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Development and application of plasma-waveguide based soft x-ray lasers

Development and application of plasma-waveguide based soft x-ray lasers. Core members of the experimental group. Prof. Jyhpyng Wang ( 汪治平 ), Academia Sinica (Taiwan) Prof. Szu-yuan Chen ( 陳賜原 ), Academia Sinica (Taiwan) Prof. Jiunn-Yuan Lin ( 林俊元 ) , National Chung-Cheng Univ.

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Development and application of plasma-waveguide based soft x-ray lasers

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  1. Development and application of plasma-waveguide based soft x-ray lasers Core members of the experimental group Prof. Jyhpyng Wang (汪治平), Academia Sinica (Taiwan) Prof. Szu-yuan Chen (陳賜原), Academia Sinica (Taiwan) Prof. Jiunn-Yuan Lin (林俊元),National Chung-Cheng Univ. Prof. Hsu-Hsin Chu (朱旭新), National Central Univ. Institute of Atomic and Molecular Sciences Academia Sinica, Taiwan National Central University, Taiwan

  2. Outline • Introduction to soft x-ray lasers • Soft x-ray lasers pumped by optical-field ionization • Fabrication of transient plasma waveguides • Plasma-waveguide based soft x-ray lasers • Injection-seeding with high-harmonic generation • X-ray digital holographic microscopy

  3. Introduction to soft x-ray lasers

  4. X-ray lasers powered by nuclear bomb for “Star Wars” 1983

  5. Energy levels of soft x-ray lasers He-Ne laser Ne-like ions: Ar8+, Ti12+, Fe16+ 3p lifetime = ~3 ps lasing 3s collisional excitation (~200 eV) fast relaxation 2p

  6. Early pumping scheme line-focused high-power laser pulse solid target solid target x-ray lasing collisional excitation in hot plasma

  7. Pulse sequence for effective excitation pump pulse plasma generation target plasma heating time delay to reduce plasma density gradient by diffusion

  8. Grazing-angle pumping scheme plasma generating pulse pumping at grazing angle solid target solid target J.J. Rocca et al. “Saturated 13.2 nm high-repetition-rate laser in nicke-llike cadmium” Opt. Lett. 30, 2581 (2005).

  9. Soft x-ray lasers pumped by optical-field ionization

  10. Optical-field ionization multiphoton ionization tunneling ionization above-threshold ionization above-threshold ionization heating appearance intensity for 1+ ion (=1 m) Xe: 8.71013 W/cm2 He: 1.51015 W/cm2

  11. Pumping by optical-fieldionization electrons gain energy electron-ion collisional excitation population inversion and lasing ionization to specific ion stage tunneling ionization above-threshold-ionization heating electron velocity time laser field

  12. Ionization of Xe as a function of intensity When a laser pulse with appropriate laser intensity is incident into a gas jet, atoms in the jet can be ionized to specific ion species through optical-field-ionization.

  13. Energy levels of soft x-ray lasers

  14. CCD grating Longitudinally pumped optical-field-ionizationx-ray lasers l gas jet • advantages: • high efficiency • excellent beam profile • no debris pump pulse nozzle • problem: • ionization defocusing higher refractive index lower refractive index pump pulse defocusing quickly reduces intensity

  15. Tomography of laser-plasma interaction machining-pulse intensity nanoseconds after

  16. Setup of the machining beam for tomographic measurements function of the knife-edge:setting the interaction length pump pulse focal spot: 20 m1.3 mm variable position knife-edge cylindrical lens pair gas jet machining pulse Phys. Rev. Lett. 96, 095001 (2006)

  17. Tomography of x-ray lasing 7 machining pulse: 30-mJ, 45-fs, 6-ns before pump pulse. 1.11018 cm-3 6 8.31017 cm-3 6.61017 cm-3 5 width of the line focus: 20 m 4 pump pulse: 240-mJ, 45-fs, focused to 10-m diameter. 3 2 1 0 Simulation shows the pump beam diverges quickly due to ionization defocusing. As a result, the x-ray output is limited by the absorption from the weakly pumped medium at the tail. Phys. Rev. A 74, 023804 (2006)

  18. How to make an all-optical plasma waveguide?

  19. Plasma-waveguide formation from a line focus ignitor ignitor heater axicon line focus creating seed electrons line focus heating up and generating more electrons shock expansion & collisional ionization heater forming a plasma waveguide Phys. Plasmas 11, L21 (2004)

  20. Laser-drilled plasma waveguide length > 1.2 cm density variation < 20% electron density profile ignitor: 15 mJ, 55 fs heater: 85 mJ, 80 ps (1.1 ns delay) probe: 1.2 ns after heater Phys.of Plasma 11, L21 (2004)

  21. Unexpected immunity to ionization defocusing ignitor + heater pulses (1) pump pulse in waveguide (2) radial electron density profile pump pulse: 45 fs, 235 mJ ignitor: 45 fs, 45 mJ heater: 80 ps, 225 mJ ignitor-heater separation: 200 ps hearer-pump delay: 2.5 ns atom density: 1.6×1019 cm-3 (2) (1) A uniform pure-Kr plasma waveguide of 9-mm length is produced with the axicon-ignitor-heater scheme. The guided beam size is smaller than 15 m.

  22. Plasma-waveguide based soft x-ray lasers

  23. Atom-density dependence for Ni-like Kr lasing at 32.8 nm 400-fold enhancement by waveguide linear growth (reaching saturation) without waveguide pump pulse: 45 fs, 235 mJ focal position: 2.75 mm pump polarization: circular pure Kr waveguide pump pulse: 45 fs, 235 mJ pump polarization: circular focal position: 500 mm ignitor: 45 fs, 45 mJ heater: 80 ps, 225 mJ ignitor-heater separation: 200 ps heater-pump delay: 2.5 ns exponential growth trade-off between larger gain coefficient and more severe ionization defocusing Phys. Rev. Lett. 99, 063904 (2007)

  24. Pump-power dependence for Ni-like Kr lasing at 32.8 nm linear growth (reaching saturation) pure Kr waveguide pump pulse: 45 fs, 235 mJ pump polarization: circular focal position: 500 mm ignitor: 45 fs, 45 mJ heater: 80 ps, 225 mJ ignitor-heater separation: 200 ps heater-pump delay: 2.5 ns 400 folds number of photon/pulse exponential growth optimized lasing without waveguide pump energy (mJ) Phys. Rev. Lett. 99, 063904 (2007)

  25. Reduced divergence without waveguide with waveguide Phys. Rev. Lett. 99, 063904 (2007)

  26. Multi-line lasing for Ne-like Ar raw image recorded by x-ray spectrometer energy diagram of Ne-like Ar 46.9 nm 46.5 nm 45.1 nm 46.9 nm 45.1 nm 46.5 nm intensity (arb. units) Phys. Rev. A 76, 053817 (2007)

  27. Multi-species parallel x-ray lasing raw image recorded by flat-field spectrometer Kr/Ar mixed-gas waveguide pump pulse: 45 fs, 240 mJ pump polarization: circular ignitor: 45 fs, 45 mJ heater: 160 ps, 220 mJ Kr atom density: 9.1×1018 cm-3 Ar atom density: 1.2×1019 cm-3 ignitor-heater separation: 200 ps hearer-pump delay: 1.5 ns gas mixture Kr : Ar = 0.9 : 1.2 Phys. Rev. A 76, 053817 (2007)

  28. Injection-seeding with high-harmonic generation

  29. Experimental set-up parabolic mirror x-ray laser pump axicon x-ray mirror amplified x-ray Kr jet Ar jet high harmonic seed bored lens pump for high harmonic generation parabolic mirror pulses for waveguide fabrication (ignitor & heater) pulse timing diagram time

  30. Spectrum of the soft x-ray lasers parameters of HHG seed: high harmonic seed gas: argon atom density: 7.1×1018 cm-3 pump energy: 3.8 mJ pump duration: 360 fs focal position: 1250 mm 25th harmonic unseeded laser parameters of x-ray amplifier: gas: krypton atom density: 1.6×1019 cm-3 pump pulse: 38 fs, 235 mJ ignitor: 38 fs, 45 mJ heater: 160 ps, 270 mJ ignitor-heater separation: 200 ps heater-pump delay: 2.5 ns seeded laser seed-amplifier pump delay: 2 ps Maximizing the 25th HHG output is achieved by adjusting the pump beam size, pump energy, focal position, and atom density. The spectral overlap between HHG seed and amplifier is done by adjusting the chirp of HHG pump pulse.

  31. Angular distribution(with waveguide) high harmonic seed parameters of HHG seed: gas: argon atom density: 7.1×1018 cm-3 pump energy: 3.8 mJ pump duration: 360 fs focal position: 1250 mm unseeded laser parameters of x-ray amplifier: gas: krypton atom density: 1.6×1019 cm-3 pump pulse: 38 fs, 235 mJ ignitor: 38 fs, 45 mJ heater: 160 ps, 270 mJ ignitor-heater separation: 200 ps heater-pump delay: 2.5 ns seeded laser seed-amplifier pump delay: 2 ps fluctuations of beam pointing and angular distribution ~0.13 mrad With seeding the divergence of the x-ray laser is greatly reduced from 4.5 mrad to 1.1 mrad, which is about the same as that of the HHG seed. With the waveguide-based soft-x-ray amplifier, the HHG seed is amplified by a factor of 104.

  32. Controlled polarization detector x-ray laser polarization analyzer (Is : Ip > 19) unseeded laser high harmonic seed seeded laser The x-ray analyzer consists of two multilayer x-ray mirrors which are strongly polarization dependent. The polarization of seeded soft-x-ray laser follows that of the HHG seed.

  33. Comparingour x-ray laser with synchrotron radiation spectral brightness (photon/sec/mm2/mrad2) for x-ray laser (HHG seeding) NSRRC (Taiwan) 100 ps 200 fs* pulse duration 10 Hz 106 Hz repetition rate wavelength discrete set tunable average spectral brightness at 32.8 nm 9.81012 6.61014 peak spectral brightness at 32.8 nm 7.91014 3.31026 * assuming the pulse duration is limited by bandwidth

  34. X-ray digital holographic microscopy

  35. Working principle focused x-ray laser constructed images object focusing mirror CCD camera

  36. Experimental set-up Opt. Lett. 34, 623 (2009)

  37. Image of an AFM tip 10 m SEM image resolution: 0.5 m working distance: 20 cm Opt. Lett. 34, 623 (2009)

  38. Thank you for your attention.

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