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

Masson and Gallot OL (2006) Weis et al APL (2009) Delacroix et al OE (2012) Fresnel Rhomb Jie Shan,OSA (2009) stacked six birefringent quartz plates Birefringence of subwavelength grating Narrow band waveplate based on metamaterial Waveplate in THz frequency

Adjusting CEP of single-cycle THz pulse with parallel metal plates TE L=10mm TEM g 10mm Nagai et al. Proc. otst 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 A. Bingham, Y. Zhao, and D. Grischkowsky, Appl. Phys. Lett. 87, (2005). resonance frequency : ν 0 =c / √3p λ/2

Structured parallel metal plate waveguide TM wave propagates slowly Positive phase perturbation due to the high-frequency resonance of the structure 0 →constant phase difference in wide frequency region E for TE mode E for TM mode

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 9/14 We fabricated several 50×10×0.03mm 3 steel plates with the periodically placed holes by the chemical etching. They were arranged using the metal spacers Theoretically, the cut-off and the resonant frequencies should be c =0.10 THz and 0 =1.7 THz, respectively.  E in p=100  m L=10mm g=1.5mm a=66  m

Experimental setup EO detector (CdTe) P1 0 or 90 ° P2 45° Θ LiNbO 3 emitter E // E⊥E⊥ E in Yb: fiber laser IMRA D1000 (100kHz 11  J 470fs) 50fs Nonlinear optical fiber +negative dispersion fiber 1.0THz Bandpass filter

Achromatic waveplate based on structured parallel metal plates Within 5% deviation from  /2: from 0.67 to 1.21 THz

Achromatic waveplate based on structured parallel metal plates 12/14 θ=45° θ=135°

Achromatic waveplate based on structured parallel metal plates 13/14 θ=45° θ=135°

Achromatic waveplate based on structured parallel metal plates 14/14 Fresnel rhome Shan OE 2004

Light that is reflected from a magnetized surface can change in both polarization and reflected intensity. MO disk Mini Disk Magnet-Optical Kerr Effect (MOKE) complex permittivity tensor : ε

R right ≠R left θ right ≠ θ left + ⇔ + ⇔ + ⇔ Kerr rotation φ Kerr ellipticity η Incident

lens polarizer λ/4 waveplate sample parabolic mirror Input/output module1 Input/output module2 THz Magnet-Optical spectroscopy

Sample: InSb

THz Magnet-Optical spectroscopy InSb

THz Magnet-Optical spectroscopy InSb

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. Summary and future’s prospects

25μm Sandblasting RSm( 粗さ曲線要素の平均長さ ): 30μm Ra( 算術平均粗さ ): 1.4μm