I have a free-space laser coupler (Omicron Laserhub) that I purchased for the ability to switch out failed laser diodes when necessary. Touch wood, this isn’t necessary yet, but what’s the drawbacks to buying something like this (below) as a replacement? It’s not something I’m considering; I would definitely just go ahead an spend the money on a known brand, but I’m curious how there can be such a discrepancy between the two products. Obviously, the price is ~100 US, instead of several thousand , so there must be something that’s very different between this and, for example, an Omicron Luxx laser. Clearly I’m not a laser physicist or I would already know this, but what’s the difference between these cheap modules and more expensive ones? Reliability? Collimation/fibre coupling? Stability?
All of the above are different.. In my experience though the biggest difference is in the beam quality. An inexpensive laser like this will very likely have horrible beam quality. This means it will be close to impossible to get good collimation and in turn good fiber coupling, assuming we are talking about coupling into a single mode fiber. Beam quality is usually reported as the M squared value, which represents how different the beam is from a perfect gaussian. The beam from lasers with a M2 value close to one can be focused to a diffraction limited spot. You would probably find that the beam from a laser like this cannot be focused to a spot much smaller than 10x or 100x larger than the diffraction limit. Which is not to say they are useless. If you don’t care about beam quality and you just need a lot of light they can certainly provide that. This laser for example could probably be used in place of an LED lamp for widefield fluorescence imaging.
Thanks! That’s a really helpful answer.