Report Silicon Photonics (2)

8/12/2019 Report Silicon Photonics (2)

1/27

A Seminar Report on Silicon Photonics

CHAPTER 1

CONCEPT OF SILICON PHOTONICS

We all expect fast, free-flowing bandwidth whenever and wherever we connect with theworld. However, there is a problem, as newer faster microprocessors roll out, the copper

connections that feed those processors within computers and servers will prove inade uate to

handle the crushing tides of data. Here is a better wa!" replace the copper with optical fiber and

the electrons with photons. #hat is the promise of silicon photonics" affordable optical commu-

nications for ever!thing. $t will let manufacturers build optical components using the same

semiconductor e uipment and methods the! use now for ordinar! integrated circuits, thereb!

dramaticall! lowering the cost of photonics. $ts overarching goal is to develop high-volume, low-

cost optical components using standard %&'S processing-the same manufacturing process used

for microprocessors and semiconductor device. #he onl! wa! for photonics to move into the

mass mar(et is to introduce integration, high-volume manufacturing, and low cost assembl!-that

is, to )Siliconi*e) photonics. +! that, we mean integrating several different optical devices onto

one silicon chip, rather than separatel! assembling each from exotic materials.

#he researchers believe that with this development, silicon photonic chips containing

do*ens or even hundreds of h!brid silicon lasers could someda! be built using standard high-

volume, low-cost silicon manufacturing techni ues side b! side, communicating with each other

to form a supercomputer far be!ond the scale of toda! s fastest computer. Silicon photonics

technolog! has the potential to use the power of optical networ(ing inside computers and to

create new generation of miniaturi*ed and low-cost photonic components, among other

applications.

$n one potential use, man! boards containing these Silicon-photonic chips would coexist.

#hus one can now see a path to integrating silicon h!brid lasers, photo detectors, modulators, andwaveguides into a single highl! integrated photonic chip capable of transmitting #bit s of

information down a single optical fiber all on a piece of silicon the si*e of !our fingernail. #he

chips will also be well suited for use in general data communications and computing.

/epartment of 0lectronics 1 #elecommunication 0ngineering /r. +abasaheb Ambed(ar #echnological 2niversit!, 3onere.


2/27


CHAPTER 2

INTRODUCTION OF SILICON PHOTONICS

$ts overarching goal is to develop high-volume, low-cost optical components usingstandard %&'S processing the same manufacturing process used for microprocessors and

semiconductor device. /espite silicon4s shortcomings, researchers have been stud!ing silicon

photonics for more than 56 !ears, starting with Richard Soref4s pioneering wor( in the midioaos

at the Air 7orce Research 3aborator!. Since then, there have been a host of silicon photonics

brea(throughs at %ornell 2niversit!, the &assachusetts $nstitute of #echnolog!, the 2niversit!

of %alifornia at 3os Angeles, the 2niversit! of %atania in Sicil!, the 2niversit! of Surre!, $+&,

$ntel, and elsewhere.

With optical interconnects in and around our des(top computers and servers, we4ll

download movies in seconds rather than hours and conduct lightning-fast searches through

gigab!tes of image, audio, or text data. &ultiple simultaneous streams of video arriving on our

P%s will open up new applications in remote monitoring and surveillance, teleconferencing, and

entertainment $n theor!, !ou could push fiber up to 86 trillion bits per second a rate that would

deliver the text of all the boo(s in the 2.S. 3ibrar! of %ongress in about a second. 2nli(e

electronic data, optical signals can travel tens of (ilometers without distortion or attenuation.

9ou can also pac( do*ens of channels of high-speed data onto a single fiber, separating the

channels b! wavelength, a techni ue called wavelength-division multiplexing. #oda!, :6

separate signals, each running at 6 gigabits per second, can be s uee*ed onto a hair-thin fiber.

#oda!4s devices are speciali*ed components made from indium phosphide, lithium

niobate, and other exotic materials that can4t be integrated onto silicon chips. #hat ma(es their

assembl! much more complex than the assembl! of ordinar! electronics, because the paths that

the light travels must be painsta(ingl! aligned to micrometer precision. #he onl! wa! for

photonics to move into the mass mar(et is to introduce integration, high-volume manufacturing,

and low cost assembl!-that is, to )Siliconi*e) photonics. +! that, we mean integrating several

different optical devices onto one silicon chip, rather than separatel! assembling each from

exotic materials.

/epartment of 0lectronics 1 #elecommunication 0ngineering 5/r. +abasaheb Ambed(ar #echnological 2niversit!, 3onere.


3/27


2.1 Photon:

A photon is a discrete bundle of light energ!. Photons are alwa!s in motion and, in a

vacuum, have a constant speed of light to all observers, at the vacuum speed of light. #he photon

is an elementar! particle, despite the fact that it has no mass. $t cannot deca! on its own,although the energ! of the photon can transfer ;or be created< upon interaction with other

particles. Photons are electricall! neutral and are one of the rare particles.

According to the photon theor! of light, photons-

&ove at the speed of light in free space

Have *ero mass and rest energ!.

%arr! energ! and momentum.

%an be destro!ed created when radiation is absorbed emitted.

%an have particle-li(e interactions ;i.e. collisions< with electrons and other particles, suchas in the %ompton 0ffect .

2.2 Silicon:

$t is semiconductor element which have s!mbol of silicon is Si and atomic number :.

Second onl! to ox!gen in abundance in 0arth4s crust= it never occurs free but is found in almost

all roc(s and in sand, cla!, and soils, combined with ox!gen as silica. Pure silicon is a hard, dar(

gra! solid with a metallic luster and the same cr!stal structure as diamond . $t is an extremel!

important semiconductor doped with boron, phosphorus, or arsenic, it is used in various

electronic circuits and switching devices, including computer chips, transistor s, and diode s.

Silicon presents a uni ue material for this research because the techni ues for processing it

are well understood and it demonstrates certain desirable behaviors. 7or example, while silicon is

opa ue in the visible spectrum, it is transparent at the infrared wavelengths used in optical

transmission, hence it can guide light. &oreover, manufacturing silicon components in high

volume to the specifications needed b! optical communication is comparativel! inexpensive.

/epartment of 0lectronics 1 #elecommunication 0ngineering >/r. +abasaheb Ambed(ar #echnological 2niversit!, 3onere.
http://physics.about.com/od/quantumphysics/a/comptoneffect.htmhttp://www.encyclopedia.com/doc/1B1-363585.htmlhttp://www.encyclopedia.com/doc/1B1-361970.htmlhttp://www.encyclopedia.com/doc/1B1-362666.htmlhttp://www.encyclopedia.com/doc/1B1-378213.htmlhttp://www.encyclopedia.com/doc/1B1-381075.htmlhttp://www.encyclopedia.com/doc/1B1-362777.htmlhttp://physics.about.com/od/quantumphysics/a/comptoneffect.htmhttp://www.encyclopedia.com/doc/1B1-363585.htmlhttp://www.encyclopedia.com/doc/1B1-361970.htmlhttp://www.encyclopedia.com/doc/1B1-362666.htmlhttp://www.encyclopedia.com/doc/1B1-378213.htmlhttp://www.encyclopedia.com/doc/1B1-381075.htmlhttp://www.encyclopedia.com/doc/1B1-362777.html


4/27


Silicon4s (e! drawbac( is that it cannot emit laser light, and so the lasers that drive optical

communications have been made of more exotic materials, such as ?indium phosphide and

?gallium arsenide . However, silicon can be used to manipulate the light emitted b! inexpensive

lasers so as to provide light that has characteristics similar to more-expensive devices. #his is

@ust one wa! in which silicon can lower the cost of photonics.

2.3 Photonics:

Photonics is the science of generating, controlling, and detecting photons , particularl! in

the visible and near infra-red spectrum, but also extending to the ultraviolet ;6.5 6.>8 Bm

wavelength


5/27


Historicall!, the term photonics onl! came into common use among the scientific

communit! in the DC6s as fiber optic transmission of electronic data was adopted widel! b!

telecommunications networ( operators. At that time, the term was adopted widel! within +ell

3aboratories . $ts use was confirmed when the $000 3asers and 0lectro-'ptics Societ!

established an archival @ournal named Photonics #echnolog! 3etters at the end of the DC6s. A

huge further growth of photonics can be expected for the case that the current development of

silicon photonics will be successful.

2.4.2. Need silicon photonics:

$ntel cofounder Gordon &oore pro@ected that the number of transistors on a computer

chip will double ever! 5 !ears. ; DE8


6/27


telephone and $nternet traffic among service providers around the world. what about moving

large amounts of data inside !our computer

%omputer manufacturers don t use fiber optics to move data from component to

component inside !our P% because it s expensive to use and implement fiber optics insidecomputers, which is wh! the! rel! on electrical copper lin(s. However, as computer components

and chips wor( faster, those slower copper lin(s will begin to hold bac( P%s. #he copper lin(s

won t be able to move data uic(l! enough to let the chips and other components wor( at top

speed. #he chips ma! be waiting for data to arrive over the copper lin(s, leaving them idle. 7iber

optics can carr! thousands of times more data than copper cable lin(s.

Silicon photonics ma! be the answer to these problems. Silicon photonics brings laser

technolog! to silicon, allowing for the use of fiber optic communications from a silicon chip.+ecause silicon is inexpensive, implementation of fiber optics in man! new areas including

among servers, across networ(s, and inside computers ma! become possible. #o understand how

optical data might one da! travel through silicon in !our computer, it helps to (now how it

travels over optical fiber toda!.

7irst, a computer sends regular electrical data to an optical transmitter, where the signal is

converted into pulses of light. #he transmitter contains a laser and an electrical driver, which

uses the source data to modulate the laser beam, turning it on and off to generate s and 6s.

$mprinted with the data, the beam travels through the glass fiber, encountering switches at

various @unctures that route the data to different destinations. $f the data must travel more than

about 66 (ilometers, an optical amplifier boosts the signal. At the destination, a photo detector

reads and converts the data encoded in the photons bac( into electrical data.

CHAPTER 3

/epartment of 0lectronics 1 #elecommunication 0ngineering E/r. +abasaheb Ambed(ar #echnological 2niversit!, 3onere.


7/27


(UILDIN) (LOC*S OF SILICON PHOTONICS

3.1. Int#o+,ction

Silicon Photonics incl,+$s -ollo'ing -lo' o- P#oc$ss -lo'

1. Light source (low cost external laser)

2. Guide light (silicon on insulator)

3. odulation (!i "! capacitor de#ice)

4. $hoto detection (!i %ased photo detector)

A laser generates light this light ma! be filtered and tuned to a specific wavelength. $t is

then modulated, which is the process of placing data on the light. $f multiple optical channels are

desired, the light then passes through a multiplexer that combines it with wavelengths from other

lasers and places the resulting light onto a glass fiber. A bloc( diagram of this setup appears in

7ig ;>.


8/27


3asers generate a beam of a single wavelength. 0lectrical or optical energ! is pumped

into a gain medium, which is surrounded b! mirrors to form a Icavit!.J $nitial photons are either

electricall! generated within the cavit! or in@ected into the cavit! b! an optical pump. the!

trigger the release of other photons with the same optical properties ;wavelength, phase and

polari*ation


9/27


&!#he Raman 0ffect allows energ! from a pump beam to amplif! data at longer

wavelengths in glass fiber.

;b< #his can now done in silicon as well with small distance.

$f a data beam is applied at the appropriate wavelength, it will pic( up additional photons.

After traveling several (ilometers in the fiber, the beam ac uires enough energ! to cause a

significant amplification of the data signal ;7igure >.> A.>b


10/27


release of duplicate photons with the same optical properties ;wavelength, phase and

polari*ation


11/27


3.2.2. &wo photon a%sorption:

2suall!, silicon is transparent to infrared light, meaning atoms do not absorb photons as

the! pass through the silicon because the infrared light does not have enough energ! to excite an

electron. 'ccasionall!, however, two photons arrive at the atom at the same time in such a wa!that the combined energ! is enough to free an electron from an atom.

Fig 3.4!: PIN / t /$ int#insic n t /$! +io+$ /l&c$+ on $ith$# si+$ o- th$ light 0$&

When the pump pulse propagates through the waveguide, free carriers are generated due to the#PA effect. #he free-carriers effect not onl! causes excess absorptions, as mentioned before, it

also induces a change in the refractive index of the Silicon ;Kn


12/27


Where, 3M 3ength of waveguide

NM Wavelength of the light, OM #PA coefficient

PpM $ntensit! pulse of the probe, A MArea of waveguide.

Fig. 3.6!: En$#g (&n+ Di&g#&

2suall!, this is a ver! rare occurrence. However, the higher the pump power, the &ore li(el! it is

to happen. 0ventuall!, these free electrons recombine with the cr!stal 3attice and pose no further

problem. However, at high power densities, the rate at which the free electrons are created

exceeds the rate of recombination and the! build up in the waveguide. 2nfortunatel!, these free

electrons begin absorbing the light passing through the silicon waveguide and diminish the

power of these signals. #he end result is a loss significant enough to cancel out the benefit of

Raman amplification.

3.2.3. Breakthrough Laser:

#he solution is to change the design of the waveguide so that it contains a semiconductor

structure, technicall! called a P$ ;P-t!pe -$ntrinsic - -t!pe< device. When a voltage is applied

to this device, it acts li(e a vacuum and removes the electrons from the path of the light. Prior to

this brea(through, the two-photon absorption problem would draw awa! so man! photons as to



13/27


not allow net amplification. Hence, maintaining a continuous laser beam would be impossible.

$ntel4s brea(through is the use of the P$ to ma(e the amplification continuous.

7igure ;>.E< is a schematic of the P$ device. #he P$ is represented b! the p- and n-

doped regions as well as the intrinsic silicon in between. #his silicon device can direct the flowof current in much the same wa! as diodes and other semiconductor devices do toda! in common

electronics. Hence, the manufacture of this device relies on established manufacturing

technologies and it reinforces the basic goal of silicon photonics" inexpensive, high-performance

optical components.

Fig,#$ 3.7!: Th$ 0#$& th#o,gh silicon l&s$# ,s$+ & PIN +$ ic$ &n+ th$ R& &n E--$ct to & /li- light &s it 0o,nc$+

0$t'$$n t'o i##o#s co&t$+ on th$ '& $g,i+$ $n+s5 /#o+,cing & contin,o,s l&s$# 0$& &t & n$' '& $l$ngth.

#o create the brea(through laser, $ntel coated the ends of the P$ waveguide with mirrors to

form a laser cavit! ;7igure above/r. +abasaheb Ambed(ar #echnological 2niversit!, 3onere.


14/27


Fig,#$ 3.8! An $9& /l$ o- c#$&ting ,lti/l$ silicon l&s$# so,#c$s -#o on$ /, / 0$&

Fig 3. !: T'o Photon A0so#/tion in Silicon

3.2.4. 'a an Based !ilicon $hotonics

Raman scattering was proposed and demonstrated in 5665 as a mean to b!pass these limitations,

and to create optical amplifiers and lasers in silicon. #he approach was motivated b! the fact that

the stimulated Raman gain coefficient in silicon is 6 >- 6: times larger than that in fiber.

#he modal area in a silicon waveguide is roughl! 66 times smaller than in fiber,

resulting in a proportional increase in optical intensit!. #he combination ma(es it possible to

/epartment of 0lectronics 1 #elecommunication 0ngineering :/r. +abasaheb Ambed(ar #echnological 2niversit!, 3onere.


15/27


reali*e chip-scale Raman devices that normall! re uire (ilometers of fiber to operate. #he initial

demonstration of spontaneous Raman emission from silicon waveguides in 5665 was followed

b! the demonstration of stimulated Raman scattering and parametric Raman wavelength

conversion , both in 566>. 'ther merits of the Raman 0ffect include the fact that it occurs in pure

silicon and hence does not re uire rare earth dopants ;such as 0rbium


16/27


carrier depletion. 'ptimum electronic performance is crucial= the device is designed so that the

electrical and optical signals propagate together down the waveguide.

3.3.2. ,ow !ilicon odulator -orks:

#o understand how the modulator functions, we need to touch briefl! on the nature of

light. 3ight is a form of radiation that occurs at specific fre uencies, some of which are visible,

and some, li(e ultraviolet and infrared, that are invisible. When light is emitted it travels in a

pattern that loo(s ver! much li(e a sine wave. ;See the top row of 7igure .< #he total distance

reached b! the pea(s and troughs of this sine wave is (nown as amplitude. When the sine wave

is nearl! flat, the light is at its dimmest and has low amplitude. When the pea(s and troughs are

ver! high and deep, the light shines brightl! and has greater amplitude.

Fig: 3.;! & /li-ic&tion /h$no $non

When two wavelengths are combined, the resulting sine wave is the sum of the two

constituent sine waves. 7or example, if two sine waves are perfectl! in s!nc and added together

;left column of 7igure >.D. 6< the

resulting wave has no amplitude

/epartment of 0lectronics 1 #elecommunication 0ngineering E/r. +abasaheb Ambed(ar #echnological 2niversit!, 3onere.


17/27


3.3.3. ach 0ehnder inter*ero eter :

Fig 3.1


18/27


9ou start b! splitting the laser beam in two and then appl!ing an electric field to one

beam. $f the speed changes enough to dela! the beam b! half of one wavelength, that beam will

be out of phase with its mate. When the beams recombine, the! will interfere with each other and

cancel out.

$f, on the other hand, no voltage is applied, the beams remain in phase, and the! will add

constructivel! when recombined. 0ncoding the beam with s and 's, then, means ma(ing the

beams interfere ;6< or (eeping them in phase ;


19/27


&ach-Qehnder interferometer is modulated b! modulating the phase difference between the

interferometer s two arms. #his modulation can be ver! fast, because free carriers can be swept

out of the @unction.

#he modulator speed is thus limited b!, the parasitic effects such as R% time constantlimit. #he high-speed silicon modulator could find use in various future applications. 7or

example, a highl! integrated silicon photonic circuit ma! provide a cost effective solution for the

future optical interconnect within computers and other devices. With the demonstration of the :6

Gbps silicon modulator and the electricall! pumped h!brid silicon laser , it will become possible

to integrate multiple devices on a single chip that can transmit terabits of aggregate data per

second trul! enabling tera-scale computing .

3.4. Silicon (&s$+ Photo+$t$cto#:

Fig 3.13! Silicon (&s$+ Photo+$t$cto#

Silicon can also be used in photo detection-the process b! which incoming wavelengths

are converted into electrical signals representing bits. &odulation turns the light on and off to

encode the data. When the wavelength is off, a *ero-bit is encoded= when the wavelength is on, a

one-bit result. #he photo detector has the responsibilit! of converting those incoming bits bac(

into their electrical counterparts. &a(ing a photo detector in silicon, however, has a significant/epartment of 0lectronics 1 #elecommunication 0ngineering D/r. +abasaheb Ambed(ar #echnological 2niversit!, 3onere.
http://www.intel.com/research/platform/sp/hybridlaser.htmhttp://www.intel.com/research/platform/terascale/index.htmhttp://www.intel.com/research/platform/sp/hybridlaser.htmhttp://www.intel.com/research/platform/terascale/index.htm


20/27


challenge" At the infrared fre uencies used b! toda! s fiber-optic lasers, silicon is transparent. $t

cannot detect incoming light because the photons that ma(e up the wavelengths pass right

through it. $nterestingl!, if the laser wavelengths were in the visible spectrum where silicon is

not transparent, silicon would be ideall! suited for photo detection. $ntel has developed a means

of adding the element germanium to silicon to improve its light sensitivit! in the infrared

spectrum. #his approach leverages one of germanium s important properties" $t can extend the

spectrum of wavelengths at which silicon absorbs light. #his achievement enables $ntel to build

silicon detectors for optical communication.



21/27


CHAPTER 4

A T=PICAL ASSE"(L= OF SILICON PHOTONICS

7$G. below shows an assembling structure of silicon photonics in which modulators,

electronic chip, optical fiber, photo-detectors, a laser source mirrors etc.

Fig 4.1! Ass$ 0l St#,ct,#$



22/27


CHAPTER 6

"ICRO PHOTONICS > NANO PHOTONICS

&icro-photonics is a branch of technolog! that deals with directing light on a

microscopic scale. $t is used in networ(ing. &icro photonics emplo!s at least two different

materials with a large differential index of refraction to s uee*e the light down to a small si*e.

Generall! spea(ing virtuall! all of micro photonics relies on 7resnel reflection to guide the light.

$f the photons reside mainl! in the higher index material, the confinement is due to total internal

reflection . $f the confinement is due man! distributed 7resnel reflections , the device is termed a

photonic cr!stal . #here are man! different t!pes of geometries used in micro photonics including

optical waveguides, optical micro cavities , and Arra!ed Waveguide Gratings.

ano-photonics is the stud! of the behavior of light on the nanometer scale. #he abilit! to

fabricate devices in nanoscale that has been developed recentl! provided the catal!st for this area

of stud!. #he stud! of anophotonics involves two broad themes

. Stud! the novel properties of light at the nanometer scale.

5. 0nabling highl! power efficient devices for engineering applications. #he stud! has the

potential to revolutioni*e the telecommunications industr! b! providing low power, highspeed, and interference-free devices such as electro optic and all-optical switches on a

chip.

http://en.wikipedia.org/wiki/Technologyhttp://en.wikipedia.org/wiki/Index_of_refractionhttp://en.wikipedia.org/wiki/Fresnel_reflectionhttp://en.wikipedia.org/wiki/Photonshttp://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Fresnel_reflectionhttp://en.wikipedia.org/wiki/Photonic_crystalhttp://en.wikipedia.org/w/index.php?title=Optical_waveguides&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Optical_microcavities&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Arrayed_Waveguide_Gratings&action=edit&redlink=1http://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Nanometrehttp://en.wikipedia.org/wiki/Technologyhttp://en.wikipedia.org/wiki/Index_of_refractionhttp://en.wikipedia.org/wiki/Fresnel_reflectionhttp://en.wikipedia.org/wiki/Photonshttp://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Total_internal_reflectionhttp://en.wikipedia.org/wiki/Fresnel_reflectionhttp://en.wikipedia.org/wiki/Photonic_crystalhttp://en.wikipedia.org/w/index.php?title=Optical_waveguides&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Optical_microcavities&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Arrayed_Waveguide_Gratings&action=edit&redlink=1http://en.wikipedia.org/wiki/Lighthttp://en.wikipedia.org/wiki/Nanometre


23/27


CHAPTER 7

AD?ANTA)ES AND DISAD?ANTA)ES

A+ &nt&g$s:

. $t is inexpensive to use.

5. $mplementation is eas!.

>. Speed is so high ; #bit sec66th of usual speed of light. Smaller computers, less heat, elimination of motherboards ;b! toda! s standards, ;E -58.

C +. R. +ennett, I +ontrol o* unwanted light in !i wa#eguide J, / . 5uantu lectron. ,

vol. U0-5>, no. , pp. 5> 5D, Tan. DDE.

D 9urii A. lasov $+& #homas T. Watson Research %enter, 9or(town Heights, 9 68DC,

2SA , I !ilicon photonics *or next generation co puting s6ste s J p. 6F:> 5, 5668.

6 T. W. Pan, I!ilicon Nanophotonics 7 application in sensing J, 'pt. 0xpress E, 8F5

566C.

H. #a(esue,I Generation o* polari8ation entangled photon pairs using silicon wire

wa#eguide J, 'pt. 0xpress E, 8F5 ;566C, ;5 Soref. R,I&he past9 present9 and *uture o* silicon photonics J, $000 T. Sel. #op. Uuantum

0lectron, 566E, 5, ;E

Report Silicon Photonics (2)

Documents

Transcript of Report Silicon Photonics (2)