Fig. 1. General block diagram of the XCELS laser. DKDP_i, nonlinear crystal in intermediate OPCPA; DKDP_0, nonlinear crystal in booster OPCPA; DKDP_1–12, nonlinear crystals in final OPCPAs; GC, grating compressor.
Fig. 2. General view of the building for the XCELS project: frontend (1); intermediate OPCPA (2); pumping zone for wide-aperture OPCPAs (3); booster OPCPA (4); final OPCPAs (5); transport telescopes and optical compressors (6); main target chamber (7); experimental laboratories (8).
Fig. 3. Schematic diagram of the frontend. MO, master oscillator; NF, nonlinear fiber; FA, fiber amplifier; FRA, fiber regenerative amplifier; FSRA, femtosecond regenerative amplifier; DRA, disk regenerative amplifier; DMA, disk multipass amplifier; NA, neodymium amplifier; YA, ytterbium amplifier; WLG, white light generator; FOPA, parametric amplifier; XPW, orthogonal polarization generator; GS, stretcher on diffraction grating; AOPDF, acousto-optical programmable dispersion filter.
Fig. 4. Measured pulse intensity and phase at the output of a parametric amplifier based on a BBO crystal
[46].
Fig. 5. Variants of the optical scheme of the intermediate OPCPA when pumped by a lamp-pumped neodymium glass rod laser (a), a lamp-pumped neodymium glass active-mirror laser (b), (c) and two diode-pumped Yb:YAG cryogenic disk lasers (d), (e) (see also Table 3).
Fig. 6. Signal spectra at the input (black curves) and at the output (red curves) of OPCPA and the shape of the pump pulse (green curves) for the five options shown in Figure 5 and Table 3. The insets show the dependence of the energy W on the thickness L of the DKDP crystal. The dashed curves in (b), (d) and (e) show the corresponding dependence for the first OPCPA cascade.
Fig. 7. Optical layout of one channel of the UFL-2M setup
[70].
Fig. 8. Booster OPCPA. ARE, auxiliary removable equipment (filters, diaphragms, screens); TM, a mirror on the translator; RM, a rotating mirror, used for alignment and phasing of channels (see Sections 2.8 and 2.9). In the lower left corner there is a diagram of the beam division into 12 replicas (the green square is the pump beam cross-section, the red circle is the signal beam cross-section); one telescope out of twelve is shown.
Fig. 9. Signal spectra at the input (black curve) and output (red curve) of OPCPA and the pump pulse shape (green curve) for booster OPCPA. The inset shows the dependence of the energy W on the thickness L of the DKDP crystal.
Fig. 10. Signal spectra at the input (black curve) and output (red curve) of OPCPA and the pump pulse shape (green curve) for the final OPCPA. The inset shows the dependence of the energy W on the thickness L of the DKDP crystal.
Fig. 11. Expanding telescope and chirped pulse compressor (sizes of beam and gratings G1–G4 are shown to scale), as well as a 17-fs Fourier-transform-limited output pulse.
Fig. 12. Focusing geometry in the main target chamber. For clarity, the parabolic mirror of beam No. 6 is shown transparent, and the input beams are shown for only two channels: the beam input of channel No. 1 coincides with the output of channel No. 7, and vice versa.
Fig. 13. Dependence of the maximum intensity achieved in the focal region on the number of focused beams for ideal phasing (σ = 0) and for different values of the standard deviation σ of the phase mismatch between the beams.
Fig. 14. Scheme of spatial and temporal overlapping of beams at the main focus. TM, mirror on the translator; RM, rotating mirror; DM, deformable mirror; PM, parabolic mirror; WFS, wavefront sensor; QP, quadrature photodiode; FI, focus image; FPM, fiber-optic phase modulator; PD, photodiode; DU, diagnostic unit; RDU, retro-diagnostic unit; MO, microscope objective.
Fig. 15. Illustration of blade alignment.
Fig. 16. Overlapping of counterpropagating channels.
Fig. 17. Adjacent channels overlapping.
Fig. 18. Schemes of post-compression (a), post-compression with spectral filtering (b) and frequency doubling with post-compression (c). NE, nonlinear element; CM, chirped mirror; R(
) is a mirror whose reflection coefficient has a dip in the center of the spectral band; the dichroic mirrors shown in blue reflect the second harmonic of the pulse and transmit the first harmonic.
Fig. 19. Spectra (a) and pulse intensity in linear (b) and logarithmic (c) scales at the grating compressor output (red curves), after post-compression (green curves) (see Figure 18(a)) and after post-compression with spectral filtering (blue curves) (see Figure 18(b)).
Fig. 20. Pulses of the fundamental harmonic (red curves), the second harmonic (blue curves) and the second harmonic after post-compression (green curves).
Fig. 21. The number of laser pulses that are needed in the experimental schemes proposed in Refs. [
118–
156]. The blue color shows the minimum required number of laser pulses, while the cyan color shows the maximum number of pulses.
|
---|
| XCELSa | SEL-100PW[20–24] | EP-OPAL[25,26] | Gekko-EXA[27,28] | Refs. [29,30] | Ref. [31] |
---|
Number of channels | 12 | 1 | 2 | 1 | 1 | 1 | Peak power, PW | 12 × 50; 12 × 230b | 100 | 2 × 25 | 50 | 100 | 120; 589b | Pulse duration, fs | 20; 3b | >15 | 20 | < 10 | 3 | 8; 1.65b | Pulse energy, J | 12 × 1100 | >1500 | 2 × 500 | 500 | 300 | 971 | Central wavelength, nm | 910 | 925 | 920 | ~1000 | 900 | 900 | Bandwidth, nm | 150 | 210 | 200 | 500 | 600 | 460 | Nonlinear crystal in final OPCPA (deterioration) | DKDP (80%) | DKDP | DKDP (>90%) | DKDP (65%) | LBO | LBO | Pump energy of one channel, J | 5600 | - | - | 6400 | 1000 | 2000 | Chirp pulse duration, ns | 3 | 4 | 1.5 | <1 | 2 | 2 | Beam area at compressor input, cm2 | 66 × 66 | 64 × 64 | 80 × 80 | 80 × 80 | 36 × 36 | 98 × 98 | Area of diffraction gratings, cm2 | 70 × 145 | 70 × 145 | - | - | 50 × 80 | - | Compressor efficiency | 0.66 | 0.67 | - | - | 0.73 | 0.7 |
|
Table 1. Characteristics of the XCELS laser and other 100-PW laser projects.
| Wavelength, | Bandwidth | | Pulse | Beam size, | Repetition |
---|
Key points | nm | (FWHM), nm | Energy, J | duration | cm | rate |
---|
1.1 Pump laser of DKDP_ 0…12 input | 1054 | 0.05–3 | >0.1 | 4 ns | 0.55 (dia) | >2 Hz | 1.2 Pump laser of DKDP_ i input | 1054/1030 | 0.05–3 | >0.1 | 4 ns | 0.55 (dia) | >2 Hz | 1.3 Input of DKDP_i | 910 | 200 | >0.1 | 3 ns | 1 (dia) | 100 Hz | 2.a Pump of DKDP_i | 527 | 1 | 412 | 3.5 ns | 10 | 0.001 Hz | | 527 | 1 | 140 | 3.5/7 ns | | 0.1 Hz | | 515 | 1 | 2 × 87 | 7 ns | | 10 Hz | 2.b Output of DKDP_i | 910 | 150 | 149 | 3 ns | 10 (dia) | 0.001 Hz | | | | 51 | | | 0.1 Hz | | | | 60 | | | 10 Hz | 2.1 Input of DKDP_0 | 910 | 150 | 141 | 3 ns | 30 (dia) | 0.001 Hz | | | | 48 | | | 0.1 Hz | | | | 57 | | | 10 Hz | 3.0 Pump of DKDP_0 | 527 | 1 | 3900 | 3.5 ns | 25 × 25 | 2 shots/day | 3.1–3.12 Pump of DKDP_1…12 | 527 | 1 | 3900 | 3.5 ns | 25 × 25 | 2 shots/day | | | | 5616 | | 30 × 30 | 4.a Output of DKDP_0 | 910 | 150 | 1248 | 3 ns | 27 (dia) | 2 shots/day | 4.1–4.12 Input of DKDP_1…12 | 910 | 150 | 46 | 3 ns | 25 × 25 | 2 shots/day | | | | | | 30 × 30 | 5.1–5.12 Output of DKDP_1…12 | 910 | 150 | 1248 | 3 ns | 25 × 25 | 2 shots/day | | | | 1797 | | 30 × 30 | | 6.a1–6.a12 Compressor input | 910 | 150 | 1145 | 3 ns | 55 × 55 | 2 shots/day | | | | 1669 | | 66 × 66 | | 6.1–6.12 Compressor output | 910 | 150 | 751 | 20 fs | 55 × 55 | 2 shots/day | | | | 1095 | | 66 × 66 | | Auxiliary outputs | | 1.4 | 1056 | 1 | 1 μJ | 1 ns | | 100 kHz | 1.5 | 1030 | 1 | 1 nJ | 1 ps | | 50 MHz | 1.6 | 910 | >200 | 1 mJ | 15 fs | | 1 kHz | 2.2=2.1 | | | | | | | 3.13–3.15 | 1054/527 | | 20,000/14,000 | 3–10 ns | 40 × 40 | 2 shots/day |
|
Table 2. Main parameters at key points of the XCELS laser.
| Figure 5(a) | Figure 5(b) | Figure 5(c) | Figure 5(d) | Figure 5(e) |
---|
Pump | Lamp | Diode |
---|
Pump laser amplifier | Nd:glass rods | Nd:glass active mirrors | Yb:YAG disks | Pump laser prototype | PEARL | Premiumlite GLASS laser | 2 × DiPOLE (two lasers) | Repetition rate, Hz | 0.001 | 0.1 | 10 | SHG outline | Usual | Usual | With pulse | Usual | With pulse | | | | shortening | | shortening | OPCPA outline | Single stage | Two stages | Single | Two stages | Two stages | | | with single | stage | with single | with two | | | 7 ns pump | | 7 ns pump | 7 ns pumps | Pump energy @1
$\omega$
, J | 550 @ 3.5 ns | 260 @ 15 ns | 2 × 150 @ 10 ns | Pump energy @1
$\omega$
and 7 ns, J | - | 200 | 2 × 125 | Pump energy @2
$\omega$
, J | 412 | 160 | 140 | 187.5 | 2 × 87 | Beam diameter, cm | 10 | 4.4 | 5.8 | 4.8 | 4.6 | DKDP(s) length, cm | 8 | 6.8 + 1.9 | 7.1 | 6.9 + 1.9 | 6.8 + 1.9 | Input pulse energy, J | 0.03 | 0.03 | 0.03 | 0.03 | 0.03 | OPCPA efficiencya | 0.36 | 0.34 | 0.36 | 0.35 | 0.35 | Output pulse energya, J | 149 | 54 | 51 | 65 | 60 | Powera after compression, PW | 4.9 | 1.8 | 1.7 | 2.1 | 2.0 |
|
Table 3. Five options of intermediate OPCPA (optical schemes are shown in Figures 5(a)–5(e)).
Parameter | Value |
---|
Input pulse energy, J | 132/54/64b | DKDP thickness, cm | 3.8/4.3/4.3b | Input beam diameter, cm | 27 | Pump beam area, cm2 | 25 × 25 | Pump energy in input beam diameter, J | 3250 | Full pump energy, J | 3900 | OPCPA efficiencya | 0.32 | Beam area at outputs 4.1–4.12, cm2 | 5 × 5 | Beam energya at outputs 4.1–4.12, J | 50 |
|
Table 4. Booster OPCPA parameters. All apertures and energies (except for the total pump energy) refer to the homogeneous region of the beam; total aperture is approximately 20% larger.
Parameter | Value |
---|
Beam area in compressor, cm2 | 55 × 55 | 66 × 66 | Beam area in OPCPA, cm2 | 25 × 25 | 30 × 30 | DKDP thickness, cm | 4.3 | 4.3 | Input pulse energy, J | 46 | 46 | Pump energy in input beam | 3250 | 4680 | diameter, J | | | Full pump energy, J | 3900 | 5616 | OPCPA efficiencya | 0.32 | 0.32 | Output pulse energya, J | 1248 | 1797 |
|
Table 5. Final OPCPA parameters for two options. All apertures and energies (except for the total pump energy) refer to the homogeneous region of the beam; the full aperture is about 20% larger.
Parameter | Value | |
---|
Size of gratings G2 and G3, cm2 | 57 × 101 | 70 × 145 | Groove density, grooves/mm | 1200 | 1200 | Littrow angle, degree | 33.1 | 33.1 | Input pulse bandwidth, nm | 150 | 150 | FTL pulse duration (FWHM)a, fs | 17 | 17 | Output pulse duration (FWHM)a, fs | 20 | 20 | Input pulse duration, ns | 3 | 3 | Compressor efficiency | 0.66 | 0.66 | Beam fluence on grating G1, J/cm2 | 0.265 | 0.265 | Beam fluence on grating G4, J/cm2 | 0.174 | 0.174 | Beam area, cm2 | 55 × 55 | 66 × 66 | Incident angle, degree | 45.5 | 46.2 | Distance between gratings G1 and G2, cm | 185 | 190 | Horizontal beam size at grating G1, cm | 78.5 | 95 | Horizontal beam size at grating G2, cm | 121 | 138 | Input pulse energy, J | 1145 | 1669 | Output pulse energy, J | 751 | 1095 | Output pulse power (Fourier limit), PW | 40 | 58 | Output pulse power, PW | 35 | 50 |
|
Table 6. Parameters for two compressor options.
|
---|
Number of channels | Focusing | Options | Power, PW | Intensity, 1025 W/cm2 |
---|
1 | F/1 | Basic | 50 | 0.44 | | | With post-compression | 230 | 2.0 | | | With SHG | 70 | 2.5 | 12 (without post-compression and SHG) | Dipole | Without phase-locking | 600 | 9 | | | With phase-locking | 600 | 32 |
|
Table 7. XCELS laser power and intensity.