The Vision of Light

Let there be light! 

Light and colors are omnipresent in our lives, offering both practical benefits and aesthetic beauty. Despite its familiarity, light remains a profound mystery, particularly in how it influences us emotionally. We find ourselves captivated by the hues of a sunset, the ethereal dance of the northern lights, or the serene beauty of a sunrise. Light, and even its absence, can stir our deepest emotions, painting our lives in vivid colors. 

Beyond its emotional impact, light has been a subject of scientific inquiry for thousands of years. Despite significant advancements in our understanding, light continues to puzzle us, especially in the realm of physics. One of the most intriguing aspects of light is its dual nature: is it a wave or a particle? This question has baffled scientists for centuries. Since the early 20th century, we’ve come to accept that light is both—a concept that remains difficult to fully grasp. 

The initial understanding of Light 

Historically, the first serious studies of light and vision were undertaken by the ancient Greeks. Thinkers like Euclid and Pythagoras (~500 BCE) proposed that light emanated from the eyes. While this idea might seem strange today, it likely stemmed from observations of animals like cats, whose eyes appear to glow in the dark, giving them a seemingly supernatural ability to hunt at night. 

Interestingly, even though this concept was eventually debunked, it continues to influence our language: expressions like "twinkling eyes," "eyes lit up," or "starry-eyed" persist, reflecting an intuitive connection between light and vision. 

The Golden Age of the Islamic world (750–1258 CE) brought significant advances in the study of light and optics. Scholars like Ibn al-Haytham (also known by his Latin name Alhazen), known as the Father of Optics, made groundbreaking contributions. His seminal work, "Kitab al-Manazir" (The Book of Optics), laid the foundation for many modern concepts of light as early as 1010 CE. Key discoveries from this period included the realization that light originates from luminous bodies like the sun or fire, existed of “particles”, travels in straight lines, and possesses a finite speed. He experimented with measuring the speed of light, but as to be expected then, the results were not too accurate. 

The concept of the camera obscura as perceived a thousand years ago by Ibn al-Haytham, referred to as "the father of modern optics". He was the first to correctly explain the theory of vision.

📷 History of Islam - An encyclopedia of Islamic history

The laws of reflection and refraction, essential principles in optics, were also formulated during this time.  Arab thinkers like Al-Farisi first proposed the wave nature of light and first described advanced optics (by today's standards), such as parabolic and aspheric lenses long before they were (re-)discovered by European scientists like Snell in the 17th century.  

During the Renaissance, when al Haytham's books were translated into Latin and circulated throughout Europe, the interest in light and optics also came to Europe. Figures like Leonardo da Vinci studied the concepts of light, shadow, and perspective became central to innovations in European art and painting. 

Waves, particles, or both? 

In the 17th century, Isaac Newton made significant strides in optics, proposing that light consists of particles ("corpuscles").  Although he was unaware of photons, his particle theory successfully explained many phenomena, such as the straight-line travel of light, the formation of sharp shadows, and the behavior of colors through a prism. However, the lesser-known physicist Christiaan Huygens argued that light was a wave, particularly to account for diffraction—light bending around objects. 

Huygens' wave theory also explained reflection and refraction more elegantly, but Newton rejected Huygens’ wave theory and Newton’s prominence overshadowed this wave concept, that had already  been described by Arab scholars centuries earlier.  

Sir Isaac Newton - Opticks, A treatise of the reflections, refractions, inflections and colors of light.

One of the great works in the history of science, documents Newton’s discoveries from

his experiments passing light through a prism.

📷 Smithsonian Libraries

A century later, Thomas Young’s famous double-slit experiment provided compelling evidence that light behaves as a wave, showing an interference pattern that could only be explained by wave theory. However, another century later, the photoelectric effect—crucial for technologies like solar panels—could only be explained by treating light as particles (photons). This work earned Einstein a Nobel Prize, underscoring the dual nature of light as both a wave and a particle. 

So, what is light? The answer is paradoxical: it is both a wave and a stream of particles simultaneously. This concept, known as wave-particle duality, extends to electrons as well, as demonstrated by Louis de Broglie. His hypothesis that particles, like electrons could also exhibit wave-like behavior was later confirmed by experiments, earning him a Nobel Prize. 

Photonics 

As our understanding of light deepens, we’ve begun exploring new frontiers in technology, particularly in the field of photonics—the study and application of light and photons as an alternative to electricity and electrons. Photonics is driving innovation much like electronics did in the past century, with photonic integrated circuits (PICs) offering exciting possibilities by replacing electrons with photons. 

One major advantage of photons over electrons is their lack of mass; photons are massless and they propagate much faster than typical electrons drift through copper cables. This has significant implications for data communication, where fiber optic cables—transporting photons—are increasingly replacing traditional cables that carry electrons. Additionally, fiber cables offer benefits like better bandwidth, faster speed, longer transmission distances and stronger security. However, photons also present challenges: they lack charge and, therefore, they go where they go, possibly bouncing in all directions, making them more difficult to control than electrons. 

Despite these challenges, photonics is advancing rapidly. The development of fiber optics was a major breakthrough, allowing photons to travel through fibers with minimal loss. Yet, fibers have limitations, such as signal degradation over long distances, requiring amplification. Another challenge lies in connecting optical fibers without causing signal reflection. Unlike electricity, which is relatively easy to manage due to the charge of electrons, light requires more precise handling. 

Photonic Integrated Circuits 

Nonetheless, the benefits of photonics are driving its adoption, especially in PICs, which are analogous to electronic integrated circuits but operate with light/photons. PICs can perform many of the same functions as electronic circuits, such as splitting, combining, amplifying, and filtering signals. However, for PICs to be practical, they must interface with electronic circuits, converting electrical signals to optical signals and vice versa. This technology is already in use in internet fiber connections, where electrical signals are converted into light for transmission and then back into electrical signals at the receiving end. 

Another key difference between ICs and PICs is how they operate. Electronic ICs require power not only to function but also to move electrons through circuits. In contrast, PICs are passive, relying on an external light source, usually a laser, to generate the photons needed for operation. This brings us to the importance of light sources. 

Wideband lasers 

Historically, the sun was humanity’s only light source until fire was harnessed. It wasn’t until about 150 years ago that Edison’s invention of the light bulb revolutionized how we live. Since then, various artificial light sources have been developed, including efficient LED lights used in homes and screens. 

The invention of lasers in 1960 marked another milestone. Lasers produce highly collimated, coherent, monochromatic light beams with a wide range of applications, from everyday laser pointers to industrial, medical, and even military uses. Lasers also play a crucial role in photonics, providing the photons necessary for PICs to function. 

Charles Townes in 1955 with the maser – the microwave beam predecessor to the laser

While most lasers produce a single wavelength (monochrome), some applications require a broader spectrum of light. Wideband lasers, or supercontinuum generation lasers, produce a wide spectrum of coherent light, as if they were a whole set of indistinguishable lasers next to each other, making them valuable in fields where more detailed information is needed, such as (bio-)medicine and industry. 

In medicine, for example, wideband lasers can improve the accuracy of endoscopic procedures by providing full-color images with more detail than monochrome lasers. In industry, wideband lasers can enhance fault detection and quality control, while in agriculture, they can improve efficiency in monitoring nutrients and disease. 

Looking to the future, wideband lasers could play a critical role in self-driving cars, providing the detailed, full-color imaging needed to detect obstacles on the road. They could also revolutionize data communication by increasing bandwidth through the simultaneous transmission of hundreds of colors of light. 

The Future of Light 

Moore’s Law, which has driven technological progress for decades, is approaching its limits as electronic circuits reach their physical size constraints. Photonics offers a way to extend Moore’s Law by replacing electrons with photons, pushing technology to new heights. This is why the integration of photonics with electronics is so important—it represents the next step in technological evolution. 

SuperLight Photonics is at the forefront of this revolution. Our motto, "Better light, more insight," reflects our commitment to advancing photonics technology for the betterment of society.

By harnessing the power of light, we aim to create a brighter future for all.