Wazzup Pilipinas!?
A team from UP Diliman has achieved what was once thought nearly impossible—measuring an elusive light phenomenon in everyday materials that could revolutionize semiconductor technology
In a darkened laboratory at the University of the Philippines Diliman, a laser beam strikes a silicon surface. To the naked eye, nothing unusual happens—the light bounces off at a predictable angle, obedient to the laws of reflection we all learned in high school. But peer closer, with instruments sensitive enough to detect shifts smaller than a human hair, and something extraordinary reveals itself: the light doesn't land quite where it should.
It shifts. Sideways. Impossibly subtle, yet undeniably real.
This ghostly displacement, known as the Goos–Hänchen shift, has haunted physicists since its theoretical prediction nearly a century ago. Now, for the first time, a team of Filipino scientists has successfully measured this elusive phenomenon in the very materials that power our modern world—semiconductors and photonic devices—opening doors to applications that could transform everything from quality control in chip manufacturing to our fundamental understanding of how light behaves.
The Phantom in the Mirror
The Goos–Hänchen shift is one of nature's most mischievous tricks. Named after German physicists Fritz Goos and Hilda Hänchen who first observed it in 1947, the effect occurs when light undergoes total internal reflection—the same principle that allows fiber optic cables to carry information at the speed of light. But instead of reflecting from a precise point, the light beam appears to penetrate slightly into the reflecting surface before bouncing back, causing it to emerge shifted from where classical physics says it should.
"Imagine throwing a ball at a wall," explains Jared Joshua Operaña, lead researcher from the UPD College of Science's Materials Science and Engineering Program. "You expect it to bounce straight back. But what if, impossibly, it seemed to pass partway through the wall before returning—and came back shifted to the side? That's essentially what light is doing."
The shift is vanishingly small—typically measured in wavelengths of light, or mere hundreds of nanometers. For context, a human hair is about 80,000 nanometers thick. Detecting such minute displacements requires extraordinary precision and, until now, had only been reliably observed in metals or specially engineered exotic structures where the shifts are relatively large.
Breaking Through the Impossible
The real challenge lay in materials that barely interact with light at all—so-called "low-loss dielectrics" like silicon and gallium arsenide, the workhorses of the semiconductor industry. Theoretical physicists had long predicted that these transparent materials should produce unusually large Goos–Hänchen shifts, but there was a catch: the effect would only manifest within an impossibly narrow range of angles, making it nearly undetectable with conventional measurement techniques.
"Until now, GH shifts were mostly observed in metals or exotic layered structures, because these are the materials where GH shifts are relatively larger and thus are easily observed," Operaña said. "But theoretical studies have long suggested that even ordinary, uncoated dielectrics with very little light absorption should produce unusually large GH shifts."
It was a prediction waiting decades for confirmation.
Working in the Structured Light and Applications Lab at the National Institute of Physics, Operaña and his collaborators—Drs. Niña Zambale Simon and Nathaniel Hermosa—spent countless hours perfecting their experimental setup. The breakthrough came when they developed a method sensitive enough to capture shifts occurring within those razor-thin angular windows.
The results were stunning.
Silicon's Secret Revealed
When the team trained their laser beams—at wavelengths of 543 and 633 nanometers—onto silicon surfaces, they measured shifts up to 100 times the wavelength of the light itself. In the quantum world, this is enormous. Even more remarkably, the size of the shift varied dramatically depending on how much light the material absorbed. Silicon, which absorbs less light than gallium arsenide, produced larger shifts—a counterintuitive finding that reveals just how sensitive this phenomenon is to a material's optical properties.
"We showed that silicon, which absorbs less light than gallium arsenide, produces a shift up to 100 times the wavelength of the laser beam," Operaña noted, his voice carrying the quiet pride of someone who has just proven the skeptics wrong.
This marks the first experimental confirmation of theoretical predictions made decades ago, transforming the Goos–Hänchen shift from an academic curiosity observed only in specialized materials into a measurable phenomenon in the semiconductors that underpin modern technology.
From Laboratory Curiosity to Industrial Revolution
The implications ripple outward in unexpected directions. The extreme sensitivity of the Goos–Hänchen shift to minute variations in material properties suggests a powerful new tool for both industry and research.
In semiconductor manufacturing, where the difference between success and failure can come down to impurities measured in parts per billion, the ability to detect subtle variations in light absorption could revolutionize quality control. "In the commercial setting, compact instruments based on GH-shift detection could be developed for quality control in semiconductors, photonics, and advanced coatings, where precise control of material properties is critical," Operaña explained.
Imagine a handheld device that could instantly verify the optical quality of a silicon wafer without touching it, or identify defects in photonic components before they're assembled into devices. The technology could catch manufacturing flaws that current methods miss, potentially saving millions in rejected products.
But the reach extends beyond industry. In academic laboratories, this method provides researchers with an unprecedented window into light-matter interactions. How do different materials manipulate photons at the nanoscale? Can we engineer surfaces that control the Goos–Hänchen shift for novel applications? The questions multiply with each possibility.
The Road Ahead
The UP Diliman team isn't stopping at visible light. Their next goal is to expand their method across the electromagnetic spectrum, testing wavelengths beyond what the human eye can see—perhaps into the infrared or ultraviolet regions where semiconductors operate most efficiently. Other researchers might modify material properties to enhance or suppress the shift for specific applications.
The study, published in Optics Letters and funded by the Department of Science and Technology's Philippine Council for Industry, Energy, and Emerging Technology Research and Development (DOST-PCIEERD) and the UP Office of the Vice Chancellor for Research and Development, represents more than just a technical achievement. It's a reminder that Filipino scientists continue to push the boundaries of what's possible, often with limited resources but unlimited ingenuity.
The Poetry of Light
There's something profoundly beautiful about the Goos–Hänchen shift. In an age where we often take light for granted—flipping switches without thought, streaming data through fiber optics without wonder—it reminds us that photons still hold mysteries. Even something as simple as a reflection harbors hidden depths, quantum subtleties that challenge our classical intuitions.
That a team working in Manila has now illuminated one of these mysteries, measuring what was thought nearly unmeasurable, speaks to the universal nature of scientific inquiry. The same laser light that bounces off silicon in a Philippine laboratory obeys the same laws that govern starlight crossing the cosmos. And now, thanks to Operaña and his colleagues, we understand those laws just a little bit better.
The light shifts. And so does our understanding of the universe.
Ross is known as the Pambansang Blogger ng Pilipinas - An Information and Communication Technology (ICT) Professional by profession and a Social Media Evangelist by heart.
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