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Neodymium:YAG Laser

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Optically pumped with flashlamp or another laser. Dye Lasers Demtr der, W. Laser Spectroscopy, Springer, Berlin: 1996. CW Dye Laser with Second Harmonic Generation ... – PowerPoint PPT presentation

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Title: Neodymium:YAG Laser


1
NeodymiumYAG Laser
  • Nd3 in yttrium-aluminum-garnet (Y3Al5O12)
  • Four level laser
  • Powerful line _at_ 1064 nm often doubled or
    tripled
  • Pump Kr/Ar arc lamp or flash lamp
  • CW or pulsed operation

Ingle and Crouch, Spectrochemical Analysis
2
Diode LASERs
  • Conversion of electrical to optical power up to
    30.
  • Polished faces of semiconductor act as mirrors
    and reflect 95 of photons from leaving
    resonance cavity.

McCreery, R. L., Raman Spectroscopy for Chemical
Analysis, 3rd ed., Wiley, New York 2000
3
Stimulated Emission
Agrawal, G.P. Dutta, N.K. Semiconductor Lasers,
Van Nostrand Reinhold, New York 1993.
4
Semiconductor (Diode) Laser
Used in telecommunications, CD players, laser
pointers etc.
Blue and UV (375 400 nm) diode lasers have
recently been developed.
Eli Kapon, Semiconductor Lasers I, Academic
Press, San Diego, 1999.
5
Semiconductor (Diode) Laser
Eugene Hecht, Optics, Addison-Wesley, Reading,
MA, 1998.
6
Diode LASER Output
McCreery, R. L., Raman Spectroscopy for Chemical
Analysis, 3rd ed., Wiley, New York 2000
7
He Cd Laser
For lasing to occur, cadmium must be heated
sufficiently to obtain and maintain the proper
partial pressure of cadmium vapor in the
discharge tube. The vapor is propagated through
the system by cataphoresis (cadmium cations are
transported by discharge through the laser bore
towards the cathode). Once the cadmium vapor
leaves the bore region, it coalesces on any cool
surface.
www.mellesgriot.com
8
Ion Lasers (Ar and Kr)
CW pumped using an electrical discharge. Very
reliable. Inefficient because energy is required
to ionize gas. Power up to 40 W (distributed
over many lines). Argon ion is most common.
488 nm and 514 nm are most powerful lines.
Cluster of 10 lines in 454 529 nm. UV
334, 352, 364 nm (need several W in visible to
get 50 mW in UV) Deep UV 275 nm (need 20-30
W in visible to get 10mW _at_ 275 nm)
9
Excimer Lasers
Excimer is a dimer that is only stable in the
excited state. e.g. ArF, KrF, XeF Pass
current through noble gas / F2 mix. Lasing occurs
as excimer returns to the ground state.
Ingle and Crouch, Spectrochemical Analysis
10
Dye Lasers
Molecular transitions in the solution
phase. Active species is an organic dye (e.g.
rhodamines, coumarins, fluoresceins). To prevent
overheating, a jet of the dye solution is pumped
through focal point of optical system. Broad
transitions. Can be tuned over 50 nm. Lases in
UV-Vis-IR Difficult and expensive to
operate. Optically pumped with flashlamp or
another laser.
Ingle and Crouch, Spectrochemical Analysis
11
Dye Lasers
Demtröder, W. Laser Spectroscopy, Springer,
Berlin 1996.
12
CW Dye Laser with Second Harmonic Generation (SHG)
  • Ring laser with two focal points.
  • Ar ion laser (515 nm) for pumping.
  • Dyes with absorption maxima at 595 to 700 nm.
  • Dye jet is positioned at one focus and the
    second harmonic generating
    crystal (LiIO3) resides at the other.
  • Output at about 300 nm.
  • Cavity expansion plates allow tuning.

Myers, A.B. Rizzo, T.R. Laser Techniques in
Chemistry, Wiley, New York 1995.
13
Dye Lasers
Molecular transitions in the solution
phase. Active species is an organic dye (e.g.
rhodamines, coumarins, fluoresceins). To prevent
overheating, a jet of the dye solution is pumped
through focal point of optical system. Broad
transitions. Can be tuned over 50 nm. Lases in
UV-Vis-IR Difficult and expensive to
operate. Optically pumped with flashlamp or
another laser.
Ingle and Crouch, Spectrochemical Analysis
14
Tunable Lasers
E.g. Emerald laser Be3Al2Si6O18Cr3 (720 to 842
nm) E.g. Titanium sapphire laser (650 to 1000
nm) E.g. Dye lasers E.g. Solid-state
semiconductor lasers E.g. Ar/Kr ion laser Nine
selectable wavelengths (476 to 676 nm). To select
a wavelength, the operator turns a calibrated
micrometer on the back panel of the laser head,
rotating a prism assembly around the optical axis
of the laser.
www.mellesgriot.com
15
External Cavity Diode LASER
  • Diffraction grating selects and stabilizes
    output wavelength.
  • Diffraction grating permits tunability over 10
    nm range.
  • Isolator reflects 95 of photons from diode and
    prevents stray light from entering resonance
    cavity.

McCreery, R. L., Raman Spectroscopy for Chemical
Analysis, 3rd ed., Wiley, New York 2000
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