Huiwen Tai

A widely tunable refractive index in a nanolayered photonic material

A class of composite polymer films is described in which the refractive index can be varied by simple mechanical forces. The films are comprised of 1024 alternating layers of an elastomer and a glassy polymer. When the layer spacing is much less than the wavelength of the probe light, these materials behave as effective medium composites. The layer thickness of the elastomer component and thus the effective index of the composite can be varied by compressing the composite.

Gradient index polymer optics

We developed novel lenses from gradient index, multi-polymer sheets. The sheets were processed into lenses with spherically-symmetric index profiles. An F/2.25 GRIN singlet produced images with 4times better contrast than a commercial F/2.25 glass singlet.

Bio-inspired optical polymers

Nanolayered polymer films were used to construct materials whose properties mimic bio-optic systems found in nature. The nanolayered structures have the unique ability to control the index gradient profile in three dimensions.

Nonlinear transmission of 1D photonic crystal polymers

Transmission from a strongly nonlinear material incorporated into monolithic and nanolayered polymer thin films are compared. When the laser wavelength approaches the bandgap, the nanolayered films transmit less than monoliths as excitation fluence is increased.

Variable refractive index polymeric nanolayered films

A new class of polymer films comprised of alternating elastomeric and glassy polymer nanolayers is described. Applying pressure to the composite can reversibly vary the refractive index. The mechanism for the index change was investigated by reflectance measurements, which were also used to assess the modulus of the elastomeric nanolayer.