Laser Dye Performance

A. Jaqueline Mena University of Hawai’i- Hilo

W.M. Keck ObservatoryMentor: Kenny Grace

Advisor: Jason Chin

Funding provided through the Center of Adaptive Optics, a National Science Foundation Science and Technology Center (STC), AST-987683

Photo Credit: John McDonald, CFHT

Overview• Background

Information:– Laser Guide Star– Dye Laser

• Introduction:– Problem– Purpose– Goal

• Experiment– Set-up/Procedure

• Analysis– Peak-to-Valley Ratios– Spectral Slopes– Dye Concentration

Measurements

• Results and Conclusion

• Acknowledgements

Laser Guide Star (LGS)

589nm Excites sodium layer

Creates an artificial guide star

Allows image correction:

Background Photo: http://www.kaunana.com/Default.aspx?tabid=62Courtesy of W.M.Keck and UCLA

Basic Dye Laser

Layout: Keck’s Laser

DMODye Master Oscillator

6 Yag LasersYttrium Aluminum Garnet

Problem The observatory presently has no method for determining when its laser dye should be changed

to maintain the laser guide star’s performance. Old dye can cause down time on the laser for

several nights.

Old dye……new dye, see our problem?

R2 Perchlorate Dye dissolved and diluted in Ethanol

Old DMO Dye

• Output power was 9 watts

After the dye was replaced…

• Output power was 18 watts

This means…

• The laser is twice as efficient with the new dye

To find consistent characteristics in old dyes’ spectra that will help determine when the dye should

no longer be used.

Purpose

Goal

To create a specific procedure for analyzing laser dye samples, and

to identify the spectral features that change most with dye age

and overexposure .

Steve Doyle holding up a small sample of old dye

Experiment

• Four Dye Samples: New Dye, Dye with 200 hours of use, Old Amplifier (Amp) dye (unknown exposure

time), and Old Dye Master Oscillator (DMO) Dye (unknown exposure time)

• New Dye

• 200 Hr. Dye

• Old Amp Dye

• Old DMO Dye

Peak-to-Valley Subtractions

Subtracted: B-A, B-C, D-E, F-G

A B

C

D

E

FG

-2

0

2

4

6

8

10

12

14

1 2 3 4 5 6 7

DMO Amp 200 Hr New

12

34

S1

0

0.001

0.002

0.003

0.004

0.005

0.006

0.007

0.008

0.009

0.01

Slopes between 253.08-240.03nm

• New Dye• 200 Hr. Dye• Old Amp Dye• Old DMO Dye

Old DMO

Old Amp 200 Hr. New

12

34

S1

-0.001-0.0005

00.0005

0.0010.0015

0.002

0.0025

0.003

0.0035

0.004

Slopes between 284.39-269.08nm

•New Dye•200 Hr. Dye•Old Amp Dye•Old DMO Dye

11%

127%89%

Concentration Measurements

• New Dye: 0.22678

• 200 Hr. Dye: 0.226780%

• Old Amp Dye: 0.1385839%

• Old DMO Dye: 0.1488734%

•Dye should be changed when the bar graph of the peak-to-valley subtraction calculations changes in pattern compared to the new dye.

-2

0

2

4

6

8

10

12

14

1 2 3 4 5 6 7

•Dye should be changed when the slope changes by more than 30% of the original.

•Dye should be changed when the concentration drops by 30%

•Dye should be changed when the graph’s peak at 546.69nm drops by 30%

Acknowledgments Center for Adaptive Optics

Sarah Anderson

Lisa Hunter

Scott Seagroves

Hilary O’Bryan

Internship short course staff

My internship peers

Everyone at W.M. Keck Observatory

Taft Armandroff

Kenny Grace

Ron Mouser

Kathy Muller

Steve Shimko

Jason Chin

University of Hawai’i at Hilo

Institute for Astronomy

Thank YOU for your time and support!

Funding provided through the Center of Adaptive Optics, a National Science Foundation Science and Technology Center (STC), AST-987683