1. Manuel Marchiò, Raffaele Flaminio, Shunshi Kuroki
Development and test of an absorption bench to characterize KAGRA mirrors
- Status report
Manuel Marchiò, Raffaele Flaminio, Shunshi Kuroki
JPS Autumn Meeting 2017
2017年10月14日

2. Motivation
Study the absorption of Sapphire, bulk scans and surface maps
Characterize the KAGRA mirrors absorption
R&D – Investigate on Crystalline coating to reduce mechanical losses.
JPS Autumn Meeting 年10月14日- M. Marchiò

3. Absorption measurement method at NAOJ
Photo-thermal Common-path Interferometer
The 1064nm pump periodically changes the temperature of the sample
The thermal lens effect changes the probe wavefront
The perturbation makes interference with the main mode
The detector sense the intensity variation of the central part of the spot.
This variation is proportional to the pump absorption rate
Interference
pattern
Detector size
from the company Stanford Photo-Thermal Solution
JPS Autumn Meeting 年10月14日- M. Marchiò

4. Experimental setup – Previous configuration
Scan along the sample depth
2D maps of the surface and inside the substrate
High power pump laser (25W)
Best sensitivity:
Silica: <1 ppm/cm (bulk) <0.1 ppm (surface)
Sapphire: <5 ppm/cm (bulk) <0.5 ppm (surface)
JPS Autumn Meeting 年10月14日- M. Marchiò

5. Experimental setup – Previous configuration
Translation stage with step motors
Only for small samples, up to 2” diameter
HeNe probe
Only for transparent materials
Scan along the sample depth
2D maps of the surface and inside the substrate
High power pump laser (25W)
Best sensitivity:
Silica: <1 ppm/cm (bulk) <0.1 ppm (surface)
Sapphire: <5 ppm/cm (bulk) <0.5 ppm (surface)
JPS Autumn Meeting 年10月14日- M. Marchiò

6. Experimental setup – NEW configuration
TO MEASURE KAGRA MIRRORS → Large translation stage
- Step motors 1/8063 mm (~0.1μm)
- Move range 250mm in x,y,z
- Designed to bear heavy objects
- Added a cage structure for rigidity
KAGRA mirror size
Up to 2”
mirror size
TAMA300
mirror size Y X
JPS Autumn Meeting 年10月14日- M. Marchiò Z

7. Experimental setup – NEW configuration
- Not transparent to visible light
- Cannot use HeNe probe laser
- Use of 1310 nm laser
TO MEASURE GaAs CRYSTALLINE COATINGS → 1310nm laser probe
JPS Autumn Meeting 年10月14日- M. Marchiò

8. Experimental setup – NEW configuration
Design of two probe lasers (633nm and 1310nm)
HeNe laser
TO MEASURE KAGRA MIRRORS → Large translation stage
Fixed lens f=150mm
Pump laser
lens
Mirror
SAMPLE
Adjustable
lens
Sphere
Mirror
Lens
InGaAs-detector
Mirror
TO MEASURE GaAs CRYSTALLINE COATINGS → 1310nm laser probe
Mirror
Power meter
Fiber port
for the
1310nm laser
Adjustable
Lens f=50mm
Si-detector
Spherical mirror
f=1.25mm
...with the same setup
JPS Autumn Meeting 年10月14日- M. Marchiò

9. Experimental setup – NEW configuration
HeNe laser
Fixed lens f=150mm
Pump laser
lens
Mirror
SAMPLE
Adjustable
lens
Sphere
Mirror
Lens
InGaAs-detector
Mirror
Mirror
Power meter
Fiber port
for the
1310nm laser
Adjustable
Lens f=50mm
Si-detector
Spherical mirror
f=1.25mm
Assembly completed !
JPS Autumn Meeting 年10月14日- M. Marchiò

10. Cleaness improvement Replaced the HEPA filters with new ones
Covered optical table holes
Added a pre-clean booth, with clean suits, air-shower, sticky mats.
Secret: CLEAN OFTEN !
JPS Autumn Meeting 年10月14日- M. Marchiò

11. Cleaness improvement Replaced the HEPA filters with new ones
Covered optical table holes
Added a pre-clean booth, with clean suits, air-shower, sticky mats.
Secret: CLEAN OFTEN !
JPS Autumn Meeting 年10月14日- M. Marchiò

12. Cleaness improvement Replaced the HEPA filters with new ones
Covered optical table holes
Added a pre-clean booth, with clean suits, air-shower, sticky mats.
Secret: CLEAN OFTEN !
JPS Autumn Meeting 年10月14日- M. Marchiò

13. Cleaness improvement Replaced the HEPA filters with new ones
Covered optical table holes
Added a pre-clean booth, with clean suits, air-shower, sticky mats.
Secret: CLEAN OFTEN !
JPS Autumn Meeting 年10月14日- M. Marchiò

14. Cleaness improvement LAST YEAR Replaced the HEPA filters with new ones
Covered optical table holes
Added a pre-clean booth, with clean suits, air-shower, sticky mats.
Secret: CLEAN OFTEN !
NOW
JPS Autumn Meeting 年10月14日- M. Marchiò

15. Next steps Get some sapphire substrates to test
Make sure of the correctness of calibration
Take measurements of sapphire mirrors and GaAs crystalline coatings
JPS Autumn Meeting 年10月14日- M. Marchiò

16. Conclusions Thank you for your attention
We worked hard to make a clean space in TAMA300
We are almost ready to measure KAGRA mirrors
We will measure GaAs samples soon
Thank you for your attention
JPS Autumn Meeting 年10月14日- M. Marchiò