| Abstract [eng] |
The dissertation objective was to investigate and improve terahertz (THz) imaging techniques allowing for inspection of hidden objects without harmful X-rays. The work was carried out as follows. Firstly, an efficient and cost-effective compact homodyne THz imaging scheme was developed using reliable bow-tie diodes as an alternative to heterodyne THz imaging technique for low absorbing object identification using paper sheets for phase shifting at 0.3 THz and 0.6 THz frequencies. Secondly, effect of molecular beam epitaxy growth conditions on InGaAs/InP layers dedicated for bow-tie diodes fabrication was investigated and optimal growth regime with respect to InGaAs diodes parameters was determined. Furthermore, silicon diffractive optics-based Fibonacci bifocal THz lens was designed, fabricated and investigated. Additionally, the designed bifocal THz lens was applied for THz imaging, demonstrating simultaneous multi-focal THz imaging. Moreover, diffractive THz lens allowing Bessel THz imaging was developed with extended focal depth up to 20 mm suitable for imaging of objects hidden in post packages. Additionally, purely silicon optics based Bessel THz imaging was demonstrated and deconvolution algorithms were applied for enhancement of the contrast. Finally, THz beam manipulation using spatial filtering methods was investigated and applied for THz imaging revealing its advantages in comparison with other beam engineering methods. |
