Transcript Wollaston and Nomarski Prisms

The evolution of electron density of laser plasmas
With the Normarski
interferometer, we
measure the plasma
density of laser
plasmas.
beam expander
imaging lens
bi-prism
imaging plane
Time integrated imaging Thomson scattering
ZTe=883eV @ x=810 m
ZTe=1078eV @ x=810 μm
ZTe=308eV@ x=810μm
E=6J, focused in front of the
target surface
E=2J, focused on the target
surface
x
E=6J, focused on the target
surface
stray light
signal from sound waves
Time-integrated Thomson scattering from
ablated solid target is performed to investigate
the temperature of laser plasmas under various
conditions.
390~409pixel
2.52e18 cm^-3
2.79e18 cm^-3
2.25e18 cm^-3
Experimental data
1.0
0.8
ne  2.52 1018 cm -3
laser beam
Z 7
Intensity
0.6
Te  39 eV
Ti  9 eV
0.4
0.2
0.0
480
500
520
540
560
580
s (nm)
signal from electron plasma waves
410~429pixel
2.34e18 cm^-3
2.61e18 cm^-3
2.07e18 cm^-3
Experimental data
1.0
0.8
ne  2.34 1018 cm -3
Z 7
emission from nitrogen ions
stray light
Intensity
0.6
Te  42 eV
Ti  9 eV
0.4
0.2
0.0
Time-integrated Thomson scattering from
heated gas target is performed to investigate
the density and temperature of laser plasmas.
480
500
520
540
s (nm)
560
580
210~229pixel
signal from sound waves
1.0
ne  2.16  1018 cm -3
Te=17eV
Te=22eV
Te=12eV
Experimental data
Z 7
0.8
Te  17 eV
Intensity
Ti  9 eV
0.6
Vi  2 105 cm/s
Ve  9 105 cm/s
0.4
0.2
0.0
531.4
531.6
531.8
532.0
532.2
532.4
532.6
s (nm)
230~249pixel
1.0
ne  2.16  1018 cm -3
0.8
Te  20 eV
Te=20eV
Te=25eV
Te=15eV
Experimental data
Z 7
Intensity
Time-integrated Thomson scattering from
gas target is performed to investigate the
density and temperature of laser plasmas.
Ti  9 eV
0.6
Vi  5 105 cm/s
Ve  4 105 cm/s
0.4
0.2
0.0
531.4
531.6
531.8
532.0
s (nm)
532.2
532.4
532.6
Wollaston and Nomarski Prisms
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Birefringent Wollaston and/or Nomarski prisms are inserted in the optical pathway with their shear
axis oriented at a 45-degree angle (northwest to southeast) to the polarizer and analyzer. The
prisms are composed of two precisely ground and polished wedge-shaped slabs produced from
high-grade optical quartz, a uniaxial birefringent crystal. Two quartz wedges having perpendicular
orientations of the optical axis must be fabricated to produce a single Wollaston (or Nomarski)
prism. The wedges are cemented together at the hypotenuse to generate an optically anisotropic
compound plate where the crystallographic optical axis of the first wedge is perpendicular to the
optical axis of the second wedge. Incident linearly-polarized wavefronts that enter a prism
(oriented with the optical axis at a 45-degree angle to the polarized light) in the condenser aperture
are divided into two separate orthogonal waves, termed the ordinary and extraordinarywave.
The mutually perpendicular extraordinary and ordinary component wavefronts are coherent, have
identical amplitudes (70.7 percent of the original polarized wave), and travel in the same direction
through the lower half of the Wollaston prism. However, the waves propagate at different velocities,
which are defined by the dielectric properties along the slow and fast axes of the lower birefringent
quartz crystalline wedge. The ordinary wave proceeds through the prism along the fast axis (having
a lower refractive index), while the extraordinary ray travels through the slower axis, which has a
higher refractive index. In quartz, the refractive index difference between the fast and slow axes is
approximately 0.6 percent, and the fast axis is oriented perpendicular to the crystallographic axis of
the wedge. Therefore, the ordinary wave traverses a quartz wedge section perpendicular to the
optical axis, while the extraordinary wave is oriented parallel to this axis.