Design of a novel TiO2/airgap-based polarizing micro beam splitter cube

M J Maciel,S Pimenta,J H Correia,J F Ribeiro

doi:10.1088/1742-6596/1319/1/012006

M J Maciel, S Pimenta + Show 2 more

Open Access

https://doi.org/10.1088/1742-6596/1319/1/012006

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Abstract

Polarizing beam splitters are key elements widely used in different optical instruments. This paper introduces the design and simulation of a novel thin-film multilayer polarizing micro beam splitter based on airgap layers (n = 1.002828 at 400 nm). The negligible absorption coefficient of the air over a wide spectral region (κ ≈ 0 from about 200 nm and higher) satisfies the conditions of a perfect low refractive index material (L). Moreover, using titanium dioxide (TiO2) as high refractive index material (H), a very high refractive index contrast is obtained. The micro beam splitter optical structure consists in a 7 optimized multilayer of TiO2 and air, providing a refractive contrast higher than 1.2. The polarizing beam splitter cube is projected in a borosilicate glass substrate (BK7) and the optical multilayer obtained, expressed in multiples of the quarter wavelength optical thickness – QWOT, is 1.6H L 1.1H 1.5L 1.1H L 1.6H. This optical structure ensures the transmission of p- polarization and the reflection of s- polarization, from visible to NIR spectral range, over a bandwidth higher than 170 nm. Additionally, the designed polarizing beam splitter can be fabricated using standard microtechnology fabrication processes.

Highlights

Polarizing beam splitters (PBS) are optical components which separate the two orthogonal polarization modes of the light, s- and p- polarizations, into different propagation directions
They play an important rule in liquid crystal displays (LCD), optical communication systems [1] and polarization-based imaging systems, such as a polarization sensitive optical coherence tomography (OCT) systems [6]
The PBS was designed for a cube typed configuration, using borosilicate glass (BK7) as substrate

Summary

Introduction

Polarizing beam splitters (PBS) are optical components which separate the two orthogonal polarization modes of the light, s- and p- polarizations, into different propagation directions. Multilayer PBS are key polarizing separators, which are based on optical interference thin-films [2]. This type of beam splitters presents very good efficiency (negligible absorption) [8]. The most convenient PBS reflects one polarization component of light at 90o relatively to the incident light direction, which puts the cube type configuration to advantage [9]. Wavelength band, reflectance or transmittance of the desired polarization and angular field are the main characteristics of a PBS [2] These parameters are investigated performing TFCalc (from Software Spectra) simulations from visible to NIR spectral regions. Borosilicate glass substrate (BK7) is the material used as substrate, and it is intended the separation of the two polarization states

Optical theory

Characterization parameters

Findings

Conclusions and future guidelines