Graduation date: 2007
In this thesis I studied several THz components that can be used for potential THz
technology. THz waves were generated in nonlinear medium via optical rectification
of femtosecond optical pulses. Utilizing the phase matching condition between the
optical and THz waves in a ZnTe crystal, single-cycle broad-band THz pulses were
obtained. On the other hand, a tunable narrow-band THz waves were generated in
PPLN structures based on a quasi-phased matching process. THz waves were detected
via free-space electro-optic detection.
Several methods of THz pulse shaping were demonstrated. First, the generated THz
waves replicated the polled lithium niobate (PLN) domain structures. In the 2nd
method, we controlled the THz pulse shape by adjusting the delay time between two
coherent optical pulses impinging on a fanned out periodically poled lithium niobate
(FO-PPLN) structure. The 3rd method is an adaptive THz pulse shaping technique in
which each frequency component of the THz wave generated in the FO-PPLN crystal
was manipulated
Controlling the ellipticity of the THz wave is highly desirable for many
applications. Two linearly right-angled and delayed optical pulses incident on a
nonlinear medium generated two coherent THz pulses. The ellipticity of the resultant
THz wave was controlled by adjusting the delay time between the two optical pulses.
The other and more efficient technique is to use the THz wave-plate consisting of a
wire-grid polarizer and a mirror. The output of the waveplate is two linearly and
perpendicularly polarized THz waves with a relative phase shift. The ellipticity of the
output pulse is controlled by adjusting the distance between the wire-grid and the
mirror located behind it.
Linear THz properties of 1D periodic dielectric structure were studied.
Distributed-Brag-reflectors with 5, 10, and 15 periods in both transmission and
reflection arrangements were investigated. Stop-bands at (0.5-0.7) THz and (1.6-1.8)
THz were shown in the transmission arrangement. High-reflectivity-bands at (0.55-
0.89) THz, (1.37-1.53) THz, and (2.03-2.29) THz in a 45° reflection geometry were
observed. A resonant cavity structure was also investigated. A resonant transmission
line with frequency in the center of the stop band was demonstrated.