![MMU FORC 17/11/2015
Nonlinearity is an effect of high intensity light (laser)
travelling through an optical fiber which will alter the
properties of the medium.
Anharmonic movement of electrons when a field is
applied
P(t) = ϵ0[χ(1)E1(t)+ χ(2) E3(t)+ χ(3) E3(t)+· · ·]
The third order susceptibility χ(3) leads to the
nonlinear effect such as self-phase modulation and
Brillouin scattering.
Literature Review – Nonlinear Fiber
Optics](https://image.slidesharecdn.com/0bd0303c-c192-4f11-86f2-d7152bb6398a-160303090711/85/WCS_2-10-320.jpg)
WCS_2
- 1. BRILLOUIN CHARACTERIZATION OF OPTICAL MICROFIBERS Name: Kazi Tasneem Farhan Programme: M. Eng. Sc. Faculty: FOE Registration Date: 1st February 2013 Supervisor: Assoc. Prof. Dr. Zulfadzli Yusoff Co-supervisor: Siti Azlida Ibrahim Ghazali MMU FORC 17/11/2015
- 2. Content MMU FORC 17/11/2015 Background Motivation Problem Statement Research Objective Nonlinear fiber optics Microfibers Stimulated Brillouin scattering Introduction Fabrication of Microfibers Brillouin Effect Characterization Brillouin Scattering Brillouin Lasing Spatial Characterization of Brillouin Effects in Microfibers Introduction Microfiber Shape Profile Insertion Loss Measurement Brillouin Scattering Brillouin Lasing Spatial Characterization of Brillouin Effects in Microfibers Conclusion Future Recommendations
- 4. Introduction - Background MMU FORC 17/11/2015 Light has been a medium of communication for many centuries. The entire world relies on the exchange of information in bulk over long distances. The ability of silica (single-mode) fibers to transmit large amount of information makes it an excellent choice for the communications field. At around 1974 fiber optics came into the world of communication and since then it has experienced a growth in transmission capacity by 10 times every four year.
- 5. Introduction - Background MMU FORC 17/11/2015 The light travelling through the fiber experiences scattering. Two types of scattering: Linear scattering and Nonlinear scattering When nonlinear scattering occurs, the fiber does not produce a linear output to power changes at the input. Stimulated Brillouin scattering is one type of nonlinear scattering. The incident light interacts with sound wave in the fiber and scatters backward with downshifted frequency. The downshift is equal to the acoustic velocity.
- 6. Introduction - Motivation MMU FORC 17/11/2015 There is always a technological drive in making devices compact, cheaper and greener. One of the many focuses of technological advancements are nonlinear optics. Microfibers show great potential to be used as a nonlinear medium for nonlinear devices. They show nonlinear properties equivalent to very long lengths of fibers (~kms) just in a short length of microfiber (~cms).
- 7. Introduction – Problem Statement MMU FORC 17/11/2015 Among the nonlinear effects in optical fibers, Brillouin scattering is the easiest to observe as it has the lowest threshold power. Characterization of Brillouin scattering in various long microfibers has not been reported yet.
- 8. Introduction – Research Objectives MMU FORC 17/11/2015 To design and fabricate uniform microfibers of different lengths and diameters from different types of fibers. To characterize and compare Brillouin effects in the fabricated microfibers through three different approach (scattering, lasing and spatial measurement).
- 9. LITERATURE REVIEW MMU FORC 17/11/2015
- 10. MMU FORC 17/11/2015 Nonlinearity is an effect of high intensity light (laser) travelling through an optical fiber which will alter the properties of the medium. Anharmonic movement of electrons when a field is applied P(t) = ϵ0[χ(1)E1(t)+ χ(2) E3(t)+ χ(3) E3(t)+· · ·] The third order susceptibility χ(3) leads to the nonlinear effect such as self-phase modulation and Brillouin scattering. Literature Review – Nonlinear Fiber Optics
- 11. Literature Review – Microfibers MMU FORC 17/11/2015 Figure: The segments of a microfiber Figure : First Images shows the light guided in the core. Second image shows the light guided outside the core but within the cladding. Third image shows the light guided outside the cladding and the air acting as the cladding
- 12. Literature Review – Stimulated Brillouin scattering MMU FORC 17/11/2015 Figure : Graphical representation of Stimulated Brillouin scattering process Light travelling through a medium interacts with the acoustic phonons within the optical waveguide. The scattered light (ωS Stokes) travelling opposite to the incident beam (ωL) and is downshifted in frequency by an amount equal to the acoustic frequency (Ω).
- 13. RESEARCH METHODOLOGY MMU FORC 17/11/2015
- 14. Research Methodology - Introduction MMU FORC 17/11/2015 Design and fabricate microfibers of different shapes and sizes, from different kinds of fibers Microfiber profiles Insertion loss measurement Brillouin effect characterization of the microfibers fabricated Brillouin scattering Brillouin lasing Spatial characterization of Brillouin effects
- 15. Research Methodology - Fabrication of Microfibers MMU FORC 17/11/2015 Figure : Complete microfiber fabrication rig
- 16. Research Methodology - Fabrication of Microfibers MMU FORC 17/11/2015 Figure : The full mechanism length of microfiber Where radius rω is the final waist diameter of the taper, ro is the original radius of the fiber, LT is the total length of the microfiber, LH is the heat zone, LE is the extended length
- 17. Research Methodology - Fabrication of Microfibers MMU FORC 17/11/2015 Figure : Shape profile and simulated profile of a microfiber with a waist length LT of 20cm and waist diameter rω of 30 µm Figure : Matlab simulation of desired Microfiber
- 18. Research Methodology – Fabrication of Microfibers MMU FORC 17/11/2015 Insertion loss measurement Figure : Insertion loss measurement setup
- 19. Research Methodology – Brillouin Scattering MMU FORC 17/11/2015 Brillouin scattering Figure : Brillouin scattering measurement setup
- 20. Research Methodology – Brillouin Lasing MMU FORC 17/11/2015 Figure : Brillouin lasing measurement setup
- 21. Figure : Setup for Spatial Characterization of Brillouin Effects Research Methodology – Spatial Characterization of Brillouin Effects MMU FORC 17/11/2015
- 22. EXPERIMENTAL RESULTS & DISCUSSION MMU FORC 17/11/2015
- 23. Experimental Results & Discussion - Introduction MMU FORC 17/11/2015 Microfiber shape profile Insertion loss measurement Brillouin scattering Observation in three types of microfibers of different lengths and waist diameters. Brillouin lasing Comparison between SMF microfiber and chalcogenide microfiber. Spatial characterization of Brillouin effects Characterization of Brillouin effects along the length of a microfiber.
- 24. Figure : The shape profile for all microfibers produced Experimental Results & Discussion - Microfiber Shape Profile MMU FORC 17/11/2015
- 25. Experimental Results & Discussion - Microfiber Shape Profile MMU FORC 17/11/2015 The fabricated microfibers profile follow shape of the simulated profile within ±5%. The “ripples” in the plot is due to errors in image processing. The microfiber with 3µm waist is hard to profile due to too much movement.
- 26. Experimental Results & Discussion - Insertion Loss Measurement MMU FORC 17/11/2015 Figure : Power performance all the microfibers produced of different shapes and sizes. The power profile for microfibers of different shapes and sizes for different fiber material composition is also showed.
- 27. Experimental Results & Discussion – Insertion Loss Measurement MMU FORC 17/11/2015 Insertion loss is made up of loss in the tapered loss as well as transmission loss in the uniform waist. The transmission loss is not significantly different with the various length or diameter. The insertion losses are mainly due to the tapered loss. Ge-doped have lower loss than SMF Microfibers
- 28. Experimental Results & Discussion - Brillouin scattering MMU FORC 17/11/2015 Microfibers with same lengths but different diameters Figure : Brillouin stokes from SMF, Ge-doped and Ga-doped microfibers with same length but different diameter of 3 µm, 5 µm and 10 µm
- 29. Experimental Results & Discussion - Brillouin Scattering MMU FORC 17/11/2015 Microfibers with same lengths but different diameters Figure : The combined plot for of Brillouin stoke for increasing waist diameter of SMF, Ge-doped and Ga-doped Microfibers with fixed length
- 30. Experimental Results & Discussion - Brillouin scattering MMU FORC 17/11/2015 Peak power of Brillouin stoke decreases for increasing waist diameter of SMF, Ge-doped and Ga-doped Microfibers with fixed length. Nonlinear coefficient (γ) is defined by where Aeff is he effective mode area and n2 is the refractive index. As waist diameter increases so does Aeff , thus nonlinearity decreases so does Brillouin stoke. Ga-doped microfibers shows the highest stoke power. Second is Ge-doped and lastly SMF.
- 31. Experimental Results & Discussion - Brillouin scattering MMU FORC 17/11/2015 Microfiber of same diameter but different lengths Figure : Brillouin stokes from SMF, Ge-doped and Ga-doped Microfibers with same diameter but different lengths of 10 cm, 20 cm and 30 cm.
- 32. Experimental Results & Discussion - Brillouin scattering MMU FORC 17/11/2015 Microfiber of same diameter but different lengths Figure : The combined plot for of Brillouin stoke for increasing length of SMF, Ge-doped and Ga-doped Microfibers with fixed waist diameter.
- 33. Experimental Results & Discussion - Brillouin scattering MMU FORC 17/11/2015 The increase in peak power of Brillouin stoke for increasing length of SMF, Ge-doped and Ga-doped Microfibers with fixed waist diameter. The value of the Brillouin threshold is represented with good approximation using the equation below where Leff is he effective mode area and n2 is the refractive index Ga-doped microfibers shows the highest stoke power. Second is Ge-doped and lastly SMF.
- 34. Experimental Results & Discussion - Brillouin Lasing MMU FORC 17/11/2015 -80 -70 -60 -50 -40 -30 -20 -10 0 1.90940000000000E+14 1.90960000000000E+14 Power(dB) Frequency (THz) -80 -70 -60 -50 -40 -30 -20 -10 0 1.90940000000000E+14 1.90960000000000E+14 Power(dB) Frequency (THz) Figure : BEFL using SMF Microfiber with waist 1µm and length 13cm Figure : BEFL using Chalcogenide Microfiber with waist 1µm and length 13cm 10.68 GHz 7.05 GHz
- 35. Experimental Results & Discussion - Brillouin Lasing MMU FORC 17/11/2015 BEFL using SMF microfiber of length 13cm and waist 1 µm. BEFL using chalcogenide microfiber of length 13cm and waist 1 µm. The generated Brillouin gain is not sufficient to overcome the cavity loss hence no lasing was observed. The difference in frequency shift is due to the different material used in the two fibers.
- 36. Experimental Results & Discussion - Spatial Characterization of Brillouin Effects MMU FORC 17/11/2015 A sample of 20 cm length and 3.07 µm waist diameter to perform a Brillouin gain measurement spatially. Figure : Profile of microfiber used for spatial resolution measurement
- 37. Experimental Results & Discussion - Spatial Characterization of Brillouin Effects MMU FORC 17/11/2015 Figure : Brillouin gain along the length of the microfiber Pigtail attached to the microfiber 2.5cm uniform waist 5cm transitions Zoom over 12.5 cm of the microfiber
- 38. Experimental Results & Discussion - Spatial Characterization of Brillouin Effects MMU FORC 17/11/2015 The sample shape profile used can be seen to match the simulated shape profile quite effectively. The sample has a diameter maintained around 3.07 µm. The transitions of the microfiber show a Brillouin gain of ~ 11.1 GHz which is like 5cm region around the waist. The uniform waist of 2.5cm shows two frequencies. One at 11.1 GHz and another at 10.85 GHz. The 10.85GHz frequency according to the experiment is also found to be 3 times in higher magnitude than the 11.1 GHz.
- 39. Experimental Results & Discussion - Spatial Characterization of Brillouin Effects MMU FORC 17/11/2015 Figure : Brillouin Gain Pattern and Strength for Microfibers with wait 3 µm to 4 µm Figure : Brillouin Gain Simulation for Microfiber with waist diameter of 3.07 µm
- 40. Experimental Results & Discussion - Spatial Characterization of Brillouin Effects MMU FORC 17/11/2015 The initial simulation done by our collaborator Jean Charles at Femto-ST shows the frequency around the waist changes from 10.85 GHz to 11.1 GHz. This full acoustic spectrum was published in Nature Photonics (J. C. Beugnot, S. Lebrun, G. Pauliat, H. Maillote, V. Laude, T. Sylvestre, Brillouin light scattering from surface acoustic waves in a subwavelength-diameter optical fiber, Nature Communications October 2014 ). Our observations match to the simulated results shown in the publication.
- 41. CONCLUSION AND FUTURE RECOMMENDATIONS MMU FORC 17/11/2015
- 42. Conclusion and Future Recommendations - Conclusion MMU FORC 17/11/2015 Insertion loss is made up of loss in the tapered loss and is not significantly different with the various length or diameter. Brillouin stoke gain decreases as the diameter increases. Aeff increases causing reduction in nonlinearity. Brillouin stoke increases as the length of the Microfiber increase. Leff increases causing reduction in Pth thus increases nonlinearity. Ge-doped and Ga-doped have stronger Brillouin gain than SMF. But Ga-doped Microfiber has a more stronger response to Brillouin gain than Ge-doped.
- 43. Conclusion and Future Recommendations - Conclusion MMU FORC 17/11/2015 No lasing observed in microfibers because the Brillouin gain is not sufficient to overcome the cavity loss. Brillouin gain shifts to11.1 GHz around the uniform waist. The uniform waist of 2.5 cm shows two different types frequency. Experimental results are similar to the numerical simulation reported in Nature photonics. The 10.85GHz frequency according to the experiment is also found to be 3 times in higher magnitude than the 11.1 GHz.
- 44. Conclusion and Future Recommendations – Future Recommendations MMU FORC 17/11/2015 Ge-doped and Ga-doped fiber show great possibility in nonlinear application due to their better show of performance in generating Brillouin gain. Longer lengths of microfibers may be used for lasing. One other interesting thing to be looked into deeply is the generation of multiple high frequencies in the uniform waist of the Microfibers.
- 45. MMU FORC 17/11/2015 THANK YOU Q & A