[3분논문] 제17회 - 단방향 광도파로

황용섭의 3분논문 제17회입니다.

총시간은 4분 27초입니다.

재미있게 들어보세요.

# 방송 바로 듣기

1. 17_3분논문_제17회.mp3

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팟캐스트 검색: "3분논문"

팟캐스트 주소: http://itunes.apple.com/us/podcast/3bunnonmun/id568397433

RSS 피드: http://www.iblug.com/xml/itunes/3minpaper.xml

# 논문표지

# 간단한 정보

글쓴이: Liang Feng, Ye-Long Xu, William S. Fegadolli, Ming-Hui Lu, José E. B. Oliveira,

          Vilson R. Almeida, Yan-Feng Chen and Axel Scherer

제목: Experimental demonstration of a unidirectional reflectionless parity-time metamaterial

        at optical frequencies

학술지: Nature Materials

발행년월: 2012년 11월

이어가기: http://dx.doi.org/10.1038/nmat3495

# 용어

- parity-time symmetry: 반전성-시간 대칭.

# 발췌

1.

Here, we show the experimental realization of chip-scale unidirectional reflectionless optical metamaterials near the spontaneous parity-time symmetry phase transition point where reflection from one side is significantly suppressed.

# 그림

Figure 2: Optical properties of 

the designed passive unidirectional reflectionless parity-time metamaterial.

a, Periodically arranged 760-nm-wide sinusoidal shaped combo structures are applied on top of an 800-nm-wide Si waveguide embedded inside SiO₂ to mimic parity-time optical potentials, in which imaginary part modulation is implemented with 14 nm Ge/24 nm Cr structures and 51 nm Si layers are for real part modulation. The designed parity-time metamaterial consists of 25 sets of top-modulated combo structures with a period of 575.5 nm and a width of 143.9 nm for each sinusoidal-shaped combo. c, Simulated reflection spectra of the device in forward (red) and backward (blue) directions. d, Spectrum of contrast ratio of reflectivities, showing high contrast ratios over the studied wavelength range from 1,520 to 1,580 nm. e, Simulated electric field amplitude distribution of light in the device, where incidence is set at boundaries of the parity-time metamaterial (marked with white lines) along + z/−z in the forward/backward direction.

Figure 3: Experimental implementation of

the passive unidirectional reflectionless parity-time metamaterial.

a, Configuration of waveguides on the SOI platform to measure reflection from the device. A single-mode waveguide directional coupler with about 3 dB of coupling ratio is designed to maximize the detected signal (see Supplementary Information). Tapered waveguides are also introduced to transfer light from the single mode in the 400-nm-wide Si waveguides to the fundamental mode in the proposed waveguide device and vice versa. b, SEM picture of the whole device before deposition of SiO₂ cladding. The fabricated device consists of 25 periods of Ge/Cr and Si sinusoidal combo structures with a period of 575.5 nm on top of theSi waveguide. c, Zoom-in SEM picture of the device, where the boxed area indicates a unit cell. The remaining HSQ resist and two kinds of sinusoidal combos can be seen on top of the waveguide.

# 결론

한 쪽 방향 반사를 거의 없앤 도파로를 실험적으로 구현하였다. 메타물질이라는 이름을 붙이는 것이 적당한지는 잘 모르겠다. 

# 같이 읽을 논문

같은 1저자와 교신저자가 작년에 매우 비슷한 내용으로 Science에 낸 논문이 있다. 함께 읽어보면 좋겠다. 다른 연구자들이 보낸 comment까지 함께 읽어보기를 추천한다.

글쓴이: Liang Feng, Maurice Ayache, Jingqing Huang, Ye-Long Xu, Ming-Hui Lu, Yan-Feng Chen,

            Yeshaiahu Fainman, and Axel Scherer

제목: Nonreciprocal Light Propagation in a Silicon Photonic Circuit

학술지: Science

발행년월: 2011년 8월

이어가기: http://dx.doi.org/10.1126/science.1206038

끝.

2012년 11월 26일