ps-ns pulsed laser solution for spectroscopic applications

[malachai0852]

Photonlexicon,

I am attempting to build a time-resolved setup for either fluorescence or electronically delayed transient absorption. For this I am hoping to find a nano/picosecond emission source. I've been using lasers for spectroscopy applications for a few years, but I'm relatively inexperienced in building them from scratch. And for this application we would like to keep cost down so no >$20k prebuilt systems.

Specs I believe I would need are: (sync-in & out triggers if I go the transient absorption route), 1Hz-100kHz rep rates, 1uJ-100mJ pulse energies, <100 ns pulse duration, 200-532 nm wavelength (single mode or broadband, doesn't matter and could be selected with filters or gratings).

I've found a number of products that may work, with the cheapest being $12k. This is still within budget for the source but I'm wondering if there are cheaper solutions? With enough time I'm sure I could piece together a fast diode with a custom driver, but I was hoping to get some experienced advice before going down the rabbit-hole.

I like this forum already and hope to contribute in time.

[VDX]

... I have an old comercial N2 TAE-laser, which is specced with 200ps pulse time and 30 Hz repetition rate at 337nm wavelength - this could be an interesting route, as N2 TAE lasers are pretty easy to DIY ...

Viktor

[mixedgas]

Um, Your asking for specs that come from 15,000$ to 40,000$ lasers. In some cases 250,000$ lasers.
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A microchip based YAG or q-switched fiber laser on the low end, a used Ekspla OPO on the high end.
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While you can pulse a diode, your looking for short pulse peak power, and that comes from a lasing material with long upper state lifetime, such as Nd:YAG, ND:YLF or ER:fiber.
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Diodes have almost no energy storage in their upper state lifetime. Making it hard to squeeze out useful energy in picoseconds.
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Maybe nitrogen in some cases at the low rep rate end.
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With that budget, do you want to be a researcher, used laser repair guy, or YAG laser developer? Narrow down your wavelength specs. Buy a bigger laser then you need and attenuate it.
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Your rep rate range stretches from DC to Daylight, same for your energy specs. Kind of unrealistic to expect such wide ranges.
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Call Lucian Hand at Altos Photonics* and see if any of his customers are upgrading, he might have something on trade in. Before you call Lucian, get your prof to narrow down the specs.
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Do you have a budget for the digitizer, spectrometer, phast photodetector, and optics mounts yet?, Read up on Laser Safety and have a budget for enough eye protection? Got Joulemeter? Have a proper two or four channel
delay generator ? Generally there are other techniques for this, had a good look at Review of Scientific Instruments lately? They have a wonderful search engine after you spend an hour reading a few basic papers and coming up with a list of keywords to run through one or two at a time. Ever heard of Phase Flourometry?
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Steve

(*Disclaimer, I'm a former employee, but they do make a good, workhorse, product if you learn how to maintain/adjust the system during install)

[malachai0852]

My apologies, the OP was a bit unclear. I am currently a researcher, and looking to build a setup for time-resolved fluorescence or nanosecond transient absorption (detection is very cheap in the ns regime). I've already been using femtosecond systems for a number of years so we have tables, optics and other gear. I don't need all of those specs in a single unit, rather, anything within those specified ranges will do. The cheapest I've found is a doubled 1064 DPSS (532 output) for $12k, 8 ns, 1-10Hz, 1.6mJ pulses; and that includes PSU and controller! That's pretty good compared to the other 20-40k+ quotes I've gotten. I was mostly curious if anyone here has any knowledge of cheaper options---and I wouldn't mind a discussion on custom waveform generators powering LED or other simple DIY options. Ultimately my source doesn't even need to be coherent, collimating with a single lens would be sufficient for my application.

[mixedgas]

Ah, Now I can contribute as I have a target. Sorry for the attitude, but we get some grad students with some wild expectations here. Let me do a little looking around.
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25 years laser experience, 9 years as University Research Assistant, 3 Years as a University Senior Instrument Technician, and a few years doing this and that with lab lasers. One year as a pico and nanosecond FSE including OPO/OPA before returning to university to finish retirement requirements. In my case, everything from CW gas lasers to repairing power supplies and training users for a Pentawatt system, with some spectroscopy in there. Over twenty years of laser show involvement.
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Would you prefer high rep rate, or high energy?
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Calling Lucian is worth a try. Ekspla systems are like the original Volkswagens, they can be rebuilt again and again.
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Led in the 500 pS to 10s of nanoseconds is doable. We have systems on campus that run LED for PIV and Stroboscopic uses, I can meander over to the other building and see what he uses for the fast green LED. The main company in the US that made decent OEM led and diode laser pulsers just got adsorbed by Tektronix, with a serious degradation in the sales web site and product range.
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Steve

[mixedgas]

Fast OEM Diode drivers come from IXYS Colorado, Highland Technology, and Avtech Electrosystems. There are a few others.

I'll see what I can find in the laser arena. We have a used laser dealer near here (Ohio) that is worth looking at.

Steve

[malachai0852]

Thanks, I'll definitely look into your recommendations and contacts. We have a slight preference for lower rep-rates 1-1000Hz (simpler if we ever need mechanical chopping), but anything up to 100KHz would work for now. If we go the TA route, we would need two lasers in master/slave configuration with the electronically delayed probe laser accepting external sync (but I'm mostly sticking with time-resolved fluorescence unless I find two pump lasers for less than $13k total).

With higher rep rates we can go to lower powers and still maintain signal/noise, at low rep rates we would need slightly higher pulse powers (>0.1 mJ).

I would be very interested in the basic design of the LED setups you know of. If it's "simple"* and relatively inexpensive we may go that route, but I'm less experienced with LED/driver options, and would need to be pointed in the right direction or replicate another design.

*nothing is ever simple

[malachai0852]

So with all of 4 hours of hunting around, is it really as simple as hooking up a higher powered LED (Cree XLAMP or other? which has <10ns turn-on response) to a compatible waveform generator (Keithley 2000 series)?