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Constructing Gas Lasers Inside of Photonic Band Gap Fiber Optic Cells

Constructing Gas Lasers Inside of Photonic Band Gap Fiber Optic Cells. Joshua Perkins Texas A&M University Kansas State University REU Mentor- Dr. Kristan Corwin. R. Thapa et al, Opt. Express, 2006. Gas Lasers. Well understood Relatively cheap gain medium

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Constructing Gas Lasers Inside of Photonic Band Gap Fiber Optic Cells

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  1. Constructing Gas Lasers Inside of Photonic Band Gap Fiber Optic Cells Joshua Perkins Texas A&M University Kansas State University REU Mentor- Dr. Kristan Corwin R. Thapa et al, Opt. Express, 2006

  2. Gas Lasers • Well understood • Relatively cheap gain medium • Difficult to damage the gain medium • Large volumes of active material • Very Efficient • Bulky • Complex • Fragile Diode Laser http://en.wikipedia.org/wiki/Image:Laser_diode_chip.jpg http://technology.niagarac.on.ca/lasers/Chapter6.html

  3. Outline • How molecular gas lasers work • Why we picked Acetylene gas • How laser cavities work • Our solution for better gas cells • Our laser cavity setup and estimated losses • My accomplishments this summer

  4. Optically Pumped Gas Lasers • Pump • Relaxation • Stimulated Emission of Radiation http://www.answers.com/topic/population-inversion-3level-png-1

  5. Detailed Model ... J12 J11 J10 J 9 ... N3 v1+v3 + P13 ... J12 J11 J10 J 9 N2 v4 ... J13 J12 J11 J 10 ... N1 No Vibration

  6. Rate equations Abs. Abs. Stim. Spon. Spon. Abs. Stim. Stim. Spon. Spon. Abs. Abs. Stim.

  7. Gain Alkali-vapor lasers can have gains of 2000x CO2 is about 4% per cm and up to 200% per centimeter for pulsed CO2

  8. Acetylene Gas • Well understood • Quickly available • Frequency reference measurements • Possible to produce light in a region that works well with fiber optic equipment

  9. Laser Cavities • A laser cavity is simply gain medium between mirrors with some way to get energy in and photons out. Mirror Mirror C2H2 Glass Tube • Issues: • For more gain a longer (or wider) cavity is required, but scaling is an issue • Pump Beam Size • Intensity in gain medium

  10. Fiber Optic Cell Cross section of the smallest human hairs Splice Splice SM Fiber PBG Fiber SM Fiber • Much less fragile • Flexible even during lasing • Extremely high intensities compared to normal gas cells • Input and output are fiber allowing for the use of other fiber optic devices. • Splices between SMF and PBGF are hard to make and are lossy • Loss is due to mode mismatching because PBG are multi mode and Single Mode are not. Also Refractive index Change • Delicate due to fine structure being melted to the solid face of SM fiber

  11. Variable Pressure Cavity To pump Gas Inlet Pump Mirror Hollow optical fiber OC Mirror Laser Polarizing Beam Splitter C2H2 molecules • Has worked in the past • Polarization is necessary because dichroic mirrors don’t exist for these wavelengths • More vacuums to maintain and more free space optics to align

  12. 6.75cm 4cm Output Coupler Vacuum Chamber 14cm Screw 4cm Curved Mirror 5cm Bellows 5cm Screw Vacuum XYZ Translation

  13. Final Setup 0.59 dB ~7.11 dB Round-trip Loss PBS Fiber Mirror 0.83 dB 0.32 dB R = 99% 1.87 dB f = 40 mm 2.9 dB (estimated) f = 25 mm PD PBGF

  14. Final Setup Light from Decepticon (1532 nm) Amplified by an EDFA 0.59 dB ~7.11 dB Round-trip Loss PBC Fiber Mirror 0.83 dB 0.32 dB R = 99% 1.87 dB f = 40 mm 2.9 dB (estimated) f = 25 mm PD PBGF

  15. What I have learned this summer • Splicing Fibers • Fiber Optic Components • Free space optics • Optically pumped gas laser theory • Vacuum Systems

  16. What I have done this summer • Design of optical and vacuum systems • Part ordering • Building of optical and vacuum systems • Took a project that had just cleared the proposal stage and built a functional testing apparatus.

  17. C2H2 Buffer Gas

  18. Summary • How molecular gas lasers work • How laser cavities work • Improvement of gas cells using PGB Fibers • Vacuum chamber and fiber lasing scheme setup • What I learned in the REU

  19. Future Directions • Fluorescence Testing. • Rate constant control with buffers • Working all fiber gas laser • Comparable to diode lasers for cost and size, but keeps the advantages of gas lasers

  20. Acknowledgements • K-State REU Program 2008 funded by NSF • Dr. Kristan Corwin –Mentor • Dr. Larry Weaver • Andrew Jones • Kevin Knabe • Dr. Karl Tillman • Mike Wells

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