How hard would it be to mod these lasers?

[VW]

So I've odered a few sleds (DVD + HD-DVD) to turn into laser pointers.  As I'm a bit lazy, I was looking for a couple of DX lasers to use as the housing.  Initially I'm going to do a DVD laser in the form of a module, just to get into the swing of things.  But after that I want to build a few blue-ray pointers and wouldn't mind them in a propper casing.  

http://www.dealextreme.com/details.dx/sku.12342

This forst one I like because of the robust design, I already own a hulk so this is a design I could easilly settle with.  However the housing looks very tough and I have no idea how I would get in there.

http://www.dealextreme.com/details.dx/sku.7886

This one on the other hand I really like the look of as I already have access to the diode casing and from here looks removable too.  Also the lens cover would give me a load of options also.  Do you think it would be possible to make the driver small enough to fin in these?  What about batteries and power source? As I'd like to maximise their performance...

Any input would be apreciated...

 

[rkcstr]

They look like they'd be relatively easy to disassemble... but you'd probably have to do some fabrication to make sure everything fits right.  For the about the same amount you could go with Kenom's custom laser case which is specifically designed for our needs, minimal fabrication needed  

http://www.laserpointerforums.com/forums/YaBB.pl?num=1204788577

But, you may have to wait on it... I'm not sure of when exactly they'll be available.

 

[VW]

Wow, thanks. No that would be perfect, I want to try and build both heat sinking and non sinking models (eventually) so they would be perfect for no sinking.

 

[IgorT]

You are going to dissasemble those lasers, just for the body?

What driver are you going to use? The included ones will be pretty much useless to you, as they are often not regulated at all, and when they are the current is not really constant. They can only run an IR from the one battery inside there.

You would need Dr_Lava's flexdrive to drive a blue ray from a single Li-Ion..


Another problem will be, that these lasers are very inconsistent to how the module is mounted inside them. They green modules are often mounted in a way, that actualy prevents heatsinking. And an AixiZ module wouldn't just fit.


You would probably end up doing just as much work as if you were to use a $5-10 DX flashlight host, but you'll be paying much more, and wasting the green modules, which can be good sometimes.

 

[IgorT]

Wow, thanks. No that would be perfect, I want to try and build both heat sinking and non sinking models (eventually) so they would be perfect for no sinking.

What?!? Heat sinking and no sinking? I understand the first, but the second?!?

The kenbarrel is made in a way that the LD sticks directly into the head, so the entire head is a heatsink, and you don't need an AixiZ module. Otherwise, the AixiZ module itself is a heatsink, just not big enough for certain more powerfull LDs.


But what is the idea behind non-heatsinked lasers? Most cheap Chinese green lasers are like that, and often suck just because of that. They peak shortly and drop in power immediately, because the crystals lose efficiency. A diode laser won't drop that much, but it's not very healthy for it.


I don't get it. Is there a special purpose behind this?

 

[Sandor]

I am wondering, (and pardon me for being new to the thread, but) how come you guys don't seem to use pulser circuits for your lasers?  You all seem to be running them at continuous duty, which is much lower power than pulsing.

Is it just that you don't know how to build a pulser, or is there a reason that you are using continuous?
(Like is it illegal to run a pulser because of its possible use as a weapon?) The reason I wonder is that I don't even see much about pulser circuits on google, so I thought maybe the government had cracked down on them or something?

 

[IgorT]

I am wondering, (and pardon me for being new to the thread, but) how come you guys don't seem to use pulser circuits for your lasers? You all seem to be running them at continuous duty, which is much lower power than pulsing.

Is it just that you don't know how to build a pulser, or is there a reason that you are using continuous?
(Like is it illegal to run a pulser because of its possible use as a weapon?) The reason I wonder is that I don't even see much about pulser circuits on google, so I thought maybe the government had cracked down on them or something?

You are correct, when you say that pulsed an LD can reach a certain higher power. Sometimes even a much higher power. But due to the low duty cycle (required by the diode) in such pulsing, the average power is MUCH lower, than what you can get using CW.

Use as a weapon? Are you kidding? Not with diodes. There are certain laser types that can create enormously powerful pulses, but can not be driven in CW at all. But we mostly build diode lasers here.


You can find pretty much everything here, including people who could draw you a pulsed driver in minutes.
In fact some have built and tested pulsed drivers, with the same idea in mind as you, but discovered there is no point in doing that for what we want.. If you want good power for burning or just an impressive looking beam, you need a CW driver.


P.S. You have chosen an odd thread for this question....

 

[Sandor]

No, actually, I wasn't kidding, and I do understand you are using solid-state Lasers.  

In a non-weapon area, I was just reading yesterday about a new device to be used by homeland security for determining the contents of sealed containers...  It essentially works like an x-ray device, but allows identification of what compounds are in the container...  Let me think --It is running in the near-infrared at 1550 nM.  The main LD is a 130 mW solid-state laser, pulsed to achieve about 50 k-Watt pulses with a pulse width in the nano-seconds.

The idea behind pulsing is that you can dump a very narrow sharp rise and fall pulse through the LD without damaging it, and get an intense pulse that can zap through a lot of things.

Repeated pulsing can have a destructive effect on the target without overloading the laser diode.

I fooled around with these 25-30 years ago.  At that time I was doing good to find a laser diode capable of even 5 mW, but was running very narrow pulses at between 5 and 10 Amps current, using a capacitor-discharge arrangement.

 

[phenol]

50kW from a semiconductor solid-state laser? this sounds fictitious for a single emitter, but thats good news if a thing like that has been made. I have seen a few datasheets of pulsed NIR LDs capable of generating up to 100W++ under the conditions along the lines of: Ifpk>50A, Pwmax<50ns, duty cycle<0.05%, Vfpk>40-50V
Building a driver meeting such requirements would be far beyond the abilities of the average hobbyist.
Readily accessible LDs coming from dvd/cd burners are spec'ed for up to 350mW Pulse for Pw=30ns and Duty<35%. I guess they can output more if Pw is shorter, but there comes the other obstacle - how to make a driver capable of sourcing pulses with subnanosecond rise times - also a challenging task requiring precise tiny components and HF PCB layout with a microstrip line feeding power to LD. Some parasitic inductance there, some here and the cct may end up supplying horrendous pulses with heavy overshoot eventually killing the diode or degrading its performance in a short time.Every DVD burner has a driver like that with at least 2 outputs.

 

[IgorT]

I've heard about 5mW diodes being pulsed at very high currents and surviving as well.

And in certain cases, pulsing is required for a process to work, but it has no benefits for what we are doing here..
You get a higher total (average) power using CW with DVD or Blue Ray diodes, even tho they are originally meant for being pulsed.


I've also heard of some older low power green lasers using pulsed drivers, but it's very rare, or non existing these days (except by accident).

 

[Sandor]

I have seen a few datasheets of pulsed NIR LDs capable of generating up to 100W++ under the conditions along the lines of: Ifpk>50A, Pwmax<50ns, duty cycle<0.05%, Vfpk>40-50V
Building a driver meeting such requirements would be far beyond the abilities of the average hobbyist.
Readily accessible LDs coming from dvd/cd burners are spec'ed for up to 350mW Pulse for Pw=30ns and  Duty<35%. I guess they can output more if Pw is shorter, but there comes the other obstacle - how to make a driver capable of sourcing pulses with subnanosecond rise times - also a challenging task requiring precise tiny components and HF PCB layout with a microstrip line feeding power to LD. Some parasitic inductance there, some here and the cct may end up supplying horrendous pulses with heavy overshoot eventually killing the diode or degrading its performance in a short time.Every DVD burner has a driver like that with at least 2 outputs.

Quite true. In the unit I referred to, I was running 10nSec wide pulses at a rep. rate of 20 kHz, and sending superimposed audio signal (essentially pulse code modulation, although I had no way to replicate the negative pulse at the time, so it was a variation of PCM.  The maximum limit of my audio signal was 10 khz max and I was really working with a lower effective bandwidth than that.)  I believe that works out to a .02% duty cycle (I remember being concerned that I gave th diode plenty of time to cool down between pulses.

My original design would have used an SCR to dump the charge from the cap, but I could not come up with an SCR capable of handling it at that frequency, so I created an scs out of an npn and pnp uhf capable transistors to do the switching.  The SCS actually worked better anyway, since it was capable of turn-on and off.  (The SCR would have only turned off when the capacitor charge dropped enough so it stopped conducting.)  Using an SCS I was able to get a good looking sharp rise and fall on the pulse. (looking at it with an oscilloscope, of course,)

My experiment at the time was to try bouncing off the moon (A 'corner-cube' reflector array was left on the moon by some of the astronauts) I kept having failures, and suddenly I must have gotten the alignment perfect, because I suddenly got my transmitter music from the receiver.  Of course, the laser beam had a decent quality collimating lens and I was using a 10" schmidt telescope focused onto a balanced photo-darlington preamp as a pickup and feeding it to the main ampplifier.

My wife was not impressed at all...  She made a comment along the lines of "So?  It's music...  So what?"    She sure knew how to burst a guy's balloon...  I mean I am picking up a signal that went to the moon and back and all I get from her is "So?"

Just something I was playing with back then.

I was reading about the new TVs they are bringing out with rear-projection solid-state laser "guns" at 460, 532, and 635 nm which are supposed to have much better quality than anything else that has come out so far (as long as they iron out a couple bugs).  Anyway, what I am wondering is what power those lasers will have and how quickly "replacement" parts will be available for the hobbyist market...   <grin>

 

[phenol]

sandor, what power are you talking about? that laser must have had divine guts to send detectable pulse trains to the moon and back.
hams do the same tricks with radiowaves at freqs 50MHz up to tens of GHz - moonbounce radiocontacts with powers as low as 100W at 144MHz, of course the BW is far too narrow for anything but CW using very selective IF filtering and low noise antenna preamps. and there isnt a special radiowave reflector on the moon surface.

 

[Sandor]

I've heard about 5mW diodes being pulsed at very high currents and surviving as well.

And in certain cases, pulsing is required for a process to work, but it has no benefits for what we are doing here..
You get a higher total (average) power using CW with DVD or Blue Ray diodes, even tho they are originally meant for being pulsed.


I've also heard of some older low power green lasers using pulsed drivers, but it's very rare, or non existing these days (except by accident).

Ok, I understand.  As to the idea of higher total power, I suppose I might compare it to the ocean.  A slow rise in the tides with billions af gallons rising a few inches, opposed to only part of that total being pushed ashore in one quick tidal wave. ;D  The tidal wave will knock down buildings, even though it is much less total water.

Anyway, I am retired now, but anyone who wants to know more about pulsing, etc. can drop me an email.

I might even give you my idea for a "Star Wars" type blaster pistol - <grin>  (It's not a laser, it's only fired/initiated by a laser)  Never have been able to come up with a working light saber yet.

Gotta get back to my writing. (I  just can't stay retired.)  Catch you fellows later on.

 

[Sandor]

sandor, what power are you talking about?   that laser must have had divine guts to send  detectable pulse  trains to the moon and back.
hams do the same tricks with radiowaves at freqs 50MHz up to tens of GHz - moonbounce radiocontacts with powers as low as 100W at 144MHz, of course the BW is far too narrow for anything but CW using very selective IF filtering and low noise antenna preamps. and there isnt a special radiowave reflector on the moon surface.

Let me think, I am pretty sure when I finally succeeded I was dumping a 10 amp pulse over 10 nS from a charged capacitor. (Cap rechares during the off cycle)  Anyway, in case you are not familiar with the cube reflectors, you can not use them to send to someone else --only to yourself.  When light enters them, the light is bounced around the inside corner of a cube and comes directly back the same direction it entered.  Therefore, your own signal comes back to you.  The secret is not so much the power.  It should be possible with an even lower power level.  The secret is in the collimation of your laser beam.  You have to collimate it as carefully as you can so it does not get any bigger.  The more it spreads out, the less energy you will have (inverse square law).  This was my big problem and the reason it took me a while to make it work.  Your beam has to hit that reflector, to be bounced back.  The better collimated your beam the tighter and therefore the more signal you will end up with, but on the other hand, hitting the reflector becomes harder when your beam is smaller in  diameter.  However, that is the secret.

Oh, and what you said about hams, as you said, there is no radio reflector on the moon, but there is a laser reflector. With the radio transmission, they are bouncing off the moon itself and their signal can spread out over quite a wide angle and they still get enough signal for a contact. That is why I said the power is not so important as how focused your beam is.

OK, guys, catch you later.
Take care.

 

[IgorT]

Ok, I understand. As to the idea of higher total power, I suppose I might compare it to the ocean. A slow rise in the tides with billions af gallons rising a few inches, opposed to only part of that total being pushed ashore in one quick tidal wave. ;D The tidal wave will knock down buildings, even though it is much less total water.

I understand what you are talking about very well. One application that NEEDS a pulsed laser is writing a DVD. There these diodes are pulsed at a much higher power than we are driving them, because they have to produce a change in the surface of a DVD in a very short time.

But if you want to burn a hole through a piece of plastic, a CW laser diode with 200mW will do it faster than the same diode pulsed at 300 or even 500mW because of the short duty cycle required for pulsing.

The same goes, if you just want to enjoy a beautiful beam.


A laser pulsed at a VERY high power might pop a baloon instantly tho, and some people are interested in that, so why not show them how to do it?
I still think you should start your own thread(s) with all the "crazy" ideas you want to share.