[PPT] - Advanced Vitreous State The Physical Properties of Glass Active PowerPoint Presentation

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Advanced Vitreous State – The Physical Properties of Glass

Active Optical Properties of Glass Lecture 21: Nonlinear Optics in Glass-Applications

Denise Krol Department of Applied Science University of California, Davis Davis, CA 95616 dmkrol@ucdavis.edu

dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 1

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 2

Nonlinear optical susceptibilities

(1)

( ) = P(1)()

E() = Ne2
m

1

2 2 i

General formalism:

= P(1)(t) + P(2)(t) + P(3)(t) + ...

P(t) = (1)E(t) + (2)E(t)2 + (3)E(t)3 + ...

E and P can be written as sum of frequency components:

E = E( j)e

i j t j

P =

P( j)e

i j t j

2( p = m + n) =

P(2)( p) E(m)E(n) = Nae3 m2 D p

( )D n

( )D m ( )

(3)(q = m +n +p) = Nbe4 m3 D(q)D(m )D(n)D(p)

utput frequency

input frequencies, pos or neg

D( j) = (0

2 j 2) i j

Value of χ(n) depends on frequencies

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 3

Nonlinear optics in glass

2nd-order nonlinearities

In normal glasses χ(2)=0

3nd-order nonlinearities

All materials, including glasses, have a χ(3)
In glass there are only three independent χ(3) tensor elements
χ(3) processes involve the interaction of 3 input waves to generate a polarization

(4th wave) at a mixing frequency with 3 different input frequencies there are many possible output frequencies

Strength of generated signal depends on propagation length
optical fibers!
Phase matching: Δk=k4-k3-k2-k1=0

(3)(3 = + + ) (3)( = + )

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 4

Units in nonlinear optics

linear nonlinear

r P (t) = (1) r E (t)+ (2) r E (t)2 + (3) r E (t)3 +

Gaussian system of units

r P (t) = 0 (1) r E (t) + (2) r E (t)2 + (3) r E (t)3 +

[ ]

MKS system

ε0 = permittivity of free space = 8.85 x 10-12 F/m

MKS system Gaussian system Electric Field, E V/m statvolt/cm Polarization, P C/m2 statvolt/cm Intensity, I Intensity, I W/m2 erg/cm2-sec χ(2) m/V

cm/statvolt, esu

χ(2) (MKS) = 4.189 x 10-4 χ(2) (Gaussian) χ(3) m2/V2 (cm/statvolt)2, esu χ(3) (MKS) = 1.40 x 10-8 χ(3) (Gaussian)

I = nc 2 E

2

I = 2n 0 µ0

1/ 2

E

2

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 5

χ(2) can be induced in glass by thermal poling

The induced χ(2) can be examined via second harmonic generation (SHG)

ω ω 2ω

SHG process

Second order optical nonlinearity (χ(2)) = 0 in glasses because glasses are isotropic To induce a χ(2) in glasses Thermal poling technique silica DC + Heat

~ 1 mm Thermal poling experiment

t (min.) T (°C)

280 25

V (kV)

3

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 6

Thermal poling-proposed mechanism

χ(2) ∝ χ(3) EDC + - + - + - + - + + + + + +

HV,T

+

RT

- - - - - - - - - -
- - - - - - - - - -
- - - - - - - - - -

Z

EDC

//

Z

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 7

Effect Nonlinear index Stimulated Raman scattering Nonlinear photoinduced changes n =n0+n2I n2 ~ χ(3)(ω=ω+ω−ω)

χ(3) phenomena and applications in glass

Applications Optical switching Supercontinuum generation Raman amplifiers and lasers Fs laser structuring

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 8

Nonlinear optical switch

Signal Switching Pulse Output Nonlinear Material Waveguide Interferometer 1 2

Without switching pulse: waves in leg 1 and 2 interfere destructively, no output With switching puse: due to the nonlinear interaction, the switching pulse causes a phase shift in the part of the signal pulse propagating in leg 2. As a result waves in 1 and 2 interfere constructively, output

From P.Thielen, PhD Dissertation, UC Davis, 2004

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 9

Material dependence of n2

ω0 Classical anharmonic electron oscillator, far from resonance:

(3)( = + ) e4 m30

6d5

ω

n2() = n2(0) 1 h ES

2
3.5

n2(0) = 3.4(n0

2 + 2)3(n0 2 1)d2

n0

2ES 2

1020

Bond polarizability model by M. Lines: Frequency dependence Long wavelength limit:

Es is Sellmeier gap

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 10

Material dependence of nonlinear index

n2 (10-16cm2/W)

T. Monro et al, Annu. Rev. Mater. Res. 2006. 36:467

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 11

distance through fiber

self phase modulation

pulse of light

(t) = 0 0n2L c dI(t) dt

instantaneous frequency

generation of new frequency components

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 12

Supercontinuum generation in microstructured fibers

From Philip Russell et al. Source:www.bath.ac.uk/physics/groups/opto/rse/holeyfibres.html core

cladding guidance properties determined by size and pattern of holes unusual dispersion high nonlinearity propagation of pulsed (100fs) Ti-sapphire laser light( 800 nm) results in supercontinuum generation : 400-1600 nm

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 13

Raman gain

P NL(S,z) = 6R(S) AL

2 ASeikSz

R(S ) = N 6m

q
2
1

v

2 (L S )2 + 2i(L S )

ωL ωv ωS

Stokes Raman scattering vibrational energy At high laser intensities: stimulated Stokes Raman scattering

fiber

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 14

χ(3) phenomena and applications in glass

Effect Nonlinear index Stimulated Raman scattering Nonlinear photoinduced changes Applications Optical switching Supercontinuum generation Raman amplifiers and lasers Fs laser structuring

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Interaction of glass with sub-bandgap, focused, fs laser pulses

cw laser at 800 nm silica glass ultrashort (100fs) pulses and tight focusing (µm-size spot) permanent modification deposition of laser energy into glass at low to moderate intensities sub-bandgap light is transmitted

photon energy

at high intensities multiphoton absorption occurs

Light-matter Interaction is localized in time and space -> 3-D control of modification

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Schaffer et al, MRS Bull 31, 620 (2006)

How does the material change on an atomic scale? 4) Proposed mechanism:

Shockwave propagation

(microexplosion)

Fast heating and cooling

3) Plasma formation 1) Multiphoton absorption 2) Avalanche photoionization 5) Modified spot

Femtosecond laser modification in glass

?

energy abs ~100 fs energy

dissipation ~ 1µs

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dmkrol@ucdavis.edu Advanced Vitreous State - The Properties of Glass: Active Optical Properties of Glass 17

Davis et. al, Opt. Lett., 21, 1729 (1996)

130 fs ~ 1 µJ of energy 800 nm bulk glass waveguide

Properties:

Refractive index
Absorption
Composition (phase separation)
Valence state (Sm3+ -> Sm2+)
Crystal nucleation (Ag and Au colloids in glass)

Femtosecond laser pulses can modify various glass properties

Applications: photonic devices lab-on-chip data storage

ptical switching

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Some references

NLO Books:

N. Bloembergen, Nonlinear Optics

R.W. Boyd, Nonlinear Optics NLO in Glass Reviews

E. M. Vogel, M.J. Weber, D. M. Krol, “Nonlinear optical phenomena in glass”, Phys.
Chem. Glasses 32, 231 (1991).
K. Tanaka, “Optical nonlinearity in photonic glasses”, J. Materials Science: 16, 633