Engineering Inside:

2016 Issue 1
Light

Lighting the Way Toward Progress

February 2016

by Robin Hegg

LED flashlight with a light beam. Lighting concept

Light can come from heat, a chemical reaction, electrical energy, even stress on a crystal. Most of the visible light we encounter comes from the sun and it is this visible light that allows us to see and more fully experience the world around us. It gives us heat, energy, and food. At its most basic, light is electromagnetic radiation. The range of electromagnetic radiation visible to the human eye is referred to as “visible light,” which has a wavelength in the range of 400-700 nanometers. Each color of the rainbow occupies a different range of wavelengths with red being the longest and violet the shortest. Beyond the longer wavelengths of visible light is infrared light, and beyond the shortest wavelengths of visible light is ultraviolet light. Visible light exhibits properties of both waves and particles. This property of light is called the wave-particle duality. When thinking of light as a collection of particles, these particles are called “photons.”

Because light is so vital to humans, it didn’t take long for humans to begin to engineer new light-related technology, beginning with developing campfires, fuels, oil lamps, and electric lights. The study and science of light have continued to grow. Two of the major scientific fields involving light are optics and photonics. Optics focuses on light’s properties and behavior and how light interacts with matter. It also covers the development of instruments that use and detect light. Photonics is the science of generating, controlling, and detecting photons (particles of light). Photonics includes the science of light emission and transmission, modulation, signal processing, switching, and detection and covers all of light’s technical applications.

Light-related technology has come to influence everything from lighting, to advanced lenses and mirrors for cameras, microscopes, and telescopes, the development of fiber optic cables for communication and computing, the development and use of lasers, and the wide variety of uses of infrared radiation. Light-related technologies impact communications, computers and robotics, human sight, medicine, and the exploration of outer space.

hanging tungsten light bulb energy saving and LED bulb

hanging tungsten light bulb energy saving and LED bulb

The light bulb, one of the most basic light-related technologies, has changed drastically over the last few decades, becoming more efficient and longer lasting. The original incandescent light bulb, which uses a wire filament that is heated by an electric current until glows, was incredibly inefficient, converting less than 5% of the energy it uses into light, the rest of the energy being converted into heat. Compact fluorescent bulbs, which work by running an electric current through mercury gas, are able to last 8-15 times longer than incandescent bulbs. Light-emitting diodes, or LEDs, which use work by applying voltage to two-lead semiconductors, produce electroluminescence. They produce no heat and are very efficient, and are currently being used in lighting, aviation lighting, car headlights, camera flashes, traffic lights, and more.

Light-related technologies extend far beyond simple lighting, however. Light is revolutionizing communications and computing technologies. Light is used, as infrared radiation, to allow different devices to communicate with one another and to operate switches, whether it’s a remote control turning on a television, or two robots communicating with one another.

Blue fiber optic cable with stripped and exposed fibers

fiber optic cables

The development of fiber optic cables has allowed light to be used to send information quickly over long distances, creating vast and efficient computer networks. Optical fiber is a thin, flexible, and transparent fiber made from glass or plastic that is about the thickness of human hair. The fibers are used to transmit light from one end of the fiber to the other. Optical fibers can be bundled together into cables that can allow the transmission of data over longer distances and at higher bandwidths than wire cables. Fiber optic cables also experience less signal loss than metal wires and immune to electromagnetic interference.

A new super small laser (a device that emit an intense beam of light of the same wavelength) promises to bring the speed of optical communications to computer chips. Just as optical fibers have allowed computers to send data quickly across long distances, these lasers (vertical-cavity surface-emitting lasers or VCSELs) could massively speed up a computer’s processing. Researchers have created a silicon-based chip that produces laser beams, making it possible to use laser light instead of wires to send data.

medical laser

medical laser

Lasers are also changing the way doctors treat their patients. Laser surgery, which uses lasers instead of a blade, allows for increased precision and easier healing. Lasers can also be used to remove diseased tissue, treat blood vessels, correct vision, remove wrinkles, tattoos, and birthmarks, and even deliver radiation to cancerous tissue. .

In the developing field of optogenetics, cells are genetically modified so they can be activated by light. Researchers have been able to use this method to control the electrical waves that regulate our heartbeat. The scientists used gene therapy techniques to deliver a protein called channelrhodopsin to heart cells. This allowed them to be controlled by light. They then used a computer-controlled light projector to control the speed and direction of cardiac waves. This technique could provide an alternative pacemakers, defibrillators, or drugs, which are currently used to start or stop cardiac waves, but aren’t able to control speed or direction.

Thermal Image of Heat Leak through Windows

Thermal Image of Heat Leak through Windows

Light-related technologies have also changed how we’re able to explore the Universe. Infrared radiation, the radiation with wavelengths longer than visible light but shorter than radio waves, can also has a number of applications in technology. When there isn’t enough visible light available to see, infrared radiation can be used to “see” by detecting heat and creating an image. Heat sensing technology like this can be used for night vision, in search and rescue operations, and by police and military. Infrared radiation is also used by astronomers to locate objects in outer space, and through a process called spectroscopy, infrared radiation can be used to discover the structure and composition of a material by seeing what infrared radiation is able to pass through a material.

James Webb Space Telescope. This image elements furnished by NASA

James Webb Space Telescope. This image elements furnished by NASA

The Hubble Space Telescope, which was launched in 1990, was the first space-based observatory, allowing us to view outer space without having to see through the Earth’s atmosphere. Since then, more space telescopes have been developed that are able to view a wider range of wavelengths, but they are still limited in how far they can see, and in space, the farther you can see, the farther back in the history of the universe you can see. The Hubble Space Telescope is able to see back to galaxies that are about 500 million years old. The James Webb Space Telescope (JWST) is due to launch in October 2018. The telescope will be able to gather more than seven times the amount of light that Hubble can, do ultra-high resolution spectroscopy for wavelengths from 600 nanometers to 6 microns, and cool its instruments, all of which should allow it to view the early Universe like no telescope has done before.

Light, through its different properties and forms, has proved to be an incredibly valuable resource for humans, far beyond its use as a simple light source. Light is used in technologies across disciplines, improving the way we share information and communicate with one another, helping us to heal one another, and allowing us to learn about things far beyond the scope of our own world.

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