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

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

ECE 631 (Photonics and Devices) Gas Laser (He-Ne) Presentation: Muhsin Caner GKE Instructor: Prof. Dr. Celal Zaim L ankaya 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 (Al2O3, 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

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 be transferred from the Helium to the Neon atom. How It Works Neon is the lasing gas

Visible light and IR Fast radiative transition (spontaneous) Relevant energy levels of the He-Ne laser. (Ref: Principles of Lasers Orazio Svelto 5. edition) The lifetime of s-states

is order longer than p states Applications Red (6328 ) (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 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 Cavity Length (L) 2-5 Torr Totally reflective mirror Rb =75 k

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 Properties FWHM: Gain is at least half of the peak value

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

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: 444-460) http://www.cvimellesgriot.com/

http://www.repairfaq.org/sam/laserhen.htm#henhl c0 http://www.worldoflasers.com/lasertypes2.htm ECE 631 lecture notes: http://ece631.cankaya.edu.tr http://hyperphysics.phy-astr.gsu.edu/hbase/optmo d/lasgas.html#c1 http://www.fou.uib.no/fd/1996/h/404001/kap04.ht m

Thanks for Your Attention

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