Course status
Course materials
• Lab access
• Everyone should have
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lab book
proto board
voltmeter
jumper wires
resistor card
• Write name on yours
– maintain -- example battery in voltmeter
Electronics maintenance tips
• Voltmeter has battery
– turn off when not in use
• Soldering iron corrodes if left on all night
Course status - basics
• Enough to get started in lab
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Machine safety
Mount assembly
Optics cleaning
Mach Zender alignment
Basic electronics -- diff amp, integrator
Soldering
• Lab book writeups of above skills
Next step
• Proficiency demonstrations
– like test questions
– if done correctly -- full credit
– otherwise -- partial credit
• compare to others to be sure same performance gets
same grade
• Written tests
– first test is sample -- next class period
Lab proficiency demos
• Second optical mount assembly
• Construct and align interferometers
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Michaelson
Sanac
etalon
white light interferometer
• Iris alignment
• Others ?
– Spatial filter
– Confocal etalon
• Acousto optics setup
• Fabry-Perot filter setup
• Stabilize laser intensity using simple servo
– acousto-optic shifters, VCOs
• Lock optical spectrum analyzer (Fabry-Perot) to laser
– lock-in amplifiers and ac servos, etc.
• Construct servo box
– design and packaging of special-purpose electronics
• Optimize both servos and Bode plots
Soldering
• Steps to get good joint
– Melt drop of solder on iron
– Contact work
– Flow solder directly on both work pieces
• can “tin” in advance
– Last action
• contact with fresh flux
• can be in fresh solder
• Too much solder ?
– remove with pump or wick
• Learn to be fast -- heat damage can result
Op amp debugging tips
• Check dc voltage at key pins of op amp chip
– Pin 4 = -15 V, Pin 7 = +15 V
• if not, check power supply, grounding
– Pin 6 (output)
• if greater than +/- 10 V -- saturated ? -- check inputs
– Pin 2 (+ input) = ground (or reference voltage)
• if not, connect
– Pin 3 (- input) = pin 2
• if not -- saturated, output load impedance, bad op amp
• Saturated ?
– Check voltage at each resistor connected to summing junction
• set to zero ?
• Feedback path closed ? -- short integrator
• Check ac voltage at pin 6
– MHz oscillation ? -- add capacitors on power leads
– above 1 micro Farad -- electrolytic -- observe polarity
More machining
• Second set of mounts
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learn tool change
tool sharpen (lathe)
machine setup an tear down
cleanup
• Testing of mounts
– stability -- nothing loose or vibrating
– operation -- knobs and levers work
– far field test (mirrors)
Far field test -- mirrors
• Deflect laser beam with mirror
– send long distance
– shine on card and mark position
– test alignment and stability
mirror
Long distance
screen
screen
Laser
beam
marks
Iris alignment
• Align optical sub-assembly
– interferometer ?
• Place irises in position
– one close to second mirror
– the other far from second mirror
• Disturb input laser beam alignment
• Reset alignment using only input mirrors and irises
– first center on close iris (1) using mirror 1
– then center on far iris (2) using mirror 2
– iterate
Iris 1
Iris 2
Optical
sub-assembly
Mirror 2
Mirror 1
Input