applications of soi based optical mems in fiber

8/7/2019 Applications of SOI Based Optical MEMS in Fiber

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Applications of SOI based optical

MEMS in fiber opticscommunication and others


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Key features of MEMS technology

Array ability: which is the term that we use for

the ability to place tiny devices in large-scale

arrays

Reconfigurability: i.e. the ability to reconfigure

the optical properties, spatially and temporally,

via localized micro-actuation and/or deformation

Nanopositioning: nanoscale precision control ofposition and alignment for microscale devices


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Optical-MEMS or MOEMS

Three Technologies coming together

Micro-optics:Semiconductor Laser Waveguide

Micro-mechanics:Resonant Gate transistor

Micro-Electronics:IC fabrication


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In OFC

There are four main domains:

Amplifiers

Switches or Optical Cross Connectors (OXC) 2x2, 4x4, NxN

Variable Optical Attenuators (VOA)

Filters


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Overview of Silicon on Insulator (SOI)

Technology Polycrystalline silicon on top of the buried

SiO2 layer (100mm -2m -75 m)

Photolithography: Patterning anddepositing

DRIE: narrow structures of about 2m to

5m can be achieved with very smoothsidewalls.

The buried SiO2 serves as etch stop forDIRE as etching rate is different indifferent directions

The resist is removed by oxygen plasma

etching. Buried Sio2 is removed by etching with 50%

conc HF acid

SiO2 pedestals remains serves asinsulators between different electrodes

Deposition of Gold for conductivity andproper reflection of mirror.


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2x2 optical switch

Two input two output fibers in 75um high grove

Their endfaces all meet at one point,where a movable gold-coated mirroris located. This way, the light of

either one of the input fibers can beswitched to either one of the outputfibers

Refractive index matching fluid:reduces two effects: first the Index stepbetween the fiber endfaces and theambient and Secondly the divergence of

the freely propagating light; hermeticallysealed

The mirror is attached to a longbeam which is electrostatic allyactuated by comb drive

The optical and mechanical properties

of the switch are

excellent. The insertion loss is between

0.3 and 0.5dB.

The switching time is about 500s


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Electrostatic Comb drive Actuators

Driving Principle:

Electrostatic force

generated when voltage

is impressed between

both sides of the comb-

drive electrodes


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---Polyimide is used as the structural

material. Since polyimide is an insulator,which cannot be driven electrostatically

by impressed voltage if it is left as it is,

depositing a metallic membrane on

polyimide

---- The structure is the one that supports the

fixed electrode by the anchor of the electrode.

This structure makes it possible to insulate the

fixed electrode and the movable electrode

because the metallic membranes cannot be

formed in the shadow parts of fixed electrodeswhen metals are accumulated from the upper

direction by a sputtering technique after

fabricating the actuator structures


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Fabrication


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4x4 switch design

Consists of 16 2x2 MEMS switches that will beoptically interconnected by integrated opticalwaveguides

Top chip holding the waveguides and the electricalconnections for the switches. The two chips will becombined by standard flip chip bonding technology.


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Variable Optical Attenuators (VOA) Losses due to absorption,

bending, scattering

Amplification wavelength

dependent

Channels are split of different

intensities

WDM-VOA-WM

MEMS based VOA: A mirror that

is rotated by 82 to the axis of

light propagation can move

linearly between two opposing

fibers that are held by small leaf

springs in two U-grooves. The

slight tilt prevents the backreflection into the input fiber.

The attenuation efficiency

versus the driving voltage is

depicted.

Not linear hence has to be

calibrated before use.


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Fourier transform spectrometer

FT spectroscopy is used for

week and extended sources

High cost; miniature

reduced cost

FTS are based on MichelsonInterferometer configuration

with scanning mirrors.The output signal of the interferometer is the

variation of the light intensity IR as a function

of the opticalpath length d. The relation ofIRto d is referred to as the interferogram. The

wavelength power spectrum and the recorded

interferogram IR(d) are related by a Fourier

transformation. Therefore, a spectrum of a

light source can be obtained by simply

recording IR(d) and a subsequent FT.


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MEMS based Accelerometer

The optical source is an LED

The optical detection utilizes the partial and simultaneous lightcoupling from one source fiber into two output fibers

The light of the source fibers hits the point of a V-shaped mirror,which splits and couples the light evenly into the two identicaloutput multimode fibers

The output fibers guide the light to two photodiodes allowingdifferential measurement of optical fiber.


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Advantages of Optical MEMS

More sensitive than electrical sensors based

systems

Higher dynamic range Free from electromagnetic and electrical

interference noises

Thermal Mechanical noise is negligible High arability due to miniature in size

Nano-positioning, very precise

applications of soi based optical mems in fiber

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