Research Projects

Light propagation through high-quality(Q) factor optical resonators has attracted considerable interest towards the development of nano-photonic devices. It can contribute to controlling the characteristics of light propagation by modifying the interaction between light and the material medium at the subwavelength scale. Therefore, they are indispensable for a wide range of photonic applications such as sensing, filters, and lasing. High-Q-factor optical resonators are commonly demonstrated using micro-ring excitation through in-plane near-field coupling by the optical fiber. However, it is crucial to realize a resonator that can operate in free space and to observe excited high-Q modes in experiments. Typically, a resonant architecture such as a guided-mode resonance (GMR) structure consists of a grating on a thin-film waveguide that can support various photonic modes, which may be utilized to achieve high Q-factors and accessed in free space. Grating diffracts the incident light, and one of the diffracted orders couples to the waveguide and propagates as a guided mode. However, some of the leaky waveguide modes interfere with the free-space propagating wave and contribute to the high Q-factors in GMR structures, yielding a narrow resonance spectrum either in reflection or in transmission geometry. Designing such structures is possible as the theory of GMR supports the possibilities of getting a very high Q-factor, but it is still challenging, especially for different spectral regimes of interest. At the same time, it is in demand to fabricate those optical resonators following the optimized design parameters, which is limited by material and fabrication constraints, together with experimentally perceiving a large Q-value. In this proposal, we will focus on the design and fabrication of a high-Q guided-mode resonances platform by engineering the structure, targeting applications as optical sensing, filtering, and quantum light sources for free-space nanophotonic devices. The development of various optical resonators and their contribution have been studied by other groups earlier. However, there are still challenges and requirements for detailed analysis of the feature parameters and reviewing the fabrication techniques to minimize imperfections that can make them more suitable for attaining such a high-Q in the GMR-based resonance structures. Besides the fabrication deformity, the modal characteristics of the light are very much dependent on the shape, size, and height of the grating, along with the waveguide thickness of these resonators. Careful engineering of those critical parameters can mitigate the light-matter interaction, resulting in the realization of efficient high-Q resonances. In addition, besides the large field enhancement, high-Q nanostructures can be integrated directly onto a flat substrate, concerning the miniaturization of the next-generation photonic devices, which may offer control of the light spatially and spectrally.