Although I've always wanted to build a flash lamp pumped dye laser, I've refrained from any serious attempts until now. In my mind, there were too many variables to nail down - too many uncertainties. I was discouraged by the relationships of OC reflectivity (and respective transmissivity), dye concentration, pump energy and circuit inductance. The possible variations seemed overwhelming. The availability, cost and relatively esoteric nature of high voltage capacitors were yet another deterrent. All of this changed however when I encountered the brillient work of [1]Sothory Yun. Sothory Yun managed to build lasers with the most basic and common supplies imaginable. Best of all, he presented working examples of dye lasers that did not require commercial HV capacitors! The lamp pumped dye laser had been moved within reach owing to Sorothy Yun's work, but I was still hesitant due to my distractions with other projects. A final push was made by a friend in South Africa, Chris Hill. Chris had been wanting to build a dye laser for quite some time. During the course of our ongoing correspondence, Chris said bluntly "You should build a dye laser" - this statement was a final straw, and it resulted in my decision to make a serious attempt to build a flash lamp pumped dye laser.

The following three parameters, unique to dye lasers, are the most challenging considerations:

The following parameters are more general in nature, but they still represent a formidable challenge to the successful construction of a operating dye laser device:

Ongoing work:

Energy per unit volume

Based upon the wonderful work of Sorothy Yun, I've calculated an energy to volume ratio of 2.6E-2J/mm^3, or (conversely) a volume to energy ratio of 38mm^3/J. The genius behind Mr. Yun's "pocket" dye laser is that it is scaled down to the point where it can be pumped by very simple homemade capacitors.

My calculation serves as a point of reference whereby the required energy can be found for a device based upon the volume of its amplifying medium. The calculation provides a very general figure, as it does not take into account other important factors (namely dye concentration). The accuracy or effectivity of the calculation remains to be determined experimentally - this is a work in progress on my part. As of the writing of this text, I have not constructed my first successful flash lamp pumped dye laser!

• Application:

I plan to use an amplifier tube that is roughly twice the diameter of that recommended by Mr. Yun. In addition, my lamps arc length is 30mm (which can basically be thought of as the active length how the amplifier tube) as opposed to Yun's suggested 25mm. So what this all translates to is:

Step 1:

Volume = pi*r^2*h
3.14*(1.25mm^2)*30mm
3.14*1.6mm^2*30mm
Volume ≈ 150mm^3

Step 2:

Volume to energy ratio ≈ 38mm^3/J
1 Joule/38mm^3 * 150mm^3
3.95J
Required energy based upon ratio = 4 Joules

Dye concentration

Dye concentration is another factor that, in my estimation, must vary based upon other factors such as output coupler reflectivity, pump energy and amplifier tube diameter. Fortunately the guess work is eliminated by Sorothy Yun's example. He provides an extremely easy way to determine the required dye concentration, using an ordinary green laser pointer. The concentration would likely need to be reduced if using an amplifier tube that is substantially larger in diameter than that recommended by Sorothy Yun, and the output coupler reflectivity would presumably need to be increased accordingly. But this is a very general assumption on my part and even if I am correct, I do not know how to quantify everything in a common formula so that all of these factors can be adjusted proportionally. The best approach is to base ones design on something that has been proven to work, and then make experimental changes as desired. In the absence of adequate theory, initial design in the form of guesswork (as opposed to a design based heavily upon a successful example) will likely result in an exhaustive exercise in futility.

To be continued ...

Ongoing Work

My original plan was to make the 'end pieces' out of recycled HDPE. There are numerous YouTube examples of DIY recycling of HDPE. I quickly abandoned the idea however when I discovered bubbles or air-pockets in my solid HDPE pieces.



[1] http://laserkids.sourceforge.net