A Look At The Role Photonics Play In Environmental Sensing

By John Oncea, Editor

Photonics-based technologies play an important role in environmental sensing, enabling more accurate, real-time, and comprehensive monitoring of various environmental parameters and conditions.

Environmental sensing is the use of various technologies and techniques to monitor, measure, assess, and analyze various aspects of the environment, such as air quality, water quality, soil conditions, and more. Photonics has numerous applications in environmental science and monitoring, significantly helping researchers do their jobs.

Drone surveying using InGaAs image sensors and modules, soil measurement using NIR spectrometers, water analysis using UV mini-spectrometers, gas analysis using high-power mid-infrared LEDs and high-sensitivity InAsSb detectors, and plastic recycling using X-ray line scan cameras, InGaAs area image sensors, FT-NIR spectrometers, and Raman spectrometers with built-in CMOS image sensors and lasers are just some of the ways photonics is used in environmental applications.

Photonics In Action

Photonics is used in a variety of environmental applications, from monitoring water quality and tracking greenhouse gas emissions to developing solar energy technology and mapping land use. Its ability to measure light absorption and scattering allows for highly accurate and detailed monitoring of the environment.

One technique – laser ranging – uses laser beams to more accurately measure distances, according to Optica. This method is useful for determining changes in elevation for solid objects, such as ice sheets. NASA's ICESat-2 mission, for example, uses satellites equipped with LiDAR to measure the changing height of Earth’s ice, including glaciers and sea ice.

Hyperspectral imaging is a technique that captures the full spectral data of each pixel in an image. This enables researchers to identify patterns of healthy and diseased life forms in their habitats, making it useful for monitoring ecosystems and vegetation health, as well as detecting changes in land cover.

Advancements in portability have enabled laser spectroscopy to fill gaps in our understanding of atmospheric gases’ distribution. The technology aids in detecting problematic gases such as greenhouse emissions, contributing to the assessment of climate change. Other techniques include:

1. Spectroscopic analysis: Photonic sensors can use spectroscopic techniques, such as Fourier-transform infrared spectroscopy (FTIR) and light detection and ranging (LIDAR), to identify the chemical composition of air, water, and soil by analyzing the absorption and emission spectra of different molecules and compounds.
2. Remote and satellite-based sensing: Photonic technologies, including remote sensing and satellite-based systems, can be used to monitor environmental conditions over large geographical areas, such as deforestation, ecosystem health, and pollution levels.
3. In-situ and point-of-contact measurements: Photonic sensors can be used for in-situ and point-of-contact measurements of environmental parameters, such as water quality, gas composition, and more. This allows for real-time monitoring and rapid response to environmental changes.
4. Weed and crop sensing: Photonic-based sensors can be used in agriculture to detect and differentiate between weeds and crops, enabling more efficient and sustainable farming practices.
5. Extreme environment sensing: Photonic sensors can be used to monitor environmental conditions in extreme environments, such as combustion, flames, plasmas, and explosions, where traditional sensors may not be able to operate effectively.

The Photonics Advantage

Photonics-based sensors play a crucial role in revolutionizing environmental monitoring and pollution detection. They offer several advantages over traditional analytical methods for environmental monitoring, including:

• Faster, more sensitive, and more selective detection of various pollutants and contaminants.
• They enable real-time, on-site monitoring capabilities, unlike centralized laboratory-based techniques.
• Photonic sensors can be integrated into portable, low-cost devices for widespread deployment.
• Photonic technologies like optical waveguides, fiber optics, and laser-based spectroscopy are enabling new sensing approaches for air quality, water quality, and other environmental parameters.

The precision, versatility, and cost-effectiveness of photonics-based sensors are revolutionizing how we monitor and protect the environment, paving the way for a more sustainable future. That said, some challenges come with them.

While photonics technology and machine learning have advanced separately, fully integrating them to realize high-accuracy environmental monitoring sensors has not been fully explored yet. A second challenge is developing small-, medium-, and large-scale photonics-based sensor networks. Scaling photonics-based sensor systems from individual devices to interconnected networks for comprehensive environmental monitoring remains a challenge.

Enabling photonic sensing techniques for extreme environments like combustion, flames, plasmas, and explosions requires overcoming significant technical hurdles. Other challenges include improving the cost-effectiveness and portability of photonic sensors, as well as transitioning photonic technologies from laboratory settings to practical, low-cost, and portable devices for widespread field deployment.