Development of a compact angleresolved optical spectrum analyzer

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Development of a compact angle-resolved optical
spectrum analyzer

• J N Philippson, M Ugray, T J Toai and R C Shiell

Trent University 1600 West Bank Drive,
Peterborough, ON, K9J 7B8 Canada
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The challenge
We wish to provide a dedicated optical spectrum
analyzer for each laser system in use
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Obtaining laser mode structure information
Fixed etalon constructive interference occurs
at a set of angles depending on the wavelength
Multimode laser radiation produces a discrete
set of rings for each mode
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Detecting an interference pattern
Singlemode beam
Dualmode beam
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The complete system
Programmable microcontrollers allow flexible
control and data transfer.
Etalon has a free spectral range at least double
the modespacing of the laser.
To your experiment
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Programmable microcontrollers
What do we use ? Programmable microcontrollers
from the PICMicro family

• Flexible clock speed
• Flexible operating voltage
• Many to choose from (gt120 chips from Digikey)
• Inexpensive between 5 - 20
• Easily programmed with free software MPLAB IDE
  and MicroPro
• Comprehensive datasheets for each chip from
  www.microchip.com
• Programmable in BASIC, C or Assembly and compile
  into hex.
• Assembly has advantage that commands take a
  known, calculable amount of time to execute

Previously used in the construction of a
wavemeter based on a travelling Michelson
interferometer
M. Ugray, J. E. Atfield, T. G. McCarthy and R. C
Shiell, Rev. Sci. Instrum. 77, 113109 (2006).
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Implementation (program)
Configure sensor
Microcontroller programs implemented in assembly,
allowing precise temporal control
Read from sensor
Send to DisplayPIC
Receive from SensorPIC
Plot curve on LCD
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System performance
Finesse 23(3) Free spectral
range 214 GHz Minimum power 3.3 mW,
decreased to 0.75 mW
At 0.75 mW incident power, SNR 14
Linearity and sensitivity
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Further details
J. Opt. A Pure Appl. Opt. 9 (2007) 10241029 J
Philippson, M Ugray, T J Toai and R C Shiell
Jeffrey Philippson MSc Thesis, chapter 4.
Available through QSpace at Queens
University http//qspace.library.queensu.ca/ Sear
ch Philippson