IPG YLP 0.5mJ 10 watt fiber laser test results

[Skyko]

I am going to collect my thoughts in this thread about my new to me IPG YLP fiber laser model YLP-0.5-100-20-10 manufactured 05/2009.

The laser has 5 meters of fiber between the base unit and the head, and the head has a Faraday optical isolator attached to it (I think).

I built a simple circuit to power up the laser to full nominal power and turn it on for a variable amount of time. My first tests did not apply any signal to pin 22, which is the pulse repetition rate pin. I figured the unit would provide a default PRR and it does seem to do this (around 19.9khz measured on my setup). Later I hooked up the function generator output from my Agilent MSOX3024A oscilloscope and provided 40khz and 100khz pulse rep rates for testing. It is interesting in the following snapshots that the signal from the photodiode I am using to measure pulse length and frequency went way way up when I provided a 40khz rep rate. I was on the 5mV scale when measuring with the built in 19.9khz rep rate and had to move to the 50mV scale and move the sensor back several inches (it is just pointed at a black anodized aluminum plate that is terminating the beam). This makes me suspect the scope traces I took at 19.9khz because the average power I have measured using a Synrad 250 watt powerwizard meter have been about the same at 20khz, 40khz and 100khz (around 9 to 10 watts). I can't see a reason that the photodiode would respond with 10x the signal when going from 20khz rep rate to 40khz.

The pulse length seems to be less than 200ns at 20khz and at 40khz but it is really hard to tell because I do not know the rise/fall times of my reverse biased (10V) photodiode (guestimate 10ns or so). The spec at 20khz should be 100ns and 10 watts average power.

I have included screenshots of the scope signals at the internal 19.9khz rep rate and a 40khz rep rate applied to pin 22. I have also included a burn test on some laser paper. This test was done at 20khz, 40khz and 100khz at 10 inches from the end of the delivery head with a total laser on time of 100ms. I have included a ruler for scale, but the spots look ok to my untrained eye?

[Skyko]

I scrounged an odd plano-convex lens...not even sure if it is AR coated...then lathed a quick mount to align it with the optical isolator of the IPG fiber laser.

Putting on the OD10 goggles and even then just watched the webcam view of the laser, I fired a 2 second burst at 20khz.

My first test subject was aluminum foil. I immediately punched a hole through it even though the focus was not tight. One Reynold, check!

I then went for broke and grabbed a razor blade. It took a few trys to get the focus correct, but the last two shots blasted all the way through. One Gillette, check!

I am amazed how tiny the spot is. I wasn't even making an effort to get a good focus and this is a very short FL lens (about 20mm) so the depth of field is not big.

My experience has been with CO2 lasers and quite a larger focal point. I don't even have anything readily available to even measure how small the hole is!

Be safe!

[Skyko]

I tried to take a picture of the razor blade using my non-SLR digital camera and my binocular microscope (just focusing through the eyepiece at 30x).

Poor quality, but you can see the holes as I illuminated the razor from the front and the back. The black line is a human hair...about 20um in diameter.

The holes look to be about half the diameter of the hair...a little blurred in the photo where they look almost the same diameter.

Makes you wonder what you could do with the correct lens and real ability to focus. Luckily I am much better with cnc than microscope photo taking.

[krazer]

Nice looking laser, with a good quality 2cm lens and a 4mm input beam you should theoretically be able to get to a 6um spot size. It really is amazing how much better the beam quality from a fiber laser is compared to a multimode diode laser, or even a good quality CO2 laser (the wavelength of a CO2 laser is 10x as long, so the spot size is 10x as large for a given focusing arrangement).

With the elusive f/1 lens it would be possible to focus down to roughly 1 wavelength (radius), but with a more reasonable f/0.5 (something like a 40x microscope objective) you should be able to get to about 3um, just watch out you are starting to approach the levels at which you can ionize air (roughly 500GW/cm^2)

[VDX]

... yes, the fiber-lasers are really 'fine' beasts -- i have one with 50Watts CW, that looks nearly identical - and an 40MHz AOM for modulating them, that will remove roughly 15 percents of the energy.

With a single standard glass lens with f=35mm I'll get around 20 microns spot-diameter, with a 1:8 beam-expander this goes down to nearly 5-7 microns ... but didn't measure the punching diamters yet.

Without an optical isolator I have to avoid back reflection, but cutting 0.5mm thick hardened steel was no problem ;-)

Viktor

[Skyko]

What model is yours Viktor? You are able to cut 0.5mm steel with 50 watts CW and no high peak power pulses? If so, I guess that is an indicator of how high a quality the beam is from these things.

I think mine has an optical isolator...the long thing attached to the head at the end of the fiber. I am not sure how much energy is lost in that part though.

[Skyko]

Nice looking laser, with a good quality 2cm lens and a 4mm input beam you should theoretically be able to get to a 6um spot size. It really is amazing how much better the beam quality from a fiber laser is compared to a multimode diode laser, or even a good quality CO2 laser (the wavelength of a CO2 laser is 10x as long, so the spot size is 10x as large for a given focusing arrangement).

With the elusive f/1 lens it would be possible to focus down to roughly 1 wavelength (radius), but with a more reasonable f/0.5 (something like a 40x microscope objective) you should be able to get to about 3um, just watch out you are starting to approach the levels at which you can ionize air (roughly 500GW/cm^2)

I did manage to spark air with a SSY1 head a few years back using a microscope objective. I was never able to completely punch through a razor with it curiously enough. It may be that I just never got the focus in the right spot on the blade because the peak power was certainly high enough.

[VDX]

What model is yours Viktor?

... it's a PYL 50 M - nearly same design as yours, but the 5m long fiber is not detachable and the end is a collimator, outputting a 5mm wide beam.

The PS is a separate unit with display for Watts or Amperes (switchable).

Viktor

[krazer]

Getting a SSY-1 to punch through a razor blade would take some significant over driving, the only reason that this laser is capable of it is that you fired 40,000 shots during that 2 second burst, a total energy of 2J, just about right for vaporizing a hole in a razor blade.

[Skyko]

Getting a SSY-1 to punch through a razor blade would take some significant over driving, the only reason that this laser is capable of it is that you fired 40,000 shots during that 2 second burst, a total energy of 2J, just about right for vaporizing a hole in a razor blade.

More like 20J (10 watt-seconds for 2 seconds), although I don't know exactly when the hole was formed...might have been after only 1 second or shorter.