Anticipated improvement in laser beam uniformity using distributed phase plates with quasirandom patterns

1990 ◽  
Vol 68 (3) ◽  
pp. 924-931 ◽  
Author(s):  
R. Epstein ◽  
S. Skupsky
Keyword(s):  
Laser Beam ◽  
Phase Plates

scholarly journals Preparation of random-phase plates for laser-beam smoothing

1995 ◽  
Author(s):  
Ian M. Thomas ◽  
Sham N. Dixit ◽  
Michael C. Rushford
Keyword(s):  
Laser Beam ◽  
Random Phase ◽  
Phase Plates

scholarly journals Spectral control of the orbital angular momentum of a laser beam based on 3D properties of spiral phase plates fabricated for an infrared wavelength

2020 ◽  
Vol 28 (12) ◽  
pp. 18407 ◽  
Author(s):  
Svetlana N. Khonina ◽  
Vladimir V. Podlipnov ◽  
Sergey V. Karpeev ◽  
Andrey V. Ustinov ◽  
Sergey G. Volotovsky ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Laser Beam ◽  
Orbital Angular Momentum ◽  
Infrared Wavelength ◽  
Spectral Control ◽  
Phase Plates ◽  
Spiral Phase

Phase plates for laser beam compensation

1977 ◽  
Vol 21 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Lee W. Casperson ◽  
Nancy K. Kincheloe ◽  
Oscar M. Stafsudd
Keyword(s):  
Laser Beam ◽  
Phase Plates

Characteristics of an Electrostatic Phase Plate

1972 ◽  
Vol 30 ◽  
pp. 618-619
Author(s):  
William Krakow ◽  
Benjamin Siegel
Keyword(s):  
Phase Contrast ◽  
Objective Lens ◽  
Phase Plate ◽  
Net Charge ◽  
Phase Plates ◽  
Beam Currents ◽  
Contrast Image ◽  
Bright Phase ◽  
Additional Phase Shift ◽  
Additional Phase

Unwin has used a metallized non-conducting thread in the back focal plane of the objective lens that stops out a portion of the unscattered beam, takes on a localized positive charge and thus produces an additional phase shift to give a different transfer function of the lens. Under the particular conditions Unwin used, the phase contrast image was shifted to bright phase contrast for optimum focus.We have investigated the characteristics of this type of electrostatic phase plate, both analytically and experimentally, as functions of the magnitude of charge and defocus. Phase plates have been constructed by using Wollaston wire to mount 0.25μ diameter platinum wires across apertures ranging from 50 to 200μ diameter and vapor depositing SiO and gold on the mounted wires to give them the desired charging characteristics. The net charge was varied by adjusting only the bias on the Wehnelt shield of the gun, and hence the beam currents and effective size of the source.

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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