![]() “We are the first team to show a laser’s phase-stable operation under the protection of our optical isolator,” said Yu.Īltogether, the advance represents a significant leap forward for practical, high-performance optical chips. “Since the light doesn’t have to travel so far, there is less decay and loss of power,” Cheng said.įinally, the teams showed that the device can successfully protect an onchip laser from external reflection. The scaled-down dimensions and ultralow loss property of this platform also boost optical power. “With a smaller device, you can control light more easily and also put that light in closer proximity to the electrical signals, thus achieving a stronger electrical field with the same voltage,” enabling more powerful control of the light, Yu said. The reason we can do this with such remarkable performance is because of lithium niobate’s properties.”Īnother reason for the high performance and efficiency has to do with the size of the device - the team built it at the Harvard Center for Nanoscale Systems, fabricating a chip measuring 600 nanometers thick with etchings (to guide the light using prescribed nano-structures) up to 320 nanometers deep. “All previous attempts at engineering something like this required multiple resonators and modulators. “What’s exceptional about this device is that at its core it’s incredibly simple - it’s really just one single modulator,” said Rebecca Cheng, co-first author on the paper and a current Ph.D. In addition to isolation, it offers the most competitive performance across all metrics including loss, power efficiency, and tunability.” ![]() ![]() “To our knowledge, when compared to all other demonstrations of integrated isolators, this device performs the best optical isolation. “We wanted to create a safer environment for a laser to operate in, and by designing this one-way street for light, we can protect the device from the laser’s reflection,” said Mengjie Yu, co-first author on the paper and a former postdoctoral researcher in Lončar’s lab. “This is accomplished by sending electrical signals in the direction of the reflected optical signals, thus taking advantage of the excellent electro-optic properties of lithium niobate,” in which voltage can be applied to change the properties of optical signals, including speed and color. “We constructed a device that lets light emitted by the laser propagate unaltered, while the reflected light that travels back towards the laser changes its color and gets re-routed away,” said Lončar, Tiantsai Lin Professor of Electrical Engineering at SEAS. Their findings are reported in Nature Photonics. Now, a team of researchers led by electrical engineer Marko Lončar at SEAS has developed a method for building a highly efficient integrated isolator that’s seamlessly incorporated into an optical chip made of lithium niobate. But conventional isolators have been relatively bulky in size and require more than one type of material to be joined together, creating a roadblock to achieving enhanced performance. Isolators also help cut down on signal noise by preventing light from bouncing around unfettered. To protect the lasers from damage and instability, these systems also require isolators, components that prevent light from traveling in undesired directions. Paulson School of Engineering and Applied Sciences (SEAS) could drastically improve optical systems for many practical applications.Īll optical systems - used for telecommunications, microscopy, imaging, quantum photonics, and more - rely on a laser to generate photons and beams of light. ![]() (Image: Loncar Lab/Harvard SEAS)Īn optical isolator developed at the Harvard John A. Paulson School of Engineering and Applied Sciences, Cambridge, MA Optical micrograph of the electro-optic isolator chip on thin-film lithium niobate, comprising four devices with varying modulation length. ![]()
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