3D nanoimprinted Fabry–Pérot filter arrays and methodologies for optical characterization

Abstract

Fabry-Pérot (FP) filter arrays fabricated by highresolution three dimensional (3D) NanoImprint technology are presented. A fabrication process to implement 3D templates with very high vertical resolution is developed. Filter arrays with 64 different cavity heights have been fabricated requiring only one single imprint step. Different optical methods are involved in this paper to characterize geometric and spectral properties. In order to investigate the transfer accuracy of the surface quality from the NanoImprint template to the filter, we use white light interferometry (WLI) measurements. Surface roughness and structure height accuracy of <1 nm for both values demonstrate the conservation of these critical parameters during the 3D NanoImprint process. Additionally, an optical characterization methodology for spectral transmission and reflection measurements of the filter arrays is introduced and applied. A compact microscope spectrometer setup which allows efficient handling, high resolution and short inspection time is verified by comparing measurement results to that of an optical bench setup used as a reference. First, this paper focuses on the foundation of the FP filter arrays, second on the technological fabrication, third on validation calibration of the setup and forth on the characterization of the filter arrays. The measurements envisage the spectral position of filter transmission lines, the full width at half maximum (FWHM) and the

Role of Nanoimprint Lithography for Strongly Miniaturized Optical Spectrometers

“…The optical spectra of all FP transmission lines were recorded by a microscope spectrometer setup consisting of halogen lamp, confocal microscope, photodetector, lateral active aperture manipulation, and a commercial spectrometer [ 34 ]. Figure 4 presents the spectra of 192 transmission lines of the fabricated FP filter array with 3 spectrally neighboring DBRs.…”

“…Nanoimprint technology is able to mold the whole cavity structure of millions of pixels, and the mold/template can be replicated and reused several times. Theoretically, there is no limit to the number of pixels that can be fabricated in a single cavity layer imprint step [ 32 , 33 , 34 , 35 , 36 ], in contrast to alternative technologies [ 27 , 28 , 29 , 30 ]. In a batch process many FP filter arrays can be imprinted at the same time, potentially resulting in substantial cost reduction.…”

“…The third interferometric spectrometer is based on the Fabry–Pérot (FP) principle [ 4 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ]. Although only two parallel transparent dielectric mirrors are involved, the FP interferometer is also highly complex and involves multipath interference.…”

“…As a selection of alternatives to these mini grating spectrometers, we compare in this review paper four strongly miniaturized optical spectrometers ( Table 1 ): AWG devices [ 20 , 21 , 22 , 23 , 24 , 25 , 26 ], static FP filter arrays on a charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) sensor arrays [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ], tunable MEMS FP filter arrays [ 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ] on photodetector (PD) arrays, and tunable MEMS photonic crystal (PC) filters [ 61 , 70 , 71 , 72 , 73 , 74 ]. At first glance, we identify that all these alternatives are smaller in size and reveal higher resolutions, as well as smaller FWHM than the grating spectrometers.…”

MWIR/LWIR filter based on Liquid–Crystal Fabry–Perot structure for tunable spectral imaging detection

“…Meanwhile, with the development of Micro-Electro-Mechanical Systems (MEMS) and Micro-Opt-Electro-Mechanical Systems (MOEMS), the electrically tunable filter based on the structure of MEMS-FP has been utilized in spectral imaging application. The wavelength of the resonant peak, determined by the depth of the FP cavity, has already covered several typical regions such as visible [6], near-infrared [7,8], mid-infrared [9], and far-infrared [10]. Although the size of the device has been significantly reduced and the transmission spectrum can be adjusted electrically, the mechanical moving parts of MEMS-FP filter limit its reliability in some applications.…”