Drastic phase changes in topologically engineered planar absorbers improve sensitivity of optical sensors

January 18, 2018, Massachusetts Institute of Technology
Left: a planar absorber topologically engineered to support an interfacial Tamm optical state. Right: Near-perfect absorptance at the Tamm resonance translates into sharp variation of the optical phase, which provides a mechanism of high-sensitivity singular-phase optical sensing. Credit: Massachusetts Institute of Technology

Non-invasive optical temperature sensing is essential for remote monitoring of fabrication processes, in situations where the sample needs to be insulated from the environment, at extreme or rapidly changing temperatures, and in the presence of strong and varying magnetic fields. Optical temperature sensors measure frequency shifts of optical resonances and often require long optical paths to compensate for very small thermo-optical coefficients of materials.

However, a phase of light is a cyclic variable, which is undefined at the point of complete destructive interference, and varies rapidly in the vicinity of this point. For example, a phase shift of the plane wave reflected from a planar interface exhibits singular behavior at frequencies where the surface reflectance vanishes. Narrow asymmetric spectral features in the sensor phase response near such singular points are very sensitive to any environmental changes and can be used to improve the sensitivity of remote sensors with optical transduction.

Plasmonic metasurfaces can be designed to achieve the singular-phase condition, yet this typically requires complex electromagnetic design and low-throughput fabrication techniques such as electron beam lithography. In a new work, an international team led by an MIT researcher Dr. Svetlana Boriskina developed a simple and robust planar singular-phase sensing platform for remote temperature detection, which does not require nano-patterning and exhibits singular-phase behavior due to the excitation of topologically protected Tamm surface states.

The researchers engineered Tamm states on planar material interfaces between metal and dielectric thin films by using the boundary-bulk correspondence principle adopted from the physics of topological materials and the conjugate impedance matching approach borrowed from the antenna theory. They demonstrated singular-phase temperature detection with an over an order of magnitude improvement in sensor sensitivity and over two orders of magnitude improvement in the figure of merit over the standard approach of measuring shifts of resonant features in the reflectance spectra of the same sensor.

Planar structures that support Tamm interfacial states can be fabricated by using a variety of materials, including those compatible with standard complementary metal oxide semiconductor (CMOS) technologies. The resonant wavelengths of Tamm sensors are highly tunable, and do not directly depend on the plasma frequency of the absorber material. The sensors are amenable to fast and large-scale fabrication by either sputtering of vapor deposition techniques.

Unlike nano-patterned plasmonic sensors, planar Tamm detectors can be used in harsh environmental conditions, including corrosive atmosphere and high temperatures, which can cause severe degradation of nanostructured surface texture. Although the developed Tamm absorbers were only characterized as , they offer a simple, sensitive and tunable platform for a wide variety of sensing applications including monitoring surface bio/chemical binding events and environmental sensing.

The results of this work are reported in the ACS Photonics paper "Topological engineering of interfacial optical Tamm states for highly sensitive near-singular-phase optical detection."

Explore further: Optical fingerprint can reveal pollutants in the air

More information: Yoichiro Tsurimaki et al. Topological Engineering of Interfacial Optical Tamm States for Highly Sensitive Near-Singular-Phase Optical Detection, ACS Photonics (2018). DOI: 10.1021/acsphotonics.7b01176

Related Stories

Optical fingerprint can reveal pollutants in the air

March 15, 2017

More efficient sensors are needed to be able to detect environmental pollution. Researchers at Chalmers University of Technology have proposed a new, sophisticated method of detecting molecules with sensors based on ultra-thin ...

Optical surface states in magnetophotonic crystals

October 26, 2010

Using state of the art microfabrication technology to create periodic structures with high accuracy, Dr Baryshev and colleagues at the Toyohashi University of Technology, Japan, report the existence of so-called optical surface ...

New capability takes sensor fabrication to a new level

June 30, 2015

Operators must continually monitor conditions in power plants to assure they are operating safely and efficiently. Researchers on the Sensors and Controls Team at DOE's National Energy Technology Laboratory can now fabricate ...

Recommended for you

Compelling evidence for small drops of perfect fluid

December 10, 2018

Nuclear physicists analyzing data from the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC)—a U.S. Department of Energy (DOE) Office of Science user facility for nuclear physics research at Brookhaven National ...

Supercomputers without waste heat

December 10, 2018

Generally speaking, magnetism and the lossless flow of electrical current ("superconductivity") are competing phenomena that cannot coexist in the same sample. However, for building supercomputers, synergetically combining ...

Engineers invent groundbreaking spin-based memory device

December 7, 2018

A team of international researchers led by engineers from the National University of Singapore (NUS) have invented a new magnetic device to manipulate digital information 20 times more efficiently and with 10 times more stability ...

Multichannel vectorial holographic display and encryption

December 7, 2018

Holography is a powerful tool that can reconstruct wavefronts of light and combine the fundamental wave properties of amplitude, phase, polarization, wave vector and frequency. Smart multiplexing techniques (multiple signal ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.