Oral Presentation, Theme J : NEMs, MEMs, Nano-Fluidics, Nano-Actuators, Nano-Sensors, Nano-robotics Photonic Nano-Metamaterials: Science Meets Magic Ekmel Ozbay Nanotechnology Research Center, Bilkent University Bilkent, Ankara 06800 TURKEY Abstract: The word “magic” is usually associated with movies, fiction, children stories, etc. but seldom with the natural sciences. Recent advances in metamaterials have changed this notion, in which we can now speak of “almost magical” properties that scientists could only dream about only a decade ago. In this article, we review some of the recent “almost magical” progress in the field of photonic nanometamaterials. Keywords: Metamaterials, Photonics, Nanolithography Starting in high school physics, we learn that light is Besides negative refraction, scientists have shown made of a combination of electric and magnetic fields. that metamaterials can also be used to achieve “almost As light propagates through matter, conventional magical” applications such as subwavelength imaging, materials only react to the electric field, in which this super lenses, perfect lenses, cloaking, chirality etc. interaction results in most of the optical effects that we Although the early experiments were performed at know of, such as refraction, diffraction, lensing, microwave frequencies, it took only a few years for the imaging, etc. 40 years ago, Prof. Veselago asked the scientists to downscale these structures to optical question “what if matter also interacts with the magnetic frequencies [ 4 ]. These nano-scale metamaterials are now field of light?” [ 1 ]. He showed that when both electric called as photonic metamaterials. and magnetic properties were negative ( � <0 and μ <0), As shown in Figure 1, SRRs can be fabricated with the solution of the Maxwell equations resulted in an dimensions reaching nanometer scales. The nano-scale SRR acts as an LC resonator with a resonance frequency index of refraction with a negative sign. The theoretical predictions of Prof. Veselago had to at optical frequencies [ 5 ]. More importantly, the typical size of these resonant inclusions is approx. 10 times wait ~30 years for the first experimental realization of these engineered materials that are also called smaller than the vacuum wavelength of the light at the resonance frequency. Although a single-layer SRR metamaterials. The seminal work of Sir John Pendry [ 2 ] provided the blueprints for the experimental realization structure can easily be fabricated on a dielectric surface, it is relatively difficult to stack these structures due to the of metallic based resonant structures that are called split tight alignment tolerance requirements. Prof. Harald ring resonators (SRRs), which exhibit μ <0 at the Giessen and his group members have reported a new resonance frequencies. Smith et al. [ 3 ] combined an method where metamaterials in the near-infrared spectral array of SRRs ( μ <0) and an array of metallic wires ( � <0) region can be fabricated using a layer-by-layer technique in order to create double negative composite [ 6 ]. metamaterials. In such a case, the famous “right handed Conventional SRRs provide a neat way to achieve rule” between the electric and magnetic fields becomes magnetism at optical frequencies. In order to excite the left-handed, in which these materials are known as left- magnetic resonance of the SRR, the incoming light handed materials (LHMs) or negative index materials should propagate in a direction that is parallel to the SRR (NIMs). 1 156 6th Nanoscience and Nanotechnology Conference, �zmir, 2010
Oral Presentation, Theme J : NEMs, MEMs, Nano-Fluidics, Nano-Actuators, Nano-Sensors, Nano-robotics Terahertz Wave Emission from Intrinsic Josephson Junctions of High-T c Superconducting Mesas Lütfi Özyüzer 1* , H. Köseo�lu 1 , F. Türko�lu 1 , Y. Demirhan 1 , Y. �im�ek 2 , T. Yamamoto 3 , K. Kadowaki 3 , H. B. Wang 4 , P. Müller 2 1 Department of Physics, Izmir Institute of Technology, Izmir, Turkey 2 Department of Physics, University of Erlangen, Erlangen, Germany 3 University of Tsukuba, Tsukuba, Japan 4 National Institute of Materials Science, Tsukuba, Japan Abstract— The natural structure of single crystal Bi 2 Sr 2 CaCu 2 O 8+d (Bi2212) is considered as c-axis tunnel junctions between sets of superconducting CuO 2 planes, which are called intrinsic Josephson junctions (IJJ). Recently, we experimentally demonstrated that rectangular IJJ mesa structures of Bi2212 can be used as a compact solid state generator of continuous, coherent and polarize terahertz (THz) radiation source, which a reliable source does not exist around this frequency range. The simple voltage-frequency relation in AC Josephson effect is valid and higher frequencies require higher bias for over 600 junctions in series. The mesa structures were fabricated on various Bi2212 single crystals, and current-voltage and THz emission characteristics were investigated. We will discuss recent experimental results of THz wave generation from Bi2212 crystals. Terahertz sensing and imaging is a rapidly developing example of bolometer response during I-V measurement. The technology with applications including security, medicine, frequency of the emission is around 0.35 THz for this mesa. quality control etc [1]. There is a need for compact Furthermore, one of the radiating mesas will be shown that continuous wave (CW) solid-state terahertz source with Josephson voltage frequency relation has to be satisfied for the practical power. There are some available CW sources such THz emission. as quantum cascade lasers that only work above 1.2 THz. 40 Multiplication of Gunn diodes produces low output powers. 30 20 Backward wave oscillators are bulky and have low output 10 I (mA) power at higher frequencies. Optically pumped THz gas 0 lasers are also bulky and not tunable. -10 -20 Single crystal of high temperature superconductors (HTSs) -30 (a) e.g. Bi 2 Sr 2 CaCu 2 O 8+� (Bi2212), forms perfect layered structure -40 0.2 as a superlattice and these natural stacks of SIS multi- 0.1 junctions are called intrinsic Josephson Junctions (IJJs). Each 0 Lock-in (mV) junction is 1.5 nm thick and separated by Bi-O and Sr-O -0.1 -0.2 layers. The experimental observation of IJJ in Bi2212 single -0.3 crystals was an important achievement because close -0.4 proximity of tunnel junction couples Josephson junctions [2]. -0.5 (b) Since the IJJs are naturally stacked along the c-axis of Bi2212 -0.6 -1500 -1000 -500 0 500 1000 1500 V (mV) single crystals, they exhibit anisotropic electrical behaviors. Figure 1: (a) Current-voltage characteristics of 100x300 � m 2 mesa at The tunneling current-voltage (I-V) characteristics of IJJs 20 K (b) Bolometer response during I-V measurements. The arrows show THz emission voltages. along the c-axis of Bi2212 exhibit large hysteresis and multiple branches. * ozyuzer@iyte.edu.tr The successful observation of THz emission by our group stimulated studies on THz generation from intrinsic Josephson R EFERENCES junctions of Bi2212 mesas [3]. The fundamental frequencies [1] M. Tonouchi, “Cutting-edge terahertz technology,” Nature Photonics 1 , of observed emission were as high as 0.85 THz and radiation 97 (2007). [2] R. Kleiner, F. Steinmeyer, G. Kunkel, and P. Müller, “Intrinsic power was up to 0.5 � W which are not achieved before. It is Josephson effect in Bi 2 Sr 2 CaCu 2 O 8 single crystals.” Phys. Rev. Lett. 68 , shown that the emission frequency is proportional to the 1/w, 2394 (1992). where w is with of mesa and indicating that Josephson plasma [3] L. Ozyuzer, A. E. Koshelev, C. Kurter, N. Gopalsami, Q. Li, M. Tachiki, K. Kadowaki, T. Yamamoto, H. Minami, H. Yamaguchi, T. frequency has to match the cavity resonance of mesa for Tachiki, K. E. Gray, W.-K. Kwok, U. Welp, “Emission of Coherent THz successful emission. Recently, one order larger radiation Radiation from Superconductors,” Science 318 , 1291 (2007). power (~ 5 � W) and higher harmonics (up to 4 th corresponds [4] K. Kadowaki, H. Yamaguchi, K. Kawamata, T. Yamamoto, H. Minami, I. Kakeya, U. Welp, L. Ozyuzer, A. E. Koshelev, C. Kurter, K. E. Gray, to 2.5 THz) of resonance have been obtained [4]. and W.-K. Kwok, “Direct observation of terahertz electromagnetic Many theoretical studies accomplished to explain waves emitted from intrinsic Josephson junctions in single crystalline mechanism of THz generation from Bi2212 mesas. There is Bi 2 Sr 2 CaCu 2 O 8+d, ”, Physica C 468 , 634 (2008). [5] L. Ozyuzer, Y. Simsek, H. Koseoglu, F. Turkoglu, C. Kurter, U. Welp, no consensus right now and need more experimental input for A. E. Koshelev, K. E. Gray, W. K. Kwok, T. Yamamoto, K. Kadowaki, complete proof of a theory. In this study, we will present Y. Koval, H. B. Wang and P. Müller, "Terahertz wave emission from generic properties of THz radiating mesas, such as resistivity intrinsic Josephson junctions in high-Tc superconductors", Supercond. Sci. Technol. 22, 114009 (2009). versus temperature (R-T) and I-V [5]. Figure 1 shows an 157 6th Nanoscience and Nanotechnology Conference, �zmir, 2010
Recommend
More recommend
