Nanosecond Laser! Over-driving the worlds most powerful visible Laser diode!

[@RobertJGowans]

Fantastic, this is really cool to see. I work for Lightware Lidar, and our bread and butter is pulsing laser diodes really hard for miniscule periods of time (for the purposes of range finding), so this hits really close to home for me. I also love that long exposure of the beam at different distances, you can really make out its profile.

[@LesLaboratory]

That sounds awesome! I'm curious what kind of pulse widths and peak powers do they get out of those for Lidar?

[@RobertJGowans]

@@LesLaboratory We use 905 nm diodes with pulses of ~20 ns @ 20 kHz. I think our peak power is ~10 W, with the average being 2.5 mW.

[@bussi7859]

My pulsed range finder did run at 10kHz and its range was 6km. Used in the SAAB Training System weapons simulator BT 41, 53, 56.

[@LesLaboratory]

Sweet! I have an ex MOD rangefinder under the bench. One day I will dust it off an do something with it!

[@MathewMoss-fp9ju]

Id love to see more quantum entanglement experiments and wish i could test a theory with using a GAGG crystal instead of dye

[@LesLaboratory]

It's something I aim to get around to, probably with BBO (if I can afford one) but after that, I will be looing at less expensive materials to try.

[@matteo234321]

Jim Williams lives on in many ways ,good to see another. Great Video!

[@LesLaboratory]

Yep, I'm just standing on the shoulders of giants. Thanks!

[@LutzSchafer]

Something like that was part of my masters work 40 years ago. I used coax cable as load lines. This gives an almost perfect rectangular waveform of the diode current. The length of the load lines defines the pulse width.

[@LesLaboratory]

Awesome! There is a screenshot of a paper towards the end of the video, where a coax is used to customise the pulse width.

[@InTimeTraveller]

Hi, I'm a test engineer and I find your experimental setup and your entire experiment incredibly useful! I have been trying to puzzle out for months how to measure pulsed laser diodes and what equipment I can use there (I haven't been able to find very short rise time transimpedance amplifiers), so the average power method and back-calculation of peak power seems very insightful, thank you! However, for the love of God (and I know I'm just a random person on the internet but I'm also an electronics engineer with a passion for signal integrity and proper layout techniques), do NOT split the ground planes and place just a single pour ground plane over your entire board. It will improve your noise a lot. I don't know who in the literature suggested to put these R7-R11 resistors there and for what reason, but the split plane underneath the resistors is gonna create a very strong EMI that will radiate everywhere. Moreover it will add inductance to your dI/dT loop which in your case is from point C to H1.2 to the laser diode, then back through H1.1 all the way to the GND of Q1. This loop should ideally have a *uniform* ground plane underneath and be kept as short as possible to minimise EMI (both radiation and pickup).

[@LesLaboratory]

Excellent, you are welcome! I am not a test engineer, so good advice like this is always welcome! The bottom plane under the PFN likely contributes significant capacitance, slowing things down as well I imagine, diode leads could be shorter, and the FMMT415 could be used in place of the ZTX415.

[@InTimeTraveller]

@@LesLaboratory the bottom plane doesn't add as much capacitance as you'd think because you have a two layer board so the ground plane is really far away from the signal layer (since this is a two layer board and the gnd is in the bottom layer which is usually 1.2-1.6mm thick) and because the ground plane split that you have is very minimal. That said, from an electrical engineering perspective the most important thing for a pulse forming network is not necessarily low impedance or inductance, but impedance matching of the transmission line and the source impedance (and ideally the load impedance as well). So my point is, you can put a solid ground plane underneath and then calculate via your EDA software the trace width that you would need to achieve a specific impedance (say 50Ω or sth). Having a signal pass over a split plane is a big no no in PCB design because that spot there is acting as an antenna and it both receives and emits radiation (which is harmful both to other devices nearby and to your device if it picks up stray signals). Moreover the extra zero ohm resisors are adding inductance to the loop and that both increases the rise/fall time and it can create a gnd bounce (where your "ground" is not really at 0V during the transient but at a slightly higher voltage than the actual gnd plane exactly due to the zero ohm resistors which have some small resistance and additional inductance). Also, important thing, I wouldn't use zero ohm resistors in the PFN even if it's just for stitching (which imho is a bad idea to begin with as I said), but I would rather use some specific resistance value like 0.5Ohm or whatever because then you have a controlled value, zero ohms are just some random low value with no effort in controlling the value. In any case, I would suggest at a future iteration to just ditch all of these parallel low side resistors at the very least. Second step would be to try to calculate a target impedance to hit for the trace that delivers the pulse.

[@bussi7859]

Essentially the design of the pulse circuit is to keep the length of the current path as short as possible, I made a pulse laser with bonded chips that gave the same result at 70V as with discrete components and PCB at 350V . I changed from avalanche Transistor to FET. It is still produces today with no improvement.

[@ShopperPlug]

Make a video about it.

[@fzigunov]

I'm glad you got jlc as a sponsor! I'm a long time customer, they always deliver very nice PCBs! Really changes electronics prototyping for me!

[@LesLaboratory]

Thank they are superb. Process tracking, fast delivery, and I always seem to rack up coupons for SMD assembly as well, which is nice for when I need it.

[@andymouse]

Awesome ! this just keeps getting better ! The shot with the pulse train output is mindblowing, cheers for your work !

[@LesLaboratory]

Thanks! Yeah that picture is pretty neat. I built a motorized rig out of old printer parts, just so I could get that shot!

[@andymouse]

@@LesLaboratory :)

[@gsestream]

les is more

[@LesLaboratory]

@@gsestream 😄

[@ShopperPlug]

🤣

[@laserhobbyist9751]

Yes, you can, but keep it cool. Every 10 C above the rated temperature (up to a limit, of course) about half of the life is reduced.

[@LesLaboratory]

Thanks! I was hoping someone who has played with these in CW mode would comment on lifetimes :-)

[@rolmie]

I guess heating is less an issue here, rather bonding wire ripping themselves apart from magnetic forces.

[@LesLaboratory]

@@rolmie I'm sure there are a bunch of other failure modes as well, such as dendrite growth, and photon damage to the facets, but so far so good! I should just let it run at high current for a few days or weeks and see what happens! The results in the literature seem good though in terms of lifetime.

[@rolmie]

@@LesLaboratory @Breaking Taps might have the equipment to answer this :)

[@LesLaboratory]

@@rolmie @BreakingTaps might even have a use for it. With such short duration pulses, thermal effects will be absent, but the number of photons from each pulse, might, possibly, be able to micro machine on the order of atoms or molecules at a time!

[@thorjohnson5237]

I had a thought of a cool technique for lidar, but I couldn't wrap my head around how to do it with a pulse: Use Radar ideas: Analoguely: modulate the beam's intensity with a frequency ramp, say 100-1KHz and back down. Mix the PD return with the outgoing beam (some lasers used to have PDs in them), and get a beat frequency out of it; the frequency of the beat will tell you the range to the object without needing to solve ns timing for TOF sensing. If you want to get even more accurate, you can start figuring out the phase difference (some guys did that with a Red Pitaya). I'm sure you could figure out how do that with say a 100-1KHz pulse interval and figure that out, but the math is making my head hurt... and "phase" is...?

[@moki123g]

Another thing to consider is the threshold current of the diodes. They typically won't lase until they are at a couple of hundred ma of current. You might want to think about being able to apply a dc ofset to get to threshold, then modulate on top of that. Of course now you will have to improve the heat sinking of the diode. I would also be curious what the diode is doing thermally.

[@LesLaboratory]

I have seen biasing like before, and this was even done in earlier efforts, but didn't seem to be required at these extreme currents. It would still be an interesting thing to try out, now that all the other issues are ironed out. Someone suggested there is a paper where they were getting picosecond pulses out of an LD that was biased and fed with RF pulses. There is way more work to be done here!

[@MGoat76]

Would be interesting to try with a 405nm diode too. Awesome work. Love ya man

[@LesLaboratory]

Thanks! Oh totally. 445nm is cheap 405 not so much, but now its been well tested, its time to try I think. There are UV laser diodes now as well, so things are getting real interesting!

[@henrikstenlund5385]

Awesome job, Les. This is likely the best video of yours thus far. I am impressed.

[@LesLaboratory]

Thanks! Hopefully people will be able to make use of it!

[@theserver201]

I second the idea to use a GaN MOSFET take a look at the LMG1020 and his datasheet.

[@LesLaboratory]

Yep! There is some interesting tech out there now for this particular field. I'm also interested in playing with SiC stuff for high voltage work as well.

[@johnwest7993]

As a former PCB layout professional, I can say that your HV traces need much more clearance away from ground. Even a small amount of moisture in the air or using it at a bit higher altitude, (I live at 6,000 feet,) could cause arc-over of the HV. A spacing between the conductors and ground of nearly .15 inch would be the minimum spacing for generic PCB material (without any sort of conformal coating) that I would use under any circumstances with just over 230 V applied, while .2 inch would be much better since your PCB layout clearly has the room for it. With the possibility of an unknown higher voltage being applied for experiments I would design the bd with a .25 inch gap between the HV and Ground wherever I possibly could, (including a wider footprint for the transistor and the LASER connector,) with a painted-on HV dielectric where the traces cannot be given that clearance in order to ensure reliability of operation. Any sort of contamination between the traces, from moisture to dust reduces the dielectric insulation between the traces, increasing to probability of arc-over. Circuits used near the saltiness of the oceans also require extra clearance. Even altitude has a pronounced effect, so with all of those unknowns it's better to just provide as much clearance as you can afford to in the creation of a HV bd design made available to your users.

[@suki4410]

0.2 inches, is 5mm.

[@LutzSchafer]

Don't think this is of concern here with avalanche breakthrough from the transistor of a little more than 100V. Inductance on the other hand plays a major role at these frequencies...

[@LesLaboratory]

For sure, the design is not optimal, nor hardened against the elements, it's just experimental. IPC-2221 suggests 1.25mm minimum clearance up to 300v between conductors on an un-coated board (0-10007ft), but it is generic and probably superseded by more rigorous standards. The pin pitch on the ZTX415 is really quite small, and so creepage could occur on the package itself as well. Far better to use the FMMT415 and ensure sufficient clearance on the rest of the board. For this I just wanted proof of concept. For another project I have been working on I have taken much more care, since I have up to 1kV on the PCB!

[@larslindgren3846]

I think creepage distance is much less of an issue than you imagine. First creepage distance is much less of a risk on the parts of the circuit with nanosecond pulses since there will not be enough time to get a breakdown propagating unless the field strength is very high. On the DC part it can be an issue but not as big as if it was 230 mains voltage. When designing for 230 V mains the nominal peak voltage is 325 V and then you need to be able to handle voltage spikes of a few kilovolts lasting for tens of microseconds from switching transients and distant lightning. In a small DC-supply like this there will be much less transients. More clearance is better but not if it causes more inductance in the pulls path. The loop area needs to be as small as possible. To spread out the legs of e.g. the laser diode will reduce the peak power since the inductance increases. It is better to improve the insulation if needed by coating, poting or oil immersion.

[@Robertwclarke]

Another fantastic video Les. Thanks so much for putting in all that work and sharing it with us all.

[@LesLaboratory]

Thanks! You are welcome!

[@JohnLauerGplus]

This is really spectacular work. Love it.

[@LesLaboratory]

Thanks! :-)

[@TinLethax]

This vid came just in the right time! I've been working on a small project to make dToF LiDAR. So far the digital part (tapped delay line on FPGA) is straight forward, but I'm looking for a fast LD driver that capable of 10ns pulse width.

[@LesLaboratory]

Great! You can extend the pulse width by attaching a length of un-terminated coax in parallel with the capacitor bank (or even in place of it!) to widen the pulse width (see application note 47). There is a nice video on this by Dave Jones @EEVblog here: kzbin.info/www/bejne/q3O8fpiGiqucpLM

[@MachiningandMicrowaves]

I did wonder if some of the microwave PTFE laminates and GaN microwave devices might give faster rise times, but how about a machined coaxial cavity? That might give a really serious and near-constant discharge current when compared with coaxial cables. If the RF impedance is a good match, then it shouldn't have any overshoot or oscillation. You'd still need a hyperfast pulse generator to drive the microwave device of course. Once you get past 30 GHz, you are really into chip-bonding territory, but there you are well into the picosecond domain. Not much point as the laser packages are hugely suboptimal and Stone Age - unless you can hack them up and get within a millimetre or two of the diode chip. Very cool work, fascinating as ever.

[@BreakingTaps]

This is _very_ cool! At that pulse duration and peak power it might be starting into the range of micromachining (when coupled to a microscope objective for a small spot). Especially in something like silicon, the absorption depth will be very small, around 1um iirc? Really love that long-exposure shot too, neat to see the individual pulses!

[@LesLaboratory]

Thanks! Somewhere in that region, it is very shallow on silicon. This should work with 405nm diodes as well. There are even 375nm diodes in production now but they are $$$!

[@bussi7859]

Your wiring gives about 1nH/mm of length, keep the lengths SHORT

[@LesLaboratory]

For sure, it could do with improvement. Lead lengths on the Laser diode are too long as well. For what it is 2nS isn't too bad.

[@GermanMythbuster]

Once again a awesome Video 🤩 Great job! ❤

[@LesLaboratory]

Thanks!

[@FrainFreeze]

I'm considering studying optics & lasers next year (MSEE) and videos like this make me very very excited. Amazing content as always Les! I was wondering if you could cover pico and femto as well in the future? Best, TT

[@LesLaboratory]

Thanks! I would love to get down to pico and pemto. It has already been remarked that the Raman Laser build probably resulted in fs pulses, but at the moment I have not way to detect them...yet. As this channel grows, I'm sure I will find a way to do it inexpensively :-)

[@jobidi99]

Oh man do I have to comment on this. You mentioned pumping dye lasers with diodes, but in my opinion there would be an even more prominent example that might be of interest, Ti:Sapphire. With the power of blue/green LDs rising and getting ever closer to the absorption peak at 488 I think that could make for a wicked laser, especially which the prospect of modelocking in mind. Another way of generating short pulses from a diode that came to mind was having them DC biased and then modulated with RF. I would have to look that paper up again to a| how short those pulses got. Great video as always!

[@LesLaboratory]

@@jobidi99 oh for sure, Ti:Sapphire is the answer. I'm hoping some company in China starts producing the optics at a low enough price for everyone to have fun! Interesting, if you find the link please share it. One notable observation though, we might be at the limit for pulse width out of these things, certainly at this power level. The input pulse is only 2 nanoseconds, but the output is closer to 7 nanoseconds. I'm not entirely sure why. Perhaps enough energy is dumped in the die that it just continues to glow and Lase, or perhaps the capacitance of the die is storing energy.

[@jobidi99]

@@LesLaboratory Sharing links on yt is always a bit difficult, but the paper i was thinking of is "Nonresonant self-injection seeding of a gain-switched diode laser" and available on reserchgate. This apparently manages to reach the picosend regime. Another paper I can't find anymore this technique was used to seed a more powerful solid state laser

[@LesLaboratory]

@@jobidi99 got it thanks! I will have a read and see if it is something that can be applied! Cheers!

[@codacoder]

Very cool!

[@LesLaboratory]

Thanks!

[@kevinmartin7760]

I don't quite understand the "long exposure" photo at 12:55. What is the beam reflecting off in mid-air? The earlier shot with the flapping paper is essentially using this laser as a glorified strobe lamp. The size and spacing of the spots would be the paper's speed times the pulse width and pulse repetition period. The pulses themselves would be spatially a couple of feet long (using the rough 1ns/foot speed of light). You could observe this using smoke and a picosecond-ish camera shutter.

[@gorak9000]

I was also wondering how a long exposure shot resulted in discrete laser dots like that - I don't understand... I guess there has to be a "moving piece of paper" or something in that photo too, but you just can't see it in the exposure, and you only see the dots

[@ElsataVidz]

This is probably explained aliasing of the camera internal sampling rate vs the function generator frequency used to trigger the laser driver. This could explain the spacing between the spots and the length of those spots. Normally, those spots should be 4 or 5 feet long because the optical power metered was about 6ns.

[@LesLaboratory]

Ah! I thought about videoing how this shot was done, but didn't think anyone would find it very interesting! Maybe I should have! I tried doing a long exposure, whilst quickly wafting a piece of paper along the beam length, and it works, as on camera, but not particularly well. Right behind the Laser you can see a pair of rails. This was a Linear motorised rail from a printer. I mounted an arm to it with a white target on the end, and that sits in the path of the Laser beam. The camera shutter is opened and the target moved from one end to the other, quite quickly. This was driven using an Arduino.

[@Les__Mack]

Great video. Thanks!

[@seanmcelwee5034]

When you took the average power measurement, is the power meter you're using a photodiode or a thermal sensor? If these are high peak power pulses, the photodiode will saturate and result in a false average power reading.... something to consider. Or consider using the pyroelectric sensor you made in a previous video since it more equipped for peak power

[@LesLaboratory]

The power meter is a silicon sensor, but, the integration time is about 2 seconds, so the pulses are ignored and we get a fairly accurate average power. Unfortunately because the output is in the nano joule range, my Pyroelectric sensors wont even detect it, which is a shame. Like you I would rather see a direct measurement than a derived one.

[@lukebowers536]

wow thats an insane price for such a small circuit, how do they justify that ? Great experiment, over 60 watts is really quite something.

[@LesLaboratory]

$2 bucks for 5 boards is great. I think they panelize at the factory to reduces costs. I hand populated these though because of the experimental nature of it.

[@lukebowers536]

@@LesLaboratory those boards you made where very nice, ive started using jl for my little laser pointer boards. have you seen the nichia diode arrays, ive got one here rated at 128 watts, its scary, ive not experimented with it yet due to having damaged laser eyewear, ime not risking it untill my new set arrive from thorlabs

[@pyromen321]

@@LesLaboratoryI think he was talking about the £340 boards.

[@laserdan]

Have you looked into using GaN FETs? They are capable of extremely short pulses, and the ones I've looked at from EPC have packages that are designed for absolute minimum inductance.

[@LesLaboratory]

Hmm, I will look into that. I was thinking for the next board using an FMMT415, I only used through hold because it is easier to re-work the prototype. Not thought about GaN FET's so thanks or the tip, I will go look those up!

[@freelancer917]

Thank you for the video! I assume you made sure the oscilloscope actually has 50 ohms input impedance for your measurements? As you may be aware, most of them have a high input impedance by default. Some can be switched into 50 ohms input mode.

[@LesLaboratory]

Thanks! Yes, its a TDS784 and has a switchable impedance of 50ohms. For fast measurements like this, it's the only way. On my little 100MHz scope I use a 50 Ohm terminator right before the input.

[@gorak9000]

Did you notice any appreciable differences between the ZTX415 and the 2N5192G? You made drivers with both, but left us hanging on what, if any, differences there are, and if one is better than the other in any way!

[@LesLaboratory]

Yes, I probably should have mentioned it. The 2N5192 results in a higher threshold and is obsolete, though still available. The ZTX415 has a lower threshold and is currently available, but expensive at 10 bucks each. Both work just fine, and I am sure others will too.

[@alexwang007]

Maybe try a GaN FET? The EPC boards you showed has full design files (I've made some using JLC, which was the EPC9126, and others), and they are very serious about minimizing inductance, you could probably get nicer edges and more peak power!

[@LesLaboratory]

Yeah a couple of people have mentioned GaN FET's its definitely worth looking into.

[@zebo-the-fat]

Very nice!

[@LesLaboratory]

Thanks!

[@hirboodakhavan7793]

Hi! Very interesting video and I learned a lot. I might have seen every single one of your uploads by now. I'm working on a project to generate two picosecond pulse-width beams from diodes whose peaks are apart on the order of picoseconds. Any suggestion on how to go about this would be extremely appreciated!!!

[@LesLaboratory]

Honestly i'm not sure at this point. ~7 nanoseconds is where I am at just now. I might be possible to get into the picosecond range by re-spinning the board with lower inductance and capacitance. The ZTX415 is capable of picosecond rise times, but I am sure there are better alternatives. What is your application?

[@saadtiwana]

Very interesting video, thanks for sharing. I have two questions: 1. What was the energy per pulse that you got? The paper showed pulse energies in the mJ range...did you get anywhere near to that? 2. Do you think the pulsed laser diodes (905nm) can be overdriven in a similar fashion to get higher pulse energies? The datasheets all say up to 100W peak with 0.1% duty cycle and 100ns pulse widths, but i haven't seen anything about overdriving them. Pls share if you know about this.

[@LesLaboratory]

Thanks! Pulse energy is about 468nJ (calculated) so almost half a mJ, not too bad. The IR diodes, (I assume) are already at their max output in pulsed mode. I suspect with cooling, you might get a couple of watts CW. It might be interesting to try though with very short pulses!

[@Robertwclarke]

So Les, I was just thinking how similar the circuit is that you are using is to the famous spark gap capacitor discharge of the DIY Nitrogen laser. And I wondered could you put a laser diode across the plates of a nitrogen laser? Does this make sense?

[@LesLaboratory]

It's very similar. I think a diode placed across the rails of a Nitrogen Laser would be instantly destroyed though. There is a huge difference between ~200v and 20kV, before the diode even emitted light, I suspect several kV woudl appear across it. With all that said, I have been toying with the idea of building a Nitrogen Laser (for the most part) on a PCB. It would be so cool if they could be manufactured really small and inexpensively.

[@Robertwclarke]

@@LesLaboratory what about depositing silver chemically on two sides of a piece of mica? That would be very tidy!

[@Robertwclarke]

@@LesLaboratory could one close the spark gap so it triggered at 200v instead?

[@colinbarnes705]

Could this be used to make a supercontinuum laser, replacing the complicated nitrogen+dye pump? If I remember correctly, your dye lased around 426nm in the supercontinuum video. Sharp makes a 425nm diode that'll do 2W continuous.

[@LesLaboratory]

It might, and that is one of the motivations of this project. For SC generation (like with N2 and Dye Lasers), you need a fairly wide bandwidth of Laser light to begin with, and the bandwidth from diodes is probably too narrow. The power levels are very low as well, about two orders of magnitude lower than the nitrogen Laser pumped dye laser. With all that said, it might, just might, be possible to use very narrow core fiber, and multiple pump diodes to get something to happen. So far I have not observed any broadening in fiber, but I have only tried a couple of Laser diodes.

[@wolpumba4099]

*Nanosecond Pulsed Visible Laser Diode Driver: Pushing the Limits* * *0:24** Powerful Visible Laser Diodes:* The video focuses on the NUBM44 and NUBM47 blue laser diodes, the most powerful visible single emitter diodes available, capable of 6 watts (and potentially up to 7-8 watts with reduced lifespan) of optical output power. * *0:54** Pulsed vs. Continuous Wave:* While high power infrared pulsed laser diodes are common in LiDAR applications, visible laser diodes are traditionally operated in continuous wave mode with current limiting to prevent damage. * *1:40** Scientific Literature:* Research indicates that pulsed operation of high power visible laser diodes can achieve peak powers of several watts, with pulse durations under 10 ns and currents of 50-60 amps. [From bussi7859's comment] Optimal performance requires minimizing the length of the current path. * *4:33** Achieving High Peak Power:* The video highlights experiments demonstrating peak output powers approaching 30 watts from commercially available visible laser diodes using a simple avalanche pulsed driver circuit. The 445nm laser diodes performed exceptionally well, reaching over 200 nanojoules and 25 watts peak power. * *6:12** Avalanche Driver Circuit:* The video explores using a Jim Williams avalanche driver, known for its nanosecond rise times, as a simpler and potentially more cost-effective alternative to commercial MOSFET-based pulsed laser drivers. [From laserdan's comment] GaN FETs might be an interesting alternative due to their short pulse capabilities and low inductance packaging. * *6:50**-**7:00** Driver Design and PCB Layout:* The video showcases a custom-designed PCB for the avalanche driver, emphasizing a large ground plane and thick traces to minimize inductance, drawing inspiration from commercial designs. * *11:28** High Voltage Power Supply:* The driver requires a high voltage power supply (around 188 volts in the demonstrated setup). * *12:35** Nanosecond Pulses:* The driver successfully generates nanosecond pulses, visible as individual flashes when a piece of paper is moved rapidly through the beam path. * *13:13** Power Measurement:* Measurements reveal a pulse width of 6.97 ns at a repetition rate of 5 kHz, with an average output power of 2.34 mW. * *14:47** Peak Power Calculation:* Based on the measurements, the calculated peak power is an impressive 67.1 watts at a drive current exceeding 80 amps. * *15:18** Laser Rangefinder Application:* The pulsed laser is used to demonstrate a simple rangefinder using a beam splitter, a corner cube retroreflector, and a fast photodiode. The time delay between the transmitted and received pulses accurately measures the distance to a target. [From bussi7859's comment] Rangefinders operating at 10kHz have demonstrated ranges up to 6km. * *17:00** Fluorescent Dyes and Future Applications:* The pulsed laser's potential for fluorescence analysis and use in confocal microscopy setups are discussed. Future work includes experimenting with different avalanche transistors, laser diodes, and pulse forming network parameters to further optimize performance. [From MathewMoss-fp9ju's comment] There's interest in exploring quantum entanglement experiments with the pulsed laser and crystals like GAGG. [From arktik75's comment] There's also interest in exploring the possibility of pumping dye lasers with this pulsed laser. I used gemini-1.5-pro-exp-0801 on rocketrecap dot com to summarize the transcript. Cost (if I didn't use the free tier): $0.08 Input tokens: 21048 Output tokens: 756

[@LesLaboratory]

Cool! Never though of using tools like this.

[@omsingharjit]

Is it possible to make Diy Powerful fiber laser using some Diode lasers and fiber?

[@LesLaboratory]

Such Lasers already exist, however I have not attempted it from a home-brew standpoint.

[@omsingharjit]

@@LesLaboratory will you try?

[@arktik75]

Hi Les. What is the use of R1 to R6 resistor if they are 0 ohm? Why not connect the LD directly to the capacitors bank? Thanks.

[@LesLaboratory]

I wanted to mess around with the values of those to see what effect it had on pulse width. Larger values, a few Ohms in total, lengthens the pulse, however the waveform looked particularly ugly, so I reverted back to 0 Ohm.

[@arktik75]

Many thanks Les!Then I can simplify the board by eliminating the resistors and also the resistors for oscilloscope since I don't have one anymore😊.

[@arktik75]

Beautiffull, Les....can a dye laser be pumped with this laser? Thanks.

[@LesLaboratory]

According to academic papers, yes, but it seems to require a rather precise setup. Pumping a Dye laser with one of these is one of the motivations for this project.

[@arktik75]

I thought your aiming for that. I'l try to buid the same setup. I have the diode already. The PCB is two layers or more? How much will cost to order?

[@codacoder]

Can the function generator generate arbitrary predefined nanosecond-length signals?

[@LesLaboratory]

@@codacoder no it's just an inexpensive one. It would be nice to have variable pulse width for this.

[@codacoder]

@@LesLaboratory Would also be cool to have it blink 1 billion digits of Pi within a second (using its binary expansion, or variable length pulses for each digit) :)

[@graealex]

What's wrong with comically-sized beam splitters?

[@LesLaboratory]

@@graealex for demos like this, nothing at all, but compared to the tiny laser diode, it's kinda fun 😀

[@graealex]

@@LesLaboratory Love the videos and love the list of supporters grow!

[@LesLaboratory]

@@graealex Thanks! Yes, it's really great, and I have the encouragement from supporters like you to thank for it!

[@Ma_X64]

What is a daod?

[@LesLaboratory]

I'm guessing this is the auto closed caption attempt at diode!

[@savagesarethebest7251]

999th like and this is the 111th comment too 😅👌

[@LesLaboratory]

Sweet!