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Measured transmittance of the tunable air gap FPF (single filter region) at X = 0.00 mm (bottom panel), X = 0.25 mm (middle panel), and X = 0.50 mm (top panel) under Vapp = 0.00 V over the designed wavelength range from 400 to 700 nm. The red dashed curve indicates the simulated transmission spectrum of the air gap FPF for Tair gap = 2.70 µm (bottom panel), Tair gap = 2.72 µm (middle panel), and Tair gap = 2.75 µm (top panel).
Source publication
We fabricate a microelectromechanical systems (MEMS)-based device configuring the tunable air gap Fabry–Pérot filter (FPF) with a static gradient thickness filter on the same platform. The proposed double filter configuration offers a wavelength calibration approach that accurately estimates the air gap dimension in the tunable air gap FPF. The wav...
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... and the device is left undisturbed for several hours to allow the glue dry. During the assembly process, the step pattern area of the top mirror is carefully aligned over the static gradient thickness filter region. Based on this, the length of the static gradient thickness filter is confirmed prior to assembly using transmission measurements (Fig. S4 in the supplementary material). Figure 3(b) shows a photograph of the top view of the device after assembly. Colored interference fringes can be observed in regions where the top mirror overlaps with the bottom mirror to form a cavity. The appearance of several colored fringes provides visual evidence that T air gap is larger than the designed value as only a single ...Context 2
... single and double filter regions of the assembled device are further characterized by performing transmission measurements. Figure 4 presents the measured transmission spectra of the single filter region at different spatial positions (X) under Vapp = 0.00 V over the designed wavelength range of 400-700 nm. Measurements are done using a grating-based microscope spectrometer (LVmicro-Z, Lambda Vision Inc., Japan) with a wavelength resolution of 0.5 nm. ...Context 3
... spatial positions (X) under Vapp = 0.00 V over the designed wavelength range of 400-700 nm. Measurements are done using a grating-based microscope spectrometer (LVmicro-Z, Lambda Vision Inc., Japan) with a wavelength resolution of 0.5 nm. The incident beam diameter is selected as 16 μm. The black curves in the bottom, middle, and top panels of Fig. 4 depict the measured spectra at X = 0.00 mm, X = 0.25 mm, and X = 0.50 mm, respectively. The black curve indicates the presence of six transmission peaks instead of the desired single peak over the entire wavelength range. This implies that the initial T air gap of the tunable air gap FPF is anticipated to be larger than the designed ...Context 4
... range. This implies that the initial T air gap of the tunable air gap FPF is anticipated to be larger than the designed value (T air gap = 135-295 nm). For comparison purposes, the transmission spectrum of the air gap FPF is numerically simulated for different higher values of T air gap. The spectrum with the optimal T air gap is shown in Fig. 4. The red dashed curve in Fig. 4 represents the simulated transmission spectrum of the air gap FPF for T air gap = 2.70 μm (bottom panel), T air gap = 2.72 μm (middle panel), and T air gap = 2.75 μm (top panel). The simulated transmission spectra exhibit a strong agreement with the measured transmission spectra in terms of the spectral ...Context 5
... the initial T air gap of the tunable air gap FPF is anticipated to be larger than the designed value (T air gap = 135-295 nm). For comparison purposes, the transmission spectrum of the air gap FPF is numerically simulated for different higher values of T air gap. The spectrum with the optimal T air gap is shown in Fig. 4. The red dashed curve in Fig. 4 represents the simulated transmission spectrum of the air gap FPF for T air gap = 2.70 μm (bottom panel), T air gap = 2.72 μm (middle panel), and T air gap = 2.75 μm (top panel). The simulated transmission spectra exhibit a strong agreement with the measured transmission spectra in terms of the spectral positions of the peak ...Similar publications
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Citations
... Notably, the t a value in the fabricated tunable air-gap FPF can be experimentally measured using a capacitive displacement sensor [29], [31], [41]. Alternatively, to estimate the t a value while satisfying the requirements for device miniaturization in daily life applications, a compact and lightweight optical sensor using a linear gradient thickness filter can be integrated into the same platform as a tunable air-gap FPF, as previously reported by our group [42], [43]. ...
A tunable air-gap Fabry–Pérot filter consisting of distributed Bragg reflectors as cavity mirrors was developed to operate in the visible wavelength range. The wavelength tunability of the filter was achieved based on the piezo actuation mechanism. Four in-plane identical piezo actuators were employed to simultaneously achieve both wavelength tunability and cavity air-gap parallelism in the filter. Two pairs of piezo actuators positioned at crossed locations enabled independent control of cavity air-gap dimensions along orthogonal directions in the cavity plane. Optical transmission measurements were performed at different spatial positions on the cavity region to estimate the cavity air-gap dimensions. The initial maximum spectral separation among different spatial positions owing to the initial non-parallelism of the cavity air gap was estimated to be ∼28 nm. After achieving cavity air-gap parallelism via piezo actuation, the final maximum spectral separation was reduced to ∼3 nm. The proposed device configuration significantly improved the cavity air-gap parallelism by minimizing the maximum variation of the cavity air-gap dimension from an initial value of 535 nm to a final value of 18 nm, resulting in an improvement by a factor of ∼30. This device prototype can enable high-resolution and high-throughput spectral transmission with improved spatial uniformity across a large cavity area, showing great promise for advancing hyperspectral imaging systems.
