Shift-free fixed-line laser protection filter technology

Abstract

The development of shift-free fixed-line filters is a key technology for advancing the next generation of laser protection and is greatly desired due to the increased threat of laser attacks. Thin-film interference coatings have remained the key technology for achieving narrow bandstop filters for protection against laser light since the late 1970s. This paper presents the latest developments in fixed-line laser technology and introduces a metamaterial solution to mitigate the angular shift found in thin-film interference coatings. The metamaterial coating consists of metallic nano-particles periodically distributed within a non-absorbing dielectric material with a specific refractive index that enables the desired plasmonic resonance to exist at wavelengths that match that of the lasers. Due to the nano-particle size, the metamaterial layer can be treated as an individual homogeneous layer with properties described by an effective Drude-Lorentz approximation model. Unlike standard interference coatings where the effective index of the stack decreases with larger angles of incidence, the metamaterial's effective index remains relatively fixed with increasing angles resulting in the narrow bandstop function remaining shift-free.

Optimized Wide-Angle Metamaterial Edge Filters: Enhanced Performance with Multi-Layer Designs and Anti-Reflection Coatings

“…The blue shift of the spectrum is approximately 80 nm when the incident angle is increased from 0 • to 60 • s for the transverse electric (TE) waves and 100 nm for the transverse magnetic (TM) waves. The blue shift in the thin-film filters at increased angles of incidence results from changes in phase thickness and the variation of effective admittance, influenced by the Brewster angle, which separates the band edges at higher angles [24]. This shift does not satisfy the requirements for numerous applications.…”

Nanoengineering instrumentation to control the optical properties of plasmonic nanoparticles for thin film optics

“…Dielectric thin film filters are an excellent technology that will not be surpassed with ease. Nonetheless, they do have some drawbacks; more noticeably their ability to shift to short wavelengths as the angle of incidence increase [22] . This can be used as an advantage for a lot of technology including chemical sensing.…”

Laser protection by using vortex wavefront coding imaging system

“…There are two feasible technical ways to prevent laser blindness in the photoelectric imaging system: one is to use laser protective materials and the other is to develop new photoelectric imaging systems. Laser protective material technology utilizes linear materials, 5,6 nonlinear materials, [7][8][9][10] and phase change materials [11][12][13][14] to make light filters for the protection of photoelectric imaging devices, which is a relatively common laser protection method; however, so far, there are still disadvantages, such as narrow protective bandwidth, slow reaction speed, and low protective strength. 15 At the same time, the increasing power and wavelength broadening of lasers [16][17][18] make laser protection of photoelectric imaging systems more difficult.…”