Abstract-Integrated Silicon Photonic Crystals Toward Terahertz Communications

Withawat Withayachumnankul,   Masayuki Fujita, Tadao Nagatsuma,

https://onlinelibrary.wiley.com/doi/abs/10.1002/adom.201800401

The terahertz frequency range locates between 0.1 and 10 THz. This range accommodates atmospheric windows with staggering absolute bandwidth. It holds a potential for point‐to‐point wireless communications with an aggregate capacity reaching terabit per second in a range up to a kilometer. This unique capability is envisaged for backhauls between base stations and for local area networks. To this end, efficiency and compactness of the transceivers are crucial for successful large‐scale adoption. However, state‐of‐the‐art terahertz front ends are based on radio‐frequency or photomixing technologies that are inefficient, bulky, or complicated. In principle, as a neighbor of the microwave and optics domains, the terahertz band can leverage technologies from both sides to overcome those challenges. Recently, low‐loss integrated circuits based on photonic crystal waveguides are developed for routing terahertz waves. Here, a progress report on core components, including waveguides and diplexers, is presented. Additionally, the interfacing of the platform with electronic sources and detectors on one end, and with antennas for free‐space coupling on the other end, is discussed. Currently, the platform can support terahertz communications at a data rate over 10 Gbit s−1. Challenges and opportunities are discussed in the light of future development in this area.

Abstract-Design and Verification of Terahertz Wave Photoswitch Based on Silicon Photonic Crystal

Yi-He Liu, Jiang-Ming Kuang, Jing Xu,  Ji-Ning Yang, Shuang Zhang

https://dl.acm.org/citation.cfm?id=3195142&dl=ACM&coll=DL

In this paper, the filtering property of the terahertz waveband based on one-dimensional photonic crystal was studied and preliminary theoretical exploration for the two-dimension case is carried out. The effect of the lattice imperfection layers' refractive index upon the center frequency and intensity of the defect mode's transmission peak was deeply analyzed. It is proven that tuning the transmission frequency of the Terahertz wave can be accomplished by changing the incident angle of the Terahertz wave or altering the refractive index and width of the defect layers; changing the defect layer number can realize multi-channel filtering and tuning of the Terahertz wave. Thus they can be applied to design of the Terahertz optical switch. Finally, the electro-optical crystal Lithium Niobate and the ferroelectric liquid crystal material (FLC) are taken as the defect layer of the photonic crystal to design the Terahertz optical switch and the multi-channel filter. Optical switch control within a tunable frequency band of 100G can be achieved by using them.

Abstract-Photonic-crystal diplexers for terahertz-wave applications

Masahiro Yata, Masayuki Fujita, and Tadao Nagatsuma
https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-7-7835

A compact diplexer is designed using a silicon photonic-crystal directional coupler of length comparable to the incident wavelength. The diplexer theoretically and experimentally exhibits a cross state bandwidth as broad as 2% of the operation frequency, with over 40-dB isolation between the cross and bar ports. We also demonstrate 1.5-Gbit/s frequency-division communication in the 0.32- and 0.33-THz bands using a single-wavelength-sized diplexer, and discuss the transmission bandwidth. Our study demonstrates the potential for application of photonic crystals as terahertz-wave integration platforms.

© 2016 Optical Society of America

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Abstract- A Tunable Terahertz Photonic Crystal Narrow-Band Filter

Li, S. Liu, H. ; Sun, Q. ; Huang, N.
State Key Laboratory of Transient Optics and Photonics Technology, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an, China 
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?reload=true&arnumber=7017510&filter%3DAND%28p_IS_Number%3A7051313%29

We theoretically propose and investigate a magnetically tunable narrow-band terahertz filter based on a triangular lattice silicon photonic crystal with a point and two line defects. The optical properties of the filter have been analyzed in detail. It is found that a single resonant peak with the central frequency of$sim 1$ THz is existed in the transmission spectrum, which has a narrow full width at half maximum of <2 GHz. Moreover, under the control of an external magnetic field, transmission frequency and width of passband are adjustable, which reveals that the 2-D silicon photonic crystal waveguide with point and line defects can serve as a continuously tunable bandpass filter at the terahertz waveband.