1. Graduate Institute of Photonics and Optoelectronics
~National Taiwan University
Topic Report
S/N of EUV based OCT
Speaker：Yen-Yin Li
Adviser： Sheng-Lung Huang

2. Outline Power for EUV application CCD specific Numerical calculation
Summary
In the end , thank you for your attention.

3. Power for EUV application
Laser source:
1064nm, 2mJ, 20kHz
Average power: 40W
(ideal Amp W/O SRS)
CE from laser to EUV is 1%
The EUV power at source is 400mW
Average power: 40W (2mW/ per shot)
EUV source: 400mW (20μW/ per shot)
Collection optics:
Effective focal length: 100mm
Diameter: 76.2mm (3”)
Hole diameter:30/16/9 mm
(2” f=127/225/400mm)
Collection efficiency modified by angular distribution (Cosθ)^5.84
Collection efficiency: 37.37/43.42/45.11
Vacuum transmission of 55cm traveling at 0.05 torr : 77.75%
Transmission of Si/Zr filter: 80%

4. Power for EUV application
(1)5R, 1BS(RT),
(2)5R,2BS(RRTT)
(3)3R,1BS(RT)
The ideal power for the EUV application is
Vacuum transmission of 100cm traveling at torr : 99.5%
Si/Mo reflection: 60% Beam splitter: T=R=25%
Power before enter the grating:
Michelson type: 269.7μW
Mirau type: 16.9μW; Due to pass through BS twice.
Mirau-like type: 749.3μW

5. CCD specific - ANDOR Pixels:1024x256 Pixel size: 26x26 (μm)
Read noise: 4
Dark current: e-
Pixel well depth:500,000
Maximum full frame rate:10

6. CCD specific - Princeton
Pixels:1340x100
Pixel size: 20x20 (μm)
Read noise: 2.5
Dark current: e-
Pixel well depth:1,000,000

7. SNR equations
In the end , thank you for your attention.

8. Numerical calculation: ANDOR
1024*100
Electron number can’t excess the well depth.
Exposure time is just 60 ms. (100ms per frame)
The SNR is limited by shot noise.
SNR= mW

9. Numerical calculation: Princeton
1340*100
Electron number can’t excess the well depth.
Exposure time is just 150 ms. (??? per frame)
The SNR is limited by shot noise now.
SNR= mW

10. Summary
The SNR of EUV based OCT is usually limited by the shot noise due to can’t arise the exposure time to do the average.
The SNR can arise after the Fourier transform. For the ideal case, SNR can be improved N/2 times where N is the CCD pixel number.
In the end , thank you for your attention.
Future work, I will discuss the collector shape and the spectrometer.

11. Thank you for your attention
End
In the end , thank you for your attention.
Thank you for your attention

12. SNR: source variation
In the end , thank you for your attention.

13. CCD selection
鎖相環（PLL: Phase-locked loops）是一種利用反饋（Feedback）控制原理實現的頻率及相位的同步技術，其作用是將電路輸出的時鐘與其外部的參考時鐘保持同步。當參考時鐘的頻率或相位發生改變時，鎖相環會檢測到這種變化，並且通過其內部的反饋系統來調節輸出頻率，直到兩者重新同步，這種同步又稱為「鎖相」（Phase-locked）。