selected applications of polarization interferometry · in which the state of polarization (sop) of...

Selected applications of polarization

interferometry

Faculty of Electronics, Telecommunication and Informatics

Paweł Wierzba

June 2nd, 2017

1

Outline

2

Introduction,

What is polarization interferometry?

Components,

Beware of Polarization,

Liquid Crystals and Other Exotic Materials,

Polarization interferometers,

Detection setups,

Conclusions,

What is polarization interferometry

3

One may read (or hear):

Polarization interferometers are ones in which the two

coherent beams required for interference are produced

from a single source by means of a birefringent beam-

splitter, i.e. use is made of the separation of the E and

O rays.

OR

Polarization interferometry is a branch of optical

interferometry investigating and using interferometers

in which the state of polarization (SOP) of interfering

beams is controlled and stable.


4

Polarization interferometry is a branch of optical

interferometry investigating and using interferometers

in which additional information is obtained from the

state of polarization (SOP) of interfering beams.


5

First polarization interferometer: Jamin 1868,

First polarization microinterferometer

or polarization microscope: Lebedeff 1930,

Jamin, M. J.; Sur un refracteur differentiel pour la lumiere

polarisee; Comptes Rendus Acad.Sc. Paris,

67, 814 (1868).

Lebedeff, M. A. A.; L’interferometre a polarisation at ses

applications; Revue d’Opt., 9, 385 (1930).


6

Polarization interferometry has been the subject of

intense research.

Its scope of applications has steadily increased.

At present the research is concentrated on using

new materials and new states of polarization.

Polarization interferometers employ

several specific birefringent components

and use

dedicated detection setups.

Outline

7

Introduction,


Components,




Detection setups,

Conclusions,

Components

8

Specific birefringent components:

Waveplates (retarders)

Polarizers

Polarization BeamSplitters (PBS)

Prisms (e.g. Wollaston Prism)

... othersPBS

Components

9

Wollaston Prism Can act as a polarizing beamsplitter (large ε)

Can produce interference fringe field (small ε)

WP

Outline

10

Introduction,


Components,




Detection setups,

Conclusions,

Beware of Polarization

11

Beware of Polarization? Why?

E2

E1

E2E1

E2

E1

Because interference depends on

the SOPs of interfering beams

Always check if there is any

potential for problems in your setup


12A, B, Δ – Full description of the SOP

SOP – State Of

Polarization

Classical fully polarized wave


13

Poincare sphere for

visualization

Classical fully polarized wave – Poincare sphere


14

1) SOP changes slowly, compared to the optical

carrier frequency.

2) SOP is constant in the cross-section of a beam.

Classical fully polarized wave

Polarization modes in optical fibers

Vectorial vortex beams

Femtosecond lasers


Fast-changing SOPLocal SOP fitting


16

Fast-changing SOP Local SOP fitting can

be performed


17

Fast-changing SOP Local SOP fitting cannot

be performed


18

Beams with SOP varying in the crossection

Generation of these beams – later


19

Laguerr-Gauss

vector beams

New Journal of Physics 9(2007) 78

(http://www.njp.org/)


20

‘Ultimate disaster’ – a full Poincare beam

A Full Poincare Beam,

contains in its cross-

section each SOP on the

Poincare sphere

Outline

21

Introduction,


Components,




Detection setups,

Conclusions,

Liquid Crystals and Other Exotic Materials

22

1) Liquid Crystals (LCs),

2) Liquid Crystalline Polymers (LCPs),

Reactive Mesogens (RMs)

3) Photo-alignment materials,


23

Liquid Crystals (LCs)

LCs consist of anisotropic molecules

electrical anisotropy

optical anisotropy

LCs can be aligned:

using electric or magnetic field

by confining them between pre-treated

surfaces


24

Liquid Crystals (LCs) – key textures

planar

homeotropic

splayed

tilted


25

LCs can be used to make birefringent optical

components

Waveplates

Wollaston prisms

Main problems

LCs remain liquid (must be confined)

Thicker layers (xx µm) are difficult to align

Liquid Crystal

Glass substrate


26

Liquid Crystalline Polymers (LCPs),


Liquid Crystalline Polymers (LCPs) are Liquid

Crystals whose molecules have reactive

(polymerisable) group on both ends

LCPs can be aligned on a pre-treated surface


27



The same textures as LCs

Under UV illumination polymerization takes place

and a solid birefringent layer is formed


28



λ/4 Waveplate made from RM

AR Coating

Beamsplitter

No need for confinement

= simpler components

Better integration

of optical setups

is possible

ReactiveMesogen

Glass substrate


29



Retardation control:

Birefringence adjustment (temperature)

Process adjustment (composition, ω)


30



Quarter-wave plate

between

crossed polarizers


31

Photo-alignment materials (for LCs and LCPs)

Direction of

orientation

corresponds to the

direction of the UV

radiation polarization


32

Vector Vortex Waveplates

N. Murakami, Opt. Expr. Vol. 21, no. 6 pp. 7400-7410


33

Vector Vortex Waveplates

Outline

34

Introduction,


Components,




Detection setups,

Conclusions,

Polarization interferometers

35

Displacement measurement interferometer

BS – Beamsplitter, WP – Wollaston Prism, L1, L2 – Lens,

DS – detection setup, M1 – Measurement Mirror,

M2 – Reference Mirror.

Beam displacer

can be used

instead of the

Wollaston prism


36

Displacement measurement interferometer

Twice as sensitive as Michelson interferometer

Can be used for pressure measurement


37

Wavelength measurement

Problem:

Fast high-resolution measurement of wavelength emitted by

a tunable semiconductor laser

The wavelength is known to some accuracy,

The laser linewidth is narrow,

High absolute accuracy is not always needed,


38Juncar P and Pinard J, Rev. Sci. Instrum. 53, 939 (1982)

Wavelength measurement: solution


39

lN 0

0

212

l

2

lN

0

0

22



40



41

Problem: λ/8 waveplate

We can make it from LCP


42

Phase contrast microscopy


43


CCD/

CMOS

detector

array

M. Pluta. Advanced Light Microscopy. Vol. 1-3, Elsevier 1989-93


44


Image of an

LED surface

Laser as a

light source?


45

… Qualitative Phase Measurement techniques


46

Vector Vortex coronagraph

N. Murakami, Opt. Expr. Vol. 21, no. 6 pp. 7400-7410

Outline

47

Introduction,


Components,




Detection setups,

Conclusions,

Detection setups

48

Detection Setups

Detection setups convert phase difference of output

beams into one or more intensity signals

Photodetectors convert these signals to electric domain

Electric signals are processed and fed to the output(s)

Detection setups

49

In many instances we can select

‘the best’ detection setup

Detection Setups or ‘Mix and Match’

Detection setups

50

BS

w2

WP1

D2

D4

i -D4 iD3

WP2

QWPHWP

i -D2 iD1

D1

D3

wi

w1

wd1 wd2

wd3

wd4

cos2

12 rtSPii WPiDD

sin2

34 ttSPii WPiDD

Detection setups

51

Detectors

Fringe pattern on detectors

AnalyserA

Beams frominterferometer

Nomarski prismNP

Beam expander

BE

α

This setup can work also with a broadband source

Detection setups

52

Phase measurement range can cover 100s fringes

Detectors

Fringe pattern on detectors

AnalyserA

Beams frominterferometer

Nomarski prismNP

Beam expander

BE

α

Outline

53

Introduction,


Components,




Detection setups,

Conclusions,

Conclusions

Some components, e.g. waveplates, can be reliably

and inexpensively made from Liquid Crystal Polymers

Its scope of application has been expanding, due to

important that this technique provides

Polarization interferometry is a measurement

technique providing high performance solutions

Further research on materials, components and

setups will result in new devices and applications.

54

Price of components specific to this technique limits

its scope of applications

selected applications of polarization interferometry · in which the state of polarization (sop) of...

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