This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A research team from Singapore, led by Associate Professor Dawn Tan of the Singapore University of Technology and Design (SUTD) and Dr. Luo Xianshu, head of the Silicon Photonics Department at the A*STAR Institute of Microelectronics (A*STAR IME), has developed a low-loss silicon nitride waveguide that generates broadband light on a chip.
By replacing hydrogen with its heavier isotope, deuterium, the team fabricated the low-loss SiN waveguide on an 8-inch wafer using a low-temperature process, demonstrating its potential for large-scale manufacturing and integration with CMOS-compatible semiconductor processes. Published in Optics Express, the paper "Octave-spanning supercontinuum generation in a wafer-scale, low loss deuterated silicon nitride waveguide" demonstrates a chip-scale waveguide that stretches infrared laser pulses into a spectrum running from visible red to deep into the infrared. Lasers are prized for their color purity because they emit light in a single color, but many of the most demanding technologies require a beam that spans an enormous sweep of the spectrum at once.
This so-called supercontinuum light underpins high-resolution medical imaging, precision measurement and the frequency combs that keep optical clocks ticking without error. Today's supercontinuum sources are mostly built around specially engineered optical fiber, but they are bulky, power-hungry and difficult to shrink onto a chip. The most compatible chip material is silicon nitride, but making it transparent enough demands conditions so extreme that thick films crack.
Standard semiconductor factories also cannot accommodate the process. "The primary gap is the need for compact, energy-efficient, and integrable light sources," said Yao Wang, a doctoral student and first author on the paper. "While fiber-based systems are standard, they are bulky and not easily integrated onto chips." The trouble with conventional silicon nitride traces back to hydrogen.
Films are typically grown from silane gas, leaving behind silicon-hydrogen bonds that absorb light at precisely the wavelengths telecommunications systems use. Purging those bonds requires hours of annealing at up to 1,200 degrees Celsius—a temperature no chip carrying electronic circuitry could survive and one that builds crippling stress into thick films. So, the researchers swapped ordinary silane for its deuterated cousin, replacing each hydrogen atom with the heavier isotope deuterium.
"This substitution achieves a physical shift. The absorption peak moves from the telecommunications range to the 2.1 micron region," explained Tan. "Because light is no longer being absorbed at the operating wavelength, the high-temperature baking process is no longer necessary." The resulting fabrication process is simple.
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