Publications

journal articles

1. APL Engg. Phys.

   Engineering highly directional Bloch surface wave-coupled augmented emission in perovskite nanocrystals-embedded photonic crystal

   Somnath Pandit, Rahul Murali, Prasanta Kumar Guha, Sai Santosh Kumar Raavi, and Shivakiran Bhaktha B. N.

   APL Engineering Physics, Dec 2026

   Abs DOI Bib

   Photonic crystals (PhCs) alter the emission properties of integrated emitters by modifying the local density of states, thereby controlling the spontaneous emission rate and directionality. However, the respective roles of photonic architecture and intrinsic emitter properties in determining the performance of coupled emitters under identical photonic environments remain less explored. In this work, two CsPbBr3 nanocrystals (NCs)—pristine (CPB) and Zn-alloyed CsPbBr3 (Zn-CPB), possessing 47% and 96% intrinsic quantum yields, respectively—are integrated in a one-dimensional photonic crystal (1D-PhC) to study the Bloch surface wave (BSW)-based emission enhancement and directionality. Transfer matrix method simulations were employed to optimize the PhC architecture and ensure efficient spectral overlap between the BSW resonance and the emission spectra of both emitters. Both the NCs exhibit polarized, highly directional emission (<4° angular spread) and a comparable lifetime reduction upon coupling to the BSW. Under identical excitation conditions, both emitters exhibit nearly 280-fold enhancement in 1D-PhC coupled emission. Despite experiencing comparable relative enhancement, Zn-CPB produces substantially stronger photonic crystal-coupled emission intensity owing to its higher emission efficiency and absorption cross-section. These findings establish that, while the relative photonic enhancement and Purcell factor estimated from the lifetime reduction are primarily governed by the PhC architecture, the achievable absolute directional emission intensity is strongly determined by the intrinsic emissive properties of the emitter. Consequently, comparable photonic enhancement does not necessarily translate into comparable emission intensity, highlighting the importance of considering both coupling conditions and emitter characteristics in the design of highly efficient directional light sources.

   @article{panditEngineeringHighlyDirectional2026,
     title = {Engineering highly directional {Bloch} surface wave-coupled augmented emission in perovskite nanocrystals-embedded photonic crystal},
     volume = {1},
     issn = {3066-7380},
     url = {https://pubs.aip.org/aep/article/1/4/046102/3401262/Engineering-highly-directional-Bloch-surface-wave},
     doi = {10.1063/5.0331886},
     language = {en},
     number = {4},
     urldate = {2026-08-17},
     journal = {APL Engineering Physics},
     author = {Pandit, Somnath and Murali, Rahul and Guha, Prasanta Kumar and Raavi, Sai Santosh Kumar and Bhaktha B. N., Shivakiran},
     month = dec,
     year = {2026},
     pages = {046102}
   }

2. Adv. Opt. Mat.

   Bloch Surface Wave‐Coupled Enhanced Fluorescence on a Nano‐Assembly–Photonic Crystal Hybrid Interface for Ultrasensitive Detection

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

   Advanced Optical Materials, Jul 2026

   Abs DOI Bib

   ABSTRACT There is an ever‐increasing demand for miniaturization and portability of reliable sensor platforms for individualized health monitoring in diagnostics. Photonic crystals (PC)‐based frameworks in conjugation with fluorescence techniques efficiently address these requirements on account of their high sensitivity, compactness, and robust integrated features. Here we demonstrate fluorophore emission engineering via Bloch surface waves (BSWs) supported by one‐dimensional PCs. Since brighter emission directly translates to improved detection performance, achieving highly sensitive PC platforms necessitates careful interfacial nano‐engineering. In this context, cryosorets, which are hybrid nano‐assemblies composed of gold nanoparticles (AuNPs) and TiO 2 nanorods (TiO 2 NRs), are used to generate three‐dimensional multi‐fold hotspots. When interfaced with a PC, the resulting metallo‐dielectric hybrid yields photonic crystal‐coupled emission (PCCE), mitigating the challenge of fluorescence quenching. The nanoscale gaps between the plasmonic AuNPs, high refractive index (HRI) TiO 2 NRs, and graphene oxide (GO) hybrid interface generate strong hotspots, augmenting the fluorescence coupling via the underlying BSW. Integrating such sensors onto smartphones and other personalized devices to enable rapid, on‐site sensing of target analytes is need of the hour. The high 1300‐fold PCCE enhancement enables attomolar sensing of rhodamine reporter molecule and is demonstrated here using a smartphone camera as a detector amenable for resource limited settings.

   @article{sBlochSurfaceWaveCoupled2026,
     title = {Bloch {Surface} {Wave}‐{Coupled} {Enhanced} {Fluorescence} on a {Nano}‐{Assembly}–{Photonic} {Crystal} {Hybrid} {Interface} for {Ultrasensitive} {Detection}},
     issn = {2195-1071, 2195-1071},
     url = {https://advanced.onlinelibrary.wiley.com/doi/10.1002/adom.71496},
     doi = {10.1002/adom.71496},
     language = {en},
     urldate = {2026-08-17},
     journal = {Advanced Optical Materials},
     author = {S, Sudha Maria Lis and Liu, Weinan and Bhaskar, Seemesh and Pandit, Somnath and Cunningham, Brian T. and Bhaktha B. N., Shivakiran},
     month = jul,
     year = {2026},
     pages = {e71496}
   }

3. 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},
   }

4. 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},
   }