160 research outputs found
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Plastic fiber design for THz generation through wavelength translation
We report on an all-fiber Terahertz (THz) radiation source by exploiting nonlinear parametric process in a theoretically designed microstructured-core double clad plastic fiber (MC-DCPF). The required phase-matching condition is satisfied through suitable tailoring of the fiber dispersion and nonlinear properties at the pump wavelength of a high power CO2 laser, with a CO laser of much lower power acting as a seed concomitantly. Our simulated results reveal that a THz radiation source at the frequency of ~ 3 THz could be realized with a 3-dB phase-matching band-width of 2.13 GHz in a 65 m long optimized MC-DCPF. Maximum power conversion efficiency >1% is realizable even after including the material loss
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An efficient polarization converter for Mid-IR wavelength
Design of a silicon-based polarization converter through phase matched power coupling between TE and TM modes is presented. Conversion efficiency up to 90% is feasible at 3 μm wavelength with device length of 536 μm
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Design of a compact SOI polarization rotator for mid-IR application
Design of a compact polarization rotator (PR) exploiting power coupling through phase matching between the TM mode of a strip waveguide (WG) and TE mode of a vertical slot WG is presented. Optimized cross sectional dimensions of the coupler have been achieved to use this device as a compact PR at 3 μm wavelength with device length of just 2 mm. We also investigate the device performance at the operating wavelength (λ) = 1.55 μm
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Design and Performance Study of a Compact SOI Polarization Rotator at 1.55 mu m
We numerically design a compact silicon (Si) based polarization rotator (PR) by exploiting power coupling through phase matching between the TM mode of a Si strip waveguide (WG) and TE mode of a Si-air vertical slot WG. In such structures, the coupling occurs due to horizontal structural asymmetries and extremely high modal hybridness due to high refractive index contrast of Si-on-insulator (SOI) structure. Design parameters of the coupler have been optimized to achieve a compact PR of ~135 μm length at the telecommunication wavelength of 1.55 μm. Maximum power coupling efficiency Cm, which is studied by examining the transmittance of light, is achieved as high as 80% for both polarization conversions. Fabrication tolerances and the band width of operation of the designed PR have also been studied
Specialty Fibers for Terahertz Generation and Transmission: A Review
Terahertz (THz) frequency range, lying between the optical and microwave frequency ranges covers a significant portion of the electro-magnetic spectrum. Though its initial usage started in the 1960s, active research in the THz field started only in the 1990s by researchers from both optics and microwaves disciplines. The use of optical fibers for THz application has attracted considerable attention in recent years. In this paper, we review the progress and current status of optical fiber-based techniques for THz generation and transmission. The first part of this review focuses on THz sources. After a review on various types of THz sources, we discuss how specialty optical fibers can be used for THz generation. The second part of this review focuses on the guided wave propagation of THz waves for their transmission. After discussing various wave guiding schemes, we consider new fiber designs for THz transmission
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Design of a Polymer-Based Hollow-Core Bandgap Fiber for Low-Loss Terahertz Transmission
We use numerical simulations to design a hollowcore microstructured polymer optical fiber (HC-mPOF) suitable for broadband, terahertz (THz) pulse transmission with relatively low losses and small dispersion. The HC-mPOF consists of a central large air-core surrounded by periodically arranged wavelength-scale circular air holes in a hexagonal pattern, embedded in a uniform Teflon matrix. The THz guidance in this fiber is achieved by exploiting the photonic bandgap (PBG) effect. In our low index contrast Teflon-air (1.44:1) hexagonal periodic lattice, the PBG appears only for a certain range of non-zero values of the longitudinal wavevector. We have achieved PBG over a broad spectral range (bandwidth ~400 GHz) ranging from 1.65 to 2.05 THz in the proposed HC-mPOF. The achievable loss coefficient in our designed HC-mPOF is <;4 m-1 and the group velocity dispersion parameter is <;±5 ps/THz·cm over a 300-GHz bandwidth (1.65~1.95 THz)
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