Progress in photo cathode laser pulse shaping towards ultimate - PowerPoint PPT Presentation

Progress in photo cathode laser pulse shaping towards ultimate low-emittance beams Experimental progress in infrared shaping & Progress of conversion section design by Christian Koschitzki

Photo Injector Test facility at DESY in Zeuthen (PITZ) acceleration electron p x F x bunch x x p x F x laser cathode x x Pulse should only experience linear distortions Homogeneous ellipsoidal electron bunch results in linear phase space  ultimate low emittance Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 2

Laser Shaping at PITZ > „Generation of flat-top picosecond pulses by coherent pulse stacking in a multicrystal birefringent filter “, Ingo Will & Guido Klemz Optics Express, Vol. 16, Issue 19, pp. 14922-14937 (2008) 1 1 0.8 0.8 OSS Signal (a.u.) OSS Signal (a.u.) 0.6 0.6 0.4 0.4 0.2 0.2 0 0 0 5 10 15 20 25 30 35 0 5 10 15 20 25 30 Time (ps) Time (ps) > Proof of principle demonstrated with IAP system (single SLM -> dual path) at PITZ in 2016 Comparison with simulated e - beam shapes (500pC): similarity in shape 20 @PST.Sc1 Gaussian laser Ellipsoidal laser Flattop laser 10 t (ps) 0 -10 @EMSY -20 -10 -5 0 5 10 x (mm) J. Good et al., Proc. 38 th FEL Conf., WEP006 (2017) Measurement Problems: pointing stability, spectral width and conversion Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 3

Example for the key principles: The spectrograph CCD 4f (Image) SLM CCD 2f Polarizing beamsplitter Waveplate Reflect and reverse Repeat for 2 nd spatial domain optical path Only rectangular shapes because of projection  Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 4

Schematic setup of infrared shaping Spherical Lens Cylindrical Lens Faraday Image Out rotator Waveplate Grating SLM Polarizing BS Volume Bragg Grating Shaper VBG Standard VBG mod. VBG Dove Prism Modified VBG SLM λ -Y Shaper Provides rotational symmetry Output Power: 20W Pharos Rep. Rate: 0.1-1 MHz laser Pulse duration: 0.25 – 15 ps Wavelength: 1030 nm Image Start SLM λ -X Shaper Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 5

Shaping with spectrograph feedback Pharos laser Spectrograph Inverted MZ Interferometer SLM SLM λ -X Shaper Spectrograph Gaussian (unshaped) profile Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 6

3D Measurement with Spectrograph Slit Scan Spectrograph Data  Transverse Slices Slices in λ -X along Y x y λ Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 7

Nonlinear Conversion chi23d.com Input beam Harmonic Pulse (VIS) Pump Pulse (IR) Wavelength: 1030 nm Fourier Limit: 0.211 ps Diameter: 0.25 mm Pulse duration: 30 ps Pulse Energy: 20 µJ Material: BBO Propagation: 2.5 mm BBO Walk Off: 57 mrad  Without angular chirp Efficiency 20%  With angular chirp Efficiency 36% Matched angular chirp: AC = 0.275 mrad per nm Slant angle = 25 deg Animation over 2.5 mm propagation Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 8

Nonlinear Conversion chi23d.com Input beam Harmonic Pulse (VIS) Pump Pulse (IR) Wavelength: 1030 nm Fourier Limit: 0.211 ps Diameter: 0.25 mm Pulse duration: 30 ps Pulse Energy: 20 µJ Material: BBO Propagation: 2.5 mm BBO Walk Off: 57 mrad  Without angular chirp Efficiency 20%  With angular chirp Efficiency 36% 57 mrad * 2.5 mm= 143 micron Matched angular chirp: AC = 0.275 mrad per nm Slant angle = 25 deg Animation over 2.5 mm propagation Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 9

Conversion to Fourth Harmonic f 2 f 1 f 1 +f 2 4 Nonlinearity: E out ~ E in 20 µJ in  2.75 µJ out (14%) 10 µJ in  0.38 µJ out (4%) 𝜄 𝑗𝑜 LBO BBO Broadband Phasematching: Suppression of spectral components due to wavelength dependent phase matching  Compensate with matched angular chirp Spatial Walk Off: Edge Softening due to propagation difference between pump and harmonic beam. Softening in 0.8 mm BBO Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 10

First Conversion Tests and Outlook CCD Image LBO f - 250 Plane f300 f200 f250 f500 f150 f80 4mm Variable Magnification Telescope Image in IR from old Image after first Conversion Image in IR (1030 nm) IAP system in VIS (515 nm) Collaboration with Chiang Mai University Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 11 Thailand by Narupon Chattrapiban

Summary & Outlook > 3D shaping capabilities in IR demonstrated > Image preservation in Second Harmonic shown > Preparing for Fourth Harmonic (UV) experiments (UV Spectrograph) > Investigation of time coordinate using cross correlation > Improved 3D shaping with Volume Bragg Gratings Thank you for your attention Christian Koschitzki | Progress on ELLA2 | 05.09.2018 | Page 12