Spaser Spectroscopy with Subwavelength Spatial Resolution

TL;DR

This paper introduces a high-sensitivity, subwavelength spectromicroscopy technique using a spaser-based scanning probe that leverages plasmon pumping by quantum dots, enabling high spatial resolution and spectral sensitivity.

Contribution

It proposes a novel spaser-based spectromicroscopy method utilizing quantum dot pumping, differing from traditional laser irradiation, and analyzes its spectral and sensitivity characteristics.

Findings

Narrow dips in plasmon spectrum indicate molecular absorption.

Sensitivity peaks near the spaser generation threshold.

High spatial resolution determined by tip curvature.

Abstract

A new method for high-sensitivity subwavelength spectromicroscopy is proposed based on the usage of a spaser (near-field laser) in the form of a scanning probe microscope tip. The high spatial resolution is defined by the tip's curvature, as is the case for apertureless scanning near-field optical microscopy. In contrast to the latter method, we suggest using radiationless plasmon pumping by neighbouring quantum dots instead of irradiation of the tip by an external laser beam. The spaser generation spectrum is analyzed. The plasmon generation is suppressed due to absorption at the transition frequencies of the neighbouring nano-objects (molecules or clusters) under study. As a result, narrow dips appear in the wide plasmon generation spectrum. Further, the highest sensitivity is achieved near the spaser generation threshold. The sensitivity of the spaser spectromicroscope is estimated.