Fabrication of micro-optical devices at the end of a multimode optical fiber with negative tone lift-off EBL

Sundaram, Vijay M.; Wen, Sy-Bor

doi:10.1088/0960-1317/22/12/125016

Cited by 11 publications

(4 citation statements)

References 26 publications

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“…As a proof of concept, we demonstrated patterning of gold nanodot arrays on a fibre facet. Functionalization on optical fibres has recently attracted much attention because fibre-based devices can be small, lightweight and portable for in-situ sensing, imaging, and optical trapping applications 52 53 54 . However, the size and the shape of an optical fibre preclude the use of conventional lithographic processes 25 .…”

Section: Resultsmentioning

confidence: 99%

Nanofabrication on unconventional substrates using transferred hard masks

Bayn

et al. 2015

Sci Rep

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A major challenge in nanofabrication is to pattern unconventional substrates that cannot be processed for a variety of reasons, such as incompatibility with spin coating, electron beam lithography, optical lithography, or wet chemical steps. Here, we present a versatile nanofabrication method based on re-usable silicon membrane hard masks, patterned using standard lithography and mature silicon processing technology. These masks, transferred precisely onto targeted regions, can be in the millimetre scale. They allow for fabrication on a wide range of substrates, including rough, soft, and non-conductive materials, enabling feature linewidths down to 10 nm. Plasma etching, lift-off, and ion implantation are realized without the need for scanning electron/ion beam processing, UV exposure, or wet etching on target substrates.T he ability to define patterns on the nanometre scale is a cornerstone of modern nanotechnology with applications in chemistry, biology, medicine, electronics, optics, material science and other fields. In top-down fabrication processing, patterns are produced in a resist film by commonly-used lithography methods 1 , including electron-beam lithography (EBL) 2 , optical lithography 3 and projection ion/electron beam lithography with stencil masks 4-7 . The patterns can then be transferred onto the substrate using subtractive or additive methods, such as dry etching or lift-off 8,9 . However, these lithography techniques are restricted to a certain subset of target samples, which must be flat and typically several millimetres or more in size so that a uniform resist film can be applied by spin coating 10 . Spin coating is difficult on many other types of substrates 11 , including fibre facets, thin and fragile samples, or small regions on pre-fabricated devices such as semiconductor lasers 12 and atomic force microscope (AFM) cantilevers 13 . Also, many samples have low electrical conductivity and are therefore not suitable for EBL or require the coating of additional conductive layers.Several techniques have been developed to solve the challenges in patterning some of the above-mentioned samples. Evaporated negative resists for EBL have been demonstrated to pattern optical fibres 12 and AFM cantilevers 13 . Dip coating 14 and spray coating 15 have been developed, but the difficulty of producing uniform and thin resist films present major challenges for high-resolution EBL. A focused ion beam (FIB) can be used for fabricating these samples without spin coating, but it causes extensive surface amorphization, material re-deposition, and gallium implantation [16][17][18] . Nanoimprint lithography 19,20 can also be applied to some of these unconventional substrates without spin coating [21][22][23] , which is ideal for rigid sample surfaces to avoid pattern distortion. A few other methods of pattern transfer have been explored in which metal nanostructures were transferred onto unconventional substrates by utilizing a sacrificial organic layer 24,25 ; they are mainly suited for applications that do...

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Section: Resultsmentioning

confidence: 99%

Nanofabrication on unconventional substrates using transferred hard masks

Bayn

et al. 2015

Sci Rep

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“…For the same reason, 450 nm deep (or even deeper) pillar-shaped initial mold can be used to deal with the issue of non-uniform residual resist without any obvious deformation in the patterned resist; (3) due to the high etching selectivity of Si-doped STU2 to LOR in O 2 -based ICP etching, the non-uniformity issue of the underlying resist can be ignored. Generally, a WLO method is used to fabricate the undercut profile for the preparation of micro-scaled arrays [24,25]. However, when the feature size decreases down to hundreds of nanometers, the use of WLO will induce the following issues: (1) the wet etching speed is too fast to be controlled; (2) the free-standing nano-pillars will collapse due to the influence of the buoyancy, the flow force and the surface tension of the liquid.…”

Section: Resultsmentioning

confidence: 99%

Photonic crystal structures on nonflat surfaces fabricated by dry lift-off soft UV nanoimprint lithography

Sun

Zhang

et al. 2013

J. Micromech. Microeng.

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The surface nonflatness induced from the material itself or the production atmosphere can lead to serious non-uniformity consequences in nanoimprint lithography (NIL) which is used for providing a low cost and high throughput nano-fabrication process. In this paper, soft UV NIL (SUNIL) processes are used for photonic crystal (PC) pattern transfer of a GaN-based light-emitting diode (LED) with patterned sapphire substrate (PSS). The results reveal a significant incompatibility between the conventional SUNIL and the nonflat p-GaN surface. Ellipse-shaped rather than circle-shaped PC structure is obtained on the p-GaN surface due the deformation of the soft mold in nonflat NIL. A dry lift-off (DLO) SUNIL is proposed to overcome the non-uniformity issue in nonflat NIL as well as the collapse problem of the free-standing pillar-shaped resist in wet lift-off. The photoluminescence enhancements of the LED fabricated by the DLO SUNIL method compared to those with conventional SUNIL and unpatterned LED are 1.41 fold and 3.48 fold, respectively. Further study shows that the DLO SUNIL is applicable in the fabrication of the PC structure with tunable duty cycle via one single initial PC mold.

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“…To improve the sensitivity of sensors, it is often necessary to modify or fabricate special structures on optical fibers to enhance the interaction between light and matter. In recent years, manufacturing strategies such as electron beam lithography (EBL) [ 27 ], focused ion beam milling (FIB) [ 28 , 29 ], direct laser writing (DLW) [ 30 ], nano-imprinting, and laser micro-machining have been successfully applied in the fabrication of fiber optic sensors. Among them, EBL, DLW, nano-imprinting, and other techniques have limited applicability, since they typically rely on flat surfaces for manufacturing [ 28 ].…”

Section: Introductionmentioning

confidence: 99%

Demonstration of a Learning-Empowered Fiber Specklegram Sensor Based on Focused Ion Beam Milling for Refractive Index Sensing

Gao

2023

Nanomaterials

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We report a simple and robust fiber specklegram refractive index sensor with a multimode fiber-single mode fiber-multimode fiber structure based on focused ion beam milling. In this work, a series of fluid channels are etched on the single-mode fiber by using focused ion beam milling to enhance the interaction between light and matter, and a deep learning model is employed to demodulate the sensing signal according to the speckle patterns collected from the output end of the multimode fiber. The feasibility and effectiveness of the proposed scheme were verified by rigorous experiments, and the test results showed that the demodulation accuracy and speed could reach 99.68% and 4.5 ms per frame, respectively, for the refractive index range of 1.3326 to 1.3679. The proposed sensing scheme has the advantages of low cost, easy implementation, and a simple measurement system, and it is expected to find applications in various chemical and biological sensing.

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Fabrication of micro-optical devices at the end of a multimode optical fiber with negative tone lift-off EBL

Cited by 11 publications

References 26 publications

Nanofabrication on unconventional substrates using transferred hard masks

Nanofabrication on unconventional substrates using transferred hard masks

Photonic crystal structures on nonflat surfaces fabricated by dry lift-off soft UV nanoimprint lithography

Demonstration of a Learning-Empowered Fiber Specklegram Sensor Based on Focused Ion Beam Milling for Refractive Index Sensing

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