Photonic Devices - Bragg gratings

1
Photonic Devices - Bragg gratings
Peak shifts with temperature and / or strain
Reflectivity ()
Theory
Experiment
This graph shows typical experimental
theoretical Grating reflection spectra. The peak
wavelength is sensitive to changes in temperature
(0.01nm/ degree C) as well as changes in strain
(0.001 nm if the fibre stretches by 1 part in
106), making Bragg gratings useful in fibre
sensors.
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Special fibres for special applications
Current sensing on HV powerlines
Erbium-doped fibre amplifier for all-optical
repeaters in long haul communication links
Optical fibre wound around conductor can safely
sense magnetic fields
Non-zero dispersion-shifted fibre for long haul
high bit rate links
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Planar optical waveguides
Planar waveguides written into a polymer on a
silicon wafer using a focused laser
Microscope photo of a planar waveguide device
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Planar Optical Waveguides

• Planar waveguides can also be built up layer by
  layer, as has been done for silicon chips
• Sequence of processing steps
• Cladding deposition
• Core deposition
• Masking
• Etching
• Cladding deposition
• This allows quite complex waveguide structures to
  be fabricated over a large area in a short time

Microscope photo of a buried channel waveguide
showing the 6 micron core (bright) against a
darker cladding
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Microphotonics - a new frontier
Micro-electro-mechanical systems (MEMS)
In recent years, new kinds of moving objects such
as tiny motors, pumps and moving mirrors have
been fabricated on micrometer scales. This tiny
electronically tiltable mirror is a building
block in devices such as all-optical
cross-connects and new types of computer data
projectors.
MEMS array configured as an optical crossconnect