Laser Kids

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This photo shows a low-pressure continuous mode CO2 laser built upon industrial 3 W rated sealed tube. The laser is fed by alternating current from electronic halogen lamp transformer passed trough an ignition coil. For portability it was necessary to get rid of water cooling. A very powerful cooler presses the air through that earlier was a water cooling jacket. As the result the laser does about 1 Watt of output and completely independent of tap water.

Three step Marx bank generator. The capacitors are rolled from kitchen foil and A4 format mylar (laminating leafs) with 125 mcm thickness. Charging voltage 12 kv. Output pulse is 3 J x 30 kV x 500 ns.

"Cosmodrome." The Megawatt pulsed RF generator based on a tank circuit. Intended for feeding lasers by high frequency. Output: 1 J x 10 MHz x 1 mcs. It was named so for its futuristic outfit. One may see a leyden jar capacitor with water dielectric. It is charged to 100 kV before the pulse, and oil filled spark gap, that provides reasonable Q-factor for the circuit without use of compressed gases. However the oil filled spark gap appeared to be unstable - the discharge voltage varied by factor of two. This fact has defined the fortune of the construction - it appeared to be useless... as laser driver. But as an EMP gun... After it fires, a computer in other room loses keyboards and mouse. When it is done with a small antenna - it causes alarm clock of neighbourers to ring chaotically. OTOH now I have a new computer, multimeter and oscilloscope.

"The Kuzma's mother." (Ultra)fast pulsed transformer rated to 100 kv. The winding that You see at the picture is the SECONDARY one. In order to improve efficiency and to avoid the troublesome resonant mode of operation the ferrite core is used. Output is about 2 J with amplitude ~100 kV in form of fast decaying oscillations having the period of 2 mcs. Or either (with matched load) thee is a single pulse with less than 1 mcs duration.

The "sailship" Marx bank generator. Uses home rolled capacitors too. 4 steps 72 nf each. Charging voltage is 12 kV. Output is about 20 J at 40 kV in 500 ns pulse. A linear halogen lamp (500W x 220V) lights in a flashlamp mode i.e. the current flows through plasma and not through incandescent filament. And then who has said that it is impossible to build a dye laser using a common halogen lamp?

Still life in the "double martini with soda for droids" style. Two fast oil filled Tesla coils in the opposite series connection. Spark length is 14 cm. Length of single spark, do note. In the mode of fast repeating pulses it may cover about a half of a meter. This device was intended to be used as a driver of longtitudal CO2 atmospheric pressure laser. However the success of its creation haven't yet been attemptful.

Dye laser cavity. Not a very suitable to be a guide subject but fully operational. Borosilicate glass tube. 6mm inner diameter, 8 mm - outer diameter. The lamp is 8mm outer diameter, and has 105mm discharge length. (Bought at electronic goldmine (ty, JS)). Windows are made of uncoated glass. Mirrors are from an old He-Ne laser.

"500 bucks on the table" etude. Dye laser driver. 2-step Marx bank, made of two Maxwells. It has been built by steps of Jon Singer's work. Pretty expensive, but works. For the beginning a reliably working sample was needed. However the spark gaps are home build (air filled), not EG/G type.

Here comes the dye laser spot. Rhodamine G (No, not "6G"!) in isopropanole. Rhodamine is taken from old supplies, and isopropanol - from a hardware store. Here is 6x10^-5 mol/liter concentration. As it turns out the key element of the laser is a car fuel filter (You can see it at right bottom of the picture.) Without it the laser refused to oscillate at all.

Drunk to Green. Fluoresceine generates in... vodka. At about 2e-5mol/l concentration. Laser tube has 4mm diameter. Output mirror - is a piece of He-Ne back mirror (the front one transmits too much). All other is the same as on photos above. Also one can see a plastic cup with the dye solution and an aquarium pump bathing inside it.

Rhodamine in isopropanol got superradiant under lamp pumping! No mirrors at all. Only lamp and capillary with dye. 1e-3 mol/l concentration, 1.5 mm bore diameter. The lamp and driver are the same as on photos above. You can see that laser spot has form of ring. And this ring widens from pulse to pulse.

Heres a try to build an x-charge laser (pulsed barrier discharge is crossed by main dc discharge). One electrode is sectioned and resistor ballasted. Some friend of mine said that the tube is fat like hamster. And here it got a name 'Rastrapovich' - the name of one hamster-hero movie character.

X-charge system again. Here You can see the front mirror mount and a double discharge driver, based on two capacitors and double chambered coupled discharger.

The x-charge in action. You can see two tubes (wrapped by mylar sheet) as ignition electrodes. The main (conductive) electrodes are in kinda fade. On both photos You can see barrier discharge layer on the mylar surface and a glowing column of volumetic discharge. Left is before modifications of driver. Right is after them. The column glows rather brightly. However it appeared not to be enough for the laser to reach the threshold.

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Laser spark. Manifestation of one of the most concentrated energies on the Earth. In the focal point of the lense the density of the laser radiation is so high that electric field of light itself becomes strong enough to cause breakdown of the air. (Kinda similar to electric type of the breakdown.) The laser spark is rather hard to obtain from a homemade laser. One needs not only high power laser beam but also a tight focusing. This is the place where the common automobile aluminium mirrors fail - due to their huge aberrations.

Here is the laser spark with a lense having longer focal length than the one on previous photo. In an attempt to show that the plasma ball is formed not on the surface of something there was placed a piece of paper. Curious side effect: one can see a tight spot of fluorescence behind the laser spark. What could it be? Lasing of air nitrogen?

Here is a video clip, showing the laser spark and the laser itself. When camera moves around, it is undoubtful that the spark ignites directly in the midair. Static photos usually do not provide the sense of that kind.

DIY Laser Pointer based upon a 5W NIR laser diode. Why so big? The larger hole the longer is its usage range and smaller its spot. Output is made with a cheap chinese lense, and the body is sewers plastic tube. Does it burn? Yes it does. Later I will put here some photos or maybe a video.
The same laser pointer. Rear view.

The promised video of this laser pointer in action. This one is a bit upgraded in comparison with the one on the photos above, but uses the same diode. More details on its electronic and optics can be found in this note.

Yet another laser airgun. The (open air) nitrogen laser uses a charge transfer circuit and utilizes a frame which was initially intended for a co2 laser (7 murata's 2nf x 40 kV each). A stacked homemade planar capacitor is used here as a peaker. One can also see a very high voltage spark gap mounted on the frame. Its threaded surface helps to suppress flashovers greatly. This construct endures up to 40 kv.
The framed open-air nitrogennie in operation. This is the first air laser that gives noticeable readings on the Peltier calorimeter. When its spark gap is set to 30 kV the output is about 1 mJ, that corresponds to more than 1 MW power.
The end view of the powerful airlaser. One can see a multi-layered planar capacitor having been set up just under the electrodes (it serves as a preionizer too). The fact that this capacitor really can pump an air laser which has lifetime of about 1 ns does allow to make more presize estimations for a discharge time for that kind of capacitor. Earlier I estimated it as several tenth of ns, and now I can say it is of the order of a few ns.

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Another open air nitrogennie. Uses the sum of technologies: sharp edged electrodes and rail type spark gap. Dielectric is mylar 0.125 mm thick. Wings are 10 cm wide (each) and 32 cm long. Electrodes are made of aluminium triangle (in section) doorhandles. Their length is 30 cm.
The main intention is to drive test samples with (probably laser) dyes. The thing appears to be pretty powerful. It gives blinding bright spot on a piece of paper and drives rhodamine 6g to lasing at 45 cm away from the end of the electrodes without any focusing optics. The same distance for coumarine reaches above 1 meter. It seems that under its beam anything will lase. There are many photos of this laser in operation, see the report on dye lasers here. Its operational voltage is 13 kV (5 mm spacing in the spark gap)

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Yet another open air laser. It appears to be almost a direct clone of Alfonso Rodriguez designs (With a precision to technologies and resources - do note neodimium magnets, for example. They are used instead of bolts and weights). Its power, however didn't exceed the output of the winged system (see above): rhodamine 6g at 40 cm. Storage capacity is 8 nf (4 white muratas), peaker is 5.5 nf (aluminium foil wing 32x10cm), operational voltage 30 kv (12 mm in the spark gap) The spark gap is common point type, made of M16 acorn nut and a piece of stainless steel as the opposing electrode. The main purpose is to serve as the reserve for previous (winged) laser, when it is under repairs after its dielectric has been broken. However it lost actuality when the infinite source of mylar was found in the form of kitchen baking sleeves.

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Ruby laser. You can clearly see an AN/VVS-1 (MS-60) pump cavity installed into homemade resonator. The original (MS-60) laser is well described in Sam's laser FAQ. However it is stated there that it has threshold of 75..100J. As for me, I failed it to lase even in more closed resonator until the energy has reached 300J - see a big, quick-hand assembled, capacitor bank on the right photo.
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It appears that there's no need to hunt for a special dielectric interference mirrors. The one, You got from dismantling a DVD-burner head, are sufficient. Those should remain in Your stock after the times when You built Your powerful red laser pointer using the DVD diode. The head usually contains several small mirrors. Some are reddish coloured - use them as output coupler, and some are yellowish coloured - use them as back mirror. On the left photo at the center of mirror - no it is not hole for beam output. It is the optical damage of the mirror. However even with the damaged mirror this laser gives more than a Joule of output.
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The ruby laser in operation. The snapshots are taken with a small web-camera through a welder filter (right one) and through the same welder filter with addition of red laser-safety googles. It appears that my usual camera (Nikon Coolpix 4600) sees ruby laser spot as blue colored, so it is almost impossible to distinguish it on the lamp light background. Even with a welder filter you can see a very strong pickup. And only with addition of red filter the camera agreed to register the laser spot clearly.
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Spots of the ruby laser. On carbon paper. On undeveloped photographic film. And micro hole in a razorblade (this one is done by a single pulse).

CO2 laser from a nitrogen one. As one could easily expect it does not work.

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"Furry" - an attempt to make a laser with a carbon fiber preionizer. Its electrode system consists of 10 mm aluminium tube (anode) and a homemade fetlock (cathode) made of carbon fiber thread. Carbon pins have a very emission property under the electric field applied. Some ppl have offered to use this as a preionizer. Its preliminary tests were very encouraging... but when a full capacity required for working laser was applied, the discharge began to show signs of contraction and ununiformity.
Left photo - the discharge as seen from aside of the tube. Right photo - the discharge as seen through the output window. 200 torr, air, 14nf, 25 kv.
No lasing was observed inspite of all efforts. At any voltages or pressures. It is probably due to too narrow discharge column or either due to black spacings along the discharge.
Photo of the mockup discharge 0.5 bar 2nf air.

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Working model of another x-charged laser. The assembly at first produces the barrier discharge between two mylar insulation layers. And then it connects main electrodes. It even works - 750 mcJ at 250 torr. It shows a rather strange behaviour - at low pressure it produces sliding sparks and the higher pressure is the more stable volumetic discharge becomes. Working range is however too narrow +5% of pressure above the sliding spark. It does not lase above because the ionization multiplication in the discharge becomes too low and it does not lase below because of the sparks. The toy is useless for practice but it gave me more understanding about behaviour of x-charge (Rastrapovich-like) systems
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Left - discharge as seen from the back mirror side. 200 mbar, air+CO2. Right picture - the electrode structure as seen from its end.

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