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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
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
Gas Lasers Optic Cells

  • 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


Outline
Outline Optic Cells

  • 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
Optically Pumped Gas Lasers Optic Cells

  • Pump

  • Relaxation

  • Stimulated Emission of Radiation

http://www.answers.com/topic/population-inversion-3level-png-1


Detailed model
Detailed Model Optic Cells

...

J12

J11

J10

J 9

...

N3

v1+v3

+

P13

...

J12

J11

J10

J 9

N2

v4

...

J13

J12

J11

J 10

...

N1

No Vibration


Rate equations
Rate equations Optic Cells

Abs.

Abs.

Stim.

Spon.

Spon.

Abs.

Stim.

Stim.

Spon.

Spon.

Abs.

Abs.

Stim.


Gain Optic Cells

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
Acetylene Gas Optic Cells

  • Well understood

  • Quickly available

  • Frequency reference measurements

  • Possible to produce light in a region that works well with fiber optic equipment


Laser cavities
Laser Cavities Optic Cells

  • 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


Fiber optic cell
Fiber Optic Cell Optic Cells

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


Variable pressure cavity
Variable Pressure Cavity Optic Cells

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


6.75cm Optic Cells

4cm

Output Coupler Vacuum Chamber

14cm

Screw

4cm

Curved Mirror

5cm

Bellows

5cm

Screw

Vacuum

XYZ Translation


Final setup
Final Setup Optic Cells

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


Final setup1
Final Setup Optic Cells

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


What i have learned this summer
What I have learned this summer Optic Cells

  • Splicing Fibers

  • Fiber Optic Components

  • Free space optics

  • Optically pumped gas laser theory

  • Vacuum Systems


What i have done this summer
What I have done this summer Optic Cells

  • 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 Optic Cells

Buffer Gas


Summary
Summary Optic Cells

  • 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
Future Directions Optic Cells

  • 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
Acknowledgements Optic Cells

  • 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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