Ultra-thin perfect absorber employing a tunable phase change material

New device hides, on cue, from infrared cameras

November 26, 2012

Tunable material developed at Harvard boasts nearly 100% absorption on demand

Cambridge, Mass. - November 26, 2012 - Now you see it, now you don’t.

A new device invented at the Harvard School of Engineering and Applied Sciences (SEAS) can absorb 99.75% of infrared light that shines on it. When activated, it appears black to infrared cameras.

Composed of just a 180-nanometer-thick layer of vanadium dioxide (VO₂) on top of a sheet of sapphire, the device reacts to temperature changes by reflecting dramatically more or less infrared light.

Announced today in the journal Applied Physics Letters, and featured on its cover, this perfect absorber is ultrathin, tunable, and exceptionally well suited for use in a range of infrared optical devices.

Perfect absorbers have been created many times before, but not with such versatile properties. In a Fabry-Pérot cavity, for instance, two mirrors sandwich an absorbing material, and light simply reflects light back and forth until it's mostly all gone. Other devices incorporate surfaces with nanoscale metallic patterns that trap and eventually absorb the light.

Reflectivity of Mineral Powders

From the Website of Ocean Optics, an applications note for their Jaz Spectrometer

It begins:

"Reflectance spectroscopy is a versatile technique than can be used to identify and characterize a range of powdered samples including mineral powders, grains in lunar samples, mining samples, natural deposits, soils and sediment core samples. In this application note, reflectance spectroscopy is used to characterize mineral powder samples.

"The Jaz spectrometer was used to acquire reflectance spectra for pure samples and powder mixtures to assess the power of reflectance spectroscopy to characterize mineral powder samples."

Figure-3-Experiment-Setup.jpg from the Ocean Optics Blog

Experimental verification of a multiband system for non-contact temperature measurements

Proc. SPIE 5258, 198 (2003); doi:10.1117/12.544574
Conference Title: IV Workshop on Atomic and Molecular Physics
Conference Chair: Jozef Heldt

Abstract

Adam Mazikowski and Marcin Gnyba
Gdansk Univ. of Technology (Poland)
Recent studies about non-contact temperature measurement concern passive multiband radiometric systems. These systems give a potential possibility of accurate temperature measurements in case of unknown and wavelength depended emissivity of the examined object. Modeling of such systems, what is usually the first stage of system designing, requires acceptance of several simplifications and approximations. In this paper an experimental verification of modeling result is performed. Based on developed experimental setup some tests are performed. It allows us to determine some systems parameters and whole system estimation.

Publications of Robert O. Knuteson

Reference online: http://library.ssec.wisc.edu/publications/resultOnly.php?authorText=Knuteson,%20Robert%20O.&numOfRecs=25&currPage=1.

Sample Entries of the 38 records online at the University of Wisconsin Library:

1. Seemann, Suzanne W.; Borbas, Eva E.; Knuteson, Robert O.; Stephenson, Gordon R. and Huang, Hung-Lung. Development of a global infrared land surface emissivity database for application to clear sky sounding retrievals from multispectral satellite radiance measurements. Reprint # Journal of Applied Meteorology and Climatology, Volume 47, Issue 1, 2008, pp.108-123. Call Number: Reprint # 5663

2. Tobin, David C.; Antonelli, Paolo; Revercomb, Henry E.; Dutcher, Steven; Turner, David D.; Taylor, Joe K.; Knuteson, Robert O. and Vinson, Kenneth. Hyperspectral data noise characterization using principle component analysis: Application to the atmospheric infrared sounder. Reprint # Journal of Applied Remote Sensing, Volume 1, 2007, Doi:10.1117/1.2757707. Call Number: Reprint # 5392...

Noncontact multiband emissivity measurements

Proc. SPIE 5124, 240 (2003); doi:10.1117/12.517121
Conference Title: Optoelectronic and Electronic Sensors V
Conference Chairs: Wlodzimierz Kalita

Abstract

Adam Mazikowski
Gdansk Univ. of Technology (Poland)

During last decade an increasing interest in passive multiband systems for temperature measurement was noted. However, recent studies showed that multiband systems are capable of producing accurate results of non-contact temperature measurement only in limited number of applications. Available literature about passive multiband systems concentrated exclusively on problem of temperature measurements too. A model of a passive multiband system for non-contact emissivity measurement has been developed and presented in this paper. Simulations carried out using this model showed that it is possible to achieve reasonable accuracy of emissivity measurements with passive multiband systems and these systems can be considered as an attractive solution for emissivity measurements in industrial conditions.