Power/Performance Bits: Oct. 29

Chip scanning; integrated SiC photonic chip; thinner camera lens.


Chip scanning
Researchers at the University of Southern California and the Paul Scherer Institut in Switzerland developed an x-ray technique to non-destructively scan chips to make sure they conform to specifications. Such a system could be used to identify manufacturing defects or malicious alterations, the team said.

Called ptychographic x-ray laminography, the technique utilizes x-rays from a synchrotron to illuminate a small region of a rotating chip at an angle of 61 degrees (with respect to the normal of the chip plane). The resulting diffraction patterns are measured with a photon-counting detector array. The data are then used to generate high-resolution slice images of the chip, from which 3D renderings are created.

The 3D image can then be compared with the original design to make sure it was manufactured correctly and meets specifications. The researchers noted that signature features on chips make it possible to tell how and where they were manufactured.

The process would also allow for non-destructive reverse engineering of circuit designs, said Anthony F. J. Levi, Department Chair of Electrical Engineering-Electrophysics at USC. “The majority of a chip’s intelligence is how it is wired. It is like the connectome of a brain. By viewing a chip in detail, you can non-destructively figure out what it does. With this technology, hiding intellectual property in a chip is over.”

It could also lead to a certification process to insure integrity of chips, Levi said. Next, the team plans to continue improving the imaging speed and resolution as well as improving x-ray microscope performance.

Integrated SiC photonic chip
Researchers at the Georgia Institute of Technology created a silicon carbide (SiC) photonic integrated chip that can be thermally tuned by applying an electric signal. This tuneability could lead to reconfigurable devices like phase-shifters and tunable optical couplers.

“Devices such as the one we demonstrate in this work can be used as building-blocks for next generation quantum information processing devices and to create biocompatible sensors and probes,” said Xi Wu, a Ph.D. student at Georgia Tech.

Previously, the team created a platform called crystalline SiC-on-insulator they say overcomes some of the fragility and other drawbacks of previously reported SiC platforms while providing an easy and reliable route for integration with electronic devices.

“The SiC-on-insulator platform our group pioneered is similar to the silicon-on-insulator technology widely used in semiconductor industry for a variety of applications,” said Tianren Fan, currently a Ph.D. candidate at Georgia Tech.

“It enables wafer-level manufacturing of SiC devices, paving the way toward commercialization of integrated photonic quantum information processing solutions based on SiC,” added Ali A. Eftekhar, a research engineer at Georgia Tech.

The team fabricated tiny ring-shaped optical cavities called microring resonators using the crystalline SiC-on-insulator technology. In each resonator, light at certain wavelengths, called its resonance wavelengths, traveling around the ring will build up strength through constructive interference. The resonator then can be used to control the amplitude and phase of the light in a waveguide coupled to it. To create a tunable resonator with a high degree of control, the researchers fabricated electric heaters on top of the microrings. When an electric current is applied to the integrated microheater, it locally increases the temperature of the SiC microring and thus changes its resonant wavelengths thanks to the thermo-optic effect.

“Combined with other unique features of our crystalline SiC-on-insulator platform, these high-quality devices have the basic requirements for enabling new chip-scale devices that operate in a wide range of wavelengths,” said Ali Adibi, professor of electronics at Georgia Tech. “This chip-scale tunability is essential for performing quantum operations necessary for quantum computing and communication. In addition, because of the biocompatibility of SiC, it could be very useful for in vivo biosensing.”

Additionally, the device can be manufactured with existing foundry processes. The team is working to build elements with the crystalline SiC-on-insulator platform for quantum photonic integrated circuits, including on-chip pump lasers, single photon sources and single photon detectors that could be used with the tunable microring resonator to create a fully functional chip for advanced optical quantum computing.

Thinner camera lens
Engineers at the University of Utah developed a new type of optical lens that is thinner and lighter than conventional lenses used in smartphone cameras.

The new lens is only a few microns thick, but the researchers say it provides the performance of traditional millimeter-thick lenses. Instead of a conventional curved lens, the new lens is comprised of many microstructures, each bending the light in the correct direction at the sensor. The team developed a fabrication process with a new type of polymer along with algorithms that can calculate the geometry of these microstructures.

A flat lens developed by researchers at the University of Utah that is much thinner and lighter than a conventional lens that could produce lighter cameras for drones and night-vision cameras for soldiers. (Photo credit: Dan Hixson/University of Utah College of Engineering)

“Our lens is a hundred times lighter and a thousand times thinner, but the performance can be as good as conventional lenses,” said Rajesh Menon, an electrical and computer engineering associate professor at Utah. “You can think of these microstructures as very small pixels of a lens. They’re not a lens by themselves but all working together to act as a lens.”

Menon said this new lens could also be cheaper to manufacture because the design allows them to create them out of plastic instead of glass.

As a bonus, the lens can be used in thermal imaging for night vision and cameras. The team said the lighter lens would be useful for military drones to fly longer for night missions or to map forest fires or look for victims of natural disasters.

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