DURIP Optical Parametric Oscillator (OPO), Transmission, and Electrical Test Upgrades for Nanoscale Far-IR Characterization of Twist-Optic and Semiconductor Materials
Abstract
PI-Caldwell is proposing an upgrade to the existing scattering-type scanning near-field optical microscope (s-SNOM) and nano-FTIR metrology suite present in his laboratory at Vanderbilt University to enable s-SNOM mapping into the telecom, mid-wave, and far-infrared (FIR) spectral ranges, perform s-SNOM and nano-FTIR measurements under applied electrical bias, and within transmission configurations. The Caldwell lab currently includes a s-SNOM and nano-FTIR tool that enables IR mapping at a fixed frequency or nano-FTIR ata fixed position with a spatial resolution on the order of 10-nm. However, the s-SNOM measurements are restricted to 6.1-7.0 µm and8.6-11.7 µm. Nano-FTIR enables a broader spectral range extending from 4.6-15.4 µm free-space wavelengths, but cannot be used for spectral mapping. Neither s-SNOM or nano-FTIR currently cover the telecom spectral band (Near-IR), most of the 3-5 µm atmospheric window, nor the far-IR, which are critical to many polaritonic, semiconductor, and twist-optic concepts of importance to the programs highlighted within the proposal.The proposed upgrade would dramatically expand the tool capabilities. Specifically, this would provide four major upgrades: 1) Extend the spectral range for s-SNOM measurements via an optical parametric oscillator (OPO)-based laser, which provides excitation between 1.4-2.02, 2.25-4.45, and 5-18 µm free-space wavelengths. This would dramatically expand the spectral range of operation for the existing s-SNOM, while also offering a significant increase in signal-to-noise. This upgrade would enable the measurement of optic phonon and free-carrier behaviors within wide-bandgap semiconductors, twist-optic structures, and a broad variety of two-dimensional (2D) materials instrumental for a broad array of DoD-sponsored programs, including a recently awarded MURI. 2) Enable single point spectroscopy mode, providing IR spectra over the same spectral range as the OPO, effectively extending the range of Nano-FTIR to include the NIR and FIR. This enables studies that are currently only possible through nano-FTIR with the light source provided via a synchrotron, such as the Advanced Light Source at the Lawrence Berkeley National Laboratory. 3) Additionof photocurrent electrical testing attachment. This would enable direct probing of materials and devices under non-equilibrium electric bias conditions, for instance moiré heterostructures as a function of Fermi energy, or semiconductor devices under forward and reverse bias, enabling experiments like exploring carrier redistribution for correlating semiconductor defects with device failure, and the induction of topological transitions in moiré and twist-optic heterostructures. 4) Enable s-SNOM and nano-FTIR measurements in transmission mode. Finally, inclusion of the transmission module is critical for measurements in waveguide geometries and many thin film sample measurements. The proposed instrumentation is designed to meet the challenges of current and future DoD programs, with PI Caldwell#s recently ONR MURI program the specific focus. This program aims to understand the role of crystal structure and symmetry in driving hybridization and strong coupling phenomena within moiré and twist-optic structures. These offer opportunities for active beam-steering and tuning of emitters, novel laser and electro-optic devices, polarization control including dictating chirality, and nonlinear optical responses within the IR. The expanded functionality will benefit a variety of DoD programs, including thoseat the Naval Research Laboratory and multiple universities including Vanderbilt, Penn State, and University of Virginia.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Mar 15, 2024
- Source ID
- N000142412233
Entities
People
- Joshua Caldwell
Organizations
- Office of Naval Research
- United States Navy
- Vanderbilt University