EP0497244A1 - Ultrafast camera to display the intensity profile of a laser pulse - Google Patents

Ultrafast camera to display the intensity profile of a laser pulse Download PDF

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Publication number
EP0497244A1
EP0497244A1 EP92101273A EP92101273A EP0497244A1 EP 0497244 A1 EP0497244 A1 EP 0497244A1 EP 92101273 A EP92101273 A EP 92101273A EP 92101273 A EP92101273 A EP 92101273A EP 0497244 A1 EP0497244 A1 EP 0497244A1
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EP
European Patent Office
Prior art keywords
laser pulse
pulse
intensity profile
camera
electrons
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP92101273A
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German (de)
French (fr)
Inventor
Mustapha Boussoukaya
Jean-Claude Grossetie
Joseph-Albert Miehe
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COMMUNAUTE ECONOMIQUE EUROPEENNE (CEE)
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COMMUNAUTE ECONOMIQUE EUROPEENNE (CEE)
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Publication of EP0497244A1 publication Critical patent/EP0497244A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
    • H01J31/501—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output with an electrostatic electron optic system
    • H01J31/502—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output with an electrostatic electron optic system with means to interrupt the beam, e.g. shutter for high speed photography

Definitions

  • the invention relates to a streak camera for viewing the intensity profile of a laser pulse.
  • the invention aims to provide a camera for analyzing pulses of duration less than 10 ⁇ 1 observationssec, that is to say having a temporal response of one picosecond and even less.
  • This object is achieved according to the invention by replacing the photocathode of the semiconductor type with at least one metal tip. and by sending the laser pulse to an area located opposite this point.
  • Figure 1 shows schematically and in axial section a camera according to the invention.
  • FIG. 2 represents a variant of the electron emitter according to FIG. 1.
  • an enclosure 1 which is capable of being evacuated by about 10 ⁇ 8 Torr and which comprises, centered on an axis 2, a metal needle 3, an extraction grid 4, a focusing anode 5 having a central hole, deflection plates 6 and finally a display screen 7, made of phosphorus, for example.
  • the various organs are connected to sources of electrical voltage suitable for performing their respective conventional functions.
  • the needle 3 is connected to a generator 8 of an electrical pulse which is synchronized with the optical pulse to be analyzed. The latter comes from a laser 9 placed outside the enclosure 1 and directing its beam 13 through a window 10 towards an area located opposite the needle 3.
  • the amplitude of the electric pulse supplied by the generator 8 is chosen slightly below a threshold at which spontaneous emission of electrons from the needle occurs.
  • This emission is finally obtained only by the simultaneous application of this electrical pulse and the optical beam coming from the laser 9, the emission of electrons then corresponding fairly fairly to the time profile of the optical pulse.
  • the direct realization, from a laser alone, of an electric field, of an intensity such that it produces a tunnel effect and an emission of electrons, would require significant powers of the order of 1.3.10 11W / cm2 while the joint action of the electric pulse and the optical pulse means that an optical power of the beam of the order of 105W / cm2 is enough to trigger the tunnel effect.
  • the invention therefore makes it possible to reduce the power of the laser beam to be analyzed and therefore to improve the temporal resolution of the analysis.
  • FIG. 2 represents a variant with respect to the needle 3 of FIG. 1.
  • a substrate 11 of good conductive metal which is connected as before to the generator 8 through the wall of the enclosure 1.
  • This substrate has an emission surface 12 having a certain microscopic roughness of the substrate, so that there are a plurality of tips capable of emitting electrons. It has been observed that the emission threshold is much lower when the surface is rough, because the local electric field at the top of an acute point is a factor B greater than the mean microscopic field around this point, the factor B up to 104.
  • the laser beam does not have to intersect axis 2 at 90 °.
  • an angle of 45 ° with the rough emission surface one obtains an impulse field emission accompanied by a photoemission. It is also possible to replace the pulse generator 8 with a DC voltage source, but in this case it is necessary to reduce this voltage to avoid unintentional discharges before the laser pulse is triggered.

Abstract

The invention relates to an ultrafast camera for displaying the intensity profile of a laser pulse. This camera includes, inside an evacuated enclosure, a photocathode, an extraction grid, focusing electrodes, deflection plates and a display screen. According to the invention, the electron emitter consists of at least one metal point (3, 12) and of means (9, 10) for conveying the said laser pulse (13) into a zone situated opposite this point. <IMAGE>

Description

L'invention se réfère à une caméra à balayage de lente ultrarapide (streak camera) pour visualiser le profile d'intensité d'une impulsion laser.The invention relates to a streak camera for viewing the intensity profile of a laser pulse.

Pour l'étude des phénomènes transitoires, on sait générer des impulsions laser d'une durée très brève de l'ordre de 10⁻¹⁰ sec. La connaissance exacte du profile d'intensité de cette impulsion y est très importante. On l'obtient jusqu'ici par une caméra à balayage de lente qui comporte dans une enceinte sous vide une photocathode, une grille d'extraction, des électrodes de focalisation, des plaques de déflection et un écran de visualisation. L'impulsion laser à analyser est appliquée à travers un substrat transparent de la photocathode, qui, en réponse, émet des électrons. Ceux-ci sont alors soumis au champ électrique appliqué entre la cathode et la grille d'extraction. Ils sont accélérés, passent à travers un trou dans une anode de focalisation et sont enfin défléchis par des plaques de déflection, qui reçoivent une tension en dent de scie. Sur l'écran, on peut alors visualiser la distribution temporelle des photons de l'impulsion laser qui frappent la photocathode.For the study of transient phenomena, it is known to generate laser pulses of a very short duration of the order of 10⁻¹⁰ sec. The exact knowledge of the intensity profile of this pulse is very important. Until now, this has been obtained by a slow-motion camera which comprises in a vacuum enclosure a photocathode, an extraction grid, focusing electrodes, deflection plates and a display screen. The laser pulse to be analyzed is applied through a transparent substrate of the photocathode, which, in response, emits electrons. These are then subjected to the electric field applied between the cathode and the extraction grid. They are accelerated, pass through a hole in a focusing anode and are finally deflected by deflection plates, which receive a sawtooth tension. On the screen, one can then visualize the temporal distribution of the photons of the laser pulse which strike the photocathode.

L'invention a pour but de proposer une caméra permettant d'analyser des impulsions d'une durée inférieure à 10⁻¹⁰sec, c'est-à-dire ayant une réponse temporelle d'une picoseconde et même moins.The invention aims to provide a camera for analyzing pulses of duration less than 10⁻¹ duréesec, that is to say having a temporal response of one picosecond and even less.

Ce but est atteint selon l'invention en remplaçant la photocathode de type semiconducteur par au moins une pointe métallique et en envoyant l'impulsion laser dans une zone située en face de cette pointe.This object is achieved according to the invention by replacing the photocathode of the semiconductor type with at least one metal tip. and by sending the laser pulse to an area located opposite this point.

En ce qui concerne des exemples de mise en oeuvre de l'invention, référence est faite aux revendications secondaires.As regards examples of implementation of the invention, reference is made to the secondary claims.

L'invention sera décrite ci-après plus en détail à l'aide d'un exemple de réalisation et des dessins annexes.The invention will be described below in more detail with the aid of an example embodiment and the accompanying drawings.

La figure 1 montre schématiquement et en coupe axiale une caméra selon l'invention.Figure 1 shows schematically and in axial section a camera according to the invention.

La figure 2 représente une variante de l'émetteur d'électrons selon la figure 1.FIG. 2 represents a variant of the electron emitter according to FIG. 1.

Sur la figure 1, on voit une enceinte 1, qui est susceptible d'être mise sous vide d'environ 10⁻⁸ Torr et qui comporte, centrés sur un axe 2, une aiguille métallique 3, une grille d'extraction 4, une anode de focalisation 5 ayant un trou central, des plaques de déflection 6 et enfin un écran de visualisation 7, en phosphore, par exemple. Les différents organes sont reliés à des sources de tension électrique adéquats pour assurer leurs fonctions conventionelles respectives. En particulier, l'aiguille 3 est connectée à un générateur 8 d'une impulsion électrique qui est synchronisée avec l'impulsion optique à analyser. Cette dernière provient d'un laser 9 placé hors de l'enceinte 1 et dirigeant son faisceau 13 à travers une fenêtre 10 vers une zone située en face de l'aiguille 3. L'amplitude de l'impulsion électrique fournie par le générateur 8 est choisie légèrement inférieure à un seuil auquel se produit une émission spontanée d'électrons de l'aiguille.In Figure 1, we see an enclosure 1, which is capable of being evacuated by about 10⁻⁸ Torr and which comprises, centered on an axis 2, a metal needle 3, an extraction grid 4, a focusing anode 5 having a central hole, deflection plates 6 and finally a display screen 7, made of phosphorus, for example. The various organs are connected to sources of electrical voltage suitable for performing their respective conventional functions. In particular, the needle 3 is connected to a generator 8 of an electrical pulse which is synchronized with the optical pulse to be analyzed. The latter comes from a laser 9 placed outside the enclosure 1 and directing its beam 13 through a window 10 towards an area located opposite the needle 3. The amplitude of the electric pulse supplied by the generator 8 is chosen slightly below a threshold at which spontaneous emission of electrons from the needle occurs.

Cette émission n'est enfin obtenue que par l'application simultanée de cette impulsion électrique et du faisceau optique provenant du laser 9, l'émission d'électrons correspondant alors assez fidèlement au profil temporel de l'impulsion optique. La réalisation directe, à partir d'un laser seul, d'un champ électrique, d'une intensité telle qu'il se produit un effet tunnel et une émission d'électrons, nécessiterait des puissances importantes de l'ordre de 1,3.10¹¹W/cm² alors que l'action conjointe de l'impulsion électrique et de l'impulsion optique fait qu'une puissance optique du faisceau de l'ordre de 10⁵W/cm² suffit pour déclencher l'effet tunnel. L'invention permet donc de réduire la puissance du faisceau laser à analyser et donc d'améliorer la résolution temporelle de l'analyse.This emission is finally obtained only by the simultaneous application of this electrical pulse and the optical beam coming from the laser 9, the emission of electrons then corresponding fairly fairly to the time profile of the optical pulse. The direct realization, from a laser alone, of an electric field, of an intensity such that it produces a tunnel effect and an emission of electrons, would require significant powers of the order of 1.3.10 ¹¹W / cm² while the joint action of the electric pulse and the optical pulse means that an optical power of the beam of the order of 10⁵W / cm² is enough to trigger the tunnel effect. The invention therefore makes it possible to reduce the power of the laser beam to be analyzed and therefore to improve the temporal resolution of the analysis.

La figure 2 représente une variante par rapport à l'aiguille 3 de la figure 1. On y voit en effet un substrat 11 en métal bon conducteur qui est relié comme précédemment au générateur 8 à travers la paroi de l'enceinte 1. Ce substrat comporte une surface d'émission 12 ayant une certaine rugosité microscopique du substrat, de sorte qu'il y a une pluralité de pointes susceptibles d'émettre des électrons. On a observé que le seuil d'émission est bien plus bas lorsque la surface est rugueuse, car le champ électrique local au sommet d'une pointe aigue est d'un facteur B plus grande que le champ microscopique moyen autour de cette pointe, le facteur B pouvant atteindre 10⁴.FIG. 2 represents a variant with respect to the needle 3 of FIG. 1. In fact there is seen there a substrate 11 of good conductive metal which is connected as before to the generator 8 through the wall of the enclosure 1. This substrate has an emission surface 12 having a certain microscopic roughness of the substrate, so that there are a plurality of tips capable of emitting electrons. It has been observed that the emission threshold is much lower when the surface is rough, because the local electric field at the top of an acute point is a factor B greater than the mean microscopic field around this point, the factor B up to 10⁴.

L'invention n'est pas limitée à l'exemple de réalisation décrit ci-dessus. Ainsi, il n'est pas obligatoire que le faisceau laser intersecte l'axe 2 à 90°. En choisissant par exemple un angle de 45° avec la surface d'émission rugueuse, on obtient une émission de champ impulsionnel accompagnée d'une photoémission. On peut en outre remplacer le générateur d'impulsions 8 par une source de tension continue, mais dans ce cas il faut réduire cette tension pour éviter des décharges involontaires avant que l'impulsion laser soit déclenchée.The invention is not limited to the embodiment described above. Thus, the laser beam does not have to intersect axis 2 at 90 °. By choosing for example an angle of 45 ° with the rough emission surface, one obtains an impulse field emission accompanied by a photoemission. It is also possible to replace the pulse generator 8 with a DC voltage source, but in this case it is necessary to reduce this voltage to avoid unintentional discharges before the laser pulse is triggered.

Claims (3)

Caméra ultrarapide pour visualiser le profile d'intensité d'une impulsion laser, comportant dans une enceinte sous vide une photocathode, une grille d'extraction, des électrodes de focalisation, des plaques de déflection et un écran de visualisation, caractérisée en ce que l'émetteur d'électrons est constitué d'au moins une pointe métallique (3, 12) et de moyens (9,10) pour envoyer ladite impulsion laser (13) dans une zone située en face de cette pointe.Ultra-fast camera for viewing the intensity profile of a laser pulse, comprising in a vacuum chamber a photocathode, an extraction grid, focusing electrodes, deflection plates and a display screen, characterized in that the 'emitter of electrons consists of at least one metal tip (3, 12) and means (9,10) for sending said laser pulse (13) in an area located opposite this tip. Caméra selon la revendication 1, caractérisée en ce que l'émetteur comporte une pluralité de pointes définissant une surface rugueuse (12) d'un support métallique (11) (figure 2).Camera according to claim 1, characterized in that the transmitter has a plurality of points defining a rough surface (12) of a metal support (11) (Figure 2). Méthode de mise en oeuvre de la caméra selon l'une des revendications précédentes, caractérisée en ce que la tension électrique d'extraction appliquée entre la grille d'extraction et les pointes est une impulsion électrique qui définit une fenêtre autour de l'impulsion laser à visualiser, l'amplitude de cette impulsion électrique étant choisie légèrement inférieure à celle nécessaire pour causer toute seule une émission d'électrons.Method of operating the camera according to one of the preceding claims, characterized in that the electric extraction voltage applied between the extraction grid and the tips is an electric pulse which defines a window around the laser pulse to be viewed, the amplitude of this electrical pulse being chosen to be slightly lower than that necessary to cause an emission of electrons on its own.
EP92101273A 1991-01-30 1992-01-27 Ultrafast camera to display the intensity profile of a laser pulse Pending EP0497244A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
LU87882 1991-01-30
LU87882A LU87882A1 (en) 1991-01-30 1991-01-30 ULTRA-FAST CAMERA FOR VIEWING THE INTENSITY PROFILE OF A LASER PULSE

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EP0497244A1 true EP0497244A1 (en) 1992-08-05

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EP92101273A Pending EP0497244A1 (en) 1991-01-30 1992-01-27 Ultrafast camera to display the intensity profile of a laser pulse
EP92902925A Expired - Lifetime EP0678218B1 (en) 1991-01-30 1992-01-27 Method for visualising the intensity profile of a laser pulse

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US (1) US5362959A (en)
EP (2) EP0497244A1 (en)
JP (1) JPH06504649A (en)
AT (1) ATE185220T1 (en)
CA (1) CA2100266C (en)
DE (1) DE69230075T2 (en)
IE (1) IE920295A1 (en)
LU (1) LU87882A1 (en)
WO (1) WO1992014257A1 (en)

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JPH0944621A (en) * 1995-07-25 1997-02-14 Yokohama Rubber Co Ltd:The Information memory cell, scanner and information storage and reproducing device
US7721948B1 (en) * 1999-05-25 2010-05-25 Silverbrook Research Pty Ltd Method and system for online payments
RU2704330C1 (en) * 2018-11-30 2019-10-28 Федеральное государственное бюджетное учреждение науки Институт спектроскопии Российской академии наук (ИСАН) Photoemission profilometer of laser beam

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0127735A1 (en) * 1983-05-03 1984-12-12 DORNIER SYSTEM GmbH Photo cathode and method of manufacturing such a cathode
US4868380A (en) * 1988-03-02 1989-09-19 Tektronix, Inc. Optical waveguide photocathode
FR2662036A1 (en) * 1990-05-14 1991-11-15 Centre Nat Rech Scient Slit-scanning camera

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Publication number Priority date Publication date Assignee Title
US5013902A (en) * 1989-08-18 1991-05-07 Allard Edward F Microdischarge image converter
JP3071809B2 (en) * 1990-09-07 2000-07-31 浜松ホトニクス株式会社 Streak tube

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0127735A1 (en) * 1983-05-03 1984-12-12 DORNIER SYSTEM GmbH Photo cathode and method of manufacturing such a cathode
US4868380A (en) * 1988-03-02 1989-09-19 Tektronix, Inc. Optical waveguide photocathode
FR2662036A1 (en) * 1990-05-14 1991-11-15 Centre Nat Rech Scient Slit-scanning camera

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
IBM TECHNICAL DISCLOSURE BULLETIN. vol. 26, no. 12, Mai 1984, NEW YORK US pages 6604 - 6605; J KASH: 'Picosecond streak camera with single photon sensitivity' *

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Publication number Publication date
CA2100266C (en) 2002-05-14
CA2100266A1 (en) 1992-07-31
EP0678218A1 (en) 1995-10-25
EP0678218B1 (en) 1999-09-29
WO1992014257A1 (en) 1992-08-20
DE69230075T2 (en) 2000-01-05
JPH06504649A (en) 1994-05-26
US5362959A (en) 1994-11-08
DE69230075D1 (en) 1999-11-04
LU87882A1 (en) 1992-10-15
IE920295A1 (en) 1992-07-29
ATE185220T1 (en) 1999-10-15

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