materials for photonic applications glasses, optical...

Materials for Photonic Applications

Glasses, Optical Fibers and Sol-Gel Materials

www.sampaproject.com

Sidney J.L. Ribeiro, Edison Pecoraro, Marcelo Nalin, Younes Messaddeq

and collaborators

sidney@iq.unesp.br

Project UNESP-PROPG-NEaD-TIC (UNESP Graduate Studies Office)

Graduate Robson R. Silva and Undergraduate Fernando E. Maturi

April-June- 2013

www.iq.unesp.br www.unesp.br

Rio Grande do Sul

South of Brazil

Barbecue, chimarrão,

beautiful places to visit!!

GLASSES

OPTICAL PROPERTIES

CLASS 3

"To focus, coordinate and promote educational and research activities

across the globe to introduce new functionality in glass"

http://www.lehigh.edu/imi/

Professor Himanchu Jain

Lehigh University (Betelehem, PA, USA)

http://www.lehigh.edu/matsci/faculty/jain/jain.htm

The International Materials Institute for New Functionality in Glass (IMI-NFG) was

established in August 2004 through an initiative of the National Science Foundation

for enhancing research collaborations between US researchers and educators

and their counterparts worldwide.

It is also a collaboration between Lehigh University and Penn State University.

Go the IMI webiste or contact Professor Jain

for more informations!

Light- Special kind of electromagnetic energy

Propagates in space

c= 3.108 m/s in vacuum (0,03% less in air and 30% less in glass)

Refractive index- n v(vacuum)/v(material)

Optical waves propagate through insulators

With characterisitics determined by:

-The dielectric constant and refractive index of the

material

-any absorptive or scattering process

As a consequence, insulators have a broad window of transparency

over somepart of the optical spectrum.

In this transparency window the dielectric constant generally has a weak dispersion.

Therefore the material transmits light with very little loss.

Wavelengths outside de transparency regions can induce strong polarization processes,

that can cause a dispersion in the dielectric constant or refractive index,

with an associated increase in propagation loss or absorption

Ordinary glasses are highly transparent in the visible

for three main reasons:

1- Their polatization processes are either too slow or too fast to keep up with

the oscillations in electromagnetic fields associated with the visible optical wave;

Consequently the refractive index is only weakly dependent on wavelength in that region

of the electromagnetic spectrum

2- Their constituents do not have electronic states that allow free-electron or

bound-electron transitions in the visible

3- Their microstructure is homogenous and isotropic, and their refractive index is

dependent on neither spatial position nor direction

Ref. “Optical Materials” by Joseph H. Simmons and Kelly S. Potter, Academic Press, 2000

Optical properties of glasses

Ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

-Good optical properties

-difficult preparation

-Bad optical properties

-easy preparation

-Good optical properties

-easy preparation

REFLECTION

ABSORPTION

SCATTERING

TRANSMISSION

INCIDENT LIGHT ON A MATERIAL SURFACE

Glasses are

isotropic

REFLECTION

(FRESNEL EQUATION)

In the transparentregion =0

= extintion coeffcient

n= n+ i.

2

1

1

n

nR valid for < 20o

If n=1.5 R=4% at each surface

ABSORPTION

= absorption coefficient

c

2

Relationship between the absorption coefficient and the extinction coefficient

SCATTERING

Rayleigh scattering- results from microscopic fluctuations of the density-

Light is sent to multiple directions. There is no energy transfer to the scatterer

Why is the sky blue??

http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html

Take a look at

The change of sky colour at sunset (red nearest the sun, blue furthest away)

is caused by Rayleigh scattering by atmospheric gas molecules which are much

smaller than the wavelengths of visible light.

The grey/white colour of the clouds is caused by Mie scattering by water droplets

which are of a comparable size to the wavelengths of visible light.

http://en.wikipedia.org/wiki/Mie_theory

Scattering from

particles.

Mie Scattering

Independent of the

wavelength

TRANSMISSSION

If the optical quality is good,

scattering may be descarded

and R+T+A=1

Refraction effect

Pencil in the

water

vertical

Pencil in the water

inclined

2211 sennsenn

Snell-Descartes Law

Reflection and refraction

Total Internal Reflection

According to Snell-Descartes Law, 2

1

21 sen

n

nsen

If n2>n1 then 1>2

For a given angle c the refracted beam will be paralel to the surface (1=90o)

We call this angle “critical angle”

The critical angle value will be given by senc=n1/n2

For any angle 2 larger that the critical angle, light will be completely

reflected to the medium. This process is what we call

Total internal reflection We will come back to this to

explain light guiding in optical fibers

The deviation a light beam will suffer

will depend on its relative velocity in the two media

The relative refractive index (n21)- ratio of the two velocities

n21=v1/v2= n2/n1

Absolute value (n)- When the medium 1 is vacuum (v1=c)

C= 300000 km/s and n will be always larger than 1

In ordinary glass v=200000 km/s

And then n= 300000/200000=1.5

Refractive index- Basics

Material Refractive index

air 1

water 1.33

glass 1.5

glicerine 1.9

Ethyl alcohol 1.36

diamond 2.42

Acrylic 1.49

Fused silica 1.46

ZBLAN glass 1.5

Lead silicate glass 2.5

Refractive index for some materials

What if the refractive index is negative??????

...the incident and the refracted waves lie on the same side of the normal to

the interface between a standard medium and the new medium with

negative refractive index (“left-handed refraction”)...

Normal refraction Left-handed refraction

In the transparent region, dispersion

is “normal”

In resonance regions the dispersion

is “anomalous”. The refractive index

value goes to infinity

Refractive index as a function of the wavelength

Dispersion of the refractive index

Coming back to normal refraction basics

Abbe number: CF

d

nn

n

1

The optical dispersion may be evaluated

through the Abbe Number

(Concerning the d-line some authors substitute the Na lamp line at 589,3nm for the He line at 587.56nm)

Ref. “Optical Materials” by Joseph H. Simmons and Kelly S. Potter, Academic Press, 2000

The lower the Abbe number

The greater the dispersive power

.

Glasses can then be categorised by their composition and position on the diagram.

This can be a letter-number code, as used in the Schott Glass catalogue

and shown in the figure

Abbe numbers are used to calculate the necessary focal lengths of achromatic

doublet lenses to minimize chromatic aberration.

Flint glassesCrown glasses

Sellmeier equation- dispersion of the refractive index for a single-component glass

Sellmeier coefficients- A, B and C- determined experimentally for a variety of

different materials and may be found in the literatureIn practice given the refractive index at some given wavelengths,

one can fit the Sellmeier equation to obtained the coefficients A, B and C

Silica

A=1.099433

B=10974.1

C=9.5988x10-9

Refractive index measurements

Abbe refractometer

Measures the angle of incidence required to just begin total internal reflection

(critical angle) for light propagating from a standard glass hemisphere of high

Index to a sample of lower index- Accuracy- 2x10-3

Ref. “Optical Materials” by Joseph H. Simmons and Kelly S. Potter, Academic Press, 2000

Refractive index measurements

Minimum-deviation prism goniometer

The most accurate method for measuring refractive index.

1- Position the source to one side of the unknown

prism and measure the minimum angle of deviation

2- Rotate the prism 1800 and repeat

3- This gives a measure of 2m from which the

refractive index can be calculated

The accuracy is 5x10-6 if the angle

can be measured with an accuracy

of 0.5 angular seconds

Ref. “Optical Materials” by Joseph H. Simmons and Kelly S. Potter, Academic Press, 2000

Refractive index measurements

Prism coupling

Metricom Model 2010- Prism Coupler

Lasers – 1540nm, 633nm, 543.5nm

Accuracy is comparable with that of

minimum deviation method

Critical angle

Refractive index measurements

Refractometers

The method consists of the measurement of the angle of a mirror required to send

a collimated optical beam back along its incoming track.

The refractive index of the V-block must be known to the same accuracy as the

desired for the unknown sample.

Ref. “Optical Materials” by Joseph H. Simmons and Kelly S. Potter, Academic Press, 2000

Refractive index measurements

Ellipsometry

Ref. “Optical Materials” by Joseph H. Simmons and Kelly S. Potter, Academic Press, 2000

An ellipsometer is usually used to measure the thickness and refractive index of

films deposited on a substrate.

With an appropriate standard, the same method can be applied to index measurements

on bulk samples.

Monochromatic light is passed through a polarizer (Glan-Thomson calcite prism)

and a quarter-wave compensator (mica plate with 45º retardation) to give

elliptically polarized light.

This light is incident upon a sample surface at a specified angle.

The reflected light is then detected through an analyser (Glan-Thomson calcite

prism) and both the polarizer and the analyser angles are varied to find the

maximum extinction of the reflected light. The values obtained consist of the

polarizer angle (P), the analyser angle (A) and the angle of incidence.

Refractive index measurements

Becke line method

Ref. “Optical Materials” by Joseph H. Simmons and Kelly S. Potter, Academic Press, 2000

Most used in optical mineralogy- Small glass fragments in an immersion liquid

of known refractive index, and observed under a microscope.

As the microscope stage is moved away from focus, there will be a bright line

contouring the perimeter of the glass sample. This is the “Becke Line”.

If the refractive index of the immersion liquid is lower than that of the glass, the

Becke line will move inside the object when the distance between the objective

lens and the specimen is increased. Decreasing the distance will cause the Becke

Line to move outside the sample.

If the immersion liquid index is higher that that of the sample,

the Becke line will move in the opposite direction

Different liquids are used so as to bracket the unknown index

The bracket is narrowed until the desired degree of accuracy is reached.

Finely graduated liquids can yield n= 0.02

Refractive index measurements

Femtosecond transit time method

Ref. “Optical Materials” by Joseph H. Simmons and Kelly S. Potter, Academic Press, 2000

The white light pulse from a Ti-sapphire femtosecond laser is used.

By decomposing the transmitted pulse into its component colors the time taken

for each wavelength to transmit through the sample can be calculated, giving

the refractive index for each wavelength directly.

Accuracy is good to the second decimal place for a sample1mm thick

100fs pulse width

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

Considering thin films,

refractive index and thickness

can be obtained together by using:

Soda-lime silica glass- Absorption spectrum

Multiphonon

processes

Harmonics of

fundamental

vibrational

modes Energy gap

Electronic

transitions

valence band

conduction band

Minimum depends on the

glass composition

A=5.10-5 (1cm)

A=10-7(1cm)

96% of the

signal after

1km

Attenuation- "decibels"

(dB)= 10 log(P1/P2) P1-in P2-out

3dB P1/P2= 2 (signal is half of the initial)

1ppm OH-- 4dB/k m at 1380nm

Quizz number 3- question 1

270 kms of fiber

Araraquara

São Paulo

1W, 1.5 m

?W

Attenuation of a silica fiber at 1.5 m

0.2 dB/km

http://en.wikipedia.org/wiki/ZBLAN

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

Spectrometers

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

Fourier Transform Infrared (FTIR) spectrometers

In the infrared, which is the region of molecular vibrations,

wavenumbers range from 300 to 5000 cm-1 (33 to 2 m))

interferometers are used instead of dispersion monochromators

Michelson Interferometer

The FT analysis of the

resulting interferogram (f(cm))

gives us

the infrared spectrum (f(cm-1))

Light sources

-Black body radiation of a

heated silicon carbide coil

Detectors

-Pyroelectric detectors

-MCT (HgCdTe) – highly sensitive

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

E

Size effect in the band-gap value

“Quantum confinment in quantum dots” (“Quantum dots”- QD)

1128 nm

146 nm

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

Ref. “Optical Materials”

by Joseph H. Simmons and Kelly S. Potter,

Academic Press, 2000

The Bohr diameter defines the smallest

structure that will exhibit bulk behavior

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

100 200 300 400 500 600

Inte

nsid

ad

e (

un

.arb

.)

Número de onda (cm-1)

Raman spectrum of a fluorindate glass

Highest energy

vibracional mode

510 cm-1 (19,6m)

2 important consequences

Non-radiative rates for transitions

Between lanthanides excited states

IR absorption edge

The lower the non-radiative rates,

The more efficient the radiative emission

will be!

Highest energy vibrational modes

Silica- 1100cm-1 (9,1m)

Fluorides- 510 cm-1 (19,6m)

Chalcogenides- 300 cm-1 (33,3m)

We will come back to this!

ref- P.Lucas- Glass Properties- 2nd Virtual Glass Course - International Materials

Institute for New Functionalilty in Glasses (http://www.lehigh.edu/imi/)

http://electronics.howstuffworks.com/gadgets/automotive/in-dash-night-vision-system3.htm

Infrared Fibers

Chalcogenide glasses are transparent in the domain where the vibrational

signature of most molecules lies: 2-12 microns

A cone penetrometer system using chalcogenide

fiber can be used for the in-situ detection of

contaminants and water in soil.

A chalcogenide fiber is connected to a

headened optical analysis system (top and center),

and is inserted into the soil to be tested.

The IR signals reflected from the soil and

transmitted through the fiber to the FTIR

in the truck are used to identify

the contaminant marine diesel fuel (DFM) (bottom)

From Laser Focus World

http://www.laserfocusworld.com/articles/print/volume-41/issue-4/features/chalcogenide-optical-fibers-target-mid-ir-applications.html

Confederations Cup- 2013

Brazil Champion

Brazil 3 Spain 0

The champion is back!!!

http://www.youtube.com/watch?v=SS9k6ZoE3v0

http://news.yahoo.com/brazil-beats-spain-3-0-win-confederations-cup-000418525.html