We have fabricated high quality THz tunable bandpass filters based on one dimensional photonic crystal cavity. The
filter have a high quality about 1500 and can have a very narrow passband and the full width at half maximum (FWHM)
can be about 200MHz and the peak transmission is higher than -4dB. With the length of cavity adjusted by a motorized
linear stage, the central frequency of the filter can be tuned continuously. The bandwidth and insertion loss is also
The modes in a metallic waveguide loaded with a high permittivity dielectric rod may possess similar dispersion
relations to the modes in the left-handed metamaterial (LHM) waveguide. Therefore, such dielectric-loaded metallic
waveguide may also support slow light propagation. The slow light in such waveguide is numerically studied. The
properties and the existence conditions of slow light modes in such waveguide are also numerically studied. The results
show that the wavelength of slow light varies with the parameters of the waveguide and that high-contrast between the
dielectric rod and the air is necessary of existence of slow light modes. The linearly tapered waveguide are proposed
accordingly to realize the "trapped rainbow" phenomena. The practical tapered lossy waveguide is also investigated. It is
shown that the slow light with low loss can be achieved in a realistic waveguide. Moreover, a novel notch filter based on
such slow light waveguide is proposed.
The colorful artificial 3D silica colloidal crystals (opal) were prepared through self-assembly of silica spheres in the visible frequency range. We directly synthesized nano silver particles in the void of the silica artificial opal film using the photolysis of silver nitrate under UV light, nano silver particles were self-deposited around the surface of silica sphere. The shifts of the stop band of the artificial crystals after exposing different time under UV light were studied. Synthetic silica opal with three-dimensional (3D) structure is potentially useful for the development of diffractive optical devices, micro mechanical systems, and sensory elements because photonic band gaps obtained from self-assembled closely packed periodic structures.