Saikat Majumder

Bio: Saikat Majumder is an academic researcher from University of Calcutta. The author has contributed to research in topics: Multi-mode optical fiber & Waveguide. The author has an hindex of 2, co-authored 12 publications receiving 21 citations. Previous affiliations of Saikat Majumder include Techno India.

Semianalytical method to study silicon slot waveguides for optical sensing application

Abstract: High-index contrast slab and slot optical waveguides have a high index variation both along the lateral and vertical interfaces and are usually analyzed numerically, requiring large computer memory and time. In this article, their analysis is done semianalytically using an effective-index based matrix method. This method, which is computationally very fast, was earlier used successfully for low-index profile waveguide structures only and is now suitably modified for use in high-index contrast structures. The electric field profile of the waveguide structures is plotted and the effective refractive index at different wavelengths is calculated. The results are compared with results obtained from numerical techniques like finite element method, finite-difference time-domain, and beam propagation method and they match very well. The dependence of their different optical characteristics with the waveguide parameters is also studied. These studies will help in obtaining improved sensitivity of slot waveguides for sensing applications.

Design of low loss surface plasmon polariton waveguide and its use as hybrid Tamm sensor with improved sensitivity

Abstract: A compact, dielectric–metal–dielectric surface plasmon polariton (SPP) waveguide is designed that can have propagation lengths as high as several thousand microns. The dielectric layers surrounding the metal waveguide are actually periodic layers of different nanometer-sized dielectric pairs. By proper selection of the surrounding layer widths, a device with a controllable effective index and increased compactness can be designed. It can have a propagation loss

Study of characteristics of MMI devices using matrix approach

Abstract: Multimode Interference devices are analyzed semi-analytically using matrix approach. The propagation constant and mode profile of different modes of a multimode waveguide are determined. The field intensity for the combination of all the modes at different propagation distance is also obtained. The results are in accordance to the theory. The method can be extended to a singlemode-multimode-singlemode device where the concept of overlap integral is introduced at their interface. As this method consists of multiplication of 2X2 matrices, it is simple and computationally fast

Multilayered photonic integration on SOI platform using waveguide-based bridge structure

Abstract: A waveguide based structure on silicon on insulator platform is proposed for vertical integration in photonic integrated circuits. The structure consists of two multimode interference couplers connected by a single mode (SM) section which can act as a bridge over any other underlying device. Two more SM sections acts as input and output of the first and second multimode couplers respectively. Potential application of this structure is in multilayered photonic links. It is shown that the efficiency of the structure can be improved by making some design modifications. The entire simulation is done using effective-index based matrix method. The feature size chosen are comparable to waveguides fabricated previously so as to fabricate the proposed structure easily.

Segmented multimode to dual port slot couplers as compact optical sensors with improved sensitivity

Abstract: A segmented silicon based multimode to dual port slot structure on silicon-on-insulator platform is proposed which can be used as a refractive-index sensing device. The introduction of segmentation leads to tuning the effective index of the device which results in increasing compactness of the sensing device. Although the structure supporting TM mode is more compact than TE mode, but TE mode is considered here as vertical slots in the output section enhances optical signal in the slots for TE mode only. By considering dual output, the device length is reduced further as dual self-imaging length is less compared to single self-imaging distance for symmetrical multimode section input. The surface sensitivity of the structure has a typical value of∼2249 nm/RIU. Relative sensitivity can be calculated from the ratio of field amplitudes of the arms of the dual output. Matrix method and 2D FDTD is used for the entire analysis.⁠

Plasmonics for Telecommunications Applications.

Abstract: Plasmonic materials, when properly illuminated with visible or near-infrared wavelengths, exhibit unique and interesting features that can be exploited for tailoring and tuning the light radiation and propagation properties at nanoscale dimensions. A variety of plasmonic heterostructures have been demonstrated for optical-signal filtering, transmission, detection, transportation, and modulation. In this review, state-of-the-art plasmonic structures used for telecommunications applications are summarized. In doing so, we discuss their distinctive roles on multiple approaches including beam steering, guiding, filtering, modulation, switching, and detection, which are all of prime importance for the development of the sixth generation (6G) cellular networks.

High-sensitivity multi-channel refractive-index sensor based on a graphene-based hybrid Tamm plasmonic structure

Abstract: In this paper, we propose a high-performance refractive-index sensor at a near-infrared band based on a hybrid Tamm structure. The optical properties of this graphene-based hybrid Tamm plasmonic structure are analyzed and investigated by using the transfer matrix method (TMM). Due to the excitation of the guide mode resonance (GMR) and Tamm plasmon polariton (TPP) resonance, the structure can realize multi-channel perfect absorption. This structure can be utilized as a refractive index sensor because the position of the absorption peak is sensitive to the refractive index of the ambient layer. Therefore, we obtain the sensitivity to 950 nm per refractive index unit (nm/RIU) and figure of merit (FoM) of 161 RIU-1 after studying the performance under different structural parameters. We believe that the proposed configuration is expected to be used to manufacture high-performance biosensors or gas sensor devices and other related applications in the near-infrared band.

Numerical and Experimental Analysis of On-Chip Optical Wireless Links in Presence of Obstacles

Abstract: In this work, we analyze the effects of the presence of waveguides in a wireless on-chip optical channel, which act as obstacles for the rays composing the propagating signal. The analysis has been performed numerically by using the FDTD method, and the simulation results have been validated by the experimental characterization. This work focuses on the relationship between the received signal and the position of the obstacles on the circuit plane in a multilayered channel made of heterogeneous dielectric cladding. We show how the crossing waveguide perturbates the received power and we provide ad hoc guidelines for the best topological choices allowing to mitigate losses. Moreover, with a good agreement between numerical and experimental results, amounting to a variation of less than 1 dB, we have demonstrated that the effects of this perturbation in real chips can be predicted. The results of this analysis, as well as increasing the level of knowledge of on-chip optical wireless links, allow a better comprehension and control of unbound optical signals within the optical chip environment.

Improvement of integrated electric field sensor based on hybrid segmented slot waveguide

Abstract: Integrated electric-field (E-field) sensors are commonly used devices in E-field sensing. However, distortion in the modulated signal due to high half-voltage ( V π ) and obtaining a low-frequency response are challenging issues in low-frequency AC E-field sensors. The aim of this study is to investigate a modification by adding a Si layer beneath a segmented slot waveguide (SSW) and optimizing the hybrid SSW as the core of a sensor to determine the sensor features in terms of the frequency response and sensitivity. The results of reducing the Si-layer thickness and segment width with high periodicity revealed a high modulation efficiency for very low-frequency AC E-field sensors and simultaneously expanded the minimum limit of detection by incorporating sensors in very small AC E-fields. This study validated the feasibility and efficiency of using a hybrid SSW as the core of highly sensitive low-frequency AC E-field sensors.

Indistinguishability and collection efficiency of transition metal dichalcogenides single photon emitters embedded in silicon nitride photonic integrated circuits

Abstract: This work explores the impact of waveguide design in photon collection efficiency and indistinguishability of single photon emitters embedded in photonic integrated circuits. Transition Metal Dichalcogenides (TMDC) materials have been selected as single photon emitters because their prominent properties for single photon emission: their giant oscillator strength promotes a stronger Purcell effect and their short exciton lifetimes enhances the indistinguishability of photons. We have calculated the photon extraction efficiency and the indistinguishability of a TMDC point-source of photons with arbitrary orientation embedded at an arbitrary location within a SiN waveguide. For the calculation we propose an analytical model based in the Green dyadic of the Helmholtz equation for different geometries of the waveguide, position of the source and orientation. Calculations have been numerically evaluated through finite-difference time-domain (FDTD) simulations showing consistent results. We have found a maximum coupling up to 81% to the fundamental mode when the quantum emitter is placed in the centre of the waveguide and a maximum indistinguishability of 81% when the emitter is placed 10 nm away from the edge of the waveguide. The results help for a better understanding of the coupling of quantum emitters to nanophotonic devices and photonic integrated circuits (PICs).