The power of light

01 July 2021
By David Andrews

This issue puts a spotlight on the myriad ways that humans harness light. The conversion of light energy supports every form of life whose food chain traces down to photosynthetic organisms of some kind. The Sun powers our lives and, with other stars by night, reveals our visual world. Beyond the weak natural sources of light on Earth—bioluminescence in the marine and insect world, the phosphorescence of some minerals—only fire and flame provided any other possibility for illumination, until recent times with the introduction of incandescent bulbs.

The whole field of lighting experienced a major advance with the arrival of solid-state sources providing single-color emission. The first LED based on semiconductor electroluminescence, reported in 1927, led some 60 years later to OLED technology. The challenge of achieving usable output at the blue end of the visible spectrum led to development of high-brightness GaN emitters in the early 1990s, paving the way for revolutionary new forms and applications of solid-state lighting. Combining red, green, and blue LEDs, or using an adjunct phosphor, these new simulations of daylight have rapidly displaced the much less efficient, earlier forms of light bulb.

Many modern forms of display technology utilize the activation of individual colors, supplemented by quantum dots in the last decade, while a facility to modify the spectrum of radiant illumination leads to other applications. In our homes we can now have controllable mood luminaries; in agriculture, lighting optimizes the growth of specific crops with suitably engineered wavelengths.

Beyond the numerous applications in electrical lighting, it is interesting to observe the flip side of the coin: the conversion of light into electrical energy. All are familiar with carbohydrate synthesis in photosynthesis, but studies now indicate a possible future for artificial leaves in synthesizing fuel. In both respects, light-driven electrical charge separation drives the underlying molecular mechanisms.

Since the development of the first semiconductor-based forms of the solar panel, the steady improvement in designs and efficiency has progressively led to its domination of global energy harvesting. Solar power is now a major contributor to national power grids straining to address energy demand. Microgrid implementations secure power for communities too remote for connection to urban networks, while solar lamps can provide night-time power in even less well-endowed communities. Interconversion between electrical energy and light continues to blaze new paths of application, empowering human lives and transforming societies.

On a final note, I am delighted that after a hiatus of more than a year, we can return to in-person conferences, resuming operations in San Diego for SPIE Optics + Photonics, 1-5 August. There is a valuable legacy in the sophisticated digital operations that can now sustain conferences for remote participants, and our online meetings have been warmly welcomed by SPIE constituents. But zooming becomes wearisome; there is no way to replicate the experience of an exhibition floor, the serendipitous encounters, live lecture-floor interactions, receptions, and networking events. Large-scale meetings simply don't translate to an online format. We have heard loud and clear the message that no experience can match meeting in person; the freedom to do so is, indeed, a cause for real celebration.

David Andrews

David Andrews

2021 SPIE President

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