Multichannel Phenomenon of Symmetrical Structure Optical Filter

1. Multichannel Phenomenon of Symmetrical Structure Optical Filter Guoxun Tian April 23, 2007 ATMS790 Seminar (Dr. Pat Arnott)

2. Outline Mutiple reflection in Multilayer film Introduction of Fabry-Perot filter Multichannel Phenomenon in double-symmetrical structure Design of double-linear filter Two-chamber integrated multichannel narrowband filter Review

3. 1.Mutiple reflection in Multilayer film • A multilayer

4. 2.Fabry-Perot filter A Fabry-Perot filter showing multiple reflections in the spacer layer

5. 2.Fabry-Perot filter • Structure of Fabry-Perot Filter C Mirror Cavity Mirror This is a symmetrical structure and the position of channel was calculated by equivalent surface method

6. 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.

7. 2.Fabry-Perot filter • Equivalent surface method

8. 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/） Changesthe thickness of layer C to satisfy the following formula  1+  2－2nC/=2k (k=±1，2，3） = 2nC/ [2k +( 1+  2)]

9. 2.Fabry-Perot filter • Multichannel Fabry-Perot Filter Two-channel filter 492nm/598nm Three-channel filter487nm/550nm/632nm

10. 2.Fabry-Perot filter • Channel can be moved continuously by changing layer C • 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.

11. 3.Multichannel Phenomenon in double-symmetrical structure • Double-symmetrical structure based on Fabry Perot structure Coupling layer C d C Fabry-Perotstructure Fabry-Perot structure

12. 3.Multichannel Phenomenon in double-symmetrical structure • Adjustment of Channel position • Calculated spectrum of double-symmetrical structure Movement ofChannel position while d changes and C is fixed

13. 3.Multichannel Phenomenon in double-symmetrical structure • Adjustment of Channel position • Calculated spectrum of double-symmetrical structure Movement ofChannel position while C changes and d is fixed

14. 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

15. 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

16. 4.Design of double-linear filter • Film structure of double-linear filter

17. 4.Design of double-linear filter • Relationship between incident point and spectrum • Incident point move along X axis

18. 4.Design of double-linear filter • Relationship between incident point and spectrum • Incident point move along Y axis

19. 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 =777.4nm

20. 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.

21. 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

22. 5.Two-chamber integrated multichannel narrowband filter • Experiment spectrum of two-chamber integrated narrowband filter (HL)4H4.64LH(LH)4L(HL)4H4.64LH(LH)4

23. 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.

24. 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.