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"Blackbody"
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On the trail of blackbody radiation : Max Planck and the physics of his era
\"A concise historical study of On the trail of blackbody radiation, intended to provide insight into the process of scientific discovery\"-- Provided by publisher.
Book
Effects of Solar Intrusion on the Calibration of the Metop-C Advanced Microwave Sounding Unit-A2 Channels
This study presents our first discovery about two abnormal problems in the blackbody calibration target associated with the antenna unit A2 in the Metop-C AMSU-A instrument. The problems include the anomalous patterns in both blackbody kinetic temperature Tw and radiative temperature (measured in warm count or Cw), and the time lag between orbital cycles of Tw and Cw. This study further determines solar intrusion as the root cause of the anomalous pattern problem. According to our analysis, solar illumination is constantly observed during each orbit near the satellite terminator, causing anomalous changes in Cw and Tw, characterized by sudden and abnormal increases typically for more than 16 min. The resultant maximum antenna temperature errors due to abnormal increases in Cw are approximately in the range from 0.15 K to 0.25 K, while the maximum errors due to the abnormal increase in Tw are in the range from 0.04 K to 0.07 K, varying with orbit, season, and channel. The time shift feature is characterized with a changeable time lag with the season in the Tw orbital cycle in comparison with the Cw cycle. The longest time lag up to about 18 min occurs in summer through early fall, while the time lag can be decreased down to about 9 min in winter through early spring. Hence, this study underscores the imperative need for future research to rectify radiance errors and reconstruct a more accurate long-term Metop-C AMSU-A radiance data set for channels 1 and 2, crucial for climate studies.
Journal Article
Hundred-fold enhancement in far-field radiative heat transfer over the blackbody limit
Radiative heat transfer (RHT) has a central role in entropy generation and energy transfer at length scales ranging from nanometres to light years
1
. The blackbody limit
2
, as established in Max Planck’s theory of RHT, provides a convenient metric for quantifying rates of RHT because it represents the maximum possible rate of RHT between macroscopic objects in the far field—that is, at separations greater than Wien’s wavelength
3
. Recent experimental work has verified the feasibility of overcoming the blackbody limit in the near field
4
–
7
, but heat-transfer rates exceeding the blackbody limit have not previously been demonstrated in the far field. Here we use custom-fabricated calorimetric nanostructures with embedded thermometers to show that RHT between planar membranes with sub-wavelength dimensions can exceed the blackbody limit in the far field by more than two orders of magnitude. The heat-transfer rates that we observe are in good agreement with calculations based on fluctuational electrodynamics. These findings may be directly relevant to various fields, such as energy conversion, atmospheric sciences and astrophysics, in which RHT is important.
Rates of radiative heat transfer between sub-wavelength planar membranes are experimentally and theoretically shown to exceed the blackbody limit in the far field by more than two orders of magnitude.
Journal Article
A wavelength-scale black phosphorus spectrometer
On-chip spectrometers with compact footprints are being extensively investigated owing to their promising future in critical applications such as sensing, surveillance and spectral imaging. Most existing miniaturized spectrometers use large arrays of photodetection elements to capture different spectral components of incident light, from which its spectrum is reconstructed. Here, we demonstrate a mid-infrared spectrometer in the 2–9 µm spectral range, utilizing a single tunable black phosphorus photodetector with an active area footprint of only 9 × 16 µm2, along with a unique spectral learning procedure. Such a single-detector spectrometer has a compact size at the scale of the operational wavelength. Leveraging the wavelength and bias-dependent responsivity matrix learned from the spectra of a tunable blackbody source, we reconstruct unknown spectra from their corresponding photoresponse vectors. Enabled by the strong Stark effect and the tunable light–matter interactions in black phosphorus, our single-detector spectrometer shows remarkable potential in the reconstruction of the spectra of both monochromatic and broadband light. Furthermore, its ultracompact structure that is free from bulky interferometers and gratings, together with its electrically reconfigurable nature, may open up pathways towards on-chip mid-infrared spectroscopy and spectral imaging.A single-photodetector spectrometer based on black phosphorus is demonstrated in the wavelength range from 2 to 9 μm. The footprint is 9 × 16 μm2. The spectrometer is free from bulky interferometers and gratings, and is electrically reconfigurable.
Journal Article
Radiative cooling and indoor light management enabled by a transparent and self-cleaning polymer-based metamaterial
Transparent roofs and walls offer a compelling solution for harnessing natural light. However, traditional glass roofs and walls face challenges such as glare, privacy concerns, and overheating issues. In this study, we present a polymer-based micro-photonic multi-functional metamaterial. The metamaterial diffuses 73% of incident sunlight, creating a more comfortable and private indoor environment. The visible spectral transmittance of the metamaterial (95%) surpasses that of traditional glass (91%). Furthermore, the metamaterial is estimated to enhance photosynthesis efficiency by ~9% compared to glass roofs. With a high emissivity (~0.98) close to that of a mid-infrared black body, the metamaterial is estimated to have a cooling capacity of ~97 W/m
2
at ambient temperature. The metamaterial was about 6 °C cooler than the ambient temperature in humid Karlsruhe. The metamaterial exhibits superhydrophobic performance with a contact angle of 152°, significantly higher than that of glass (26°), thus potentially having excellent self-cleaning properties.
Transparent roofs offer a solution for harnessing natural light in sustainable buildings. Here, authors demonstrate a polymer-based metamaterial with micro-pyramid surface structures that diffuses sunlight while offering passive cooling and self-cleaning properties.
Journal Article
Cryogenic optical lattice clocks
A pair of
87
Sr optical lattice clocks with a statistical agreement of 2 × 10
−18
within 6,000 s has been developed. To this end, the behaviour of the blackbody radiation—a major perturbation for optical lattice clocks—was directly investigated.
The accuracy of atomic clocks relies on the superb reproducibility of atomic spectroscopy, which is accomplished by careful control and the elimination of environmental perturbations on atoms. To date, individual atomic clocks have achieved a 10
−18
level of total uncertainties
1
,
2
, but a two-clock comparison at the 10
−18
level has yet to be demonstrated. Here, we demonstrate optical lattice clocks with
87
Sr atoms interrogated in a cryogenic environment to address the blackbody radiation-induced frequency shift
3
, which remains the primary source of systematic uncertainty
2
,
4
,
5
,
6
and has initiated vigorous theoretical
7
,
8
and experimental
9
,
10
investigations. The systematic uncertainty for the cryogenic clock is evaluated to be 7.2 × 10
−18
, which is expedited by operating two such cryo-clocks synchronously
11
,
12
. After 11 measurements performed over a month, statistical agreement between the two cryo-clocks reached 2.0 × 10
−18
. Such clocks' reproducibility is a major step towards developing accurate clocks at the low 10
−18
level, and is directly applicable as a means for relativistic geodesy
13
.
Journal Article
Early spectra of the gravitational wave source GW170817
On 17 August 2017, Swope Supernova Survey 2017a (SSS17a) was discovered as the optical counterpart of the binary neutron star gravitational wave event GW170817. We report time-series spectroscopy of SSS17a from 11.75 hours until 8.5 days after the merger. Over the first hour of observations, the ejecta rapidly expanded and cooled. Applying blackbody fits to the spectra, we measured the photosphere cooling from
11,000
−
900
+
3400
to
9300
−
300
+
300
kelvin, and determined a photospheric velocity of roughly 30% of the speed of light. The spectra of SSS17a began displaying broad features after 1.46 days and evolved qualitatively over each subsequent day, with distinct blue (early-time) and red (late-time) components. The late-time component is consistent with theoretical models of r-process–enriched neutron star ejecta, whereas the blue component requires high-velocity, lanthanide-free material.
Journal Article
Optical fiber sensors for high-temperature monitoring: a review
High-temperature measurements above 1000 °C are critical in harsh environments such as aerospace, metallurgy, fossil fuel, and power production. Fiber-optic high-temperature sensors are gradually replacing traditional electronic sensors due to their small size, resistance to electromagnetic interference, remote detection, multiplexing, and distributed measurement advantages. This paper reviews the sensing principle, structural design, and temperature measurement performance of fiber-optic high-temperature sensors, as well as recent significant progress in the transition of sensing solutions from glass to crystal fiber. Finally, future prospects and challenges in developing fiber-optic high-temperature sensors are also discussed.
Journal Article
A bright γ-ray flare interpreted as a giant magnetar flare in NGC 253
Soft γ-ray repeaters exhibit bursting emission in hard X-rays and soft γ-rays. During the active phase, they emit random short (milliseconds to several seconds long), hard-X-ray bursts, with peak luminosities
1
of 10
36
to 10
43
erg per second. Occasionally, a giant flare with an energy of around 10
44
to 10
46
erg is emitted
2
. These phenomena are thought to arise from neutron stars with extremely high magnetic fields (10
14
to 10
15
gauss), called magnetars
1
,
3
,
4
. A portion of the second-long initial pulse of a giant flare in some respects mimics short γ-ray bursts
5
,
6
, which have recently been identified as resulting from the merger of two neutron stars accompanied by gravitational-wave emission
7
. Two γ-ray bursts, GRB 051103 and GRB 070201, have been associated with giant flares
2
,
8
–
11
. Here we report observations of the γ-ray burst GRB 200415A, which we localized to a 20-square-arcmin region of the starburst galaxy NGC 253, located about 3.5 million parsecs away. The burst had a sharp, millisecond-scale hard spectrum in the initial pulse, which was followed by steady fading and softening over 0.2 seconds. The energy released (roughly 1.3 × 10
46
erg) is similar to that of the superflare
5
,
12
,
13
from the Galactic soft γ-ray repeater SGR 1806−20 (roughly 2.3 × 10
46
erg). We argue that GRB 200415A is a giant flare from a magnetar in NGC 253.
The γ-ray burst GRB 200415A is probably a giant flare emitted from a magnetar in the nearby starburst galaxy NGC 253.
Journal Article