Optical sensing is one of the most important applications of light science. It plays crucial roles in astronomy, environmental science, industry and medical diagnoses.
Despite the variety of schemes used for optical sensing, they all share the same principle: The quantity to be measured must leave a "fingerprint" on the optical response of the system. The fingerprint can be its transmission, reflection or absorption. The stronger these effects are, the stronger the response of the system.
While this works well at the macroscopic level, measuring tiny, microscopic quantities that induce weak response is a challenging task. Researchers have developed techniques to overcome this difficulty and improve the sensitivity of their devices. Some of these techniques, which rely on complex quantum optics concepts and implementations, have indeed proved useful, such as in sensing gravitational waves in the LIGO project. Others, which are based on trapping light in tiny boxes called optical resonators, have succeeded in detecting micro-particles and relatively large biological components.
Nonetheless, the ability to detect small nano-particles and eventually single molecules remains a challenge. Current attempts focus on a special type of light trapping devices called microring or microtoroid resonators -- these enhance the interaction between light and the molecule to be detected. The sensitivity of these devices, however, is limited by their fundamental physics.
In their article "Sensing with Exceptional Surfaces in Order to Combine Sensitivity with Robustness" published in Physical Review Letters (DOI: https:/
Exceptional Points for Exceptionally Sensitive Detection
In order to understand the meaning of exceptional points, consider an imaginary violin with only two strings. In general, such a violin can produce just two different tones -- a situation that corresponds to a conventional optical resonator. If the vibration of one string can alter the vibration of the other string in a way that the sound and the elastic oscillations create only one tone and one collective string motion, the system has an exceptional point.
A physical system that exhibits an exceptional point is very fragile. In other words, any small perturbation will dramatically alter its behavior. The feature makes the system highly sensitive to tiny signals.
"Despite this promise, the same enhanced sensitivity of exceptional point-based sensors is also their Achilles heel: These devices are very sensitive to unavoidable fabrication errors and undesired environmental variations," said Ramy El-Ganainy, associate professor of physics, adding that the sensitivity necessitated clever tuning tricks in previous experimental demonstrations.
"Our current proposal alleviates most of these problems by introducing a new system that has the same enhanced sensitivity reported in previous work, while at the same time robust against the majority of the uncontrivable experimental uncertainty," said Qi Zhong, lead author on the paper and a graduate student who is currently working towards his doctorate degree at Michigan Tech.
Though the design of microring sensors continues to be refined, researchers are hopeful that by improving the devices, seemingly tiny optical observations will have large effects.
Kelley Christensen | EurekAlert!
Appreciating the classical elegance of time crystals
20.09.2019 | ETH Zurich Department of Physics
'Nanochains' could increase battery capacity, cut charging time
20.09.2019 | Purdue University
How long the battery of your phone or computer lasts depends on how many lithium ions can be stored in the battery's negative electrode material. If the battery runs out of these ions, it can't generate an electrical current to run a device and ultimately fails.
Materials with a higher lithium ion storage capacity are either too heavy or the wrong shape to replace graphite, the electrode material currently used in...
To process information, photons must interact. However, these tiny packets of light want nothing to do with each other, each passing by without altering the...
Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.
The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.
At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.
Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...
Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....
19.09.2019 | Event News
10.09.2019 | Event News
04.09.2019 | Event News
20.09.2019 | Life Sciences
20.09.2019 | Life Sciences
20.09.2019 | Life Sciences