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ECE 631 ( Photonics and Devices ) Gas Laser (He-Ne). Presentation: Muhsin Caner GÖKÇE Instructor: Prof. Dr. Celal Zaim ÇİL Çankaya University Graduate School of Natural and Applied Sciences Department of Electronic and Communication Engineering. Table Of Contents. Background Information

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ece 631 photonics and devices gas laser he ne

ECE 631 (Photonics and Devices) Gas Laser (He-Ne)

Presentation: Muhsin Caner GÖKÇE

Instructor: Prof. Dr. Celal Zaim ÇİL

Çankaya University Graduate School of Natural and Applied Sciences

Department of Electronic and Communication Engineering

table of contents
Table Of Contents
  • Background Information
  • How it works
  • Applications
  • Technical Properties
  • Pulse Mode (recent Improvements)
background information
Background information

Inventions:

  • 1954 Gordon, Zeiger, Townes: Maser
  • 1960 Maiman: Ruby-Laser (Al2O3, Solid)
  • 1961 Helium-Neon Laser (Gas) by Ali Javan in Bell Telephone Laboratories, USA
  • 1962 Semiconductor-Laser
  • 1985 Rontgen(X-ray)-Laser
background information1
Background information
  • It is a four level atom laser with a mixture of helium and neon(helium to neon (typically around 7:1 to 10:1) at a pressure of between 2 and 5 Torr (atmospheric pressure is about 760 Torr)).
  • It operates in Continuous Working (CW) mode(the Helium-Neon laser was the first continuous laser).
  • Superior beam quality(Gaussian irradiance profile, long coherence length, low divergence angle).
how it works1
 How It Works

Excited levels of Helium at 20.61 eV is very close to a level in Neon at 20.66 eV

Collision of a helium with neon atom, the energy can betransferred from the Helium to the Neon atom.

how it works2
 How It Works

Neon is the lasing gas

Visible light and IR

Fast radiative transition (spontaneous)

The lifetime of s-states is order longer than p states

Relevant energy levels of the He-Ne laser.

(Ref: Principles of Lasers Orazio Svelto 5. edition)

applications
 Applications

Red (6328 Å) (Most Common)

Yellow (594 nm) (Not efficient)

Orange (604.6 and 611.9 nm) (Not Efficient)

Green (543.5 nm) (Not efficient)

Infrared (1,523.1 nm) (Fiber optic testing)

Types of wavelengths

applications1
 Applications

Some of the important applications of He-Ne lasers:

  • Free-space optical communications
  • Bar-code scanners
  • Hologram generation
  • Fiber Optic Experimentation
  • Construction of laser light show
  • Surveillance (ie. audio surveillence)
  • Tachometer (measuring the rotation speed of a shaft or disk)
  • Burglar alarm
  • Gyroscope
  • Alignment
  • Interferometry (extracting information about the waves)
  • Laser printers
technical properties
 Technical Properties

Totally reflective mirror

Cavity Length (L)

2-5 Torr

Rb =75 kΩ

Partially reflective mirror

1.2 to3 kV DC

Since the discharge has a negative resistance, a ballast resistance is to be used in series with the laser to make the overall impedance positive

technical properties1
 Technical Properties

FWHM:Gain is at least half of the peak value

cvi melles griot company tem00
CVI Melles Griot Company TEM00

 Technical Properties

Maximum output is 100mw

Long Life (More than 10,000hours)

Low divergence angle

Rugged, compact and less expensive

cvi melles griot company tem001
CVI Melles Griot Company(TEM00)

 Technical Properties

cvi melles griot company tem002
CVI Melles Griot Company TEM00

 Technical Properties

technical properties2
 Technical Properties

CVI Melles Griot Company TEM00

pulse modes
Pulse Modes

Mode Locking:

is a technique which converts CW beam to a

periodic series of very short pulsesfrom

picoseconds to a nanosecond. 

Advantages:

  • High power pulse
  • All the cavity modes are forced to be in phase

Disadvantages:

Implementation is diffucult

pulse modes recent improvements
Pulse Modes (Recent Improvements)

Applications:

  • Photon excitation microscopy
  • Nuclear fusion
  • 3D optical data storage
  • Metal Forming Nano structure
references
References
  • (Ref: Principles of Lasers 2010, Orazio Svelto 5. edition page: 444-460)
  • http://www.cvimellesgriot.com/
  • http://www.repairfaq.org/sam/laserhen.htm#henhlc0
  • http://www.worldoflasers.com/lasertypes2.htm
  • ECE 631 lecture notes: http://ece631.cankaya.edu.tr
  • http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lasgas.html#c1
  • http://www.fou.uib.no/fd/1996/h/404001/kap04.htm