Hollow core planar waveguides and multilayers

Prof. M. Skorobogatiy, review for the course

‘Introduction to Photonic Crystals’

École Polytechnique de Montréal

Montréal, QC, Canada

2

~D

T

R

I=1

R2

R3

R4

T

D2/

D

T T

21

10 2

( ) / (1 ) (1 )

10log ( ( ) / ) [ / ]

bounce

L LL D

o

o

I L I T T

TLoss I L I dB m

L D

TIR silica fiber D=10m =1.55m, loss=0.2dB/km

T=10-6-10-5

Hollow core planar waveguide, scaling relations

REFLECTOR

3 Metallic reflectors

Simplest mirrors present thin layers of metals such as aluminum deposited on glass substrates. Choice of metals will determine reflection characteristics of a mirror.

• Aluminum is the cheapest and least expensive material with a coefficient of reflection of 88%-92% in the visible.

• More expensive is silver with reflectivity of 95%-99% even in the IR, while less than 90% in the blue and UV.

• Most expensive is gold with an excellent reflectivity of 98%-99% in the IR, while poor reflectivity below 550 nm.

Metallic Reflector

Omnidirectional reflection, high material loss in the IR

4 Losses of hollow metallic waveguides

D=100m; =1-10m; T=10-2

Losses=1-10 dB/m

T

R

I=1

D

REFLECTOR

5

1

1

90o0 tan-1(nh/nl)

p-pols-pol2

h l

h l

n n

n n

Reflectance

Contraste d’indice s’augmente

Conventional Dielectric Mirrors

Very low material absorption loss, strong dependence of

reflection characteristics on the light polarization

SiO2-air0.04

AsSe-air0.22

nl

nh

Contraste d’indice s’augmente

Dielectric reflectors

Dielectric mirrors are characterised by very low absorption losses, but their reflection characteristics are strongly dependent of the angle of radiation incidence and polarization. For the s-polarized light reflectivity increases monotonically with an increase of an angle of incidence. However, for a p-polarised light reflectivity goes through zero at a so called Brewster angle.

6 Losses of hollow dielectric waveguides

2,

2 3

5 10[ / ] [ / ]

ln(10) ln(10)

4;

TE TMTE

c c r c

c r rTE TM TE TM TE

cr c c

TLoss dB m Loss dB m

n D Dn

nT T T Loss Loss

cn

D=100m; =1-10m;

nc=1; nr=1.5

LossesTE=0.04-4 dB/cm

T

R

I=1

D

REFLECTOR

~Drn

cn

7 ARROW waveguides

=1.55mm

LossesTE=0.2 dB/cm

8 ARROW multilayer waveguides

9

D. Yin et al. 14 June 2004 / Vol. 12, No. 12 / OPTICS EXPRESS 2710

dc~3.7m

12m

Capillary1 layer

2 layers3 layers

Sensor applications - putting the light where the analyte (gas) is

Planar antiresonant reflecting optical (ARROW) waveguides, SiN/SiO2 (2.1/1.46)

Omnidirectional reflectorsOR

high index contrast multilayers

11

6 9 1 2 1 50

5 0

1 0 0

0

5 0

1 0 0

0

5 0

1 0 0

0

5 0

1 0 0

0

5 0

1 0 0

normal

450 s

450 p

800 p

800 s

Wavelength (microns)

Te / polystyrene

normal=0o

=90o

Ep

Es

Omnidirectional Dielectric Mirrors

Reflection for all angles of incidence and polarizations

Multilayer dielectric reflectors

Omnidirectional reflection - for any incoming polarization and any angle of incidence radiation is completely reflected in a certain frequency band.

12 Omnidirectional dielectric reflectors

normal=0o

=90o

Ep

Es

13

normal=0o

=90o

Ep

Es

Omnidirectional dielectric reflectors

cω = β/n

cncω = β/n

14

normal=0o

=90o

Ep

Es

Omnidirectional dielectric reflectors

cω = β/n

cn

cω = β/n

When cladding index nc is increased beyond a critical value, omnidirectional reflectivity is lost.

Omnidirectional reflectorsSURPRIZE !!!

low index contrast multilayers

16 All-polymer multilayers

nl

nh

17 Giant birefringence polymer multilayers

18 Giant birefringence polymer guides