Compact Multiband Polarisation Selective Filter in Mid-Infrared Region

Opportunity

Metamaterial-based filter for the mid-IR wavelength range can be used to probe the molecular vibration modes of different gases/chemical. Integral to spectroscopy, industrial imaging, medical imaging, and remote sensing, they enable selective material/molecule detection and analysis, ensuring high selectivity, minimal interference and efficient transmission/blocking of specific wavelengths within the mid-IR range.

Technology

The proposed device is based on a new type of two-dimensional material, molybdenum trioxide (MoO3). It exhibits strong phonon resonance in mid-IR regime, allowing the optical modal volume of the infrared photons to be squeezed by more than 106 times, while ensuring quality factors remain relatively high. The high confinement and long lifetime of the phonon resonance greatly enhance the light-matter interaction strength, which is desirable for high sensitivity sensing and efficient nonlinear optical processes.

The unique property of MoO3 supports in-plane hyperbolic dispersion, suggesting many interesting phenomena, such as non-diffractive and uni-directional beam propagation, negative refraction and arbitrarily high optical modal confinement. Leveraging these phenomena, a very selective, sensitive optical filter in the mid-IR wavelength range can be designed and fabricated.

Applications & Advantages

• Spectroscopy: Mid-IR filters facilitate precise molecular analysis in chemistry, biology, and environmental science by isolating specific wavelengths, aiding in structural and compositional studies. 
• Remote Sensing: Crucial in environmental monitoring, agriculture, and geology, these filters detect substances or phenomena via unique spectral signatures.
• Medical Imaging: Essential for IR imaging in thermography and diagnostics, mid-IR filters detect temperature variations and tissue composition.
• Industrial and Defence: Used in thermal imaging, gas sensing and surveillance, these filters identify gases and heat signatures.
• Communications: Enhancing IR communication and sensing devices, mid-IR filters ensure optimal signal transmission and reception, especially in interference-prone areas.
• Environmental Monitoring: Supporting air quality monitoring and pollutant detection, mid-IR filters contribute to environmental research and management. 

Advantages:

• Mid-IR wavelength range detection provides “fingerprints” of wider range of molecules.
• High selectivity with minimal signal interference.
• Supports multi-variate analysis.