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 coveredExperimental 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

Beamsplitter Beamsplitter Mirror

Mirror

Inputs Outputs

Beamsplitter Mirror

Mirror

Input

Outputs

Mirror

Beamsplitter

Mirror Input Mirror

Outputs

Sanac -- Laser gyros for aircraft navigation

Michaelson -- FTIR spectrometers

Mach-Zender -- Modulators for fiber communications

Beamsplitter Mirror

Mirror

Input

Output

Output

Beamsplitter

Fabry-Perot -- Lasers and wavelength (ring version shown)

Entire servoLabels in bold are for connections or adjustments on the outside of the box

50K

50K

50K

Diff ampbalance> 50K

50KDC

reference100K

+15V

- 15V

Signal in

Reference in

100K

Diff ampgain100K

Diff ampoutput

DC refswitch

1 M

100

Lead100K

10 MIntegrator drift compensation

100K10 turns

+15V

- 15V

Integratoroutput

100

Lock/unlock switch

Rotary switch

0.1 F

10,000 pF

1,000 pF

100 pF

10 pF

20K

20K

20KDCinput100K

+15V

- 15V

Servooutput

20K

Modulationinput

1 M

Scan input

1 M

150

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• Similar to upcoming proficiency demo• Crude circuit diagrams• Note -- Pasted in sheets okay

Optical setupCircuit 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

• 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

• Spectroscopy, FTIR

• Liquid crystal displays, optical memories & correlators

• Microscopy, confocal and fluorescence

• Photon counting and correlation

• Fiber optic techniques

Prerequisites & referencesPrerequisites: 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-productindex-1221.asp

– http://www.mellesgriot.com/resourcelibrary/technicalnotes/default.asp

– http://www.newfocus.com/support/support_freelit.cfm

GradingGrading 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 timesLectures: 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