Smridhi Chawla | Searcharxiv

arXiv2026

Quantum Theory of Third-harmonic Generation in Epsilon-Near-Zero Materials

We present a theoretical framework, based on the Green's tensor quantization method, to describe third-harmonic generation in epsilon-near-zero (ENZ) materials and derive analytical, closed-form solutions for the generation efficiency. We validate our model against experimental measurements of wavelength- and angle-resolved third-harmonic generation efficiency from 30 nm-thin ITO nanolayers at low pump intensity, described under the undepleted pump approximation. Our results provide a local and scalar effective model for quantum nonlinear processes in dispersive and lossy ENZ media, and establishes a simple and reliable framework for investigating a variety of nonlinear optical phenomena with applications to quantum sensing, quantum information, and quantum nondemolition measurements.

physics.optics↗

arXiv2025

Enhancement of the Third Harmonic Generation Efficiency of ITO nanolayers coupled to Tamm Plasmon Polaritons

We study the enhancement of third harmonic generation in indium tin oxide nanolayers coupled to Tamm plasmon polaritons (TPPs). The TPPs are excited at the interface between a thin gold mirror and a silicon dioxide/silicon nitride (SiO2/Si3N4) distributed Bragg reflector with a 30nm-thick indium tin oxide (ITO) nanolayer embedded inside the topmost dielectric layer under the metal mirror. This ITO nanolayer exhibits epsilon-near-zero (ENZ) behavior at near infrared wavelengths. By tuning the angle of incidence and the TPP resonance conditions, we achieve sub-wavelength confinement of the electromagnetic field, resulting in a 8x enhancement of the nonlinear optical response of the structure compared to the isolated ITO nanolayer at its optimal ENZ condition. We further investigate the dependence of the THG signal on the incident angle and sample orientation, confirming that the enhancement is driven by the excitation of the TPP mode with a characteristic asymmetric behavior. Numerical simulations of local field factors based on the transfer matrix method (TMM) fully support our findings. Our study demonstrates that the TPP-ENZ platform offers a versatile and highly efficient approach to enhancing nonlinear optical processes, with potential applications in frequency conversion, optical signal processing, and the development of more efficient nonlinear photonic devices.

physics.optics↗