Small wonder that the light bulb, more than a century after its invention, remains the symbol of innovation. For we have entered the Age of Light. The age began in May 1960 with the flash of the first laser. It has expanded exponentially ever since. Light now reads documents, plays music, performs surgery, measures buildings, beams messages, and so much more.
The ages of steam and coal are long gone. With oil clinging to power, light is emerging as our Deus ex Machina. Light goes where nothing else can, gets there faster than anything else could, and brings back the photos. If there are limits to light, other than its cosmic speed limit, we have not tested them. If there is a final answer to light – the answer Einstein never stopped seeking — we have not found it. The Age of Light is here, and here are some of its latest wonders. Imagine…
Imagine stimulating the brain not with electrodes but with pulses of light. In 2011, researchers at Stanford University used light to calm anxious mice. First Dr. Karl Deisseroth and his team treated the mice’s amygdala — the brain’s seat of depression — with opsins, proteins in the retina that absorb photons and trigger the optic nerve. Then the researchers fired blue beams to switch off the primed neurons. The anxious mice calmed, even when placed in open fields where predators might lurk. Beyond making mice feel better, optogenetics is changing neuroscience. If pulses of light can excite the amygdala, what other functions normally stimulated by intrusive electric probes might be triggered by light? Optogenetics is still in incubation, but the National Institute of Health considers the field “the most revolutionary thing that has happened in neuroscience in the last couple of decades.”
Imagine a laser beam that lasts just a femtosecond — one quadrillionth of a second. Imagine its stimulated emissions creating pressures three times as dense as the sun’s center. Such a laser already exists at the National Ignition Facility in Berkeley’s Lawrence-Livermore Lab. In 2014, NIF scientists achieved “ignition,” the creation of energy through fusion, as in the sun. The world’s most powerful laser heated and compressed hydrogen atoms into helium, releasing more energy than was added to the mix. Though still in its infancy, this first ignition fanned the biggest possible dream about light. “If we can harness this fusion reaction,” NIF staff scientist Tammy Ma said, “this gives us limitless and sustainable energy for humankind.”
Making light has always been messy, hot, and wasteful. Candles smelled. Torches smoked. Incandescents, even long after Edison, squandered most of their energy in heat.. Then came the Light Emitting Diode, the LED. Emitted by electrons jumping a “P-N junction,” the light of LED was first red, then a shorter wavelength green. But when blue was finally added in the 1990s, the three together made white. Ever since, LEDs have been the light of the future.
Because they waste little heat, LEDs use twenty times less energy than incandescent bulbs. In a world where nearly one-fifth of all electricity is used to make light, LEDs carry their own brand of hope. In African villages, solar powered LEDs are already replacing smoky kerosene lamps. In 2014, The Nobel Prize for Physics went to the three inventors of the blue LED. The LED, the Nobel committee said, “holds great promise for increasing the quality of life for over 1.5 billion people around the world who lack access to electricity grids.”
Imagine invisibility. If light could somehow be diverted around an object, that object would become invisible. Though it suggests Harry Potter’s magical cloak, invisibility is no longer left to witchcraft and wizardry. In 2006, Duke University scientists embedded small ceramic chip with microscopic circuits whose electro-magnetic field bent oncoming microwaves. The chase was on to make “metamaterials,” substances that could divert higher energy waves of light. Again, the future arrived quickly. By 2008, scientists at UC Berkeley had engineered a composite material with a fishnet weave whose holes were more compact than a red light wave. The material bent some light around it and let other wavelengths pass through. The field of metamaterials is now one of the hottest in optics.
Computing with Light
Imagine a computer whose circuits are fired by light. In 2010, photonics engineers at IBM created a semi-conductor chip that converts photons to electrons, then uses the charged particles to process data. Four years later, two German scientists activated a transistor not with a charged electron, as usual, but with a single photon. The emerging field of Silicon Nanophotonics is not expected to replace desktops and laptops, but the advantages of computing with light — cooler, faster, more efficient than electricity — parallel the advances of fiber optics over copper phone wires. By 2020, some expect super computers in industry and medicine to begin converting to photons.