Hung-Chun Lin

Polarizer-free and fast response microlens arrays using polymer-stabilized blue phase liquid crystals

We demonstrate polarizer-free and fast response microlens arrays based on optical phase modulation of polymer-stabilized blue phase liquid crystal (PSBP-LC). Polarization-independent optical phase shift is because the propagation of an incident light is along the optic axis of PSBP-LC, and birefringence of PSBP-LC induced by Kerr effect results in electrically tunable optical phase shift. The measured optical phase shift of a PSBP-LC phase modulation is around π radian at 150 Vrms for the cell gap of 7 μ. The response time is about 3 ms. The focal length is around 13.1 cm at 100 Vrms.

Isoelectronic In-doping effect in GaN films grown by metalorganic chemical vapor deposition

The isoelectronic In-doping effect in GaN films grown by metalorganic chemical vapor deposition was investigated by using Raman scattering, scanning electron microscopy (SEM), and x-ray and photoluminescence (PL) measurements. In our study, the phonon spectra of films remain sharp without alloy formation after incorporation of small amounts of In atoms. The SEM pictures of the sample surface reveal greatly reduced nanopits indicating better surface flatness that is also supported by the multiple interference effect in the PL signals. More importantly, isoelectronic doping has caused the linewidth at 15 K of the near-band-edge emission of GaN to decrease sharply to 10 meV or less, reflecting improved optical property.

A Review of Electrically Tunable Focusing Liquid Crystal Lenses

Electrically tunable focusing liquid crystal (LC) lenses are reviewed in this paper. The distribution of the orientations of LC directors which is controlled by electric fields results in a distribution of refractive indices of LC directors. The incident light can be modulated by the electrically tunable lens-like phase difference of the LC lens. We introduce the basic operating principles of LC lenses and discuss the structures of LC lenses. The major challenges of LC lenses are also discussed. We believe this paper provides a guideline for basic understanding of LC lenses.

An electrically tunable optical zoom system using two composite liquid crystal lenses with a large zoom ratio

An electrically tunable-focusing optical zoom system using two composite LC lenses with a large zoom ratio is demonstrated. The optical principle is investigated. To enhance the electrically tunable focusing range of the negative lens power of the LC lens for a large zoom ratio, we adopted two composite LC lenses. Each composite LC lens consists of a sub-LC lens and a planar polymeric lens. The zoom ratio of the optical zooming system reaches ~7.9:1 and the object can be zoomed in or zoomed out continuously at the objective distance of infinity to 10 cm. The potential applications are cell phones, cameras, telescope and pico projectors.

A fast response and large electrically tunable-focusing imaging system based on switching of two modes of a liquid crystal lens

We demonstrated a fast response and large tunable focusing imaging system consisting of a lens module and a liquid crystal (LC) lens based on the switching of two modes of a LC lens: the negative LC lens and positive LC lens. By discarding the conventional operation of a positive LC lens only in the imaging system, large tunable focusing range can be achieve from 300 to 10 cm owning to the phase change between the positive and the negative LC lens; meanwhile, the response time is fast (∼433 ms). The potential applications are autofocused cell phones, and cameras.

An electrically tunable-focusing liquid crystal lens with a low voltage and simple electrodes

An electrically tunable focusing LC lens with a low voltage and simple planar electrodes is demonstrated. The inhomogeneous electric field of the LC lens without any hole-patterned-electrode is generated by using an embedded polymeric layer with a gradient distribution of dielectric constants (or relative permittivity). LC directors in the LC layer experience spatially inhomogeneous voltages even though a single voltage is applied to the planar electrodes. Such a LC lens has a low voltage (~2.6 V(rms)) and simple design of electrodes. The gradient distribution of dielectric constants of polymeric layer is discussed and the performance of the LC lens is investigated. The applications of such a LC lens are cell phones, webcam, and pico projectors.

An Electrically Tunable Focusing Pico-Projector Adopting a Liquid Crystal Lens

An electrically tunable pico-projector adopting a liquid crystal (LC) lens as an active optical element is demonstrated. The focal length of this pico-projector is electrically tunable from 350 to 14 cm and the tunable range is even wider than that of a manually focused pico-projector. The response times of turn-on and turn-off are approximately 313 and 880 ms, respectively. In addition, the location of the projection lens can affect the electrically tunable range of the system. A small shift of the projection lens results in the large tunable focusing range of the pico-projector and a tunable focusing range is determined by the LC lens. The optical analysis is also discussed. This concept can even be applied to design other electrically auto focusing pico-projectors based on other optical elements such as liquid lenses and spatial light modulators.

An electrically tunable focusing liquid crystal lens with a built-in planar polymeric lens

An electrically tunable focusing liquid crystal (LC) lens with a built-in planar polymeric lens with a short focal length (∼4.41 to 8.82 cm) is demonstrated. The focal length of the LC lens is contributed by two parts: one is the LC layer and the other is planar polymeric layer. In the image system, the object can be continuously imaged by the LC lens when the object is at the objective distance from 360 to 17 cm as the voltage is switched from 0 to 35 Vrms. The image performance is also demonstrated. The applications are cell phones, and cameras

A holographic projection system with an electrically tuning and continuously adjustable optical zoom

A holographic projection system with optical zoom is demonstrated. By using a combination of a LC lens and an encoded Fresnel lens on the LCoS panel, we can control zoom in a holographic projector. The magnification can be electrically adjusted by tuning the focal length of the combination of the two lenses. The zoom ratio of the holographic projection system can reach 3.7:1 with continuous zoom function. The optical zoom function can decrease the complexity of the holographic projection system.

Electrically tunable wettability of liquid crystal/polymer composite films

An electrically tunable wettability in a liquid crystal/ polymer composite film is demonstrated, in which liquid crystal molecules are anchored among polymer grains. The tunable wettability of the composite films originates from the reorientation of the anchored liquid-crystal molecules, which is switched by an in-plane electric field with squared pulses of voltages. These liquid crystal/polymer composite films with electrically tunable wettability have potential applications in polarizer-free displays, ink-jet printing, microfluidic devices, and lab-on-a-chip.