Whispering-gallery mode lasers for biosensing: a rationale for reducing the lasing threshold

Alexandre François; Nicolas Riesen; Hong Ji; Shahraam Afshar Vahid; Tanya M. Monro

doi:10.1117/12.2076889

3 March 2015 Whispering-gallery mode lasers for biosensing: a rationale for reducing the lasing threshold

Alexandre François, Nicolas Riesen, Hong Ji, Shahraam Afshar Vahid, Tanya M. Monro

Proceedings Volume 9343, Laser Resonators, Microresonators, and Beam Control XVII; 93431U (2015) https://doi.org/10.1117/12.2076889
Event: SPIE LASE, 2015, San Francisco, California, United States

Abstract

Whispering-gallery modes have been studied extensively for biosensing applications. Whilst the vast majority of work undertaken has focused on high Q factor resonators, with the main improvement being a reduction of the resonator size to improve sensitivity, we have chosen a different pathway by starting with resonators that exhibit extremely high refractive index sensitivity but low Q factor. A way forward to overcome this limitation is to introduce a gain medium and operate the resonator above its lasing threshold. This has been shown to result on average in a 5 fold increase in the Q factor. With the lasing threshold itself being dependent on the Q factor, amongst other parameters, the Q factor enhancement can be exploited to either reduce the lasing threshold or alternatively enable smaller resonators to be operated above their lasing threshold. As a demonstration we present a 10 μm diameter polystyrene microsphere lasing in aqueous solution for refractive index sensing applications, which to the best of our knowledge is the smallest polystyrene microsphere laser ever demonstrated in these conditions.

Citation Download Citation

Alexandre François, Nicolas Riesen, Hong Ji, Shahraam Afshar Vahid, and Tanya M. Monro "Whispering-gallery mode lasers for biosensing: a rationale for reducing the lasing threshold", Proc. SPIE 9343, Laser Resonators, Microresonators, and Beam Control XVII, 93431U (3 March 2015); https://doi.org/10.1117/12.2076889

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