Large‐Area Wire Grid Polarizer with High Transverse Magnetic Wave Transmittance and Extinction Ratio for Infrared Imaging System

Abstract

Infrared (IR) wire grid polarizer is the core device of polarization imaging system with exceptional properties. However, the fabrication of high-quality devices with large area and good uniformity remains challenging. Herein, a new high aspect ratio structure is designed and fabricated, which makes the polarizer have high transverse magnetic (TM) transmittance and extinction ratio in a wide wavelength band. This study also presents some innovations to traditional fabrication processes. These improvements make it easier to fabricate polarizers with good performance as well as large areas. In a very wide wave band (3-15 μm), the extinction ratio is over 32.33 dB. The average TM transmittance of the wire grid layer is 80%, and of the polarizer is 56.57%, which is almost the highest on silicon substrate without antireflection (AR) coating. Meanwhile, the diameter with good uniformity is larger than 30 mm. This method is highly reproducible and can be mass-produced. The polarizer can cover atmospheric IR windows in both 3-5 and 7-12 μm simultaneously, which is suitable in IR imaging systems for remote sensing and astronomy observation.

Modeling of the synergistic anti-reflection effect in gradient refractive index films integrated with subwavelength structures for photothermal conversion

“…When the grating period T is small enough and enters the resonance region, the diffraction becomes extremely unstable, which is known as the ''Rayleigh anomaly''. In this case, the relationship between the wavelength l and the incident angle y is expressed as: 44,45…”

“…When the grating period T is small enough and enters the resonance region, the diffraction becomes extremely unstable, which is known as the “Rayleigh anomaly”. In this case, the relationship between the wavelength λ and the incident angle θ is expressed as: 44,45 where n is the refractive index of the substrate (= 1.42) and j is the diffraction order. In this model, the grating period T is 100 nm and the wavelength λ is greater than 300 nm.…”

“…In this model, the grating period T is 100 nm and the wavelength λ is greater than 300 nm. Therefore, the grating is a subwavelength grating and satisfies the following relationship: 44,45 …”

“…In this case, only the zero-order diffraction exists, while all other orders are evanescent waves that do not carry energy. 44,45 Therefore, the properties of light waves do not change after passing through a grating. When a light wave passes through a grating, the direction of propagation does not change and there is no loss of energy due to diffraction.…”