In this paper, we design and implementation anti-reflection and high reflection film for tunable LC-FP filter working in
typical medium wave infrared (MWIR) spectral region. As to reflection mirror, we complete it by depositing gold film
on the silicon substrate. By using the analytical method of dividing amplitude multiple beam interference to simulate
the reflectance, the reflectivity result of the gold film is around 98% at the average in the MWIR spectral region. When
take the absorption of the gold film into consideration, the gold film should be thin under the condition that it is
conductive well. The anti-reflection film is introduced to reduce the reflection of the other side of the wafer. In
anti-reflection structure, we simulate the reflection of the films with the algorithm of the equivalent membrane and
fulfill our design with the technology of vapor deposition. Finally, we test the total transmittance of the wafer deposited
gold films and anti-reflection films, which is about 0.2% of single chip. By making use of the wafer designed by us, we
fabricate the LC-FP filter by placing two wafers side by side with the anti-reflection structure face to the direction of
wavelength incident. Simultaneously, the LC layer with fixed thickness is sealed between the two high reflection
mirrors formed by gold film. Compared with other method to fabricate mid-infrared FP filter, deposition of reflection
and anti-reflection films on wafer have the advantage of low cost, simple technology.
This paper proposes a method to characterize a liquid crystal Fabry-Perot (LC-FP) hyperspectral imaging devices with electrically controlling and shifting wavelength of light beam penetrating the LC-FP device proposed. As the effect of the directing vector distribution of LC materials can be remarkably changed and stably anchored in an electric field applied over the electrodes of the device, the refractive index of the LC materials which filled into FP cavity can be modulated by voltage signal with relatively low amplitude. We achieved the transmissivity properties of the infrared radiation out from the LC-FP and continuously incident upon the photosensitive structure through the thin film matrix equation, and then acquired the basic relationship among the transmissivity, and the applied voltage signal, and the wavelength parameter selected. The key features of the proposal approach is that the device is mainly composed of very thin electrically modulating refractive-index architecture, which are generally two basic FP interferometers connected closely so as to accurately perform the choice of the wavelength desired in the spectral range by the interference filtering; and the depths of the two FP interferometers are designed to be different, and through combination two parts mentioned above we can obtain some single wavelengths desired of penetrating beam. The proposed device has already been complished. The final device will be used to sequentially choose each desired infrared (IR) wavelength from incident IR radiation. Prototypes of the LC-FP with 4×4 arrays is going to be made, thus we can get several different wavelengths with the device.
This paper proposes a method to characterize a tunable liquid crystal Fabry-Perot (LC-FP) hyperspectral imaging detectors with electrically controlling and shifting wavelength of light beam penetrating the LC-FP chip proposed. Based on the effect of the directing vector distribution of LC materials can be remarkably changed and stably anchored in an electric field applied over the electrodes of the device, the refractive index of the LC materials filled into FP cavity can be modulated by voltage signal with relatively low amplitude. By the thin film matrix equation utilized, we calculated the transmissivity properties of the infrared radiation out from the LC-FP and continuously incident upon the photosensitive structure, and then acquired the basic relationship among the transmissivity, and the applied voltage signal, and the wavelength parameter selected. The key features of the proposal approach is as follows: (1) the device is mainly composed of very thin electrically modulating refractive-index architecture, which are generally two basic FP interferometers connected closely so as to accurately perform the choice of the wavelength desired in the spectral range by the interference filtering; and (2) the depths of the two FP interferometers are designed to be different, and through combination two parts mention ed above we can obtain some single wavelength desired of penetrating beam. The proposed device is being produced currently. The final device will be used to sequentially choose each desired infrared (IR) wavelength from incident IR radiation.
A wavelength tunable optical filter based on cascaded Liquid-Crystal Fabry-Perot (LC-FP) cavity with many working units has been proposed and simulated in this paper. By choosing different material and according geometric parameters, we simulated the structure in the wavelength of medium infrared (IR)(3-5μm) and far IR(8-14μm) with the algorithm of thin film matrix equation and iterative finite-difference. Finally, we give the spectrum of the structure under different driving-voltage. Combing this structure with uncooled infrared focal plane array (IRFPA), the image of many spectral bands can be obtained in one picture frame by applying different driving-voltage on each unit. Compared with other design, this structure has the advantages of wide free spectral range (FSR), compact integration, low cost and high stability.
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