Multi-band filter design with less total film thickness for short-wave infrared

Yung Jhe Yan, I. Pen Chien, Po Han Chen, Sheng Hui Chen, Yi Chun Tsai, Mang Ou-Yang

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


A multi-band pass filter array was proposed and designed for short wave infrared applications. The central wavelength of the multi-band pass filters are located about 905 nm, 950 nm, 1055 nm and 1550 nm. In the simulation of an optical interference band pass filter, high spectrum performance (high transmittance ratio between the pass band and stop band) relies on (1) the index gap between the selected high/low-index film materials, with a larger gap correlated to higher performance, and (2) sufficient repeated periods of high/low-index thin-film layers. When determining high and low refractive index materials, spectrum performance was improved by increasing repeated periods. Consequently, the total film thickness increases rapidly. In some cases, a thick total film thickness is difficult to process in practice, especially when incorporating photolithography liftoff. Actually the maximal thickness of the photoresist being able to liftoff will bound the total film thickness of the band pass filter. For the application of the short wave infrared with the wavelength range from 900nm to 1700nm, silicone was chosen as a high refractive index material. Different from other dielectric materials used in the visible range, silicone has a higher absorptance in the visible range opposite to higher transmission in the short wave infrared. In other words, designing band pass filters based on silicone as a high refractive index material film could not obtain a better spectrum performance than conventional high index materials like TiO2 or Ta2O5, but also its material cost would reduce about half compared to the total film thickness with the conventional material TiO2. Through the simulation and several experimental trials, the total film thickness below 4 um was practicable and reasonable. The fabrication of the filters was employed a dual electric gun deposition system with ion assisted deposition after the lithography process. Repeating four times of lithography and deposition process and black matrix coating, the optical device processes were completed.

Original languageEnglish
Title of host publicationCurrent Developments in Lens Design and Optical Engineering XVIII
EditorsVirendra N. Mahajan, Simon Thibault, R. Barry Johnson
ISBN (Electronic)9781510612075
StatePublished - 2017
EventCurrent Developments in Lens Design and Optical Engineering XVIII 2017 - San Diego, United States
Duration: 7 Aug 20178 Aug 2017

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceCurrent Developments in Lens Design and Optical Engineering XVIII 2017
Country/TerritoryUnited States
CitySan Diego


  • Bandpass filter
  • Optical interference filter
  • Photolithography
  • Short-wave infrared


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