Tunable Subwavelength Metal Gratings in the Mid-IR Band

We demonstrate a tunable infrared (IR) filter based on a patterned subwavelength grating in a metal film. The optical properties of the filter, including center wavelength and pass bandwidth, are dependent on the lithographically defined pattern of the grating. Additionally, the transmission intensity is controlled by using electrostatic actuation to bring the metal film into and out of contact with an underlying dielectric film. A maximum transmission of 72% is achieved, with a 4-to-1 rejection ratio at an actuation voltage of 46 V. The device holds promise for application to gas sensors and other IR sensor systems. The operating principle of this device can be extended to other regions of the electromagnetic spectrum beyond the mid-IR