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 Difficult to damage the gain medium Large volumes of active material Very Efficient Bulky Complex Fragile Diode Laser Laser_diode_chip.jpg

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

Optically Pumped Gas Lasers Pump Relaxation Stimulated Emission of Radiation

P13 v 1 +v 3 v4v4 No Vibration... J12 J11 J10 J Detailed Model... J13 J12 J11 J J12 J11 J10 J 9 N2N2 N3N3 N1N1

Rate equations Abs. Stim. Spon.

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

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

Laser Cavities A laser cavity is simply gain medium between mirrors with some way to get energy in and photons out. C2H2C2H2 Mirror 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

Fiber Optic Cell SM Fiber PBG Fiber Splice 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 Cross section of the smallest human hairs

Variable Pressure Cavity Hollow optical fiber Gas Inlet To pump Laser C 2 H 2 molecules Polarizing Beam Splitter Has worked in the past Polarization is necessary because dichroic mirrors dont exist for these wavelengths More vacuums to maintain and more free space optics to align Mirror Pump OC Mirror

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

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

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

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

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.

C2H2 Buffer Gas

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

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

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