Do it Yourself Complete Green DPSS with O-like Crystals

[vk2fro]

Great thread. Helped explain to me exactly whats going on inside a cheap dpss pen, labby or any other green DPSS laser. I really enjoyed the read. I might give this a go myself but my mechanical skills are far behind my soldering skills

 

[Bionic-Badger]

Wow, I never saw this thread before either. This should go into Sam's FAQ or something. Cool stuff!

 

[Hemlock_Mike]

This is the "down and dirty" part of the DPSS science. This should be stickied for all noobs to see when they ask HOW !!!!
Good work, pictures and descriptions.

HMike

 

[DrSid]

It seems those output couplers are not available anymore at O-like. Any ideas where they can be bought ?

Also, ReNNo, do I understand it right ? You pump the vanadate with 808nm ?

EDIT: I've just played with one of my pens .. and I removed the small 'concave lens' in front of the crystals before .. and as I glued it back the laser went really down in power .. after reading this I thought it's the output coupler .. so I played with it a bit again to get the power back. And it is not output coupler ! Because the laser lases (in green I mean !) happily without it ! It seems it indeed is just concave lens to widen the beam to get wider beam at aperture (thus better divergence). I glued it back again, this time mainly focusing of having it centered correctly on the beam. The loss of power was actually misaligned pump diode, it needed about 30 degrees rotation. It even made 2 beams at one specific angle .. was it mod ? Or just some inner reflection ? Anyway now I have my laser (about 30mw though) back and this thread helped me understanding the problem, thanks !

 

[ElektroFreak]

Just thought I'd bump this thread, since it is one of the all-time greats IMO.. Down and dirty hands on sh*t.. man I miss those days. Seems so few and far between lately.. but it's stuff like this that makes LPF great.. to me anyway.


Where you been maus??

EDIT: Lol.. i found this thread by searching for it, and I didn't even know it's a sticky. Kind of silly to bump a thread that's permanently among the first threads in the section..

 

[mauswiesel]

Where you been maus??

i felt in love with nuclear physics !
let me show you some of my result with my wilson cloud chamber experiment, sorry for OFF topic :beer: :

The diffusion cloud chamber is a device which can reveal the path of ionized, subatomic particle, travelling at relativistic speed.
The diffusion cloud chamber can only detect charged particles : muon, electron, positon, proton, kaon...or indirect one created by neutral particle :gamma, neutron, K0... . It was invented (the expansion one) bye Charles Wilson in 1911. The diffusion cloud chamber allow to see continuous interactions of particle when the bottom is cooled at low temperature (this one is about -37°C with some peltiers). When we put some alcohol in the top of the chamber (Isopropyl alcoohol ), the vapors falls to the bottom and cools down : but not all the vapor condense, there is some which stay in vapor state, making a metastable layer of supersaturated alcoohol above the surface. Once a charged particle pass through this layer, it ionize some of the molecules of air or alcoohol : the ions created act as condensation nucleus and the alcoohol suddenly condense on this newly created ions, making a track of droplet following the path of the particle. The bigger is the track, the more ionizing is the particle (for example with the alphas).

Some interactions of my setup :

Alpha particle close up. An ionized cloud of alcoohol atom is surrounding the path of the particle. Alpha particles : are He2+ nucleus, 7350 times more heavier than electron so are not easily deflected by electromagnetic interaction. Due to their mass, their speed is lower and because of the high charge, alpha particle lose rapidly their energies with ionization, thus are easily absorbed by materials. Kinetic energy range from 3 to 7 MeV. For an alpha particle of 5 MeV (from Am241) :
15.000km.s-1, 5000 ionization per μm in water, maximum range of 50μm in water or 4 cm in air.

241Am decay (above, there is a source of Am in the chamber) : Americium 241 is a by product of the fission of 235U and decay into 237Np with the emission of 5.5 Mev alpha particles, 60 keV gamma rays and few keV conversion or Auger electrons . It has a half life of 432.2 years. The amount of 241Am in the picture is about 1μCi. The end of alpha track is often dense due to the “Bragg” peak.

Bêta particles : are electron or positon which have the same mass but opposite charge. Their speed is close to the speed of light (1 Mev~0.941c). Due to their little mass, they are easily deflected by electromagnetic interaction. Because they can easily accelerate when they come close to an atom, they lose most of their energies with Bremsstrahlung. They produce less ionization than alpha particle due to their monocharge, thus have a higher range. Positron when thermalized, annihilate with an electron to form gamma rays. For a bêta particle about 2 MeV :
Range : 6 meters in air, 1 cm in water, 3 mm in aluminium, 10 ionizations per μm in water.
Above picture is a "Delta ray " : An energetic beta particle (often electron) is knocking orbiting electron out of one atom. We can see the original electron deflected with an ejected electron at a few keV of energy.

Gamma rays : They are not detected in a cloud chamber because these “particles” which are also electromagnetic radiation, are neutral. They can interact in matter with photoelectric, compton, or pair creation effect and produce charged particle which are detectable. Photoelectric effect is the transfert of all the gamma’s energy to an electron which is ejected from an atom. Compton effect is the inelastic scattering of a gamma with an electron who are ejected. When gamma energy is above 2x0.511 keV, the gamma can disappear and form a pair of bêta particles. For a gamma of 1 MeV, it need 900 meters of air to absorb 50% of the gamma, 5.1 cm of concrete, or 0.85 cm of lead.
The picture above show some Photoelectric or Compton effect : In air, gamma do mostly photoelectric interaction under 30 keV, compton above 30 keV and pair creations above 10 Mev. Above, an electron is ejected by a gamma ray.

Gamma Annihilation (pair creation) : A magnetic field about 0.5T (direction of B into the paper) deflect the electron toward right and the positon to left when a gamma annihilate. The radius of curvature is given by the Lorentz’s Force by R=mv(Bq)-1.

Thoron decay : Some 232Th nucleus (T1/2=14.1x109 years) decay successively to 220Rn in the mineral. Thoron is a gas with a half life of 55s. It decay through alpha emission to 216Po which have an half life of 0.14s. Thus, 216Po decay immediately into 212Pb with an alpha disintegration. We can see some V or L shape : it is the simultaneous disintegration of 220Rn and 216Po.
A big one here with explanation :

About 10,000 muons reach every square meter of the earth's surface a minute. Traveling at relativistic speeds, muons can penetrate tens of meters into rocks and other matter before attenuating as a result of absorption or deflection by other atoms. Paralell track of muons come from the same cosmic ray shower .

Muon decay (above) : A track enter in left in the cloud chamber and is not really deflected by the magnetic field, due to a high mass. Then it "kinks" and is deflected to left by the magnetic field : it’s now a lighter particle, a positon which in fact come from a μ+ decay. The two neutrino are not detected.

Momentum transfert : The annihilation of a gamma produce a pair of bêta particles. The magnetic field, which go into the paper, deflect the positron towards left. But something happen, mid flight : Strangely, the positron start curving in the opposite direction as if it had suddenly become negatively charged. What has happened is that the positon has run head-on into an electron, transferring all its momentum to that electron. This can only happen if the mass of the positon is equal to that of the electron. The positon that stops would eventually have annihilated.

Elastic proton scattering : a very rare event which come from hours of movie. A cosmical proton interact with the glass wall of the chamber, ejecting another proton. The two protons are visible and entering in the bottom of the picture. One of the protons then collides with another proton which either comes from a water molecule (one of its two hydrogens atoms), or one of the hydrogen atoms in the alcohol molecule. This collision kicks the proton out of the water molecule and we now see both the scattered original proton and the new proton kicked out of the water molecule.

The most striking signature is that the angle between the 2 emerging protons is 90 degrees (it appears a little bigger than 90° because the tracks are pointing away from the camera).
Elastic scattering of two equal mass particles, where one is initially stationary, always gives an angle of 90 degrees between the two final particles.

 

[BShanahan14rulz]

You're the most curious cat I've ever met!

So, what's the deal with the tants and diodes stack?

And why do the particles leave tracks like that in there? are those tracks just fallen out of the air from some sort of gas at phase equilibrium in the tank?

You find the most interetsing things to DIY. I vote best off-topic post ever :drool:

 

[mauswiesel]

the capacitors and diodes make a cockroft walton generator. It produce a high electic field (10kV) from a neon power supply which produce 2000 V AC, supplied with 12V DC from a computer power supply. The electric field is needed to clean the unwanted ions and to have a clear view of the events.

The track of particle are revealed because the metastable layer of alcoohol is unstable and will condense when there is a perturbation : same effect as supercooled water : give a perturbation to the "liquid" water (at-20°C but still liquid!) and it will instantaneously transform into ice. That's the same principle here.
When vapor of alcoohol, coming from the top of the chamber, fall to the very cold plate, most of all the alcoohol molecule go into liquid state, forming droplets (you can see some "rain" of alcoohol in picture above, that's it).
But a tiny part of the vapor of alcoohol, even if the vapor is very cold in contact with the cold plate, won't condense. They stay in the vapor state, even if it's forbidden by thermodynamic, but are very unstable. A perturbation will force them to condense instantaneously, like supercooled water.
The perturbation will be the passage of a charged particle in the layer of metastable alcoohol : the nuclear particle always lose some energy when traveling through matter, creating ions (making ionized atom in his path). This ions are created by ejecting some electron of water molecule or alcoohol present in the particle's path. These ions created are the Perturbations ! it will allow metastable vapor of alcoohol to suddenly condense, but many of vapor molecule condense in the same time, and we see a big cloud of condensation which follow the path of the particle, making a track visible. When there is no radioactive source in the chamber, there is still interactions, because cosmic ray are always coming to us.
See my vid on youtube

http://www.youtube.com/watch?v=AuUldLya3Wo

some picture about the building : wilsoncloud.wordpress.com

you can build one, it 's one of the first air cooled continuous cloud chamber ever made (with the guy from intrusctable at nothinglabs.com). You need 4 peltiers, a PC power supply, one or 2 radiator for processor, some glass to build the chamber (like an aquarium), thermal grease from dealextreme and some other stuff easily found. estimated price : 150-200$ same as a good laser mod, and it won't frie !
This experiment allow you (and your public!) to show the radioactive world, perfecly undetectable by human sens. This is awesome when you think about their dimensions, that's why i fell in love with that, this is madness !!!
spec of particles
dimensions :10^-15 m
weight : 10^-31 kg
speed : 15.000 km/s and 298000 km/s
origin : from the deep of universe or sun

of course story won't stop here, you can make your own interactions by making a neutron source for example with some beryllium and americum, and observe transmutation of elements...

 

[sEyehealth]

Hey u have great photos.......
By this any 1 can do it by themselves.......

Thanks for adding such a great post.....

Thanks..

 

[Misanthrop]

Going through the process of repairing a 1Watt green right now..

CNI isn't responding to my emails asking about what Diode would be in it.. so I can just go out and buy one..

Does anyone know..?

80% loss of power with shit crystals.. but seeing as this is a CNI laser it would have good ones.. so I'm thinking 60% loss maybe?

Calculations speak for themselves...

Regardless I would still like to know what Watt of diode usually goes in these 1 watt 532's..


Thanks..

 

[Misanthrop]

Jesus thanks for the information !!

 

[ElektroFreak]

Going through the process of repairing a 1Watt green right now..

CNI isn't responding to my emails asking about what Diode would be in it.. so I can just go out and buy one..

Does anyone know..?

80% loss of power with shit crystals.. but seeing as this is a CNI laser it would have good ones.. so I'm thinking 60% loss maybe?

Calculations speak for themselves...

Regardless I would still like to know what Watt of diode usually goes in these 1 watt 532's..


Thanks..

I know this is a tad old, but I would use a 5W 808+/-3nm diode with FAC lens. This way you will be slightly underdriving the pump diode which is ideal for long life.

 

[nikola tesla]

WOW great threat and great pictures!
Just one question: does this method apply for other laser colors too?
In other words: wich colors can i also achieve with this method?

 

[ElektroFreak]

For the hobbyist green is pretty much it. DPSS technology can be used to achieve MANY different colors, but there is considerable difficulty involved in anything but green which puts other colors out of reach of hobbyists as a general rule. This is due to a variety of factors including component quality, supply and demand, rarity of raw materials etc. Green DPSS is very common, so the diodes, crystals and assorted optics are very easy to come by, and today even the cheap stuff is very good quality compared to just a decade ago.

Even so, building your own green DPSS can be a challenge.. it requires patience and a lot of learning.

Here's a VERY good read on the subject:

Sam's Laser FAQ - Home-Built Diode Pumped Solid State (DPSS) Laser

 

[nikola tesla]

thanks man sounds really interesting
so what do common lasers use in order to get different colors?
I thought it was most times an IR laser hitting some material that changes the frequency?

 

[Sputnik77]

thanks man sounds really interesting
so what do common lasers use in order to get different colors?
I thought it was most times an IR laser hitting some material that changes the frequency?

That can be the case with some other colors, but pretty much all the ones you will come across, that are DPSS, (Diode Pumped Solid State, a diode pumped crystal set) will be green.

Nearly all the lasers you will come across besides green (red,blue and violet), the diode is not IR (except IR lasers). It is in fact a diode that directly produces the said wavelength, similar to an LED. The cavity in which lasing occurs, and produces said color, is directly part of the die itself. No frequency manipulation happens outside the diode can.