Multichannel Phenomenon of
Symmetrical Structure Optical Filter
Guoxun Tian
April 23, 2007
ATMS790 Seminar (Dr. Pat Arnott)
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
1. Mutiple reflection in Multilayer film
A multilayer
Incident light
Reflected light=combination of
many beams
Air
Low index
High index
Low index
High index
Substrate
Transmitted light
Multilayer
High index
2. Fabry-Perot filter
A Fabry-Perot filter showing multiple reflections
in the spacer layer
Incident
light
Reflected light=combination of
many beams
Air
High-reflectance
Multilayer
Spacer layer
High-reflectance
Multilayer
Transmitted light
2. Fabry-Perot filter
Structure of Fabry-Perot Filter
C
Mirror
Cavity
Mirror
( HL )7 H C ( LH )7
This is a symmetrical structure and the position of
channel was calculated by equivalent surface method
2. Fabry-Perot filter
Simulated conditions
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.
2. Fabry-Perot filter
Equivalent surface method
T1T2
T
(1  R1 R2 ) 2
1
4 R1 R2
1
1
sin (1   2  2 )
2
2
(1  R1 R2 )
2
1  2  2  2 (  1,2,3)
Tmax 
T1T2
(1  R1 R2 ) 2
2. Fabry-Perot filter
Equivalent surface method
 Calculation of channel’s position
Maintains two mirrors invariably
It means that 1 and
 2 are constants
C is the thickness of Layer C
（  =2nC/）
Changes the thickness of layer C to satisfy the following formula
 1+  2－2nC/=2k (k=±1，2，3）
= 2nC/ [2k +( 1+  2)]
2. Fabry-Perot filter
Multichannel Fabry-Perot Filter
Two-channel filter 492nm/598nm
Three-channel filter487nm/550nm/632nm
2. Fabry-Perot filter
C=5.6H
C=5.2H
C=4.8H
C=4.4H
100
50
100
50
100
50
100
50
100
50
C=4H
Transmittance(%)
Channel can be moved continuously by
changing layer C
500 550 600 650 700 750
Wavelength(nm)
Deficiency in this structure
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.
3. Multichannel Phenomenon in double-symmetrical structure
 Double-symmetrical structure based on
Fabry Perot structure
Coupling layer
C
Fabry-Perot structure
d
C
Fabry-Perot structure
( HL )7 H C ( LH )7 Ld ( HL )7 H C ( LH )7
3. Multichannel Phenomenon in double-symmetrical structure
 Adjustment of Channel position
 Calculated spectrum of double-symmetrical structure
( HL )7 H C ( LH )7 Ld ( HL )7 H C ( LH )7
Movement of Channel position while d changes and C is fixed
3. Multichannel Phenomenon in double-symmetrical structure
 Adjustment of Channel position
 Calculated spectrum of double-symmetrical structure
( HL )7 H C ( LH )7 Ld ( HL )7 H C ( LH )7
Movement of Channel position while C changes and d is fixed
3. Multichannel Phenomenon in double-symmetrical structure
 Calculated spectrum and experiment spectrum
(HL)3HLCH(HL)3LD(HL)3HLCH(HL)3
(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
4. Design of double-linear filter
 Film structure of double-linear filter
( HL )7 H C ( LH )7 Ld ( HL )7 H C ( LH )7
4. Design of double-linear filter
 Relationship between incident point and spectrum
Incident point move along X axis
( HL)7 H C ( LH )7 Ld ( HL)7 H C ( LH )7
4. Design of double-linear filter
 Relationship between incident point and spectrum
Incident point move along Y axis
( HL)7 H C ( LH )7 Ld ( HL)7 H C ( LH )7
5. Two-chamber integrated multichannel narrowband filter
Film structure of two-chamber filter
C
C
The original structure of the filter designed to be
(HL)4H4.64LH(LH)4L(HL)4H4.64LH(LH)4 with design
wavelength 0 =777.4nm
5. Two-chamber integrated multichannel narrowband filter
 Flow sheet of the preparation of two-chamber
integrated 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.
5. Two-chamber integrated multichannel narrowband filter
 Calculated spectrum of two-chamber integrated
narrowband filter
(HL)4H4.64LH(LH)4L(HL)4H4.64LH(LH)4
5. Two-chamber integrated multichannel narrowband filter
%Transmittance
 Experiment spectrum of two-chamber integrated
narrowband filter
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
780
800
820
840
860
880
Wavelength / nm
(HL)4H4.64LH(LH)4L(HL)4H4.64LH(LH)4
900
920
5. Two-chamber integrated multichannel narrowband filter
 Instrument and experiment condition
Thickness of two spacer layer of which equivalently decreases
by the optical thickness of 0.02L through the etching technique.
5. Two-chamber integrated multichannel narrowband filter
 Instrument and experiment condition
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.
Thank you
谢 谢