Research

Optical Magnets

Controlling spin states using very small magnetic fields or radio-waves provides the opportunity to sense tiny changes in magnetic fields, caused by changes in oxidation states of ions or so on, within cells. I work on a special class of open-shell molecular semiconductors that can be interrogated about the magnetic field around them, to which they answer by changing the colour of light they emit! My interests specifically lie in understanding the mechanism of such tiny magnetic field effects and using this knowledge to design better materials for biological integration.

We work with the group of Prof. Hugo Bronstein (Cambridge) and Dr. Petri Murto (Aalto) for the molecular synthesis. We work closely in collaboration with Dr. Alexei Chepelianskii (LPS-MESO, Paris-Saclay) for low-temperature, high magnetic field measurements and Dr. Sam Bayliss (Glasgow) for ODMR measurements. I also build magneto-radio-optical instrumentation, with custom controlling codes, for these investigations.

References:

Rituparno Chowdhury, Petri Murto, ..., Alexei Chepelianskii*, Hugo Bronstein*, Richard Friend*, Nature Chemistry, 17, 1410-1417 (2025)

Rituparno Chowdhury, Alistair Inglis, Lucy E. Walker, Petri Murto, ..., Alexei Chepelianskii*, Sam Bayliss*, Hugo Bronstein*, Richard Friend*, ArXiv preprint, 2510.09440 (2025)

Chiral semiconductors

Chirality is ubiquitious in nature, it helps distinguish left from right. It has huge impact on how biomolecules interact with each other and underpins crucial processes that support life itself. It is also of importance to semiconductor devices because it allows us to control electronic spin and photon polarisation in a material. I am interested in understanding and implementing chirality within molecular semiconductors using the interactions between molecules to make them stack like a corkscrew! Amazingly this allows us to use an efficient semiconducting core with chiral sidechains that act like guides for the twisted chiral stacking of these planar units. A major effort is now underway to understand the mechanism of how chirality manifests in the spin and photon polarisation in these supramolecular materials and what they can be used for in the future.

We work closely with the group of Prof. E. W. (Bert) Meijer (Eindhoven) for the synthesis of these chiral semiconducting units. Experiments are done locally using circular-polarisation instruments I have built in-house.

References:

Rituparno Chowdhury, Marco Preuss, ... , E. W. Meijer*, Richard Friend*, Science, 387, 1175-1181 (2025)

Magneto-Radio-Optics

I build custom instrumentation for the capability to measure magnetic field modulated or micro/radio-wave modulated changes in optical absorption and photoluminescence. This includes the option to time resolve the optical phenomena, being modulated by magnetics or radio-waves, from <1 nanosecond to >1 millisecond. The magnetic field range I work in is 0.1 milli-Tesla all the way up to 1.0 Tesla. I have also designed in the capability to implement complex radio/micro wave pulse sequences for mixing spin states. Do get in touch with our group (Richard Friend Group at Cambridge) if you would like to discuss a potential measurement!

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