Denghui Pan

About Me

I am Denghui Pan, a first-year Ph.D. student in the ECE Department at the University of California, Santa Cruz, working with Prof. Holger Schmidt. Now I am in collaboration with the Department of Astronomy and Astrophysics to develop cutting-edge spectrometers-on-a-chip for astronomy applications. Previously, I conducted research on ultrafast fiber lasers and transient laser dynamics in Prof. Hongyan Fu’s group at Tsinghua University. My current research interests mainly focus on Chip-scale Spectrometers, Deep-learning Based Spectrometer, Ultrafast Time-resolved Laser Spectroscopy, Integrated Optofluidics, and Spectral Analysis.

Education

University of California, Santa Cruz

Fall 2024 - Present

Ph.D. in Electrical and Computer Engineering

Tsinghua University

2020 - 2023

M.S. in Data Science and Information Technology

Zhejiang University of Technology

2013 - 2017

B.S. in Safety Engineering

News

[Aug 2024] I joined the Applied Optics Group in ECE, UCSC!

Projects

Deep Learning for Spectral Reconstruction with Multimode Interference (MMI) Chips - This project introduces a novel computational spectrometer that leverages a multimode interference (MMI) chip to encode spectral information into unique 2D spatial interference patterns. We employ a deep learning model, specifically a Convolutional Neural Network (CNN) with SE-modules and residual connections, to accurately reconstruct the original spectrum from these patterns. The model is trained using a multi-task loss function for enhanced accuracy in both spectral shape and peak prediction, and its robustness is improved through data augmentation with complex, synthetic spectra. This approach aims to create a compact, high-performance alternative to traditional spectrometers.

Research on Linear Polarization-maintaining NPE Mode-locked Fiber Laser - I designed and constructed an innovative ultrafast fiber laser utilizing the principle of Nonlinear Polarization Evolution (NPE) for mode-locking in a Polarization-Maintaining (PM) erbium-doped fiber laser. The novelty of this work lies in the incorporation of a novel wavelength-division multiplexer (WDM) collimator integrated device, contributing to a more compact laser architecture. The resultant laser demonstrates stable output of ultrashort pulses at a repetition rate of 60.9 MHz.

Research on Transient Dynamics of Dissipative Solitons in Mode-locked Fiber Lasers - By employing Time-Stretch Dispersion Fourier Transform (TS-DFT) technique, I investigated the dynamic process of dissipative soliton formation within an anomalous dispersion fiber laser. The construction of dissipative solitons revealed five distinct transient stages: relaxation oscillations, modulation instability, spectral broadening, soliton explosion, and stable mode-locking state. Notably, during the soliton explosion phase, the existence of dissipative rogue waves was discovered. This finding significantly contributes to comprehending the evolutionary dynamics of dissipative soliton formation within nonlinear dissipative systems.

Research on Ultra-compact Femtosecond Fiber Laser Product - This project aims to transition the research-oriented, dispersion-managed, polarization-maintaining, erbium-doped femtosecond fiber laser (referred to as the fiber laser) developed within our laboratory into an industrialized product. The goal is to create a compact, portable, stable, and adaptable fiber laser product suitable for various complex engineering environments. The fiber laser employs full-polarization-maintaining fiber with erbium-doped gain medium and features a nine-mirror cavity structure. By adjusting the lengths of positively and negatively dispersive fibers, the net dispersion within the cavity can be controlled, yielding pulses with different characteristics. When approaching near-zero dispersion, the laser generates femtosecond pulses. In an industrial setting, the fiber laser is pumped by butterfly-packaged laser diodes for energy supply. Mode-locking is achieved by rotating an internal polarizing waveplate to ensure stable pulse output. During the product design phase, the precise components of the laser were modeled using Solidworks. These components were fabricated by a precision machinery factory, followed by assembly and performance testing of the laser to meet industrial-grade standards. This prototype is capable of generating stable laser pulses at 97 MHz with an impressively narrow pulse width of only 293 femtoseconds. This product has been included in multiple research project and grant applications, including the Tsinghua SIGS Concept Verification Project (Fiber Lasers for Biomedical Imaging) and the Overseas Research Cooperation Fund (Coexistence and Evolution of Bright and Dark Solitons in Mode-Locked Fiber Lasers).

Research on Hybrid Mode-locked Fiber Laser Based on Nonlinear Multimodal Interference - The project involved the design of a novel semi-polarization-maintaining erbium-doped fiber laser. A distinctive approach was employed, utilizing a reflective multi-mode interference saturable absorber (SA) for mode-locking. Within this specially designed SA, linearly polarized light was coupled into a 15 cm long gradient refractive index multi-mode fiber through polarization-maintaining fiber. The light was then reflected back into the polarization-maintaining structure via a mirror connected to a single-mode fiber. The measured modulation depth and saturation peak power were 1.5% and 0.6 watts, respectively. This laser generated mode-locked pulses of 409 femtoseconds at a repetition rate of 33.3 MHz. Compared to traditional nonlinear polarization evolution (NPE) mode-locking in non-polarization-maintaining fiber lasers, this laser exhibited superior optical performance metrics, including spectral bandwidth, pulse duration, and stability.