GAS LASERS AND ATOMIC LASER

3. TOPICS: GAS LASERS & ATOMIC LASERS
INTRODUCTION
 The first gas laser, the Helium–neon laser (HeNe), was co-invented by Iranian-
American engineer and scientist Ali Javan and American physicist William R. Bennett,
Jr., in 1960.
 It produced a coherent light beam in the infrared region of the spectrum at 1.15
micrometres.
DEFINATION
A gas laser is a laser in which an electric current is discharged through a gas to produce
coherent light. The gas laser was the first continuous-light laser and the first laser to
operate on the principle of converting electrical energy to a laser light output.

4. GAS LASERS
Most widely used lasers and most varied:
• Low power ( He-Ne) to High power (CO2 ) lasers
• Operates with rarified gases as active medium excited by electric discharge
• Carbon dioxide lasers, or CO2 lasers can emit hundreds of kilowatts at 9.6 µm
and 10.6 µm, and are often used in industry for cutting and welding. The
efficiency of a CO2 laser is over 10%.
• Carbon monoxide or "CO" lasers have the potential for very large outputs, but
the use of this type of laser is limited by the toxicity of carbon monoxide gas.
Human operators must be protected from this deadly gas.
Gas lasers using many gases have been built and used for many purposes:

5. TYPES OF GAS LASER
Chemical lasers (HF Laser) Excimer Lasers
Ion Lasers
Argon Laser
Helium-Cadmium Laser Copper-Vapour Laser

6. Schematic of Gas Lasers
• In gases, energy levels of atoms involved in lasing action are well defined and
narrow; broad pump bands do not exist.
• To excite gaseous atoms; pump sources with sharp wavelengths are required =
Optical pumping not suitable for gas lasers.
• Most common method; Passing electric discharge through the gas medium.
• Gas contained in a tube with cavity mirrors.
• A high DC voltage ionizes the gas for conduction.
• Electrons in the discharge transfer energy to atoms in the gas by collisions.

7. WORKING PRINCIPLE
• It is a four energy level laser system.
• The electrons produced from electric discharge collide with He and Ne atom and
excite them to the higher energy levels He2 and Ne4 at 20.61 eV and 20.66 eV
respectively.
• These two states are metastable so the atoms may stay there for a longer time.

8. Advantages
• High volume of active material
• Active material is relatively inexpensive
• Almost impossible to damage the active material
• Heat can be removed quickly from the cavity
Applications
• He-Ne laser is mainly used in making holograms.
• In laser printing He-Ne laser is used as a source for writing on the photosensitive
material.
• He-Ne lasers were used in reading Bar Codes, which are imprinted on products in
stores. They have been largely replaced by laser diodes.
• Nitrogen lasers and excimer laser are used in pulsed dye laser pumping.
• Ion lasers, mostly argon, are used in CW dye laser pumping.

9. ATOMIC LASERS
HISTORY
• The first pulsed atom laser was demonstrated at MIT by Professor Wolfgang Ketterle
et al. in November 1996.
• Ketterle used an isotope of sodium and used an oscillating magnetic field as their
output coupling technique, letting gravity pull off partial pieces looking much like a
dripping tap.
• From the creation of the first atom laser there has been a surge in the recreation of
atom lasers along with different techniques for output coupling and in general
research.
• The current developmental stage of the atom laser is analogous to that of the optical
laser during its discovery in the 1960s.
• To that effect the equipment and techniques are in their earliest developmental
phases and still strictly in the domain of research laboratories.
• The brightest atom laser so far has been demonstrated at IESL-FORTH,
Crete, Greece.

10. DEFINATION
An atom laser is analogous to an optical laser, but it emits matter waves instead of
electromagnetic waves. Its output is a coherent matter wave, a beam of atoms which can
be focused to a pinpoint or can be collimated to travel large distances without spreading.
• It is a source capable of producing an intense, highly directional, coherent beam in
which all the atoms have the same wavelength just like the photons in a laser beam.

11. CONTINUE…
The exotic quantum phenomenon of Bose–Einstein condensation is the key ingredient in
a new type of laser that emits atoms rather than photons, and that promises to
revolutionize atom optics.
Bose-Einstein basics
• The idea for an atom laser predates the demonstration of the exotic quantum
phenomenon of Bose-Einstein condensation in dilute atomic gases. But it was only
after the first such condensate was produced in 1995 that the pursuit to create a
laser-like source of atomic de Broglie waves became intense.
• In a Bose condensate all the atoms occupy the same quantum state and can be
described by the same wavefunction.
• In a Bose-Einstein condensate all the atoms have the same energy and hence the
same de Broglie wavelength. If this property can be maintained when the atoms are
released from the condensate, we will have a highly monochromatic source of
matter waves.

13. Applications
• Atom lasers are critical for atom holography. Similar to conventional holography,
atom holography uses the diffraction of atoms.
• As the de Broglie wavelength of the atoms is much smaller than the wavelength of
light, an atom laser could create much higher resolution holographic images. Atom
holography might be used to project complex integrated-circuit patterns, just a few
nanometres in scale, onto semiconductors.
• In fundamental research and industry where atomic beams are used, e.g., atomic
clocks, atom optics, precision measurements of fundamental constants, tests of
fundamental symmetries, atomic beam deposition for chip production (atom
lithography), and, more generally, nanotechnology.

14. THANK YOU