Laser-based device can scan almost any sample of gas and tell you what's in it

[aj7]

People can’t even tell how much cheap oil is in olive oil, let alone “extra virgin olive oil” vs. el cheapo olive oil. Take it from this old laser spectrocopist. When there’s 75 mirror mounts on a 4 foot by 8 foot table, with a Chinese graduate student handcuffed to the table to adjust them, it’s at least a decade away. When you can buy a frequency comb laser on Aliexpress, now we’re talking.

[kylehotchkiss]

Why did you handcuff a grad student to the table?

[Eduard]

searching for "frequency comb laser" on Aliexpress doesn't yield fitting results currently for me.

https://de.aliexpress.com/w/wholesale-frequency-comb-laser.h...

[j45]

Available on Aliexpress really is a solid indicator.

[zerealshadowban]

It seems that the frequency comb laser is easy to diy! "NIST Shows How to Make a Compact Frequency Comb in Minutes" (2013) [0]. I can think of many applications apart from the medical diagnosis they talk about.

The varying mirror cavity is today's innovative step, plus the computation to identify atoms and molecules from the observation of color absorption.

[0] https://www.nist.gov/news-events/news/2013/07/nist-shows-how...

[aj7]

Yes. And a surgeon can remove your appendix in minutes too. A 777 can be landed in a crosswind, in minutes. Why a pass can be intercepted and run back for a touchdown in seconds! All of this easy. I’ve seen it on TV, even.

[aantix]

If you wanted to identify the components of a liquid, could you heat it and analyze the steam?

[kurthr]

Usually, they use HPLC (high pressure liquid chromatography), which uses a solvent and packed diffusion columns.

[rubicks]

You don't have to stop at the gas phase.

https://en.m.wikipedia.org/wiki/Inductively_coupled_plasma#A...

[Keyframe]

if it can survive phase transition untouched. otherwise, if there'd be a chemical change, you'd be looking at something new.

[WhyNotHugo]

Different components might vaporise at temperatures.

If you heat water and alcohol to 80°, measurements would indicate ~100% alcohol.

You won’t know the right temperature unless you know what substance it is.

Edit: I guess you might also have stuff which reacts below their vaporising temperature.

[egberts1]

Every phase transistion (or phase change) of a molecule alters its emission lines, at least as detected by gas chromatography equipments.

[DecentShoes]

Man, the next Vessyl is going to be intense...

[aj7]

You could taste it.

But working on a good dog interface is the way to go.

[rz2k]

I wonder how the mirrors are cleaned or kept clean. Maybe that isn’t an issue when detecting concentrations that would take a mile of light to measure, and existing NDIR detectors are sufficient for things like detecting different gasses in pollution.

It would be nice if there were general purpose gas measurement sensors that could identify more gasses rather than being specialized to a specific gas. Could this be done by replacing the circuitry of a typical evaluation board with an interface to something like an NVidia Jetson Orin Nano?

[jmusall]

You usually mount mirrors vertically so dust does not settle on them that much (also it is safer to keep laser light propagating horizontally at only one height). Additionally, overhead ventilation is often installed which provides a vertical Laminar flow of dust-free air. If you have to clean the mirrors eventually, you'd use compressed (clean) air or special mirror cleaning wipes. Thorlabs (lab supply company) has a detailed guide on optics cleaning[1]

[1] https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=90...

[condensedcrab]

Usually cavity mirrors would be somewhat sealed to prevent dust/junk build up.

Problem with general purpose spectroscopic measurements is that you need a broadband source and detector. This adds complexity compared to a targeted wavelength range.

[pjs_]

It has been possible to buy pretty nice handheld Raman spectrometers for a while now:

https://www.bruker.com/en/products-and-solutions/infrared-an...

This paper is obviously trying to go much further. But if you just want to buy a tricorder, you can

[multimoon]

I was unable to find a specific price for the model you linked in my few seconds of looking but these devices generally run in the $10,000 USD range, so I don’t think it’s achieved the “if you just want to buy it” territory yet.

[ck2]

Shame this won't work lightyears away

very hard to detect oxygen around exoplanets apparently but they came up with a new method recently

https://news.ucr.edu/articles/2020/01/06/scientists-develop-...

[xeonmc]

Similar concept to FTIR in terms of de-convolving a known agitation pattern to enable more robust signal collection.

[dv_dt]

It would be great to sample plastic and get composition sufficient to determine a recycling category

[bluGill]

We already do that. However not all plastics and be determined that way. Black plastic in particular often cannot be figured out (since the laser as absorbed) and so even if the plastic is easy to recycle it is often land filled.

There are open questions on if recycling plastic is worth bothering with at all, but that is a different debate.

[klysm]

We do this already, but also for metals which have a much more reasonable recycling story. In metals though, we use LIBS. Tomra makes the best machines currently

[TuringNYC]

>> It would be great to sample plastic and get composition sufficient to determine a recycling category

i love this idea. i cant believe how tiny the marked recycling categories are on the containers, i can barely see them. i always wondered how they even achieve this at the town recycling center.

[preezer]

So you build the tester from plankton? 99 % evil 1% hot air or the other way around ^^

[amelius]

Can it detect medical disorders, similar to how (according to popular belief) dogs can smell cancer?

[akomtu]

Can it detect the amount of PFAS in tap water?

[reaperducer]

Laser-based device can scan almost any sample of gas

Oh, sure, it can tell you who smelt it. But the real money is in figuring out who dealt it.

[01100011]

Now can we use this to do smog checks on cars as they drive so I can avoid the biennial chore of taking the car in to a shop?

[PaulHoule]

I remember people from Sandia National Labs using LIDAR to monitor pollution around Albuquerque circa 1990. Turns out this been a thing for a long time:

https://ntrs.nasa.gov/citations/19720026861

and is still going on

https://iopscience.iop.org/article/10.1088/1748-9326/ab9cfd

https://idstch.com/security/lidar-technology-revolutionizing...

I think in those cases you know what the pollutant is that is in a gas that you know what it is and want to make a quantitative determination whereas the system described in that paper is supposed to make sense of some random gas.

[datadrivenangel]

In Virginia they do this! They have devices that they'll put near highway on/offramps and rotate them between locations every few weeks or so.

[idontwantthis]

Do they still actually analyze the gas? When I did mine they just plugged into the computer and it was done in 10 seconds.

[BobaFloutist]

No, I want to add headlight lumens/angle checks and window tint checks to the smog check. It's an annoying chore but it's the one time car owners have to (semi-regularly) get their car looked at, we should take advantage of that.

[mannyv]

Contamination?

[Beijinger]

Sounds trivial. Without opening the link, let me guess: QCL?