Publications

journal articles

1. Nano Letters

   A 1.5D Photonic Crystal Interface for Prism-Free, Near-Normal, Low-Background Photoluminescence

   Leyang Liu, Seemesh Bhaskar, Joseph Tibbs, Sudha Maria Lis S, Somnath Pandit, Shivakiran Bhaktha B N, and Brian T. Cunningham

   Nano Letters, Apr 2026

   Abs DOI Bib

   Photonic crystal gratings (PCGs) and photonic crystal Bragg mirrors (PCMs) are widely used to enhance photoluminescence (PL) in fluorescence-based biosensing, yet most implementations either rely on bulky prism coupling or suffer from strong background from uncoupled spontaneous emission, limiting system integration. Here, we experimentally demonstrate an all-dielectric PCG–PCM interface in which a TiO2 ridge-groove PCG is fabricated atop a TiO2/SiO2 Bragg mirror to form a 1.5D photonic crystal (PC). Bound states in the continuum-enabled resonances in the PCG increase PL spectral flux, polarization selectivity, and near-normal outcoupling, while the PCM suppresses broadband background via stopband filtering and improves PL extraction by recycling downward radiation through radiative boundary-condition engineering. Relative to standalone PCGs or PCMs, the interface achieves up to 5.2-fold improvement in signal-to-background ratio, supported by angle-resolved spectroscopy, back-focal-plane imaging, and numerical simulations. This 1.5D PC establishes a scalable, compact route to high-contrast fluorescence readout for next-generation biosensing and bioimaging.

   @article{liu15DPhotonicCrystal2026,
     title = {A 1.{5D} {Photonic} {Crystal} {Interface} for {Prism}-{Free}, {Near}-{Normal}, {Low}-{Background} {Photoluminescence}},
     volume = {26},
     issn = {1530-6984, 1530-6992},
     url = {https://pubs.acs.org/doi/10.1021/acs.nanolett.6c00687},
     doi = {10.1021/acs.nanolett.6c00687},
     language = {en},
     number = {13},
     urldate = {2026-04-13},
     journal = {Nano Letters},
     author = {Liu, Leyang and Bhaskar, Seemesh and Tibbs, Joseph and S, Sudha Maria Lis and Pandit, Somnath and Bhaktha B N, Shivakiran and Cunningham, Brian T.},
     month = apr,
     year = {2026},
     pages = {4489--4496},
   }

2. Optics Letters

   Purcell enhanced laser action using a super-Tamm cavity mode

   Sudha Maria Lis S, Somnath Pandit, Someprosad Patra, Faizan H. Lone, Nitesh Singh, Debamalya Banerjee, Rajesh V. Nair, and Shivakiran Bhaktha B N

   Optics Letters, Mar 2025

   Abs DOI Bib

   Optical Tamm structures have potential for the development of optoelectronic devices, provided they overcome the challenge of low-quality factor of modes and inherent losses associated with plasmonic metal films. In this work, we present lasing in a super-Tamm structure consisting of a silver thin film deposited on a 4-(dicyanomethylene)-2-methyl-6-(4- dimethylaminostyryl)-H-pyran (DCM) dye-doped polyvinyl alcohol (PVA) spacer layer coated on a SiO2/TiO2 one-dimensional photonic crystal with a lasing threshold of  0.07 mJ. The spectral line narrowing and threshold characteristics observed in the emission spectrum corroborate the realization of a waveguided super-Tamm laser. The bi-exponential temporal decay profile of the Tamm lasing modes with an average lifetime of 0.52 ± 0.02 ns confirms the Purcell enhancement of radiative intensity of the DCM dye when coupled to the super-Tamm modes.

   @article{lis_s_purcell_2025,
     title = {Purcell enhanced laser action using a super-{Tamm} cavity mode},
     volume = {50},
     issn = {0146-9592, 1539-4794},
     url = {https://opg.optica.org/abstract.cfm?URI=ol-50-6-1869},
     doi = {10.1364/OL.543288},
     language = {en},
     number = {6},
     urldate = {2025-03-16},
     journal = {Optics Letters},
     author = {Lis S, Sudha Maria and Pandit, Somnath and Patra, Someprosad and Lone, Faizan H. and Singh, Nitesh and Banerjee, Debamalya and Nair, Rajesh V. and Bhaktha B N, Shivakiran},
     month = mar,
     year = {2025},
     pages = {1869},
   }

conference articles & others

1. CLEO 2024

   Spatial Correlation of Whispering Gallery Modes in an Active Micro-Bottle Resonator

   Subhajit Dutta, Somnath Pandit, and B. N. Shivakiran Bhaktha

   In CLEO 2024, 2024

   Abs DOI Bib HTML

   The spatio-spectral imaging of active micro-bottle resonator (MBR) is performed and the spatial correlation of the whispering gallery modes (WGMs) are investigated in a dye-doped poly (methyl methacrylate) (PMMA) coated silica micro-bottle resonator.

   @inproceedings{dutta_spatial_2024,
     address = {Charlotte, North Carolina},
     title = {Spatial {Correlation} of {Whispering} {Gallery} {Modes} in an {Active} {Micro}-{Bottle} {Resonator}},
     isbn = {978-1-957171-39-5},
     url = {https://opg.optica.org/abstract.cfm?URI=CLEO_AT-2024-JTu2A.10},
     doi = {10.1364/CLEO_AT.2024.JTu2A.10},
     language = {en},
     urldate = {2024-09-12},
     booktitle = {{CLEO} 2024},
     publisher = {Optica Publishing Group},
     author = {Dutta, Subhajit and Pandit, Somnath and Shivakiran Bhaktha, B. N.},
     year = {2024},
     pages = {JTu2A.10},
   }

2. CLEO 2023

   Tamm Mode-Aided Amplified Spontaneous Emission in One-Dimensional Photonic Crystal Super-Tamm Structure

   Sudha Maria Lis S, Somnath Pandit, Someprosad Patra, Debamalya Banerjee, and Shivakiran Bhaktha B N

   In CLEO 2023, 2023

   Abs DOI Bib HTML

   The optical Tamm mode-aided amplified spontaneous emission in a super-Tamm structure consisting of a silver (Ag) thin film deposited on dye-doped polyvinyl alcohol (PVA) layer coated on a SiO2/TiO2 one-dimensional photonic crystal structure is presented.

   @inproceedings{S:23,
     author = {S, Sudha Maria Lis and Pandit, Somnath and Patra, Someprosad and Banerjee, Debamalya and N, Shivakiran Bhaktha B},
     booktitle = {CLEO 2023},
     journal = {CLEO 2023},
     keywords = {Atomic force microscopy; Modes; Photonic crystals; Scanning electron microscopy; Thin films; Titanium dioxide},
     pages = {FF2D.4},
     publisher = {Optica Publishing Group},
     title = {Tamm Mode-Aided Amplified Spontaneous Emission in One-Dimensional Photonic Crystal Super-Tamm Structure},
     year = {2023},
     url = {https://opg.optica.org/abstract.cfm?URI=CLEO_FS-2023-FF2D.4},
     doi = {10.1364/CLEO_FS.2023.FF2D.4},
   }