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By:

Hojjatollah Sarvari

Department of Electrical Engineering

Shiraz University, Shiraz-IranDecember-2008

Bragg Grating All-Optical Switches

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Introduction• Bragg Grating

– Their use became practical after 1990

– Bragg gratings act as optical flters because of a stop band

– Light reflected back if its wavelengths falls within stop band of

grating

– A holographic technique is used for making Bragg gratings

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• Kerr Effect– This effect, which was discovered in 1875 by John Kerr, is called

the electrooptical Kerr effect, or simply the Kerr effect

– Electrically induced birefringence that is proportional to the square

of the electric field

– Two special cases:

• The Kerr electro-optic effect, or DC Kerr effect

• Optical Kerr effect, or AC Kerr effect

» The optical Kerr effect, or AC Kerr effect is the case in

which the electric field is due to the light itself or other light

Introduction

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• Bragg Grating + Kerr Effect → All Optical Switching

Introduction

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Nonlinear directional coupler loaded with

Bragg reflector all-optical switch

InP : 300nm

GaInAsP : 450 nm

InP (100) substrate

W= 1.5 um width

L= 3 mm

Lg= 232.5 nm

Operation of Switch:Without control light:

goes out from port 2 and other wavelengths from port 4

With control light:

goes out from port 2 and with other

wavelengths from 4

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• Center wavelength =1545.5 nm

• Extinction Ratio =25 db

• The threshold power of control light is 3 mW

• on-oft ratio could be improved by optimizing the design & fabrication

Nonlinear directional coupler loaded with

Bragg reflector all-optical switch

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Nonlinear directional coupler loaded with

Bragg reflector all-optical switch

• Set-Reset Operation for cross port with control light for λ=1543.42nm

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Optical fiber grating coupler all-optical switch

Signal light is a wavelength tunable

semiconductor laser with λ=1.55 um

Control light is a Nd:YAG laser with λ=1.06um

& 720W peak power

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Optical fiber grating coupler all-optical switch

DEmax=13.2%

FWHM =.5nm for DE λ=1554nm that better than NLDC-BG

Here switch needs lower power of control light compared to NLFC

because more sensitive for the nonlinearity induced effective index variation

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Periodically curved nonlinear waveguides

all-optical switch

is Jacobi elliptic function

For Straight Waveguides:

• is the profile of the waveguide

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Periodically curved nonlinear waveguides

all-optical switch

ω =2π/

Advantages:

Lower critical power

Sharper switching width

Drawback:Longer coupling length

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• In one expriment with these parameters:

For straight coupler (s/w=0) →

For the periodically bent coupler (s/w=2.38) → →

→

Periodically curved nonlinear waveguides

all-optical switch

Pulse width variation

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Refrences

[1] “All-optical switching characteristics in nonlineardirectional coupler loaded with

Bragg reflector”,Katsumi Nakatsuhara,Tetsuya Mizumoto,Seok-Hwan Jeong,Takashi

Shirado,Byong-Jin Ma,and Yoshiaki Nakano, Nonlinear Optics: Materials, Fundamentals,

and Applications, 2000. Technical Digest

Volume , Issue , 2000 Page(s):129 - 131;

[2] “Demonstration of an all-optical switching operation using an optical fiber

grating coupler”,H.Yokota,M.Kobayashi,H.Mineo,N.Kagawa,H.Kanbe,Y.Sasaki,

Optics Communications 281 (2008) 4893–4898;

[3] “All-optical switch with two periodically curved nonlinear waveguides”,

Qiongtao Xie, Xiaobing Luo, and Biao Wu, Physical Review A, 2007 – APS;

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Thanks for your attention