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wave propagation via laser ultrasound. Laser line source. IR laser focused on 19 mm line. Transmitted EM phase image of granite at 150 GHz. JS, M. Batzle, M. Prasad, N. Greeney & A. Yuffa Colorado School of Mines.

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wave propagation via laser ultrasound
wave propagation via laser ultrasound

Laser line source

IR laser focused on 19 mm line

js m batzle m prasad n greeney a yuffa colorado school of mines
JS, M. Batzle, M. Prasad,

N. Greeney & A. Yuffa

Colorado School of Mines

Measuring electrical and mechanical properties of rocks on the submillimeter scale

Collaboration between Physics, Geophsysics and Petroleum Engineering

all data and software will be available
All data and software will be available
  • http://mesoscopic.mines.edu
  • http://physics.mines.edu/~jscales
  • Common Ground free database of rock properties
high spatial resolution techniques now available
High spatial resolution techniques now available
  • Laser ultrasound
  • millimeter/submillimeter wave EM
  • Strain microscopy
  • Acoustic microscopy (Prasad)
  • Micro-CT scan (Batzle)
motivation
Motivation
  • Complimentary measurements
  • Submillimeter waves sample on same length scale as ultrasound.
  • measurements fully noncontacting and can be done on same samples without other preparation.
laser spot size measured in microns
Laser spot size measured in microns

'high' frequency normal mode

electrical properties at sub mm resolution
Electrical properties at sub-mm resolution
  • CSM submillimeter system covers from microwaves (8-10 GHz) to 1 THz (1000 GHz)
  • Allows us to do bulk dielectric spectroscopy
  • And now, near-field scanning
abmillimetre submm vna
ABMillimetre submm VNA

Funded by NSF MRI

unique instrument
Unique instrument
  • measure amplitude and phase of the electric field over broad range of millimeter to submillimeter wave frequencies
  • In free-space or in waveguide
  • Produces linearly polarized Gaussian beams of high optical quality: quasi-optics
  • Allows 'easy optics'
dielectric spectroscopy
Dielectric spectroscopy

Fit E field with 1D Fabry-Perot

model to get complex permittivity

mmw rock physics applications scales and batzle apl papers
MMW rock physics applicationsScales and Batzle APL papers
  • Measure organic content in rocks and oil/water emulsions
  • Resolve sedimentation at the 100 micron level (implications for climate models)
  • Check mixing models (such as Maxwell-Garnett)
recent cavity perturbation
Recent: cavity perturbation
  • Have recently built ultra-high-Q millimeter wave cavity for measuring (e.g.,) conductivity of thin films.
  • Use ultrasonic cavity perturbation to measure minute changes in samples
first work at 150 ghz
First work at 150 GHz
  • Greeney & JS, Appl. Phys. Letts.
  • Bare teflon probes
  • Later, went to higher frequency, 260 GHz
  • Clad teflon in aluminum
  • Small hole at tip to prevent leakage
  • Weiss et al, J. Appl. Phys.
  • Finite element modeling of tip surface coupling
true near field scanning
True near-field scanning

Tip-sample distance .2mm

Wavelength about 1 mm

circular drum modes
Circular drum modes

Tip-sample distance .6mm

small scale effects of pyrolisis
small scale effects of Pyrolisis

McEvoy et al, 2009 oil shale conf.

pulsed laser sources
Pulsed laser sources
  • Pulses from 10 ns to 100 fs
  • Looking at first arriving energy as we scan across the sample.
  • Scanning resolution measured in nm
measuring spatial strain in real time at video frame rates
Measuring spatial strain in real time at video frame rates

Electronic Speckle Pattern Interferometry

  • Illuminate a surface with laser speckle
  • Take a picture of the speckle
  • Apply a strain
  • Take another picture
  • Subtract the two
  • The result is an interferogram
conclusion
conclusion
  • Are acquiring independent high-spatial resolution data sets for relevant rocks
  • Expect to have high-res mechanical properties soon.
  • Batzle now has micro-CT scanner. Again, no rock prep required.
  • Have a high-speed video camera for the ESPI