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Feasibility of diode-pumped dye laser (just a thought).

LSRFAQ

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Ah, but your missing a few things. I did help a PL member get a professionally made ring dye laser lasing with solid state pump, in his case a little less then 4 watts of 532 nm DPSS Green.

First of all forget the static cell with no flow. Triplett State happens so fast that to overcome it in a static cell you need a q-switched (massive energy stored in crystal host) laser or a capacitive discharged ultrafast laser with huge peak powers like a Nitrogen system. . Even cells pumped with Q-switched doubled YAG in large dye lasers have a few meters per second of flow.

Second issue is beam quality. To get a finely focused spot, tiny enough to lase at pump powers under tens of watts, you need a laser with a modest M Squared (M^2 ) beam quality measurement, ie a M Squared approaching say 1.3 or better. I've yet to see a diode correction set up get below ~3.5...
There are papers with HENE pumped IR dye lasers running at a few microwatts of output, simply because the IR dye is amazingly efficient, and the fact that unless you have incredible peak powers in short pulses, the quality of your pump beam and the ability to focus it to a tiny spot trump any other requirement.
The HENE has a near perfect M Squared, so they could threshold the tiny flowing jet laser.

Third issue is there is little advantage in pulsing Nichia type diodes. They are usually already running so close to their peak efficacy and design maximum running CW. Attempting to overdrive them to get a high peak power pulse generally just results in a mirror faucet being blown off one face of the diode chip.


In the case of my old friend, even with the DPSS pump, I had to send him some special optics with very low output transmission tailored coatings. Basically a lab dye laser optic to go in place of the OC on the medical version, and he had to play musical mirrors to get a stable cavity.

For four watts of multimode pump into a flowing jet dye laser with a ~20 micron focal spot, he received ~200 microwatts of orange output after optimizing everything. It took him four days of aligning just to get a flash of lasing.
Reason being his pump energy density was just slightly over threshold.

Ti:saph is much, much easier to threshold then a dye, and it does not have the triplet state issues as well as having a much longer upper state lifetime.

There is a reason most dye lasers get pumped with an argon ion laser or a high class DPSS like a Verdi..
Simply beam quality that turns into a really dense spot of energy.

Your two choices are beam quality or immense peak power. The ti:saphs that run off a Nichia diode have a lot of conversion per unit of pump then even the best dyes.

If you don't mind an IR DYE, then you have a chance of pumping a dye with a 650 or 640 nm singlemode or pair of singlemodes combined with a polarizing cube to a few mW. The custom 750-800 nm optics would not be cheap. Its just a quirk of molecular chemistry that there is one or two super efficient dyes in the IR that have high pump adsorption and huge gains, far higher then Rhodamine.

Dye laser books edited by Duarte or Schafer should be going cheap on Abe Books if you want to learn why what you seek is so difficult.

I would encourage you to start with lamp pumped or N2 pumped Dyes.. The lamp has to have a really short pulse, and the Scientific American Dye laser plans with the Air Flashlamp would serve you well.
Short pulse means very low ESR flash capacitor charged to a very voltage, usually with a pulse forming network to shape the lamp pulse for high energy. A generic photoflash will not get you there. Dr. Lankard's design works well because an air flash is self terminating.

Steve
 
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