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Focusing of Terahertz Waves onto Micron-sized Slits Grown on ZnTe and GaP Substrates
서민아,H. R. Park,박두재,A. J. L. Adam,P. C. M. Planken,김대식 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.1
We report on terahertz focusing through rectangular slit apertures on thin metal film by using terahertz time domain spectroscopy both in the far- and in the near-field. Our experiments show that far-field perfect transmission is maintained in the rectangular slit array even as the aperture coverage decreases. Near-field imaging supports the field enhancement in the single rectangular aperture indeed occurring at a frequency equal to the fundamental shape resonance frequency.
Seo, M A,Adam, A J L,Kang, J H,Lee, J W,Jeoung, S C,Park, Q H,Planken, P C M,Kim, D S Optical Society of America 2007 Optics express Vol.15 No.19
<P>We present 2D measurements of the full THz electric field behind a sample consisting of multiple slits in a metal foil. Our measurements, which have a sub-wavelength spatial, and a sub-period temporal resolution, reveal electric field lines, electric field vortices and saddle points. From our measurements we are able to reconstruct the magnetic field and, finally, the position and time-dependent Poynting vector which shows the flow of energy behind the sample. Our results show that it is possible to study the flow of light near sub-wavelength plasmonic structures such as slit-arrays and, by implication, other metamaterial samples.</P>
Terahertz near-field vectorial imaging of subwavelength apertures and aperture arrays.
Knab, J R,Adam, A J L,Nagel, M,Shaner, E,Seo, M A,Kim, D S,Planken, P C M Optical Society of America 2009 Optics express Vol.17 No.17
<P>We present measurements of the complete terahertz (THz) electric near-field distribution, E(x), E(y) and E(z), in both the time- and frequency-domains, for subwavelength apertures and subsections of subwavelength aperture arrays. Measuring the individual components of the THz near-field with subwavelength spatial resolution, as they emerge from these structures, illustrates how the field interacts with the apertures. We observe the small but measurable y- and z-components of the electric field for both single apertures and arrays. Resonant contributions, attributed to Bloch modes, are detected and we observe the presence of a longitudinal field component, E(z), within the different array apertures, which can be attributed to a diffractive effect. These measurements illustrate in detail the individual THz field components emerging from subwavelength apertures and provide a direct measure of two important mechanisms that contribute to the net transmission of light through arrays.</P>
Terahertz field enhancement by a metallic nano slit operating beyond the skin-depth limit
Seo, M. A.,Park, H. R.,Koo, S. M.,Park, D. J.,Kang, J. H.,Suwal, O. K.,Choi, S. S.,Planken, P. C. M.,Park, G. S.,Park, N. K.,Park, Q. H.,Kim, D. S. Springer Science and Business Media LLC 2009 Nature photonics Vol.3 No.3
Plasmon Enhanced Terahertz Emission from Single Layer Graphene
Bahk, Young-Mi,Ramakrishnan, Gopakumar,Choi, Jongho,Song, Hyelynn,Choi, Geunchang,Kim, Yong Hyup,Ahn, Kwang Jun,Kim, Dai-Sik,Planken, Paul C. M. American Chemical Society 2014 ACS NANO Vol.8 No.9
<P>We show that surface plasmons, excited with femtosecond laser pulses on continuous or discontinuous gold substrates, strongly enhance the generation and emission of ultrashort, broadband terahertz pulses from single layer graphene. Without surface plasmon excitation, for graphene on glass, ‘<I>nonresonant laser-pulse-induced photon drag currents</I>’ appear to be responsible for the relatively weak emission of both <I>s</I>- and <I>p</I>-polarized terahertz pulses. For graphene on a discontinuous layer of gold, only the emission of the <I>p</I>-polarized terahertz electric field is enhanced, whereas the <I>s</I>-polarized component remains largely unaffected, suggesting the presence of an additional terahertz generation mechanism. We argue that in the latter case, ‘<I>surface-plasmon-enhanced optical rectification</I>’, made possible by the lack of inversion symmetry at the graphene on gold surface, is responsible for the strongly enhanced emission. The enhancement occurs because the electric field of surface plasmons is localized and enhanced where the graphene is located: at the surface of the metal. We believe that our results point the way to small, thin, and more efficient terahertz photonic devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-9/nn5025237/production/images/medium/nn-2014-025237_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5025237'>ACS Electronic Supporting Info</A></P>