Switching photochromic molecules adsorbed on optical microfibres

Area of Science:

• Optoelectronics
• Materials Science
• Physical Chemistry

Background:

• Organic photochromic molecules, such as spiropyrans, exhibit reversible color changes upon light exposure.
• Optical microfibres offer a platform for guiding light and interacting with adsorbed materials via evanescent fields.
• Controlling molecular states with light is crucial for developing advanced optical devices.

Purpose of the Study:

• To optically control and measure the internal state of spiropyran molecules adsorbed on optical microfibres.
• To investigate the dynamics and limits of repeatable photochromic switching.
• To model the photoswitching behavior and assess photochemical degradation.

Main Methods:

• Adsorption of spiropyran molecules onto optical microfibres.
• Optical control using the evanescent field of guided light (nanowatt power levels).
• Measurement of state-dependent light absorption and time-resolved photoswitching dynamics.
• Modeling of switching dynamics using a rate equation model.
• Assessment of photochemical degradation over multiple switching cycles.

Main Results:

• Demonstrated optical control of spiropyran internal states via microfibre evanescent fields.
• Achieved repeatable switching between molecular states using low-power guided light.
• Quantified photoswitching dynamics and developed a predictive rate equation model.
• Investigated the system's endurance, determining the number of switching cycles before significant degradation.

Conclusions:

• Optical microfibres provide an effective platform for low-power, reversible control of photochromic molecular states.
• The study offers a quantitative understanding of spiropyran photoswitching dynamics and degradation.
• Findings are relevant for the design of novel optoelectronic devices and molecular switches.