Developing the TiO 2 /SiO 2 mixed films for low optical loss dielectric mirror --- A retrospect Prof. Shiuh Chao Institute of Photonics Technologies National Tsing Hua University Taiwan, R.O.C. 2010/8/13 at Caltech LIGO Prof. Chao, National Tsing Hua Univ., Taiwan LIGO-G1000746
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Developing the TiO 2 /SiO 2 mixed films for low optical loss dielectric mirror --- A retrospect
Developing the TiO 2 /SiO 2 mixed films for low optical loss dielectric mirror --- A retrospect. Prof. Shiuh Chao Institute of Photonics Technologies National Tsing Hua University Taiwan, R.O.C. LIGO-G1000746. R eflection. S cattering. A bsorption. T ransmittion. 1=R+T+S+A - PowerPoint PPT Presentation
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Developing the TiO2/SiO2 mixed films for low optical loss dielectric
mirror --- A retrospect
Prof. Shiuh Chao
Institute of Photonics Technologies
National Tsing Hua University
Taiwan, R.O.C.
2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
LIGO-G1000746
Reflection
Transmittion
Scattering
Absorption
1=R+T+S+A
Total Loss ≡ 1-R-T = S+A2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
干涉條紋圖形
順時針光束
逆時針光束
抖動器
陽極充氣管
曲面鏡
陽極
腔長控制器
增益氣體
合成稜鏡
陰極光接收器
光腔長度偵測器 數位訊號輸出
薄膜鏡
輸入訊號
光學共振腔
逆時針光束 干涉條紋圖
陀螺儀輸出訊號
RING LASER GYROSCOPE
High Q resonator low optical loss for the mirrors 2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
ΩΩLinput rate
ou
tpu
t fr
equ
ency
Ψ
)4
(L
A
s
dA
cL
)32
(2
LOCK-IN EFFECT IN RLG
To avoid lock-in effect => low back-scatter mirror is critical
2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
H
H
H
L
L
Substrate
nd = 1/2 λ
H: TIO2, TA2O5 L: SIO2
Multi-layer dielectric mirror
2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
Coating Apparatus
Ion Beam Sputtering
--- dense film
--- higher refractive index
2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
Instrumental analysis for mirror characterization
Optical constants and thickness: Spectrophotometer
Concentration: Rutherford Backscattering
Spectrometer
Structure:X-Ray Diffractometer
Surface roughness:Atomic Force Microscope
Total loss: Cavity ring-down lossmeter
Optical Damage:Nd:YAG Laser
Chemical bonding: Electron Spectroscopy
for Chemical Analysis(ESCA)
OpticalMicroscope
2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
Single TiO2 film
Annealing effect on ion-beam-sputtered titanium dioxide film
Wen-Hsiang Wang and Shiuh ChaoDepartment of Electrical Engineering, National Tsing
Other methods for depositing mixed filmsTiO 2-S102 mixed films prepared by the fast alternating sputter method
Shiuh Chao, Cheng-Kuel Chang, and Jyh-Shin Chen We introduced the fast alternating sputter method and its application on deposition of TiO2-SiO2 mixed
films. By using fast alternating sputter, the TiO2 and SiO2 were completely mixed in the film, and no thinpairstructure could be found by x-ray diffraction. The structure of the mixed films was amorphous in a wide
composition range. The optical properties of the mixed films in the visible and near infrared changed fromSiO2-dominant to TiO 2 -dominant as TiO2 content in the film increased.
We used double electron-beam coevaporation to fabricate TiO2–SiO2 mixed films. The depositionprocess included oxygen partial pressure, substrate temperature, and deposition rate, all of
whichwerereal-time computer controlled. The optical properties of the mixed films varied from pure SiO2 to pureTiO2 as the composition of the films varied accordingly. X-ray diffraction showed that the mixed filmsall have amorphous structure with a SiO2 content of as low as 11%. Atomic force microscopy showedthat the mixed film has a smoother surface than pure TiO2 film because of its amorphous structure.
Linear and Bruggeman’s effective medium approximation models fit the experimental data betterthan other models.
APPLIED OPTICS Vol. 35, No. 1, 90, 1 January 1996
2010/8/13 at Caltech LIGO
Prof. Chao, National Tsing Hua Univ., Taiwan
Mixed film for LIGO application
• One more factor ---- mechanical loss ---- should be added for investigation
• Near future: systematically characterizing the mechanical loss of the films
• Current effort: recovering the old coating conditions for the films