9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada

1. Single mode fibre transmission apparatus Measuring light where it counts Chris F. Dimas, Anthony Knottenbelt, Peter Sinclair Spectral Applied Research June 17, 2014 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

2. Company profile • High-tech manufacturing facility located in Richmond Hill, Ontario • Manufacture laser engines, specialized microscope systems (confocal, TIRF) • Manufacture other fiber optic systems for biomedical OEM customer • 35 Employees • Large R&D department • Last year was purchased by • Andor Technology, and • later by Oxford Instruments 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

3. 405nm laser+single mode fibre • 405nm laser • A Single mode Fiber - designed to carry light only directly down the fibre - the transverse mode • Most common biophotonics applications: • Fluorescence microscopy • Therapeutics • Etching, micromachining 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

4. Problem • Light transmission degrades rapidly in single mode fibre when exposed to 405nm light, 0.01-0.5%/hr (0.3 - 11%/day) • Light is cw laser, and below the damage threshold for fiber: 1MW/cm2 as opposed to 1GW/cm2 • Possible causes:, • LIPSSGonshior, C. P., et al, (2013). Generation of periodic surface structures on silica fibre surfaces using 405nm CW diode lasers. Journal of Non-Crystalline Solids, 361(1), 106-110 • Contamination on end of fibre • Solarization of fibre • Defective AR coating • Burning of input due to improper alignment • Need to measure the degradation • Precisely: +/-0.02%/hr • Over a shorter period of time: 17 hrs., not 1000hrs • Without damaging product 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

5. Techniques Detector (thermopile) fibre 1. laser • Detector is underfilled Detector (integrating sphere) fibre 2. laser • Detector is underfilled at beginning… Lens fibre Camera laser 3. • Can measure light at the focus, off focus, and beamshape Lens 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

6. Technique 1. Directly at fibre fibre laser Detector (thermopile) • Measuring rates of < -0.1%/hr +/- 0.02%/hr, linear decay • Concluded rate after 17 hour test • Realized that detector needed to be thermally controlled, laser needed to be thermally controlled, and that continuous monitoring of laser input power (to provide closed loop feedback) is, unfortunately, not possible 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

7. Techniques 2. At output of relay lens laser Relay lens Detector (integrating sphere) • Corrected for laser thermal, detector thermal, • rig dependency • Measured higher degradation rates, not linear, but with quadratic component as well • Beam profiles at fibre end showed widened beams for contaminated fibre ends (-0.5%/hr) • Perhaps something similar going on even though surfaces were clean • Cannot test every production unit for 1000hrs! • More investigation required!!! 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

8. Beam profiles; before and after cleaning fibre sR ~ w4 Before After cleaning 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

9. Beam profiles, cont.. • In this instance, the change to the beam profile was more severe, did not have significant power degradation rate, and furthermore cleaning the end of the fibre did not improve the beam profile 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

10. White light profilometry 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

11. Technique 3. Using beam profiles Collimating lens Camera fibre laser Relay lens Detector (integrating sphere) • Measuring the beam profile periodically throughout the test 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

12. Beam profile vs. Power out E C 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

13. Beam profile vs. Power out • Shape of beam profile has a close correspondence to % power degradation • Knowing the hours of exposure, know the % deg/hr, one shot-measurement 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

14. Failure mode diagnosis 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

15. Conclusions • Prolonged exposure to 405nm laser light in single mode fibre in our case causes depression in fibre core • The rate of power degradation and beam profile degradation can diagnose the root cause of failure in a fibre • A beam profile gives a more application specific rate of degradation, in addition to allowing for a non-destructive and immediate diagnosis if the number of hours of exposure is known. 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040

16. Thank you! 9078 Leslie St., Unit 11, Richmond Hill, ON L4B 3L8 Canada Fax 905-326-5041 info@spectral.ca www.spectral.ca Phone 905-326-5040