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Orbital angular momentum in photon-photon scattering

Orbital angular momentum in photon-photon scattering. Ramy Aboushelbaya Prof. Peter Norreys. Photon-photon scattering. Maxwell’s electromagnetic field in the vacuum Vacuum wave equation Lagrangian quadratic in fields Wave equation linear in fields

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Orbital angular momentum in photon-photon scattering

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  1. Orbital angular momentum in photon-photon scattering Ramy Aboushelbaya Prof. Peter Norreys

  2. Photon-photon scattering • Maxwell’s electromagnetic field in the vacuum • Vacuum wave equation • Lagrangian quadratic in fields Wave equation linear in fields • It would seem that scattering between photons is impossible Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  3. Photon-photon scattering • Quantum electrodynamics would beg to differ • The Euler-Heisenberg Lagrangian • Lagrangian is quartic in fields Wave equation cubic in fields Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  4. Photon-photon scattering Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  5. Photon-photon scattering • 3 High intensity lasers interact, new photons are generated Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  6. Photon-photon scattering • A new hope • Predicted number of photons per shot is very small compared to background noise (100s of generated photons per shot) • No such thing as a perfect vacuum ⟹ Compton scattering • We need to find a needle in a haystack Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  7. A primer on the OAM of light • Laguerre-Gaussian modes are a class of solutions to the paraxial wave equation Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  8. A primer on the OAM of light : Spin • Spin is related to polarization • Only two spin states are allowed • Wavefront can still be planar Transverse phase Transverse intensity Wavefront Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  9. A primer on the OAM of light : OAM Phase Intensity Wavefront L=2 Pasta • Unlike Spin, OAM can take arbitrary integer values • OAM is even defined at a single-photon level Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  10. A primer on the OAM of light Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  11. OAM in photon-photon scattering • Problem: Solving Euler-Heisenberg Lagrangian with LG modes is difficult • Solution: Use OAM plane wave-analogues • Plane wave decomposition simplifies calculations • Conservation of angular momentum creates an additional signature Plane wave Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  12. OAM in photon-photon scattering Incoming beam at , L=l Generated photons at , L=-l • Main beam split into 3 • Generated photons have a unique frequency and OAM signature • The OAM measurement can improve SNR by 25 dB [A. Nicolas et al. 2015] Incoming beams at OAM filter Bandpass filter Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  13. OAM in photon-photon scattering • Predicted number of generated photons • For an 800 nm, 10 PW system, ~100 photons are generated per shot • Single photon detectors + OAM filtering techniques make detection possible Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  14. Future Work • Optimize OAM mode converters • Optimize the single-photon detection system • Test it on a high-power system to make sure it can be isolated from stray background light • Plan the main experiment once all the different components are optimized Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  15. Collaborators • University of Oxford: P. A. Norreys, A. F. Savin, M. Mayr, B. Spiers, R. Wang • University of Gothenburg: M. Marklund • Central Laser Facility: K. Glize, R. M. G. M. Trines, R. Bingham, J. Collier Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  16. Thank you Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  17. Appendix I: Generating OAM • How do we make high-intensity beams with OAM Spiral Phase Plates (SPP) • A transmission SPP was built and tested on the main beam of TA2 of the Astra Laser Main beam focal spot showcasing characteristic “donut” shape Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  18. Appendix II: Atlas Experiment Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  19. Appendix III : OAM for single-photons Paraxial approximation Using previous definition for angular momentum [G. Calvo et al., PRA 73, 013805 (2006)] Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

  20. Appendix III : OAM for single-photons Orbital Angular Momentum in photon-photon scattering - Ramy Aboushelbaya

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