multichannel phenomenon of symmetrical structure optical filter guoxun tian april 23, 2007 atms790...
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Multichannel Phenomenon of SymmMultichannel Phenomenon of Symm
etrical Structure Optical Filteretrical Structure Optical Filter
Guoxun TianGuoxun TianApril 23, 2007April 23, 2007
ATMS790 Seminar (Dr. Pat ArnotATMS790 Seminar (Dr. Pat Arnott)t)
Outline
1. Mutiple reflection in Multilayer film
2. Introduction of Fabry-Perot filter
3. Multichannel Phenomenon in double-symmetrical structure
4. Design of double-linear filter
5. Two-chamber integrated multichannel narrowband filter
6. Review
High index
Low index
High index
Low index
High indexSubstrate
Incident lightReflected light =combination of
many beamsAir
Transmitted light
Multilayer
1.1. Mutiple reflection in Multilayer film
A multilayerA multilayer
A Fabry-Perot filter showing multiple reflections A Fabry-Perot filter showing multiple reflections in the spacer layerin the spacer layer
Spacer layer
Incident light
Reflected light =combination of many beamsAir
Transmitted light
High-reflectance
Multilayer
High-reflectance
Multilayer
2. Fabry-Perot filter
Mirror MirrorCavity
2. Fabry-Perot filter
C
Structure of Fabry-PerotStructure of Fabry-Perot Filter Filter
77 )()( LHHHL C
This is a symmetrical structure and the position of channel was calculated by equivalent surface method
Structure of this Fabry-Perot filter: (HL)7HC(LH)7, where the number “7” is the periodic number and c is the periodic thickness of the cavity layer. 1H=1L=nHdH=nLdL=λ0/4, where dH and dL are the physical thickness of high and low refractive index material respectively, λ0 =600 nm. Vertical incidence, nH=2.3 and nL =1.44. Refractive index of substrate is n=1.52. Absorbance of the material of material is neglected to simplify the theoretical calculation.
Simulated conditionsSimulated conditions2. Fabry-Perot filter
)2(21
sin)1(
41
1
)1(21
2
221
212
21
21
δϕϕ −+−
+−
=
RRRRRR
TTT
κπδϕϕ 2221 =−+ )3,2,1( LLL±=κ
221
21max
)1( RR
TTT
−=
EEquivalent surface methodquivalent surface method
2. Fabry-Perot filter
EEquivalent surface methodquivalent surface method
Maintains two mirrors invariably It means that 1 and
2 are constants
C is the thickness of Layer C δ ( δ =2πnC/ )
Changes the thickness of layer C to satisfy the following formula
1+ 2 - 2πnC/=2kπ (k=±1 , 2 ,3 )
= 2πnC/ [2k π+( 1+ 2)]
Calculation of channel’s position
2. Fabry-Perot filter
Multichannel Fabry-PerotMultichannel Fabry-Perot Filter Filter
Two-channel filter 492nm/598nm Three-channel filter487nm/550nm/632nm
2. Fabry-Perot filter
Channel can be moved continuously by Channel can be moved continuously by changing layer Cchanging layer C
The position of channels are correlated. It is difficult to design a useful two-channel filter by this structure because we can not ensure every channel on it’s position.
500 550 600 650 700 750
5010050
10050
10050
10050
100C=5.6H
C=5.2H
C=4.8H
C=4.4H
C=4H
Wavelength(nm)
Transmittance(%)
Deficiency in this structure
2. Fabry-Perot filter
Fabry-PerotFabry-Perot structurestructure Fabry-Perot structureFabry-Perot structure
Coupling layerCoupling layer
C Cd
7777 )()()()( LHHHLLLHHHL CdC
Double-symmetrical structure based on Double-symmetrical structure based on Fabry Perot structureFabry Perot structure
3. Multichannel Phenomenon in double-symmetrical structure
Movement of Channel position while d changes and C is fixed
Adjustment of Channel position
3. Multichannel Phenomenon in double-symmetrical structure
7777 )()()()( LHHHLLLHHHL CdC
Calculated spectrum of double-symmetrical structure
3. Multichannel Phenomenon in double-symmetrical structure
Adjustment of Channel position Calculated spectrum of double-symmetrical structure
Movement of Channel position while C changes and d is fixed
7777 )()()()( LHHHLLLHHHL CdC
Calculated spectrum and experiment spectrum
(HL)3HLCH(HL)3LD(HL)3HLCH(HL)3
3. Multichannel Phenomenon in double-symmetrical structure
(a) d changes and C is fixed (b) C changes and d is fixed
Here H=L=nHdH=nLdL=λ0/4, λ0=749nm, nH=2.2 , nL=1.44
3. Multichannel Phenomenon in double-symmetrical structure
Calculated spectrum and experiment spectrum (1H1L)31H1LC1H(1H1L)31LD(1H1L)31H1LC1H(1H1L)3
(a) d changes and C is fixed (b) C changes and d is fixed
Film structure of double-linear filter
7777 )()()()( LHHHLLLHHHL CdC
4. Design of double-linear filter
Relationship between incident point and spectrumIncident point move along X axis
4. Design of double-linear filter
7777 )()()()( LHHHLLLHHHL CdC
4. Design of double-linear filter
Relationship between incident point and spectrumIncident point move along Y axis
7777 )()()()( LHHHLLLHHHL CdC
C C
Film structure of two-chamber filter
5. Two-chamber integrated multichannel narrowband filter
The original structure of the filter designed to be (HL)4H4.64LH(LH)4L(HL)4H4.64LH(LH)4 with design wavelength =777.4nm0
Flow sheet of the preparation of two-chamber integrated narrowband filter
5. Two-chamber integrated multichannel narrowband filter
(a) Depositing the first resonant cavity, (b) etching the first resonant cavity, (c) second depositing, (d) depositing the second resonant cavity, (e) etching the second resonant cavity, (f) deposition the residual film.
(HL)4H4.64LH(LH)4L(HL)4H4.64LH(LH)4
5. Two-chamber integrated multichannel narrowband filter
Calculated spectrum of two-chamber integrated narrowband filter
780 800 820 840 860 880 900 920-0.10.00.10.20.30.40.50.60.70.80.91.0
%Transmittance
Wavelength / nm
Experiment spectrum of two-chamber integrated narrowband filter
5. Two-chamber integrated multichannel narrowband filter
(HL)4H4.64LH(LH)4L(HL)4H4.64LH(LH)4
Instrument and experiment condition
5. Two-chamber integrated multichannel narrowband filter
Thickness of two spacer layer of which equivalently decreases by the optical thickness of 0.02L through the etching technique.
Coating machine: ZZSX-800 (Beijing Beiyi Innovation Vacuum Technology Co., Ltd, Beijing, China) optical multilayer coating machine, which uses the electron-beam vapor-deposition method assisted by ionic bombardment to fabricate the multilayer. Etching machine: the LKJ-1C (Beijing Institute of Radio Measurement, Beijing, China) ion-beam etching machine, which uses the dry etching method. The entrance angle of the ion beam is normal. The depth of the 32 parallel etched notches is gradually increased, and their width and length are 0.375 and 12 mm, respectively. Material: TiO2 and SiO2.
5. Two-chamber integrated multichannel narrowband filter
Instrument and experiment condition
Thank you_ _