非线性与微纳光学 / 光纤传感与通讯 / 液晶材料与器件 / 其他 

English

陆延青教授应SID(国际信息显示年会)邀请于8月2日作网络讲座
发表日期:2012-07-12

http://www.cdr.ust.hk/Webinar/Lu.html

 

The webinar is timed for optimal exposure to the SID member base:

China , Taiwan , Hong Kong: 11am (Chinese Standard Time, GMT +8:00), August 2nd Thursday;

Japan , Korea : 12pm (GMT +9:00), August 2nd Thursday;

US West Coast: 8pm (PST, GMT -7:00), August 1st Wednesday;

US East Coast: 11pm (GMT -4:00), August 1st Wednesday,

Other locations: please check your local time.

By Prof. Yan-qing Lu

ABSTRACT
Inducing micro-patterns and structures inside a Liquid crystal (LC) cell is an effective way to improve the performance of LC display, for example, widening the view angle. However, in addition to display applications, LC also plays an important role in various tunable photonic devices with the advantages of low cost, no moving parts, low power consumption and high reliability. In this talk, I am going to review some of our work in merging LC and various artificial microstructures in different spans. The related applications are discussed.


When the typical size of a LC microstructure is much larger than the light’s wavelength, it would just work like a multi-pixel LC modulator that is very useful in fiber-optic devices to process multi-channel DWDM signals simultaneously. We design and developed a LC based 40 channel 100GHz spacing wavelength blocker that could regulate the light powers of arbitrary channels.


If the LC microstructure is in the micrometer span, which is comparable with the light’s wavelength, the diffraction effect thus should be taken into account. As the simplest case of LC diffractive element, LC grating has been widely studied. We developed a serial of LC tunable 1D/2D gratings based on the photo alignment technique with both PA/PA and PA/TN configurations. In addition, ferroelectric LC and blue phase LC gratings are also demonstrated.


To realize arbitrary LC alignment microstructures, we further propose and implement a DMD based dynamic micro-lithography system thus could instantly write complicated patterns in the LC cell. Besides normal phase gratings, more complex patterns such as quasicrystal and chequerboard structures are demonstrated. Compared to other techniques, our method enables the arbitrary and instant manipulation of LC alignments and light polarization states, facilitating wide applications in display and photonic fields.


Further decrease the sizes of microstructures being close to or even smaller than the wavelength, more interesting distinctive physical properties may come out. The structures could be pre-fabricated such as a photonic crystal or metamaterial, then LC is used to tune the structures’ properties. The structures also could be induced inside the LC. Polymers are normally the best choice. Polymer network has been successfully adopted to greatly improve the LC’s response time and stabilize the “lattice” of blue phase. When the microstructure becomes smaller and smaller, down to the molecular span. Some intrinsic LC properties is able to be manipulated. In our laboratory, a bent-shaped monomer with allylic end bonds is doped into chiral nematic LC. Blue phase is induced with wider blue phase rang, providing some useful insights into the molecular design of suitable bent-shaped dopants towards wide range blue phase LCs.

In a word, merging LCs and microstructures is an interesting topic that may greatly enhance the LC properties. Microstructures with different sizes all have their own unique features, which could be used in various useful display and photonic devices.

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