Multivalent Acceptor-Doped Germanium Lasers: a solid-state tunable source from 75 to 300 μm

1997 ◽  
Vol 484 ◽  
Author(s):  
D. R. Chamberlin ◽  
O. D. Dubon ◽  
E. Bründermann ◽  
E. E. Haller ◽  
L. A. Reichertzl ◽  
...  
Keyword(s):  
Electric Fields ◽  
Duty Cycle ◽  
Population Inversion ◽  
Continuous Wave ◽  
Laser Action ◽  
Far Infrared ◽  
Uniaxial Stress ◽  
Power Input ◽  
Infrared Light ◽  
Order Of Magnitude

AbstractWe report on the performance of far-infrared hole inversion lasers made from germanium doped with the multivalent acceptors beryllium and copper. Commonly used hole inversion lasers are made from Czochralski-grown Ga-doped Ge single crystals and show emission from 75 to 125 and 170 to 300 μm. The emission gap between 125 and 170 μm, originating from absorption of the far-infrared light due to internal hole transitions in the neutral Ga acceptor, is absent in the new Be and Cu-doped lasers. We also find a mechanism for inversion depopulation through neutral Ga which hinders lasing at low electric fields. This same mechanism is shown to cause population inversion in the Be-doped laser and allows lasing at lower fields. This reduces the power input into the germanium crystal and has allowed us to increase the duty cycle up to 2.5% which is one order of magnitude higher than the maximum duty cycle reported for Ga-doped Ge lasers. These new lasers may offer an opportunity for achieving continuous-wave operation.In addition we have performed preliminary studies on the effect of uniaxial stress on the lasing in these new materials. We demonstrate that small uniaxial stress increases laser action in Ge:Cu. We propose that this is due to an increased population inversion because under these conditions two separate mechanisms cause heavy holes to enter the light hole band.

Pulsed Plasma Polymerizations: Film Chemistry Control and Applications

1998 ◽  
Vol 544 ◽  
Author(s):  
Yuliang WU ◽  
Licheng M. Han ◽  
Brett E. Thomes ◽  
Haibo Qiu ◽  
Charles R. Savage ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Low Power ◽  
Special Reference ◽  
Duty Cycle ◽  
Continuous Wave ◽  
Film Formation ◽  
Power Input ◽  
Pulsed Plasma ◽  
Plasma Technique ◽  
Power Inputs

AbstractFilm chemistry control issues, as well as key properties of polymers synthesized under pulsed plasma conditions, are discussed. Distinctions between pulsed and continuous wave plasmas are examined, particularly as they relate to differences in the energy efficiency of film formation rates and to the range of available power inputs. Film stabilities, with special reference to polymers formed under very low power input conditions, are considered. Finally, selected applications involving use of the inherently high film chemistry controllability made available by the variable duty cycle pulsed plasma technique are described.

scholarly journals Thermal non-line-of-sight imaging from specular and diffuse reflections

2019 ◽  
Vol 11 (1) ◽  
Author(s):  
Masaki Kaga ◽  
Takahiro Kushida ◽  
Tsuyoshi Takatani ◽  
Kenichiro Tanaka ◽  
Takuya Funatomi ◽  
...  
Keyword(s):  
Angular Distribution ◽  
Heat Source ◽  
Real World ◽  
Diffuse Reflection ◽  
Far Infrared ◽  
Infrared Light ◽  
Line Of Sight ◽  
Thermal Camera ◽  
Reflection Component ◽  
Non Line Of Sight

Abstract This paper presents a non-line-of-sight technique to estimate the position and temperature of an occluded object from a camera via reflection on a wall. Because objects with heat emit far infrared light with respect to their temperature, positions and temperatures are estimated from reflections on a wall. A key idea is that light paths from a hidden object to the camera depend on the position of the hidden object. The position of the object is recovered from the angular distribution of specular and diffuse reflection component, and the temperature of the heat source is recovered from the estimated position and the intensity of reflection. The effectiveness of our method is evaluated by conducting real-world experiments, showing that the position and the temperature of the hidden object can be recovered from the reflection destination of the wall by using a conventional thermal camera.

scholarly journals Large-area printing of ferroelectric surface and super-domains for efficient solar water splitting

2020 ◽  
Author(s):  
Yu Tian ◽  
Yaqing Wei ◽  
Minghui Pei ◽  
Rongrong Cao ◽  
Zhenao Gu ◽  
...  
Keyword(s):  
Water Splitting ◽  
Electric Fields ◽  
Electronic Structures ◽  
Active Sites ◽  
Large Area ◽  
Solar Water Splitting ◽  
High Efficient ◽  
Catalytic Sites ◽  
Order Of Magnitude ◽  
Magnitude Increase

Abstract Surface electronic structures of the photoelectrodes determine the activity and efficiency of the photoelectrochemical water splitting, but the controls of their surface structures and interfacial chemical reactions remain challenging. Here, we use ferroelectric BiFeO3 as a model system to demonstrate an efficient and controllable water splitting reaction by large-area constructing the hydroxyls-bonded surface. The up-shift of band edge positions at this surface enables and enhances the interfacial holes and electrons transfer through the hydroxyl-active-sites, leading to simultaneously enhanced oxygen and hydrogen evolutions. Furthermore, printing of ferroelectric super-domains with microscale checkboard up/down electric fields separates the distribution of reduction/oxidation catalytic sites, enhancing the charge separation and giving rise to an order of magnitude increase of the photocurrent. This large-area printable ferroelectric surface and super-domains offer an alternative platform for controllable and high-efficient photocatalysis.

scholarly journals Interferometric characterization of 160 fs far‐infrared light pulses

1991 ◽  
Vol 59 (8) ◽  
pp. 893-895 ◽  
Author(s):  
B. I. Greene ◽  
J. F. Federici ◽  
D. R. Dykaar ◽  
R. R. Jones ◽  
P. H. Bucksbaum
Keyword(s):  
Far Infrared ◽  
Infrared Light ◽  
Light Pulses

scholarly journals Megaparsec-scale structure around the protocluster core SPT2349–56 at z = 4.3

2020 ◽  
Vol 495 (3) ◽  
pp. 3124-3159 ◽  
Author(s):  
Ryley Hill ◽  
Scott Chapman ◽  
Douglas Scott ◽  
Yordanka Apostolovski ◽  
Manuel Aravena ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Far Infrared ◽  
Main Structure ◽  
Star Forming ◽  
Galaxy Groups ◽  
The Core ◽  
Order Of Magnitude ◽  
Number Counts ◽  
Limited Coverage

ABSTRACT We present an extensive ALMA spectroscopic follow-up programme of the $z\, {=}\, 4.3$ structure SPT2349–56, one of the most actively star-forming protocluster cores known, to identify additional members using their [C ii] 158 μm and CO(4–3) lines. In addition to robustly detecting the 14 previously published galaxies in this structure, we identify a further 15 associated galaxies at $z\, {=}\, 4.3$, resolving 55$\, {\pm }\,$5 per cent of the 870 μm flux density at 0.5 arcsec resolution compared to 21 arcsec single-dish data. These galaxies are distributed into a central core containing 23 galaxies extending out to 300 kpc in diameter, and a northern extension, offset from the core by 400 kpc, containing three galaxies. We discovered three additional galaxies in a red Herschel-SPIRE source 1.5 Mpc from the main structure, suggesting the existence of many other sources at the same redshift as SPT2349–56 that are not yet detected in the limited coverage of our data. An analysis of the velocity distribution of the central galaxies indicates that this region may be virialized with a mass of (9$\pm 5)\, {\times }\, 10^{12}$  M⊙, while the two offset galaxy groups are about 30 and 60 per cent less massive and show significant velocity offsets from the central group. We calculate the [C ii] and far-infrared number counts, and find evidence for a break in the [C ii] luminosity function. We estimate the average SFR density within the region of SPT2349–56 containing single-dish emission (a proper diameter of 720 kpc), assuming spherical symmetry, to be roughly 4$\, {\times }\, 10^4$ M⊙ yr−1 Mpc−3; this may be an order of magnitude greater than the most extreme examples seen in simulations.

scholarly journals N/O Abundances in Planetary Nebulae from Far-Infrared Line Observations

1989 ◽  
Vol 131 ◽  
pp. 214-214
Author(s):  
Harriet L. Dinerstein ◽  
Michael W. Werner
Keyword(s):  
Planetary Nebulae ◽  
Far Infrared ◽  
Optical Observations ◽  
Type I ◽  
Local Electron ◽  
Extreme Type ◽  
Order Of Magnitude ◽  
Progenitor Stars ◽  
Infrared Array ◽  
Atomic Parameters

Measurements of the [O III] 52, 88 μm and [N III] 57 μm fine-structure emission lines have been obtained for nine planetary nebulae, using the facility far-infrared array spectrometer on NASA's Kuiper Airborne Observatory. The N++/O++ ratios determined from these observations range by more than an order of magnitude among the sample. Using recent improved values for the atomic parameters, we find that the N++/O++ ratios agree fairly well with values of N+/O+ determined from optical lines in the same objects. The highest N++/O++ values, found for the extreme “Type I” nebulae NGC 2440 and NGC 6302, are approximately unity. These results imply that the synthesis and mixing of nitrogen must be extremely efficient in the progenitor stars of some planetary nebulae, and that these nebulae are significant sources of nitrogen to the interstellar medium. The local electron densities derived from the intensity ratios of the two [O III] lines are generally lower than values in the literature determined from small-beam optical observations of other ions, such as [O II]. This effect can be understood in terms of the presence of clumpy structure in the nebula, since the far-infrared lines have fairly low critical densities for collisional de-excitation and therefore are preferentially emitted from low-density gas.

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