User:Andy Maloney/Notebook/Lab Notebook of Andy Maloney/2009/06/03/Laser diode stuff

First attempt

Today I received all the components to collimate the laser diode with a fiber setup. I'll have to make a Sketchup of what I've done but it is pretty straight forward. The first thing I did was to use a 200 µm core fiber and align the fiber such that I maximized the light output. Of course, I used the snazy new optics to collect and focus the light from the diode into the fiber. The new optic is a matched set of aspheres that has a NA on the diode side of 0.55 and an NA on the fiber side of 0.16. All the fibers I am using have an NA of 0.22.

After setting everything up, I tried getting light out of the fiber very quickly. This resulted in aligning the fiber such that it was not collecting the TEM₀₀ mode but another one. The output was a doughnut.

Sketchup

The items used are

• XY cage translator (x2)
• SMA to SM05 adapter
• 0.5" long SM05 lens tube
• 0.3" long SM05 lens tube
• SM05 to 9 mm asphere adapter
• Snazy optics
• SM05 to SM1 adapter (x2)
• SM1 to SM1 tube adapter
• Z translator
• Cage to post adapter

Second attempt

My second attempt was a little more careful but still I was cavalier about it. Instead of using a 200 µm fiber, I used a 400 µm one. Again, the fiber outputted a doughnut shape but after about 10 minutes of fussing, I was able to align the fiber such that it accepted the TEM₀₀ mode as well as other modes such that the output was a quasi-Gaussian beam.

This was just too easy! I love fiber collimation! If I have time tomorrow, I will continue to optimize the optics for this setup.