The two-photon laser beam as a breathing mode of the electromagnetic field

1978 ◽  
Vol 56 (4) ◽  
pp. 442-446 ◽  
Author(s):  
D. J. Rowe
Keyword(s):  
Electromagnetic Field ◽  
Laser Beam ◽  
Single Photon ◽  
Coherent Beam ◽  
Dipole Mode ◽  
Linear Processes ◽  
Breathing Mode ◽  
Quadrupole Mode ◽  
Two Photon ◽  
Coherent Mode

It is predicted that the beam from a two-photon laser, if it can be made to operate in a coherent mode, will have properties quite different from the classical properties of the standard single-photon laser. Whereas the coherent beam of the single-photon laser is a dipole mode of the electromagnetic field, that of the two-photon laser is expected to be a monopole or quadrupole mode. It is predicted that the coherence properties of the two-photon laser will show up rather dramatically in non-linear processes.

Two-photon excitation microscopy in cellular biophysics

1995 ◽  
Vol 53 ◽  
pp. 62-63
Author(s):  
David W. Piston ◽  
Brian D. Bennett ◽  
Robert G. Summers
Keyword(s):  
Confocal Microscopy ◽  
Laser Beam ◽  
Duty Cycle ◽  
Excited Electronic State ◽  
Input Power ◽  
Two Photon ◽  
Simultaneous Absorption ◽  
Photon Excitation ◽  
Very High ◽  
Two Photon Excitation

Two-photon excitation microscopy (TPEM) provides attractive advantages over confocal microscopy for three-dimensionally resolved fluorescence imaging and photochemistry. Two-photon excitation arises from the simultaneous absorption of two photons in a single quantitized event whose probability is proportional to the square of the instantaneous intensity. For example, two red photons can cause the transition to an excited electronic state normally reached by absorption in the ultraviolet. In practice, two-photon excitation is made possible by the very high local instantaneous intensity provided by a combination of diffraction-limited focusing of a single laser beam in the microscope and the temporal concentration of 100 femtosecond pulses generated by a mode-locked laser. Resultant peak excitation intensities are 106 times greater than the CW intensities used in confocal microscopy, but the pulse duty cycle of 10-5 maintains the average input power on the order of 10 mW, only slightly greater than the power normally used in confocal microscopy.

Picosecond Single-Photon and Femtosecond Two-Photon Pulsed Laser Stimulation for IC Characterization and Failure Analysis

2009 ◽  
Author(s):  
V. Pouget ◽  
E. Faraud ◽  
K. Shao ◽  
S. Jonathas ◽  
D. Horain ◽  
...  
Keyword(s):  
Femtosecond Laser ◽  
Single Photon ◽  
Pulsed Laser ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Ultrashort Laser Pulses ◽  
Laser Stimulation ◽  
Two Photon ◽  
Resolution Improvement ◽  
Ultrashort Laser

Abstract This paper presents the use of pulsed laser stimulation with picosecond and femtosecond laser pulses. We first discuss the resolution improvement that can be expected when using ultrashort laser pulses. Two case studies are then presented to illustrate the possibilities of the pulsed laser photoelectric stimulation in picosecond single-photon and femtosecond two-photon modes.

scholarly journals Wafer-Scale Epitaxial Low Density InAs/GaAs Quantum Dot for Single Photon Emitter in Three-Inch Substrate

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 930
Author(s):  
Xiaoying Huang ◽  
Rongbin Su ◽  
Jiawei Yang ◽  
Mujie Rao ◽  
Jin Liu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Single Photon ◽  
Growth Parameters ◽  
Life Time ◽  
Correlation Factor ◽  
Low Density ◽  
Wafer Scale ◽  
Two Photon ◽  
Gaas Quantum Dot ◽  
Highly Uniform

In this work, we successfully achieved wafer-scale low density InAs/GaAs quantum dots (QDs) for single photon emitter on three-inch wafer by precisely controlling the growth parameters. The highly uniform InAs/GaAs QDs show low density of μ0.96/μm2 within the radius of 2 cm. When embedding into a circular Bragg grating cavity on highly efficient broadband reflector (CBR-HBR), the single QDs show excellent optoelectronic properties with the linewidth of 3± 0.08 GHz, the second-order correlation factor g2(τ)=0.0322 ±0.0023, and an exciton life time of 323 ps under two-photon resonant excitation.

Two-Photon Excited Ultraviolet Photoluminescence of Zinc Oxide Nanorods

2008 ◽  
Vol 8 (11) ◽  
pp. 5854-5857 ◽  
Author(s):  
Guangping Zhu ◽  
Chunxiang Xu ◽  
Jing Zhu ◽  
Changgui Lu ◽  
Yiping Cui ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Emission Band ◽  
Single Photon ◽  
Zno Nanorods ◽  
Zinc Oxide Nanorods ◽  
Excitation Wavelength ◽  
Photoluminescence Intensity ◽  
Vapor Phase Transport ◽  
Two Photon ◽  
Oxide Nanorods

High density zinc oxide nanorods with uniform size were synthesized on (100) silicon substrate by vapor-phase transport method. The scanning electron microscopy images reveal that the nanorods have an average diameter of about 400 nm. The X-ray diffraction pattern demonstrates the wurtzite crystalline structure of the ZnO nanorods growing along [0001] direction. The single-photon excited photoluminescence presents a strong ultraviolet emission band at 394 nm and a weak visible emission band at 600 nm. When the ZnO nanorods were respectively pumped by various wavelength lasers from 520 nm to 700 nm, two-photon excited ultraviolet photoluminescence was observed. The dependence of the two-photon excited photoluminescence intensity on the excitation wavelength and power was investigated in detail.

scholarly journals Assessment of Fluorochromes for Two-Photon Laser Scanning Microscopy of Biofilms

2002 ◽  
Vol 68 (2) ◽  
pp. 901-909 ◽  
Author(s):  
Thomas R. Neu ◽  
Ute Kuhlicke ◽  
John R. Lawrence
Keyword(s):  
Nucleic Acid ◽  
Laser Scanning ◽  
Single Photon ◽  
Selective Excitation ◽  
Laser Scanning Microscopy ◽  
Scanning Microscopy ◽  
Excitation Wavelength ◽  
Laser Microscopy ◽  
Two Photon ◽  
Photon Excitation

ABSTRACT A major limitation for the use of two-proton laser scanning microscopy (2P-LSM) in biofilm and other studies is the lack of a thorough understanding of the excitation-emission responses of potential fluorochromes. In order to use 2P-LSM, the utility of various fluorochromes and probes specific for a range of biofilm constituents must be evaluated. The fluorochromes tested in this study included classical nucleic acid-specific stains, such as acridine orange (AO) and 4",6"-diamidino-2-phenylindole (DAPI), as well as recently developed stains. In addition, stains specific for biofilm extracellular polymeric substances (EPS matrix components) were tested. Two-photon excitation with a Ti/Sapphire laser was carried out at wavelengths from 760 to 900 nm in 10-nm steps. It was found that autofluorescence of phototrophic organisms (cyanobacteria and green algae) resulted in strong signals for the entire excitation range. In addition, the coenzyme F420-related autofluorescence of methanogenic bacteria could be used to obtain images of dense aggregates (excitation wavelength, 780 nm). The intensities of the emission signals for the nucleic acid-specific fluorochromes varied. For example, the intensities were similar for excitation wavelengths ranging from 780 to 900 nm for AO but were higher for a narrower range, 780 to 810 nm, for DAPI. In selective excitation, fading, multiple staining, and combined single-photon-two-photon studies, the recently developed nucleic acid-specific fluorochromes proved to be more suitable regardless of whether they are intended for living or fixed samples. Probes specific for proteins and glycoconjugates allowed two-photon imaging of polymeric biofilm constituents. Selective excitation-emission was observed for Calcofluor White M2R (780 to 800 nm) and SyproOrange (880 to 900 nm). In addition, fluor-conjugated concanavalin A lectins were examined and provided acceptable two-photon emission signals at wavelengths ranging from 780 to 800 nm. Finally, CellTracker, a fluorochrome suitable for long-term labeling of microbial eucaryote cells, was found to give strong emission at wavelengths ranging from 770 to 810 nm. If fluorochromes have the same two-photon excitation cross section, they are suitable for multiple staining and multichannel recording. Generally, if an appropriate excitation wavelength and fluorochrome were used, it was possible to obtain more highly resolved images for thick biofilm samples with two-photon laser microscopy than with conventional single-photon laser microscopy. Due to its potential for higher resolution in light-scattering tissue-like material, such as biofilms, and extremely localized excitation, 2P-LSM is a valuable addition to conventional confocal laser scanning microscopy with single-photon excitation. However, further development of the method and basic research are necessary to take full advantage of nonlinear excitation in studies of interfacial microbial ecology.

Improved degassing in laser beam welding of aluminum die casting by an electromagnetic field

2018 ◽  
Vol 253 ◽  
pp. 51-56 ◽  
Author(s):  
André Fritzsche ◽  
Kai Hilgenberg ◽  
Fabian Teichmann ◽  
Helge Pries ◽  
Klaus Dilger ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Laser Beam ◽  
Die Casting ◽  
Laser Beam Welding

Observation of two-times self-focusing of femtosecond laser beam in ZnO crystal by two-photon luminescence

2018 ◽  
Vol 63 (21) ◽  
pp. 1392-1396 ◽  
Author(s):  
Xiaorui Wang ◽  
Honggang Ye ◽  
Zhicheng Su ◽  
Dapeng Yu ◽  
Shijie Xu
Keyword(s):  
Femtosecond Laser ◽  
Laser Beam ◽  
Two Photon ◽  
Self Focusing ◽  
Femtosecond Laser Beam ◽  
Zno Crystal
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