Introduction to Diode Pumped Alkali vapor Laser -DPAL

Lin Li Institute of Electronics, Chinese

Academy of Sciences Rongqing Tan

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Laser-Light Amplification by Stimulated

Emission of Radiation

Properties:

Monochromatic

Directional

Coherent

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Applications

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• Industry (cutting and welding)

• Military (marking targets , measuring range and speed )

• Research (laser cooling)

• Others (barcode scanners, holographic laser projection)

Laser Components

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Gain medium

Pump energy

Optical cavity

Type Typical Wavelength

Solid state lasers Neodymium-YAG 1.064µm

Gas lasers CO2 lasers 10.6µm

Semiconductor lasers Diode lasers 375-3500nm

Chemical lasers HF lasers 2.6-3.3nm

Types of Lasers

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New type of lasers

In recent years, with the development of diode lasers, there are many new classes of laser devices using diode lasers as pump energy, such as DPSSL (Diode Pumped Solid State Laser), DPAL (Diode Pumped Alkali Vapor Laser).

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People are always looking for lasers with high efficiency, good beam quality, duration etc.

First DPAL by Lawrence Livemore National Laboratory

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Alkali D1 line(nm) D2 line(nm) ΔE(cm-1) QE(%)

Li 670.98 670.96 0.34 99.997

Na 589.76 589.16 17.2 99.898

K 770.11 766.70 57.7 99.557

Rb 794.98 780.25 237.9 98.147

Cs 894.59 852.35 554.1 95.278

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Alkali earth metals Alkali Quantum Efficiencies

Properties of Alkali metals

Einstein was awarded the

Nobel Prize for his discovery and

interpretation of the formula -

E=mc2 - right?

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Wrong

Photoelectric effect

E=h

=h

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Light consists of photons, each with discrete quantum of energy proportional to their wavelength.

2S1/2

2P3/2

D2 line pump

D1 line laser

2P1/2

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Three energy levels of Rb

Ground state

Pump state

Lasing state

λpump=780 nm λlaser=795 nm

26.23 ns

27.70 ns population inversion

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DPAL configuration designed by IECAS

Polarization Beam Splitter

Commercial laser diode

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Single Emitter

Single Bars

Stacked Array

Experiment

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Simulation from Zemax

Beam shaping

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Output power versus incident pump power Maximum output power is 2.8 W Optical-to-optical efficiency is 21%

Light spot of Rb laser

Experiment result

Conclusion

1 DPAL is a new class of lasers with the advantage of high quantum efficiency, good beam quality and less thermal effect.

2 Using fluid medium to improve the efficiency and output laser power.

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Reference 1 Laser-Wikipedia

2 How a Laser Workshttp://muldoonshealthphysicspage.com/how_a_laser_works.htm

3 http://en.wikipedia.org/wiki/Photoelectric_effect

4 SCI FI SCIENCE

http://science.discovery.com/tv-shows/sci-fi-science/videos/sci-fi-science-using-laser-beams.htm

5 Focus: Landmarks: Laser Cooling of Atoms

6 Thesis: BROADBAND PUMPING EFFECTS ON THE DIODE PUMPED

7 Thesis: Theoretical investigation on diode pumped rubidium vapor laser

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