Indium Antimonide (InSb) Cavity Resonators based on Planar Plasmonic Terahertz Waveguide
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Indium Antimonide (InSb) Cavity Resonators based on Planar Plasmonic Terahertz Waveguide Shourie Ranjana J.1, M. N. Satyanarayan2, G. Umesh3 Optoelectronics Laboratory, Department of Physics, NITK Surathkal, Mangalore-575025 Karnataka INDIA. 1 [email protected], [email protected], [email protected] ABSTRACT We present the studies of Terahertz (THz) Semiconductor-Insulator-Semiconductor (SIS) Planar Plasmonic waveguide of Indium Antimonide (InSb) with cavities along the waveguide acting as resonator. The Surface Plasmon Polariton (SPP) modes were confined in the SI interface and resonance behavior and filtering functionality of the device were demonstrated. The transmission characteristic of the structure depends on the interference effects between the SPP mode passing through the cavity and the one returning from the cavity. These effects were observed by studying the transmission from the SIS waveguide as a function of frequency and cavity length and proving analytically using the analogy with microwave transmission line network. Furthermore, we present the SIS cavity resonator’s transmission characteristics which vary with changes in the dielectric constant of the insulator region. Such a study was proposed to incorporate in the structure for sensing of biomolecules in THz region. INTRODUCTION Exploration to design sources and detectors for the Terahertz (THz) region of the electromagnetic spectrum has emerged into a new field as THz technology. Simultaneously the growing interest in the field of Plasmonics is converging to the THz regime. Typical THz frequency lies in the range from 0.1THz (3000µm) to 10THz (30µm). The efficiency of the available THz sources is very less, limiting the applications in high intensity studies. To circumvent the above limitation, larger confinement, strong localization and enhancement of the field are very critical for the development of THz devices. Plamonics has the ability to provide subwavelength optical confinement from the strong localization of SPPs at metal –dielectric interfaces [1]. Plasmonics has entered the THz region and have found profound application as promising candidates for future devices. The capacity of THz Plasmonics devices to sustain SPP modes has opened up a wide range of novel application in sensing, spectroscopy, imaging of biological tissues and security. Wide applications in THz Plasmonics require components like waveguides, power splitters, waveguide couplers, antennas, resonators, filters etc. [2]. THz Planar Plasmonic waveguide is one of such device in the THz technology that has attracted considerable attention in the recent years as wavelength selective filters. SPP mode confinement in the THz region is achieved by two approaches, either by perforating a flat metal surface periodically with holes and grooves to obtain spoof SPPs or SPPs excited at the interfaces of semiconductor-insulator instead of metal-insulator [2]. In this study, we have investigated the localization of SPP modes at THz frequencies, using InSb planar waveguide s
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