Optics, Lasers, and Remote Sensing Department 1128 Microlasers and Nonlinear Optics R. Schmitt, D. Armstrong, A. Smith, B. Do, and Greg Hebner Sandia National Laboratories Laser, Remote Sensing, Plasma Physics and Complex Systems Department 1128 Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
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Optics, Lasers, and Remote Sensing Department 1128 Microlasers and Nonlinear Optics R. Schmitt, D. Armstrong, A. Smith, B. Do, and Greg Hebner Sandia National.
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Optics, Lasers, and Remote Sensing Department 1128
Microlasers and Nonlinear Optics
R. Schmitt, D. Armstrong, A. Smith, B. Do, and Greg Hebner
Sandia National LaboratoriesLaser, Remote Sensing, Plasma Physics and Complex Systems
Department 1128
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
Optics, Lasers, and Remote Sensing Department 1128
Emerging and enabling technologies require investment
• Long history of atomic and molecular physics– Spectroscopy, optical surface diagnostics
• Fiber lasers– Emerging compact high power sources.
• Frequency extension, nonlinear optics– Generate wavelength(s) matched to the mission
requirements.– Recent advances in nonlinear optics understanding are
enabling new system designs.
• Exploiting the THz region of the EM spectra– New source and detector technology is opening up the THz
spectral region.– High chemical specificity, unique and not widely published
spectral signatures, low probability of intercept, broad area imaging using SAR like processing.
• Compact, robust sources– Micro lasers, high power in a small size.– Solid-state and semiconductor laser systems
• UV solid state lasers are relatively well developed at 400 nm with 290 nm sources on the horizon. Wavelengths are a good fit to some remote sensing opportunities.
0.6 THz image
1.5 1 0.5 0 0.5 1 1.51.5
1
0.5
0
0.5
1
1.5
Optics, Lasers, and Remote Sensing Department 1128
Basic design for passively Q-switched microlaser
• fiber-coupled diode laser pump (electrical isolation)• passively Q-switched (electrical isolation)• Cr:Nd:GSGG active material (rad hard)• Cr4+:YAG Q-switch (rad hard)• simple cavity with mirror coatings directly on crystal faces• crystals bonded together to form rugged, monolithic laser• thermal lensing and gain guiding stabilize flat-flat cavity
Cr:Nd:GSGG Cr4+:YAG 1.06 moutput pulse
lens808-nm pump light
Fiber
Optics, Lasers, and Remote Sensing Department 1128
The Cr:Nd:GSGG microlaser produces ~1.6-ns-wide pulses
• Eout = 57 μJ / pulse
• ~1.6 ns (FWHM) pulse width
• raw beam Imean ~ 150 MW/cm2
• after-pulse is common– ~15 - 25% total energy in
second pulse typical
– affected by details of pump focus, pump beam quality
• linearly polarized (>100:1)-5 0 5 10 15 200
50
100
150
time (ns)
Inte
nsity
(M
W/c
m2 )
1.6 ns FWHM
near field beam intensity (MW/cm2)
output energy is scalable from μJ to 100’s of μJ
Optics, Lasers, and Remote Sensing Department 1128
The Cr:Nd:GSGG microlaser produces excellent beam quality
• The near-field beam diameter (1/e2) is 150 μm (h) x 144 μm (v).
• The far-field divergence (1/e2 full angle) is 10.2 mRad (h) x 10.6 mRad (v).
• M2 ≈ 1.05 (fitted second moment beam diameter to propagation equation)
Optics, Lasers, and Remote Sensing Department 1128
Near- and far-field = 803 nm signal fluence profilesNear- and far-field = 803 nm signal fluence profiles
Fresnel # D2 / L > 450 for Signal = 803 nm Fresnel # D2 / L > 450 for Signal = 803 nm
Far field: Lens with effective f/# 77Far field: Lens with effective f/# 77Near field: Image of OPO output couplerNear field: Image of OPO output coupler
SPIE 5887-3
Optics, Lasers, and Remote Sensing Department 1128
Pump depletion for seeded and unseeded oscillationPump depletion for seeded and unseeded oscillation
Self-seeded oscillation in two-crystal RISTRA~85% pump depletion
Self-seeded oscillation in two-crystal RISTRA~85% pump depletion
Free-running oscillation in two-crystal RISTRA ~37% pump depletion
Free-running oscillation in two-crystal RISTRA ~37% pump depletion
SPIE 5887-3
Optics, Lasers, and Remote Sensing Department 1128
Are flat-top beam profiles important?Are flat-top beam profiles important?