NEAR-FIELD AND FAR-FIELD MICROSCOPIC AND SPECTROSCOPIC CHARACTERIZATIONS OF COUPLED PLASMONIC, EXCITONIC AND POLYMERIC MATERIALS

Author

Chih-Feng WangFollow

Publication Date

Fall 11-14-2019

Abstract

The properties of localized surface plasmons (LSP) have been broadly utilized for chemical sensing, surface enhanced Raman spectroscopy, biomedical imaging and photothermal treatments. By exploiting well-established plasmonic effects, the spectroscopic investigation of intriguing quantum phenomena, such as excitonic interband and intersubband (ISB) transitions in semiconductor heterostructures, was examined and extended in both far- and near-field optical measurements. For far-field characterization, we used colloidal plasmonic Au nanorods (AuNRs) to increase the quantum efficiency of InGaAs/GaAs single quantum well. By analyzing the temperature-dependent photoluminescence enhancement as a function of GaAs capping layer thickness, we attributed the mechanism of the LSP enhancement to increased absorption and enhanced spontaneous emission by the Purcell effect. Using this far-field methodology, we suggest that colloidal plasmonic nanoparticles can serve as a nanoprobe for investigating carrier transport phenomena in semiconductor heterostructures. Additionally, scattering-type scanning near-field optical microscopy (s-SNOM) was applied to characterizing materials in the near-field. s-SNOM provides excellent spatial resolution with strongly enhanced electric fields at the AFM tip. Previously, the unknown vertical sensitivity of s-SNOM, especially for materials exhibiting weak tip-sample coupling, has limited the quantitative application of s-SNOM. We have demonstrated 5 nm vertical sensitivity at mid-infrared (mid-IR) wavelengths using a sloped, ultra-thin poly (4-vinylpyridine) (P4VP) polymer film limited only by the near-field phase reversal contrast and signal-to-noise-ratio of the Au substrate. In addition, we have developed a new parameter-free methodology to measure the fundamental optical properties (e.g., complex dielectric function) of such ultra-thin films over a broad frequency range using near-field microscopy. Finally, integrating s-SNOM with a broadband pulsed IR source and exploiting Fourier transform infrared (FTIR) spectroscopy technique, known as nano-FTIR allows spectroscopy with nanoscale spatial resolution to be performed. We conducted nano-FTIR experiments using a system where the LSP of a single plasmonic nanoantenna was coupled to the ISB transition in an InGaAs/AlInAs QW stack. For the first time, we observed strong light-matter interaction in a single nanoantenna. The dispersion characteristics of the nanoantenna coupled to the ISB polariton states were probed by varying the nanoantennae sizes.

Degree Name

Optical Science and Engineering

Level of Degree

Doctoral

Department Name

Optical Science and Engineering

First Committee Member (Chair)

Terefe G. Habteyes

Second Committee Member

Kevin J. Malloy

Third Committee Member

Alejandro Manjavacas

Fourth Committee Member

Hou-Tong Chen

Fifth Committee Member

Oleg Mitrofanov

Keywords

Localized surface plasmon, Near-field microscopy, nano-FTIR, Quantum well, Intersubband, Photoluminescence

Document Type

Dissertation

Language

English

Recommended Citation

Wang, Chih-Feng. "NEAR-FIELD AND FAR-FIELD MICROSCOPIC AND SPECTROSCOPIC CHARACTERIZATIONS OF COUPLED PLASMONIC, EXCITONIC AND POLYMERIC MATERIALS." (2019). https://digitalrepository.unm.edu/ose_etds/74