Technique shoots two broad light beams onto a photosensitive surface which responds nonlinearly to the intensity in the beams. The resultant signal contains a component depending on the intensity correlation function between the two light beams

Billman, K. W.

Burnham, D. C.

English

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September 1970	 Brief 70-10377 
NASA TECH BRIEF
	
ETI 
NASA Tech Briefs announce new technology derived from the U .S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Picosecond Pulse Measurement by Two-Photon Excitation

of Photographic Film 
- I - ****^<
- - — 
Experimental Arrangement for Measuring Short Duration Light Pulses 
A simplified technique for observing picosecond 
light pulses has been developed. The two advantages 
of this new technique, namely, simplicity and easily 
varied resolution, make it a useful research tool for 
the laser industry and organizations interested in spec-
troscopy and short duration light pulses. 
The basic technique is to shoot two broad light 
beams onto a photosensitive surface which responds 
nonlinearly to the intensity in the beams. The resultant
signal will contain a component depending on the 
intensity correlation function between the two light 
beams. By changing the angles at which the beams hit 
the surface, the relationship between the correlation 
time difference and the position on the detector can be 
varied; thus, the resolution can be made as high as 
desired. 
Almost all photosensitive surfaces (e.g., photo-
graphic emulsions, photoelectric and photoconductive 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned .rights.
https://ntrs.nasa.gov/search.jsp?R=19700000363 2020-03-17T00:45:03+00:00Z
surfaces) have a threshold wavelength, A, beyond 
which they have zero linear intensity response. For 
longer wavelengths up to 2 A 0 , they can respond by a 
two-photon response. This broad bandwidth (leading 
to very short time resolution) is a significant advantage 
over the clashing beam fluorescent dye technique. 
Two plane light beams are allowed to fall onto a 
photographic plate at angles 01 and 0 2 with respect 
to the normal. The simple experimental arrangement 
used to produce the two incident beams is shown in 
the figure. Observation of picosecond light pulses 
depends on the two-photon photographic response 
resulting from two-photon excitation of the organic 
photosensitizing dye in the emulsion which makes 
the film sensitive at the second harmonic. 
Notes: 
1. The two-photon film technique has been used to 
study the pulses from a diffraction limited, mode-
locked neodymium glass laser (A = 1.06k). At 
nanosecond resolution the laser output (2-mm 
diameter) consisted of three or four spikes of 
roughly 5 millijoules energy each and 10 nano-
second spacing.
2. The primary disadvantage of the film technique 
is low sensitivity. The technique requires a spread-
out beam which can use each photon to excite only 
one resolution element of the detector. Since the 
response depends quadratically on the intensity, 
spreading out the beam results in rapid loss of sen-
sitivity. 
3. Requests for further information may be directed 
to:
Technology Utilization Officer 
Headquarters 
National Aeronautics and 
Space Administration 
Washington, D.C. 20546 
Reference: TSP70-10377 
Patent status: 
This invention is owned by NASA, and a patent

application has been filed. Royalty-free, nonexclusive

licenses for its commercial use will be granted by

NASA. Inquiries concerning license rights should be

made to NASA, Code GP, Washington, D.C. 20546.

Source: Dr. D.C. Burnham and Dr. K.W. Biliman

Electronics Research Center

(ERC-10227) 
Brief 70-10377	 CategoryO2


Picosecond pulse measurement by two-photon excitation of photographic film

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