Controlling Energy Flow in Biological Chromophores with Light–Matter Hybrid States
Mentors
Project Description
Light drives life. From photosynthesis in plants to vision in animals, biological systems rely on exquisitely tuned photophysical processes to convert and transport energy. This REU project will introduce undergraduate students to the emerging field of polariton biophotonics, where confined light inside an optical cavity strongly interacts with molecules to create new hybrid light–matter states called polaritons. These hybrid states can fundamentally reshape how energy flows through molecular and biological systems.
In the Son group, we investigate how strong light–matter coupling can be used to control molecular photophysics. When molecules such as chlorophylls or phthalocyanines are placed inside an optical microcavity, their electronic structure is modified by interaction with confined photons. This interaction can alter excited-state lifetimes, energy transfer pathways, and relaxation dynamics. In this REU project, the student will explore how polariton formation influences the energy relaxation dynamics of biologically relevant chromophores, including chlorophyll derivatives. The work connects directly to biophotonics by probing and engineering light-driven processes central to photosynthesis and bio-inspired energy conversion.
Research Goals
The primary goal of this project is to understand how strong light–matter coupling inside optical microcavities can be used to control the photophysical behavior of biologically relevant chromophores. In natural photosynthetic systems, molecules such as chlorophyll absorb light and convert it into excited states that drive energy transfer and chemical transformation. These processes are governed by delicate interactions between molecular structure and the surrounding electromagnetic environment. In this project, we aim to deliberately reshape that environment by placing chromophores inside optical cavities, where confined photons interact strongly with molecular excitations to form hybrid light–matter states known as polaritons.
By engineering these hybrid states, we seek to determine how the formation of polaritons alters excited-state lifetimes, energy relaxation pathways, and energy transport mechanisms. A central objective is to compare the dynamics of chromophores inside and outside the cavity to establish whether strong coupling can prolong excited-state coherence, redirect energy flow, or suppress loss pathways. Through steady-state and time-resolved spectroscopic measurements, the project will probe how modifications to cavity design and molecular composition influence these effects.More broadly, the project aims to establish fundamental design principles for controlling biological and bio-inspired light-harvesting systems using structured electromagnetic environments. By connecting cavity photonics with molecular photophysics, this work contributes to a deeper understanding of how light can be used not only to probe biological systems but also to actively engineer their energy flow.
Learning Goals
The learning goals of this project are centered on giving the student a rigorous and immersive introduction to modern biophotonics research while building both conceptual understanding and practical laboratory skills. Over the course of the program, the student will develop a working knowledge of light–matter interactions, excited-state dynamics, and the basic principles of optical cavities and strong coupling. Rather than encountering these topics only in textbooks, the student will see how they emerge in real experiments—how abstract concepts like energy levels, coherence, and relaxation pathways translate into measurable spectra and time-resolved signals. A key educational objective is to help the student connect foundational coursework in physics and chemistry to active research questions at the frontiers of photonics and molecular science.
Equally important are the technical and professional skills the student will cultivate. The project is designed to build confidence in hands-on experimental techniques, including optical alignment, sample preparation, and spectroscopic data collection. The student will also gain experience analyzing quantitative data and interpreting results in a critical, scientific manner. Throughout the program, emphasis will be placed on developing problem-solving skills, scientific communication, and the ability to work collaboratively within a research group. By the end of the experience, the student should not only understand the scientific goals of the project but also feel empowered as an emerging scientist—capable of designing experiments, troubleshooting challenges, and clearly articulating the broader significance of their work.
Timeline
Weeks 1-2: Foundations and Training
- Laboratory safety training and introduction to research environment
- Guided readings and discussions on light–matter interactions, optical cavities, and excited-state dynamics
- Introduction to basic optical components and alignment techniques
- Training on steady-state absorption spectroscopy and sample handling
- Initial data analysis exercises (MATLAB/Python)
Week 3-5: Sample Preparation and Cavity Characterization– Preparation of molecular thin films containing biologically relevant chromophores (e.g., chlorophyll derivatives)
- Fabrication and assembly of optical microcavities
- Collection of steady-state absorption and reflectivity spectra
- Identification and verification of polariton formation (e.g., Rabi splitting)
- Guided interpretation of spectral features and comparison to control samples
- Continued development of data analysis skills
Week 6-8: Time-Resolved Measurements
- Introduction to ultrafast spectroscopy instrumentation
- Participation in alignment and setup of time-resolved experiments
- Collection of excited-state dynamics data (inside and outside cavity)
- Extraction of lifetimes and other excited-state parameters and comparative analysis to assess effects of strong coupling
Week -10: Wrap-Up and Communication
- Final data analysis and figure preparation
- Interpretation of results in the broader context of biophotonics
- Preparation of research poster and/or oral presentation
