A review on fabrication technologies for the monolithic integration of tapers with III-V semiconductor devices

IEEE Journal on Selected Topics in Quantum Electronics

Volumn 3, Issue 6, 1997, Pages 1308-1320

  Moerman, Ingrid ^a,b,c,d,e   Van Daele, Peter P ^a,c,e   Demeester, Piet M ^a,c,e  

^a GHENT UNIVERSITY   (Belgium)

^b University of Gent ^*

^c IMEC   (Belgium)

^d IMEC   (Belgium)

^e IEEE   (Belgium)

Author keywords

III V semiconductors; Mode size converters; Monolithic integration; Optoelectronic integrated circuits

Indexed keywords

DESIGN; ELECTRONICS PACKAGING; INTEGRATED OPTOELECTRONICS; MONOLITHIC INTEGRATED CIRCUITS; PERFORMANCE; WAVEGUIDES;

TAPERS;

OPTOELECTRONIC DEVICES;

EID: 0031363701     PISSN: 1077260X     EISSN: None     Source Type: Journal    
DOI: 10.1109/2944.658785     Document Type: Review

References (81)

1. N. Kalonji and J. Semo, "High efficiency, long working distance laser diode to single mode fiber coupling," Electron. Lett., vol. 30, no. 11, pp. 892-894, 1994.
2. H. M. Presby and C. A. Edwards, "Near 100% efficient fiber microlenses," Electron. Lett., vol. 28, no. 6, pp. 582-584, 1992.
3. Y. Shani, C. H. Henry, R. C. Kistler, K. J. Orlowsky, and D. A. Ackerman, "Efficient coupling of a semiconductor laser to an optical fiber by means of a tapered waveguide on Si," Appl. Phys. Lett., vol. 55, no. 23, pp. 2389-2391, 1989.
4. M. Yanagisawa, H. Terui, Y. Yamada, S. Suzuki, and K. Kato, "Low-loss fiber coupling to laserdiode using 2%-Δ silica-based mode-field converting waveguide," in Tech. Dig. Fourth Microoptics Conf. Eleventh Topical Meet. Gradient-Index Optical Systems, Kawasaki, Japan, 1993, pp. 294-297.
5. J.-M. Cheong, J.-W. Seo, and Y.-K. Jhee, "High alignment tolerance coupling scheme for multichannel laser diode/singlemode fiber modules using a tapered waveguide array," Electron. Lett., vol. 30, no. 18, pp. 1515-1516, 1994.
6. 3-laser)," IEEE J. Quantum Electron., vol. QE-23, no. 6, pp. 712-719, 1987.
7. N. Bouadma, A. Ougazzaden, M. Kamoun, C. Kazmierski, and L. Silvestre, "1.3 μm InGaP/InAsP MQW lasers with large spot size and low loss fiber chip coupling fabricated by a standard buried heterostructure process," Electron. Lett., vol. 32, no. 17, pp. 1582-1583, 1996.
8. M.-H. Shih, F.-S. Choa, R. M. Kapre, W. T. Tsang, R. A. Logan, and S. N. G. Chu, "Alignment-relaxed 1.55 μm multiquantum well lasers fabricated using standard buried heterostructure laser processes," Electron. Lett., vol. 31, no. 13, pp. 1058-1060, 1995.
9. D. Vakhshoori, W. S. Hobson, H. Han, J. Lopata, G. E. Henein, J. D. Wynn, J. de Jong, M. L. Schnoes, and G. J. Zydzik, "980 nm spread index laser with strain compensated InGaAs/GaAsP/InGaP and 90% fiber coupling efficiency," Electron. Lett., vol. 32, no. 11, pp. 1007-1008, 1996.
10. A. Malag and W. Strupinski, "MOVPE-grown (AlGa)As double-barrier multiquantum well (BDMQW) laser diode with low vertical beam divergence," J. Cryst. Growth, vol. 170, pp. 408-412, 1997.
11. I. Moerman, G. Vermeire, M. D'Hondt, W. Vanderbauwhede, J. Blondelle, G. Coudenys, P. Van Daele, and P. Demeester, "III-V semiconductor waveguiding devices using adiabatic tapers," Microelectron. J., vol. 25, pp. 675-690, 1994.
12. G. Müller, B. Stegmüller, H. Westermeier, and G. Wenger, "Tapered In/InGaAsP waveguide structure for efficient fiber-chip coupling," Electron. Lett., vol. 27, no. 20, pp. 1836-1838, 1991.
13. N. Yoshimoto, K. Kawano, H. Takeuchi, S. Kondo, and Y. Noguchi, "Spot size convenors using InP/InAlAs multi quantum well waveguides for low-loss singlemode fiber coupling," Electron. Lett., vol. 28, no. 17, pp. 1610-1611, 1992.
14. R. J. Deri, N. Yasuoka, M. Makiuchi, A. Kuramata, and O. Wada, "Efficient fiber coupling to low-loss diluted multiple quantum well optical waveguides," Appl. Phys. Lett., vol. 55, no. 15, pp. 1495-1497, 1989.
15. K. Kasaya, O. Mitomi, M. Naganuma, Y. Kondo, and Y. Nogushi, "A simple laterally tapered waveguide for low loss coupling to single-mode fibers," IEEE Photon. Technol. Lett., vol. 5, pp. 345-347, Mar. 1993.
16. K. Kasaya, Y. Kondo, M. Okamoto, O. Mitomi, and M. Naganuma, "Monolithically integrated DBR lasers with simple tapered waveguide for low-loss fiber coupling," Electron. Lett., vol. 29, no. 23, pp. 2067-2068, 1993.
17. J. N. Walpole, Z. L. Liau, L. J. Missaggia, and D. Yap, "Diode lasers with cylindrical mirror facets and reduced beam divergence," Appl. Phys. Lett., vol. 50, no. 18, pp 1219-1221, 1987.
18. J. N. Walpole, "Semiconductor amplifiers and lasers with tapered gain regions," Optical and Quantum Electron., vol. 28, pp. 623-645, 1996.
19. G. A. Vawter, R. E. Smith, H. Hou, and J. R. Wendt, "Semiconductor laser with tapered-rib adiabatic-following fiber coupler for expanded output-mode diameter, IEEE Photon. Technol. Lett., vol. 9, pp. 425-427, Apr. 1997.
20. J. G. Bauer, M. Schier, and G. Ebbinghaus, "High responsivity integrated tapered waveguide PIN photodiode," in Proc. 19th Eur. Conf. Optical Communication (ECOC '93), Montreux, Switzerland, pp. 277-280.
21. R. Zengerle, O. Leminger, W. Weiershausen, K. Faltin, and B. Hübner, "Laterally tapered InP-InGaAsP waveguides for low-loss chip-to-fiber butt coupling: A comparison of different configurations," IEEE Photon. Technol. Lett., vol. 7, pp. 532-534, May 1995.
22. Y. Yoshimoto, K. Kawano, Y. Hasumi, T. Takeuchi, S. Kondo, and Y. Noguchi, "InGaAlAs/InAlAs multiple quantum well phase modulator integrated with spot size conversion structure," IEEE Photon. Technol. Lett., vol. 6, pp. 208-210, Feb. 1994.
23. K. Kawano, M. Kohtoku, N. Yoshimoto, S. Sekine, and Y. Noguchi, "2 × 2 InGaAlAs/InAlAs multiquantum well (MQW) directional coupler waveguide switch modules integrated with spot size convenors," Electron. Lett., vol. 30, no. 4, pp. 353-354, 1994.
24. M. Wada, M. Kohtoku, K. Kawano, S. Kondo, Y. Tohmori, Y. Kondo, K. Kishi, Y. Sakai, I. Kotaka, Y. Noguchi, and Y. Itaya, "Laser diodes monolithically integrated with spot-size converters fabricated on 2 inch InP substrates," Electron. Lett., vol. 31, no. 15, pp. 1252-1254, 1995.
25. T. Schwander, S. Fischer, A. Krmer, M. Laich, K. Luksic, G. Spalschek, and M. Warth, "Simple and low-loss fiber-to-chip coupling by integrated field-matching waveguide in InP," Electron. Lett., vol. 29, no. 4, pp. 326-328, 1993.
26. I. Moerman, M. D'Hondt, W. Vanderbauwhede, P. Van Daele, P. Demeester, and W. Hunziker, "InGaAsP/InP strained MQW laser with integrated modesize converter using the shadow masked growth technique," Electron. Lett., vol. 31, pp. 452-454, 1995.
27. T. Brenner and H. Melchior, "Integrated optical modeshape adapters in InGaAsP/InP for efficient fiber-to-waveguide coupling," IEEE Photon. Technol. Lett., vol. 50, pp. 1053-1056, Sept. 1993.
28. T. Brenner, W. Hunziker, M. Smit, M. Bachmann, G. Guekos, and H. Melchior, "Vertical InP/InGaAsP tapers for low-loss optical fiber-waveguide coupling," Electron. Lett., vol. 28, no. 22, pp. 2040-2041, 1992.
29. B. Jacobs, R. Zengerle, K. Faltin, and W. Weiershausen, "Vertically tapered spot size transformers by a simple masking technique," Electron. Lett., vol. 31, no. 10, pp. 794-796, 1995.
30. R. J. Deri, C. Caneau, E. Colas, L. M. Schiavone, N. C. Andreadakis, G. H. Song, and E. C. M. Pennings, "Integrated optic mode-size tapers by selective organometallic chemical vapor deposition of InGaAsP/InP," Appl. Phys. Lett., vol. 61, no. 8, pp. 952-954, 1992.
31. G. Wenger, L. Stoll, B. Weiss, M. Schienle, R. Müller-Nawrath, S. Eichinger, J. Müller, B. Acklin, and G. Müller, "Design and fabrication of monolithic optical spot size transformers (MOST's) for highly efficient fiber-chip coupling," J. Lightwave Technol., vol. 12, pp. 1782-1790, Oct. 1994.
32. N. Shaw, P. J. Williams, J. Buus, "Optoelectronic integrated circuit (OEIC) waveguide coupler for spot size expansion and improved fiber coupling efficiency," Electron. Lett., vol. 31, no. 14, pp. 1143-1145, 1995.
33. S. Nakatsuka, S. Maruo, A. Arimoto, and S. Saitoh, "Laserdiode with controllable spot size ratio of 1:2.1," in Pacific Rim Conf. Lasers and Electro-Optics Tech. Dig., 1995, p. 234, paper FU5.
34. R. Ben-Michael, U. Koren, B. I. Miller, M. G. Young, M. Chien, and G. Raybon, "InP-based multiple quantum well lasers with an integrated tapered beam expander waveguide," IEEE Photon. Technol. Lett., vol. 6, pp. 1412-1414, Dec. 1994.
35. M. Chien, U. Koren, T. L. Koch, B. I. Miller, M. Oron, M. G. Young, and J. L. Demiguel, "Short cavity distributed bragg reflector laser with an integrated tapered output waveguide," IEEE Photon. Technol. Lett., vol. 3, pp. 418-420, May 1991.
36. G. R. Hadley, "Design of tapered waveguides for improved output coupling," IEEE Photon. Technol. Lett., vol. 5, pp. 1068-1070, Sept. 1993.
37. T. L. Koch, U. Koren, G. Eisenstein, M. G. Young, M. Oron, C. R. Giles, and B. I. Miller, "Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers," IEEE Photon. Technol. Lett., vol. 2, pp. 88-90, Feb. 1990.
38. G. Müller, G. Wender, L. Stoll, H. Westermeier, and D. Seeberger, "Fabrication techniques for vertically tapered InP/InGaAsP spot-size transformers with very low loss," in Proc. Eur. Conf. Integrated Optics ECIO 93, Neuchâtel, Switzerland, pp. 14-14.
39. D. E. Bossi, W. D. Goodhue, M. C. Finn, K. Rauschenbach, J. W. Bales, and R. H. Rediker, "Reduced-confinement antennas for GaAlAs integrated optical waveguides," Appl. Phys. Lett., vol. 56, no. 5, pp. 420-422, 1990.
40. D. E. Bossi, W. D. Goodhue, L. M. Johnson, and R. H. Rediker, "Reduced-confinement GaAlAs tapered waveguide antennas for enhanced far-field beam directionality," IEEE J. Quantum Electron., vol. 27, pp. 687-695, Mar. 1991.
41. E. Colas, A. Shahar, and W. J. Tomlinson, "Diffusion-enhanced epitaxial growth of thickness-modulated low-loss rib waveguides on patterned GaAs substrates," Appl. Phys. Lett., vol. 56, no. 10, pp. 955-957, 1990.
42. G. Coudenys, G. Vermeire, Y. Zhu, I. Moerman, L. Buydens, P. Van Daele, and P. Demeester, "Novel growth techniques for the fabrication of photonic integrated circuits," in Proc. Mater. Res. Soc. Symp., 1992, vol. 240, pp. 15-26.
43. Y. Sakai, Y. Tohmori, Y. Suzaki, Y. Kondo, and O. Mitomi, "Improved FFP of 1.3 μm spot-size converted laser for highly efficient coupling to optical fiber," Electron. Lett., vol. 32, no. 15, pp. 1372-1374, 1993.
44. Y. Tohmori, Y. Suzaki, H. Fukano, O. Okamoto, Y. Sakai, O. Mitomi, S. Maisumoto, Y. Yamamoto, M. Fukuda, M. Wada, Y. Itaya, and T. Sugie, "Spot-size converted 1.3 μm laser with butt-jointed selectively grown vertically tapered waveguide," Electron. Lett., vol. 31, no. 3, pp. 1069-1070, 1993.
45. G. Coudenys, I. Moerman, Z. Q. Yu, F. Vermaerke, P. Van Daele, and P. Demeester, "Atmospheric pressure and low pressure shadow masked MOVPE growth of InGaAs(P)/InP and (In)GaAs/(Al)GaAs heterostructures and quantum wells," J. Electron. Mater., vol. 23, no. 2, pp. 227-234, 1994.
46. M. Aoki, M. Komori, M. Suzuki, H. Sato, M. Takahashi, T. Ohtoshi, K. Uomi, and S. Tsuji, "Wide-temperature-range operation of 1.3 μm beam expander-integrated laser diodes grown by in-plane thickness control MOVPE using a silicon shadow mask," IEEE Photon. Technol. Lett., vol. 8, pp. 479-481, Apr. 1996.
47. A. Lorke, J. H. English, A. C. Gossard, and P. M. Petroff, "Tapered GaAs quantum wells and selectively contactable two-dimensional electron gases grown by shadow masked molecular-beam epitaxy," J. Appl. Phys., vol. 77, no. 7, pp. 3578-3580, 1995.
48. I. Moerman, T. Van Caenegem, P. Van Daele, and P. Demeester, "MOVPE-based localized epitaxial growth techniques and its applications," in Proc. Indium Phosphide and Related Materials Conf., Hyannis, MA, May 1997, pp. 610-613, paper ThD1.
49. H. S. Kim, S. Sinha, and R. V. Ramaswamy, "An MQW-SQW tapered waveguide transition," IEEE Photon. Technol. Lett., vol. 5, pp. 1049-1052, Sept. 1993.
50. T. Brenner, R. Hess, and H. Melchior, "Compact InGaAsP/InP laser diodes with integrated mode expander for efficient coupling to flat-ended singlemode fibers," Electron. Lett., vol. 31, no. 17, pp. 1443-1445, 1995.
51. A. Shahar, W. J. Thomlinson, A. Yi-Yan, M. Seto, and R. J. Deri, "Dynamic etch mask technique for fabricating tapered semiconductor optical waveguides and other structures," Appl. Phys. Lett., vol. 56, no. 12, pp. 1098-1100, 1990.
52. U. Koren, R. Ben Michael, B. I. Miller, M. G. Young, M. Chien, H. H. Yaffe, G. Raybon, and K. Dreyer, "Electroabsorption modulator with passive waveguide spot size converters," Electron. Lett., vol. 30, no. 22, pp. 1852-1853, 1994.
53. T. Brenner, M. Bachman, and H. Melchior, "Vertically tapered In-GaAsP/InP waveguides for highly efficient coupling to flat-end single-mode fibers," Appl. Phys. Lett., vol. 65, no. 7, pp. 798-800, 1994.
54. I. Moerman, M. D'Hondt, W. Vanderbauwhede, J. Haes, L. Van Wassenhove, P. De Dobbelaere, R. Baets, P. Van Daele, P. Demeester, W. Hünziker, and C. Holtmann, "Vertically tapered InGaAsP/InP waveguides and lasers resulting in low-loss fiber-chip coupling," in Proc. 20h Eur. Conf. Optical Communication (ECOC '94), Firenze, Italy, 1994, pp. 1027-1030.
55. G. Wenger, G. Müller, B. Sauer, D. Seeberger, and M. Honsberg, "Highly efficient multi-fiber-chip coupling with large alignment tolerances by integrated InGaAsP/InP spot-size transformers," in Proc. 18th Eur. Conf. Optical Communication (ECOC '92), Berlin, Germany, pp. 927-930.
56. L. Möri, C. M. Weinert, F. Reier, L. Stoll, and H. P. Nolting "Uncladded InGaAsP/InP rib waveguides with integrated thickness tapers for efficient fiber-chip butt coupling," Electron. Lett., vol. 32, no. 1, pp. 36-38, 1996.
57. F. Ghirardi, B. Mersali, J. Brandon, G. Herve-Gruyer, and A. Carenco, "Quasi planar Spot-size transformer for efficient coupling between a cleaved fiber and an InP/InGaAsP rib waveguide," IEEE Photon. Technol. Lett., vol. 6, pp. 552-524, Apr. 1994.
58. G. Müller, L. Stall, G. Wenger, and M. Schienle, "First low loss InP/InGaAsP optical switch with integrated mode transformers," in Proc. 19th Eur. Conf. Optical Communication (ECOC '93), Montreux, Switzerland, pp. 37-40.
59. H. Fukano, Y. Kadota, Y. Kondo, M. Ueki, Y. Sakai, K. Kasaya, K. Yokoyama, and Y. Tohmori, "1.3 μm large spot size laser diodes with laterally tapered active layer," Electron. Lett., vol. 31, no. 17, pp. 1439-1440, 1995.
60. P. Doussiere, P. Garabedian, C. Graver, E. Derouin, E. Gaumont-Gaorin, G. Michaud, and R. Meilleur, "Tapered active stripe for 1.5 μm InGaAsP/InP strained multiple quantum well lasers with reduced beam divergence," Appl. Phys. Lett., vol. 64, no. 5, pp. 539-541, 1994.
61. Y. Inaba, M. Kito, T. Nishikawa, M. Ishino, and Y. Matsui, "Multiquantum-well lasers with tapered active stripe for direct coupling to single-mode fiber," IEEE Photon. Technol. Lett., vol. 9, pp. 722-724, June 1997.
62. A. Uda, K. Tsuruka, N. Suzuki, F. Fukushima, T. Nakamura, and T. Torikai, "Spot-size expanded high efficiency 1.3 μm MQW laser diodes with laterally tapered active stripe," in Proc. Indium Phosphide and Related Materials Conf, Hyannis, MA, May 1997, pp. 657-660, paper ThF2.
63. M. Sagawa, K. Hiramoto, T. Toyonaka, T. Kikawa, and K. Uomi, "High-power and highly-reliable operation of 0.98 μm lasers with an exponential-shapes flared stripe," in Proc. 9th Annu. Meet. IEEE Lasers and Electro-Optics Soc., 1996, pp. 42-43, paper ME2.
64. S. H. Grooves, J. P. Donnelly, J. N. Walpole, J. D. Woodhouse, L. J. Missaggia, R. J. Bailey, and A. Napoleone, "Strained-layer InGaAsP diode lasers with tapered gain region for operation λ = 1.3 μm," IEEE Photon. Technol. Lett., vol. 6, pp. 1286-1288, Nov. 1994.
65. E. S. Kintzer, J. N. Walpole, S. R. Chinn, C. A. Wang, and L. J. Missaggia, "High-power, strained layer amplifiers and lasers with tapered gain regions," IEEE Photon. Technol. Lett., vol. 5, pp. 605-608, 1993.
66. H. Sato, M. Aoki, M. Takahashi, M. Komori, K. Uomi, and S. Tsuji, " 1.3 μm beam-expander integrated laser grown by single-step MOVPE," Electron. Lett., vol. 31, no. 15, pp. 1241-1242, 1995.
67. K. Shinoda, K. Hiramoto, M. Sagawa, T. Toyonaka, and K. Uomi, "Circular beam, high power operation of 0.98 μm InGaAs/InGaAsP lasers with a tapered waveguide spot-size expander," Electron. Lett., vol. 32, no. 12, pp. 1101-1102, 1996.
68. R. Zengerle, B. Hübner, C. Gréus, H. Burkhard, H. Janning, and E. Kuphal, "Monolithic integration of spot-size transformer for highly efficient laser fiber coupling," Electron. Lett., vol. 31, no. 14, pp. 1142-1143, 1995.
69. M. Wada, M. Kohtoku, K. Kawano, H. Okamoto, Y. Kadota, Y. Kondo, K. Kishi, S. Kondo, Y. Sakai, I. Kotaka, Y. Noguchi, and Y. Itaya, "High-coupling-efficiency laser diodes integrated with spot-size converters fabricated on 2 inch InP substrates," Electron. Lett., vol. 31, no. 24, pp. 2102-2103, 1995.
70. A. Kasukawa, N. Iwai, N. Yamanaka, and N. Yokouchi, "Output beam characteristics of 1.3 μm GaInAsP/InP SL-QW lasers with narrow and circular output beam," Electron. Lett., vol. 31, no. 7, pp. 559-560, 1995.
71. I. F. Lealman, L. J. Rivers, M. J. Harlow, S. D. Perrin, and M. J. Robertson, "1.56 μm InGaAsP/InP tapered active layer multiquantum well laser with improved coupling to cleaved single mode fiber," Electron. Lett., vol. 30, no. 11, pp. 857-859, 1994.
72. I. F. Lealman, L. J. Rivers, M. J. Harlow, and S. D. Perrin, "InGaAsP/InP tapered active layer multiquantum well laser with 1.8 dB coupling loss to cleaved singlemode liber," Electron. Lett., vol. 30, no. 20, pp. 1685-1687, 1994.
73. I. F. Lealman, B. M. Macdonald, J. V. Collins, P. J. Fiddyment, C. A. Jones, R. G. Waller, M. J. Robertson, L. J. Rivers, C. M. Peed, K. Cooper, S. D. Perrin, M. W. Niel, and M. J. Harlow, "Tapered active laserdevice performance and its impact on low cost optoelectronics," in Proc. 8th Annu. Meet. IEEE Lasers and Electro-Optics Soc., 1995, pp. 11-12, paper MEMGW 2.2.
74. R. Y. Fang, D. Bertoni, M. Meliga, I. Montrasset, G. Olivetti, and R. Paoletti, "Low-cost 1.55 μm InGaAsP-InP spot size converted (SSC) laser with conventional active layers," IEEE Photon. Technol. Lett., vol. 9, pp. 1084-1086, Aug. 1997.
75. Y. Tohmori, Y. Suzaki, H. Oohashi, Y. Sakai, Y. Kondo, H. Okamoto, Y. Kadota, O. Mitomi, Y. Itaya, and T. Sugie, "High temperature operation with low-loss coupling to fiber for narrow-beam 1.3 μm lasers with butt-jointed selective grown spot-size converters," Electron. Lett., vol. 31, no. 21, pp. 1838-1839, 1995.
76. M. Muramaki, "Mitsubishi Laser diode achieves 11° spread angle," Semiconduct. Int., Dec. 1995, pp. 48.
77. A. Kasukawa, N. Yamanaka, N. Iwai, Y. Nakahira, and N. Yokouchi, "Structural dependence of 1.3 μm narrow beam lasers fabricated by selective MOCVD," Electron. Lett., vol. 32, no. 14, pp. 1304-1305, 1996.
78. H. Soda, H. Kobayashi, T. Yamamoto, M. Ekawa, and S. Yamazaki, "Tapered thickness waveguide InGaAsP/InP BH MQW lasers," in Proc. 8th Annu. Meet. IEEE Lasers and Electro-Optics Soc., 1995, p. 13, paper EMGW2.3.
79. L. N. Langley, D. J. Robbins, P. J. Williams, T. J. Reid, I. Moerman, X. Zhang, P. Van Daele, and P. Demeester, "DFB laser with integrated waveguide taper grown by shadow masked MOVPE," Electron. Lett., vol. 32, no. 8, pp. 738-739, 1996.
80. G. Vermeire, F. Vermaerke, I. Moerman, J. Haes, R. Baets, P. Van Daele, and P. Demeester, "Monolithic integration of a SQW laser diode and a mode-size converter using shadow masked MOVPE growth," J. Cryst. Growth, vol. 145, pp. 875-880, 1994.
81. K. Kawano, M. Kohtoku, H. Okamoto, Y. Itaya, and M. Naganuma, "Comparison of coupling characteristics for several spot size-converter-integrated laser diodes in the 1.3 μm wavelength region," IEEE Photon. Technol. Lett., vol. 9, pp. 428-430, Apr. 1997.