Awanish Pandey

Guided-Mode Analysis of Tamm-Plasmon Polariton at Metal–Heterostructure Dielectric Interface

We present a comprehensive analysis for transverse electric (TE) and transverse magnetic (TM) polarized guided Tamm-plasmon polariton (TPP) mode at metal-heterostructure media interface. We explicitly show that the quarter-wavelength stack condition will not be satisfied for TE or TM polarized TPP mode due to the existence of null-point at metal-heterostructure media boundary. Therefore, we propose an alternate route to design TPP waveguide by solving the mode-dispersion relation for different geometrical parameters in a TiO2/SiO2 bilayer system. The guided TPP-modes (TE and TM) exhibit interesting dispersion characteristics which can be tailored as per the desired application. The group index of TM polarized TPP mode remains constant over a significant wavelength range which results into zero group-velocity dispersion (GVD) at λ ≈ 630 nm wavelength. Also, the propagation length for TM-polarized TPP modes vary between 25 μm to 50 μm in a 630-650 nm wavelength range. However, the variation of GVD for TE-modes exhibit a monotonic variation with an exceptionally large GVD ≈ -3 × 104 ps/km·nm around λ = 632.8 nm.

Tunable mode hybridisation in compact SOI coupled ring cavity

We propose and experimentally demonstrate a coupled micro-ring cavity system. The cavity enables tunable resonance mode spacing, with mode spacing as low as 27.5 GHz is demonstrated in a footprint that is 87% less than a conventional single cavity system.

Optical single sideband generation using self-coupled micro ring resonator in SOI

Radio over fiber (RoF) has emerged as one of the most economical, high-bandwidth and low loss transmission for microwave signals [1]. In a simple RoF system, the optical carrier is modulated by an RF signal resulting in an optical carrier with sidebands also referred as Double Side Band (DSB) scheme. Though simple, the distribution of power in multiple sidebands make it power inefficient and susceptible to phase distortion due to chromatic dispersion in the fibre resulting in fading and signal degradation at the receiver end. These undesirable behaviour increase with RF signal frequency. One of the approaches to address this issue to us Optical Single Side Band (OSSB) transmission scheme [2]. Recently, OSSB generation using Bragg grating, Sangnac loop and micro-ring resonators has been demonstrated with sideband suppression of 12, 34.4 and 29 dB respectively [3-5].

Distributed-Bragg-Reflection Assisted Tailoring of Extraordinary Transmission Spectrum in Sub-Wavelength Hole Array

We present a novel route to tailor the spectral features of extraordinary transmission (EOT) through sub-wavelength periodic hole array using a distributedBragg-reflector (DBR). The photonic stop-bands and high transmission regions in the DBR spectrum results in the creation of new EOT peaks in those spectral regions where conventional EOT spectrum exhibits negligible transmission. Modal-analysis for the composite geometry elucidates that the existence of such unconventional EOT peaks are reinforced by the transmission resonances of DBR. Also, by creating suitable defect states in the DBR transmission spectrum, we show that the bandwidth of conventional EOT peaks could be tailored significantly and narrowed down to less than 0.1-nm linewidth.

Investigation of logarithmic spiral nanoantennas at optical frequencies

The first study is reported of a logarithmic spiral antenna in the optical frequency range. Using the finite integration technique, we investigated the spectral and radiation properties of a logarithmic spiral nanoantenna and a complementary structure made of thin gold film. A comparison is made with results for an Archimedean spiral nanoantenna. Such nanoantennas can exhibit broadband behavior that is independent of polarization. Two prominent features of logarithmic spiral nanoantennas are highly directional far field emission and perfectly circularly polarized radiation when excited by a linearly polarized source. The logarithmic spiral nanoantenna promises potential advantages over Archimedean spirals and could be harnessed for several applications in nanophotonics and allied areas.