Fiber coupled laser diode teardown - Page 1
Forum section: electronics / general

author: blueskull
author_rank: Unknown
timestamp: September 20, 2016, 07:32:16 am
content: I tore down and reverse engineered a FocusLight 8W IR laser diode. This diode is a 915nm, 8W laser diode coupled into a 105um/125um/250um 0.15NA multimode fiber.https://youtu.be/eD2KMd2FxOoStill being processed by YT, FHD version should be available in a couple of hours.

author: lukier
author_rank: Unknown
timestamp: September 20, 2016, 12:37:58 pm
content: Very nice video!I have a question on the constant current driver. What do you use at these current levels? Do you have something off the shelf or maybe some DIY (schematic?).I'm asking because I would like to get back to my laser experiments, but this time with IR more powerful laser. I've tried 'etching' black paint painted PCB with 1W 445nm laser mounted on my CNC machine, but it wasn't very good (see here:https://www.eevblog.com/forum/beginners/practical-proscon-of-laser-vs-milling-of-pcb's/msg766269/#msg766269).Maybe 915 nm 8-25W fiber coupled would be better. I could place the laser elsewhere (with TEC and heatsink) and just ran the fiber to the CNC machine head (I need to think how to couple a focusable lens to the fiber). I might even build a lighter belt driven machine (like cheap 3D printers) to speed things up (CNC with screws is quite heavy and slow).I have some low power diode drivers fromhttp://odicforce.com/,up to 2A and I also recently aquired ILX Lightwave LDC-3722, very cool device, but only goes to 500mA. I also have a Coherent 100W laser power sensor head, so I could check and adjust the optical power. So if I get a 8-25W laser diode the only thing to solve is a 14A constant current driver with voltage compliance. Maybe I could design something and use a bunch of power rectifier diodes as a "simulated" load of the laser (I always worry I'll cook the laser diode and waste a lot of money, these things are so delicate).

author: lukier
author_rank: Unknown
timestamp: September 20, 2016, 10:47:43 pm
content: I don't want to ablate copper. LPKF makes such cool machines and you are right, they use pulsed lasers. I want to just burn the black paint that I covered the PCB with, as shown in the link to my old post. Normal chemical etching then.

author: lukier
author_rank: Unknown
timestamp: September 20, 2016, 11:27:11 pm
content: Quote from: blueskull on September 20, 2016, 11:05:21 pmI've tried the photosensitive method many years ago and was disappointed how fragile the process is. From uniformly coating the PCB, to the quality of the mask (well not the case for laser) printout, exposure times, developing solution strength etc. It can produce awesome results, sure (I once even got a speck of dust imprinted in the copper), but requires extreme care and patience and still leads to frustration. That's why I've been doing toner transfer for years. Not as high quality but quite reliable, fast and easy. Also, I would like to minimize the wet chemical processes and mess in general (that's also why I don't like PCB milling).Quote from: blueskull on September 20, 2016, 11:05:21 pmWell you might be right, the diode itself is expensive and I would have to spend much more on the splicer and other tools (I don't have any, never did anything with fibers, well maybe except tearing down broken Tektronix OTDR for parts). I was surprised when I was browsing these diodes on ebay that it's just a fiber, no coatings or plastic jacket for some protection/strength.Therefore it might be more sensible to get a low cost 40W CO2 laser cutter. I think some people managed to burn the paint off PCB with these and I could use it for other stuff as well (acrylic, plywood etc). The problem here is just the size of these machines due to the laser tube length :/ (and ventilation).