Bragg Grating All-Optical Switches

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By:
Hojjatollah Sarvari
Department of Electrical Engineering
Shiraz University, Shiraz-Iran
December-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