EP0742912A1 - Dispositif d'expansion et de compression d'impulsions laser a reseau unique - Google Patents

Dispositif d'expansion et de compression d'impulsions laser a reseau unique

Info

Publication number
EP0742912A1
EP0742912A1 EP94909474A EP94909474A EP0742912A1 EP 0742912 A1 EP0742912 A1 EP 0742912A1 EP 94909474 A EP94909474 A EP 94909474A EP 94909474 A EP94909474 A EP 94909474A EP 0742912 A1 EP0742912 A1 EP 0742912A1
Authority
EP
European Patent Office
Prior art keywords
laser beam
pulsed laser
reflector
directed
grating element
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.)
Withdrawn
Application number
EP94909474A
Other languages
German (de)
English (en)
Inventor
Ming Lai
Shui T. Lai
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Novatec Laser Systems Inc
Original Assignee
Novatec Laser Systems Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Novatec Laser Systems Inc filed Critical Novatec Laser Systems Inc
Priority claimed from PCT/US1994/000704 external-priority patent/WO1995020178A1/fr
Publication of EP0742912A1 publication Critical patent/EP0742912A1/fr
Withdrawn legal-status Critical Current

Links

Definitions

  • This invention relates to temporally stretch and compress laser pulses and particularly for the application of amplifying sub-picosecond laser pulses (less than 1 ps) to an energy level greater than 100 micro joules (J) per pulse.
  • An optical pulse stretcher-compressor is a key element in a chirped-pulse or regenerative laser amplifier for amplifying sub-picosecond laser pulses to an energy level greater than 100 micro joule per pulse.
  • the stretcher is used to lengthen the optical pulses before the amplification, and the compressor is used to resume the original pulse duration after the amplification. In this way, the peak power inside the amplifier cavity can be kept low enough to avoid any damage to the optical elements and avoid nonlinear distortion on the pulse shape and beam profile.
  • the invention is directed to a new and novel method for combined pulse stretching and compression of a pulsed laser beam of various different output frequencies.
  • the device utilizes a single grating device for both stretching and compressing of a laser pulse.
  • the grating device has vertical height sufficient for six different level beam passes, namely, four passes for the stretcher and two passes for the compressor.
  • the beam enters and strikes the grating and is directed through collimating optics, as for example, focusing lens, converging mirror or equivalent, to a mirror, the beam from the mirror is directed back to the grating element, the beam returns through the optics again striking a retro-reflective device such as for example, a roof mirror or the equivalent, the beam is again reflected to the grating, reflected from the grating to a mirror through collimating optics, reflected back to the grating, and exits the stretcher and enters a pulse amplifier.
  • collimating optics as for example, focusing lens, converging mirror or equivalent
  • the beam When amplified, the beam enters a compressor in which utilizes the bottom portion of the grating element of the stretcher.
  • the amplified beam enters the compressor and is directed toward the grating element, to a retro-reflective device, back to the grating element, to a mirror reflector, back to the grating, back to the retro-reflector device, as described above, from the retro-reflector to the grating and out for intended use now amplified and in substantially in its original pulse width.
  • the only element that need adjusting is the diffraction grating.
  • the grating element is adjusted only.
  • An object of this invention is to produce a laser pulse stretcher-compressor that requires only the adjustment of one grating when the pulse frequency is changed.
  • Another object of this invention is to provide a combined laser pulse stretcher and compressor utilizing a common grating element.
  • Figure 1 depicts a schematic showing of the prior art pulse stretcher
  • Figure 2 depicts a schematic showing of a prior art grating pulse compressor
  • Figure 3 depicts a schematic showing of a side view showing of the combined pulse stretcher-compressor of the invention showing beam vertical elevations;
  • Figure 4 depicts a plan view showing of Figure 3 showing the beam path of the stretcher portion of the device.
  • Figure 5 depicts a plan view showing of the bottom portion of the Figure 3 showing taken along line 5-5 of Figure 3.
  • drawing Figure 1 a grating pulse stretcher 10 is depicted.
  • a pulsed laser beam 12 is introduced into the stretcher and impacts input mirror 14 which reflects the beam to grating 16.
  • the beam is directed from the grating to a second mirror 18 through a collimating lens 19, reflected back to the grating through lens 19 and from the grating to a step down prism 23, the beam is reflected from the step down prism back to the grating, reflected from the grating through lens 19 to the second mirror 18, reflected from the second mirror through collimating lens 19, focusing element, to the grating, from the grating the beam is directed to output mirror 20 as a stretched beam which is directed to a pulses amplifier 21 well known in this art.
  • a pulses amplifier 21 well known in this art.
  • the beam 22 is directed to an input mirror 14a to a mirror 18a to a grating 26, to a second grating 26a, to a step down retro-reflector 18b, reflected back to grating 26a, reflected back to grating 26, reflected to mirror 18a, reflected to mirror 28 and reflected out for the amplified beam's intended use.
  • Figures 3-5 depict the stretcher-compressor 30 of the invention showing a single grating vertically stacked stretcher-compressor.
  • Figure 3 is a side view of the apparatus 30.
  • the top portion (layer) is the laser pulse beam stretcher portion and the bottom portion (layer) is the laser pulse compressor portion.
  • Figure 4 is a top plan view of the stretcher, and
  • Figure 5 is a top plan view of the compressor taken along line 5-5 of Figure 3.
  • the stretcher portion consists of the top half of a diffraction grating 32.
  • a focusing element such as for example, a lens 34 typically having a focal length of 50 cm, 1" x 3.5" and an antireflection coating (AR), a flat mirror 36 having a dimension of 2"x 2", a high reflection (HR) coating, and a retro-reflective device herein after referred to as a roof mirror reflector 38 typical a rectangular of 0.5"x 3", HR coated for vertical displacement.
  • the compressor portion composes the bottom half of the grating 32, a roof mirror reflector 40a typically a rectangle of 1" x 3", HR coated) for horizontal displacement, and a roof mirror reflector 42 having typical dimensions of 0.5" x 3", HR coated for vertical displacement.
  • a beam 44 of laser pulses to be stretched impinges on grating 32 in an angle near a Littrow angle. Its first order diffracted beam 46 hits lens 34. The transmitted beam 48 from the lens hits mirror 36. The reflected beam 50 from the mirror is directed to lens 34. Then the beam 52 from lens 34 is directed to grating 32. Lens 34 is vertically displaced down, as for example, 3/8" from the level of input beam 44. The returning beam 52 is lower than beam 44 as for example, 3/4" lower. The returning beam 52 is re-collimated by grating 32. The re-collimated beam 54 is directed from the grating to roof mirror reflector 38.
  • the reflected beam 56 from the roof mirror reflector is spaced above beam 54 by approximately 1/4" and is directed to grating 32. Then the diffracted beam 58 from the grating is directed to lens 34.
  • the beam 60 leaving lens 34 is directed to mirror 36.
  • the reflected beam 62 leaving mirror 36 passes through lens 34.
  • the transmitted beam 64 leaving lens 34 is directed to grating 32.
  • the beam leaving the grating is the stretched beam 66 is the output beam of the stretcher. That is, after impacting the grating 32 for the fourth time, the ultrashort pulses of input beam 44 become linearly chirped, stretched pulses of output beam 66. This output beam 66 propagates in the opposite direction of and with a displacement down input beam 44 as for example, 1/4".
  • the pulse duration can be modified.
  • the diffracted beam 46 after the grating element 32 is spatially spread out in the horizontal direction. The extent of this spread is defined by the spectral content of the laser pulse.
  • An aperture 47 of a smaller dimension can be inserted in the beam path after beam position 46.
  • the spatial content of the laser beam is reduced by such aperture size.
  • the overall effect of reducing the beam spatial content is to increase the temporal profile of the laser pulse before such pulse is to be compressed in the pulse compressor of the instant invention.
  • a beam 67 of laser pulses to be compressed impinges on grating 32 at the same angle as the input beam 44 of the stretcher.
  • the first-order diffracted beam 66 from the grating hits a roof mirror reflector 40.
  • the reflected beam 68 from the reflector is side ways shifted as for example, about 1.5" from beam 66 and is directed to grating 32.
  • This returning beam 68 is re- collimated by the grating.
  • the re-collimated beam 70 impacts the retro-reflector 40b, typically a roof mirror reflector.
  • the reflected beam 72 from the reflector is directed below the beam 70 as for example, by about a 1.5" and is directed toward grating 32.
  • the diffracted beam 74 from the grating 32 is directed to roof mirror reflector 40.
  • the reflected beam 76 from the reflector 38a is sideways shifted from beam 74 as for example, about 1/4", and is directed to grating 32.
  • the diffracted beam 78 from the grating is the output of the compressor.
  • the linearly chirped, stretched pulses in input beam 67 become compressed, ultrashort pulses of output beam 78.
  • This output beam 78 propagates in the opposite direction of and with a displacement down as for example, a 1/4", from input beam 64.
  • the spacing between lens 34 and mirror 36 should be equal to the focal length of the lens 34.
  • the distance from grating 32 to lens 34 controls the amount of positive group velocity dispersion, which determines the ratio of pulse stretching.
  • the path length from grating 34 to reflector 36 controls the amount of negative group velocity dispersion, which determines the ratio of pulse compression.
  • the relevant theory can be found in references 2 and 3 above.
  • the output pulses from the stretcher are fed as seed pulses into the amplifier 21.
  • the output pulses from the amplifier are then directed back as an input to the compressor.
  • the output from the compressor is then of high energy up to 100 micro Joules, ultrashort less than 1 pico ⁇ second laser pulses.

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  • Lasers (AREA)

Abstract

On décrit un procédé et un appareil à réseau unique pour un dispositif d'expansion et de compression d'impulsions laser (30). Le procédé et l'appareil font appel à une structure verticale à deux couches: une couche pour la section d'expansion (éléments 32, 34, 36 et 38) et une couche pour la section compression (élément 32, 40a, 40b). Ceci permet de disposer des composants additionnels entre les sections respectives d'expansion et de compression. On décrit des applications du dispositif dans les amplificateurs à impulsions modulées en fréquence et à réaction, lorsqu'on souhaite obtenir une syntonisation. Lorsqu'on effectue un changement de la longueur d'onde d'entrée, il suffit d'un seul ajustage en rotation pour revenir à un alignement de tout le dispositif d'expansion et de compression.
EP94909474A 1994-01-19 1994-01-19 Dispositif d'expansion et de compression d'impulsions laser a reseau unique Withdrawn EP0742912A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
PCT/US1994/000704 WO1995020178A1 (fr) 1992-11-05 1994-01-19 Dispositif d'expansion et de compression d'impulsions laser a reseau unique
CA002179268A CA2179268A1 (fr) 1992-11-05 1994-01-19 Dispositif d'expansion et de compression d'impulsions laser a reseau unique

Publications (1)

Publication Number Publication Date
EP0742912A1 true EP0742912A1 (fr) 1996-11-20

Family

ID=4158424

Family Applications (1)

Application Number Title Priority Date Filing Date
EP94909474A Withdrawn EP0742912A1 (fr) 1994-01-19 1994-01-19 Dispositif d'expansion et de compression d'impulsions laser a reseau unique

Country Status (2)

Country Link
EP (1) EP0742912A1 (fr)
JP (1) JPH09508217A (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7486705B2 (en) 2004-03-31 2009-02-03 Imra America, Inc. Femtosecond laser processing system with process parameters, controls and feedback
US7684450B2 (en) * 2004-12-20 2010-03-23 Imra America, Inc. Pulsed laser source with adjustable grating compressor
JP5637669B2 (ja) 2009-09-01 2014-12-10 浜松ホトニクス株式会社 パルス幅変換装置および光増幅システム
JP5524381B2 (ja) * 2013-03-29 2014-06-18 浜松ホトニクス株式会社 パルス幅変換装置および光増幅システム

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9520178A1 *

Also Published As

Publication number Publication date
JPH09508217A (ja) 1997-08-19

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