Terahertz imaging with sub-wavelength resolution by femtosecond laser filament in air

Terahertz (THz) imaging provides cutting edge technique in biology, medical sciences and non-destructive evaluation. However, due to the long wavelength of the THz wave, the obtained resolution of THz imaging is normally a few hundred microns and is much lower than that of the traditional optical imaging. We introduce a sub-wavelength resolution THz imaging technique which uses the THz radiation generated by a femtosecond laser filament in air as the probe. This method is based on the fact that the femtosecond laser filament forms a waveguide for the THz wave in air. The diameter of the THz beam, which propagates inside the filament, varies from 20 μm to 50 μm, which is significantly smaller than the wavelength of the THz wave. Using this highly spatially confined THz beam as the probe, THz imaging with resolution as high as 20 μm (~λ/38 at 0.4 THz) can be realized.

[1]  Remote sub-diffraction imaging with femtosecond laser filaments. , 2012, Optics letters.

[2]  Hartmut G Roskos,et al.  Terahertz white-light pulses from an air plasma photo-induced by incommensurate two-color optical fields. , 2010, Optics express.

[3]  R. Kersting,et al.  Terahertz imaging with nanometer resolution , 2003 .

[4]  See Leang Chin,et al.  Broadband terahertz wave remote sensing using coherent manipulation of fluorescence from asymmetrically ionized gases , 2010, CLEO/QELS: 2010 Laser Science to Photonic Applications.

[5]  T. Elsaesser,et al.  Ultrafast spatiotemporal dynamics of terahertz generation by ionizing two-color femtosecond pulses in gases. , 2010, Physical review letters.

[6]  A. Becker,et al.  Experiment and simulations on the energy reservoir effect in femtosecond light filaments. , 2005, Optics letters.

[7]  V. P. Kandidov,et al.  From self-focusing light beams to femtosecond laser pulse filamentation , 2013 .

[8]  George Rodriguez,et al.  Coherent control of terahertz supercontinuum generation in ultrafast laser–gas interactions , 2008 .

[9]  Masayoshi Tonouchi,et al.  Scanning Probe Laser Terahertz Emission Microscopy System , 2006 .

[10]  Hartmut G. Roskos,et al.  Broadband THz emission from gas plasmas induced by femtosecond optical pulses: From fundamentals to applications , 2007 .

[11]  Yi Liu,et al.  Strong enhancement of terahertz radiation from laser filaments in air by a static electric field. , 2008, Physical review letters.

[12]  George Rodriguez,et al.  Scaling behavior of ultrafast two-color terahertz generation in plasma gas targets: energy and pressure dependence. , 2010, Optics express.

[13]  Jean-Claude Kieffer,et al.  Microwave guiding in air by a cylindrical filament array waveguide , 2008 .

[14]  X C Zhang,et al.  Terahertz wave imaging: horizons and hurdles. , 2002, Physics in medicine and biology.

[15]  Jalil Ali,et al.  Exact Reconstruction of THz Sub-λ Source Features in Knife-Edge Measurements , 2013 .

[16]  K. Y. Kim,et al.  Off-axis phase-matched terahertz emission from two-color laser-induced plasma filaments. , 2012, Physical review letters.

[17]  F. Théberge,et al.  Toward remote high energy terahertz generation , 2010 .

[18]  R. Morandotti,et al.  Exact Reconstruction of THz Sub-$\lambda$ Source Features in Knife-Edge Measurements , 2013, IEEE Journal of Selected Topics in Quantum Electronics.

[19]  Roberto Morandotti,et al.  Wavelength scaling of terahertz generation by gas ionization. , 2013, Physical review letters.

[20]  V. Cherepenin,et al.  Plasma channels formed by a set of filaments as a guiding system for microwave radiation , 2010 .

[21]  G. Mu,et al.  Portraying polarization state of terahertz pulse generated by a two-color laser field in air. , 2009, Optics letters.

[22]  Z. Jiang,et al.  Near-field terahertz imaging with a dynamic aperture. , 2000, Optics letters.

[23]  George Rodriguez,et al.  Terahertz emission from ultrafast ionizing air in symmetry-broken laser fields. , 2007, Optics express.

[24]  V. Tikhonchuk,et al.  Conical forward THz emission from femtosecond-laser-beam filamentation in air. , 2007, Physical review letters.

[25]  Xu Xie,et al.  Detection of broadband terahertz waves with a laser-induced plasma in gases. , 2006, Physical review letters.

[26]  X. Zhang,et al.  7 terahertz broadband GaP electro-optic sensor , 1997 .

[27]  N. Karpowicz,et al.  Terahertz emission profile from laser-induced air plasma , 2006 .

[28]  Xu Xie,et al.  Coherent control of THz wave generation in ambient air. , 2006, Physical review letters.

[29]  V. P. Kandidov,et al.  Laser filament induced microwave waveguide in air , 2007, International Conference on Lasers, Applications, and Technologies.

[30]  Masayoshi Tonouchi,et al.  Cutting-edge terahertz technology , 2007 .

[31]  T. Elsaesser,et al.  Generation of single-cycle THz transients with high electric-field amplitudes. , 2005, Optics letters.

[32]  Martin Koch,et al.  THz near-field imaging , 1998 .

[33]  F. Théberge,et al.  Non-radially polarized THz pulse emitted from femtosecond laser filament in air. , 2008, Optics express.

[34]  K. Y. Kim,et al.  Intense terahertz generation in two-color laser filamentation: energy scaling with terawatt laser systems , 2013 .

[35]  Roberto Morandotti,et al.  CCD-based imaging and 3D space-time mapping of terahertz fields via Kerr frequency conversion. , 2013, Optics letters.

[36]  Masashi Yamaguchi,et al.  Coherent heterodyne time-domain spectrometry covering the entire “terahertz gap” , 2008 .

[37]  Hartmut G. Roskos,et al.  Spatio-spectral characteristics of ultra-broadband THz emission from two-colour photoexcited gas plasmas and their impact for nonlinear spectroscopy , 2013 .