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Achromatic waveplate in THz frequency region based on the structured parallel metal plates. Ashida Lab Noriyuki Mukai. Contents. Introduction waveplate based on the structured parallel metal plates THz Magnet-Optical spectroscopy Summary and future’s prospects.
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Achromatic waveplate in THz frequency region based on the structured parallel metal plates Ashida Lab Noriyuki Mukai
Contents • Introduction • waveplate based on the structured parallel metal plates • THz Magnet-Optical spectroscopy • Summary and future’s prospects
Polarization-controlled spectroscopy in THz frequency region Material characterization - Polarization dependent spectroscopy circularly dichroic molecules magnetic resonance Hall effect ….. - Polarization modulation spectroscopy Applications - beam isolator - encoding for displacement sensor - THz communication
Waveplate in THz frequency stacked six birefringent quartz plates Fresnel Rhomb JieShan,OSA(2009) Masson and Gallot OL (2006) Birefringence of subwavelengthgrating Narrow band waveplate based on metamaterial Weis et al APL (2009) Delacroix et al OE (2012)
Adjusting CEP of single-cycle THz pulsewith parallel metal plates 10mm g TE L=10mm TEM Nagai et al. Proc. otst 2013. Nagai et al. IRMMW-THz 2013 Th11-3 Phase-Sensitive THz Nonlinear Spectroscopy In High-TC Superconductor Thin Film
Parallel metal waveguide with metal hole array λ/2 resonance frequency : ν0=c / √3p A. Bingham, Y. Zhao, and D. Grischkowsky, Appl. Phys. Lett. 87, 051101 (2005).
Structured parallel metal plate waveguide E for TE mode E for TM mode • TM wave propagates slowly • Positive phase perturbation due to the high-frequency resonance of the structure n0 • →constant phase difference in wide frequency region
Our works We fabricated the low-cost THz phase shifter using an array of structured parallel metal plates, which works the wave plate with small deviation of phase shift in wide frequency region. We also demonstrated the generation of intense circularly-polarized THz pulse with multi and single cycle.
Fabrication of the structured parallel metal plates We fabricated several 50×10×0.03mm3 steel plates with the periodically placed holes by the chemical etching. They were arranged using the metal spacers L=10mm a=66mm q Ein g=1.5mm p=100mm Theoretically, the cut-off and the resonant frequencies should be nc=0.10 THz and n0=1.7 THz, respectively.
Experimental setup Nonlinear optical fiber +negative dispersion fiber 50fs Yb: fiber laser IMRA D1000 (100kHz 11mJ 470fs) Θ E// Ein EO detector (CdTe) E⊥ P2 45° P1 0 or 90 ° LiNbO3 emitter 1.0THz Bandpass filter
Achromatic waveplate based on structured parallel metal plates Within 5% deviation from p/2: from 0.67 to 1.21 THz
Achromatic waveplate based on structured parallel metal plates θ=45° θ=135°
Achromatic waveplate based on structured parallel metal plates θ=45° θ=135°
Achromatic waveplate based on structured parallel metal plates Fresnel rhome Shan OE 2004
Magnet-Optical Kerr Effect (MOKE) complex permittivity tensor : ε Light that is reflected from a magnetized surface can change in both polarization and reflected intensity. MO disk Mini Disk
Incident + ⇔ Rright≠Rleft + Kerr ellipticity η ⇔ θright≠θleft Kerr rotation φ + ⇔
THz Magnet-Optical spectroscopy Input/output module1 lens polarizer λ/4 waveplate Input/output module2 lens sample parabolic mirror
THz Magnet-Optical spectroscopy Sample: InSb
Summary and future’s prospects We demonstrate the broadband achromatic quarter wave plate based on the structured parallel metal plates. In our artificial medium available frequency region is 0.67THz to 1.21 THz (5% phase deviation). The center frequency and bandwidth of the wave plate based on the artificial medium can be controlled by the optimization of g, the thickness of the metal plate, and structure on the metal plates, so we can easily expand the available frequency region to the mid-infrared region. The wave plate based on the structured metal plates will open a new polarization-sensitive spectroscopy in infrared frequency region.
Sandblasting 25μm RSm(粗さ曲線要素の平均長さ): 30μm Ra(算術平均粗さ): 1.4μm