Role of Nanoimprint Lithography for Strongly Miniaturized Optical Spectrometers

Abstract

Optical spectrometers and sensors have gained enormous importance in metrology and information technology, frequently involving the question of size, resolution, sensitivity, spectral range, efficiency, reliability, and cost. Nanomaterials and nanotechnological fabrication technologies have huge potential to enable an optimization between these demands, which in some cases are counteracting each other. This paper focuses on the visible and near infrared spectral range and on five types of optical sensors (optical spectrometers): classical grating-based miniaturized spectrometers, arrayed waveguide grating devices, static Fabry–Pérot (FP) filter arrays on sensor arrays, tunable microelectromechanical systems (MEMS) FP filter arrays, and MEMS tunable photonic crystal filters. The comparison between this selection of concepts concentrates on (i) linewidth and resolution, (ii) required space for a selected spectral range, (iii) efficiency in using available light, and (iv) potential of nanoimprint for cost reduction and yield increase. The main part of this review deals with our own results in the field of static FP filter arrays and MEMS tunable FP filter arrays. In addition, technology for efficiency boosting to get more of the available light is demonstrated.

Miniaturized Interferometric Sensors with Spectral Tunability for Optical Fiber Technology—A Comparison of Size Requirements, Performance, and New Concepts

“…In this review, methodologies of optical sensing in the near-infrared (NIR), visible (VIS), and ultraviolet (UV) spectral wavelengths ranges are introduced. This review also refines one of our recent papers [11], extending it toward integration into optical fiber technology and the improvement of the estimation of minimum size requirements, as well as formulates new insight into tunability efficiency.…”

“…Digital deposition was applied by Wang et al in 2007 [31] to define 128 different FP cavity heights with nine lithography and nine corresponding deposition steps (9 steps for 128 pixels). Digital masking [11] allows (i) digital etching if it is combined with a sequence of etching steps [28,29] and (ii) digital deposition if it is combined with a sequence of deposition steps [31]. The higher the number of different cavity heights (being fabricated) is, the more filter transmission lines (pixels) can be included in an FP filter array.…”

Simple but effective: strong efficiency boost for a linear variable filter-based spectrometer

“…Filter-based spectrometers can have an extremely compact and rigid design without any moving parts, consisting of only a filter array or longitudinally variable filter placed in front of a sensor array, for example, a chargecoupled device (CCD) or complementary metal-oxide-semiconductor, to capture a spectrum in one shot. A variety of spectral filters and structures, often micrometer-sized, have been developed, such as plasmonic color filters, 4,5 photonic crystal arrays, 6 single nanowires, 7 absorptive filter arrays composed of either conventional colloidal quantum dots 8 or perovskite quantum dots, 9 Fabry-Pérot (FP) filter arrays, [10][11][12] and linear (also called "continuously") variable filters [13][14][15][16][17][18][19][20][21][22] [linear variable filters (LVFs)]. An important benefit of such types of spectrometers compared to grating-based spectrometers is the possibility of detecting a broad spectral range with high spectral resolution despite their small size.…”

“…An important benefit of such types of spectrometers compared to grating-based spectrometers is the possibility of detecting a broad spectral range with high spectral resolution despite their small size. 12 They can be implemented using a large number of narrowband filters or an appropriate gradient for the LVF. For example, the reported three FP filter arrays comprise 192 individual filters with a size of 40 × 40 μm and cover a spectral range between 521 and 685 nm.…”

A Study on the Dynamic Forming Mechanism Development of the Negative Poisson’s Ratio Elastomer Molds—Plate to Plate (P2P) Forming Process

“…Moreover, the micro/nano-structural substrates of different sizes and shapes [ 7 , 8 ] prepared by different processing methods (top-down, bottom-up) have high SERS enhancement factors and can be used for medical detection. At present, microstructural components, such as micro-nano gratings [ 9 , 10 , 11 , 12 , 13 , 14 ], polarizers, and lenses, can be completed by technologies such as nano-imprint, exposure, and development [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. However, there is a problem of material selection if etching is used for microstructure fabrication.…”