Title: Constructing Gas Lasers Inside of Photonic Band Gap Fiber Optic Cells
1Constructing Gas Lasers Inside of Photonic Band
Gap Fiber Optic Cells
- Joshua Perkins
- Texas AM University
- Kansas State University REU
- Mentor- Dr. Kristan Corwin
R. Thapa et al, Opt. Express, 2006
2Gas Lasers
- Well understood
- Relatively cheap gain medium
- Difficult to damage the gain medium
- Large volumes of active material
- Very Efficient
- Bulky
- Complex
- Fragile
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3Outline
- 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
4Optically Pumped Gas Lasers
- Pump
- Relaxation
- Stimulated Emission of Radiation
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5Detailed Model
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P13
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No Vibration
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6Rate equations
Abs.
Abs.
Stim.
Spon.
Spon.
Abs.
Stim.
Stim.
Spon.
Spon.
Abs.
Abs.
Stim.
7Gain
Alkali-vapor lasers can have gains of 2000x CO2
is about 4 per cm and up to 200 per centimeter
for pulsed CO2
8Acetylene Gas
- Well understood
- Quickly available
- Frequency reference measurements
- Possible to produce light in a region that works
well with fiber optic equipment
9Laser 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
10Fiber Optic Cell
Cross section of the smallest human hairs
Splice
Splice
SM Fiber
SM Fiber
PBG 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
11Variable 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 dont exist for these wavelengths - More vacuums to maintain and more free space
optics to align
12Output Coupler Vacuum Chamber
14cm
Screw
4cm
5cm
Curved Mirror
Bellows
5cm
Screw
Vacuum
XYZ Translation
13Final 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
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15Final 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
16What I have learned this summer
- Splicing Fibers
- Fiber Optic Components
- Free space optics
- Optically pumped gas laser theory
- Vacuum Systems
17What 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.
18C2H2
Buffer Gas
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21Summary
- 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
22Future 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
23Acknowledgements
- K-State REU Program 2008 funded by NSF
- Dr. Kristan Corwin Mentor
- Dr. Larry Weaver
- Andrew Jones
- Kevin Knabe
- Dr. Karl Tillman
- Mike Wells