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SUMMARY:Replacing metals with alternative materials for mid-IR to THz plas
 monics and metamaterials – does it make sense?
DTSTART:20171013T151500
DTSTAMP:20260407T181239Z
UID:d1d028a3dd17028c0c1c7e5554268f7ca003dc7b6abdbab73deb53a6
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Jacob B. Khurgin\, Department of Electrical and Compute
 r Engineering\, Johns Hopkins University\, Baltimore\, USA\nMetals\, which
  dominate the fields of plasmonics and metamaterials suffer from large ohm
 ic losses which tends to dampen the lofty promise of nanoplasmonics and me
 tamaterials. Therefore it would be greatly beneficial to identify alternat
 ive materials with smaller loss that have negative real part of dielectric
  constant and can potentially replace the metals.\nNew plasmonic materials
 \, such as highly doped semiconductors including oxides and nitrides\, hav
 e smaller material loss combined with the negative epsilon in the IR range
 \, and using them in place of metals carries a promise of reduced-loss pla
 smonic and metamaterial structures\, with sharper resonances and higher fi
 eld concentration.  This promise is put to a rigorous analytical test in 
 this work and it is revealed that having low material loss is not sufficie
 nt to have a reduced modal loss in plasmonic structures\, unless the plasm
 a frequency is significantly higher than the operational frequency. Using 
 examples of nanoparticle plasmons and gap plasmons one comes to the conclu
 sion that even in the mid-infrared spectrum metals continue to hold advant
 age over the alternative media.\nAside from alternative plasmonic material
 s in the mid and far infrared ranges of the spectrum there exists a viable
  alternative to metals – polar dielectrics and semiconductors in which d
 ielectric permittivity (the real part) turns negative in the Reststrahlen
  region. This feature engenders the so-called surface phonon polaritons (S
 PhPs) capable of confining the field in a way akin to their plasmonic anal
 ogues\, the SPPs. Since the damping rate of polar phonons is substantially
  less than that of free electrons\, it is not unreasonable to expect that 
 “phononic” devices may outperform their plasmonic counterparts. Yet 
 a more rigorous analysis of the comparative merits of phononics and plasmo
 nics reveals a more nuanced answer\, namely that while phononic schemes do
  exhibit narrower resonances and can achieve a very high degree of energy
  concentration\, most of the energy is contained in the form of lattice v
 ibrations so that enhancement of the electric field\, and hence the Purc
 ell factor\, is rather small compared to what can be achieved with metal n
 anoantennas. Still\, the sheer narrowness of phononic resonances is expect
 ed to make phononics viable in applications where frequency selectivity is
  important.\nOverall\, for most of the application\, such as waveguide pro
 pagation and antenna the metals outperform the alternative materials but t
 hese new materials may still find application niche where the high absorpt
 ion loss is beneficial\, e.g. in medicine and thermal photovoltaics.\n \n
 About the research of the speaker: https://engineering.jhu.edu/ece/facult
 y/khurgin-jacob-b/\n 
LOCATION:CE 1 5 https://plan.epfl.ch/?room==CE%201%205
STATUS:CONFIRMED
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