Lasers

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

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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

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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

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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

» Read the rest

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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.]

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

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Joss Research Institute: Lasers

Lasers at the Joss Research Institute

» Read the rest

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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 rest

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Joss 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 the primary spark

» Read the rest

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Joss Research Institute Web Report: A Large Doorknob-Cap Nitrogen Laser

“DK Plus”

A Second Simple Nitrogen Laser
Using “Doorknob” Capacitors
in an LC-Inversion Circuit,
Primarily Intended as a Research Tool

Abstract:

This page presents the design and construction of a nitrogen laser that can be built by a Do-It-Yourselfer. It is a scaled-up version of a smaller and simpler previous design.

The laser is constructed, as much as possible, from materials that are available at hardware stores and hobby shops: plastic “lumber”, aluminum rulers, steel rods, compression fittings, pieces of basswood and spruce, etc. I used a commercial spark gap, but it is eminently feasible to build one. The two items used in this design that are not easy for a do-it-yourselfer to construct are the “doorknob” capacitors, which are available from time to time on eBay; and the fused silica windows, likewise an eBay item, though it is possible to use fused silica microscope slides, which I buy from EMS.

This laser uses either nitrogen or a mixture of nitrogen and helium at low pressure (roughly 30-90 Torr each), runs at 25-30 kV, and puts out pulses of more than 1.6 millijoules, lasting ~8 nsec FWHM. This corresponds to average pulse power of 160 kW and (assuming a vaguely

» Read the rest

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Joss Research: Lasers: Nitrogen: The Molectron Nitrogen Laser; Tuning N2-Pumped Dye Lasers

Joss Research:
The Molectron Nitrogen Laser
and
Tuning a Nitrogen-Pumped Dye Laser


[Note: This page is largely about a commercial laser. If you are interested in building your own, please see the “DKDIY” page instead.]


In the Spring of 2002, we bought a used Molectron N2 laser on eBay. Here are a few photos of the case & controls; if you want more detail you can click any of the small images for a 640×480 px version, or use the text links below the small images.

                 
1600 x 1200 px             1600 x 1200 px             1600 x 1200 px             1600 x 1200 px

It proved trivial to bring this machine online, when I finally got to it, in the Spring of 2005 (argh): I removed a broken cable-tie from inside the case, powered it up, and adjusted the thyratron reservoir voltage and the mirror alignment.

Here are two fairly representative traces, taken on 3 June, 2005 using a Tektronix 7104 scope, a 7A26 (if I remember correctly) plugin, and a nice fast photodiode sent to me by Howard Davidson a while back:

     

[Note, added on 2006 January 22 and 24: I have taken more photos of ’scope traces, this time using » Read the rest

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