ECE
ECE
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Dynamo Seminar

Polymer/Liquid Crystal Mixtures for Dynamic Optical Applications

Dr. Timothy Bunning


Chief of the Functional Materials Division of the Materials and Manufacturing Directorate
Air Force Research Laboratory
 
Friday, April 17, 2015
12:00pm - 1:00pm
1123 Lurie BME

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About the Event

The ability to dynamically control light is critical for next generation photonic systems. We will explore several different polymer/liquid crystal constructs for different dynamic applications. These include optical gratings, valuable for many applications especially if their diffractive properties can be controlled electrically and/or optically. Switchable and tunable gratings based on liquid crystals (LCs) are known and widely used due to their large electro-optical and nonlinear optical coefficients. We discuss several systems based on combinations of polymer and liquid crystal materials. We will also discuss a class of LCs known as cholesterics (CLCs) which exhibit a wide spectral bandgap (reflection notch) due to the helicoidal pattern of optic axis orientation caused by the presence of chiral molecules. We explore recent work on the development of CLC materials with large phototuning ranges and/or bandwidth modulation from the blue to near IR upon irradiation with UV or violet wavelengths. We explore property improvements upon incorporation of a polymer network to the bulk LC cell and demonstrate improvements in the backwards tuning response times. We will explore the coupling of plasmonic properties of gold nano-rods with such systems as a means to measure locally temperature variations. WE will end with an exploration of novel photosensitive systems where light can be used to modulate the initial optical property of the system. A common foundation for all these examples is the interaction and understanding of light with polymer/LC soft material systems formed principally through photopolymerization techniques.

Biography

The ability to dynamically control light is critical for next generation photonic systems. We will explore several different polymer/liquid crystal constructs for different dynamic applications. These include optical gratings, valuable for many applications especially if their diffractive properties can be controlled electrically and/or optically. Switchable and tunable gratings based on liquid crystals (LCs) are known and widely used due to their large electro-optical and nonlinear optical coefficients. We discuss several systems based on combinations of polymer and liquid crystal materials. We will also discuss a class of LCs known as cholesterics (CLCs) which exhibit a wide spectral bandgap (reflection notch) due to the helicoidal pattern of optic axis orientation caused by the presence of chiral molecules. We explore recent work on the development of CLC materials with large phototuning ranges and/or bandwidth modulation from the blue to near IR upon irradiation with UV or violet wavelengths. We explore property improvements upon incorporation of a polymer network to the bulk LC cell and demonstrate improvements in the backwards tuning response times. We will explore the coupling of plasmonic properties of gold nano-rods with such systems as a means to measure locally temperature variations. WE will end with an exploration of novel photosensitive systems where light can be used to modulate the initial optical property of the system. A common foundation for all these examples is the interaction and understanding of light with polymer/LC soft material systems formed principally through photopolymerization techniques.

Additional Information

Contact: Gregory Young

Phone: 734-936-2957

Email: gbyoung@umich.edu

Sponsor(s): DYNAMO Center for Dynamic Magneto-Optics

Faculty Sponsor: Stephen Rand

Open to: Public