (at that point, your dollarstore 5mw 650nm is brighter.)
Second is the beam profile of the crapios, even lasing at such a low threshold (which it will singlemode, rather then multimode at higher powers) will still result in fairly undesirable divegance. (in comparison to a 660nm (LPC-815) with a much nicer gaussian profile).
Thinkgeek a trusted vendor? LOL. A 300$ price tag is a complete rip-off for ANY 445nm laser.. you can find some lasers ~80$ that out 50mw-80mw, but you will need to look for ones that use the osram/opnex diode (3.8mm 450nm diode, single mode and better beam profile). And likewise for crapio diode lasers, the pricing is a bit higher, but not by much (DIY for instance)
In all I can't see why you would spend more then 100$ for this.
Im personally for the LPC-815 660nm diodes, cheap (can buy a new sled for ~7$), excellent beam profile and not much optics to go along with it so it will take abuse, a simple Ar coated 3 element lens will do you well. (and at the end of the day, 200mw of 660nm is still brighter then 50mw of 445nm)
But if you *really* must have blue, these diodes are probably better then the crapios, it will output the power range you are looking for, has a higher wavelenth so its more visable, and a single mode output with a nicer beam profile then the A-140s.
Cheers.
This would be for for use in darker conditions (night home defense, etc). Also, I'm planning on actually having three lasers mounted, one 650nm (built into my sight already), one 532nm (weaver), and a ~445nm (weaver). Each has their own advantages (green during the day, red during dusk/nights, and blue at night). On top of that I thought it might be interesting, so if it turns out to not work well at all then I at least made a project out of it.
You also say that that diode has a longer wavelength, but the specifications I can find list the same wavelength?
Registered Member #2628
Joined: Fri Jan 15 2010, 12:23AM
Location:
Posts: 627
The wavelenth specification is often mislabeling, if I can find the thread on LPF regarding the spectrometer readout, that diode does have a higher wavelenth.
I see what your doing now, I suppose in a dark indoors it would be alright then.
Id worry about the green though, it better be made by a reputable company otherwise the DPSS will get knocked out of alignment or won't work in TEM00 after the first few shots.
Registered Member #902
Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042
Doomguy wrote ...
The wavelenth specification is often mislabeling, if I can find the thread on LPF regarding the spectrometer readout, that diode does have a higher wavelenth.
I see what your doing now, I suppose in a dark indoors it would be alright then.
Id worry about the green though, it better be made by a reputable company otherwise the DPSS will get knocked out of alignment or won't work in TEM00 after the first few shots.
The green laser is designed for guns. I'm only custom building the blue one.
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5mW 445nm laser?
