Abstract
A spaser consists of a plasmonic noble-metal nanostructure that acts as nanocavity, when incorporated or surface-coupled two-level emitters constitute the nanoscale gain medium. Suited two-level emitters are, for instance, laser dyes. Optical pumping may provide efficient excitation energy transfer between the two-level emitters in the gain medium and the surface plasmons sustained in the nanocavity. Strong resonant coupling of the surface plasmon modes to the gain medium may establish an inherent feedback amplification mechanism which finally drives the spaser action. In this contribution, we demonstrate that spaser emission can be generated by amplifying longitudinal surface plasmon modes in gold nanorods by optically pumping surface-attached resonantly-coupled laser dyes. Therefore, we synthesized gold nanorods whose longitudinal surface plasmon resonance peak was adjusted between 680 and 700 nm. The gain medium was realized by electrostatically attaching the laser dye phthalocyanine tetrasulfonate via the positively-charged CTAB (cetyltrimethylammonium bromide) bilayer to the gold-nanorod surface. Phthalocyanine tetrasulfonate exhibits fluorescence at 700 nm. Fluorescence quenching experiments unambiguously gave indication of resonant excitation energy transfer. The fluorescence intensity ratio I F 0 / I F follows the Stern–Volmer relationship, and the Stern–Volmer coefficient was determined as KSV = 1.22 × 106 M−1. The spaser emission was observed in fs transient absorption spectra as an ultrafast decaying narrow emission peak around 716 nm.
Highlights
The operating principle of a plasmonic nanolaser—the so-called spaser—is Surface Plasmon Amplification by Stimulated Emission of Radiation
A spaser consists of a plasmonic noble-metal nanostructure that acts as nanocavity, when incorporated or surface-coupled two-level emitters constitute the nanoscale gain medium
We demonstrate that spaser emission can be generated by amplifying longitudinal surface plasmon modes in gold nanorods by optically pumping surface-attached resonantly-coupled laser dyes
Summary
This nonradiative energy transfer to the spaser mode is the dominant process whose probability is by orders of magnitude greater than that of the free-space (far-field) emission In this contribution, we show that red spaser emission can be generated by amplifying longitudinal LSP modes in AuNRs via resonant excitation transfer from optically pumped laser dye molecules that are electrostatically surface-bound and operate thereupon as optical gain medium for the compensation of the plasmon losses. In contrast to pristine AuNRs [5], an additional narrow band at 716 nm emerges from the maximum of the longitudinal LSP bleach band that is red-shifted to 705 nm due to the changed environmental refractive index Such a sharp intensive peak at wavelengths, with negative ∆OD values and clearly red-shifted from the longitudinal LSP resonance and fluorescence emission of Pcts (700 nm) is typical for spaser emission. We will improve the performance of AuNR-based spaser by engineering heat-resistant surface coatings as optical gain media
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
