Spatial coherence of electrically pumped random terahertz lasers

2021 ◽  
Author(s):  
EVA ARIANNA AURELIA POGNA ◽  
Alessandra Di Gaspare ◽  
Kimberly Reichel ◽  
Chiara Liberatore ◽  
Harvey Beere ◽  
...  
Keyword(s):  
Spatial Coherence ◽  
Electrically Pumped ◽  
Terahertz Lasers

Terahertz-wave generation using graphene

2012 ◽  
Vol 1437 ◽  
Author(s):  
Taiichi Otsuji ◽  
Stephane Boubanga Tombet ◽  
Akira Satou ◽  
Maxim Ryzhii ◽  
Victor Ryzhii
Keyword(s):  
Terahertz Wave ◽  
Wave Generation ◽  
Nonequilibrium Carrier ◽  
Terahertz Range ◽  
Two Dimensional ◽  
Carrier Relaxation ◽  
Dynamic Conductivity ◽  
Electrically Pumped ◽  
Terahertz Lasers ◽  
Recombination Dynamics

ABSTRACTIn this paper recent advances in terahertz-wave generation in graphene are reviewed. First, fundamental basis of the optoelectronic properties of graphene is introduced. Second, nonequilibrium carrier relaxation and recombination dynamics in optically or electrically pumped graphene is described to introduce a possibility of negative dynamic conductivity in a wide terahertz range. Third, recent theoretical advances toward the creation of current-injection graphene terahertz lasers are described. Fourth, unique terahertz dynamics of the two-dimensional plasmons in graphene are described. Finally, the advantages of graphene materials and devices for terahertz-wave generation are summarized.

scholarly journals Electrically pumped semiconductor laser with low spatial coherence and directional emission

2019 ◽  
Vol 115 (7) ◽  
pp. 071101 ◽  
Author(s):  
Kyungduk Kim ◽  
Stefan Bittner ◽  
Yongquan Zeng ◽  
Seng Fatt Liew ◽  
Qijie Wang ◽  
...  
Keyword(s):  
Semiconductor Laser ◽  
Spatial Coherence ◽  
Directional Emission ◽  
Electrically Pumped

Low-spatial coherence electrically pumped red-emitting semiconductor laser

2018 ◽  
Author(s):  
Wanhua Zheng ◽  
Yufei Jia ◽  
Yufei Wang ◽  
Shao Yu Zhao ◽  
Linhai Xu ◽  
...  
Keyword(s):  
Semiconductor Laser ◽  
Spatial Coherence ◽  
Electrically Pumped

Electrically pumped photonic-crystal terahertz lasers controlled by boundary conditions

Nature ◽  
2009 ◽  
Vol 457 (7226) ◽  
pp. 174-178 ◽  
Author(s):  
Y. Chassagneux ◽  
R. Colombelli ◽  
W. Maineult ◽  
S. Barbieri ◽  
H. E. Beere ◽  
...  
Keyword(s):  
Photonic Crystal ◽  
Boundary Conditions ◽  
Electrically Pumped ◽  
Terahertz Lasers

scholarly journals Low spatial coherence electrically pumped semiconductor laser for speckle-free full-field imaging

2015 ◽  
Vol 112 (5) ◽  
pp. 1304-1309 ◽  
Author(s):  
Brandon Redding ◽  
Alexander Cerjan ◽  
Xue Huang ◽  
Minjoo Larry Lee ◽  
A. Douglas Stone ◽  
...  
Keyword(s):  
Semiconductor Laser ◽  
High Speed ◽  
Spatial Coherence ◽  
Spectral Radiance ◽  
Laser Resonator ◽  
Full Field ◽  
Wide Range ◽  
Electrically Pumped ◽  
Laser Sources ◽  
Field Imaging

The spatial coherence of laser sources has limited their application to parallel imaging and projection due to coherent artifacts, such as speckle. In contrast, traditional incoherent light sources, such as thermal sources or light emitting diodes (LEDs), provide relatively low power per independent spatial mode. Here, we present a chip-scale, electrically pumped semiconductor laser based on a novel design, demonstrating high power per mode with much lower spatial coherence than conventional laser sources. The laser resonator was fabricated with a chaotic, D-shaped cavity optimized to achieve highly multimode lasing. Lasing occurs simultaneously and independently in ∼1,000 modes, and hence the total emission exhibits very low spatial coherence. Speckle-free full-field imaging is demonstrated using the chaotic cavity laser as the illumination source. The power per mode of the sample illumination is several orders of magnitude higher than that of a LED or thermal light source. Such a compact, low-cost source, which combines the low spatial coherence of a LED with the high spectral radiance of a laser, could enable a wide range of high-speed, full-field imaging and projection applications.

Quanitative aspects of electron diffraction using electron holography

1995 ◽  
Vol 53 ◽  
pp. 616-617
Author(s):  
E. Völkl ◽  
L.F. Allard ◽  
B. Frost ◽  
T.A. Nolan
Keyword(s):  
Electron Beam ◽  
Electron Diffraction ◽  
Software Package ◽  
Spatial Coherence ◽  
Electron Holography ◽  
Image Intensity ◽  
Interference Fringes ◽  
Complex Image ◽  
The Difference ◽  
Recorded Image

Off-axis electron holography has the well known ability to preserve the complex image wave within the final, recorded image. This final image described by I(x,y) = I(r) contains contributions from the image intensity of the elastically scattered electrons IeI (r) = |A(r) exp (iΦ(r)) |, the contributions from the inelastically scattered electrons IineI (r), and the complex image wave Ψ = A(r) exp(iΦ(r)) as:(1) I(r) = IeI (r) + Iinel (r) + μ A(r) cos(2π Δk r + Φ(r))where the constant μ describes the contrast of the interference fringes which are related to the spatial coherence of the electron beam, and Φk is the resulting vector of the difference of the wavefront vectors of the two overlaping beams. Using a software package like HoloWorks, the complex image wave Ψ can be extracted.

An Alternate Algorithm for (3x3) Median Filtering of Digital Images

2012 ◽  
Vol 2 (1) ◽  
pp. 7-9 ◽  
Author(s):  
Satinderjit Singh
Keyword(s):  
Median Filter ◽  
Computational Cost ◽  
Spatial Coherence ◽  
General Purpose ◽  
Median Filtering ◽  
Basic Algorithm ◽  
Temporal Complexity ◽  
Filter Kernel ◽  
One Step ◽  
High Computational Cost

Median filtering is a commonly used technique in image processing. The main problem of the median filter is its high computational cost (for sorting N pixels, the temporal complexity is O(N·log N), even with the most efficient sorting algorithms). When the median filter must be carried out in real time, the software implementation in general-purpose processorsdoes not usually give good results. This Paper presents an efficient algorithm for median filtering with a 3x3 filter kernel with only about 9 comparisons per pixel using spatial coherence between neighboring filter computations. The basic algorithm calculates two medians in one step and reuses sorted slices of three vertical neighboring pixels. An extension of this algorithm for 2D spatial coherence is also examined, which calculates four medians per step.

Light intensity and spatial coherence characteristics of laser coherent detection in a turbulent atmosphere

2020 ◽  
Vol 13 (4) ◽  
pp. 728-736
Author(s):  
REN Jian-ying ◽  
◽  
◽  
SUN Hua-yan ◽  
ZHAO Yan-zhong ◽  
...  
Keyword(s):  
Light Intensity ◽  
Turbulent Atmosphere ◽  
Spatial Coherence ◽  
Coherent Detection
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