High-energy OPCPA at 3.9 microns

Transcription

1 High-energy OPCPA at 3.9 microns Audrius Pugžlys Photonics Institute, Vienna University of Technology, Austria 100 µm 10 µm Far-IR THz Mid-IR

2 Motivation why mid IR? Why femtosecond? Why high energy? Historic and basic concepts of O(PC)PA Source of 200-GW mid-ir pulses: design and performance Examples of applications: High harmonic generation (HHG) Incoherent X-ray generation Filamentation and lasing from a filament

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4 Short-wavelength driving pulse (e.g. 800 nm) I = W/cm 2 E 0 ~1 kv/nm Force acting on an electron: F t = qe 0 cos (ωt) E k (t) I 2 Long-wavelength driving pulse (e.g nm) 5 E k 25! Recombination: h max = I p + E k max Longer wavelength drivers: Higher energy x-ray photons Extremely short (attosecond) X-ray pulses

5 OPA: Some general aspects

6 Source: Conventional lasers: discrete spectral coverage Lack of broadband laser media in Mid-IR: vibrational instead of electronic transitions Parametric amplifiers: continuous frequency tunability FIR lasers QCLs Excimer lasers 100 µm 10 µm Far-IR THz Mid-IR Free electron lasers Synchrotrons

7 Parametric amplification a method of exciting and amplifying electromagnetic oscillations when power amplification results from the expenditure of energy on the periodic variation of the magnitude of a (non-linear) reactance parameter (C, L) ω i = ω p ω s (ω p = ω s + ω i ) Proposed 1931, practical realization 1950 s (L.I. Mandel shtam, N. D. Papaleksi) PROCEEDINGS OF THE IRE, 1962 IRE - Institute of Radio Engineers

8 Optical Parametric Amplification (OPA) s p (1) (2) (3) P i = ij Ej + ijkej E k + ijklej E k E l + (2) s i p High single pass gain: G = I s out in I ~e2 L s (2)2 I p 2 ~ n i n s n p i s Typical gain up to 10 6! ω s ω i ω p k s k i k p k i k s p s k p k i k s i k p

9 No broadband laser materials in mid-ir Optical Parametric Amplification Heat Fixed Long storage time Wide tuning range: "0" < ω s < ω p Broad gain bandwidth No heat Now storage

10 Choice of nonlinear material Wavelength, m Frequency conversion crystal: Transparency range Phasematching bandwidth Nonlinear gain coefficient ( (2) ) KTA d eff = 2 pm/v signal idler pump degeneracy s i Pump source: Wavelength Pulse energy Pulse duration Repetition rate Mid-IR Internal Angle, deg

11 CPA (Chirped Pulse Amplification) I = E τ πr 2 D. Strickland and G. Mourou, Opt. Commun. 56, 219 (1985) OPCPA = OPA +CPA Seed pulse Stretching, shaping, timing Pump pulse OPA Compressor Output pulse OPCPA matching pulse durations of pump and seed A. Dubietis, G. Jonušauskas, and A. Piskarskas, Opt. Commun. 88, 437 (1992) I.N. Ross, et al., Opt. Commun. 144, 125 (1997).

12 3.9-µm OPCPA

13 KEY FEATURES Combination of fs OPA and ps OPCPA 200-fs Yb:CaF2 CPA and 90-ps Nd: YAG pump systems All-optical synchronization Yb:KGW master oscillator Dispersion management: Stretching Signal, compressing Idler Management of optical damage Brewster-cut KTA NLO crystals in OPCPA M 2 =1.22 Andriukaitis et al, Opt.Lett. 36, 2755 (2011)

14 OPA Seed: nm Amplification of Signal pulses 1.00 Normalized intensity OPA Wavelength, nm

15 Generating pump in parallel 1.0 Signal ps Time delay, ps

16 OPCPA 4f imaging of pump Brewster oriented KTA Last stage non-collinear

17 Stretching / Compression 840 Wavelength [nm] Delay [fs] stretching signal / compressing idler signal and the idler pulses are phase conjugate there is a considerable uncompensated 3 rd order phase DAZZLER not enough of 3 rd order dispersion solution - GRISMS

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19 3.9-µm OPCPA in action: HHG

20 Laser-like X-ray emission I Xray k = 0 L 2 k = k waveguide k atoms + k electrons waveguide Popmintchev et al. PNAS 106, (2009); Nature Photonics 4, 822 (2010); Chen et al., PRL 105, (2010). Can be controlled by gas pressure

21 Broad coherent soft X-ray continuum >0.7 kev >1.3 kev Generated X-ray flux 10 6 ph/s in 1% bw at 1 kev Spatially coherent laser-like beam of kev X-ray continuum Far field beam profile Young s double-slit diffraction T. Popmitchev, et al., Science 8 June 2012:

22 3.9-µm OPCPA in action: Incoherent X-rays:

23 X-ray plasma source concept Femtosecond laser pulse driven X-ray tube Experimental Setup In Zamponi et al., App. Phys. A (2009)

24 X-ray plasma source scaling Ka Photons per shot in solid angle =3.9mm t=80fs d FWHM =21 m =59 =3.9mm t=80fs d FWHM =21 m = Peak intensity, W/cm 2 =0.8mm t=50fs d FWHM =2.6 m =45 E k (t) I 2 K flux With 3.9-µm driver as compared to 800 nm : for the same K flux 100 times lower intensity! Record flux: 25 time higher K flux per shot! V. Juve et al., Nature Photonics, 2014

25 3.9-µm OPCPA in action: Filaments

26 Femtosecond Filamentation Laser ignited plasma channels - light source for atmospheric sensing Filament: Balance between Kerr Self-focusing & Plasma defocusing: medium forms a lens which keeps the laser beam being focused while plasma defocuses n Kerr n2i 0 n plasma N 0 n( I) n0 n2i e I ( r) n( r) Kerr lens r

27 NL ( t) n2i( t) n( t) n0 n2i( t) d ( t) NL ( t) dt Self-phase modulation leads to spectral broadening of intense pulses

28 Spectral intensity input N 2 O 2 Good news for atmospheric sensing: Spectral content of continuum in N 2 is similar to air Covered spectral range: nm cm wavelength, m Filament plasma hot electrons impact excitation of N 2 population inversion Mirror-less N 2 filament laser Performance of the filament N 2 laser: Optical to optical efficiency ~5x10-4 few µj pulses at few mj pump Beam divergence: ~1.6 mrad Pulse duration: <1 ns Kartashov et al., Opt. Lett. 38, 3194 (2013).

29 Table top sources: Primary: high-intensity mid-ir pulses from OPCPA : >20mJ, 80fs, 4µm Secondary: Sub-nm coherent X-rays High-flux hard incoherent X-rays mid-ir super-continuum filament laser

30 1-kHz pump sources: 200-mJ, 100-ps 100-mJ, 200-fs from 10 6 phot/s to ~10 8 phot/s in HHG; from 10 9 phot/s to ~10 11 phot/s in incoherent X-rays; Longer mid-ir wavelengths (>6 µm)

31 Skirmantas Ališauskas, Giedrius Andriukaitis, Tadas Balčiūnas, Andrius Baltuška, Daniil Kartashov, Pavel Malevich, Oliver Muecke JILA, USA Tenio Popmintchev Ming-Chang Chen Dimitar Popmintchev Margaret M. Murnane Henry C. Kapteyn VU, LT Audrius Zaukevičius Gintaras Valiulis Valerijus Smilgevičius Algis Piskarskas U. Geneva, CH Massimo Petrarca Pierre Bejot Jerome Kasparian MBI Berlin, DE Jannick Weisshaupt Shian Ku Vincent Juvé Marcel Holtz Micheal Woerner Thomas Elsaesser NTU Singapore, SG Wenn Jing Lai Lihao Tan PohBoon Phua MSU, RU Alexander Voronin Alexander Mitrofanov Alexander Lanin Dmitrij Sidorov Andrei Fedotov Aleksei Zheltikov Ekspla, LT Kirilas Michailovas Andrejus Michailovas Jonas Kolenda LightConversion, LT Linas Giniūnas Jonas Pocius, Paulius Mišeikis Romualdas Danielius FastLite, FR Nicolas Forget Pascal Tournois

32 Die Österreichische Forschungsförderungsgesellschaft mbh EU