[HN Gopher] Ph.D student demonstrates a single, working laser on...
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Ph.D student demonstrates a single, working laser on silicon
Author : croes
Score : 117 points
Date : 2021-11-29 18:24 UTC (4 hours ago)
(HTM) web link (brighterworld.mcmaster.ca)
(TXT) w3m dump (brighterworld.mcmaster.ca)
| 908B64B197 wrote:
| I'm extremely skeptical, because I've heard claims of silicon
| lasers for a long time but it never materialized.
|
| Also the article seems to plug unrelated scientists with vague
| affiliations to the University and a weird political spin to the
| whole thing regarding the author's home country's relationship
| with the US... despite it not being a US university.
|
| Weird.
| tzs wrote:
| > Also the article seems to plug unrelated scientists with
| vague affiliations to the University.
|
| The only other scientists I noticed were her supervisor and the
| coauthors of the paper on her research. Did I miss someone?
|
| > a weird political spin to the whole thing regarding the
| author's home country's relationship with the US... despite it
| not being a US university
|
| That was in the short biographical section at the end,
| describing where she got her undergraduate degree and how she
| ended up McMasters. It is hardly a "weird political spin" to
| note that she considered US universities but could not get a
| visa.
| spicybright wrote:
| I doubt GP would have even commented if she had a more
| typical bio.
| 908B64B197 wrote:
| > The only other scientists I noticed were her supervisor and
| the coauthors of the paper on her research. Did I miss
| someone?
|
| "Miarabbas Kiani's curiosity-based research is reflected in
| the story of another McMaster student. Donna Strickland
| received her BEng in Engineering Physics from McMaster in
| 1981 and went on to doctoral studies at the University of
| Rochester. Strickland's work on pulsed lasers with her PhD
| supervisor Gerard Mourou would lead to their Nobel Prize in
| Physics in 2018"
|
| I guess they wanted to have the "Nobel" keyword in there so
| they found the closest person to the institution (some
| undergrad from 40 years ago)?
|
| > That was in the short biographical section at the end,
| describing where she got her undergraduate degree and how she
| ended up McMasters. It is hardly a "weird political spin" to
| note that she considered US universities but could not get a
| visa.
|
| I just don't know if my alma mater would brag that "hey,
| since this guy couldn't get into somewhere else so he picked
| us!". I get that it's an undergrad's joke to laugh at "The
| Other Institute of Technology" but for a press release? The
| whole thing about the visa thing feels forced.
| allemagne wrote:
| The "weird political spin":
|
| >Miarabbas Kiani received her master's in electrical
| engineering from Shiraz University in Iran, where she
| specialized in photonic and optoelectronic devices. Encouraged
| by her supervisor to expand her academic horizons, she
| considered studying in the U.S. but was unable to obtain a
| visa. Her father suggested she think of Canada.
|
| Presumably, this is some sort of bizarre prompted response and
| it's a stretch to think Kiani was simply asked "why did you
| decide to study at McMaster University" and this was her actual
| experience.
| bredren wrote:
| I noticed this quote as well. It is pointed.
|
| You have to read further to see this happened in 2018.
| Presumably, this was directed at the policies of the
| executive at the time.
| 908B64B197 wrote:
| Indeed. I wonder if they would have mentioned it had her
| visa denial had happened in 2014 rather than 2018, during a
| certain administration...
|
| What's puzzling is that it's not a US University. I can't
| recall any US University press release about innovation in
| physics mentioning some foreign country's policy in a weird
| political ending. Maybe it's cultural?
| indymike wrote:
| Any press release that evokes a response of "oh yeah, my master
| he already has one and it's very nice-ahhh" is probably heavy on
| hype and light on substance.
| spicybright wrote:
| What do you mean master?
| dang wrote:
| " _Please don 't post shallow dismissals, especially of other
| people's work. A good critical comment teaches us something._"
|
| https://news.ycombinator.com/newsguidelines.html
| _Microft wrote:
| Paper: https://onlinelibrary.wiley.com/doi/10.1002/lpor.202100348
| dasudasu wrote:
| This is neither low cost nor commercially relevant. It's an
| exotic, low-temperature (so incompatible with subsequent steps of
| most wafer processes) deposition of rare earth material. The
| lasing wavelength is all wrong (1.9 um). It requires a pump laser
| in the 1.6 um range which is the usual range of interest. The
| efficiency is not very good. Couldn't find the linewidth while
| scanning rapidly. It's a run of the mill academic paper.
|
| There exist commercial electrically pumped lasers on silicon that
| are being continuously improved through different approaches.
| Intel is one of the leaders on that.
| fanzhang wrote:
| Is there not a single dimension in which the paper is novel? If
| not, it seems like a mistake to publish this.
| 908B64B197 wrote:
| Not really. It's a different approach with different
| tradeoffs that are just as bad as the previously known ones.
|
| That's probably why it wasn't picked up by a better journal
| and that nobody outside of the university where it happened
| is talking about it.
| echelon wrote:
| Not my area of expertise, but something can be academically
| novel and interesting without having any commercial or
| industrial applicability.
| amelius wrote:
| Isn't this what usually happens when the PR department of a
| university runs away with a story?
| redmare80 wrote:
| It's novel, it's a huge iteration in the space. But, it's
| also being misrepresented as more significant than it is due
| to the summary being friendly to laypeople.
| dogber1 wrote:
| And on top of that, you can make almost any material lase.
| There have been entertaining experiments where folks used
| yogurt, apple juice, hair dye, and other fun liquids in pumped
| lasers, exploiting some molecular band transition that was
| accidentally good enough.
| sleepysysadmin wrote:
| Breakthrough using extremely rare earth
| https://en.wikipedia.org/wiki/Thulium which comes at a high price
| and only provides a low power laser?
|
| Wierd that the article says its low cost. Certainly not a holy
| grail.
| jjk166 wrote:
| The term rare earth is a bit misleading. It's not rare as in
| uncommon, it's rare as in dilute.
|
| Rare earths are elements that don't form concentrated ores, and
| instead are spread diffusely in common rocks. Most soils
| contain between 0.4 and 0.8 ppm Thulium. Luckily Earth has a
| lot of rock, so in absolute terms there are still lots of rare
| earth material.
|
| The problem is that rare earths are mined by processing
| prodigious amounts of earth, typically the waste from some
| other mining activity. Like most large scale mining operations,
| it is labor intensive and environmentally destructive.
| Naturally this leads to such operations being located where
| labor is cheap and environmental regulations are lax. When
| people express concern about access to Rare Earths, they really
| mean access to materials from countries (often one specific
| country) with cheap labor and poor regulation.
|
| Thulium's expense is due to limited production, as there are
| few industrial uses for it and those applications that do
| utilize it tend to need only microscopic amounts, but with high
| purity.
| _Microft wrote:
| Thulium is only required in small quantities. Here is a back-
| of-the-envelope calculation: molar mass of thulium: 169g/mol,
| density: 9.32g/cm3, i.e. 0.055 mol/cm^3 [0]. That's ~ 3.3*10^22
| atoms per cubic centimeter.
|
| From the article: _A thulium ion dopant concentration of 4.0 x
| 10^20 cm-3 was measured using Rutherford backscattering
| spectrometry._ [1], i.e. a concentration of roughly 1 /100
| compared to pure material.
|
| Taking the first search result at face value, a cubic
| centimeter of 99.9% pure Thulium costs $85 [2]. Since the disks
| seem to have a diameter of 40mm, only a minuscule fraction of a
| cubic centimeter of material is needed for each.
|
| I would conclude that the material costs for these disks are
| not as large as initially assumed.
|
| [0] https://en.wikipedia.org/wiki/Thulium
|
| [1]
| https://onlinelibrary.wiley.com/doi/10.1002/lpor.202100348#p...
| (page 8, left column halfway down the page)
|
| [2] https://luciteria.com/metal-cubes/thulium-metal-cubes
| superkuh wrote:
| This laser requires a second laser to pump it in order for it to
| work. It's kind of defeating the point of things.
| m-watson wrote:
| A lot of lasers require a pump laser, it seems their argument
| is that this can be useful for low cost production in something
| like the telcom world.
| jacquesm wrote:
| Not really. Pumped lasers are the norm for quite a few
| materials that are hard to use as primary light source, but as
| a secondary lightsource they are plenty useful.
|
| Note that lots of other lasers are pumped as well, for
| instance, some lasers were originally pumped by flashing Xenon
| light from spiral wound flash tubes into Ruby crystal rods
| grown at great expense to get the gas to emit coherent light.
| The energy efficiency is important so that you don't end up
| overheating your secondary laser but the principle has plenty
| of uses and isn't even restricted to using light as the
| starting point.
|
| One possible way to use this is to use a somewhat higher power
| laser to illuminate a substrate at right angles to the desired
| outputs, which would allow for a hybrid where only the primary
| is made with exotic materials and the remainder can be made in
| Silicon. Right now _every_ laser output needs to be on a
| physically different die than the Silicon based circuitry that
| drives it, this technique could do away with that intermediary
| step substantially reducing the costs of certain
| telecommunications devices.
|
| Finally, once something has been pushed to lase it usually
| doesn't take very long before improvements are made that allow
| it to do so cheaper, faster or independent of the original
| light source, it is that first step that is the really hard
| one.
|
| One joke I heard from someone who is deep inside laser research
| is that when all is said and done there are probably not a
| whole lot of substances that can't be made to emit coherent
| light, the trick is to find out how to do it in the first
| place, and then to do it repeatedly and affordably.
| ourmandave wrote:
| The real test will be if they can mount it on a jet and do a fly-
| by to fill an entire house with popcorn.
| oneshoe wrote:
| Deep reference! This comment made my morning. Thank you!
| beckingz wrote:
| Silicon photonics (microchip lasers and particle accelerators) is
| an active area of research that has had some promising
| improvements lately.
|
| Research like this is likely to result in a laser miniaturization
| breakthrough like that of MEMs sensors, which will have big
| impacts if the money and energy cost of a putting a laser on a
| device drops to near zero.
|
| Great talk on the state of the art:
| https://www.youtube.com/watch?v=t5EPeuLxaE0
| savant_penguin wrote:
| Really cool, but the article could show a picture of the actual
| laser light (maybe it's not visible light?)
| hellbannedguy wrote:
| Or at least a clear picture of the dime.
| jacquesm wrote:
| It appears to be emitting in the IR part of the spectrum (1.9
| um).
| spoonjim wrote:
| > Encouraged by her supervisor to expand her academic horizons,
| she considered studying in the U.S. but was unable to obtain a
| visa.
|
| >
|
| > Her father suggested she think of Canada.
| msie wrote:
| I'm skeptical of university press releases. Is this the "holy
| grail" as they claim it to be? :D
| crispyambulance wrote:
| It might very well be a big deal.
|
| This has been done with Indium Phosphide (InP). In fact,
| lasers, modulators and supporting circuitry have have been
| integrated together on InP in what is usually referred to as
| "Photonic Integrated Circuits". Infinera has been doing this
| for ~20 years. The drawback is you need a very specialized InP
| fab (which ultimately means high-cost and low volume).
|
| If similar stuff could be done on ordinary silicon, that
| changes the game and opens up a huge range of possibilities.
| slownews45 wrote:
| Does it need to be ordinary silicon, or ordinary silicon
| processes (including temperature?). One seems much easier
| than the other, the later seems much more likely to be cheap
| (I can build a big laser on ordinary silicon today). Much
| harder to do with ordinary silicon in a somewhat standard
| process flow.
| klyrs wrote:
| To be fair, it's a "holy Grail" of the very niche field of
| photonics. On the other hand, the lack of easily-integrated
| lasers has been a major hurdle to photonics becoming anything
| other than a niche field.
|
| After all, the first transistor wasn't remotely competitive
| with existing vacuum diodes in use at the time.
| timdellinger wrote:
| I'll also add that "holy grail" type discoveries tend to be
| published in higher tier journals than this one.
| bell-cot wrote:
| For a so-so discovery, you need the cred of a high-tier
| journal far more than they need your paper.
|
| For an actual holy grail, ~every journal in the field needs
| the cred of your paper far more than you need them.
| bredren wrote:
| If you have a holy-grail, do journals like Nature do things
| to try to lure you into publishing with them instead of the
| one this author chose?
| jacquesm wrote:
| This is exactly what should stop, so if this is the case of
| someone publishing an actual breakthrough in a lower tier
| journal then that should be encouraged, rather than punished
| by outright dismissing the contribution based on where it is
| published.
|
| Otherwise we'll never get rid of those cartels.
| wanderingmind wrote:
| That's like asking smart programmers should stop working
| for FAANG and work for minimum wage at a non-profit, to
| help save the world. The academic perks at multiple levels
| are deeply tied to publishing in top tier journals. It's
| not going to change unless there is a wholesale
| reorganization of incentives, which is unlikely to happen.
| Open sourcing the research publications for taxpayer funded
| research is probably what we can strive to achieve.
| earthscienceman wrote:
| Ehhhh. Not at all true. Or at least that's maybe 50% true.
| Many high impact papers in my field, including "holy grail"
| type papers, have been published in "low tier" journals. Some
| scientists would much rather publish quality research in a
| timely manner than go through the Nature review process and
| waste a lot of their time. It's extremely dependent on the
| disposition of the lead author.
|
| For the record I can't at all speak to the quality of this
| research paper, I'm only trying to address this comment
| specifically.
| SubiculumCode wrote:
| So true
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