Measurement of phase fluctuations in a HF chemical laser beam

1979 ◽  
Vol 50 (12) ◽  
pp. 7917-7920 ◽  
Author(s):  
C. P. Wang ◽  
R. L. Varwig
Keyword(s):  
Laser Beam ◽  
Chemical Laser ◽  
Phase Fluctuations

Interferometric Study of Phase Fluctuations of a Laser Beam Through the Turbulent Atmosphere

1968 ◽  
Vol 7 (11) ◽  
pp. 2246 ◽  
Author(s):  
M. Bertolotti ◽  
M. Carnevale ◽  
L. Muzii ◽  
D. Sette
Keyword(s):  
Laser Beam ◽  
Turbulent Atmosphere ◽  
Phase Fluctuations ◽  
Interferometric Study

scholarly journals Influence of Laboratory Generated Turbulence on Phase Fluctuations of a Laser Beam

1968 ◽  
Vol 7 (6) ◽  
pp. 1121 ◽  
Author(s):  
M. Carnevale ◽  
B. Crosignani ◽  
P. Di Porto
Keyword(s):  
Laser Beam ◽  
Phase Fluctuations

scholarly journals Influence of Thermal Turbulence in a Convective Ascending Stream on Phase Fluctuations of a Laser Beam

1969 ◽  
Vol 8 (6) ◽  
pp. 1111 ◽  
Author(s):  
M. Bertolotti ◽  
M. Carnevale ◽  
B. Crosignani ◽  
P. Di Porto
Keyword(s):  
Laser Beam ◽  
Phase Fluctuations ◽  
Thermal Turbulence

Numerical Analysis of Performance of DF Chemical Laser With a Radial-Expansion Nozzle Array According to D2 Injection Angles

Volume 1 ◽  
2004 ◽  
Author(s):  
Jun Sung Park ◽  
Seung Wook Baek
Keyword(s):  
Laser Beam ◽  
Flow Direction ◽  
Laser System ◽  
Laser Cavity ◽  
High Mass ◽  
Beam Power ◽  
Chemical Laser ◽  
Injection Angle ◽  
Main Flow Direction ◽  
Excited Molecules

It is chemical laser system that can be used for not only new strategic weapon system for the military purpose, but also a manufacturing tool in industrial areas due to the characteristic of high power laser beam in megawatt range. In order to increase laser beam power in the chemical laser system, mixing efficiency of fuel and oxidant should be higher and more excited molecules be produced by mean of chemical reaction. Basically, the production of a lot of excited molecules in the laser cavity results from the high mass flow rates of fuel and oxidant as well as high mixing and reaction efficiencies, however, it is difficult for the planar nozzle array which has been widely used until now to supply high mass flow to the chemical laser cavity. A radial expansion nozzle array as an innovated alternative of the planar nozzle system is designed. The laser beam generation in this system is achieved by mixing F atom from supersonic nozzle and D2 molecule from the holes of round-bended supply line which are distributed with zigzag configuration, hence the reaction surface will be stretched. Consequently, it is expected that more excited molecules will be produced and population inversion also be higher. Based on that the fuel injection angle with mainstream has a big influence of performance of supersonic combustor, the effects of D2 injection angles with the main F flow on mixing enhancement and laser beam power are numerically investigated. The results are discussed by comparison with three cases of D2 injection angles; 10°, 20° and 40° with the main flow direction. Major results reveal that the area where the DF(1) excited molecules as a representative product in the DF chemical laser system are produced becomes larger when the D2 injection angle increases. The reason is that the surface of chemical reaction is larger and the field temperature is higher with increase of the D2 injection angle. And in all the vibrational transitions, the distributions of the highest maximum small signal gains are observed near the inlet when the D2 injection angle is 40°. As the D2 injection angle increases, the values of the maximum SSG are higher and the area including the high gains is also wider for the most part of domain. Based on these maximum SSG distributions, the highest power of laser beam is expected to be generated when the D2 injection angle is 40°, namely higher. However, the range of population inversion becomes narrower as the D2 injection angle increases, because the collision of molecules or atoms happens more often so that the relaxation time will be reduced as the cavity pressure caused by the high D2 injection angle with the main flow direction increases.

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.

The atomic-force microscope and its future in biology

1993 ◽  
Vol 51 ◽  
pp. 704-705
Author(s):  
Jean-Paul Revel
Keyword(s):  
Silicon Nitride ◽  
Laser Beam ◽  
Atomic Force Microscope ◽  
Scanning Tunneling Microscope ◽  
Point Of View ◽  
Scanning Tunneling ◽  
Close Relative ◽  
Tunneling Microscope ◽  
Atomic Force ◽  
Sharp Point

The last few years have been marked by a series of remarkable developments in microscopy. Perhaps the most amazing of these is the growth of microscopies which use devices where the place of the lens has been taken by probes, which record information about the sample and display it in a spatial from the point of view of the context. From the point of view of the biologist one of the most promising of these microscopies without lenses is the scanned force microscope, aka atomic force microscope.This instrument was invented by Binnig, Quate and Gerber and is a close relative of the scanning tunneling microscope. Today's AFMs consist of a cantilever which bears a sharp point at its end. Often this is a silicon nitride pyramid, but there are many variations, the object of which is to make the tip sharper. A laser beam is directed at the back of the cantilever and is reflected into a split, or quadrant photodiode.

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