Stretcher and compressor design for the Apollon 10

Stretcher and compressor design for the Apollon 10 P ILE laser facility Loïc Le Gat* 1, 2 and Catherine Le Blanc 2 1 Institut de la Lumière Extrême, CNRS, Ecole Polytechnique, ENSTA Paris Tech, Institut d’Optique, Univ Paris-Sud, Palaiseau Cedex, France 2 Laboratoire pour l’Utilisation des Lasers Intenses - Ecole Polytechnique, 91128 Palaiseau, France *Loic. legat@polytechnique. edu ICUIL 2010 Conference September 26 - October 1 Watkins Glen, New York Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 1

Outline Introduction to the ILE facility Stretcher design study Compressor design study Spectral Phase Management Conclusion and perspective Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 2

Introduction to the ILE facility Amplifiers Stretcher KHz Ti: Sa 25 fs @ 800 nm 1. 5 m. J synchronized Spectral broadening < 10 fs @ 800 nm 100 µJ, k. Hz Front End Yb: KYW Diode pumped 2 ns, 2 m. J @ 1030 nm Amplis Yb: KGW Yb: YAG Diode pumped 2 J @ 1030 nm >10 Hz OPCPA 10 Ampli 0 2 J /1 Hz Ampli 1 « LASERIX » 50 J /0. 1 Hz Ampli 2 600 J -1 shot/mn Nd YAG 6 J/1 Hz Nd Glass 100 J/0. 1 Hz Nd Glass 1. 5 KJ – 1 tr/mn LBO/BBO “ 10 fs“ Compression and SHG 1 à 100 ps 1 J @ 515 nm >10 Hz (80 nm FWHM) @ 800 nm 100 m. J 180 mm Compressor 150 J / 15 fs @1 shot/mn 10 PW G 4 250 J “ 15 fs” (65 nm FWHM) G 1 400 mm G 2 G 3 Grating size : 910 x 455 mm Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 3

Stretcher design study Stretcher specifications: • Spectral bandwidth acceptance: 700 -900 nm • Only reflective optics can be used • High transmission efficiency • Low temporal and spatial aberrations are required • High stretching ratio = 13 ps/nm • The size of the optics is a constraint Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 4

Single grating stretcher: scheme • Distance grating – center of curvature linked to the stretching ratio. • Roof mirror for a second pass. Top view 1000 mm Convexe mirror R 500 Concave mirror R 1000 Grating Center of curvature 275 mm 500 mm x Roof mirrors Z (optical axis) y 800 nm beam Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 5

Spatial characteristics of the output beam: Spot diagram and aberrations Strehl ratio = 0. 17 2000 1500 1000 Lateral aberrations (µm) 12. 8 mm 3. 4 mm 500 Airy disk = 200 µm 0 -1. 5 -1 -0. 5 0 0. 5 1 1. 5 -500 Pupil position (AU) 350 Spot diagram at the single grating 300 stretcher output 250 Spot diagram at the stretcher output, after a perfect focal lens (f 1000) 200 150 Vertical aberrations (µm) x 100 Point Spread Function 50 -1. 5 -1 0 -0. 5 -50 0 0. 5 -100 -150 Pupil position (AU) Apollon 1 1. 5 y Blue = 800 nm Green = 700 nm Red = 900 nm Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 6

Increasing the radii in the afocal system to reduce aberrations = increasing the ratio: For a R 2000 concave mirror and a R 1000 convex one: Airy disk 200 µm 10 mm Blue = 800 nm Green = 700 nm Red = 900 nm x Spot diagram at the output of the stretcher y Spot diagram after a perfect focal lens (f 1000) Aberrations 50 times lower Concave mirror is a Φ 800 mm (instead of Φ 400 for a R 1000) !! Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 7

Two gratings stretcher: scheme • One grating is placed on the center of curvature. • Stretching ratio related to the distance between the 2 gratings 1000 mm Grating 1 487 mm Center of curvature 500 mm Grating 2 Roof mirror 2 x Roof mirror 1 Z (optical axis) Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 y 28/09/2010 8

Spatial characteristics of the output beam: Spot diagram and aberrations Strehl ratio = 0. 91 10 mm Spot diagram at the output of the two gratings stretcher x y Airy disk : Ø 200 µm Point Spread Function Spot diagram after a perfect focal lens (f 1000) Apollon Blue = 800 nm Green = 700 nm Red = 900 nm Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 9

Conclusion • A two gratings design reduces spatial aberrations • Alignment procedure is more complicated • Vertical chirp improved by replacing the second-pass roof mirror by a corner cube Concave mirror Convex mirror Grating 1 200 mm 400 mm 70 mm 280 mm Grating 2 Roof mirror 200 mm Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 10

Compressor design Compressor specifications: • Pulse to recompress: – 250 J of input energy, 15 fs output, 65 nm @800 nm (stretched with 13 ps/mm) • Gold coating: max fluence on the grating = 150 m. J/cm² • Beam size Φ 400 mm • 4 ultra-wide monolithic gratings (Livermore gratings 910 x 455 mm²) Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 11

Several cases studied 1200 mm 1400 mm 1600 gv/mm 1740 gv/mm 1200 mm 1400 mm • 15° and 35° of deviation (difference angle of incidence – diffracted angle) 1200 gv/mm • Densities studied: 1200, 1480, 1600 and 1740 gv/mm 1090 mm 1200 gv/mm • 15° leads to geometrical issues 910 mm 1480 gv/mm 910 mm y Best solution !! x Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 Z (optical axis) 28/09/2010 12

Livermore gold gratings specifications 65 % of transmission expected for the 4 gratings Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 13

4 gratings compressor: calculation of the transmited spectrum for a 400 mm diameter beam size Input spectrum Compressor spectral transmission FWHM spectrum : 65 nm Full transmitted wavelength : 754 nm to 842 nm Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 14

Compressor characteristics 400 mm Spot diagram at the output of the compressor x • • • y Four gratings configuration (in line) Grating size: 910 x 455 mm² Grating density: 1480 gv/mm Angle of incidence: 56° Distance between gratings = 950 mm / stretching ratio = 13 ps/mm Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 15

Misalignment study: X tilt / Z tilt of the 1 st grating • • Rotation of the first grating of 0. 1° around the x axis (1. 7 mrad) horizontal dispersion of 127µm Blue = 800 nm Green = 700 nm Red = 900 nm 127 µm Spot diagram at the output of the compressor, after a perfect focal lens (f 1000) • Z tilt (parallel to the grating grooves) on the first grating of 0. 1° (1. 7 mrad) vertical dispersion of 226µm (Y tilt is twice less): 226 µm Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 Spot diagram at the output of the compressor, after a perfect focal lens (f 1000) 28/09/2010 16

Spectral phase management Study and optimization of the stretcher specifications: • First step : stretcher and compressor gratings have 1480 gv/mm Compressor charac. : • 1480 gv/mm • incidence = 56° • Zc = 950 mm Residual phase 0. 00 700. 00 750. 00 800. 00 Pulse duration 850. 00 1. 00 900. 00 Intensity (AU) Phase (rad) -0. 05 -0. 10 -0. 15 15 fs 0. 50 -0. 25 Wavelength (nm) Apollon 0. 00 4. 00 E-13 Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 4. 50 E-13 Time (s) 5. 00 E-13 28/09/2010 17

Materials dispersion compensation • System stretcher – amplifiers – compressor with 1480 gv/mm gratings • The amplification chain uses: Calcite, Silicium, Ti: Saph, etc… Optimized stretcher charac. : • 1480 gv/mm • incidence = 56. 67° • Zc = 960. 57 mm Output pulse duration 1. 00 Residual phase Phase (rad) 0. 00 700. 00 -3. 00 750. 00 800. 00 -6. 00 850. 00 900. 00 Intensity (AU) 3. 00 0. 50 -9. 00 -12. 00 -15. 00 -18. 00 Wavelength (nm) Apollon 0. 00 2. 00 E-13 3. 00 E-13 Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 4. 00 E-13 5. 00 E-13 Time (s) 6. 00 E-13 7. 00 E-13 28/09/2010 18

Changing the number of grooves: compensate the dispersion Optimized stretcher charac. : • 1429 gv/mm • incidence = 50. 13° • Zc = 1160 mm Output pulse duration Residual phase 1. 00 2. 00 1. 60 Intensity (AU) 1. 20 Phase (rad) 0. 80 0. 40 0. 00 700. 00 -0. 40 750. 00 800. 00 850. 00 15. 9 fs 0. 50 900. 00 -0. 80 -1. 20 0. 00 3. 00 E-13 -1. 60 4. 00 E-13 5. 00 E-13 6. 00 E-13 Time (s) -2. 00 Wavelength (nm) Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 19

Best compromise: 1450 gv/mm Optimized stretcher charac. : • 1450 gv/mm • incidence = 55. 4° • Zc = 974 mm Output pulse duration 1. 00 Residual phase 1. 00 750. 00 800. 00 -2. 00 Phase (rad) 850. 00 900. 00 Intensity (AU) 0. 00 700. 00 -1. 00 -3. 00 -4. 00 0. 50 -5. 00 -6. 00 -7. 00 -8. 00 -9. 00 Wavelength (nm) 0. 00 3. 00 E-13 4. 00 E-13 5. 00 E-13 6. 00 E-13 Time (s) Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 20

Phase and duration for a 30 fs input pulse • The software is now able to suppress the phase along the whole spectrum 0. 40 1. 00 0. 80 0. 30 30. 9 fs 0. 10 0. 00 750. 00 -0. 10 770. 00 790. 00 810. 00 830. 00 850. 00 Intensity (AU) Phase (rad) 0. 20 0. 60 0. 40 0. 20 -0. 30 -0. 40 Wavelength (nm) Apollon 0. 00 8. 00 E-13 8. 50 E-13 Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 9. 00 E-13 Time (s) 9. 50 E-13 1. 00 E-12 28/09/2010 21

Conclusion • By decreasing the number of grooves in the stretcher, we can: – Manage more dispersive materials in the amplification chain – Compensate part of material dispersion • The residual phase has to be compensated by a setup like a Dazzler to allow good recompression Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 22

Conclusion and perspective • Stretcher and compressor have been dimensioned for a 15 fs pulse • Residual spectral phase still exists but should be actively controled by a Dazzler – Such pulse duration represents a challenge for the ILE project • To be done: – – Stretcher will be installed in 2011 Livermore gold gratings will be received in 6 months Compressor in 2013 Collaboration projects to increase the grating damage threshold Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 23

Thank you for your attention ! Apollon Loïc LE GAT – ICUIL, Watkins Glen, NY, 2010 28/09/2010 24