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Measurement of Picosecond Laser Pulses

IP.com Disclosure Number: IPCOM000091208D
Original Publication Date: 1969-Nov-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Spiller, E: AUTHOR

Abstract

In known methods for the measurement of picosecond light pulses, the light pulse is divided into two parts which are delayed with respect to each other. A nonlinear process, second harmonic generation or two photon fluorescence, which is only strong when both pulses are present simultaneously is measured as a function of the delay time and gives information about the pulse width.

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Measurement of Picosecond Laser Pulses

In known methods for the measurement of picosecond light pulses, the light pulse is divided into two parts which are delayed with respect to each other. A nonlinear process, second harmonic generation or two photon fluorescence, which is only strong when both pulses are present simultaneously is measured as a function of the delay time and gives information about the pulse width.

In this method, the nonlinear process used is the change in the refractive index or absorption in a material illuminated with laser light. In this process, an interference pattern is produced by both parts of the pulse only if both pulses are present simultaneously. The time constant of the nonlinear material has to be shorter than the coherence time of the light. The drawing shows an arrangement for the display of a picosecond light pulse. The two parts of the laser beam to be investigated, beam 10 and beam 12, are superimposed in the plane of nonlinear medium 14. The delay between the two beams in the plane of medium 14 is a linear function of the coordinate X. A diffraction grating is produced in the nonlinear material 14 for those delays for which both beams are present simultaneously. The spatial frequency of the grating is given by the angle between beams 10 and 12 and the wavelength.

Readout beam 16 is directed onto medium 14. Lens 18 images the plane of medium 14 onto photosensitive material 20 where the light pulse is displayed. Material 20 can be a photographic emulsion sheet.

The drawing shows only one of several possib...