In this study, we demonstrated an electrically tunable lens coupler for both variable optical attenuation (VOA) and polarization selection. This coupler consists of a liquid crystal (LC) lens sandwiched between two GRIN lens. A GRIN lens is used to couple the light into the single mode fiber, and a LC lens is used to electrically manipulate the beam size of light. It is known that the lens power of a LC lens is tunable with high polarization sensitivity. Then, as the applied voltage on the LC lens is zero, the incident light is focused due to GRIN lens and coupled into the fiber. On the other hand, the beam size of the transformed e-ray becomes larger because the lens power of a LC lens for the e-ray decreases with the increase of the applied voltage. This results in the decrease of the coupling efficiency, and the optical power coupled into the fiber is smaller. This lens coupler for the e-ray functions as a VOA due to a continuous optical attenuation. On the contrary, the lens power of this LC lens for the o-ray does not vary because of optical anisotropy of the LC layer, and then the coupling efficiency for the o-ray remains high. For an arbitrary polarized incidence, this tunable lens coupler acts as a broadband polarizer for the fiber systems. The polarization dependent loss is larger than 30 dB and the switching time is around 1 second.
We propose a broadband nano-plasmonic reflector by using an asymmetric nano-ring resonator directly connected to the
input and output waveguides based on metal-insulator-metal waveguides. Due to direct connection, both clockwise and
counterclockwise traveling modes propagate inside the ring resonator, giving rise to resonator resonances and Mach
Zehnder interference. Ultra-broad bandwidth is realized by adjusting the lengths of the ring to manipulate the resonant
wavelengths and varying its widths to minimize the low-transmission ripples. An example of the plasmonic reflector
with the dimensions of 200×522 nm×nm and the bandwidth of 1000 nm is numerically accomplished.
Novel multimode-interference (MMI)-based crossings integrated with miniaturized tapers are numerically presented for
Silicon wire waveguides. These miniature tapers function as field expanders to reduce transition loss between the
input/output waveguide and the MMI region and the crosstalk in the crossing section. As a consequence, the lengths of
MMI sections reduce to less than twice of the beat length. Using finite different time domain method, we demonstrate
that the MMI-based waveguide crossing embedded in the quadratic tapers has the size of 5800x5800 nm<sup>2</sup>, the insertion
loss of 0.15 dB and the crosstalk of -42 dB at the wavelength of 1550 nm and broad transmission spectrum ranging from
1500 nm to 1600 nm.
Commercially available colloidal semiconductor quantum dots are employed to produce an electron beam sensitive PMMA-quantum-dot (QD) positive composite via pre-polymerization. In PMMA-QD composite, the QDs are stabilized in rapidly formed oligomer matrices to prevent cluster, and the complete polymerization of the PMMA-QD composite is achieved by commonly used polymerization. The properties of the composites are measured and compared with the QDs in original colloidal solution. Patterning of the composites by direct write electron beam and UV optical lithography shows its promising applications in optoelectronics.