Raman optical activity (ROA) is a powerful tool for identifying the absolute conformational information and behavior of chiral molecules in aqueous solutions, but suffers from low sensitivity. Here we report our development of a silicon nanodisk array that tailors a chiral field to significantly increase the interaction between the excitation light and chiral molecules via exploiting a dark mode. Specifically, we used the array with pairs of chemical and biological enantiomers to show >100x enhanced chiral light-molecule interaction with negligible artifacts for ROA measurements. Our silicon nanodisk array opens a cost-effective way for conformational analysis of trace chiral molecules.
We discuss recent advances in light-matter coupling in quantum dots with a point-defect nanocavity in a woodpile three-dimensional
(3D) photonic crystal with the highest quality (Q) factor among those for 3D photonic crystal cavities. The
Q factor over 10,000 was so far achieved by optimizing the size of the defect cavity, in which the defect was not so large
that power loss into the in-plane direction limited the Q factor.
We demonstrate quantum dot (QD) based continuous-wave photonic crystal (PhC) nanocavity laser operates at room temperature with a very low effective threshold power of ~ 375 nW. The continuous-wave lasing was achieved at 1.3 μm with InAs/GaAs self-assembled QDs and high quality PhC nanocavity with a quality factor of 87,000. The light-in versus light-out curve shows no sharp threshold unlike conventional lasers with pronounced kinks around the thresholds.
This near-thresholdless behavior with smooth transition from thermal to coherent light region indicates that this nanocavity laser has a very high spontaneous emission coupling efficiency. The temporal coherence of such a high-β laser was studied by interference measurements. We also discuss the characteristics of background noise of QD based PhC nanocavity lasers compared with quantum well based PhC nanocavity lasers.
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