Tuning lasers

[museman]

Hello,

I'm sorry if this is in the wrong place... but this is the best place I could figure.

I have been reading a lot about tunable lasers.
I've found a lot here
TUNABLE LASERS

But I was just wondering if anyone knows why you don't see tuning
in many laser light shows or even laser pointers. To me it seams like
an amazing feature to be able to change the color back and forth isn't being used enough.

Is it the price?
Anyways I would love to know why it isn't used that much.
Or maybe it is and I just haven't seen it or have a misunderstanding as
to what laser tuning is. Do you think there is a way to make a home
made tuning laser?

And can laser tuning change wave lengths while the wave is running or
do you have to turn it off and then re-set it.

I know this is a lot of questions and I'm sorry.
But I'd appreciate any clearing up you can do!
Thanks

 

[charliebruce]

I suspect it's a combination of:
Cost
Stability (also stability under modulation, unless using an AOM which adds more cost)
Power
Range of lasing colours
Availiability of parts
Possibly safety of chemicals used in dyes

Mixing R,G, and B (or V) in the right proportions is so much easier and results in a brighter, more powerful beam with less stability issues, which also ends up being cheaper.

As for technical questions in the last section, I don't know enough to give an intelligent response, sorry.

 

[photonaholic]

I just read over that and it sounds complex and expensive not to mention how would all these optics fit in a pen size package??

 

[museman]

ha... true they wouldn't fit!!

 

[HIMNL9]

Theorically, it can be done easily (relatively easily) in one way, for gas lasers ..... and in other ways with a lot of difficults, but this is a different question .

The easy way in which it can be done, is the same in which He-Ne tubes are built for emit different colors, instead just the more common red ..... just make the brewster windows with a high optical density material, and turn them in different angles ..... at each angle correspond a different wavelenght, so, the mirrors cavity increase the wavelenght at which the brewster windows are tuned more than the others, and the color change ..... using this system in conjunction with mirror cavities that can be regulated for resonate with the same wavelenght of the brewster angle (tunable cavity), is possible to build a variable color laser system (ofcourse, the tube need to be used with mixes of gases that produce all the colors that you want )

But i doubt that this can be done at hobbyst levels, anyway

 

[photonaholic]

In light shows they use 3 lasers R/G/B to create any colour.

3 DPSS modules are far less expensive and complex, so I doubt a "tunable" laser would be economically viable for that either, since RGB systems can be had at rather affordable prices.

To my understanding, this tunable laser system is so very complex and expensive it has probably never been out of the lab yet.

In order to adjust the optics by mere nanometers you need very complex and delicate equipment.

 

[museman]

wow HIMNL9 that sound awesome!
It sounds over my head... But it seams like it would work.

Hey I found a plan for building a
Tunable Dye Laser
Laser Plans, Laser Projects, Kits

But it costs $20 just for the plan and I have no
clue how expensive it would cost for all the parts or
how detailed the plan is.
theirs hope!! ha

Yah it looks like most of the tunable lasers are geared to scientist.
And the cheapest one I found was $4,000. ha

I also found another plan.... might even be the same one?? but its cheaper.
TUNABLE DYE LASER PLAN - eBay (item 220260157735 end time Feb-11-10 14:48:03 PST)

I'm going to email the seller and ask him for an estimate of the parts cost.

 

[ElektroFreak]

You should also ask him for an estimate on how much the college degree costs that you'll likely need to build such a system..

 

[photonaholic]

I'd wager members here would email you the plans... support the forum instead.

However, someone correct me if I'm wrong, but the pumping system for a dye laser will be expensive to build and not for novices.

For now the only logical adaptation of what you wish to accomplish on a working persons budget is the have 3 modules firing into beam combining optics and turn the colors off and on to blend your custom colors.

With TTL modulation inputs on most "lab" style lasers it is super easy to control the color mix.

The guys on this forum have all the materials for you to build a RGB unit for a real affordable price.

There's a wealth of stuff right now in the for sale section.

 

[FireMyLaser]

Colour mixing is not at all the same as tunable waveleght. But if he wants just "artificial" wavelengths, or "colours" instead of a true wavelength then an RGB system should do the job.

 

[photonaholic]

Colour mixing is not at all the same as tunable waveleght. But if he wants just "artificial" wavelengths, or "colours" instead of a true wavelength then an RGB system should do the job.

The OP wanted to know why this is not found in pointers and light shows.

But I was just wondering if anyone knows why you don't see tuning
in many laser light shows or even laser pointers. To me it seams like
an amazing feature to be able to change the color back and forth isn't being used enough.

Is it the price?
Anyways I would love to know why it isn't used that much.
Or maybe it is and I just haven't seen it or have a misunderstanding as
to what laser tuning is. Do you think there is a way to make a home
made tuning laser?

And can laser tuning change wave lengths while the wave is running or
do you have to turn it off and then re-set it.

 

[HIMNL9]

I don't have complete plans, but i've found this article

Tunable Laser - Patent application - [Problems] To provide a tunable laser with high reliability and high performance, and of low cost

It have no pics, or at least my system don't show them, also if the article made reference to pics numbers (or, maybe, only registered users can view them) ..... anyway, the article itself is probably enough for give you an idea about the complexity grade and the difficults ..... not a hobby-grade work, imho

 

[Bluefan]

The rgb color mixing is a separate story. Real tuning you can find in lasers is possible because the gain medium has more than 1 wavelength where lasing is possible. This can be different wavelengths as with tunable HeNe or argon lasers, or a contious band where lasing is possible, as with dye lasers or CW Ti:Sapphire lasers. There are also tunable diode lasers, they also have a wide spectral range where the gain is high enough for lasing.

The wavelength selectivity is done differently for each laser, for the tunable HeNe lasers there's a tube with 1 brewster angle window, the other end has an OC for all wavelengths. HIMNL9's suggestion is nice, but incorrect. The brewster angle window isn't selective enough. The prism has 1 face under brewster angle, the other is placed so that the light is reflected back the same path. But the refractive index of the prism is different for each wavelength, so by varying the angle of the prism, separate wavelengths can be chosen because only that wavelength is reflected back at the right angle. The brewster angle window cannot be turned, this leads to losses for some wavelengths, but this is acceptable.
see also: here

Other lasers can use gratings because the gain is high enough that the losses are not a problem. Argon lasers use a prism too, not always a littrow prism. Dye lasers can use a grating, tunable diode laser too, but I'm not sure. I know spectra physics makes CW tunable ti:sapphire lasers, but I'm not sure if the use a grating or a prism.
As far as I know there are no tunable YAG lasers, although it has multiple gain lines. But doubling, as with green pointers, requires a special coated and cut KTP crystal, so for each line a different crystal is needed, or even easier, a different laser. So that's why you son't see tunable laser pointers, because unless you want a gas laser pointer or something similar or bigger in size, it's not possible.