Fabrication of Ultrathin Large-area Dielectric Membrane Stacks for use as Interference Filters

Ghaderi, M.; Graaf, G. de; Wolffenbuttel, R.F.

doi:10.1016/j.proeng.2016.11.369

Cited by 3 publications

(2 citation statements)

References 7 publications

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“…For optimal performance, a high level of parallelism between the DBRs is required, typically better than λ∕10 or λ∕20 for MEMS-based optical applications. [43][44][45][46] Our efforts in this work culminate in fabricating layers with mirror parallelism exceeding a level of λ∕200 for the suspended mirror layers. This work provides reliable and reproducible methods to develop high performing surface micromachined DBRs for the MWIR and LWIR wavelength regions using thermally evaporated BaF 2 as a low refractive index material and their suitability in the development of MEMS-based optical FPIs.…”

Section: Introductionmentioning

confidence: 99%

Ge/BaF2 thin-films for surface micromachined mid-wave and long-wave infrared reflectors

Gill

Tripathi

Keating

et al. 2022

J. Optical Microsystems

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High performance distributed Bragg reflectors (DBRs) are key elements to achieving high finesse MEMS-based Fabry-Pérot interferometers (FPIs). Suitable mechanical parameters combined with high contrast between the refractive indices of the constituent optical materials are the main requirements. In this paper, Germanium (Ge) and barium fluoride (BaF 2 ) optical thin-films have been investigated for mid-wave infrared (MWIR) and long-wave infrared (LWIR) filter applications. Thin-film deposition and fabrication processes were optimised to achieve mechanical and optical properties that provide flat suspended structures with uniform thickness and maximum reflectivity. Ge-BaF 2 -Ge 3-layer solid-material DBRs have been fabricated that matched the predicted simulation performance, although a degradation in performance was observed for wavelengths beyond 10 μm that is associated with optical absorption in the BaF 2 material. Ge-Air-Ge 3-layer air-gap DBRs, in which air rather than BaF 2 served as the low refractive index layer, were realized to exhibit layer flatness at the level of 10 to 20 nm across lateral DBR dimensions of several hundred micrometers. Measured DBR reflectance was found to be ≳90% over the entire wavelength range of the MWIR band and for the LWIR band up to a wavelength of 11 μm. Simulations based on the measured DBR reflectance indicates that MEMS-based FPIs are able to achieve a peak transmission of ≳90% over the entire MWIR band and up to 10 μm in the LWIR band, with a corresponding spectral passband of ≲50 nm in the MWIR and <80 nm in the LWIR.

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Section: Introductionmentioning

confidence: 99%

Ge/BaF2 thin-films for surface micromachined mid-wave and long-wave infrared reflectors

Gill

Tripathi

Keating

et al. 2022

J. Optical Microsystems

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“…Suspended SiO 2 structures are important for a number of optical and photonic integrated circuit (PIC) applications such as broad spectra frequency combs [ 1 ], low propagation loss waveguides [ 2 ], and UV–visible optical filters [ 3 ]. In addition to these applications, suspended waveguides can be applied to UV absorption spectroscopy and an emerging class of gallium nitride (GaN) nanowire-based photonic devices that could benefit from UV transparent waveguides—including near-field scanning optical microscopy (NSOM), vertical cavity lasers, and direct write lithography [ 4 , 5 ].…”

Section: Introductionmentioning

confidence: 99%

Stress and Refractive Index Control of SiO2 Thin Films for Suspended Waveguides

Wostbrock

Busani

2020

Nanomaterials

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Film stress and refractive index play an important role in the fabrication of suspended waveguides. SiO2 waveguides were successfully fabricated on multiple substrates including Si, Ge, and Al2O3 wafers; the waveguides were deposited using inductively coupled plasma chemical vapor deposition at 100 °C. The precursor gases were SiH4 and N2O at 1:3 and 1:9 ratios with variable flow rates. The occurrence of intrinsic stress was validated through the fabrication of suspended SiO2 bridges, where the curvature of the bridge corresponded to measured intrinsic stress, which measured less than 1 µm thick and up to 50 µm in length. The flow rates allow film stress tunability between 50 and −65 MPa, where a negative number indicates a compressive state of the SiO2. We also found that the gas ratios have a slight influence on the refractive index in the UV and visible range but do not affect the stress in the SiO2 bridges. To test if this method can be used to produce multi-layer devices, three layers of SiO2 bridges with air cladding between each bridge were fabricated on a silicon substrate. We concluded that a combination of low temperature deposition (100 °C) and photoresist as the sacrificial layer allows for versatile SiO2 bridge fabrication that is substrate and refractive index independent, providing a framework for future tunable waveguide fabrication.

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Fabrication and characterization of MEMS airgap-based optical filters for the UV spectral range

Ghaderi

Wolffenbuttel

2017

2017 19th International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS)

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Fabrication of Ultrathin Large-area Dielectric Membrane Stacks for use as Interference Filters

Cited by 3 publications

References 7 publications

Ge/BaF2 thin-films for surface micromachined mid-wave and long-wave infrared reflectors

Ge/BaF2 thin-films for surface micromachined mid-wave and long-wave infrared reflectors

Stress and Refractive Index Control of SiO2 Thin Films for Suspended Waveguides

Fabrication and characterization of MEMS airgap-based optical filters for the UV spectral range

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