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Tao K.,Shenzhen University | Tao K.,Shenzhen Key Laboratory of Micro Nano Photonic Information Technology | Tao K.,University of Colorado at Boulder | Xiao J.-J.,Harbin Institute of Technology | Yin X.,University of Colorado at Boulder
Applied Physics Letters | Year: 2014

We present a versatile add-drop integrated photonic filter (ADF) consisting of nonreciprocal waveguides in which the propagation of light is restricted in one predetermined direction. With the bus and add/drop waveguides symmetrically coupled through a cavity, the four-port device allows each individual port to add and/or drop a signal of the same frequency. The scheme is general and we demonstrate the nonreciprocal ADF with magneto-optical photonic crystals. The filter is immune to waveguide defects, allowing straightforward implementation of multi-channel ADFs by cascading the four-port designs. The results should find applications in wavelength-division multiplexing and related integrated photonic techniques. © 2014 AIP Publishing LLC. Source


Tao K.,Shenzhen University | Tao K.,Shenzhen Key Laboratory of Micro Nano Photonic Information Technology
Physica Status Solidi - Rapid Research Letters | Year: 2013

A resonance splitting effect is investigated in a system composed of two cavities coupled by two unidirectional waveguides. Both theoretical analysis and numerical calculations demonstrate that the resonance splitting (indicating a coupling between the cavities) is independent of the phase shift between the cavities, which is in contrast to previous research where reciprocal waveguides are used. Moreover, this splitting can be tunable by an external magnetic field. Our findings offer a possibility to realize effective coupling between remote on-chip resonators, which is highly demanded in the next-generation photonic circuits. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Wu C.J.,Shenzhen University | Wu C.J.,Yuan Ze University | Liu C.P.,Yuan Ze University | Ouyang Z.,Shenzhen University | Ouyang Z.,Shenzhen Key Laboratory of Micro Nano Photonic Information Technology
Applied Optics | Year: 2012

An optical logic NOT gate (OLNG) is presented based on photonic crystal (PhC) waveguides without nonlinear materials and optical amplifiers. Also, a way of determining the operating parameters is presented. It is demonstrated through finite-difference time-domain simulations that the structure presented can operate as an OLNG. The optimized contrast ratio, defined as the logic-"1" output power divided by the logic-"0" output power, is found to be 297.07 or 24.73 dB. The size of the OLNG can be as small as 7a × 7a, where a is the lattice constant of the PhC. Further, the OLNG presented in this paper can operate at a bit rate as high as 2.155 Tbit?s, which is much higher than that of electronic or optical logic gates developed until now. Moreover, as it is not based on the nonlinear effect, the OLNG can operate at very low powers and a relatively large operating bandwidth. This is favorable for large-scale optical integration and for developing multiwavelength parallel-processing optical logic systems. © 2012 Optical Society of America. Source


Tao K.,Shenzhen University | Tao K.,Shenzhen Key Laboratory of Micro Nano Photonic Information Technology
Advanced Materials Research | Year: 2012

Based on coordinate transformation, we extend the theory of unidirectional surface mode at a plane interface to a more general case of arbitrary boundary. We provide direct simulations to prove the validity of extension. Because it depends only on the signs of off-diagonal elements in the tensor of permittivity (for TM mode) or permeability (for TE mode), the unidirectionality is robust in a wide range of frequency. Moreover, this kind of surface mode is fairly robust with smoothly changing surface. These properties are very useful to design compact nonreciprocal component with wide range of operating frequency in various cases, such as broadband isolators and circulators. © (2012) Trans Tech Publications. Source


Zheng G.,Shenzhen University | Zheng G.,Shenzhen Key Laboratory of Micro Nano Photonic Information Technology | She W.,Sun Yat Sen University | Ouyang Z.,Shenzhen University | Ouyang Z.,Shenzhen Key Laboratory of Micro Nano Photonic Information Technology
Applied Physics B: Lasers and Optics | Year: 2010

"Quasi-phase matching" is first introduced to the optical activity (OA) effect and a wave coupling theory for the quasi-phase-matched (QPM) OA effect in periodically poled "gyroelectric" crystals is developed. The OA effect is observed clearly even though the propagating direction of light deviates far from the optical axis in the QPM crystal with both optical activity and natural birefringence. The QPM OA effect provides a special way to determine the gyration coefficients that cannot be observed by the normal OA effect, and it provides a principle for building optical filters without external field. © 2009 Springer-Verlag. Source

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