Multimodal Characterization of Materials with Instrumentation Development
Restricted (Penn State Only)
- Author:
- Hernandez, Landon
- Graduate Program:
- Electrical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 12, 2023
- Committee Members:
- Madhavan Swaminathan, Program Head/Chair
Zhiwen Liu, Chair & Dissertation Advisor
Xingjie Ni, Major Field Member
Tim Kane, Major Field Member
Hans Hallen, Special Member
Sri-Rajasekhar Kothapalli, Outside Unit & Field Member - Keywords:
- Ultrafast
Nonlinear
Multimodal
Nonlinear Characterization
SHG
Second Harmonic Generation
Photoluminescence
2D materials
WS2
Raman
Dual Clad Fiber
Fiber Laser
Soliton Self-Frequency Shift
Divided Pulse
Amplification
Monolayer
Hyperspectral Imaging
Dove Prism - Abstract:
- Optical imaging techniques have played an instrumental role in the discovery and development of many technologies. Silica or silicon based photonic devices have been the staple, for decades, from the near-infrared to the visible range of the spectrum. They are well understood and commercialized, providing cost-efficient solution to photonic sensing. However, they lack characteristics, such as a direct bandgap and a vanishing second-order component. Advances in the development of ultrafast (10-15) sources have opened the door for new novel techniques to be applied for characterization of emerging materials and established the field of nonlinear optics. Transitional metal dichalcogenides (TMD), have recently garnered significant interest due to the attractive characteristics they exhibit, such as direct bandgap, semi-conducting and superconducting capability, and large second-order susceptibility, when synthesized down to a single layer. The first part of this dissertation is focused on the study of such material using a multimodal approach. More complex nonlinear processes, such as coherent anti-stokes Raman spectroscopy, are becoming more popular but require multi-line excitation. Currently, optical parametric oscillators (OPO) and amplifiers (OPA) are the workhorses in the field but provide only two colors (only one independently tunable), require a large footprint, are quite expensive, and complicated to align. Therefore, the growing need for multi-line, stable, compact optical sources must continue to be met, which is the main topic of the second part of this dissertation. Chapter 1 provides a short introduction for this dissertation. Chapter 2 presents a multimodal approach for exploration of emerging materials. It combines photoluminescence (PL) imaging and second-harmonic generation (SHG) techniques with complementary characterization capabilities. As-grown Tungsten disulfide (WS2) monolayers using chemical vapor deposition (CVD), have been extensively studied in the past decade and observed to exhibit multifactor PL edge enhancement. We apply this optical multimodality technique to understand what is happening in these regions. Then, we estimate the carrier lifetime, ~700ps, of the material by fitting a simple 2D diffusion model to our experimental data. Lastly, commercial Raman and atomic force microscopy (AFM) systems are also used to identify monolayer/bilayer regions. Improving our understanding of monolayer TMDs sheds new insight of their potential as future photonic devices. In chapter 3 we introduce a stable, compact, turnkey operation, fiber-based divided pulse soliton self-frequency shift (DP-SSFS) source demonstrated to generate up to 5.9W of usable average pump power, with the potential for more. The system can be configured for a single pulse or multi-pulse mode, up to 4 pulses. By tuning the power of each pulse, a soliton’s frequency can be shifted through intra-pulse stimulated Raman scattering (SRS). We observe interesting nonlinear optical processes at the output of the photonic crystal fiber (PCF). Lastly, in chapter 4, we present a 3D portable speckle imaging setup that, combined with a machine learning algorithm, can identify bacterial susceptibility of E coli in 60 minutes and urine samples in 120 minutes.