We report generation of broadband supercontinuum (SC) by noise-like pulses (NLPs) with a central wavelength of 1070 nm propagating through a long piece of standard single-mode fibers (~100 meters) in normal dispersion region far from the zero-dispersion point. Theoretical simulations indicate that the physical mechanism of SC generation is due to nonlinear effects in fibers. The cascaded Raman scattering is responsible for significant spectral broadening in the longer wavelength regions whereas the Kerr effect results in smoothing of SC generated spectrum. The SC exhibits low threshold (43 nJ) and a flat spectrum over 1050-1250 nm.

Phase shift exceeding $\pi ∕2$ at $1\mathrm{THz}$ is demonstrated by using electrically controlled birefringence in a homeotropically aligned nematic liquid crystal (E7) cell, $570\mu \mathrm{m}$ in thickness. The driving voltage required for a phase shift of 90° is $125\mathrm{V}$ (rms). We demonstrate that the phase shifter works as an electrically switchable quarter-wave plate at $1\mathrm{THz}$. The device can also be used as an electrically tuned phase compensator around the quarter-wave point near $1\mathrm{THz}$.

A low-loss terahertz air-core microstructure fiber is demonstrated for terahertz waveguiding. Substantially low attenuation constant less than $0.01{\mathrm{cm}}^{-1}$ has been achieved and the guiding wavelength is found to be tunable by linear scaling the fiber size. The experimental results well agree with the simulation based on the finite-difference frequency-domain method, which interprets the guiding mechanism as the antiresonant reflecting waveguiding. The simulated modal pattern shows that most terahertz field is concentrated inside the central hollow air core and is guided without outside interference, which has high potential for guiding intense terahertz waves with minimized loss.

A two-element tunable Lyot filter operating in the terahertz (THz) frequency range is demonstrated. The central bandpass frequency of the filter can be continuously tuned from $0.388\text{to}0.564\mathrm{THz}$ (a fractional tuning range of 40%) using magnetically controlled birefringence in nematic liquid crystals. The transmission bandwidth is $0.1\mathrm{THz}$ and the insertion loss of the present device is $8\mathrm{dB}$ due to the scattering of LC molecules in the thick LC cells. This filter can be operated at room temperature.

Tunable phase shift up to 360° at 1 THz is achieved with a liquid crystal (LC) device. The key to this design is (1) the use of a nematic LC, E7, which exhibits a birefringence of ~0.17 (0.2–1.2 THz); (2) a LC cell (3-mm in thickness) with sandwiched structure to increase the interaction length while minimizing interface Fresnel losses; and (3) the use of magnetic field to align the thick LC cell and achieve continuous tuning of phase from 0 to 360°. This device can be operated over a broad range near room temperature.