A laser beam weakening the protective capacity of optical limiting devices

Free base porphyrin in chloroform solution irradiated with focused laser beam, in an open Z-scan set-up, changed color from purple to green, which was associated with protonation of the porphyrin with protonic species from photodegradation of the solvent. Protonation is demonstrated as a simple means to improve the optical limiting performance of free base porphyrin nonlinear optical (NLO) materials.

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LASER BEAM SELF-FOCUSING IN PHOTOREFRACTIVE MATERIALS: OPTICAL LIMITING APPLICATION

Journal of Nonlinear Optical Physics & Materials ◽

10.1142/s0218863500000376 ◽

2000 ◽

Vol 09 (04) ◽

pp. 441-450 ◽

Cited By ~ 10

Author(s):

D. WOLFERSBERGER ◽

N. FRESSENGEAS ◽

J. MAUFOY ◽

G. KUGEL

Keyword(s):

Laser Radiation ◽

Laser Beam ◽

Beam Energy ◽

Optical Limiting ◽

Low Energy ◽

The Self ◽

Self Focusing ◽

Photorefractive Materials ◽

Pulsed Regime ◽

Different Time Scales

This paper presents a way to achieve optical limiting using the self-focusing of a laser beam in a photorefractive medium. In this view, the protection is not based on the absorption of the beam energy in the limiting system but on a global defocusing of the light in the optical system. We have studied experimentally and theoretically the self-focusing of a single laser beam in electrically biased Bi 12 TiO 20 from the continuous to the pulsed regime. We show that photorefractive materials are, for given conditions, efficient against laser radiation on these two different time scales at a low energy level (nJ).

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Photophysics of Fullerene-Doped Nanostructures: Optical Limiting, Hologram Recording and Switching of Laser Beam

Materials Science Forum - Research Trends in Contemporary Materials Science ◽

10.4028/0-87849-441-3.363 ◽

2007 ◽

pp. 363-369

Author(s):

Natalie V. Kamanina

Keyword(s):

Laser Beam ◽

Optical Limiting ◽

Hologram Recording

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Two-photon excitation microscopy in cellular biophysics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100136684 ◽

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.

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The atomic-force microscope and its future in biology

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149350 ◽

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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