High-Q and modulation-depth PIT-like effect through the phase coupling between guided modes and Tamm state in a hybrid Tamm plasmon system

Abstract

High-quality (high-Q) resonators play a crucial role in optical-wave manipulation. It is challenging to excite guide modes in 1-D photonic crystals (PhC guided modes (PCGMs)) because of their high Q factors and complex patterns. To address this, a hybrid cavity Tamm plasmon (HCTP) structure composed of a metal film, cavity, and 1-D photonic crystal (1-D PhC) was designed. Subsequently, a grating was incorporated into the HCTP structure to diffract the electric fields of the HCTP resonance mode. This efficiently excited the PCGMs. When the detuning between the PCGM and HCTP modes approached zero, a plasmon-induced transparency (PIT)-like effect occurred. Under normal incidence, the PIT-like effect exhibited an impressively high Q factor (5015.5). The physical properties of the PIT-like effect were analyzed using the coupling mode theory. The results show that there is a strong phase coupling between PCGM and HCTP modes. This resulted in a modulation depth of 97.4 %. Under an oblique incidence, the degenerated PCGMs split into two modes. Both these were coupled with the HCTP mode. This resulted in a double PIT-like effect with a high modulation depth. The Q factor was enhanced further to 8957.7. Active modulation of the PIT-like spectra was achieved by modifying the incident or polarization angle. The coupling also exhibited slow-light properties, with a group delay of 17.54 ps under inclined incidence. The strong coupling between PCGM and HCTP resulted in the generation of high-Q and deep-modulation PIT-like effect. These hold high potential for various applications such as nanosensing, slow-light devices, nanolasers, and angle detectors.