A Charge-Transfer TEA Nitrogen Laser That Is Driven by a Small Marx Bank
[Started on May 15, 2011.]
Prolog:
This page is intended partly as a followon to
the “Easy TEA Laser” page,
and partly as a standalone project. It describes a relatively powerful room-pressure nitrogen laser.
Before we get any further along, we need some safety information and a disclaimer.
!! WARNING !!
If you build this project you do so at your own discretion, and at your own risk.
These lasers use high voltages, and capacitors that can store lethal amounts of energy. They put out invisible ultraviolet light that can damage your eyes and skin. It is extremely important to take adequate safety precautions and use appropriate safety equipment with any laser; and it is crucially important with lasers that involve high voltages and/or produce invisible beams!
In addition, this particular laser uses two open spark gaps, which will damage your hearing if you do not use adequate ear protection. I strongly suggest that you acquire and use at least a pair of sound-protection earmuffs of the type used by shooters at rifle and pistol ranges; they look about like this:
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Figure 1: Hearing protection
(These cost me $35, and they are definitely worth it.)» Read the rest
Pumping a CW Dye Laser with a Green DPSSL Module
This project is part of a larger project I have in mind, which requires a mode locked laser. (That project, or at least its earliest stage, is described in TJIIRRS #23.) I initially tried passively mode locking a blue diode laser, but that proved to be somewhat fraught, and I need to find an appropriate detector before I proceed further with it. (I may also need to try active or hybrid locking.) For the moment, I have set that approach aside in favor of a different one. We have an old Coherent CR-599-04 jet dye laser and a Coherent 5920 dye circulator, and I decided that it might be a good idea to attempt to get these running as a possible alternative path.
I thought about using the blue diode laser to pump the CR-599, but there are two apparent obstacles. First, the blue diode is a multimode device, and it may not be possible to focus the beam from it down to a suitable spot size: jet dye lasers generally utilize spot size of less than 50 microns diameter, and I think they prefer 10 or 20 microns. Second, it is difficult to find a low-threshold dye that absorbs » Read the rest
A Joss Research Institute Report: The Dye Laser Head We Bought on eBay…
A Joss Research Institute Flashlamp-Pumped Organic Dye Laser
(February, 2004)
Back in December, we won a dye laser head on eBay. (Our thanks to “teknogod4u”, who offered it.) It had a flashlamp and a dye cell in it, and looked interesting. The light from the flashlamp was coupled into the dye cell by a diffuse white reflector, and I wasn’t sure whether that would work at all well.» Read the rest
Your DiY Nitrogen Laser is NOT a Blumlein!
An Examination of the Amateur Scientist Circuitboard Nitrogen Laser
Contents:
Abstract
Preliminaries
Blumlein and His Circuit
The Issue of Latency
Travelling-Wave Excitation
Issues Related to Scale
Power and Energy
Closing Remarks
Some Interesting Papers
Abstract
Many Do-It-Yourselfers have built nitrogen lasers, often from a design published in the Amateur Scientist column of Scientific American magazine. This page discusses the text of that column in some detail, and shows several ways in which the explanation of the design and how it operates is faulty.
To Begin
In the Amateur Scientist column, on page 122 of the June, 1974 issue of Scientific American, there was a design for a tabletop nitrogen laser. It was written by someone named Jim Small, who was a student at MIT at the time. The article was later republished in the Scientific American book Light and Its Uses, and is also on the CD of Amateur Scientist columns, which you can get from The Society for Amateur Scientists. I have also found this CD available from The Surplus Shed, and from American Science and Surplus.
The design isn’t bad at all: it’s easy to build, easy to operate, and puts out enough energy to drive a
Joss Institute Projects: A “My First Laser” project for the DIYer
Joss Institute Projects:
A Straightforward TEA Nitrogen Laser for the Do-It-Yourselfer
(A “My First Laser” Project
That Evolves into a Higher-Performance Laser)
[Started on April 8, 2011.]
width=”450″ height=”300″This photo shows a fairly complex version of the laser in operation. (The initial version is simpler, and easier to construct.) The output is not visible to the eye; the fluorescent objects on the left and right indicate the presence of the beams: partly because there are no mirrors, this laser produces two.
Prolog:
Amateurs have been building lasers since fairly shortly after the laser was invented. Several laser projects even appeared in the late (and much lamented) Amateur Scientist column in Scientific American, which is now, fortunately, available in its entirety on CD-ROM. There are also various pages on the Web that provide information about DIY lasers of various sorts, and I provide links to some of them at the end of this page.
Unfortunately, I see quite a few videos on YouTube in which someone has bought a little laser module and hooked it up to a battery; they then proudly claim that they have built a laser. That’s pretty sad, especially when almost any of them actually » Read the rest
Joss Research Institute: Lasers
Lasers at the Joss Research Institute
- A straightforward low-pressure nitrogen laser design intended for DIY folks
I am also working on some more advanced designs; you may want to take a look at the low-pressure nitrogen laser pageset that is among my research reports, though you will want to be aware that I include lots of information about failures as well as successes, so you are probably in for a bit of a slog.
- An unhappy discussion of the Scientific American “Amateur Scientist” nitrogen laser or, to be more accurate, of Jim Small’s explanation of how it works.
- Rebuilding a damaged Avco-Everett C5000 nitrogen laser head that we acquired surplus on eBay
- Testing and using a surplus Molectron [low-pressure] nitrogen laser, also acquired on eBay (includes some information about tuning organic dyes that you are pumping with the nitrogen laser)
- Repairing, checking, and using a PRA LN-1000 [TEA] nitrogen laser, also acquired on eBay, with a note about tuning organic dyes under TEA-N2 pumping
- A bit more information about nitrogen-pumping organic dye lasers
- A “photographic tuning curve” for 4-Methyl-Umbelliferone, pumped by a low-pressure nitrogen laser
- A photographic tuning curve for 7-Diethylamino-4-Methyl-Coumarin, under flashlamp pumping
- A flashlamp-pumped organic dye laser that
Joss Institute: TEA Nitrogen Laser Principles
Joss Institute Projects:
More Information about TEA Nitrogen Lasers
Please note: this preliminary version is, as of early May, 2011, only just begun, and is extremely incomplete and disordered. If you want further references or you want to ask a question, you will find my email address at the bottom of the page.
Background
About Nitrogen Lasers
The nitrogen laser was discovered in 1963. As far as I can recall, it was the first ultraviolet gas laser, the first pulsed ultraviolet laser, and possibly the first-ever ultraviolet laser. It puts out short pulses of light at a wavelength of about 337.1 nm, a little shorter than the wavelength of an ordinary “blacklight” but not quite short enough to be described as “midwave UV”. This light is not visible, and it is even more dangerous than the light from small visible lasers. In addition, the laser operates on high voltage, so you should ONLY attempt to built it if you are prepared to exercise appropriate safety precautions. (I will list a number of these as we proceed.)
The nitrogen laser has very high gain. Excited nitrogen gas amplifies so well, in fact, that nitrogen lasers can usually operate without any mirrors
» Read the restJoss Institute Projects: Restoring a Commercial Room-Pressure Nitrogen Laser
The PRA LN-1000 Nitrogen Laser
(24 May, 2004 ff, with some additions in 2010 and 2011…)
Overview
The PRA LN-1000 nitrogen laser operates at room pressure, and puts out pulses that are approximately 800 psec long. (At least, that was what the mfr stated. Most room-pressure nitrogen lasers seem to have pulsewidth between about 600 psec and 1 nsec, and I do not yet have an easy way to check, so we’ll leave it as given for now.) The laser is rated to deliver about 1.5 mJ, which corresponds to more than 2 MW peak power. Here are two views of it:
We won this laser on eBay, some time ago. When it arrived I found the key broken off in the lock (fortunately all the way in, so I could turn the switch with a screwdriver); some of the screws were missing from the case, and it was clear that not all was well within.
I dusted out the HV section and tried running the laser. It mostly self-triggered, emitting various snorts and barks, and it only occasionally lased; but it was clearly a real machine and not just a pile of scrap. I disassembled
A Joss Research Institute Web Report: 4-Methyl-Umbelliferone (“4-MU”)
A Joss Research Institute Report on
4-Methyl-Umbelliferone,
A Laser Dye with Extremely Wide Tuning Range
…Under Certain Circumstances
(11 October, 2007)
The first coumarin in wide use was 7-Diethylamino-4-Methyl-Coumarin, often called Coumarin 1. (Exciton lists it as Coumarin 460.) It lases in the indigo and blue, with a tuning range of about 437 nm to 485 nm, depending on the pump source. Since Coumarin 1 was discovered, quite a few other Coumarin compounds have been found to be good laser dyes; the most common ones offer good performance across a significant portion of the visible spectrum, roughly 420-620 nm. Many (if not most) of these dyes are amino-substituted, but there are also hydroxy-substituted coumarins that can be lased. This page describes the best-known member of that group. (More specifically, the Umbelliferones, which have a hydroxyl group at position 7.)
7-Hydroxy-4-Methyl-Coumarin, usually called 4-Methyl-Umbelliferone (I will refer to it here as 4-MU, for brevity) dissolves well in ethanol and isopropanol, but is not easy to lase in neutral or acid solutions. Two main characteristics distinguish this dye. The first is the fact that it has the widest tuning range of any ordinary laser dye: from 370 to 580 nm (!), in
A Joss Research Institute Report: A Simple Nitrogen-Pumped Tunable Dye Laser
Joss Research: A Simple “Breadboard” Dye Laser for Nitrogen Pumping
(2004 Jan 31)
Here’s a dye laser, assembled on the bench; the nitrogen laser (upper right, first photo) reflects from the large mirror at left, which focuses it into the [homebrew] dye cell in the middle. (In this photo, it contains Rhodamine 6G in 95% ethanol.) The prism lets me tune the output.
The entrance window of the dye cuvette is a fused silica Brewster plate that I’ve had lying around for a while; the end windows are pieces of microscope slide. I find that although most microscope slides are made of rather green glass, a few are extremely clear and uncolored. I reserved a few of those to use as end windows, because I don’t have enough fused silica. I suspect that I could use the same material as a front window, but I haven’t actually tried it yet. (Alternatively, if you can assemble the cuvette without breaking it, a cover slip should work as the front window — it’s thin enough that it probably won’t absorb much of the pump pulse.) The base and back are pieces of ordinary microscope slide. I’ve used aquarium-grade silicone caulk