Outreach

Dynamical emission of semiconductor lasers is behind many of our todays laser applications, including the backbone of the internet. Nevertheless, the characterisation of the emission dynamics of semiconductor lasers has been mostly restricted to the detection of their intensity dynamics. This has imposed a major limitation when comparing to theory. The dynamics of the laser emission is best represented in the so-called phase space, spanned by its dynamical variables. There may be only a few degrees of freedom (intensity, carrier density, optical frequency) spanning the phase-space to represent the state of a solitary semiconductor laser. But if the laser is subjected to delayed feedback, the phase space has an infinite number of dimensions.

In a paper, published this week in the prestigious journal Physical Review Letters, four researchers from IFISC introduce a method which enables them to experimentally characterise the dynamics of intensity, carrier density and optical frequency at the same time. We all know tomography as a powerful method to visualize the spatial structure of our body, but tomography can create spatial images of sections of any object. The presented methodology allows the authors to perform tomography of laser dynamics in its phase space.

The authors demonstrate the power of their approach by applying it to the characterisation of a semiconductor laser with delayed optical feedback. Although the characteristic phenomenon of Low Frequency Fluctuations has been studied for a long time, thanks to this new method and its added features, the authors provide new insights into the underlying mechanism and identify a before-overlooked case, the possible segmentation of the dynamical phenomenon into two or more independently developing segments.

Moreover, this approach facilitates a better characterisation of semiconductor laser dynamics in general, and direct comparisons with theory, thereby allowing for a better optimisation of semiconductor lasers in telecommunications and other applications.

Authors

Daniel Brunner, Miguel C. Soriano, Xavier Porte e Ingo Fischer are from the Institute for Cross-Disciplinary Physics and Complex Systems, IFISC (UIB-CSIC).

Citation

Daniel Brunner, Miguel C. Soriano, Xavier Porte i Ingo Fischer. (2015, 28 de juliol). «Tomography of a semiconductor laser’s emission dynamics», Physical Review Letters 115, 053901 (2015).