Coherence Buildup and Nonlinear Dynamics in Mesoscale Lasers

活动时间： 03月29日15时30分       

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讲座内容：

Coherent light sources are nowadays ubiquitous in scientific research and engineering applications. Lasers, a powerful coherence light source, have been miniaturized since the first device realized in 1960 by Th. Maiman. Physically, the onset and development of laser coherence is largely affected by the reduction in cavity size, but this does not become apparent until its volume reaches that of the smallest Vertical Cavity Surface Emitting Lasers (VCSELs). Thus the following questions arise: At what point in the buildup of laser emission does coherence set in? How does it develop? How do we define “threshold”? Is there a unique “threshold value” and does it exist at all for a nanolaser? What is the dynamical response to modulation in this uncharted territory?

In this work we explore the regime of laser operation around what is conventionally called “the threshold point” and obtain experimental answers to some of the questions from “mesoscale” lasers (i.e., lasers whose size is intermediate between the macroscopic and the nanoscopic scales). Correlation functions, temporal dynamics,phase space reconstruction, statistical indicators and spatially-resolved intensity and emission wavelength measurements are used as indicators to find the answers we are looking for. The dynamical response is investigated by applying a sinusoidal modulation to very small VCSELs, where we obtain the extreme events. Finally, the two-dimensional (2D) characterization of the emission properties in a plane transverse to the laser beam shows the correlation between the buildup of coherence in the smallest device and the establishment ofa laser mode (preceded by the stabilization of the emission wavelength). For somewhat larger devices, we pave the way to the spatial investigation of coherence buildup through the simultaneous 2D characterization of intensity distribution and emission wavelength obtained with the help of an instrument developed in the course of this work.

主讲人介绍：

王涛，加拿大国立研究所博士后研究员，从事非线性光学、半导体激光物理、光-物质微腔相互作用、材料合成表征方向的研究。

发布时间：2017-03-28 15:00:53