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  1. J

    Need a NUBM31T PWM driver -- Killing chinese ones.

    That's an incredibly expensive little PSU likevvii. Hope you're making the most of it. These diodes are surprisingly robust. 85mA reverse current and a temperature limit of 70C. I have a couple of fiber coupled diode lasers and they aren't anywhere near as tolerant, although they do have a much...
  2. J

    Need a NUBM31T PWM driver -- Killing chinese ones.

    The hardware expects a current sourcing TTL signal. The signal on the PWM pins has to be pulled low by a transistor, bridging the two pins, to effectively switch the unit off (as its default is on). I'm guessing you're driving the PWM input with something CMOS based which won't be able to handle...
  3. J

    Need a NUBM31T PWM driver -- Killing chinese ones.

    Yes, I've been down this road with that driver. I had to 3D print a fan mount for the PSU because of overheating issues. I made a short write up as to how you can implement your own PWM interface: https://metalmatters.co/showthread.php?tid=7 With all that said you probably are better off just...
  4. J

    Building a fiber laser

    Prewritten no doubt. The equipment used to manufacture them is quite expensive. The FBGs serve as reflectors/bandpass filters in this context. It definitely makes more sense to just buy an engraving unit if you want sub 50W. A splicer alone is around 1k USD. I need CW as I'm working with metal...
  5. J

    The spam

    Received one earlier and reported. I know that links can no longer be posted by users with less than 20 posts. Could that apply to PMs also?
  6. J

    Building a fiber laser

    Has anyone here constructed their own fiber laser? I'm posting here as the NIR band doesn't fit into the colour based categories well. I'm looking to build my own, in the region of 100W CW. I want to know if there are any special considerations that need to be made in regard to bragg gratings...
  7. J

    Laser safety and goggles

    Are they the same colour as these? https://www.laserlands.net/protection/16011009.html I think laserlands/eagle pair share a lot of the same stock. I purchased a set of the goggles in the link above after having a good experience with their dedicated 190-540nm goggles. Unfortunately they are...
  8. J

    Looking for a fiber combiner for FAP800

    https://www.alibaba.com/product-detail/Y-type-1-3-fiber-optic_62330278116.html?spm=a2700.details.0.0.3bbc3c6d1tRouj
  9. J

    Maximize Nubm44 or any diode beam concentration

    I don't own a G2 lens but from what I gather the G8 is the preferred lens. Perhaps one of those might improve things.
  10. J

    NUBM31T 95W 455nm

    I think the general rule of thumb is that 2/3rds of a PCX lens is useable - look into spherical aberration. I've found that a 63mm biconvex lens is the minimum. You might be able to go smaller with an aspheric lens. EDIT: This is what will happen if your lens is too small. The corners of the...
  11. J

    PBS beam combining two NUBM38s

    Well time to finally add some closure to this thread. I've opted to combine the 2 NUBM38s using a prism. I know this is a potentially lossy method but I've ordered an AR coated prism and am willing to tolerate some losses for the sake of keeping the form factor small. The manufacturer states...
  12. J

    Combining two NUBM36 with a PBS cube or by knife-edging prism method

    I think Thorlabs will cater to requests but their prices are already high enough..
  13. J

    Combining two NUBM36 with a PBS cube or by knife-edging prism method

    Ah, vaguely recalled you couldn't run it at full power - assumed it was a fixed limitation. I was curious to know if you had pushed your experiment any further. Yeah, I try to avoid Ali for that reason. Even prior to covid, I noticed a lot of companies on there weren't fulfilling the shipping...
  14. J

    Combining two NUBM36 with a PBS cube or by knife-edging prism method

    Thanks for the info. At the moment I'm thinking of using a concave mirror to combine multiple NUBM38s, setup as a beam expander. I've ordered the mirror and a concave lens. Hopefully the divergence won't be too bad. Have you upgraded your heatsink for further testing?
  15. J

    PBS beam combining two NUBM38s

    Yes, a single lens can focus them down to a spot. I've managed to sinter SS316L down to a track width of 0.2mm which is beyond what I expected. Why do you suggest knife edging and a WP? The beam is already combined and given I'm trying to melt metal, I've read circular polarization is optimal...
  16. J

    PBS beam combining two NUBM38s

    At the moment I'm in two minds. I've ordered some cylindrical concave/convex lenses to reshape the NUBM38 output and increase its power density. I'm not sure how detrimental they'll be in terms of divergence but we shall soon see. If you succeed with your efforts Light superglue then I'll...
  17. J

    Combining two NUBM36 with a PBS cube or by knife-edging prism method

    Well.. this is a timely post Did the seller state the joule rating? I'm not sure how relevant that figure is as it appears to relate to pulsed systems but there never seems to be any information regarding CW limits. Are you willing to share the supplier of that PBS cube?
  18. J

    PBS beam combining two NUBM38s

    I was thinking of using a single PBS cube as each string of 7 diodes is 2mm apart. I would need a 20mm+ cube though, AR coated and designated as high power, those don't come cheap. e.g. https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=6055 I've found some cheaper ones in China but...
  19. J

    PBS beam combining two NUBM38s

    I'm assuming each input would need to pass through a focal lens before entering an expander. That seems like quite an elaborate setup for an XY gantry. I'd really like to stick with a PBS cube if it is possible.
  20. J

    PBS beam combining two NUBM38s

    What are the typical power limitations when it comes to combining beams using PBS cubes? I see them advertised commonly with power ratings of 5W or 8W but am not sure if that is per incident beam or overall. I suspect that if multiple beams were incident upon a cube (as we commonly see with...




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