Phase distortion in a propulsive laser beam due to aero-optical phenomena

1990 ◽  
Vol 6 (4) ◽  
pp. 416-425 ◽  
Author(s):  
Marco A. S. Minucci ◽  
Leik N. Myrabo
Keyword(s):  
Laser Beam ◽  
Phase Distortion ◽  
Optical Phenomena

Effects of random phase distortion and nonlinear optical processes on laser beam uniformity and spatial incoherence (ISI)

1993 ◽  
Author(s):  
Robert H. Lehmberg ◽  
Stephen P. Obenschain ◽  
Carl J. Pawley ◽  
Mark S. Pronko ◽  
A. V. Deniz ◽  
...  
Keyword(s):  
Laser Beam ◽  
Nonlinear Optical ◽  
Random Phase ◽  
Phase Distortion

Controlling of Microstructure Generation by Direct Holographic Etching of Semiconductor Substrates

1992 ◽  
Vol 285 ◽  
Author(s):  
K. Toyoda ◽  
H. Kumagai ◽  
M. Ezaki ◽  
M. Obara
Keyword(s):  
Laser Beam ◽  
Holographic Grating ◽  
Phase Distortion ◽  
Beam Irradiation ◽  
Laser Etching ◽  
Holographic Gratings ◽  
Average Spacing ◽  
Spatial Fluctuation ◽  
Single Beam ◽  
Semiconductor Substrates

ABSTRACTControlling of microstructure generation was investigated in laser etching of n-GaAs. For single-beam etching and holographic etching with high ratios of average spacing of holographic grating to average spacing of microstructures (Λh/Λr), ripple structures were fabricated. Especially in p-polarization, spatial fluctuation was greater than that in s-polarization. This might occur because phase distortion inherent in the laser beam cannot be eliminated by the p-polarization beam irradiation. For holographic etching with small Λh/Λr ratios, ripple structures were changed into grating structures because these grating structures might be generated in phase with holographic gratings.

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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