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Autofluorescence Spectroscopy of Optical Fibers

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Motivation

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Figure 1: A single dipole inside the planner antenna(simulations layout)

Navid Soltani and Mario Agio, "Planar antenna designs for efficient coupling between a single emitter and an optical fiber," Opt. Express 27, 30830-30841 (2019)

Figure 2: Sample image via microscrope

Figure 3: Sample image via Fiber

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Introduction

3

Fig 4:Jablonski Diagram[1]

  • The optical absorption and emission of impurity ions, e.g. rare earth elements and lead Pb2+.

Fig 5: SiO2 crystal structure in glass materials[2]

Fig 6: Ball and stick model of fused silica in random network[3]

Fig 7: Main Internal parts of fiber[4]

Fig 8: Index profile of step index fiber [5]

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Modal Analysis of Step-index Optical fibers

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U, W are fiber modal parameters

 

 

 

  • LP-mode stands for lineraly polarized mode, which is a combination of TE, TM and HE mode.
  • l represnets the indices which gives the variation of the field in azimuthal direction.

 

 

Fiber Optic Communication Systems. (2007). Fiber Optic Essentials, 100–124. doi:10.1002/9780470152560.ch8 

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5

 

 

 

 

U, W are fiber modal parameters

 

 

 

 

  • Transcendental equations in terms of normalized

parameters:

 

 

Modal Analysis of Step-index Optical fibers

 

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  •  

6

 

 

 

 

​

0

3.817

7.0156

10.1735

Mode

​

​

​

​

 

​

2.4048

5.5201

8.6537

11.7915

Mode

​

​

​

​

 

​

3.8317

7.0156

10.1735

13.3237

Mode

​

​

​

​

Modal Analysis of Step-index Optical fibers

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B-V Curve

Figure 5: B-V curve

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8

 

Modal Shape and Intensity Variation for Different Modes

 

 

 

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Focused Gaussian Beam in Paraxial Approximation

Figure 9: Focused Gaussian Beam in Paraxial Approximation

Novotny, L. (2006). Principles of Nano-Optics. Cambridge: Cambridge University Press.

​

 

  • The field in the focal plane of the objective lens can be expressed as:

 

 

 

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Focused Gaussian Beam in Paraxial Approximation

Figure 10: Intensity profile of focused gaussian beam at focal plane

Novotny, L. (2006). Principles of Nano-Optics. Cambridge: Cambridge University Press.

​

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Overlapping Integral Calculation

 

 

Navid Soltani and Mario Agio, "Planar antenna designs for efficient coupling between a single emitter and an optical fiber," Opt. Express 27, 30830-30841 (2019)

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Experimental Setup

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Operating Wavelength Range and Cut-off of Different Filters

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Fiber Name

Features

λ (nm)

NA

Compositions

UHNA3(Thorlabs)

(Ultra High NA Silica Fiber)[7]

  1. High coupling efficiency to plannar waveguide,
  2. Single mode,
  3. Mode field diameter 3.3µm@1310nm

960nm-1600nm

0.35

Core: SiO2/GeO2

Cladding:(125±1)µm

Coating:(250±20)µm

F-SM1500SC-7/125(Newports)[8]

  1. Single mode,
  2. Bend insensitive,
  3. Mode field diameter 6.7 - 7.6 µm @1550 nm

1550nm

0.170.19

Core: Pure Silicca

Cladding:(125±1)µm

Coating: (245±15)µm

​

F-SM400-SC(Newports)[9]

  1. Single mode,
  2. Mode field diameter 2.7 - 3.3 @ 480nm

405nm-532nm

0.120.14

Core: Pure Silica

Cladding:(125±1)µm

Coating: (245±15)µm

FG050LGA

(Thorlabs)[10]

  1. multimode,
  2. Low-OH

400nm-2400nm

0.22

Core: Pure Silica (50±2%)µm

Cladding: Fluorine-Doped Silica (125±1)µm

Coating: Acrylate (250±4%)µm

SM600[11]

Single mode

633nm-780nm

0.14

Acrylate Coating

Exceptional Core/Clad Concentricity

125 µm Cladding

Feautures,NA and Compositions of different Optical fibers

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Overlapping Integral Value for Different Optical fibers

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Coupling Efficiency of Different Fibers

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Whole Spectrum of Super Continuum Laser

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Whole Spectrum of Super Continuum Laser for Different Fibers

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Raman Shift Calculation

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Figure 11: Raman Scattering diagram

Kim, Y., Jeong, S., Jun, B.-H., Lee, Y.-S., Lee, Y.-S., Jeong, D. H., & Lee, D. S. (2017). Endoscopic imaging using surface-enhanced Raman scattering. European Journal of Nanomedicine, 9(3-4). doi:10.1515/ejnm-2017-0005 

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Fig: Normalized Raman-gain vs Wavenumber plot of Pure Silica Fiber

Table: Raman Shift for different excitation wavelengths of pure silica-core fiber

Raman Shift Calculation

L. Schneebeli, K. Kieu, E. Merzlyak, J. M. Hales, A. DeSimone, J. W. Perry, R. A. Norwood, and N. Peyghambarian, "Measurement of the Raman gain coefficient via inverse Raman scattering," J. Opt. Soc. Am.

 

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Autofluorescence Spectrum of UHNA3

658nm

672nm

715nm

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Autofluorescence Spectrum of F-SM1500SC-7/125

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Autofluorescence Spectrum of F-SM400-SC

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Autofluorescence Spectrum of FG050LGA

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Autofluorescence Spectrum of SM600

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Autofluorescence Spectrum of all Five Fibers at 637nm

Normalized power w.r.t Transmitted Power

Normalized power w.r.t Reflected Power

  • Comparison of Auto-fluorescence power w.r.t Transmitted Power: FG050LGA > UHNA3> SM600> F-SM400SC> F-SM1500SC-7/125
  • Comparison of Auto-fluorescence power w.r.t Reflected Power: FG050LGA > UHNA3 > F-SM1500SC-7/125> SM600 > F-SM400SC

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Autofluorescence Spectrum of all Five Fibers at 650nm

Normalized w.r.t Transmitted Power

Normalized w.r.t Reflected Power

  • Comparison of Auto-fluorescence power w.r.t Transmitted Power: FG050LGA >UHNA3> F-SM400SC> SM600> F-SM1500SC-7/125
  • Comparison of Auto-fluorescence power w.r.t Reflected Power: FG050LGA >UHNA3> F-SM1500SC-7/125> F-SM400SC>SM600

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Autofluorescence Spectrum of all Five Fibers at 690nm

Normalized Plot w.r.t Transmitted Power

Normalized plot w.r.t Reflected Power

  • Comparison of Auto-fluorescence power w.r.t Transmitted Power: UHNA3> FG050LGA > F-SM400SC> SM600> FSM1500SC-7/125
  • Comparison of Auto-fluorescence power w.r.t Reflected Power: F-SM400SC> FG050LGA >UHNA3> F-SM1500SC -7/125>SM600

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Thank You

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Summary

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  • The optical setup has been constructed by using different optical elements. Measurement of Laser intensity, bandwidth of Super Continuum Laser, auto-fluorescence spectrum for different fibers has been done.
  • Overlapping integral of different fibers for different modes has been calculated which leads to find out the coupling efficiency of the optical fibers as a function of wavelength.
  • Analysis of auto-fluorescence spectrum and the comparison has been made between different fibers for different wavelengths.
  • Finally, the analysis of the peak of the auto-fluorescence curve has been done and Raman shift has been calculated for pure silica fibers for different wavelengths of operation.

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References

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[1]. https://en.wikipedia.org/wiki/Jablonski_diagram.

[2]. http://dx.doi.org/10.1109/CSITechnol.2015.7358263

[3]. Korkut Yegin, F. B. (kein Datum). Resonance Fluorescence of Fused Silica by the Depopulation of the Ground State.

[4]. https://www.newport.com/t/fiber-optic-basics

[5]. https://www.fiberoptics4sale.com/blogs/archive-posts/95048070-basic-optics-for-optical-fiber

[6]. https://www.synopsys.com/photonic-solutions/e-news/2017-may.html

[7]. https://www.thorlabs.de/thorproduct.cfm?partnumber=UHNA3

[8]. https://www.newport.com/p/F-SM1500SC-7--125

[9]. https://www.newport.com/p/F-SM400-SC

[10]. https://www.thorlabs.de/thorproduct.cfm?partnumber=FG050LGA

[11]. https://www.thorlabs.de/thorproduct.cfm?partnumber=SM600