Introduction to Experimental
Techniques in Optics
Motivation: Optics is becoming increasingly important in many application areas
such as communication/computing and chemical/biological diagnostics. For most of
these applications, the basic hardware and experimental techniques are similar.
Overview: This course will provide a hands-on introduction to these techniques.
Lab skills are the main focus. Lectures will supplement.
Specific details:
• Start from scratch -- Build opto-electronic servo systems
– laser intensity stabilization
– wavelength filter -- active control
• Break complex tasks into a series of simpler ones
Sample of material covered
Experimental techniques and capabilities
• Optics & mechanics
– Optics handling
– Mount assembly
– Machining skills ?? – Cannot always buy what is needed
• Optoelectronics
– Electronics skills – soldering, prototype boards
– Circuit design – servos ?? – High sensitivity of optics often requires control
– Interfaces – detectors, transducers
• Lab proficiency demonstrations
• Lab book – important in real world
– Neatness not critical – will not count against
– Completeness important
First pieces to make
• Mirror mount post -- round
• Lens mount post =-- square
Interferometers
Mach-Zender -- Modulators for fiber communications
Mirror
Beamsplitter
Beamsplitter
Outputs
Inputs
Michaelson -- FTIR spectrometers
Input
Beamsplitter
Mirror
Mirror
Outputs
Mirror
Sanac -- Laser gyros for aircraft navigation
Input
Mirror
Mirror
Beamsplitter
Outputs
Mirror
Fabry-Perot -- Lasers and wavelength (ring version shown)
Input
Beamsplitter
Mirror
Beamsplitter
Output
Output
Mirror
Entire servo
Labels in bold are for connections or adjustments on the outside of the box
Lock/unlock
switch
Rotary switch
10 pF
100 pF
+15V
10 M
Integrator drift
compensation
100K
10 turns
50K
50K
Signal in
100K
1,000 pF
10,000 pF
Lead
100K
0.1 mF
20K
- 15V
100 W
Modulation
input
1M
50K
20K
Reference in
Diff amp
balance
> 50K
+15V
50K
DC
reference
100K
DC ref
switch
1M
Diff amp
output
Diff amp
gain
100K
150 W
100W
1M
Servo
output
Scan
input
Integrator
output
+15V
DC
input
100K
- 15V
- 15V
20K
20K
Servo box
• Put special-purpose electronics into fieldable box
• Often done in R&D environment
Lab proficiency demos
• Assemble mounts from “spare” parts
– basic machine shop skills
– optics cleaning techniques
• Basic electronics
– soldering techniques
– construct and balance differential amplifier
– construct and null integrator
• Construct interferometers
– construct 4 types of interferometers
– white light interferometer
• Construct and align opto-electronic system
– photodiodes, PZTs, HV drivers
• 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
Lab books
• Some are smart enough to make anything work on the first try
• The rest of us have to be organized
Lab book is key to organization
• Complex experiments:
– 1 day to take data
– 1 day to analyze and update lab book
What goes in a lab book -- everything you need to reproduce results
• Crude diagrams of experiment, circuit schematics, etc
• Pin-outs and data sheets for opto-electronic components
• Raw data -– ex: as read off voltmeter or scope
– copy of data traces (chart recorder trace, scope photo, computer image file)
• Processed data -- after computer fits, smoothing, etc
• Equations and relevant theory
• Narrative in your own words -- what was done, why, and what were results
Real world -- lab books can settle patent disputes, etc
Lab book sample -- Laser intensity servo
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Similar to upcoming proficiency demo
Crude circuit diagrams
Note -- Pasted in sheets okay
Optical setup
Circuit schematic
Effect of intensity servo on experiment
• Attempt to reach shot noise in atomic clock experiment
Noise measurement
Compare to shot noise theory
Lecture topics
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Basic experimental techniques including keeping a laboratory book and
handling of optical components
Optical mechanics and component mounting techniques
Passive optical components such as mirrors, lenses, and polarizers
Lasers – properties and operation
Coherence and interference effects
Basic electronics including op amps
Optical detectors and data collection
Active optical elements such as acousto-optics
Servos and transducers
Laser intensity stabilization
Lock-in amplifiers and ac servo techniques
Technical presentation skills
Possible supplemental topics
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Spectroscopy, FTIR
Liquid crystal displays, optical memories & correlators
Microscopy, confocal and fluorescence
Photon counting and correlation
Fiber optic techniques
Prerequisites & references
Prerequisites: None
• Include both beginning and advanced students
• Disadvantage – Advanced students bored?, Beginning students overwhelmed?
Solution
• Advanced students: Move at own pace -- proficiency exams
• Beginning students: Extended lecture time or special lectures – questions and
answers
References
References: Optics by Eugene Hecht, Addison Wesley Pub. Co.
• In print more than 20 years
• Reads like series of complete lectures
• Frees up more class time for lab work
Supplemental handouts/ web addresses
• Example: Manufacturer’s application notes
– http://www.newport.com/store/default.asp?lone=Optics&ltwo=Technical+
Reference&lang=1
– http://www.cvilaser.com/Catalog.asp?filename=/bil-productindex1221.asp
– http://www.mellesgriot.com/resourcelibrary/technicalnotes/default.asp
– http://www.newfocus.com/support/support_freelit.cfm
Grading
Grading will be “bottom-line” oriented – Prepare to succeed in future job
• Did you learn the material or not.
• Tests: 20%
– Written – scheduled, based on lecture material
• Final exam: 20%
– Optional – Can use test average as final exam grade
• Laboratory proficiency exams: 20%
– Demonstrations of experimental proficiency – when ready
• Laboratory notebooks: 20%
– Completeness first.
– Neatness only in summaries. Nothing deducted for messiness elsewhere.
– Will also be allowed during quizzes and proficiency demos
• Presentations: 20%
– Present after completing core proficiency demons
– Fellow students will also rate – Contributes to your grade
– Presentations can have “dry runs” – not count toward grade
Course meeting times
Lectures: MW 10:20 -- 11:10 am
Lab: F 10:20 am -- 1:10 pm, supplemental times ?
Problem: Limited space and equipment
Solution: Split into two groups
Homework: Everyone will have lab access
Lab books: Will supply