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Proceedings Paper

Visible and near-IR range linear variable filter with two-dimensional modeling
Author(s): Cheng-Hao (Kevin) Ko; Jih-Run Tsai; Bang-Ji Wang; Shin-Fa Lin; Chi-Tsung Hong; Wei-Huai Chiu

Paper Abstract

We have proposed an analytical 2D model [1] of a thickness gradient function for thin film deposition of a LVF for order sorting of a diffraction grating using an evaporation chamber. The LVF was fabricated and its thickness profile was measured using a probe-type surface analyzer. This study proposes an innovative method for overcoming the low production rates currently associated with LVF fabrication.

Within the 25% - 75% thickness range, the profile distribution exhibits a high degree of linearity, with R2 are greater than or equal to 0.9914 for both the cases. The LVF zone width appears to be a linear function of the mask height h, with R2 are greater than or equal to 0.9982 for all the cases. This indicates that the thickness gradient function is a more accurate model for obtaining the thickness profile of an LVF than any other modeling mentioned in previous published results. This study demonstrates that the developed theoretical 2D model can be used to predict accurately the thin film profile of an LVF.

The effective zone width of the LVF is defined as a thickness range of 25% - 75%, which appears to have high degree of linearity as a function of the mask height, h (mask-to-substrate gap). Thus, these results also confirms that the linear variable area increases as the mask-to-substrate gap increases. Thin film layer structures are constructed to demonstrate the efficacy of the proposed LVF design concept. Transmission spectrum result (wavebands 400nm to 1000nm) for varying mask heights at different positions shows maximum number of wavebands with transmittance (>99.9%). Comparison of both the theoretical and the evaporating results matches satisfactorily.

Paper Details

Date Published: 17 September 2018
Proc. SPIE 10746, Novel Optical Systems Design and Optimization XXI, 1074607 (17 September 2018); doi: 10.1117/12.2322049
Show Author Affiliations
Cheng-Hao (Kevin) Ko, National Taiwan Univ. of Science and Technology (Taiwan)
Jih-Run Tsai, National Space Organization (Taiwan)
Bang-Ji Wang, National Space Organization (Taiwan)
Shin-Fa Lin, National Space Organization (Taiwan)
Chi-Tsung Hong, National Taiwan Univ. of Science and Technology (Taiwan)
Wei-Huai Chiu, National Taiwan Univ. of Science and Technology (Taiwan)

Published in SPIE Proceedings Vol. 10746:
Novel Optical Systems Design and Optimization XXI
Cornelius F. Hahlweg; Joseph R. Mulley, Editor(s)

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