1. BESTIA (Brookhaven Experimental Supra-Terawatt Infrared at ATF) Laser: A Status Report.‬

2. Outline
ATF’s Terawatt CO2 laser overview
BESTIA concept (as presented at AAC ’14)
Progress since AAC ’14
Current vision of the roadmap to 100 TW

3. ATF’s Terawatt CO2 laser: Active medium
“1 ps”
1 bar
10 bar
10 bar,
isotopes µm µm

4. ATF’s Terawatt CO2 laser: Scheme
1 µJ
10 mJ
6 J
СЩ2
CO2
CO2
“Master oscillator”
Produces a picosecond seed pulse
Regenerative amplifier
Provides most of amplification
Small active volume
Isotopic
Final amplifier
Main source of energy
Large active volume
No isotopes (yet)

5. ATF’s Terawatt CO2 laser: Specs
Two amplifiers
Single amplifier
Maximum achievable
Routine operation
Peak power
2 TW
0.5 – 1 TW
5 GW
Pulse energy
6 J
2 – 4 J
10 mJ
Pulse duration
3 ps
3.5 ps
1.7 ps
Rep. rate
0.05 Hz
3 Hz
Wavelength
10.2 µm
9.2 µm

6. 100-TW concept (as of AAC ’14)
OPA: fs seed
Stretcher + compressor = Chirped pulse amplification
High-pressure, isotopic amplifiers
Nonlinear compressor
Collection
of innovations:
Non-linear compressor
70 J
50 J
2 ps
25 TW
OPA
Ti:Al2O3
Amplifier 1
Stretcher
35 µJ
350 fs
10 µJ
100 ps
100 mJ
Amplifier 2a
Amplifier 2b
Amplifier 2c
10 J
100 fs
100 TW

7. Progress: solid-state frontend
In routine operation
0.35 ps
25 µJ
5 ps
0.1 µJ
New system: OPA
Old system: TEA CO2 laser with amplifier and multi-stage pulse slicing

8. Chirped-pulse amplification: what’s done
In routine operation
CPA in regenerative amplifier only
Str.
Amp.
Cmp.
0.35 ps → 80 ps → 50 ps → 1.7 ps
Compressor
Stretcher
YAG
Coupler
Semiconductor switch (Si)
Amplifier vessel
Pockels cell
Polarizing splitter
Photo- detector
Osc.
OPA
Ti:Al2O3
(1.6 ps)
Polyanskiy, Babzien, Pogorelsky, "Chirped-pulse amplification in a CO2 laser,"  Optica 2, , 2015

9. Chirped-pulse amplification: work in progress
75 mm
Self-focusing of a 3.5-ps pulse in NaCl window
0.5 J
0.7 J
0.9 J
1.3 J
1.7 J
2.5 J
Full-power compressor test stand
Vacuum chamber for BESTIA’s compressor: 1.5 x 2.4 m2
165x220 mm2
75 lines/mm
1 TW (3.8 J, 3.5 ps) demonstrated

10. Non-linear compressor
non-linear material
aperture (spatial filter)
Pair of small-density gratings
(linear compressor)
>1 ps
<1 ps
2.5 J
20 mm
3.5 J
Spectrum
2.5 J
OUT IN
Proof-of-principle test: simulations
Pulse
Polyanskiy, "Pulse compressor,” US Patent Application A1 (Jan. 14, 2016)
OUT
Polyanskiy, "co2amp: A software program for modeling the dynamics of ultrashort pulses in optical systems with CO2 amplifiers,"  Appl. Opt. 54, , 2015 IN

11. Optical materials considerations
F=50 cm
sample
laser
vacuum: <= 0.1 mbar
Cu mirror
100 µm
I0 = 8.0 J/cm2
“Replica” Cu grating
I0 = 3.4 J/cm2
Damage threshold (J/cm2) µm
Bare
Grating
(replica)
Grating (master) Cu 5
1.5
??? Al
0.5 Mo
2.5 -
100 µm

12. 6 m Ø1 m New final amplifier Discharge 3 × (8.5×10×100 cm3)
isotopic CO2
50% 18O
BESTIA’s design energy: 70 J before compression
Present system: demonstrated 18.5 J in chirped pulse

13. Roadmap Present system CPA
Real-life test of full-power CPA at TW
More stretching, reach 100 mJ in regen
Test master Cu grating
Non-linear compressor: proof of principle (R&D)
BESTIA
Final amplifier
Start with two amplifier sections
Start without isotopes
Demonstrate J in chirped pulse
In-vacuum compressor
Demonstrate J after compression (5 TW, µm)
Isotopes
Install and test CO2 freeze-out system for isotope recovery
Add isotopes to main amplifier
Demonstrate J after compression (10 TW, µm)
Non-linear compressor (R&D)
Achieve 25 TW
Future BESTIA
R&D towards 100 TW