All-solid-state Q-switched laser and Random laser

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All-solid-state Q-switched laser and Random laser
A LD-single-end-pumped all-solid-state AO
Q-switched NdYVO4 laser B LD-side-pumped
NdYAG all-solid-state EO Q-switched laser C
Random laser
Prof. Sun XiaoHong Henan Key Laboratory of Laser
and Opto-Electric Information Technology,
Zhengzhou University, Henan, China
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• Laser-diode (LD) pumped solid-state laser
  is a new laser device with advantages of
  compactness, good stabilization, high efficiency
  and long lifetime. It is widely used in the
  fields of laser radar, material processing, fiber
  communication and medical health. It has become
  one of the international key development
  direction.

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A LD-single-end-pumped all-solid-state AO
(Acousto-Optic) Q-switched NdYVO4 laser
Fig. 1 The Z-shape cavity A-Q switched system
The advantages of Z-shape cavity are separation
of the laser crystal and Q-switched crystal,
flexible adjustment of model parameters and
decrease of the laser size.
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Fig. 2 the shape of the optical pulse when the
repeated frequency is 5KHz
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• Experimental results
• When the pump power is 23W and the repeated
  frequency is 5KHz
• The max single puls energy output at 1064nm is
  0.74mJ
• The max peak power at 1064nm is 16.44kW
• The min pulse width is 35ns

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Fig.3 the experimental setup of the
LD-end-pumped CW NdYVO4   all-solid-state
inner-cavity frequency-doubled laser
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Parameters
The KTP cutting angle
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(a)
Fig. 4 the relationship of the output power at
532nm and the input power at 1064nm, the max
output is 4.44W and the light-light transfer
efficiency is 19.06
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B LD-side-pumped NdYAG all-solid-state EO
(Electro-Optic) Q-switched laser
Fig. 5 the experimental setup of the
LD-side-pumped NdYAG all-solid-state EO
Q-switched laser
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Single pulse energy 9.37mJ Pulse width
14.39ns Peak power 651.51kW
Fig.6 the shape of the optical pulse when the
repeated frequency is 200Hz
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Fig. 7 the experimental setup of the
LD-side-pumped NdYAG   all-solid-state
extra-cavity frequency-doubled laser
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Single pulse energy 0.82mJ Pulse width
8ns Peak power 90kW the light-light transfer
efficiency is 17.98
Fig. 8 the shape of the frequency-doubling
optical pulse
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C. Random laser in laser dye-doped
nano-composite PMMA film

• 1. Introduction
• 2. Characteristics and Recent Development
• 3. Our Experimental Results

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Introduction
Lasers are now commonplace. They can be used
in different fields, for example, laser weapons
in the military fields, laser diagnosis and
treatment in hospitals, bar-code scanners,
compact-disc players and display in daily life,
especially high power laser. Random laser is a
kind of thresholdless laser without an external
cavity. According to the material composition,
random laser can be classified to three types.
One is polymer based laser including dye-doped
PMMA nano-composites and conducting polymer. The
second is laser based on laser crystal powders
and semiconductor powders. The third is
temperature-tunable laser composite of laser
dyes, liquid crystal and glass powder. According
to the difference of pumping source, they include
photoluminescence and electroluminescence.
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Characteristics of random laser
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Spatial profiles of random laser emission
intensity. With the increase of pumping power,
the light spot is decreased. The light emission
transfers from incoherent Amplified Spontaneous
Emission (ASE) to coherent laser.
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Recent development
They filled a porous glass structure with laser
dye dissolved in a liquid crystal. Liquid
crystals are chain-like molecules that align to a
different degree depending on their temperature.
As the degree of alignment changes, so does the
diffusion coefficient of the overall structure.
Light emission A temperature-tunable random
laser, D Wiersma and S Cavalieri 2001 Nature 414
708.
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Action of a temperature-tunable random laser The
phenomenon is caused by the change of liquid
crystal phase with temperature.
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Random laser used in disease diagnosis
Random lasing in human tissues, Randal C. Polson
and Z. Valy Vardenya, APPLIED PHYSICS LETTERS
VOLUME 85, NUMBER 7 16 AUGUST 2004
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FIG. 1. (Color) Random laser emission spectra of
human colon tissues infiltrated with a
concentrated laser dye, namely R6G. (a) Two
typical random laser emission spectra from a
healthy, grossly uninvolved tissue (blue), of
which microscopic image is shown in (b). The
narrow spectral lines are in fact coherent laser
emission modes (Refs. 10 and 11. The inset shows
schematically closed random laser resonators
formed due to scatters in the gain medium. (c)
and (d), same as in (a) and (b), respectively,
but for a malignant colon tissue. There are more
lines in the laser emission spectra in (c) (red)
that are due to more resonators in the tumor
these are caused by the excess disorder that is
apparent in (d).
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Experimental results
Yellow emission in PMMA films
Material composition Rhodamine 590 PMMA TiO2
nanoparticles
Pump Source The film was pumped at 532nm by the
second harmonic of NdYAG laser at a 450 angle
with respect to the normal direction of the film
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Material preparation Rhodamine 590 (Rhodamine
610) and TiO2 nano-particles were mixed in 2ml of
dichloromethane until the dye was dissolved
completely. Then 2ml 13wt PMMA dichloromethane
solution was added to the above mixture. The
mixture was sonificated until a homogeneous
solution was formed. A PMMA film containing
Rhodamine 590 (Rhodamine 610) and TiO2 particles
was formed by cell-casting of 1ml of the
solution.
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SEM and SPM micrograph of PMMA nano-composite
film Particles and clusters are existed in film
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Experimental Results
Emission spectra of PMMA film doped with Rh590
and TiO2 particles with a pumping energy density
(a) 1.9mJ/cm2, (b) 95mJ/cm2. a is scaled up by a
factor of 10.
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(a)
(b)
Figure 2 Peak emission intensity (a) and
line-width (b) of PMMA film containing Rhodamine
590 and TiO2 particles plotted against pump
energy density. The inset of (a) is its log-log
curve. The laser threshold is 5mJ/cm2.
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Red Emission in PMMA films
Material composition Rhodamine 610 PMMA TiO2
nanoparticles
Pump Source The pump condition is the same as
yellow film.
Material preparation The film preparation is
almost the same as the yellow film except for
substituting Rhodamine 590 with Rhdamine 610.
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Figure 4 (left) The emission spectra of PMMA film
doped with Rh610 and TiO2 particles pumped at (a)
0.6mJ/cm2 (b) 52.8mJ/cm2 The amplitude of the
spectrum in a has been scaled up by a factor of
10 (right) The line-width Vs. pump energy
density. The laser threshold and line-width are
2mJ/cm2 and 4nm, respectively.
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Optical fiber fabricated by the above
nanocomposites. They can be used in Random fiber
laser with low threshold or without threshold.
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Thanks!