Freezing Stuff With Fricken’ Lasers

For almost two decades there has been research that describes a method to freeze material with nothing but a laser. The techniques have only ever been able to work on single nano-crystals in a vacuum, making it less than functional — or practical. Until now, that is.

Researchers at the University of Washington have figured out how to cool a liquid indirectly using an infrared laser. It works by subjecting a special microscopic crystal to the laser. When the laser hits this crystal, the infrared light turns to the visible spectrum, becoming a reddish green light — which happens to be more energetic than infrared. This shift in energy levels is what causes a change in temperature. The energy (in the way of heat) is sucked from the fluid surrounding the crystal, and as such, causes a drop in the temperature of the liquid.

While our minds probably jump to making a freeze-ray, this breakthrough is more useful in biology, as it will allow researchers to freeze small amounts of tissue in order to better research biological & chemical processes in the body.

There’s a lot of interest in how cells divide and how molecules and enzymes function, and it’s never been possible before to refrigerate them to study their properties,

Now if only we could find out how to acquire that microscopic crystal… after all, it’s not that hard to build your own infrared CO2 laser using parts from a hardware store…

34 thoughts on “Freezing Stuff With Fricken’ Lasers

      1. Sounds like plain photon-phonon scattering:

        > Heat is transported out of the crystal lattice (across the solid–liquid interface) by anti-Stokes (blue-shifted) photons following upconversion of Yb3+ electronic excited states mediated by the absorption of optical phonons

        1. Phonons and photons don’t interact directly. But, phonons can impart (or take away) energy from an excited ion, thereby altering the energy of a radiatively emitted photon as the ion energy drops down to it’s ground state.

    1. It’s not a violation if you put energy in it.
      Just like a fridge generates heat by compressing the cooling gas, the laser here will generate heat to produce enough photons to have this effect. (it’s a non-linear effect, so you need lots of photons)

    2. Every (old incandescent) light bulb is turning heat into light :) Just ask Joseph Swan and Thomas Edison. It’s called black-body radiation, and is governed by the the Stefan–Boltzmann law which says that “the (radiated) power emitted per unit area of the surface of a black body is directly proportional to the fourth power of its absolute temperature”.

      So, hot means more – much more. “Power emitted” is in the form of electromagnetic radiation, also known as “light” when it’s visible. Of course, power is just the rate of conversion of energy from any one form to any other form (e,g, electrical to mechanical etc), or in this case from thermal to EM radiation.

      1. And thus, there are no green stars, just like there is no “green hot” metal from a forge or filament. Note: Edison’s carbon filament in a vacuum is sort of like back body, but black body radiation comes from a closed volume at equilibrium and you peek at it through a tiny hole. If the whole room were the temperature of the filament, you would have black body radiation from the Edison bulb -and you would not be able to see anything in the room but a uniform red or white or blue depending on temperature. Look through the peep-hole in a ceramic kiln at Cone 10 some time.

        Modern incandescent are not vacuum, they are slight pressurized with argon and use tungsten filaments. The heavy argon atoms prevent the tungsten from rapidly evaporating off the filament. There is strong convective cooling and definitely not black body behavior.

    3. I think I have to clarify my confusion about this process a little:
      I do know how a fridge works or how a lightbulb works (I even know how green dpss lasers produce green light by frequency-doubling).

      What blows my mind is, that this thing seems (to me) like it would allow you to transport heat/energy from a cold source to a warmer target.
      Thought experiment:
      I put these nano-crstals into a perfectly-clear container (of course there is no “perfectly-clear”, but you get the point) then i soround them with a layer of (warmer) flourescent material that “downconverts” the light.
      Now i start the process with some light.
      The crystals turn the light a shorter-wavelength then the flourescent material absorbs the resulting light and emits a lower-energy light back at the crystals (and “keeps” the diffrence as heat). rinse and repeat, you have now decreased the entropy.

      Now if the crystals take more photons to return a single one (like DPSS-Lasers) then they shouldn’t draw heat from the sorrounding area.

      1. The crystal absorbs thermal energy from it’s surroundings. The energy is transferred to phonons in the crystal lattice. Because the second harmonic of the near IR light requires two NIR photons to produce one second harmonic photon, conservation of energy is maintained and the universe is happy. The phonon energy of the crystal lattice alters the wavelength of the second harmonic photon.

      2. Just keep in mind that thermodynamics requires that you consider the entire system. In this case, the wast heat in the laser source and power supply, etc.

        If you could just use the light + crystal in the analysis, you will have found a method to cool the Earth – aim the “exhaust light” into space.

  1. that’s classical optical oscillators… you can “easily” make an OPO (optical parametric oscillator) and obtain a certain wavelength, but what is a pain is the beam quality

    I don’t think a supercontinuum has anything in relation to this as this is not at all the same process (while it is a very useful thing in itself)

    In the case of optical tweezers or optical freezong you have to obtain an extremely precise focus point which is hard because you can never go smaller than the original source of light which emitted the photons… as you need a relatively high power to trigger optical conversion/oscillation, you have to get a big initial emitter, which means you cannot focus to a tight point

    the real achievement is to manage to convert light at a power small enough with emitters small enough to be able to focus down under 100µm without aberrations

      1. Not that new actually, you can upconvert 782nm to 440nm by exciting a iodine cell, or even color centers in certain materials, but that was at humble powers or pulsed kilowatts, so yes this is a fascinating process!

      2. It’s not new at all. Second, third, fourth harmonic, wave mixing, self phase and cross phase modulation, non-linear (Stokes) processes, up-conversion (Anti-Stokes), and Raman shift are all well documented process.

        They just aren’t known by you. And the author of this article is using some trash online magazine targeted at pseudo-intellectuals for some reason intended to evoke some oooh-and-awe reactions from people that don’t know any better.

    1. I really cannot stand the pseudo-knowledgeable tone you’re trying to get across with these punctuation-free comments you keep making. Please buy a modern keyboard or get off the internet.

    2. As Jason said, you can definitely focus light to a smaller point than the source. The mode quality of the source only changes the efficiency of the focus, and although a single mode source can be focused to a tighter spot size, even multi mode sources can be used to generate harmonics through non-linear processes in crystals.

      I have personally machined sub-wavelength features in metals using ultra-fast pulses of 40MW peak powers.

      I see no evidence of super-continuum generation in the crystal in this article. The emission spectra indicates second harmonic generation only. The reduction in temperature of a type II cut nonlinear crystal at sub-optimal phase matching and polarization conditions has been known (but not well understood) since the mid seventies when picosecond mode-locked lasers became more readily available.

      And, from experience, generating a continuum in any material permanently destroys the material where the filament is formed and causes heating in the area. The result is a permanent change in the refractive index at that location due to crystal lattice damage. The one exception I can think of is gaseous or liquid super-continuum / high harmonic generation. But only gaseous generation gives useful light output when used in a carefully pressure controlled capillary.

  2. So freeze ray is totally possible. All you have to do is to shot somebody with shotgun loaded by frequency converting crystals. Then simply you’ll have to keep laser beam on him and wait enough time…

  3. “Now if only we could find out how to acquire that microscopic crystal… after all, it’s not that hard to build your own infrared CO2 laser using parts from a hardware store…”

    They are almost certainly not using a laser with that long of a wavelength. Since they are getting “reddish” light they are probably doubling 1342 or 1550nm. That would produce wavelengths from 671 or 775 which is generally visible, though 775 might be hard to see for some people.

  4. I wonder how difficult it would be to use this as a thermal imager. In theory, growing this crystal in a thermally isolated cell grid would be possible using current techniques. If the crystal absorbs thermal energy from its surroundings, focusing thermal energy on a crystal pixel array would mean any visible light illuminating the array would change color at the pixel site based on the radiation strength hitting the pixel. Basically, grow the crystal in an array. Shine an IR light on the array, record the reflection using a visible camera. The upconversion from IR to visible in each pixel will vary by thermal radiation.

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