From The Editor | March 18, 2024

5 Emerging Technologies Optical Coatings Are Helping To Develop

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By John Oncea, Editor

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Optical coatings enhance light properties in various emerging technologies such as AR/VR, LiDAR, and biomedical imaging, driving innovation and performance.

Optical coatings – thin layers of material that change how an optical component reflects and transmits light – play an important role in the performance of cameras, microscopes, lasers, telescopes, and other optical systems because they improve image quality, sensitivity, and light collection.

The integration of optical coatings with emerging technologies enables advancements in areas such as immersive displays, autonomous systems, communication networks, and biomedical instrumentation, driving innovation and expanding the capabilities of these cutting-edge applications.

We’re going to take a deeper look at the role optical coatings are playing with a couple of emerging technologies but first, let’s dig into what, exactly, optical coatings are.

Different Types Of Optical Coatings

Optical coating, also known as thin film coating, involves materials deposited on an optical element such as a lens or mirror to modify how the element transmits or reflects light. They also can, depending on the demand of application, improve the esthetic appeal of a material, make the surface smoother, and provide resistance against corrosion and wear. There are many different types of optical coatings, according to Thomasnet, with the most common including:

  • A beam splitter is a device that splits a single beam of light into two separate beams and also can be used in reverse to combine two beams of light into one. Beam splitters have both reflective and transmissive properties and are commonly used to control the behavior of light in laser systems, machine vision systems, and optical microscopy devices.
  • AR coating, which is used to minimize the reflection of light on surfaces. This helps to enhance light transmission and reduces glare. AR coatings are commonly used in eyeglasses, cameras, telescopes, binoculars, and microscope lenses to improve contrast and image clarity.
  • Protective films are a type of coating specifically designed to safeguard a substrate from potential damage caused by scratches, contaminants, or environmental factors. Although these coatings may also enhance specific optical properties, their primary function is to provide protection. These types of coatings are commonly found in various optical components, including eyeglasses, camera lenses, fiber-optic cables, and microscopy devices.
  • Polarizing films, composed of dielectric material, use the principles of interference to function. These coatings work with specific angles of incidence and wavelengths to reflect beams at specific angles and filter out unwanted wavelengths. Polarizing film coatings are especially helpful in sunglasses and television and computer screens as they improve visibility and reduce glare.
  • Reflective film is a type of optical coating that can reflect incident rays of light. Both metallic and dielectric coatings can significantly improve the reflectivity of an object in comparison to its uncoated version. Reflective-film coatings are useful in a range of applications, including telescope mirrors, laser cavity mirrors, and automotive mirrors.
  • Dielectric coatings are a type of optical coating made up of dielectric materials. These coatings consist of alternating layers of high and low refractive index materials for desired interference effects. Dielectric coatings can be used for reflective, anti-reflective, polarizing, or wavelength-selective purposes. They find their applications in camera lenses, binocular and telescope lenses, and optical filters.
  • An absorbent film is the opposite of a reflective film coating. It absorbs specific wavelengths of light and is useful when light needs to be attenuated or removed. In photography, absorbent films are particularly helpful in creating crisp and high-resolution images with the removal of unwanted light.
  • Wavelength-selective film is a type of optical coating that can selectively transmit or reflect specific wavelengths of light. This is particularly helpful in situations where certain wavelengths of light need to be eliminated while other desired wavelengths are maintained. For instance, wavelength-selective-film coatings are useful in optical communication devices like fiber-optic cables.

How Optical Coatings Enable Emerging Technologies

Optical coatings are integral to many emerging technologies such as augmented reality (AR), virtual reality (VR), LiDAR, and autonomous vehicles. As these technologies evolve, there will be increasing demand for specialized optical coatings and filters optimized for these applications.

  1. Augmented Reality (AR) and Virtual Reality (VR)

AR and VR devices use optical systems to project images or overlay digital information onto the user’s field of view. High-quality optical coatings are essential to reduce glare, reflections, and unwanted light leakage, improving the clarity and immersive experience for users. Specialized coatings may be used to enhance contrast, color fidelity, and image sharpness in AR/VR displays, providing a more realistic and engaging visual experience.

  1. LiDAR

LiDAR systems utilize lasers to measure distances and create detailed 3D maps of environments, commonly used in autonomous vehicles, robotics, and environmental monitoring. Optical filters are employed to selectively transmit or block specific wavelengths of light, allowing LiDAR sensors to distinguish between different objects and surfaces with greater accuracy. Coatings may also be applied to lenses and mirrors to improve optical efficiency, reduce stray light interference, and enhance the signal-to-noise ratio of LiDAR measurements.

  1. Autonomous Vehicles

Optical coatings and filters are integral to the sensors and cameras used in autonomous vehicles for perception and navigation tasks. Anti-reflective coatings help minimize glare and ghosting in camera lenses, ensuring clear and accurate image capture in diverse lighting conditions. Bandpass filters and polarizing filters may be employed to isolate specific wavelengths or polarization states of light, enhancing object detection and recognition in challenging environments.

  1. Photonic Integrated Circuits (PICs)

PICs are semiconductor devices that integrate multiple optical components such as lasers, modulators, and detectors onto a single chip, enabling compact and efficient photonic systems. Optical coatings are utilized to enhance the performance and reliability of PICs by minimizing optical losses, optimizing spectral characteristics, and controlling light propagation within the chip. Filters may be integrated directly into PIC designs to implement functions such as wavelength division multiplexing (WDM), spectral filtering, and signal routing in photonic communication networks.

  1. Biomedical Imaging And Sensing

Advanced coatings reduce reflections and maximize light transmission, improving image accuracy and clarity. Optical coatings enhance the sensitivity, resolution, and specificity of biomedical imaging and sensing systems. Fluorescence filters are commonly used in fluorescence microscopy and biomedical diagnostics to transmit emission wavelengths while blocking excitation and background light selectively. Coatings may be applied to optical fibers, lenses, and mirrors to improve light transmission, minimize autofluorescence, and optimize the performance of imaging and sensing devices in biological samples.

BONUS Technologies

  • Surveillance and remote sensing: Anti-reflective coatings on lenses and mirrors enable more reliable data collection in challenging environments
  • Defense and aerospace: Optical coatings improve safety, performance, and efficiency in satellites, aircraft, and military equipment. For example, thin film optical coatings improve the performance of satellite lenses and solar cells in space environments. They also can reduce reflectivity, which can help prevent interference with other satellites and space debris.

Improving The Performance Of Optical Filters

Researchers are attempting to develop more advanced coating materials and techniques, in part driven by a growing demand for coatings that can perform multiple functions simultaneously. An example would be anti-reflective coatings combined with scratch resistance or hydrophobic properties. Additional research is being done to improve the performance and durability of optical coatings in hopes it reduces manufacturing complexity and cost.

Increasing applications in areas like spectroscopy, imaging, and sensing are driving researchers to develop high-performance optical filters with precise spectral characteristics and high transmission or blocking efficiency. This could drive innovations in filter design and fabrication techniques.

Emerging industries such as solar and renewable energy require specialized optical coatings and customized solutions to meet their specific requirements. This is going to lead to a growing emphasis on developing environmentally friendly coating materials and processes, as well as coatings with improved resistance to environmental factors such as moisture, temperature variations, and UV radiation.

Efforts to reduce the cost of optical coatings through process optimization, automation, and economies of scale will continue to be important, particularly in high-volume applications such as consumer electronics.