Browsing by Author "Bur, James A."

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An In-situ and Direct Confirmation of Super-Planckian Thermal Radiation Emitted From a Metallic Photonic-Crystal at Optical Wavelengths
(2020-03-23)
Lin, Shawn-Yu
;
Hsieh, Mei-Li
;
John, Sajeev
;
Frey, B.
;
Bur, James A.
Planck's law predicts the distribution of radiation energy, color and intensity, emitted from a hot object at thermal equilibrium. The Law also sets the upper limit of radiation intensity, the blackbody limit. Recent experiments reveal that micro-structured tungsten can exhibit significant deviation from the blackbody spectrum. However, whether thermal radiation with weak non-equilibrium pumping can exceed the blackbody limit in the far field remains un-answered experimentally. Here, we compare thermal radiation from a micro-cavity/tungsten photonic crystal (W-PC) and a blackbody, which are both measured from the same sample and also in-situ. We show that thermal radiation can exceed the blackbody limit by >8 times at lambda = 1.7 mu m resonant wavelength in the far-field. Our observation is consistent with a recent calculation by Wang and John performed for a 2D W-PC filament. This finding is attributed to non-equilibrium excitation of localized surface plasmon resonances coupled to nonlinear oscillators and the propagation of the electromagnetic waves through non-linear Bloch waves of the W-PC structure. This discovery could help create super-intense narrow band thermal light sources and even an infrared emitter with a laser-like input-output characteristic.
Experimental observation of anomalous thermal radiation from a three-dimensional metallic photonic crystal
(2015-06-12)
Hsieh, Mei-Li
;
Lin, Shawn-Yu
;
Bur, James A.
;
Shenoi, Rajeev
;
光電工程學系
We report some striking results on thermal radiation properties of a resonantly coupled cavity photonic crystal (PhC) at elevated temperatures (T = 400-900 K). We experimentally found that at resonant wavelengths, lambda = 1.1, 1.64, 2.85 mu m, the PhC emission is spectrally selective, quasi-coherent, directional, and shows significant deviation from Planck\'s blackbody law at equilibrium. The presence of non-equilibrium effects, driven by strong thermal excitation and cavity resonance, may be the major cause for our experimental observation.
Probing the intrinsic optical Bloch-mode emission from a 3D photonic crystal
(2016-10-14)
Hsieh, Mei-Li
;
Bur, James A.
;
Du, Qingguo
;
John, Sajeev
;
Lin, Shawn-Yu
We report experimental observation of intrinsic Bloch-mode emission from a 3D tungsten photonic crystal at low thermal excitation. After the successful removal of conventional metallic emission (normal emission), it is possible to make an accurate comparison of the Bloch-mode and the normal emission. For all biases, we found that the emission intensity of the Bloch-mode is higher than that of the normal emission. The Bloch-mode emission also exhibits a slower dependence on (h(omega)/k(b)T) than that of the normal emission. The observed higher emission intensity and a different T-dependence is attributed to Bloch-mode assisted emission where emitters have been located into a medium having local density of states different than the isotropic case. Furthermore, our finite-difference time-domain (FDTD) simulation shows the presence of localized spots at metal-air boundaries and corners, having intense electric field. The enhanced plasmonic field and local non-equilibrium could induce a strong thermally stimulated emission and may be the cause of our unusual observation.
Review on Recent Progress of Three-dimensional Optical Photonic Crystal
(2014)
Hsieh, Mei-Li
;
Kuang, Ping
;
Bur, James A.
;
John, Sajeev
;
Lin, Shawn-Yu
Over the past two decades, the field of photonic-crystals has become one of the most influential realms of contemporary optics. In this paper; we will review two recent experimental progresses in three-dimensional photonic-crystal operating in optical wavelengths. The first is the observation of anomalous light-refraction, an acutely negative refraction, in a 3D photonic-crystal for light trapping, guiding and near-unity absorption. The second is the observation of quasi-coherent thermal emission from an all-metallic 3D photonic-crystal at elevated temperatures.