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Calibration Bench for Fast Wire Scanners: Optical Design and Issues

Calibration Bench for Fast Wire Scanners: Optical Design and Issues. Student Meeting 16-10-2012 Jose Luis Sirvent. 1. Working Principle. Optical system for calibration Laser position well known Scan = Cross the two beams Position recorded Optical signal recorded

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Calibration Bench for Fast Wire Scanners: Optical Design and Issues

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  1. Calibration Bench for Fast Wire Scanners:Optical Design and Issues Student Meeting 16-10-2012 Jose Luis Sirvent

  2. 1. Working Principle • Optical system for calibration • Laser position well known • Scan = Cross the two beams • Position recorded • Optical signal recorded • Calibration table for position • The optical system is mobile • Precision linear stages *Pictures Extracted from: A. Lokhovitskiy et al. Fast Wire Scanner Calibration. Proceedings of DIPAC2009, Switzerland2009.

  3. 2. Why am I working on it? • 1. Laser source  Optical fibre (Impact??) • Rotating platform = Space limitation (The fibre is flexible) • 2. System modeling (Zemax) • 3. Working verification of the components already selected • MMF Fibre / 532nm Laser / PAF-X-5-A Fiber-port / Mirror / Beam Splitter / Beam Displacer / LA1172 Lens • 4. Proposal of new components / lens for optimization

  4. 3.Base lens system • Model Introduced in Zemax • Study of the Base behavior Beam-Splitter 400-700nm Beam-Displacer BD27 Tank Wall Mirror Focusing Lens LA1172 PhotoDetector Fibre Port (MMF) PAF-X-5-A

  5. 4. Distance issues and compromise • Linear Stage range= + - 50mm • Horizontal Scanner crossing points • Min:225.7mm,Mean:309.4mm,Max:332.1mm • Vertical Scanner crossing points • Min:199.mm,Mean:214.6mm,Max:240.6 mm • Desired Specs: • Beam as small as possible (100 – 200 um) • Distance range: 199.5 – 332.1mm (132.6mm) • Focal distance: 265.8mm *Distances with respect to the internal tank wall

  6. 5. System performance (MMF) • Smaller beam size reached in focal point? • Fiber Core: 100 um • F1:4.5mm F2~300mm (Magnification ~ 70) • Focused Spots > 7mm (Impossible smaller with this system) • Spots Separation: 2.7mm

  7. 5. System performance (SMF) • Gaussian optics should be considered: • Fibre MDF(532nm): 3.5nm • Objective: Minimize 2Wo and maximize 2Zr (Compromise) • M2= Quality factor of the laser (Considered 1) • W1= Gaussian waist before focusing lens

  8. 5. System performance (SMF) • Gaussian optics should be considered: • Which is the value of W1 just before the lens LA1172? • W1= 508 um (Current fiber port) (Equation estimation: 2Zr=200mm 2Wo=250um ) • Change of lens in Fiber-Port  Movement on X • Change of Focuser lens LA1172(F400) Different lines

  9. 5. System performance (SMF) • Moving the model to Zemax 12 • Protocol followed: • The fiber port is always kept: Only adjust Fiber - 1st Lens • Simulated an aspheric lens with similar characteristics • The assembly will be as compact as possible • 3 Focuser lens tested • Thorlabs LA1884 (Focal 300mm) • Thorlabs LA1172 (Focal 400mm) • Thorlabs LA1464 (Focal 1000mm) • 2 Sources tested • Current Laser 532nm (Green) + SMF MFD 3.5um • Laser LP405-SF10 405nm (Blue) + SMF MFD 2.9um • Decision Parameters: Wo & ZR

  10. 5. System performance (SMF) • Model appearance Mirror Focal point Scanners Crossing Points

  11. 5. System performance (SMF) • Beam Waist at the scanners crossing points Scanner V Scanner H • Same lens configuration with 405nm = Smaller Wo • Bigger lens F dist = ++ Wo & ++Zo • Smaller lens F dist = --Wo & --Zo • Most important factor for decission= Bigger Zo • Better compromise  Conf 6!

  12. 5. System performance (SMF) • Vertical and horizontal Scans Simulation • Evolution of the light received in the scanner range (200um wire) • Comparison between two configurations (530 nm F400 & 405nm F1000)

  13. 5. System performance (SMF) • Vertical and horizontal Scans Simulation • Evolution of the light received in the scanner range (30um wire) • Comparison between two configurations (530 nm F400 & 405nm F1000)

  14. 5. System Performance (SMF) • Simulation of a Scan in D= 240mm (Vertical)

  15. 6. Practicalresultswith SMF • 1. Systemparameters: • Lamda: 532nm • Lens2: F400mm • Fibre: SMF MFD 9.2um @ 1310nm (MFD @ 532nm?) Thisfibreisnot SMF forthiswavelenght.

  16. 7. Second Set of Simulations • A) 4 Different configurations will be studied and compared: • 1. Fiber-Port + Focuser lens together (400mm) • 532nm & 405nm • D (lens Focus)= 410.71 mm • 2. Beam displacer + Focuser lens together (300mm) • 532nm & 405nm • D (lens Focus)= 318.15 mm

  17. 7. Second Set of Simulations • Beam Waist at the scanners crossing points

  18. 7. Second Set of Simulations • Vertical and horizontal Scans Simulation • Evolution of the light received in the scanner range (30um wire) • Comparison between two configurations (530 nm F400 & 405nm F1000)

  19. 8. Simulations: In conclusion • 1. The most promising configurations are • 405nm Laser, SMF (MFD 2.9um) & Focal lens LA1172 (F400mm)  Around 1.5% better • 530nm Laser, SMF (MFD 3.5um) & Focal lens LA1172 (F400mm) • When wire in beam the light decreases from 100% to 75-82% (~20% ) • 2. Components to be ordered to make the system work (Thorlabs): • A) Focal lens for photodiode: LA1951 - N-BK7 Plano-Convex Lens, Ø1", f = 25.4 mm, Uncoated  • B) SMF for our laser (MFD 3.5um & 530nm): P2-460A-PCSMA-1 - SM Patch Cable, 450-600 nm, FC/PC to SMA, 1 m Optional: • C) Laser 405nm with fibre pigtail FC/PC: LP405-SF10 - 405 nm, 10 mW, B Pin Code, SM Fiber-Pigtailed Laser Diode, FC/PC 

  20. 9. Practical Verification • 1. Suitable SMF fibre arrived (MFD @ 532 = 3.5um) • 2. Suitable focuser lens for photodiode arrived (LA1951 F=25.4mm) • 3. Suitable mirror also arrived (25MG00) Scanning range

  21. 9. Practical Verification • A) Beam size reduction reached using the suitable SMF Fibre for 532nm Several modes Only one mode As simulated Gaus. Waist ~ 100um Before (W~300um) Fibre for 1310nm After (W~100um) Fibre for 532nm As simulated, the new beam waist in the focal point is in the order of 100um Obviously there is a reduction of the beam waist due to the MFD of the new fibre. The new fibre guarantees the Single Mode Behavior

  22. 9. Practical Verification Signal Response (Copper) Beam Diam ~ 200um --- Carbon wire 170um Decay 50% (Each beam seems to be completely covered) Signal Response (Carbon) Beam Diam ~ 200um --- Carbon wire 30um Decay 25% (Each beam seems to be partly covered) It’s clearly visible that the beam is Gaussian Results similar to the simulations! System Settings: Offset calibrated to 0V ambient light Photodiode Biased (-10V) I/V Ampliffication 10e6 Low Pass filter 1MHz DC Coupling • B) Signal obtained when crossing the beam with two different wires Copper wire (170um) ~50% Decrease Carbon wire (30um) TransimpedanceAmpliffier Settings ~25% Decrease

  23. 10. Final remarks • 1. With very few modifications of the original assembly the desired results are achieved. • 2. Jonathan, Julien, Juan and William (sorry if I forget someone) made a very good component selection. Performance proved by simulations. • 3. The system now it’s ready for the assembly in the final tank. • 4. While performing last lens adjustments in the laser, It suddenly stopped working • Back-reflections damage?, Overheated?, Electrical failure in the temperature control? • I contacted the company World Star Tech inc. looking for a possible solution, explanation. • Finally testing with a little modification (White wire to 3.3V, TTL->1) the laser continues working • 5. However the Laser coupling to SMF it’s not good enough • Options: • Change the laser for a pigtailed one • Adapt the laser with suitable components SMA Connector for MMF

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