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In 1929, von Neumann and Wigner showed that Schrödinger’s equation can have, somewhat surprisingly, bound states above the continuum threshold [1]. These bound states represent the limiting case of quasi-bound states with an infinite lifetime, i.e., resonances that do not decay. It was recently realized that bound states in the continuum (BICs) are intrinsically a wave phenomenon and are thus not restricted to quantum mechanics. Since then, they have been shown to occur in many different fields of wave physics such as acoustics and photonics.
In photonics’ terminology, BICs are eigenmodes of an open system with an infinite radiation quality factor, Qrad. To take advantage of this unique property to design high quality resonant cavities, most investigations have focused on dielectric structures that, unlike their plasmonic counterparts, are not limited by their material quality factor, Qmat [3-5]. To investigate the properties of BICs, various platforms have been used such as 1D gratings [3], waveguide arrays [4], and 2D photonic crystal slabs [5].
In this contribution, we have designed a high quality cavity based on a BIC and harnessed its novel properties to achieve a compact low-threshold nanophotonic laser.
[1] J. von Neumann and E. Wigner, “On some peculiar discrete eigenvalues” Phys. Z, 465 (1929).
[2] C. Linton et al., “Embedded trapped modes in water waves and acoustics” Wave Motion 45, 16 (2007).
[3] D. C. Marinica et al., “Bound states in the continuum in photonics” Phys. Rev. Lett. 100, 183902 (2008).
[4] Y. Plotnik et al., “Experimental observation of optical bound states in the continuum” Phys. Rev. Lett. 107, 183901 (2011).
[5] C. W. Hsu et al., “Observation of trapped light within the radiation continuum” Nature 499, 188 (2013).
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