1. Hi Repetition Rate MOPA Based Fibre Laser for Micro Machining Applications Bill O’Neill Centre of Industrial Photonics Institute for Manufacturing University of Cambridge

2. ..who loves fibre lasers? Yes, you are right Bill. I really really love Fibre Lasers

3. New Laser Technologies  Fiber lasers have changed the landscape of high power industrial laser systems & applications  Ultrafast pico/femto second systems finding applications in micro-system/electronics fabrication  High efficiency low cost Yb fiber systems are replacing conventional sources in marking/coding applications  Low cost, <$15k @ 20W typical high brightness Yb lasers, prf 500kHz  New applications can be found in the high-end processing such as trimming, patterning, machining, drilling..

4. System under evaluation.. SPI G3 Yb doped Pulsed Fibre Laser Nutfield XLR8 Two Axis Scan Head

5. directly modulated Laser Diode SPI G3 Yb doped Pulsed Fibre Laser 1 064nm wavelength MOPA (Master Oscillator Power Amplifier) architecture Yb fiber laser Amplifier Chain (GTWave Technology) Seed Lase r Average Power: 20W Spot size: 40um with x3 Beam Expander, 9mm input beam diameter Pulse width: 10-70ns FWHM Peak Power: 14kW per pulse Power density: up to 1GW/cm 2 for 40um spot size Pulse Energy: 0.8mJ max Pulse frequency: up to 500KHz, 25 preset pulse waveforms Pre-Amp Post-Amp

6. Pulse tuning  25 preset pulse waveforms on 20W Waveforms optimised for peak pulse power at specified repetition rate 20W average power maintained at higher rep rates

7. ...PV cell fabrication

8. Si processing at various  The optical reflectivity&The optical penetration length of mono crystalline silicon for various wavelength, measured at room temperature, Bauerle, D. (2000) Laser Processing and Chemistry, Springer, 3 rd edition. Si exhibits higher penetration at 1 µm wavelength Large melt volumes under high intensity illumination Poor definition and micro cracking

9. Optical Properties of Si  Transmission & Reflection Abovethemelting pointAbsorption~ 4535%,f ( 

10. Etch rates

11. ..explosive ejection  Percussion drilled holes prior to ultrasonic cleaning for 10 pulses delivered at repetition rates of 25kHz, 20.8 Jcm -2 (left) and 20 pulses at 65 kHz, 8 Jcm -2 (right). Percussion drilled holes from after ultrasonic cleaning for 10 pulses delivered at repetition rates of 25kHz, 20.8 Jcm -2 (left) and 20 pulses at 65 kHz, 8 Jcm -2 (right).

12. ..Scribing

13. ..Si scribing Machined trenches produced at 25kHz, at 100 MWcm -2, with 3 over scans at a scanning speed of 100 mms -1 (top), and 250 kHz at 50 MWcm -2, with 5 over scans at a scanning speed of 2500 mms -1 (bottom),

14. ...Si percussion drilling

15. Glassy carbon machining  Glassy carbon used as Nano Print toolset for PDMS replica’s  TG ~ 3000 0 C  FIB machined ~ 7nm-200  m  Laser machined ~ 10  m+

16. High precision machining/cleaning

17. NPL Micro probe

18. ..GC micro fluidics Blood plasma separator

19. Conclusion & Future Outlook  The low cost of MOPA based Yb fibre lasers, and pulsing flexibility offer unique low cost solutions to  -systems fabrication  Effective processing of Si for a variety of marking, scribing & drilling applications & using 20W< 500kHz @ 1064nm  Further characterisation of Si machining process is required but shows promise  Further development of Laser processing capabilities Process to include: Direct patterning of micro fluidics PV cell processing Micro structuring of bio-materials Metal polishing

20. ..even dogs love lasers Thanks! wo207@cam.ac.uk