Abstract

We report on the fabrication and experimental demonstration of optical mode size transformation between standard single-mode fiber and 0.26μm-thick Si-waveguide by 12μm-thick Si/SiO2 multilayer on-chip GRIN lens of lengths 16μm or 24μm butt-joint to 10μm-wide terminated Si-waveguide. The overall coupling loss of the coupler was measured to be 3.45dB in which the Fresnel reflection loss is estimated to be 2dB at the GRIN-lens/air interface. The on-chip integrated GRIN lens opens up the feasibility of a low cost passive aligned fiber-pigtailed electronic-photonics integrated circuits platform.

© 2010 OSA

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  1. B. Jalali and S. Fathpour, “Silicon photonics,” J. Lightwave Technol. 24(12), 4600–4615 (2006).
    [CrossRef]
  2. C. Gunn, “CMOS photonics for high-speed interconnects,” IEEE Micro 26(2), 58–66 (2006).
    [CrossRef]
  3. A. Sure, T. Dillon, J. Murakowski, C. Lin, D. Pustai, and D. Prather, “Fabrication and characterization of three-dimensional silicon tapers,” Opt. Express 11(26), 3555–3561 (2003).
    [CrossRef] [PubMed]
  4. V. R. Almeida, R. R. Panepucci, and M. Lipson, “Nanotaper for compact mode conversion,” Opt. Lett. 28(15), 1302–1304 (2003).
    [CrossRef] [PubMed]
  5. T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita, “Low loss mode size converter from 0.3μm square Si wire waveguides to singlemode fibres,” Electron. Lett. 38(25), 1669–1670 (2002).
    [CrossRef]
  6. A. Delâge, S. Janz, B. Lamontagne, A. Bogdanov, D. Dalacu, D.-X. Xu, and K. P. Yap, “Monolithically integrated asymmetric graded and step-index couplers for microphotonic waveguides,” Opt. Express 14(1), 148–161 (2006).
    [CrossRef] [PubMed]
  7. K. Shiraishi and C. S. Tsai, “A micro light-beam spot-size converter using a hemicylindrical GRIN-slab tip with high-index contrast,” J. Lightwave Technol. 23(11), 3821–3826 (2005).
    [CrossRef]
  8. H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
    [CrossRef]
  9. R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
    [CrossRef]
  10. K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C. S. Tsai, “A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers,” Appl. Phys. Lett. 91(14), 141120 (2007).
    [CrossRef]
  11. H. Yoda, K. Shiraishi, A. Ohshima, T. Ishimura, H. Furuhashi, H. Tsuchiya, and C. S. Tsai, “A two-port single-mode fiber-silicon wire waveguide coupler module using spot-size converters,” J. Lightwave Technol. 27(10), 1315–1319 (2009).
    [CrossRef]
  12. Y. Huang and S. T. Ho, “Superhigh numerical aperture (NA > 1.5) micro gradient-index lens based on a dual-material approach,” Opt. Lett. 30(11), 1291–1293 (2005).
    [CrossRef] [PubMed]
  13. Q. Wang, Y. Huang, T.-H. Loh, D. K. T. Ng, and S.-T. Ho, “Thin-film stack based integrated GRIN coupler with aberration-free focusing and super-high NA for efficient fiber-to-nanophotonic-chip coupling,” Opt. Express 18(5), 4574–4589 (2010).
    [CrossRef] [PubMed]
  14. T. H. Loh, Q. Wang, K. T. Ng, and S. T. Ho, “Design and fabrication of multilayer Si/SiO2 super-high N.A. GRIN lens for nano-waveguide to optical fiber coupling,” in Frontiers in Optics, Technical Digest (CD) (Optical Society of America, 2009), paper CThK2. http://www.opticsinfobase.org/abstract.cfm?URI=CLEO-2005-CTuT2
  15. LUMERICAL FDTD SOLUTIONS, http://www.lumerical.com
  16. R. G. Walker, “Simple and accurate loss measurement technique for semiconductor optical waveguide,” Electron. Lett. 21(13), 581–583 (1985).
    [CrossRef]
  17. G. Tittelbach, B. Richter, and W. Karthe, “Comparison of three transmission methods for integrated waveguide propagation loss measurement,” Pure Appl. Opt. 2(6), 683–700 (1993).
    [CrossRef]
  18. Y. A. Vlasov and S. J. McNab, “Losses in single-mode silicon-on-insulator strip waveguides and bends,” Opt. Express 12(8), 1622–1631 (2004).
    [CrossRef] [PubMed]
  19. Q. Wang, T. H. Loh, K. T. Ng, and S. T. Ho, “Design and analysis of optical coupling between silicon nanophotonic waveguide and standard singlemode fiber using an integrated asymmetric Super-GRIN lens,” IEEE J. Sel. Top. Quantum Electron. (to be published).
    [PubMed]

2010 (1)

2009 (1)

2007 (2)

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C. S. Tsai, “A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers,” Appl. Phys. Lett. 91(14), 141120 (2007).
[CrossRef]

2006 (4)

A. Delâge, S. Janz, B. Lamontagne, A. Bogdanov, D. Dalacu, D.-X. Xu, and K. P. Yap, “Monolithically integrated asymmetric graded and step-index couplers for microphotonic waveguides,” Opt. Express 14(1), 148–161 (2006).
[CrossRef] [PubMed]

B. Jalali and S. Fathpour, “Silicon photonics,” J. Lightwave Technol. 24(12), 4600–4615 (2006).
[CrossRef]

C. Gunn, “CMOS photonics for high-speed interconnects,” IEEE Micro 26(2), 58–66 (2006).
[CrossRef]

H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
[CrossRef]

2005 (2)

2004 (1)

2003 (2)

2002 (1)

T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita, “Low loss mode size converter from 0.3μm square Si wire waveguides to singlemode fibres,” Electron. Lett. 38(25), 1669–1670 (2002).
[CrossRef]

1993 (1)

G. Tittelbach, B. Richter, and W. Karthe, “Comparison of three transmission methods for integrated waveguide propagation loss measurement,” Pure Appl. Opt. 2(6), 683–700 (1993).
[CrossRef]

1985 (1)

R. G. Walker, “Simple and accurate loss measurement technique for semiconductor optical waveguide,” Electron. Lett. 21(13), 581–583 (1985).
[CrossRef]

Agarwal, A.

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

Almeida, V. R.

Bogdanov, A.

Dalacu, D.

Delâge, A.

Dillon, T.

Fathpour, S.

Furuhashi, H.

Gunn, C.

C. Gunn, “CMOS photonics for high-speed interconnects,” IEEE Micro 26(2), 58–66 (2006).
[CrossRef]

Ho, S. T.

Y. Huang and S. T. Ho, “Superhigh numerical aperture (NA > 1.5) micro gradient-index lens based on a dual-material approach,” Opt. Lett. 30(11), 1291–1293 (2005).
[CrossRef] [PubMed]

Q. Wang, T. H. Loh, K. T. Ng, and S. T. Ho, “Design and analysis of optical coupling between silicon nanophotonic waveguide and standard singlemode fiber using an integrated asymmetric Super-GRIN lens,” IEEE J. Sel. Top. Quantum Electron. (to be published).
[PubMed]

Ho, S.-T.

Hong, C. Y.

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

Huang, Y.

Ikedo, H.

K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C. S. Tsai, “A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers,” Appl. Phys. Lett. 91(14), 141120 (2007).
[CrossRef]

H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
[CrossRef]

Irie, A.

H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
[CrossRef]

Ishimura, T.

Jalali, B.

Janz, S.

Karthe, W.

G. Tittelbach, B. Richter, and W. Karthe, “Comparison of three transmission methods for integrated waveguide propagation loss measurement,” Pure Appl. Opt. 2(6), 683–700 (1993).
[CrossRef]

Ketsuka, T.

H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
[CrossRef]

Kimerling, L.

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

Lamontagne, B.

Lin, C.

Lipson, M.

Loh, T. H.

Q. Wang, T. H. Loh, K. T. Ng, and S. T. Ho, “Design and analysis of optical coupling between silicon nanophotonic waveguide and standard singlemode fiber using an integrated asymmetric Super-GRIN lens,” IEEE J. Sel. Top. Quantum Electron. (to be published).
[PubMed]

Loh, T.-H.

McNab, S. J.

Michel, J.

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

Morita, H.

T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita, “Low loss mode size converter from 0.3μm square Si wire waveguides to singlemode fibres,” Electron. Lett. 38(25), 1669–1670 (2002).
[CrossRef]

Murakowski, J.

Ng, D. K. T.

Ng, K. T.

Q. Wang, T. H. Loh, K. T. Ng, and S. T. Ho, “Design and analysis of optical coupling between silicon nanophotonic waveguide and standard singlemode fiber using an integrated asymmetric Super-GRIN lens,” IEEE J. Sel. Top. Quantum Electron. (to be published).
[PubMed]

Nguyen, V.

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

Ohshima, A.

H. Yoda, K. Shiraishi, A. Ohshima, T. Ishimura, H. Furuhashi, H. Tsuchiya, and C. S. Tsai, “A two-port single-mode fiber-silicon wire waveguide coupler module using spot-size converters,” J. Lightwave Technol. 27(10), 1315–1319 (2009).
[CrossRef]

K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C. S. Tsai, “A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers,” Appl. Phys. Lett. 91(14), 141120 (2007).
[CrossRef]

Panepucci, R. R.

Prather, D.

Pustai, D.

Richter, B.

G. Tittelbach, B. Richter, and W. Karthe, “Comparison of three transmission methods for integrated waveguide propagation loss measurement,” Pure Appl. Opt. 2(6), 683–700 (1993).
[CrossRef]

Shiraishi, K.

H. Yoda, K. Shiraishi, A. Ohshima, T. Ishimura, H. Furuhashi, H. Tsuchiya, and C. S. Tsai, “A two-port single-mode fiber-silicon wire waveguide coupler module using spot-size converters,” J. Lightwave Technol. 27(10), 1315–1319 (2009).
[CrossRef]

K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C. S. Tsai, “A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers,” Appl. Phys. Lett. 91(14), 141120 (2007).
[CrossRef]

H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
[CrossRef]

K. Shiraishi and C. S. Tsai, “A micro light-beam spot-size converter using a hemicylindrical GRIN-slab tip with high-index contrast,” J. Lightwave Technol. 23(11), 3821–3826 (2005).
[CrossRef]

Shoji, T.

T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita, “Low loss mode size converter from 0.3μm square Si wire waveguides to singlemode fibres,” Electron. Lett. 38(25), 1669–1670 (2002).
[CrossRef]

Sun, R.

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

Sure, A.

Tittelbach, G.

G. Tittelbach, B. Richter, and W. Karthe, “Comparison of three transmission methods for integrated waveguide propagation loss measurement,” Pure Appl. Opt. 2(6), 683–700 (1993).
[CrossRef]

Tsai, C. S.

H. Yoda, K. Shiraishi, A. Ohshima, T. Ishimura, H. Furuhashi, H. Tsuchiya, and C. S. Tsai, “A two-port single-mode fiber-silicon wire waveguide coupler module using spot-size converters,” J. Lightwave Technol. 27(10), 1315–1319 (2009).
[CrossRef]

K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C. S. Tsai, “A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers,” Appl. Phys. Lett. 91(14), 141120 (2007).
[CrossRef]

H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
[CrossRef]

K. Shiraishi and C. S. Tsai, “A micro light-beam spot-size converter using a hemicylindrical GRIN-slab tip with high-index contrast,” J. Lightwave Technol. 23(11), 3821–3826 (2005).
[CrossRef]

Tsuchiya, H.

Tsuchizawa, T.

T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita, “Low loss mode size converter from 0.3μm square Si wire waveguides to singlemode fibres,” Electron. Lett. 38(25), 1669–1670 (2002).
[CrossRef]

Vlasov, Y. A.

Walker, R. G.

R. G. Walker, “Simple and accurate loss measurement technique for semiconductor optical waveguide,” Electron. Lett. 21(13), 581–583 (1985).
[CrossRef]

Wang, Q.

Q. Wang, Y. Huang, T.-H. Loh, D. K. T. Ng, and S.-T. Ho, “Thin-film stack based integrated GRIN coupler with aberration-free focusing and super-high NA for efficient fiber-to-nanophotonic-chip coupling,” Opt. Express 18(5), 4574–4589 (2010).
[CrossRef] [PubMed]

Q. Wang, T. H. Loh, K. T. Ng, and S. T. Ho, “Design and analysis of optical coupling between silicon nanophotonic waveguide and standard singlemode fiber using an integrated asymmetric Super-GRIN lens,” IEEE J. Sel. Top. Quantum Electron. (to be published).
[PubMed]

Watanabe, T.

T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita, “Low loss mode size converter from 0.3μm square Si wire waveguides to singlemode fibres,” Electron. Lett. 38(25), 1669–1670 (2002).
[CrossRef]

Xu, D.-X.

Yamada, K.

T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita, “Low loss mode size converter from 0.3μm square Si wire waveguides to singlemode fibres,” Electron. Lett. 38(25), 1669–1670 (2002).
[CrossRef]

Yap, K. P.

Yasaitis, J.

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

Yoda, H.

H. Yoda, K. Shiraishi, A. Ohshima, T. Ishimura, H. Furuhashi, H. Tsuchiya, and C. S. Tsai, “A two-port single-mode fiber-silicon wire waveguide coupler module using spot-size converters,” J. Lightwave Technol. 27(10), 1315–1319 (2009).
[CrossRef]

K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C. S. Tsai, “A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers,” Appl. Phys. Lett. 91(14), 141120 (2007).
[CrossRef]

H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
[CrossRef]

Appl. Phys. Lett. (2)

R. Sun, V. Nguyen, A. Agarwal, C. Y. Hong, J. Yasaitis, L. Kimerling, and J. Michel, “High performance asymmetric graded index coupler with integrated lens for high index waveguides,” Appl. Phys. Lett. 90(20), 201116 (2007).
[CrossRef]

K. Shiraishi, H. Yoda, A. Ohshima, H. Ikedo, and C. S. Tsai, “A silicon-based spot-size converter between single-mode fibers and Si-wire waveguides using cascaded tapers,” Appl. Phys. Lett. 91(14), 141120 (2007).
[CrossRef]

Electron. Lett. (2)

T. Shoji, T. Tsuchizawa, T. Watanabe, K. Yamada, and H. Morita, “Low loss mode size converter from 0.3μm square Si wire waveguides to singlemode fibres,” Electron. Lett. 38(25), 1669–1670 (2002).
[CrossRef]

R. G. Walker, “Simple and accurate loss measurement technique for semiconductor optical waveguide,” Electron. Lett. 21(13), 581–583 (1985).
[CrossRef]

IEEE J. Sel. Top. Quantum Electron. (1)

Q. Wang, T. H. Loh, K. T. Ng, and S. T. Ho, “Design and analysis of optical coupling between silicon nanophotonic waveguide and standard singlemode fiber using an integrated asymmetric Super-GRIN lens,” IEEE J. Sel. Top. Quantum Electron. (to be published).
[PubMed]

IEEE Micro (1)

C. Gunn, “CMOS photonics for high-speed interconnects,” IEEE Micro 26(2), 58–66 (2006).
[CrossRef]

IEEE Photon. Technol. Lett. (1)

H. Yoda, H. Ikedo, T. Ketsuka, A. Irie, K. Shiraishi, and C. S. Tsai, “A high performance micro-GRIN-chip spot-size converter formed with focused ion-beam,” IEEE Photon. Technol. Lett. 18(14), 1554–1556 (2006).
[CrossRef]

J. Lightwave Technol. (3)

Opt. Express (4)

Opt. Lett. (2)

Pure Appl. Opt. (1)

G. Tittelbach, B. Richter, and W. Karthe, “Comparison of three transmission methods for integrated waveguide propagation loss measurement,” Pure Appl. Opt. 2(6), 683–700 (1993).
[CrossRef]

Other (2)

T. H. Loh, Q. Wang, K. T. Ng, and S. T. Ho, “Design and fabrication of multilayer Si/SiO2 super-high N.A. GRIN lens for nano-waveguide to optical fiber coupling,” in Frontiers in Optics, Technical Digest (CD) (Optical Society of America, 2009), paper CThK2. http://www.opticsinfobase.org/abstract.cfm?URI=CLEO-2005-CTuT2

LUMERICAL FDTD SOLUTIONS, http://www.lumerical.com

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Figures (11)

Fig. 1
Fig. 1

(a) Schematic diagram of the MLS-GRIN lens integrated with Si-waveguide on the PIC. (b) Schematic vertical cross-section of Si waveguide, MLS-GRIN lens, and anti-reflection coating. (c) Ray tracing for evaluating the near-parabolic refractive index profile of the multilayer thin films.

Fig. 2
Fig. 2

(a) The MLS-GRIN lens structure butt-joint to 0.26μm-thick Si waveguide (LGRIN = 19.7μm). (b) Optical power for forward light propagation from Si waveguide through MLS-GRIN lens to air (red arrow indicates direction of propagation). (c) Simulated optical power for backward propagating Gaussian light beam source at the output facet through MLS-GRIN lens and focused into the Si-waveguide. (d) Ey-field plot, (e) Hz-field plot, and (f) Hx-field plot, for backward propagating Gaussian light beam source at the output facet, passing through the MLS-GRIN lens and focusing into the Si-waveguide.

Fig. 6
Fig. 6

(a) through (c) are optical micrographs showing the position of SMF with respect to the MLS-GRIN lens on the PIC chip. SMF is connected to an IR power-meter. (d) shows the dependence of the optical power in the SMF against wavelength of the laser light for SMF positions (a), (b) and (c).

Fig. 3
Fig. 3

(a) through (c) are SEM images of MLS-GRIN lens butt-joint to the tip of the Si waveguide at the edge of the die.

Fig. 4
Fig. 4

Schematic diagram of the DUT which consists of 3μm-wide Si-waveguide, 500μm-long Si up-taper at both ends, with MLS-GRIN lens butt-joint at output end of the waveguide.

Fig. 5
Fig. 5

(a) to (c): Optical mode at termination facets as imaged on IR-camera by discrete lens (30X, NA = 0.4). (a) Optical-mode of 3μm-wide waveguide without MLS-GRIN lens. (b) optical-mode of 3μm-wide waveguide with MLS-GRIN lens. (c) optical-mode of 6μm-wide waveguide with MLS-GRIN lens. (d) and (e): Optical mode imaged by lens (60X, NA = 0.65). (d) optical-mode of 10μm-wide waveguide without MLS-GRIN lens, (e) optical-mode of 10μm-wide waveguide with MLS-GRIN lens (LGRIN = 24µm).

Fig. 7
Fig. 7

(a) The experimental set-up of IR-light coupling from SMF into Si-waveguide through MLS-GRIN lens, with discrete lens objectives imaging the optical mode at the waveguide output. (b) Magnified optical micrograph of IR-light coupling from SMF into Si-waveguide via MLS-GRIN lens situated at the input end. (c) Near field pattern of the optical mode of SMF at 2μW. (d) Near-field pattern of the optical mode at the output end of Si-waveguide. (e) SEM image of the output end-facet of the Si-waveguide.

Fig. 8
Fig. 8

Schematic diagrams of the experimental set-up to obtain: (a) Fabry-Perot spectrum of 3μm-wide Si-waveguide up-tapers to 10μm-termination at both ends, using lensed fiber-probes at input/output for optical coupling, (b) insertion loss spectrum for the DUT, using lensed fiber-probe at the input and SMF coupled to MLS-GRIN lens at the output of the Si-waveguide.

Fig. 9
Fig. 9

Fabry-Perot spectrum of 3μm-wide Si-waveguide up-tapers to 10μm-termination at both ends, using lensed fiber-probes at input/output for optical coupling.

Fig. 10
Fig. 10

Insertion loss against wavelength of 3μm-wide Si-waveguide with 10μm-wide terminations at both ends, and without MLS-GRIN lens (shown at Fig. 8(a)). Optical source is wavelength tunable laser coupled into and out of the waveguide by lensed fiber-probes.

Fig. 11
Fig. 11

Insertion loss against wavelength for the DUT shown at Fig. 8(b), using lensed fiber-probe at the input and SMF coupled to MLS-GRIN lens at the output of the Si-waveguide.

Equations (4)

Equations on this page are rendered with MathJax. Learn more.

L G R I N = h ( n 1 n 2 ) 2 1 ,
L G R I N = j = 1 i 1 h ( n j 2 n i 2 ) 2 1 .
n j 2 = n H 2 T H j + n L 2 T L j T H j + T L j ,
O v e r a l l _ I n s e r t i o n _ L o s s ( FP DUT SMF ) = C o u p l i n g _ L o s s ( FP WG,Left ) + C o u p l i n g _ L o s s ( MLSGRIN SMF,Right ) + Propagation _ L o s s ( WG )

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