A Co-programmable Platform for Continuous-Wave Ultra-Broadband Nonlinear Mid-IR Vibrational Spectroscopy

This document corresponds to the current pre-final version of a doctoral thesis on continuous-wave nonlinear mid-infrared vibrational spectroscopy in dual-resonant plasmonic nanocavities. Conventional vibrational sum- and difference-frequency generation (SFG/DFG) provide interface-specific chemical fingerprints, but in practice their spectral access, stability, and reproducibility remain closely tied to ultrafast sources, synchronization, and phase-matching pipelines. This thesis addresses that constraint by defining and demonstrating a co-programmable measurement framework for local nonlinear vibrational readout.

The experimental implementation uses a dual-resonant nanoparticle-on-slit nanocavity that co-localizes visible and mid-infrared fields at a single site, enabling MIR-addressed excitation with visible-frequency nonlinear readout. Broadband operation is achieved by sweeping a tunable continuous-wave MIR source across selected windows while keeping the visible pump and detection chain fixed. Post-fabrication FTIR resonance mapping is used to select source windows that overlap the measured enhancement landscape of each chip, allowing spectral access to be scheduled without changing the measurement class.

The thesis further defines the output as a standardized vibrational fingerprint composed of MIR-indexed, co-registered nonlinear spectra and drift-robust derived observables. An effective-response description is used to account for interference between resonant vibrational and non-resonant background contributions, enabling consistent fitting and comparison across devices and molecules.