New sensors to detect microscopic fluctuations can now operate at microchip level

Credit: The Hebrew University of Jerusalem.

Very detailed and accurate readings of the properties and environmental conditions of microchips are nowadays possible and are standard practice when analysing and designing chip systems and operations. This is done on the nano-level. Plasmonics and photonics devices known as resonant cavities are used, which can measure precise changes in things like temperature, movement and index of refraction. They render small changes in refraction they detect into quantifiable changes in spectrum. Resonant cavities are capable of rendering these small changes because of their properties as transductors, meaning they convert one type of energy into another. These devices are used in many industries and for many tasks, from medicine to industrial engineering and for nuclear and molecule level measurement of electromagnetic radiation. On the level of microchips, a special kind of resonant cavity is needed that is very compact, easy to prototype and manufacture, accurate and able to be optimised for different uses. MRRs (microring and microdisk resonators) meet these requirements and are extensively used.

Existing devices for this purpose have led to breakthroughs in a number of applications. That being said, it has been a challenge to make the devices more compact and hence more usable. These optical sensors measure complex changes in their composition which is dependent on their environment (such factors as different surrounding material and conditions), so it’s difficult to construct a very small scale device due to how complicated their functioning is.

This is now possible thanks to research at the Hebrew University of Jerusalem. Their innovation involves combining two such devices (microring in particular). One of the devices does the measuring, which is then compared with the state of the other. This allows for the factoring out of certain influencing factors. The devices are placed one atop the other.

One of the researchers leading the project was Professor Uriel Levy. He said about the research: “Here we demonstrate a record-high sensing precision on a device with a small footprint that can be integrated with standard CMOS technology, paving the way for even more exciting measurements such as single particle detection and high precision chip scale thermometry,”. Prof. Levy directs the Harvey M. Krueger Family Center for Nanoscience and Nanotechnology at the university. He is part of the faculty of the Department of Applied Physics in the Rachel and Selim Benin School of Computer Science and Engineering

The development was possible thanks to new inventions in the fields of measuring reference, and an innovation in servo-loop locking, This allows transfer of energy measurements of light to be rendered as radio frequencies, and thus enabled the team to use standard radio frequency tools like spectrum analysers, atomic standards and frequency counters to measure the effectiveness of their innovation.

The results of their findings, which used microring devices made at the Center for Nanoscience and Nanotechnology at the university, were peer reviewed and released in the science publication Optica. The Optical Society publishes the journal.

More information can be found at: The Hebrew University of Jerusalem.

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