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 How it works Applications Technical Properties Pulse Mode (recent Improvements)
Background information Inventions: 1954 Gordon, Zeiger, Townes: Maser 1960 Maiman: Ruby-Laser (Al 2 O 3, Solid) 1961 Helium-Neon Laser (Gas) by Ali Javan in Bell Telephone Laboratories, USA 1962 Semiconductor-Laser 1985 Rontgen(X-ray)-Laser
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 Works
Excited levels of Helium at eV is very close to a level in Neon at eV Collision of a helium with neon atom, the energy can be transferred from the Helium to the Neon atom.
How It Works Relevant energy levels of the He-Ne laser. (Ref: Principles of Lasers Orazio Svelto 5. edition) Neon is the lasing gas Visible light and IR Fast radiative transition (spontaneous) The lifetime of s-states is order longer than p states
Applications Red (6328 Å) (Most Common) Yellow (594 nm) (Not efficient) Orange (604.6 and nm) (Not Efficient) Green (543.5 nm) (Not efficient) Infrared (1,523.1 nm) (Fiber optic testing) Types of wavelengths
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 1.2 to3 kV DC R b =75 kΩ 2-5 Torr Partially reflective mirror Totally reflective mirror 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 Cavity Length (L)
Technical Properties FWHM: Gain is at least half of the peak value
CVI Melles Griot Company TEM00 Technical Properties Maximum output is 100mw Low divergence angle Long Life (More than 10,000 hours) Rugged, compact and less expensive
CVI Melles Griot Company(TEM00) Technical Properties
CVI Melles Griot Company TEM00 Technical Properties
CVI Melles Griot Company TEM00
Pulse Modes Mode Locking: is a technique which converts CW beam to a periodic series of very short pulses from 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) Applications: Photon excitation microscopy Nuclear fusion 3D optical data storage Metal Forming Nano structure
References (Ref: Principles of Lasers 2010, Orazio Svelto 5. edition page: ) ECE 631 lecture notes: astr.gsu.edu/hbase/optmod/lasgas.html#c1 astr.gsu.edu/hbase/optmod/lasgas.html#c1
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