Intro to Optical Spec.pptx

7/23/2019 Intro to Optical Spec.pptx

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Introduction to opticalspectroscopy

Chemistry 243



Fundamentals of

electromagnetic radiation

(s-1)

34Planck's constant 6.626 10 J s

=frequency in Hz

E h

h

ν

ν

−

=

= = × ×

8 msee! of li"#t 3.00 10s

=$a%elen"t#

c

c

ν

λ

λ

=

= = ×

E swavenumber cm ∝∝== − υ

λ

11

ν h E = ν λ =

c



Electromagnetic spectrum

http://www.yorku.ca/eye/spectrum.gif

HighEnergy

LowEnergy



Terminology Spectroscopy is the study of the interaction of

light and matter NMR or !Ray spectroscopy" spectroscopist

Spectrometry is the esta#lishment of thepattern of interaction $as a function of energy% of

light with particular forms of matter Mass spectrometry $M&%" spectrometrist

Spectrophotometry is the 'uantitati(e study of

the interaction of light with matter )*!*isi#le spectrophotometry (I’e neer heard anyone called a spectrophotometrist)



!hat chemical and"or material

properties can we measure using

spectral methods# +road and powerful applications ,lemental composition $often metals" C-N% dentity of a pure su#stance $what is it0% Components of a mi1ture $purity0% mount of a su#stance in a mi1ture $how much0% +ulk/maor component minor component

trace component ultra!trace component &urface composition Material property $stress/strain polymer cross!

linking change of state temperature% Reaction rate mechanism products



!hat properties of incident or

generated light can we measure#

#sorption 5luorescence $fast% 6 7hosphorescence $slow% 8hermal ,mission

Chemiluminescence &cattering Refraction or Refracti(e nde1 7olari9ation 7hase nterference/iffraction Coherence Chemistry conse'uent to the a#o(e



!hat atomic"molecular properties

affect or are affected $y light#

Rotation $typically refers to a molecule%

*i#ration $typically refers to a molecule%

,lectronic ,1citation $atomic or molecular% oni9ation $loss of electron to yield a cation%

Com#inations of the a#o(e:

Rotation!(i#ration $infrared/Raman% Rotational (i#rational electron e1citation $)*!*is%

oni9ation with )* a#sor#ance $strong e1citation%



The properties you want to study

help to select a suita$le waelength

-igh ,nergy

;ow ,nergy



!hy waenum$er#

8he energy difference #etween two wa(enum#ers isthe same regardless of spectral region or λ

<a(elength is not proportional to energy" it has a

reciprocal relation to energy so:

8he energy difference #etween two wa(elengths $in nmor angstroms% (aries as a function of spectral region.

11 −=⇒= cmunit

λ ν

&' ν

ν

λ

ν

∆=∆

==

=

hc E

hc

hc

h E

ν λ =c

E ∝λ

1



%electing the right optical

method



Emission

&lasma'

flame' or

chemical

Focus

%orting of

Energy'

%pace' and

Time

etection

Computer control enhances

and optimi9es the info

e1tracted from each

instrument component.

,1citation &ource

Chemiluminescence is emission

caused #y a chemical reaction.

5luorescence is emission

caused #y e1citation



$sorption

Light

%ource Focus %pecimen FocusEnergy'

%pace' and

Time %orting

etection

Transmissionand"or

*eflection can

also occur

Nearly linear light path geometry

for multi!wa(elength

simultaneous light detection

Rela1ation is non!radiati(e"sample warms up a #it (ia (i#ration and rotation

) $ s o r $ a n c e

!aelength (+)



Fluorescence (fast) , &hosphorescence

(slow)

Light%ource

(Laser)

Focus

Focus etection

%pecimen

Energy'

%pace' and

Time %orting

ay include

energy sorting

Typical geometry ./0'

$ut angle aria$le

E m i s s i o n & o w e r

*adiatie



*aman %cattering

Light

%ource

Laser

Focus

Focus etection

%pecimen

Energy'

%pace' and

Time %orting

Typical geometry ./0'

$ut angle aria$le

%ame geometrical layout as fluorescence and phosphorescence'

2ut what happens is not the same as a$sorption or emission



*aman %cattering

Elastic scattering3 Ee4 5 Eout

Inelastic scattering3 Ein 6 Eout and Ein 7 EoutEe4citation

Ee4 8E-E

irtual stateirtual state



,mission

5lame

plasma

chemistry

#sor#ance$)*/*is or R%;amps ;,s

5luorescence/

7hosphoresence

;amps ;,s

laserslasers

Raman scattering

ifferent classes of optical

spectroscopy



9lasses of light sources



Light sources3

9ommon e4amples

+lack#ody radiation ;ight emitting diode $;,s% rc lamp/hollow cathode lamp

;asers &olid!state =as/e1cimer ye laser

8hermal e1citation Com#inations $laser to (apori9e

sample leading to thermal emission%



9ontinuum spectra and

$lac:$ody radiation

solid is heated to incandescence t emits thermal #lack#ody radiation in a continuum

of wa(elengths

%:oog' Fig; <-==

High E 5 Low + 5 High T <ien>s

;aw

b is <ein>s displacement constant

6

6

6

2.8(8 10 ) nm

2.8(8 10 ) nm(.82 m

2(* )

2.8(8 10 ) nm(.3* m

310 )

peak

roomtemp

human

T λ

λ µ

λ µ

× ×=

× ×= =

× ×= =

T bblackbody

peak =λ



9ontinuum spectra and

$lac:$ody radiation

http://en.wikipedia.org/wiki/mage:+lack#ody!lg.png

http://en.wikipedia.org/wiki/+lack?#ody

8 @ A2BB C8 @ A4D3 E



9ontinuum sources

Common sources euterium lamp $common )ltra(iolet source% r e or -g lamps $)*!(is%

>ot always continuous" spectral structure possi#le

http://wwwA.union.edu/newman/lasers/;ightF2B7roduction/;amp&pectra.gif

http://creati(elightingllc.info/4GBp1!euterium?lamp?A.png



Light emitting diodes (LEs)

5irst practical (isi#le region ;,

in(ented #y Nick -olonyak in

AHI2 $=," ))C since AHI3%

J5ather of the light!emitting!diodeK

http://en.wikipedia.org/wiki/Nick?-olonyakhttp://upload.wikimedia.org/wikipedia/commons/D/Dc/7nLunction!;,!,.7N=

http://www.pti!n.com/images/8imeMaster;,/;,!spectra?remade.gif

n ;, is a semiconductor

which emits electroluminescence



Light emitting diodes (LEs)

Cheap low energy long!lasting small fast

Commonly used in display screens stoplights

circuit #oards as state indicators

;ots of colors nfrared ;,s used in remote controls

http://en.wikipedia.org/wiki/5ile:*erschiedene?;,s.pg



Line (emission) sources

Continuous wa(e -ollow cathode discharge lamp

Microwa(e discharge

5lames and argon plasmas

7ulsed 7ulsed hollow cathode

&park discharge ll these are non!laser

line source is a light source

that emits at a narrow waelengthcalled an emission ?line@



Lasers

Light mplification #y

%timulated Emission

of *adiation

• ntense light source• Narrow #andwidth $small range B.BA nm%• Coherent light $in phase%



Lasers

Light mplification #y

%timulated Emission

of *adiation

• 7umping

• &pontaneous ,mission• &timulated ,mission• 7opulation n(ersion



Laser design

Lasing medium is often3• a crystal' li:e ru$y• a dye solution• a gas or plasma

photon

cascadeA

&koog 5ig. D!4



&umping

=eneration of e1cited electronic states #y thermal

optical or chemical means.

&koog 5ig. D!G



%pontaneous emission or

rela4ation

Random in time No directionality

Monochromatic $same % #ut incoherent $not in phase%

&olid (s. dashed line O 2 different photons

&koog 5ig. D!G



%timulated emission

8he e1cited state is struck #y photons of precisely

the same energy causing immediate rela1ation

,mission is 9BHE*E>T

,mitted photons tra(el in same direction ,mitted photons are precisely in phase

&koog 5ig. D!G



&opulation inersion

<hen the population

of e1cited state

species is greater

than ground statean incoming photon

will lead to more

stimulated emission

instead ofa#sorption. Inerted population

>ormal population

distri$ution

&e4cited 7 &ground

&e4cited 6 &ground

&koog 5ig. D!I



C- and D-state lasers

7opulation in(ersion easier in 4!state system

&koog 5ig. D!D

Things stac:

up here;

&opulation

inersion easily

achieed;

&opulation

relatiely low

down here



Laser design

Lasing medium is often3• a crystal' li:e ru$y• a dye solution• a gas or plasma

photon

cascadeA

&koog 5ig. D!4



9ontinuous wae

laser sources Nd3P:Qttrium aluminum garnet $Q=: Q3 lGA2%

&olid state 1/<D nm C= nm 3GG nm 2II nm

8he =8, &yl(ania Model IBG uses a Nd!Q= laser rod set in a dou#leellipticalJ reflector is pumped #y two GBB!< incandescent lamps and is

limited to a low order mode #y an aperture in the laser ca(ity.



9ontinuous wae

laser sources -elium!Neon $-eNe%

=as #ut emission comes from generated plasma $(ery e1citedstate atoms%

<C=; nm IA2 nm IB3 nm and G43.G nm" A.AG 6 3.3H Sm ,mission lines all the way out to ABB Sm

HH.HF

reflecti(e

HHF

reflecti(e



9ontinuous wae

laser sources rP

=as laser #ut emission comes from ions )ses lots of electrical power to generate ions

3GA.A nm 3I3.T nm 4G4.I nm 4GD.H nm 4IG.T nm 4DI.G nmD;/ nm 4HI.G nm GBA.D nm 1D; nm G2T.D nm ABH2.3 n

Coherent nno(a HB

)p to G < of outputU

VABB1 my laser pointer



Bther continuous wae

laser sources

Cu (apor G2B nm

-eCd

DD/ nm 32G nm ye lasers



&ulsed lasers sources Nd:Q=

&olid state

ften nanosecond pulses

1/<D nm' C= nm 3GG nm

8i:sapphire &olid stateWoften pumped #y Nd:Q=

8una#le output aroudn TBB!A2BB nm

7roduces femtosecond pulses

Nitrogen =as

CCG nm

,1cimer lasers $gas mi1tures" e1cited state is sta#le%

8una#le dye lasers $ is selecti(e within limits%



Laser diodes

)sed in C and *players $not (ery strong%

<a(elengths now a(aila#lefrom R to near )* regions

+and gap

energy ,g

&koog 5igs. D!T 6 D!H.

*esonant

9aity emits

t .G nm



Tip going forward

Eeep your (aria#les straight v for (elocity or ν for fre'uency

Microsoft e'uation editor gi(es:

will use m for integer te1t#ook uses n ,asy to get mi1ed up with refracti(e inde1 n

m+s& %ee

1+s&nu

=

=

v

ν

& ti f l t ti



&roperties of electromagnetic

radiation

8ransmission

Refraction

Reflection &cattering

ptical Components

nterference

iffraction

& ti f l t ti



&roperties of electromagnetic

radiation

y = magnitude of the electric field at time t

A = ymax – also called the amplitude of y

ν = frequency in s -1 (cycles per second)

φ = phase angle (an offset relative to a reference sine wave)

ω = angular velocity in radians/sec (a handy definition)

Recall: π radians = 1! degrees

( )

( )φ πν

πν ω

φ ω

+=

=

+=

t A y

t A y

2sin

2

sin

φ

Interference magnitudes add or su$tract



2

82

+ is in phase with





2

82

+ is ATB degrees $X radians% shifted from





2

82

+ is HB degrees $X / 2 radians% shifted from


Interference $etween waes of



Interference $etween waes of

different freuency

<a(e A P 2

&koog 5ig. I!G

21 ν ν ν −=∆

T i i th h



Transmission through

materials Compared to (acuum the (elocity of light is reduced

when propagating through materials that ha(e

polari9a#le electrons. <a(elength also decreases

ll electrons are polari9a#le to some e1tent

%:oog' Fig <-=; cacuum 5 =;..G.= 4 1/ m Y s-1

i

i

cn

v=

me!iumc

constant

=

=

=

λν

ν h E



Inde4 of *efraction

*efractie inde4 is measure of how much light is slowed3

*efractie inde4 is waelength- and temperature-dependent for many materials3

A.4IZuart9

A.4H8oluene

A.43-e1adecane

A.GT=lass$light flint%

A.33<ater

A.BB*acuum $air%

n @ 589.3 nmaterial<a(elength!dependence of nSiO2

http://www.rp!photonics.com/refracti(e?inde1.html

len"t#"i%en $a%eaat%elocity

1&'len"t#"i%en $a%eaatin!e,refracti%e

=

≥==

i

i

vacuumi

v

v

cn



*efraction

&nell>s law:

il immersion lenses

for high magnificationmicroscopy

Jelocities' not freuencies

Medium A

Medium 2

Here' n= 7 n1

%:oog' Fig; <-1/

2

1

1

2

2

1

sin

sin

v

v

n

n==θ

θ



For your information

+ook ,rror on page A4A e'uation I!A2:

8his is correct: &nell>s ;aw of Refraction

2me!iumin%elocity

1me!iumin%elocity

sin

sin

2

1

1

2

2

1 === v

v

n

n

θ

θ



*eflection

mount of loss at a reflection increases with refracti(einde1 mismatch. 5or right angle light entrance into a medium:

Reflecti(e loss is angle!dependent

5resnel e'uations $which we will skip% Most important case is: total internal reflection

( )

( )

2

2 1

20 2 1

r n n I

I n n

−=

+ 1intensityinci!ent

intensityreflecte!≤=



Total internal reflection

;ight incident upon a material

of lesser refracti(e inde1 is#ent away from the normal sothat the e1it angle is greaterthan then incident angle. t the critical incident angle

the e1it angle is HB ! #eam

does not e1it ngles larger than the critical

incident angle lead to totalinternal refection $8R%

MediumA

Medium2

nentry

ne4it

Modified from &koog

nentry 7 ne4it

K= 7 K1

!hen this is true' K1 5 critical entry angle for TI*

exit critical entry

exit critical entry

exit entry

nn

nn

nn

nn

=

=

=

=

θ

θ

θ θ

θ θ

sin

&(0sin'sin

sinsin

sinsin

21

2211

1θ

2θ




8R fluorescence

microscopy:

http3""hyperphysics;phy-astr;gsu;edu"H$ase"phyopt"totint;htmlhttp3""www;olympusmicro;com"primer"techniues"fluorescence"tirf"tirfintro;html

!hen this is true'

K1 5 critical entry angle for TI*;

If K1 [ Kcritical result is TI*;

Eanescent wae samples a ery

narrow slice of the sample ery near

to the dielectric interface

Typically =// nm

exit critical entry nn =θ sin

f




8R fluorescence

microscopy:

!hen this is true'

K1 5 critical entry angle for TI*;

If K1 [ Kcritical result is TI*;

http3""hyperphysics;phy-astr;gsu;edu"H$ase"phyopt"totint;htmlhttp3""www;olympusmicro;com"primer"techniues"fluorescence"tirf"tirfintro;html

Mood for studying adhered cellsN low $ac:ground

exit critical entry nn =θ sin



Fi$er optics

,1truded strands of glassor plastic that guide light(ia total internal reflection. Core has higher refracti(e

inde1 than cladding. 5le1i#le Material choice allows

transmission in )* (isi#leor R

&koog 5ig D!3H.

Follows all the rules of

%nell’s Law



%cattering

Raman scattering nelastic scattering

offset from λ #y fre'uency of molecular (i#rations

Rayleigh scattering Molecules or aggregates smaller than λ ntensity V A/λ4

Mie scattering 7articles large $or compara#le% to λ )sed for particle si9ing



Essential optical elements

;enses

Mirrors

7risms

5ilters

=ratings



2asic optical components

Mirrors Reflection

Conca(e mirror is

con(erging

7risms Refraction

&nell>s ;aw1 1 2 2sin sinn nθ θ =

Filt



Filters

#sorption filters Cheap (isi#le region"

colored glass

Cutoff filters O long!pass

short!pass

nterference filters

%:oog' Fig; G-1=

θ is usually 9ero

so cos θ \ A.

lso m is usually A

d \ thickness of dielectric layer

n \ refracti(e inde1 of dielectric medium

m = inte"er

λ ́ = $a%elen"t# in t#e !ielectric material

2

cos

2

cos

inter"er

air

air

d m

n

dn

m

m

λ θ

λ λ

λ θ

′ =

′=

=

=

I t f filt



Interference filters

lmost

monochromatic

%:oog' Fig; G-1C

2andwidth of a filter is

width at half-height(a:a full-width O half-ma4)

iffraction of coherent radiation3




Interference at wor:

Conse'uence of

interference

%:oog' Figs; <-G' <-

constructie

destructie

constructie

constructie

destructie

d 5 distance from slit 2 to 9

istance 4 to y is one +

(m is the order of interference)

m is3• / for E• 1 for

m use! #ere- te,t uses n

inte"er

sin

==

m

d m θ λ




act o o co e e t ad at o

Interference at wor:

Conse'uence of

interference

(m is the order of interference)

m use! #ere- te,t uses n

You can now determine the

wavelength of light

based on things that

are easy to measure!

%:oog' Fig; <-

inte"er

sin

==

m

d m θ λ

OD DE BC

d m

=

= θ λ sin



onochromators

)sed to spatially separate different

wa(elengths of light: prisms gratings

C9erny!8urner grating monochromator +unsen prism monochromator

%:oog' Fig; G-1



Mratings and monochromators

*eflection 8 diffraction3 echellette-type grating

%:oog' Fig; G-=1

The condition for

constructie interference;The m 5 1 line is most intense;

The surface contains ?grooes@ or ?$laPes@;

8ake a look at

,1ample D!A

7age AT4.

( )

( )

sinsin

sin sin

m CB BD

CB d i BD d r

m d i r

λ

λ

= +

=

=

= +



onochromators

)sed to spatially separate different

wa(elengths of light: prisms gratings

C9erny!8urner grating monochromator

%:oog' Fig; G-1

Qseful metrics for



Qseful metrics for

monochromators

ispersion $page ATG%" high dispersion is good ntegration of at constant i gi(es the

angular dispersion:

Linear dispersion is the (ariation of along the

focal plane position y:

*eciprocal linear dispersion !A:

r 5 angle of reflection

d 5 distance $etween $laPes

ore useful' results in

-1 in nm per mm

or similar

measure of

the a$ility to

separate waelengths

( )sin sinm d i r λ = +

cos

dr m

d d r λ =

focal len"t#

dy dr D

d d

λ λ

×= =

=

1 cos for small r

d d r d D

dy m m

λ − ×= = ≈

Qseful metrics for



Qseful metrics for

monochromatorsRcontinued

Resol(ing power $R" unitless% ;imit of monochromator>s a#ility to distinguish

#etween adacent wa(elengths.

;ight gathering power $f!num#er 5" unitless% Collection efficiencyWimpro(e for ma1imi9ing &/N

,fficiency scales as the in(erse s'uare of 5

focal len"t# of collimatin" mirror or lens

!iameter of collimatin" otic

! d

d

=

=

=

!illuminate lazes"ratin"of /umer

'unitless&

=

=

∆

=

"

m" #λ

λ

2

∝

d E

9omplications with



9omplications with

monochromators

(erlap of orders m \ A λ\ IBB nm and m \ 2 λ \ 3BB nm spatially o(erlap

Qou can get λ>s mi1ed up if light source contains manywa(elengths

dditional wa(elength selection often needed 5ilter prism detector selection de(ice digital

analysis after data collection #ackgroundsu#traction Might need to use a different light source if your

wa(elength of interest is not JcleanK

%lit width and spectral



%lit width and spectral

resolution of a spectrometer

8radeoff e1ists #etween sensiti(ity and resolution -igh intensity \ high sensiti(ity $low noise%

8wo #asic concepts: f you make the entrance slit width too #ig you let in a lot of

light $that>s good O high intensity% #ut it can #e multi!wa(elength" a large section of light dispersed in λ is let in =ood light intensity poor spectral resolution

f you make the entrance slit width too small you let in less

light $less intensity% #ut its λ range is smaller 7oor light intensity good spectral resolution

,ntrance slit $creates image% and e1it slit $output filter% )sually the same width

ptimal slit width #ased upon grating dispersion

%lit width



%lit width

&koog 5ig. D!24

For Sust passing =

%lit width



&koog 5ig. D!2G

&total

If spectral $andwidth

is "=' good

spectral resolution

2oth entranceand e4it slits

narrowed

from top to

$ottom

%lit width

w is slit width

%lit width



&koog 5ig. D!2I

%lit width

<atch the effect of adusting the slit width and theresultant spectral #andwidth on the following data sets of

#en9ene (apor.

w is slit

width



Bptical &hotodetectors

. 7hotomultiplier tu#e $7M8%

+. Cd& photoconducti(ity

C. =as photo(oltaic cell

. Cd&e photoconducti(ity cell

,. &e/&e photo(oltaic cell

5. &i photodiode

=. 7#& photoconduciti(ity

-. 8hermocouple

. =olay cell

These generally ma:e current

or oltage when light hits them;

ore sensitie

Less sensitie

Ideal photodetector



Ideal photodetector

(photon transducer)

-igh sensiti(ity

-igh &/N

5ast response time

&ignal directly

proportional to ] of

photons detected

êro dark current 8he #lank is 9ero

r e'ui(alently

counte! P#otons∝ "

$

k% $ =

Ideal photodetector



-igh sensiti(ity

-igh &/N

5ast response time

&ignal directly


photons detected

êro dark current 8he #lank is 9ero

Ideal photodetector

(photon transducer)

-igh sensiti(ity

-igh &/N

5ast response time

&ignal directly


photons

êro dark current

R e a l i t y

I n t r u

d e s -ere>s what really happens:

&ignal is

5unction of

Constant dark

current term

$non!9ero%

$ k% =

( ) dark $ k% k λ = +

Three main



Three main

photodetector types

7hoton transducers $directly JcountK photons% 7hotomultiplier tu#es $7M8s%

Charge transfer de(ices

Charge inection de(ices $C% Charge coupled de(ices $CC%

8hermal transducers 7hotons strike the transducer

8emp increases 8emp increase increases conducti(ity

Current or (oltage are measured



Jacuum phototu$e

Cathode is coated with

photo!emissi(e material

,mitted electrons are

collected anode.

] of electrons is directlyproportional to ] of photons.

Current is easy to amplify.

)sually ha(e small dark

current. perate at V HB* #ias

Not so porta#le

&koog 5ig. D!2H.



&hotomultiplier tu$e (&T)

] of electrons is amplified#y photoelectric effectupon accelerationtowards dynodes

,ach dynode #iased V HB*more positi(e than pre(iousdynode $or cathode%

*oltage drop accelerateselectrons to dynode

cascade mplification: ABI!ABD

electrons per incidentphoton" electron cascade

http://www.nt.ntnu.no/users/flo#an/ELF2BF2B3BGG/7M8.pg



&hotomultiplier tu$e (&T)

d(antages: *ery sensiti(e in )*!*is region

single photon sensiti(ity Cooled 7M8 has (ery low

#ackground $kdark approaches 9ero%

;inear response 5ast response

isad(antages ,asily damaged #y intense $am#ient%

light Noise is power dependent &ingle channel: can>t use for imaging

&hotooltaic cell



&hotooltaic cell ;ight strikes a

semiconductor $&e% andgenerates electrons andholes

Magnitude of current isproportional to ] of

photons Re'uires no e1ternal

power supplyU isad(antages: hard to

amplify signal and fatigue$wears out% )seful for porta#le

analyses field workoutdoor setting

&koog 5ig. D!2T

&hotodiodes



&hotodiodes(%ilicon 1./-11// nm' InMas .// 1<// nm)

Re(erse!#iased p!n unction Conductance goes to near

9ero

7hotons create electron hole

pairs that migrate to oppositecontacts and generate

current

+attery powered 7orta#le applications

re not as prone to some

electronic noise sources IB -9 line noise

&koog 5ig. D!32



ultichannel transducers

llow simultaneous interrogation of multiple

wa(elengths

maging

7hotodiode arrays $A! array%

Charge!transfer de(ices $2! array% Charge!inection de(ices

Charge!coupled de(ice $CC% CM&



&hotodiode arrays

,ach diode has definedspatial address

d(antages Multichannel $used for

imaging% More ro#ust than 7M8

isad(antages Not as sensiti(e as 7M8 &lower response time

Common in cheaper )*!*isinstruments ften perfectly ade'uate

&koog 5ig. D!33



9harge transfer deices

Con(erts light into charge Negati(e!#iasing leads to

increased capture of holes

under pi1el electrodes 7otential well

7hoton eects electron and

the de(ice collects and stores

charges ABG!ABI charges per pi1el

Configured as C or CC

&koog 5ig. D!3G

&chematic is for C

9harge transfer deices



g

(continued)

Charge!inection de(ice $C%!measuresaccumulated (oltage change $nondestructi(eread" persistent after read% Measurements can #e made while integrating

Charge!coupled de(ice $CC%!mo(esaccumulated charges to amplifier and readout$destructi(e read" gone after read% *ery high sensiti(ity" AB4!ABG pi1els

-igh resolution spectral imaging Complementary metal o1ide semiconductor

$CM&% <e#cam technology: C-,7U

E sensiti(ity large pi1el density

99 (charge coupled deice)



99 (charge coupled deice)

7i1els read one at a time #y se'uential

transfer of accumulated charge

5rom: JCC (s. CM&: 5acts and 5ictionK #y a(e ;itwiller in 7hotonics &pectra Lanuary 2BBA



9B% detectors

igital camera and we#cam technology

,ach pi1el can #e read indi(idually

5rom: JCC (s. CM&: 5acts and 5ictionK #y a(e ;itwiller in 7hotonics &pectra Lanuary 2BBAmage from <ikipedia

99 9B%



99 9B%

,ssentially serial

,ach pi1el read one at atime #y common e1ternalcircuitry *oltage con(ersion and

#uffering

utputs an analog signal -istorically ga(e higher!

resolution images Relati(ely e1pensi(e

-igh power consumption )p to ABB1 more than

CM&

,ssentially parallel

,ach pi1el has its own redout circuitry Jon!chipK llows amplification and

noise correction More suscepti#le to noise

utputs a digital signal Reduced area for light

a#sorption Relati(ely ine1pensi(e

-ighly commerciali9ed fa#

Runs on less power Re'uires less Joff!chipK

circuitry

2oth approaches e4ist today



&hotoconductiity transducers

&emiconductors whose resistance decreases

when they a#sor# light

#sorption promotes electron to conduction

#and. )seful in near R$λ \ B.DG to 3 µm%

Cooling allows e1tension to longer

wa(elengths #y reducing thermal noise



Thermal transducers

&olution for R region $low energy photons%

8hermocouples ;ight a#sor#ed heats the unction $two pieces of dissimilar

metal% which leads to a change in (oltage relati(e to a

reference thermocouple.

+olometer $thermistor% Material changes resistance as a function of temp

7yroelectric de(ices 8emperature!dependent capacitor

Change in temperature leads to change in circuit current

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Intro to Optical Spec.pptx

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