Flexible Dye Laser Using CLCEs

[H2Oxide]

Or at least that's what I can make of it.

Tunable lasing in cholesteric liquid crystal elastomers with accurate measurements of strain

From what I can tell with my quick skim of the article is they're altering the physical structure of the medium, and thus tuning the wavelength.

What are your thoughts on this?

 

[H2Oxide]

Seriously, no one?

 

[Isaac Clarke]

i read through the article.... the process seem complicated and the article don't tell us the efficiency of the system,the cost pros.....so on

 

[H2Oxide]

i read through the article.... the process seem complicated and the article don't tell us the efficiency of the system,the cost pros.....so on

I think it's more of a proof-of-concept, I can't really see too many uses for this, and dye will probably be a dead medium within the next few years anyway. It also looks like it doesn't use cavity mirrors (for the dye), so it must be lasing superradiantly, which isn't really that complicated (you can do it with a homebuilt nitrogen laser, a lens and a cuvette full of dye). The concept of solid state dye lasers is nothing new, however I though the fact that the medium itself acts like a BRF and that it was flexible was interesting. It is odd that they don't include output power though.

 

[planters]

You can substantially alter the lasing wavelength by simply changing the solvent polarity ie hexane to methanol. Ph will shift some dyes and temperature will shift all of them.

The solvent is realy part of the dye system.
I have never understood the push to solid state. There are usually alternative materials with superior qualities and with so many, along with non-linear mixing, the wavelength coverage is pretty good.
I still think the low cost,cooling and high power will keep liquid dye around for some time

 

[Deleted member 13229]

Very cool article, thanks for posting! Liquid crystals are SO cool! For one, a single compound can undergo several phase transitions, and especially in the case of these chiral LCs, messing with the solvent system can give massive changes in the physical and optical properties of the crystal.

The typical FWHM of lasing emission from the CLCE film was ~0.25 nm.

I found this quote pretty interesting. From what I know, simple dye lasers usually have much broader spectral emission than this (unless corrected with bragg gratings or something similar IIRC).

I'd love to have a tunable laser over a fairly large range of wavelengths....

 

[H2Oxide]

You can substantially alter the lasing wavelength by simply changing the solvent polarity ie hexane to methanol. Ph will shift some dyes and temperature will shift all of them.

I knew pH would shift them, didn't know temperature would shift them as well though. Why is that? I can't find anything online.

The solvent is realy part of the dye system.
I have never understood the push to solid state. There are usually alternative materials with superior qualities and with so many, along with non-linear mixing, the wavelength coverage is pretty good.
I still think the low cost,cooling and high power will keep liquid dye around for some time

I can see why we'd push SS dye, lower toxicity and a heck of a lot less work and mess. While they might not provide as big of a spectrum, I can't think of any applications that demand a continual spectrum >20 nm. SS dye could still provide compact tunability over almost the entire spectrum (depending on dye and material of course). As for superior materials, the only thing I can think of that can lase around 600 nm is praseodymium, and I don't know if you saw the last thread on that, but it sure has its drawbacks.

Very cool article, thanks for posting! Liquid crystals are SO cool! For one, a single compound can undergo several phase transitions, and especially in the case of these chiral LCs, messing with the solvent system can give massive changes in the physical and optical properties of the crystal.


I found this quote pretty interesting. From what I know, simple dye lasers usually have much broader spectral emission than this (unless corrected with bragg gratings or something similar IIRC).

Yes, especially without internal tuning. Without a BRF or something in the cavity they can have a spectrum spanning tens of nanometers AFAIK.

I'd love to have a tunable laser over a fairly large range of wavelengths....

You should work with planters, he seems to be a bit of a dye nut.

 

[Deleted member 13229]

I actually have been working on a dye laser recently...my photonics professor at my university gave me the green light to do whatever with an old continuum surelight dye laser setup that he inherited from an old lab. The pump is a Q-switched Nd:YAG with removable harmonic generators, but we have no dye to pump so I'm going to synthesize some rhodamine 6G over my break. It turns out a lot of the laser dyes are relatively simple organic molecules with easy synthesis routes.

A bit OT but dyes can also be flashlamp pumped...maybe if I get around to it this winter break I'll see if I can optically pump some laser dyes with photoflash powder and see if I can get it to lase.

 

[H2Oxide]

I actually have been working on a dye laser recently...my photonics professor at my university gave me the green light to do whatever with an old continuum surelight dye laser setup that he inherited from an old lab. The pump is a Q-switched Nd:YAG with removable harmonic generators, but we have no dye to pump so I'm going to synthesize some rhodamine 6G over my break. It turns out a lot of the laser dyes are relatively simple organic molecules with easy synthesis routes.

Shame the laser isn't CW. When you say "generators" do you mean is has more than just the second harmonic? 355 or 266 perhaps?
Also the synthesis sounds like an interesting project. Can you order from Sigma or does your university already have everything you need?

A bit OT but dyes can also be flashlamp pumped...maybe if I get around to it this winter break I'll see if I can optically pump some laser dyes with photoflash powder and see if I can get it to lase.

I think this is how their emission spectrum is determined and measured. It'd be cool to spectro it untuned if you get it working

 

[planters]

The temperature shift in florescence wavelength is probably due to the increasing viscosity of the solvent and the effect on vibrational states that are in turn based on the flexing of the dye molecule.

https://books.google.com/books?id=6rTrCAAAQBAJ&pg=PA171&lpg=PA171&dq=fluorescence+efficiency+with+temperature+dye+laser&source=bl&ots=yVkkHfKPA-&sig=I5nV61m8Za1EvuNehv6zFOJ_2ag&hl=en&sa=X&ved=0ahUKEwiAl8nIuYzKAhUCPz4KHbUIBZUQ6AEINjAC#v=onepage&q=fluores

I can see why we'd push SS dye, lower toxicity and a heck of a lot less work and mess.

I work with dyes a lot and I think this is overrated. If you treat the dye cell and the interconnects with anything approaching the care that you would use to handle a multi thousand dollar laser crystal the leakage will be rare

These solid state dyes wear out. Unlike a SS crystal, even if you do not damage the medium, the dye degrades due to the exposure to pump light. This occurs on a time frame that matters. Energy of mega to even giga joule/mole is typical, but when you do the math and realize how small a fraction of a mole a "solid state" dye laser contains and that it can't be refreshed then liquid state becomes attractive.

A bit OT but dyes can also be flashlamp pumped...maybe if I get around to it this winter break I'll see if I can optically pump some laser dyes with photoflash powder and see if I can get it to lase.

Have you ever tried to pump a dye with a flash lamp? It's surprisingly demanding. It is not hard, there are YouTube videos of it being done (including my own), but the magic is in the peak energy. The eye will not distinguish a 1kJ,usec and a 1kJ,msec pulse although the usec pulse, which has 1000 times the peak energy, may look a little bluer, the appearance is subtle. Photo flash powder will be very slow and as a chemical reaction will be likely to be much cooler than the 8,000 to 20,000K temperature required of a flash lamp that can pump a dye.

The dyes will florescence over an extended range as will a ti sapphire, but if the cavity optics are narrow band or if you insert a BRF or even a dispersing prism you can force the laser, as an amplifier, to output close to the same amount of energy wherever you want within that band. You can also blend dyes( the xanthenes are used this way all the time) or replace a dye solution with another and select other bands to amplify.

For laser pumping the harmonics are needed and the Q switching helps a lot. Without Q switching you need to focus a CW laser such as an ion or a 532 to a really tiny spot, microns across and then align the cavity optics to cause the dye laser beam to coincide with this tiny place to obtain efficient pumping. Fluence of 20-30kW/cm2 is about a minimum and the best flash lamp systems might get to 100kW/cm2 while a Q switched pump laser will easily reach 2MW/cm2.

My link is stuck. Try to Google tempreture effect on flouresence of laser dyes. There are a lot of hits.

 

[thebouljello]

This article was interesting, although some things were difficult to understand. I find it interesting how the laser can achieve such a broad range of wavelengths by adjusting the pitch of the CLCE.