Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011, USA.
Nanotechnology. 2016 Jul 22;27(29):295301. doi: 10.1088/0957-4484/27/29/295301. Epub 2016 Jun 8.
This paper presents the fabrication methodology of a linear variable photonic crystal (PC) filter with narrowband reflection that varies over a broad spectral range along the length of the filter. The key component of the linear variable PC filter is a polymer surface-relief grating whose period changes linearly as a function of its position on the filter. The grating is fabricated using a nanoreplica molding process with a wedge-shaped elastomer mold. The top surface of the mold carries the grating pattern and the wedge is formed by a shallow angle between the top and bottom surfaces of the mold. During the replica molding process, a uniaxial force is applied to stretch the mold, resulting in a nearly linearly varying grating period. The period of the grating is determined using the magnitude of the force and the local thickness of the mold. The grating period of the fabricated device spans a range of 421.8-463.3 nm over a distance of 20 mm. A high refractive index dielectric film is deposited on the graded-period grating to act as the waveguide layer of the PC device. The resonance reflection feature of the device varies linearly in a range of 680.2-737.0 nm over the length of the grating.
本文提出了一种具有宽带反射窄带的线性变光子晶体（PC）滤波器的制造方法，该滤波器在滤波器的长度上沿着光谱范围发生变化。线性可变 PC 滤波器的关键部件是聚合物表面浮雕光栅，其周期随其在滤波器上的位置呈线性变化。该光栅采用带有楔形弹性体模具的纳米复制成型工艺制造。模具的顶表面带有光栅图案，而楔形是由模具的顶表面和底表面之间的浅角度形成的。在复制成型过程中，施加单轴力以拉伸模具，从而导致光栅周期几乎呈线性变化。通过力的大小和模具的局部厚度来确定光栅的周期。在 20mm 的距离内，所制造器件的光栅周期在 421.8-463.3nm 的范围内变化。在渐变周期光栅上沉积了高折射率介电膜，作为 PC 器件的波导层。器件的共振反射特征在光栅长度上在 680.2-737.0nm 的范围内呈线性变化。
