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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 2010/8/13 at Caltech Prof. Chao,

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SLIDE 1

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

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SLIDE 2

Reflection Transmittion Scattering Absorption

1=R+T+S+A Total Loss ≡ 1-R-T = S+A

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 3

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

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SLIDE 4

Ω

ΩL input rate

  • utput frequency

Ψ

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

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SLIDE 5

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

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SLIDE 6

Coating Apparatus

Ion Beam Sputtering

  • -- dense film
  • -- higher refractive index

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 7

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 8

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) Optical Microscope

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 9

Single TiO2 film

Annealing effect on ion-beam-sputtered titanium dioxide film Wen-Hsiang Wang and Shiuh Chao Department of Electrical Engineering, National Tsing Hua University, Hsin-Chu, Taiwan September 15, 1998 / Vol. 23, No. 18 / OPTICS LETTERS 1417

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 10

Anatase A(101)

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 11

(A) as-deposited (B) annealed 200 oC

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 12

(C) annealed 225 oC (D) annealed 300oC

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 13

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 14

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 15

(1) GOOD POLISHING=> REDUCE SUBSTRATE ROUGHNESS (2) RAISE UP THE CRYSTALLIZATION TEMPERATURE OF THE FILM

Substrate roughness=>

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SLIDE 16

Single TiO2-SiO2 mixed film

Characteristics of ion-beam-sputtered high refractive- index TiO2-SiO2 mixed films Shiuh Chao and Wen-Hsiang Wang Department of Electrical Engineering, National Tsing Hua University, Hsin-Chu, Taiwan Min-Yu Hsu and Liang-Chu Wang Chung-Shan Institute of Science and Technology, Tao-Yuan, Taiwan

  • Vol. 16, No. 6/June 1999/J. Opt. Soc. Am. A 1477

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 17
  • 65-

5% SiO2

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 18
  • 66-

9% SiO2

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 19
  • 67-

17% SiO2

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 20

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 21

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 22

(A) SiO2: 0% annealed 300oC (B) SiO2: 17% annealed 300oC

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 23

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 24

圖(二十八) TiO2-SiO2光學混合膜的退火相圖

  • 84-

“phase diagram” of the mixed film

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 25

Multi-layer dielectric mirror with the mixed film

Low-loss dielectric mirror with ion-beam-sputtered TiO2–SiO2 mixed films

Shiuh Chao, Wen-Hsiang Wang, and Cheng-Chung Lee 1 May 2001 y Vol. 40, No. 13 y APPLIED OPTICS 2177

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 26

TiO2+ SiO2 17% TiO2+ SiO2 17% TiO2+ SiO2 17% SiO2 SiO2 Zerodur nd = 1/4 λ nd = 1/4 λ

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 27

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 28
  • 50
  • 100
  • 50
  • 100

deposition temp.(820C)

  • 34%

▲ SiO2 : 0%

  • SiO2 : 17 %

Annealing Temperature (0C) Total Loss Change (%) Total Loss Change (%)

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 29

3 mm (A) (B) 1.5 mm SiO2:0% as-deposited damage threshold: 2.8 KJ/cm2

(A) (B): damaged spot under optical microscope

Laser Induced Damage

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 30

(C) (D) SiO2:0% as-deposited damage threshold: 2.8 KJ/cm2 (C) )(D) damaged spot under AFM

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 31

(A) (B) 3 mm SiO2: 17% annealed 200oC Damage threshold: >6.37 KJ/cm2

(A) Optical microscope (B) AFM of the exposed spot => no damage

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 32

(A) (B)

Depth profile for the mirrors (A) as-deposited(B) after 400oC annealing (17% mixing) (Tracing the Ti2p Si2p and O1s by ESCA)

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 33

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 34

as-deposited 2000C 3000C 4000C

well-defined as-deposited 4000C 圖(三十五)以TiO2-SiO2(17%)混合膜為高折射係數層的雷射反射鏡退 火後 的穿透光譜(A)為從光譜儀得到的量測值(B)為從ESCA對 鏡片膜層原子分佈的偵測，以薄膜矩陣電腦模擬分析穿透率的結果

(A) (B)

  • 107-

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 35

Other methods for depositing mixed films

TiO 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 thinpair

structure 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 from SiO2-dominant to TiO 2 -dominant as TiO2 content in the film increased. 1 August 1991 / Vol. 30, No. 22 / APPLIED OPTICS 3233

Slow alternating sputter for “nano-film” ?

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan

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SLIDE 36

Mixed films of TiO2–SiO2 deposited by double electron-beam coevaporation Jyh-Shin Chen, Shiuh Chao, Jiann-Shiun Kao, Huan Niu, and Chih-Hsin Chen We used double electron-beam coevaporation to fabricate TiO2–SiO2 mixed films. The deposition process included oxygen partial pressure, substrate temperature, and deposition rate, all of whichwere real-time computer controlled. The optical properties of the mixed films varied from pure SiO2 to pure TiO2 as the composition of the films varied accordingly. X-ray diffraction showed that the mixed films all have amorphous structure with a SiO2 content of as low as 11%. Atomic force microscopy showed that 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 better than 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

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SLIDE 37

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

2010/8/13 at Caltech LIGO

  • Prof. Chao, National Tsing Hua

Univ., Taiwan