Modeling efforts on the Mercury Laser system

1
Modeling efforts on the Mercury Laser system

• Andy Bayramian, Camille Bibeau, Ray Beach
• Prop 92 work Ron White
• French Collaboration with MIROOlivier Morice,
  Bruno Legarrac, Marc Nicolaizeau, Xavier Ribeyre

2
Comparison of important spectroscopic and thermal
properties between pertinent laser host / dopants
     
YbS-FAP has the unique property of high cross
sections and long lifetime allowing efficient
pumping and extraction with a minimum number of
diodes
The low saturation fluence in S-FAP allows
efficient extraction below typical material
damage thresholds
     
3
Calculation of gain
Pump Equations
Gain/Extraction Equations (Franz-Nodvik)

• Feathered doping to equilibrate the gain through
  the amplifier head
• Symmetric pumping from left and right sides make
  gain profiles symmetric about center slab
• 77 of the diode pump light is transferred from
  the diode backplanes to the extractable area of
  the amplifier
• 13 of the diode pump light is transmitted
  through the amplifier due to pump saturation

4
Transfer efficiency of the pump delivery system
output matches optical modeling data
He gas in
Hollow pump light homogenizer
Diode Array
Laser beam
Gas - cooled slabs
Diode Array
Hollow pump light concentrator
5
The Mercury laser system minimizes damage by
arranging the lenses, amplifiers, Pockels cell,
and mirrors near relay planes
Pockels Cell
Reverser
Front End
Amplifier 1
Relay plane
1.5 x output telescope lens
3.5 meters
Relay plane
Relay plane
Relay plane
Relay plane
Deformable Mirror
Amplifier 2
6
Advanced beam propagation modeling using MIRO a
diffraction code developed by the French

• The MIRO code uses the paraxial wave equation
  with full diffraction and an adaptive mesh,
  which allows accurate modelling of a beam through
  an image relayed system

• MIRO results include
• F(x,y,z,t)
• I(x,y,z,t)
• Pulse shaping
• B-integral

7
Current Mercury models show promising results

• Ein 20 mJ, Eout 83 J
• Energy through
• a 5X DL spot 96.0
• a 1X DL spot 81.2
• B-integral (5 ns) 0.7 radians
• Using Dn 300 GHz bandwidth requires increase
  injection
• Ein 165 mJ, Eout 85.0 J

• Caveats to current modeling results
• Amplifier phase files are simulations
• Low frequency information lost due to small files
• Arbitrarily randomized to simulate multiple slabs
• Phase distortions on amplifiers only
• Thermal distortions not included yet
• Benchmarking in progress against Prop 92 and
  experiments

8
B-Integral causes beam breakup as the pulswidth
decreases below 1 ns
5 ns
1 ns
0.5 ns
9

• OPTICAD
• architecture
• delivery efficiency
• multiplexing angle

• VB 1D Pump
• 1-way 1D abs/slab
• 1-way 1D gain/slab

• VB 1D Extract
• 2-way 1D gain/slab
• E, B-integral, t, h
• ASE, power density

• FIDAP
• Diffuser design

OPTICAD 1-way 2D pump light deposition/slab

• TEXTAN
• Heat xfer coef.

• Fritz VB process
• 2-way 2D gain/slab
• 2D norm. source desc.

• TOPAZ
• 2D temp. distribution

• NIKE
• 2D map of stress
• and displacement

• ZEEMAX/CODE V
• Lense shape
• AAA drawings
• Expected wf error
• ghost analysis

• OPL
• 2D thermal OPL map

• ASAP
• Pinhole sizes
• Pencil beam analysis

• OPL PLOT
• 2D thermal phase map

• ASE
• Slab aperture limitations
• and geometry
• Edge cladding

Experimental Wavefront, input, and
loss measurements
code flow chart.ppt
10
Prop 92 benchmarking of the MIRO code
Front end for first 4 propagations Energy 0.1
J Wavelength 1047 nm Temporal FWHM 5 ns Time
exponent 50 Height FWHM 2.8 cm Width FWHM
4.8 cm Spatial exponent in X Y 20

• Currently benchmarking simple propagation such
  that Energy, intensity, phase, and B-integral
  match
• Phase and gain files then added and re-verified
• Optional The full mercury system modeled

11
Trivalent ytterbium shows high cross sections and
long lifetime in the Sr5(PO4)3F (S-FAP) host
sem 6 x 10-20 cm2 sabs 9 x 10-20 cm2 tem
1.14 ms
Absorption
Emission