Economical Fiber Coupling Methods?

[r34p3rex]

For my senior project, I'm looking to couple several lasers into a fiber. Basically, 6 different lasers (405, 445, 532, 635, 650, 808nm) need to be injected into a single fiber (200 or 400 micron). The lasers will be turned on and off sequentially one after another (only one on at any given time). I came up with the following ideas.

A) Using several dichro mirrors, combine the 6 lasers into one beam, then collimate that beam onto a single 400 micron fiber. The dichro's I found are relatively cheap because they are manufacturer rejects (such as this Optical Filter Dichroic 480DRLP 22X1mm Beamsplitter@45 | eBay). The only problem is, the device I am designing is intended for global health applications (keep the cost low!). As such, if this device is to be manufactured in the future, buying full price dichro's would increase the device cost significantly.

B) Inject each laser into a 100 micron fiber (terminated on a SMA connector) and then couple the 6 100 micron fibers onto a single 400 micron fiber. The problem with this design is that it is very hard to inject a good amount of light into a 100 micron fiber (need at least 2 mW to make it through). It's doable with the expensive Thorlabs equipment we have here, but it may be hard to do it with cheap parts.

Does anyone have any other ideas?


tl;dr: Need a way to inject 6 different wavelength lasers into a single fiber. HELP!

 

[Cyparagon]

There's no way you found the five dichros you need. You can combine the blue/violet with the rest of the four with the dichro you found, but you'll never find the other four with the transmission spectrum you need for anything less than... 4, maybe 5 figures is my guess. Use a prism instead.

 

[Bluefan]

Edge-pass filters are quite common, so if you look around you'll find the right optics. They will however be expensive, they're quite normal from a professional point of view but they're not the low cost mass produced RGB dichro's, so expect prices like the Thorlabs prices.

Coupling different fibers is a challenge, but if you use a standard fiber combiner and just make up for the loss with lots of power it's doable, but each laser would have to be fiber coupled individually.

A prism doesn't have much dispersion. Try combining the wavelengths with a diffraction grating and then use a achromatic lens or microscope objective to focus them into a fiber. A multimode fiber of 50 of 62.5 um is already quite easy to align for a single laser, 200 or 400um is just BIG.

Aligning multiple lasers through a grating into a fiber is slightly more difficult. I'd recommend to first combine them into a parallel beam and then align the fiber coupling. Should work fine and 2mW is very easy to get into a fiber if you start with a few tens of milliwats.