Optical Chaos with External Feedback Mirror

Background

Lasers have useful applications in our lives as clean, coherent light sources. However, lasers are not perfectly stable, and by feeding light back into the laser, one can create an unstable output. Manipulating the level of feedback, along with other variables, it has been shown that one can create “optical chaos”, or highly irregular and complex behavior in the power output. By nature, a chaotic system has an unpredictable output and is sensitive to slight changes in initial conditions. The output may at first seem random and disordered in strength, but it is really just complex behavior controlled by a deterministic rule (the Lang-Kobayashi equations).

Although it is difficult to find the usefulness of optical chaos in everyday life, with some ingenuity it has led to applications in optical communication security and random number generation. This experiment will only seek to prove that chaotic laser systems exist, and will not discuss synchronization in optical chaos (the idea that dual lasers can be "locked" in the same pattern") or verify any communication practically.

As you can imagine, there are several ways to feed light back into the laser cavity. (You may have even done so without noticing!). Here are a few configurations:

Goals

Set-up a valid semiconductor laser (FC 1550nm class B) experiment to induce optical chaos. • Prove the existence of optical chaos with experimental results o power output on oscilloscope o RF spectra • Observe chaotic behavior in a few regions of instability