Physics and Astronomy UBC

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Physics and Astronomy _at_ UBC

• Undergraduate Programs
• Research
• Graduate Programs

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UGrad Physics and Astronomy

• Physics Major
• Program Requirements
• Suggestions for electives
• Minor in Another Subject
• Astronomy Major
• Honours Physics
• Program Requirements
• Suggestions for Electives
• Honours Biophysics
• Co-op option
• Honours Physics and Astronomy
• Other Combined Honours Programs
• Chemical Physics
• Physics and Computer Science
• Physics and Mathematics
• Physics and Oceanography

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Co-op Placements
gtJapan gtGermany gtDenmark gtAustralia
gtSweden gtGreenland gtChile gtTaiwan
gtHong Kong gtFinland gtSingapore gtU.K.
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Engineering Physics
Are you up to the challenge?
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UBC EngineeringSolar Car Project
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Research Areas

• Astrophysics
• Cosmology
• Planetary Science
• Relativity
• String Theory

• Condensed Matter
• Biophysics
• Atoms Molecules
• Lasers/optics
• Materials Science

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Waves, Quantum Mechanics and the Internet

• Some of the science and engineering behind
  optical communications

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Outline

• Communication Basics
• Modes of Implementation
• Optical-fibre Systems
• Lasers for Optical Communications
• basis of operation
• simple physics at work!
• The Future?

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Communication Basics

• Information Source
• video camera
• telephone
• computer (data)

• Coding Scheme
• analogue
• digital (various)

Transmission Channel

• Decoding Scheme
• corresponds to the Coding scheme

• Destination
• TV
• telephone
• computer (data)

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Implementation Schemes
Electrical Current

• Copper wire
• twisted pair (telephone)
• coaxial cable (cable)
• Wireless
• on the air
• Fibre optics

Microwave Power
Light Intensity
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Source End

• Channel
• Driver

• Channel

Source
Coax cable
Coding
Free space
Electrical Current
Optical fibre
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Coded Data
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Benefits of Optical Coding

• High carrier frequency means shorter length bits
• Shorter bit length means more bits per second
• More bits per second means higher data
  transmission rates (more bandwidth)

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The Faster is Better Trend
Nortel Networks
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Parallel Channels

• For a given bit rate, can double, triple,
  quadruple etc. the transmission bandwidth by
  sending multiple carrier frequencies (colors)
  down the same fibre

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The Multi-Colour Approach
Nortel Networks
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Technological Requirements

• Lasers absolutely must have
• low noise
• high linearity (fidelity)
• well-defined wavelength (color)
• Increasing, they should also
• be inexpensive
• have tunable wavelengths

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What Is a Laser?

• For our purposes it is

a device that converts electrical signals into
light that has a very well-defined color and
spatial extent
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more laser basics

• Basic constituents of a laser are
• atoms that emit light of the appropriate color
  when excited
• an optical cavity that controls the exact color
  and direction of the laser light

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Familiar Territory
ELECTRIC POWER
Florescent Bulb
OPTICAL POWER
Mirrors
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Semiconductor Lasers

• Gas lasers too bulky, inefficient, and inflexible
  (one color per type of atom)
• Just how bad are they?
• Semiconductor laser puts out 5 times more
  optical power, consumes less electrical power,

AND IT IS A MILLION TIMES SMALLER!
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More Semiconductor Lasers
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For Scale, a Segment of Hair
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If You Didnt Believe That...
Jens Hair
Laser Ridge
Ben Ruck and Jens Schmidt, UBC
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Closer LookSemiconductor Layers

• SUBSTRATE WAFER
• Indium Phosphide (InP)
• electrical conductor
• heat sink
• something big enough to manipulate!

• BOTTOM CONFINEMENT LAYER
• extremely high quality InP layer
• starts off electrically conducting
• ends up an insulator

• TOPCONFINEMENT LAYER
• extremely high quality InP layer
• starts off an insulator
• ends up a conductor

• ACTIVE LAYER
• different composition (InGaAsP)
• insulator
• light prefers being in this material

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Define Optical Cavity

• SHALLOW ETCH
• confines light laterally

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Electrical Contact (Step 1)
DEPOSIT INSULATOR
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Electrical Contact (Step 2)

• ETCH HOLES
• where electrical contact wanted

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Electrical Contact (Step 3)

Bottom
Top
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More Detail in the Active Region

Quantum Wells each 5 nm thick
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Atomic Images of Quantum Wells
Chen, Feenstra et al., Applied Physics Letters
1999
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Electron Micrograph of Grating
Schrenk et al., http//www.iaee.tuwien.ac.at/gme/j
b98/schrenk.htm
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Future Laser Array?
10 mm
Vighen Pacradouni et al., UBC
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Quantum Dots!
Pinnington et al., UBC
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Conclusions

• Optical communications hardware already employs
  some very sophisticated technology, based on
  simple wave mechanics (classical and quantum)
• You aint seen nothin yet!