What is a chemical laser

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What is a chemical laser?

• a laser pumped by energy released from chemical
  reaction(s) or chemically produced species
  involved in laser medium
• This pumping mechanism makes possible to attain
  much higher laser efficiency than pumping by UV
  light or other energy.
• ? High-power continuous wave or repetitively
  pulsed chemical lasers radiating in near IR
  region can be developed.

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COIL mechanism

• Pumping
• Near-resonant energy transfer from chemically
  generated singlet oxygen, O2(1?), to atomic
  iodine
• O2(1?g) I(2P3/2) ? I (2P1/2) O2(3?)
• Lasing
• I (2P1/2) ? I (2P3/2) hv (1.315 ?m)

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SOG Singlet Oxygen Generator

• Key part of COIL - generation of primary energy
  for laser pumping
• Principle of O2(1?) generation
• gas-liquid surface reaction between chlorine and
  alkaline hydrogen peroxide
• Cl2(g) H2O2(l) 2KOH(l) ? O2(1?) 2KCl 2H2O
• Key parameter of SOG - O2(1?) yield, Y
• Y O2(1?)/O2total
• Ythresh 17 at 300 K, Yreal. up to 80

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Supersonic COIL operation

• Physical reasons
• Cooling a gas mixture flowing through gain region
  to 150 200 K by isentropic expansion
• Shifting the equilibrium of pumping reaction due
  to temperature dependent equilibrium constant
• is mainly advantageous for
• - more efficient utilization of O2(?) energy
  
• ? much higher laser power is extracted
• - reducing density gradients in gain region
• ? much better beam quality is attained

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Schematic diagram of main components of
supersonic COIL systems
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Potential applications of COIL Arguments for
COIL concern

• Very efficient conversion of stored chemical
  energy into laser radiation (chemical efficiency
  up to 30)
• Scalability to extremely high powers (tens
  of kilowatts)
• Short IR wavelength (1.315 ?m) advantageous for
  beam transmission through optical fibers making
  remote beam distribution possible
• Wavelength coupled well with materials for
  cutting and welding technology, good beam
  propagation through atmosphere
• Possible operation in continuous waves and
  pulsed regime
• Suitable for use from mobile platform
• Special Laser Technologies (e.g. dismantling
  decommissioning of dangerous devices)
• Airborne Defense Laser Program

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Scheme of pilot device and reactor with injectors
for atomic I generation via atomic Cl, including
I concentration and gain measurements
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Concentration and gain of atomic I generated in
small-scale pilot devices

• B. Absorption / emission (gain) curve for atomic
  iodine recorded for primary flow of either
  without O2(1?g), or with O2(1?g)
• Concentration of atomic iodine measured by Iodine
  Scan Diagnostics along gas flow (slow gas
  velocity of 40 m/s) in dependence on distance
  from HI injector (o ISD beam moved in flow
  direction, ? - moved against gas flow)

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Scheme of reactants (NO, HI) injection into
primary flow in subsonic COIL channel, and cross
section of supersonic laser cavity
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COIL operation with chemically generated atomic
iodine
A. Effect of HI flow on laser power at different
flow of ClO2 (NOClO2?2), 10 HI used B. Effect
of HI flow on laser power, 5 HI used, 1,2 T
1.0 , 3 T 1.4