bo loc quang

Nghin cu v ch to b lc quang (bng rng v bng hp) da trn mng a lp silic xp

Nguyn Thy Vn

Trng i hc Cng ngh

Lun vn Thc s ngnh: K thut in t; M s: 60 52 70 Ngi hng dn: TS. Bi Huy

Nm bo v: 2011

Abstract: Tng quan v tinh th quang t v tinh th quang t mt chiu da trn silic xp. Tin hnh m phng cc c tnh quang hc ca b lc quang. Trnh by cc kt qu thc nghim ch to b lc quang hc giao thoa da trn quang t mt chiu v m phng

Keywords: in t - Vin thng; K thut in t; B lc quang; Mng a lp silic xp

Content

M U

Tinh th quang t l mt loi vt liu mi c nhiu nt tng ng tinh th bn dn -

mt vt liu lm nn cuc cch mng mi v s pht trin ca cng nghip vi in t (IC).

Chnh nh s pht trin ca ngnh cng nghip ny chng ta ch to c nhng my tnh

c nhn gn, nh vi tc cao, nhng h thng thng tin vin thng siu tc bng thng

rng. Tinh th quang t l mt cu trc khng gian tun hon ca cc vt liu c hng s in

mi khc nhau. S bin i tun hon ca hng s in mi lm xut hin vng cm quang

(photonic bandgap - PBG) trong cu trc vng (c hiu l mi lin h gia tn s v s

sng) ca tinh th quang t. PBG trong tinh th quang t c vai tr ging nh vng cm v

nng lng trong tinh th in t.

Chng ta c th s dng tinh th quang t iu khin, giam gi v kim sot nh

sng trong khng gian ba chiu. Tinh th quang t c th cm hon ton cc sng in t c

bc sng trong PBG lan truyn qua n m khng ph thuc vo s phn cc ca nh sng.

Tinh th quang t c th to ra s dn sng t b mt mt nng lng hng dng nh sng

truyn theo mt hng c th (thm ch vi nhng ch r cong n 900) Trn thc t, tinh

th quang t c xem nh linh kin then cht cho cc mch tch hp quang trong thng tin

quang v cc h thng my tnh lng t trong tng lai. Vi kh nng kim sot s lan truyn

v bc x t pht nh sng, tinh th quang t c nh hng to ln n s pht trin cng ngh

2

ch to cc b lc quang, cc chuyn mch quang tc cao, cc hc quang, cc it quang,

cc laser ngng thp, cc ng dn sng vi cc nhnh r nh sng t ngt ng dng trong

thng tin quang v cc sensor ha, sinh hc

Trong cc loi tinh th quang t, tinh th quang t mt chiu l loi tinh th n

gin nht. Tuy nhin tinh th mt chiu li c nhng u im ring nh d dng ch to hn,

c th s dng nghin cu mt s kha cnh ca tinh th quang t nhiu chiu hn v c th

dn n nhng ng dng v cc linh kin m chng khng yu cu phi cm hon ton (v

mi hng) s lan truyn qua hay bc x nh sng. Tinh th quang t mt chiu vi chit sut

ng nht trong mi lp c bit n di tn gi l tm phn x Bragg phn b hay thng

dng hn l b lc quang hc giao thoa. Loi b lc ny l mt trong cc linh kin quang hc

kh thng dng, trc y thng c ch to bng phng php phn x hay bay hi nhit

mt cch ln lt cc oxt to ra mng mng a lp c chit sut thay i tun hon. Ngy

nay, da trn cng ngh in ha phin silic chng ta c th ch to c mng silic xp a

lp c tnh nng nh mt b lc quang hc giao thoa. Cc b lc quang bng rng hot ng

da trn nguyn l phn x Bragg ch to t mng silic xp a lp c th t c rng

ph t vi chc n vi trm nano mt. Trn c s b lc quang bng rng ny, chng ta c th

ch to c cc b lc bng hp c rng ph ch vi nano mt vi suy hao thp di

dng cc bung vi cng hng. u im ca cc b lc ch to bng phng php ny l tch

hp thun li vi cng ngh vi in t to ra mch tch hp quang vi vng ph hot ng

c tri rng t nhn thy, qua hng ngoi n tn vng siu vi ba.

Vi nhng l do trn v ng thi da vo trang thit b hin c ca phng th nghim

ti chn ti cho lun vn thc s l:

Nghin cu v ch to b lc quang (bng rng v bng hp) trn c s mng a lp

silic xp.

Ngoi phn m u v kt lun, lun vn gm c ba chng vi ni dung nh sau:

Chng 1: Tng quan v tinh th quang t mt chiu

Chng 2: M phng cc c tnh quang hc ca b lc quang

Chng 3: Kt qu thc nghim v tho lun

CHNG 1

TNG QUAN V TINH TH QUANG T MT CHIU

1.1 Tinh th quang t

1.1.1 Khi nim tinh th quang t:

3

Tinh th quang t l mt cu trc tun hon trong khng gian ca cc vt liu vi hng

s in mi khc nhau c sp xp xen k nhau, c chit sut thay i theo chu k trn mt

thang chiu di c th so snh c vi bc sng nh sng ang c nghin cu.

1.1.2 Cc c tnh v thng s quan trng ca tinh th quang t

Tinh th quang t c c trng bi mt s thng s c bn sau: S chiu, s i

xng, hng s mng (a), h s lp y (f), chit sut hiu dng (neff), s tng phn chit sut

()

1.1.3 Cc ng dng ca tinh th quang t

S dng nh cc chuyn mch quang hc, b nh quang hc, pin quang-in-ha

Tinh th quang t mt chiu( 1D) c s dng trong vic kim sot v iu chnh nh sng

mc chnh xc c bc sng, nh vic to ra tinh th quang t 1D c s dng nh nhng

b lc quang hc, ng dn sng, cm bin sinh hc

1.2 Tinh th quang t mt chiu da trn silic xp

1.2.1 Tinh th quang t mt chiu c thit k nh mt b lc giao thoa

a. B lc quang giao thoa bng rng Gng phn x Bragg (Distributed

Bragg Reflectors)

B lc bng rng hay gng phn x Bragg l h gm nhiu lp in mi hot ng

da trn hin tng nhiu x Bragg ca mt chm nh sng sau khi phn x ti mt phn cch

gia cc lp in mi. M hnh n gin ca hin tng nhiu x c trnh by trong hnh

1.6 [9],[15], trong mng mng bao gm nhiu cp lp ging ht nhau, mi cp lp gm hai

lp c chit sut n1 v n2 khc nhau tng ng vi dy d1, d2.

Hnh 1.6: (a) Tia phn x v tia truyn qua trong trng hp mng n lp v (b)

trong trng hp mng a lp

B lc di rng c s dng nhiu nht l b lc (Gng phn x Bragg - DBR) phn

t bc sng, l loi b lc c di quang hc ca cc lp l nH.hH=nLhL=/4 v chu k

ca cu trc l =hH+hL

4

Hnh 1.8 Hnh minh ha ca cc hiu ng phn x ca mt b lc bng rng. a) nh

sng phn x ti mi mt phn cch gia cc lp c chit sut khc nhau, b) ph phn x ca

mt b lc bng rng da trn tinh th quang t mt chiu [9],[19].

b. B lc bng hp Bung vi cng hng (Microcavities)

Hnh 1.9. S ct ngang ca mt bung vi cng hng. Chit sut ca lp m l

ns v b dy ca lp ny l ds. Lp m c a vo gia hai DBR i xng vi chit sut

ca cc lp l nH, nL v b dy dH, dL

1.2.2 C s cho qu trnh hnh thnh b lc giao thoa trn c s mng silic

xp a lp

1.2.2.1 S hnh thnh silic xp

Silic xp ch yu c to ra t s n mn in ho cc phin Silic trong cc dung dch

axit HF [2],[13]. Hnh 1.10 l s ch to silic xp: anot l phin silic c b mt c tip

xc vi dung dch HF, catt c lm bng platin.

Hnh 1.10. S nguyn l ch to silic xp

1.2.2.2 Kch thc v hnh thi l xp

5

Hnh 1.12: Mt ct ngang hnh nh TEM cho thy s khc nhau c bn trong hnh thi

gia cc loi khc nhau ca mu. (a) silic pha tap loi p, (b) silic pha tp loi n, (c) silic pha

tap loi p+, (d) silic pha tp loi n+.

1.2.2.3 Cc thng s anot ha

Cc nghin cu s hnh thnh silic xp bng n mn in ha [1],[10] u cho thy cc

tham s nh hng ti qu trnh ny l:

- S pha tp ca phin silic gm: loi tp v nng tp;

- Mt dng;

- Nng HF: nng cng cao, kch thc l v xp cng nh. Nng

HF quyt nh JPS, l gii hn trn ca gi tr mt dng.

- Cc dung mi dng pha long HF: v silic xp l loi vt liu k nc nn

vic s dng ethanol lm cht pha long HF s m bo tnh ng nht v kh nng thm t

b mt tt hn so vi nc kh ion ha.

- Thi gian n mn: thi gian n mn di dn n cc lp dy hn, nu khng

c thi gian di s xy ra tnh d hng i vi chiu su trong lp do hot ng ha hc ca

cht in phn.

- S chiu sng trong sut qu trnh n mn: p dng cho silic loi n [10]

1.2.3 c im ca silic xp.

1.2.3.1 xp (P)

Phng php n gin nht xc nh xp theo trng lng c th hin trong

cng thc 1.4:

1 2

1 3

%m m

Pm m

(1.4)

6

Hnh 1.13 : Mi quan h gia xp v mt dng ca tm silic loi p+ (~0,01 cm)

vi dung dch HF 15% trong ethanol. Tng mt dng dn n xp cao hn. xp nm

trong khong gia 45% v 85% l ph hp i vi mt dng thit lp t 5 mA/cm2 n 100

mA/cm2[23].

1.2.3.2 Chit sut hiu dng

1.2.3.3

Hnh 1.14: Gin minh ha khi nim chit sut hiu dng ca silic xp [22]

Hnh 1.15: Mi quan h gia xp v chit sut ca silic xp. S khc bit gia l

thuyt Bruggeman, Looyenga v Maxwell-Garnett l do nhng gi thit to ra cc hnh thi

ca vt liu hn hp gia silic v khng kh [23].

1.2.3.4 Tc n mn

1.2.3.5

7

Hnh 1.16: Gin mi lin h gia tc n mn vi mt dng in ca loi silic

P+ (0,01 cm ) vi dung dch axit HF 15% trong ethanol[23].

KT LUN CHNG 1

1. Tinh th quang t c cu trc khng gian tun hon v chit sut, c trng c bn

nht ca n l tn ti vng cm quang, tc dng quan trng nht l kim sot s lan truyn v

bc x nh sng.

2. Tinh th quang t mt chiu n gin nht l b lc giao thoa bng rng (DBR), c

cu trc gm cc lp in mi bin i tun hon v chit sut sao cho qung ng quang

hc mi lp tha mn iu kin Bragg. Da trn cu trc ca b lc bng rng, chng ta c th

pht trin ch to b lc bng hp. B lc bng hp c cu trc bung vi cng hng bao

gm hai b lc bng rng ging ht nhau t i xng vi nhau bi mt lp m c di

quang hc bng /2 hoc .

3. iu kin to ra silic xp bng in ho phin silic: dung dch in ho cha HF,

ch phn cc a-nt, mt dng thp hn ngng nh bng in cc v c s tham gia

ca l trng trong phn ng ho tan Si.

4. C s cho vic ch to mng silic xp a lp: (i) qu trnh hnh thnh cc nano tinh

th Si trong silic xp mang tnh cht t gii hn do mt khi nano Si c to ra hay mt lp

xp c to ra th chng s khng b nh hng ca cc qu trnh in ho tip theo; (ii)

xp ca lp xp ch ph thuc vo mt dng khi cc iu kin in ho cn li c duy tr

khng i; (iii) chit sut ca lp xp ph thuc n nht vo xp ca n; (iv) tc n

mn ph thuc n nht vo thi gian n mn khi cc iu kin in ho khc c duy tr

khng i. Cc iu kin ny cho php thay th vic kim sot chit sut theo chiu su ca

mng ngha l to ra mt mng a lp bng vic kim sot mt dng theo thi gian n mn.

5. L thuyt mi trng hiu dng a ra tiu chun cho vt liu xp gm hai pha

c th c xem nh l mi trng hiu dng n nht vi mt hng s cch in c trng

m n l trung bnh theo t trng ca hng s cch in ca hai vt liu hp phn khi khong

khng gian trng trong vt liu nn nh hn nhiu so vi bc sng ca nh sng ti.

8

CHNG 2

M PHNG C TNH QUANG HC CA B LC QUANG

2.1. C s ton hc phn tch v m phng mng a lp

Trc khi ch to b lc quang hc giao thoa, chng ti xy dng chng trnh m

phng c th thit k v d on c cc tnh cht quang hc ca b lc mt cch chnh

xc hn. Mi b lc quang hc giao thoa da trn mng a lp silic xp c c trng bi

cc thng s c bn nh: s lp N, chit sut n v dy quang hc d ca lp. C rt nhiu

phng php s phn tch b lc quang hc giao thoa (hay h thng mng a lp) nh:

Phng php ma trn truyn (Transfer Matrix Method - TMM), phng php sng phng

(Plane Wave Method - PWM), v phng php min thi gian khc bit hu hn (Finite

Difference Time Domain - FDTD). Da trn nhng u nhc im ca tng phng php

chng ti chn phng php Ma trn truyn m phng c trng ph phn x cho cc b

lc c nghin cu trong Lun vn.

2.1.1 Phng php ma trn truyn (Transfer Matrix Method - TMM)

Phng php ma trn truyn (TMM) l mt thut ton rt hu ch cho vic tnh ton

ph phn x v truyn qua ca cc cu trc a lp.

Phng php ma trn truyn c th x l cc cu trc c ch s tng phn cao gia hai

vt liu hn hp. iu ny khin cho TMM tr thnh phng php ph hp cho m phng cc

cu trc mng a lp, l cc cu trc c s tng phn cao gia cc lp.

2.1.2 Chng trnh m phng:

Trong lun vn ny, chng ti s dng phng php ma trn truyn m phng ph

phn x ca b lc quang giao thoa.

Hnh 2.1. S cu trc b lc quang giao thoa 1 chiu bng rng

9

Hnh 2.2 S cu trc ca b lc quang hc giao thoa 1 chiu bng hp

2.2. Kt qu m phng b lc quang hc giao thoa da trn tinh th

quang t 1 chiu:

Mc ch nh gi kt qu thc nghim vi kt qu tnh ton ca l thuyt, chng

ti m phng chi tit khi thay i tng thng s ca b lc. u tin trong phn ny, ti a

ra cc kt qu m phng v b lc quang bng rng, sau l cc kt qu v b lc quang

bng hp.

2.2.1 Kt qu m phng v b lc quang giao thoa 1 chiu bng

rng[3],[8],[21]:

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000

0.2

0.4

0.6

0.8

1

Pho phan xa cua bo loc quang bang rong 1D

Buoc song (nm)

Do

ph

an

xa

(R

)

Hnh 2.3 Ph phn x ca b lc quang bng rng 1D vi chu k l 12,

nH=2,5,nL=1,55,dH=155nm v dL=258,3nm.

Nghin cu cc thng s ca b lc quang:

a) T l chit sut nH/nL:

1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000

0.2

0.4

0.6

0.8

1

1.2Pho phan xa cua bo loc quang bang rong 1D

Buoc song (nm)

Do p

han

xa (

R)

(a)

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000

0.2

0.4

0.6

0.8

1


Buoc song (nm)

Do

ph

an

xa

(R

)

(b)

10

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000

0.2

0.4

0.6

0.8

1


Buoc song (nm)

Do

ph

an

xa

(R

)

(c)

Hnh 2.4. Ph phn x ca b lc quang bng rng vi s chu k N=12. dy ca

mi lp c tnh ton sao cho bc sng trung tm 1550nm. T l chit sut nH/nL ln lt

l:(a) 2/1,55; (b) 2,3/1,55; v (c) 2,5/1,55

1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 22000

0.2

0.4

0.6

0.8

1


Buoc song (nm)

Do p

han

xa (

R)

(1) 2.0/1.55

(2) 2.3/1.55

(3) 2.5/1.55

(1)(2)(3)

Hnh 2.5 Ph phn x ca b lc quang bng rng 1D khi t l chit sut n1/n2 ca cp

lp trong mt chu k thay i

b) S chu k ca b lc:

1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 30000

0.2

0.4

0.6

0.8

1


Buoc song (nm)

Do p

han

xa (

R)

(1) N=4

(2) N=6

(3) N=8

(4) N=25

(1) (2) (3) (4)

Hnh 2.6. Ph phn x ca b lc quang bng rng 1D vi n1=2,3; n2=1,55 v s

chu k ln lt l 4, 6, 8 v 25 chu k

Bng 2.1 Bng gi tr th hin s ph thuc ca phn x vo s chu k

S chu

k N

H s

phn x

S chu

k N

H s

phn x 1 0.5172 9 0.9932

2 0.6904 10 0.9961

3 0.8113 11 0.9978

4 0.8886 12 0.9988

5 0.9354 13 0.9993

6 0.9692 14 0.9996

7 0.9789 15 0.9998

11

8 0.9880 16 0.9999

Hnh 2.7: S ph thuc ca h s phn x vo s chu k

Nhn xt: khi s chu k N tng ln, h s phn x tng dn ti gi tr 1

Nghin cu s nh hng ca s chu k ln bn rng ph

Bng 2.2 Bng gi tr th hin s ph thuc ca bn rng ph

vo s chu k

S chu

k N

bn

rng ph

S chu

k N

bn

rng ph 2 698 9 363

3 551 10 353

4 481 11 345

5 440 12 338

6 411 13 332

7 392 14 327

8 375

Hnh 2.8. S ph thuc ca bn rng ph vo s chu k

Nhn xt: khi s chu k N tng ln th bn rng ph c xu hng gim xung v

dn ti gi tr xc nh.

c) Nghin cu s nh hng ca bc sng nh sng trung tm ln bn

rng ph

12

1000 1500 2000 2500 3000 35000

0.2

0.4

0.6

0.8

1

1.2

Pho phan xa cua bo loc quang bang rong 1D

Buoc song (nm)

Do

ph

an

xa

(R

)

(1) 1000nm

(2) 1550nm

(3) 2500nm

(1) (3)(2)

Hnh 3.12. S ph thuc ca bn rng ph vo bc sng nh sng trung tm. (1)

0 = 1000 nm, (2) 0 =1550 nm, (3) 0 = 2500 nm.

Bng 2.3: Bng gi tr th hin s ph thuc ca bn rng ph vo bc sng nh

sng trung tm trong vng 1000nm n 2800 nm:

Bc

sng nh sng

trung tm (

nm)

bn

rng ph

Bc

sng nh sng

trung tm (nm)

bn

rng ph 1000 289 2000 442

1200 265 2200 487

1400 310 2500 530

1550 353 2600 573

1800 398 2800 618

Hnh 3.13: th th hin s ph thuc ca bn rng ph vo bc sng sng

trung tm.

Nhn xt: bn rng ph ph thuc gn nh tuyn tnh vo bc sng ca nh sng

ti, khi bc sng nh sng ti tng, th bn rng ph cng tng

2.2.2 Kt qu m phng b lc quang giao thoa 1 chiu bng hp da

trn tinh th quang t 1 chiu [21]:

500 600 700 800 900 1000 11000

0.2

0.4

0.6

0.8

1

1.2Pho phan xa cua bo loc quang giao thoa bang hep 1D

Buoc song (nm)

Do

ph

an

xa

(R

)

13

Hnh 2.7. Ph phn x m phng ca mt b lc quang giao thoa bng hp 1D vi

bc sng cng hng 0 =650nm. T l ca nH/nL l 2,5/1,55 v dss= 0 /2ns.

Nghin cu cc thng s ca b lc quang giao thoa bng hp 1D

a) dy ca lp khng gian (dss):

500 600 700 800 900 1000 11000

0.2

0.4

0.6

0.8

1


Buoc song (nm)

Do p

han

xa (

R)

(a)

500 600 700 800 900 1000 11000

0.2

0.4

0.6

0.8

1


Buoc song (nm)

Do

ph

an

xa

(R

)

(b)

Hnh 2.8 Ph phn x ca mt vi hc cng hng bao gm 2 DBR vi dy quang

hc l /4 v mt lp khng gian dy l a), b)/2.

b) Chit sut phn x ca lp gia

Hnh 2.9 Ph phn x ca b lc quang giao thoa da trn tinh

th quang t 1 chiu bao gm 2 DBR vi nL=1,55 v nH =2,5. dy

ca lp khng gian l /2 v chit sut phn x ca n ln lt l a)1,4,

b)1,55, c) 1,8, d) 2,5.

d) S chu k ca DBR

400 500 600 700 800 900 1000 1100 12000

0.2

0.4

0.6

0.8

1

Pho phan xa cua bo loc quang hoc bang hep

Buoc song (nm)

Do

ph

an

xa

(R

)

N=2

N=4

N=6

N=8

(4)(3)(2)(1)

Hnh 2.10 Ph phn x ca b lc quang hc giao thoa bng hp da trn tinh th

quang t mt chiu ti bc sng trung tm 650nm trong cc DBR c s chu k khc nhau.

14

2 3 4 5 6 7 80

2

4

6

8

10

12

14

16

18

20

FH

WM

lin

e w

idth

of

cavit

y (

nm

)

The number of periods N

Hnh 2.11 S ph thuc ca bn rng

ph vo chu k ca b lc quang hc giao thoa bng hp ti bc sng 650nm.

KT LUN CHNG 2

1. Trong chng ny, chng ti chng minh c rng phng php ma trn

truyn l phng php rt hu ch v n gin cho vic m phng mng a lp. Da vo

phng php ny, chng ti m phng c cc c tnh quang hc ca b lc quang bng

cch thay i cc thng s u vo nh chit sut v dy ca cc lp, s chu k, gc ti v

khong bc sng. Cc c trng ca ph phn x ca b lc quang hc giao thoa bng rng

v bng hp c nghin cu trong vng bc sng t 600nm n 3000 nm.

2. Trong lun vn ny, mc d vic m phng trng tm cho cc lp silic xp

nhng vi bt k vt liu no chng ta cng c th m phng c bi v chit sut c th

c thay i ty vo mi vt liu khc nhau.

3. Cc kt qu nghin cu ph phn x ca b lc quang hc bng rng bng

chng trnh m phng nh sau:

- Ph phn x ph thuc ln vo t s nH/nL (t s gia chit sut lp cao v chit

sut lp thp), rng ph tng cng vi tng phn chit sut gia hai lp lin k

- Khi s chu k N tng, ph phn x ca cc b lc hp li v phn x tng

dn ti 1

- Khi s chu k N tng ln, h s phn x tng dn ti gi tr 1

- Khi s chu k N tng ln th bn rng ph c xu hng gim xung

- bn rng ph ph thuc tuyn tnh vo bc sng nh sng ti, khi bc

sng nh sng ti tng, th bn rng ph cng tng.

4. Sau khi m phng cc c tnh quang hc ca b lc quang hc giao thoa bng

hp ta thu c cc kt qu nh sau:

- Khi thay i dy quang hc ca lp khng gian th ph phn x trong c hai

trng hp v /2 l tng t nhau. nh truyn qua c t ti bc sng trung tm

650nm trong c hai trng hp v phn x trong c hai trng hp gn nh bng 0 ti bc

15

sng ny. Tuy nhin, vng cm ca b lc vi lp khng gian l /2 l rng hn vng cm ca

b lc c dy l v cc cc tr hai bn gn vi vng cm hn.

- Chit sut phn x ca lp khng gian gn nh khng c nh hng nhiu ti

vng cm hoc nh truyn qua. S khc nhau gia cc ph phn x khi ta quan st thy c

l cc side-lobes.

- rng ca nh truyn qua ph thuc vo s chu k ca cc DBR ca hc

cng hng. Khi N tng, nh truyn qua tr nn hp hn, phn x ca vng cm tng ln

v hnh dng ca ph sc nt hn.

CHNG 3

CC KT QU THC NGHIM V THO LUN

3.1 Nguyn l, qui trnh ch to mng a lp bng phng php n mn

in ha

3.1.1 Nguyn l ch to

3.1.2 Ch to b lc quang hc da trn mng a lp silic xp

Bc 1: Chun b mu, dng c v ha cht

Hnh 3.1: H l c dng tip xc cho phin silic bc bay nhm

Bc 2: Ch to PC 1D bng phng php n mn in ha

Hnh 3.2: H thng n mn in ha

16

Hnh 3.3: S h in ha AUTOLAB. PGSTAT 30 dng ch to PC 1D

3.2 Thit k ch to b lc quang hc giao thoa da trn tinh th quang t 1

chiu

3.2.1 Thit k b lc quang hc giao thoa bng rng

Hnh 3.4: Lc ch to mng a lp

3.2.2 Thit k b lc quang giao thoa bng hp

Hnh 3.5. (a) S minh ha cu trc ca mt b lc quang hc bng hp th hin bi

lp khuyt tt c di quang hc /2 xen gia hai DBR gm cc lp c chit sut cao v

thp c di quang hc /4 xen k ln nhau. (b) Ph phn x tng ng ca b lc cho thy

mt bc sng cng hng hp gia nh phn x cc i.

17

Hnh 3.6. S minh ha qu trnh n mn to ra silic xp. Qu trnh ha tan ca

silic c u tin xy ra nh cc l xp ni mi trng l m c nht v cc l trng (h+)

v cc ion F- phn ng vi nhau. Hn na cc vng pha trn sau khi b n mn khng b nh

hng bi cc ht ti in

Hnh 3.7. S ca quy trnh to ra cc lp silic xp. Thi gian v ln ca mt

dng in quyt nh dy v xp ca lp silic xp sau khi in ha. Khi p dng mt

dng theo thi gian ( th bn tri), cc lp silic xp c hnh thnh tng ng (hnh v bn

phi). Mt thi gian ngn c thit lp (vi mt dng bng 0) nng HF cn bng

trong sut cc l xp v ngn nga s hnh thnh ca gradient xp khng mong mun

Bng 3.1. Cc iu kin n mn ch to b lc quang hc bng hp da trn tinh

th quang t 1D

M t Mt dng

(mA/cm2)

Thi gian

(s)

18

Gng

trn

(N,5 chu

k)

15 6,35

50 3,63

Lp

khuyt tt

50 7,26

Gng

di (N+1 chu

k)

15 6,35

50 3,63

3.3 Cc kt qu ch to b lc quang hc giao thoa da trn tinh th quang

t 1D

3.3.1 Cc kt qu ch to b lc quang hc giao thoa bng rng da trn tinh

th quang t 1D

a. Cu trc b lc quang bng hp

(a)

(b)

Hnh 3.8: nh FE SEM ca 2 lp lin k c t s mt dng (a) 15/50mA/cm2 and

(b) 25/50mA/cm2

b. Cu trc ca cc PC mt chiu c s chu k khc nhau

Hnh 3.9: nh FESEM c cng h s khuch i ca mt ct ngang ca

mng a lp vi s chu k N l 6, 12 v 18, tong ng vi cc hnh (a), (b) v (c).

c. Cc kt qu nghin cu ph phn x ca PC mt chiu da trn mng

silic xp a lp

19

iu khin bc sng trung tm ca ph phn x trong di hng

ngoi

1000 1500 2000 2500 3000

0

10

20

30

40

50

60

70

80

90

100D

o p

han x

a (

%)

Buoc song (nm)

Hnh 3.10: Ph phn x ca PC mt chiu ch to bng phng php n mn in ha vi

nng HF l 16%, tng phn mt dng 50mAcm-2/15 mAcm-2

Hnh 3.11: Ph phn x ca cc mng a lp c thit k vi bc sng trung tm

thay i trong di hng ngoi

nh hng ca s tng phn chit sut ln rng ca cc i ph

phn x

Hnh 3.12: Ph phn x ca cc PC M4 v M5 c ch to vi t s mt

dng J1/J2 tng ng l 50mAcm-2

/30mAcm-2

v 50mAcm-2

/15mAcm-2

C

n

g

p

h

n x

(%)

Bc sng (nm)

20

Nh vy bc u c th khng nh rng c th iu chnh tng phn v

mt dng in ca hai lp lin k trong qu trnh ch to b lc iu chnh rng ca

cc i trong ph phn x.

nh hng ca s chu k N ln ph phn x ca b lc da trn mng

silic xp a lp

Hnh 3.13: Ph phn x ca cc b lc a, b v c c ch to vi s chu k

N tng ng l 6, 18 v 12.

1000 1500 2000 25000

0.2

0.4

0.6

0.8

1

1.2

So sanh pho phan xa mo phong va thuc nghiem

Buoc song (nm)

Do p

han

xa (

R)

(1) mo phong

(2) thuc nghiem

Hnh 3.14. So snh ph phn x m phng (1) v thc nghim (2) ca cng mt mu

b lc quang hc bng rng da trn PC 1D vi bc sng thit k =1460nm

d. Cc kt qu ban u v ch to b lc quang hc bng rng hot ng

trong vng nhn thy da trn mng silic xp a lp ch to bng phng php n

mn in ha

Hnh 3.15. nh chp cc mu PC 1D hot ng trong vng nhn thy cc bc

sng khc nhau (tng ng vi iu kin ch to khc nhau)

C

ng

ph

n x

(%)

21

a b

400 450 500 550 600 650 700 750 800

10

20

30

40

50

60

70

80

90

Cu

on

g d

o p

ha

n x

a (

%)

Buoc sng (nm)

562.5nm

603nm

647.7nm

689nm

(1)(2)

(3)

(4)

Hnh 3.16. Ph phn x ca cc mu b lc quang hc hot ng trong vng nhn

thy

3.3.2 Cc kt qu ch to b lc quang hc giao thoa bng hp da trn tinh

th quang t 1 chiu

Hnh 3.17. nh FE-SEM ca mt ct ngang mt b lc quang hc giao thoa bng hp

da trn tinh th quang t 1D vi di quang hc ca lp m (lp khuyt tt) l /2 vi

bc sng cng hng 650nm v tng phn chit sut l 15/50mAcm-2 (a), v nh FE-

SEM cho thy kch thc ca cc l xp vo khong vi chc nanomet trong lp m ca b

lc (b)

Hnh 3.18. nh FE-SEM ca vi hc cng hng 1D vi bc sng cng hng

650nm, t s mt dng l 15/50mAcm-2, nng HF l 16% cho thy b dy ca lp m

l khong 174nm

22

400 500 600 700 8000

10

20

30

40

50

60

70

80

Do

ph

an

xa

(%

)

Buoc song (nm)

Hnh 3.19. Ph phn x ca vi hc cng hng 1D vi 20 lp silic xp. Bc sng

trung tm ca vi hc cng hng 643,27nm v rng tng ng ca di truyn qua l

20nm.

500 600 700 80020

30

40

50

60

70

80

90

Do

ph

an

xa

(%

)

buoc song (nm)

a

b

Hnh 3.20. Ph phn x ca hai vi hc cng hng c cc iu kin ch to ging

nhau nhng s chu k ca cc DBR trn/di l khc nhau ln lt l

6,5/7 (a) v 8,5/9 (b).

400 500 600 700 80010

20

30

40

50

60

70

80

Do

ph

an

xa

(%

)

Buoc song (nm)

Cavity 11 Jan 146

540nm

576nm

Hnh 3.21. Ph phn x ca vi hc cng hng 1D gm hai di truyn qua trong vng

cc i ph phn x ti 540nm v 576nm

23

450 500 550 600 650 700 750 800 850 9000

0.2

0.4

0.6

0.8

1

Pho phan xa cua bo loc quang hoc bang hep

thuc nghiem va mo phong

Buoc song (nm)

Do

ph

an

xa

(R

)

(1) thuc nghiem

(2) mo phong

(1) thuc nghiem

(2) mo phong

Hnh 3.22. So snh ph phn x thc nghim (1) v m phng (2) ca cng mt mu

b lc quang hc bng hp da trn PC 1D vi bc sng thit k =644nm

KT LUN CHNG 3

1. Chng ti xy dng c quy trnh v ch to thnh cng mng silic a lp

ng u trn din tch c 1 cm2 bng phng php n mn in ho phin silic loi p+, c

nh hng tinh th (100) trong dung dch HF l 16% vi vi cu trc bao gm cc l xp ng

u nm trong khong 5 n 50 nm tng ng vi s thay i ca mt dng trong khong

t 15mA/cm2 n 150 mA/cm2.

2. S ph thuc ca tc n mn vo mt dng n mn v s ph thuc ca

chit sut vo mt dng n mn c nghin cu v cho cc kt qu tng t vi cc

cng b ca cc tc gi nc ngoi.

3. Chng ti ch to thnh cng cc b lc quang hc bng rng trn c s

mng silic xp a lp hot ng trong vng ph t hng ngoi n vng nhn thy vi h s

phn x ln ti 80%.

4. Ph phn x ca cc b lc ch to c s ph hp nht nh vi cc kt qu

nhn c t tnh ton m phng v nh hng ca tng phn chit sut ca cc lp lin

k v s chu k N ca b lc. S sai lch v ph gia thc nghim v m phng ch xy ra vi

cc b lc c s chu k qu nh hoc qu ln v c gii thch thng qua s thay i cu

trc ca cc lp xp trn b mt v di y ca b lc.

5. Chng ti cng ch to thnh cng b lc bng hp hot ng trong vng

nh sng nhn thy da trn PC 1D bng phng php n mn in ho phin silic. Cc b lc

quang hc ny c phn x cao, trong khong t 50% n hn 80%.

6. Cc kt qu thc nghim cng cho thy khi s chu k ca b lc quang bng

hp tng ln th cng ca nh ph phn x tng ln v rng na cc i ca di truyn

qua gim. Cc kt lun ny rt ra ph hp vi cc tnh ton bng m phng.

24

KT LUN CA LUN VN

Lun vn t c mc tiu ra vi nhng kt qu chnh nh sau:

1. Lun vn trnh by mt cch h thng khi nim, nhng c trng c bn cng

nh nhng ng dng quan trng ca tinh th quang t ni chung v c bit l ca tinh th

quang t mt chiu da trn mng silic xp a lp.

2. Lun vn xy dng c mt quy trnh n mn in ho n nh, to c mng

xp a lp ng u trn din tch mu l ng trn c ng knh 10mm.

3. Lun vn chng minh c rng phng php ma trn truyn l phng php rt

hu ch v n gin cho vic m phng mng a lp. Da vo phng php ny, chng ti

m phng c cc c tnh quang hc ca b lc quang bng cch thay i cc thng s u

vo nh chit sut v dy ca cc lp, s chu k, gc ti v khong bc sng. Cc c

trng ca ph phn x ca b lc quang hc giao thoa bng rng v bng hp c nghin cu

trong vng bc sng t 600nm n 3000 nm

4. tm c quy trnh n nh, ph hp ch to cc b lc quang hc bng rng

c cht lng tt hot ng trong mt vng di ph rng t vng nhn thy n vng hng

ngoi. Cc b lc ny c cu trc trt t dn n hnh thnh vng cm quang theo phng

truyn, phn x cao. Vng cm quang ca cc b lc quang hc ph hp vi cc tnh ton

t m phng. Ngoi ra, chng ti cng nghin cu nh hng ca cc yu t nh tng

phn chit sut, s chu k n ph phn x ca b lc quang hc. Kt qu cho thy:

- Khi tng tng phn chit sut gia cc lp th cc i ph phn x

s c m rng.

- Khi s chu k tng ln th cng phn x tng dn n 1 v bn

rng ca cc i trung tm s gim.

Cc kt qu ny cng cho thy s ph hp gia m phng v thc nghim.

5. ch to thnh cng cc b lc quang bng hp trn c s PC 1D. Cc b lc ny

c vng bc sng hot ng tri di trong vng nhn thy v c phn x t 50% n 80%.

Ph phn x t m phng v thc nghim c s ph hp vi nhau chng t cht lng ca b

lc ch to c. Cc kt qu thc nghim cng cho thy khi s chu k ca b lc tng ln th

cng ca nh ph phn x tng ln v rng na cc i ca di truyn qua gim. Cc

kt lun ny rt ra ph hp vi cc tnh ton bng m phng.

References

25

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