[HN Gopher] World's Shortest Wavelength Laser Diode Emits Deep U...
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World's Shortest Wavelength Laser Diode Emits Deep UV Light at Room
Temperature
Author : bookofjoe
Score : 69 points
Date : 2020-01-19 16:16 UTC (6 hours ago)
(HTM) web link (iopscience.iop.org)
(TXT) w3m dump (iopscience.iop.org)
| Zenst wrote:
| This is good, the usage for UV is huge and anything that reduces
| costs will only help.
|
| Whilst many don't need it, I'm sure having a UV filter of your
| water would not go amiss.
| fsh wrote:
| DUV LEDs have existed for quite a while and produce a lot more
| power.
| lightedman wrote:
| UVB/UVC LEDs barely touch 2% efficiency converting energy
| into photons. When they can hit 30%, I'll have the perfect
| mineral hunting lamp designed and built.
| robocat wrote:
| > I'm sure having a UV filter of your water would not go amiss
|
| You don't need lased light for that (and using a low
| efficiency, high cost device also not ideal?!).
| amluto wrote:
| UV LEDs seem to be in development. The problem with UV
| fluorescent tubes is that they have horrible cycle life.
| pg_is_a_butt wrote:
| More like in production for years. What do you think powers
| those "instant curing glue" lights that have been helping
| old ladies glue together their purse straps for over a
| decade.
| dbtx wrote:
| I guess everyone means UVC here. A UVA flashlight is
| cheaper than lunch ;) edit: my facts were scrambled. C is
| the nasty one... maybe my favorite (unsafe) language will
| help me remember that from now on.
| m-p-3 wrote:
| Or maybe for photolithography hobbyist.
| jjoonathan wrote:
| Yeah, especially because that hinges on having coherent
| light, whereas sterilization does not AFAIK.
|
| As for incoherent UV light, I wonder how this laser compares
| in efficiency to arc lamps. Is that still how incoherent UV
| is generated? Deuterium and mercury vapor? Or have LEDs taken
| over?
| Zenst wrote:
| A solution that does not use mercury, then that will make
| for cheaper and equally safer production and dispose.
| fsh wrote:
| DUV for lithography is usually produced with excimer lasers
| at 248 or 193 nm. While they are technically lasers, they
| are barely coherent and have horrible beam quality.
|
| For other applications such as sterilization or curing
| adhesives, mercury vapor lamps and LEDs are popular.
| pressurefree wrote:
| or super lo-po phosphorescent LEDs
| anonymfus wrote:
| Is photolithography at home limited by laser'd wavelength?
| hanniabu wrote:
| Would be very useful for vitiligo treatment.
| [deleted]
| cies wrote:
| > I'm sure having a UV filter of your water would not go amiss.
|
| UV "filter"? I thought the UV thing in water treatment was
| merely to kill most (if not all) of what micro-life would
| otherwise still live in yr water.
|
| Filters are needed to actually get some (dissolved) solids
| --possibly UV-zapped micro org corpses-- out of yr water.
|
| Most places add chlorine/chloramine to the tap water to prevent
| micro orgs becoming so prevalent "at the faucet" that you can
| get "cannot go to work tomorrow" sick.
| zdragnar wrote:
| Yes, if you live in an area with municipal water treatment,
| but if you rely on a private well, accessible and inexpensive
| UV treatment would be great. Of course, you also (generally)
| need a water softener and perhaps more expensive filtering
| equipment depending on the what metals and minerals might be
| present.
| mrpeanutbutter wrote:
| Handheld UV water purifiers are already common. A lot of
| backpackers use them. I'm not sure how they work. Presumably
| they're not using LEDs.
| analog31 wrote:
| They use mercury lamps. I took one apart to use the lamp as a
| wavelength standard. Don't try that at home, the sterilizers
| have interlocks to prevent accidental eye and skin exposure.
| ruslan wrote:
| Even more, they are getting pretty close to x-ray now which
| begins at 10nm.
|
| The laser structure was grown on the (0001) face of a single-
| crystal aluminum nitride substrate. The measured lasing
| wavelength was 271.8 nm with a pulsed duration of 50 ns and a
| repetition frequency of 2 kHz.
| rubidium wrote:
| In the atomic research world, diode lasers are great because
| they're cheap and fairly tunable.
|
| Many of atomic cooling studies done 20 years ago were done using
| rubidium because it had a primary absorption wavelength that
| matched what commercial CD players used. This made the 780nm
| diodes dirt cheap.
|
| Having new wavelengths of diode lasers makes certain basic
| research more accessible. I've been out of the field too long to
| know where this one may help but it's exciting to see progress.
| fsh wrote:
| Nowadays in atomic physics frequency-quadrupled diode lasers
| are commonly used for accessing DUV wavelengths. They produce a
| lot of power and have narrow linewidths, but are very expensive
| (>> 100kEUR). Here is a chart from one manufacturer that shows
| commonly accessed transitions:
| https://www.toptica.com/fileadmin/Editors_English/15_downloa...
|
| In the paper the authors only demonstrate pulsed operation of a
| bare laser diode. To make it usable for atomic physics, they
| would have to achieve continuous-wave operation with feedback
| from an external cavity. This might be pretty difficult to do.
| xellisx wrote:
| But can I use it to burn things?
| dhabxkxbx wrote:
| What does "Burn" mean?
|
| Break the bonds of just about anything except fluorides and
| metals? Probably.
|
| Deposit enough energy I locally heat the material above it's
| auto ignition T? Well that's a flux question
| xellisx wrote:
| Yes, to raise the temperature of a material in which ignition
| can occur.
|
| I know the cheap hobby laser machines use a 405-450nm module,
| which works decent on stuff like wood. Now since it's about
| half the wavelength, is it more affective in cutting /
| etching these materials with a lower optical output power.
| wbl wrote:
| That's just straight up energy transfer. Doesn't matter
| exactly what wavelength you use provided you dump enough
| energy in, and this one is so inefficient it doesn't make
| sense.
| semi-extrinsic wrote:
| If you look at CO2 lasers, at 40W ($350 on eBay) you can
| cut plywood, at 150W ($5000 on eBay) you can cut metal.
| Both of those are 1040 nm.
|
| The 450 nm modules you can get up to 5W ($100 on eBay), but
| those can hardly cut anything, they're more like engravers.
| [deleted]
| mdturnerphys wrote:
| CO2 lasers are typically at 10.6 microns. They can cut
| metal but you need at least 100W and RF pumping. Metal-
| cutting lasers are more commonly fiber lasers with
| wavelengths of ~1050nm.
| dhabxkxbx wrote:
| " is it more affective in cutting / etching these materials
| with a lower optical output power."
|
| Probably because it's more likely to be absorbed.
|
| On the other hand, absorption can't be > 100%. So a longer
| wavelength laser an cut just as well for the same power as
| long as the mtls absorbs all the photons
| dang wrote:
| This looks like a great HN comment, but could you please stop
| creating accounts for every few comments you post? We ban
| accounts that do that. This is in the site guidelines:
| https://news.ycombinator.com/newsguidelines.html.
|
| HN is a community and we want it to remain one. For that,
| users need some identity for others to relate to. Otherwise
| we may as well have no usernames and no community, and that
| would be a different kind of forum. https://hn.algolia.com/?q
| uery=by:dang%20community%20identity...
|
| You needn't use your real name, of course.
| dhabxkxbx wrote:
| " This looks like a great HN comment, "
|
| Thank you. I thought it was rushed w/out the explanation
| that it deserves (it has fascinating implications about the
| lack of the color blue in nature). Also, I felt it came out
| as snarky or arrogant, which I didn't intend. But I was
| juggling other things :S
|
| Unfortunately, I'm afraid you'll have to ban me. I've
| abused the site far too long but I also have no intention
| to expose myself w/ a profile (any user with a karma > 1000
| is trivial to dox).
| api wrote:
| Does this have any implication for chip fabs? Right now EUV
| requires crazy Rube Goldberg machines using tin plasma or
| something like that, which is insanely expensive.
| hwillis wrote:
| EUV is 20x smaller wavelength, 10000x higher power, and far
| larger area
| balaclava9 wrote:
| Who is the lead writer of this paper? According to google Ziyi
| Zhang is a famous Chinese actress.
| Gene_Parmesan wrote:
| Zhang is an extremely common Chinese family name, so I wouldn't
| be surprised to see a lot of people with the same name.
| rubidium wrote:
| Likely not the same person. From the article:
|
| Author e-mails zhang.zc@om.asahi-kasei.co.jp Author
| affiliations 1 Innovative Devices R&D Center, Corporate
| Research & Development, Asahi Kasei Corporation, Fuji, Shizuoka
| 416-8501, Japan
|
| 2 Center for Integrated Research of Future Electronics,
| Institute of Materials Research and System for Sustainability,
| Nagoya University, Furo-cho, Chikusa-ku, Aichi 464-8601, Japan
| orbital-decay wrote:
| I'm sure some of the people named Will Smith are scientists.
| howardD wrote:
| Normally, in LEDs and solid state lasers, there is a direct
| relation between wavelength(energy quantum) (electron-Volts) and
| operating voltage (Volts).
|
| For example Red = 660 nanometers = 1.8 electron-Volts = 1.8
| Volts, which is the typical operating voltage for a Red LED.
|
| Blue = 470 nm = 3.3 eV = 3.3 Volts operating voltage.
|
| So: Deep UV (270 nm) is supposed to operate on ~4.6 Volts.
|
| But article mentions 13.8 Volts. I wonder why there is such a
| huge gap?
| lightedman wrote:
| I'd wager that they're just using a pulsed array of three LEDs
| in series to get their required photon output. Typical for
| solid state lasing.
| jpmattia wrote:
| > _But article mentions 13.8 Volts. I wonder why there is such
| a huge gap?_
|
| I'm spitballing here, but I'd guess that the difference is due
| to a resistive drop across one or both of the contact layers.
|
| In the article, Fig 2 says that they have 0.5A flowing with a
| pulse width of 50 ns and a pulse rate of 2 kHz. Their duty
| cycle is then 1/10000, so that's a lot of current flowing
| during the active part of the cycle. I haven't found all the
| details about the dimensions and doping, but any small amount
| of resistance might cause enough potential drop between the
| contact and the lasing region to account for the difference
| (especially that side contact to the bottom n-type layer.)
| fsh wrote:
| The bands of laser diodes are not necessarily sharp, so there
| can be a significant difference between the injection voltage
| and the photon energy. The paper mentions that their particular
| doping method produces a step-less valence band profile.
|
| Furthermore, they need a fairly large current (0.4 A) to get
| this thing to lase. The "knee" in the U-I curve is at around 9
| V and 0.05 A, so there seems to be a fair bit of voltage drop
| due to internal resistance of the device. This is probably also
| why they have to pulse the laser with a 0.01 % duty cycle in
| order not to produce too much heat.
| MayeulC wrote:
| By sharp, do you mean a direct band-gap?
|
| I recall that you sometimes want to pump your atoms in a
| higher energy state than the one that corresponds to the
| output energy, but I forgot its usefulness. Could someone
| enlighten me on this? Or is it just for optically pumped
| mediums (thus pumped with higher energy photons than the
| emitted ones)?
| fsh wrote:
| It is impossible to achieve inversion (and therefore gain)
| by optically pumping a medium exactly at the emission
| wavelength. Therefore, optically pumped laser gain media
| are at least three (usually four) level systems.
| itcrowd wrote:
| Based on the abstract, it is a pulsed system (in contrast to
| continuous wave LEDs) so I think there is a bias voltage of
| 14V.
| throwawaycanada wrote:
| Three laser diodes in series, electrically?
| sansnomme wrote:
| Down conversion perhaps?
| aurelwu wrote:
| I'm not sure if that has any meaning, as I know nothing about
| lasers, but 4.6 * 3 = 13.8 , could be pure coincidence.
| [deleted]
| bookAlot wrote:
| Is this supposed to be or sound like a good thing? Sounds
| dangerous as heck.
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