2025
- K. Maeda, T. Fujisawa, and M. Arai, “Excitation Intensity and Temperature Dependence of Photoluminescence in Mid-Infrared Region for Lattice-matched InAs/GaAsSb Superlattice Grown by Metalorganic Vapor Phase Epitaxy,” Journal of Materials Science: Materials in Electronics, vol. 36, 122, Jan. 2025, DOI: https://doi.org/10.1007/s10854-024-14142-7.
- T. Fujisawa and Y. Tsuji, “Highly confined out-of-plane corner states in air-hole type topological photonic crystal fiber,” Journal of Optical Society of America B, vol. 42, no. 2, pp. 243-250, Feb. 2025, DOI: https://doi.org/10.1364/JOSAB.544796.
2024
- K., Hombu, K. Hikita, T. Fujisawa, K. Maeda, and M. Arai, “Metalorganic Vapor-Phase Epitaxy Growth of Multilayer Stacked InAsSb/InAsP Superlattices on GaAs and InAs Substrates,” Physica Status Solidi (a), vol.221, pp. 2300824, Feb. 2024.
- K. Nakamura, T. Fujisawa, T. Sato, and K. Saitoh, “Tunable O-band high-tolerance silicon mode multiplexer based on phase-mismatched asymmetric directional couplers,” Journal of the Optical Society of America B, vol. 41, no. 5, pp. 1106-1115, May 2024, DOI: https://doi.org/10.1364/JOSAB.515894.
2023以前
- 藤澤剛, 小柴正則, “3次元非線形光導波路のためのフルベクトル有限要素ビーム伝搬法,” 電子情報通信学会論文誌, vol. J85-C, no. 6, pp. 440-448, June 2002.
- T. Fujisawa and M. Koshiba, “Full-vector finite-element beam propagation method for three-dimensional nonlinear optical waveguides,” IEEE/OSA Journal of Lightwave Technology, vol. 20, no. 10, pp. 1876-1884, Oct. 2002.
- 藤澤剛, 小柴正則, “非線形フォトニック結晶ファイバの波長分散特性,” 電子情報通信学会論文誌, vol. J86-C, no. 1, pp. 72-73, Jan. 2003.
- T. Fujisawa and M. Koshiba, “Finite element characterization of chromatic dispersion in nonlinear holey fibers,” Optics Express, vol. 11, no. 13, pp. 1481-1489 June 2003.
- T. Fujisawa and M. Koshiba, “A frequency-domain finite element method for modeling of nonlinear optical waveguide discontinuities,” IEEE Photonics Technology Letters, vol. 16, no. 1, pp. 129-131, Jan. 2004, DOI: 10.1109/LPT.2003.818924..
- T. Fujisawa and M. Koshiba, “Time-domain beam propagation method for nonlinear optical propagation analysis and its application to photonic crystal circuits,” IEEE/OSA Journal of Lightwave Technology, vol. 22, no. 2, pp. 684-691, Feb. 2004.
- T. Fujisawa and M. Koshiba, “Finite-element mode-solver for nonlinear periodic optical waveguides and its application to photonic crystal circuits,” IEEE/OSA Journal of Lightwave Technology, vol. 23, no. 1, pp. 382-387, Jan. 2005.
- 小松宏一, 藤澤剛, 小柴正則, “チャネル阻止型フォトニック結晶方向性結合器を用いた光双安定素子のスイッチング特性,” 電子情報通信学会論文誌, vol. J88-C, no. 9, pp. 716-723, Sept. 2005.
- S.K. Varshney, T. Fujisawa, K. Saitoh, and M. Koshiba, “Novel design of inherently gain-flattened discrete highly nonlinear photonic crystal fiber Raman amplifier and dispersion compensation using a single pump in C-band,” Optics Express, vol. 13, no. 11, pp. 9516-9526, Nov. 2005.
- T. Fujisawa and M. Koshiba, “Finite-element modeling of nonlinear Mach-Zehnder interferometers based on photonic crystal waveguides for all-optical signal processing,” IEEE/OSA Journal of Lightwave Technology, vol.24, no. 1, pp.617-623, Jan. 2006.
- T. Fujisawa and M. Koshiba, “Polarization-independent optical directional coupler based on slot waveguides,” Optics Letters, vol. 31, no. 1, pp. 56-58, Jan. 2006.
- T. Fujisawa, K. Saitoh, K. Wada, and M. Koshiba, “Chromatic dispersion profile optimization of dual-concentric-core photonic crystal fibers for broadband dispersion compensation,” Optics Express, vol. 14, no. 2, pp. 893-900, Jan. 2006.
- K. Morikawa, T. Fujisawa, K. Saitoh, and M. Koshiba, “Transmission characteristics of laterally illuminated photonic crystal fibers,” IEICE Electronics Express, vol. 3, no. 4, pp. 70-73, Feb. 2006.
- T. Fujisawa and M. Koshiba, “All-optical logic gates based on nonlinear slot waveguide couplers,” Journal of Optical Society of America B, vol. 23, no. 4, pp. 684-691, Apr. 2006.
- S.K. Varshney, T. Fujisawa, K. Saitoh, and M. Koshiba, “Design and analysis of a broadband dispersion compensating photonic crystal fiber Raman amplifier operating in S-band,” Optics Express, vol. 14, no. 8, pp. 3528-3540, Apr. 2006.
- N. Yokoi, T. Fujisawa, K. Saitoh, and M. Koshiba, “Apodized photonic crystal waveguide gratings,” Optics Express, vol. 14, no. 10. pp. 4459-4468, May 2006.
- T. Fujisawa and M. Koshiba, “Theoretical investigation of ultrasmall polarization-insensitive 1´2 multi-mode interference waveguides based on sandwiched structures,” IEEE Photonics Technology Letters, vol. 18, no. 11, pp. 1246-1248, June 2006.
- T. Fujisawa and M. Koshiba, “Analysis of photonic crystal waveguide gratings using coupled-mode theory and finite-element method,” Applied Optics, vol. 45, no. 17, pp. 4114-4121, June 2006.
- T. Fujisawa and M. Koshiba, “Guided modes of nonlinear slot waveguides,” IEEE Photonics Technology Letters, vol. 18, no. 14, pp. 1530-1532, July 2006.
- K. Saitoh, T. Fujisawa, T. Kirihara, and M. Koshiba, “Approximate empirical relations for nonlinear photonic crystal fibers,” Optics Express, vol. 14, no. 14, pp. 6572-6582, July 2006.
- K. Kakihara, N. Kono, K. Saitoh, T. Fujisawa, and M. Koshiba, “Impact of structural deformations on polarization conversion in high index contrast waveguides,” Optics Express, vol. 14, no. 16, pp. 7046-7056, Aug. 2006.
- 桐原誉人, 藤澤剛, 齊藤晋聖, 小柴正則, “非線形フォトニック結晶ファイバの解析的近似理論,” 電子情報通信学会論文誌, vol. J89-C, no. 10, pp. 692-699, Oct. 2006.
- 石川嘉樹, 齊藤晋聖, 藤澤剛, 小柴正則, “空隙を有するリッジ型擬似位相整合第二高調波発生素子の漏れ損失評価,” 電子情報通信学会論文誌, vol. J89-C, no. 10, pp. 700-707, Oct. 2006.
- S.K. Varshney, N.J. Florous, K. Saitoh, M. Koshiba, and T. Fujisawa, “Numerical investigation and optimization of a photonic crystal fiber for simultaneous dispersion compensation over S+C+L wavelength bands,” Optics Communications, vol. 274, no. 1, pp. 74-79, June 2007.
- T. Fujisawa, M. Arai, T. Kakitsuka, T. Yamanaka, Y. Kondo, and H. Yasaka, “Enhanced temperature characteristics of InGaAs/InAlGaAs multi-quantum-well lasers on low-In-content InGaAs ternary substrates,” Applied Physics Express, vol. 1, no. 4, pp. 041203, Apr. 2008.
- T. Sato, M. Mitsuhara, N. Nunoya, T. Fujisawa, K. Kasaya, F. Kano, and Y. Kondo, “2.33-mm-wavelength distributed feedback lasers with InAs-In0.53Ga0.47As multiple-quantum wells on InP substrates,” IEEE Photonics Technology Letters, vol. 20, no. 12, pp. 1045-1047, June 2008.
- (Invited paper) T. Sato, M. Mitsuhara, T. Kakitsuka, T. Fujisawa, and Y. Kondo, “Metalorganic vapor phase epitaxial growth of InAs/InGaAs multiple quantum well structures on InP substrates,” IEEE Journal of Selected Topics in Quantum Electronics, vol. 14, no. 4, pp.992-997, July/August 2008.
- M. Arai, T. Fujisawa, W. Kobayashi, K. Nakashima, M. Yuda, and Y. Kondo, “High-temperature operation of 1.26 mm Fabry-Perot laser with InGaAs metamorphic buffer on GaAs substrate,” IEE Electronics Letters, vol. 44, no. 23, pp. 1359-1360, Nov. 2008.
- M. Arai, W. Kobayashi, T. Fujisawa, M. Yuda, T. Tadokoro, K. Kinoshita, S. Yoda, and Y. Kondo, “10-Gbps direct modulation using a 1.31-mm ridge waveguide laser on an InGaAs ternary substrates,” Applied Physics Express, vol. 2, no. 1, pp. 022101, Jan. 2009.
- M. Arai, T. Tadokoro, T. Fujisawa, W. Kobayashi, K. Nakashima, M. Yuda, and Y. Kondo, “Uncooled (25-85°C) 10 Gbit/s operation of 1.3 mm-range metamorphic Fabry-Perot laser on GaAs substrates,” IEE Electronics Letters, vol. 45, no. 7, pp. 359-360, Mar. 2009.
- M. Arai, K. Nakashima, T. Fujisawa, T. Tadokoro, W. Kobayashi, M. Yuda, and Y. Kondo, “High-temperature operation of 1.26-mm ridge waveguide laser with InGaAs metamorphic buffer on GaAs substrate,” IEEE Journal of Selected Topics in Quantum Electronics, vol. 15, no. 3, pp.724-730, May/June 2009.
- T. Fujisawa, M. Arai, T. Yamanaka, Y. Kondo, and F. Kano, “Microscopic design of GaInNAs quantum well laser diodes on ternary substrates for high-speed and high-temperature operations,” Journal of Applied Physics, vol. 105, no. 11, pp. 113114, June 2009.
- W. Kobayashi, M. Arai, T. Yamanaka, N. Fujiwara, T. Fujisawa, M. Ishikawa, K. Tsuzuki, Y. Shibata, Y. Kondo, and F. Kano, “Wide temperature range (-25°C to 100°C) operation of a 10-Gbit/s, 1.55-mm electroabsorption modulator integrated DFB laser for 80-km SMF transmission,” IEEE Photonics Technology Letters, vol.21, no. 15, pp.1054-1056, Aug. 2009.
- T. Fujisawa, M. Arai, N. Fujiwara, W. Kobayashi, T. Tadokoro, K. Tsuzuki, Y. Akage, R. Iga, T. Yamanaka, and F. Kano, “25-Gbit/s 1.3-mm InGaAlAs-based electroabsorption modulator integrated with a DFB laser for metro-area (40 km) 100-Gbit/s Ethernet system,” IET Electronics Letters, vol.45, no. 17, pp.900-901, Aug. 2009.
- W. Kobayashi, T. Yamanaka, M. Arai, N. Fujiwara, T. Fujisawa, K. Tsuzuki, T. Ito, T. Tadokoro, and F. Kano, “Wide temperature range operation of a 1.55 mm 40-Gb/s electroabsorption modulator integrated DFB laser for very short reach applications,” IEEE Photonics Technology Letters, vol.21, no. 18, pp.1317-1319, Sep. 2009.
- M. Arai, T. Tadokoro, T. Fujisawa, W. Kobayashi, K. Nakashima, M. Yuda, and Y. Kondo, “10-Gb/s direct modulation up to 100°C using 1.3-mm-range metamorphically grown strain compensated InGaAs-GaAs MQW laser on GaAs substrate,” IEEE Photonics Technology Letters, vol.21, no. 18, pp.1344-1346, Sep. 2009.
- T. Fujisawa, T. Sato, M. Mitsuhara, T. Kakitsuka, T. Yamanaka, Y. Kondo, and F. Kano, “Successful application of the 8-band k∙p theory to optical properties of highly strained In(Ga)As/InGaAs quantum wells with strong conduction-valence band coupling,” IEEE Journal of Quantum Electronics, vol. 45, no. 9, pp.1183-1191, Sep. 2009.
- W. Kobayashi, M. Arai, T. Yamanaka, N. Fujiwara, T. Fujisawa, T. Tadokoro, K. Tsuzuki, Y. Kondo, and F. Kano, “Design and fabrication of 10-/40-Gbit/s, uncooled electroabsorption modulator integrated DFB laser with butt-joint structure,” IEEE/OSA Journal of Lightwave Technology, vol. 28, no. 1, pp.164-171, Jan. 2010.
- T. Fujisawa, M. Arai, and F. Kano, “Many-body design of highly strained GaInNAs electroabsorption modulators on GaInAs ternary substrates,” Journal of Applied Physics, vol. 107, pp. 093107, May 2010.
- W. Kobayashi, N. Fujiwara, T. Yamanaka, T. Tadokoro, T. Fujisawa, Y. Shibata, M. Ishikawa, K. Tsuzuki, and F. Kano, “Full C-band 10-Gb/s 40-km SMF transmission of InGaAlAs electroabsorption modulator,” IEEE/OSA Journal of Lightwave Technology, vol. 28, no. 20, pp.3012-3018, Oct. 2010.
- T. Fujisawa, T. Yamanaka, T. Tadokoro, N. Fujiwara, M. Arai, W. Kobayashi, Y. Kawaguchi, K. Tsuzuki, and F. Kano, “Theoretical and experimental investigations of the incident-power-dependent extinction ratio of electroabsorption modulator integrated with DFB laser,” IEEE Journal of Quantum Electronics, vol. 47, no. 1, pp.60-65, Jan. 2011.
- T. Fujisawa, S. Kanazawa, H. Ishii, N. Nunoya, Y. Kawaguchi, A. Ohki, N. Fujiwara, K. Takahata, R. Iga, F. Kano, and H. Oohashi, “1.3-mm, 4×25-Gbit/s, monolithically integrated light source for metro area 100-Gbit/s Ethernet,” IEEE Photonics Technology Letters, vol. 23, no. 6, pp.356-358, Mar. 2011.
- T. Fujisawa, K. Takahata, W. Kobayashi, T. Tadokoro, N. Fujiwara, S. Kanazawa, and F. Kano, “1.3-mm, 50-Gbit/s electroabsorption modulators integrated with a DFB laser for beyond 100G parallel LAN applications,” IET Electronics Letters, vol. 47, no. 12, pp.709-710, June 2011.
- T. Fujisawa, K. Takahata, T. Tadokoro, W. Kobayashi, A. Ohki, N. Fujiwara, S. Kanazawa, T. Yamanaka, and F. Kano, “Long-reach 100Gbit Ethernet light source based on 4×25-Gbit/s 1.3-mm InGaAlAs EADFB lasers,” IEICE Transactions on Electronics, vol. E94-C, no. 7, pp.1167-1172, July 2011.
- (Invited paper) W. Kobayashi, K. Tsuzuki, T. Tadokoro, T. Fujisawa, N. Fujiwara, T. Yamanaka, and F. Kano, “40-Gb/s operation of 1.3/1.55-mm InGaAlAs electroabsorption modulator integrated with DFB laser in compact TO-CAN package,” IEEE Journal of Selected Topics in Quantum Electronics, vol. 17, no. 5, pp.1183-1190, Oct. 2011.
- (Invited paper) S. Kanazawa, T. Fujisawa, A. Ohki, H. Ishii, N. Nunoya, Y. Kawaguchi, N. Fujiwara, K. Takahata, R. Iga, F. Kano, and H. Oohashi, “A compact EADFB laser array module for a future 100-Gbit/s Ethernet transceiver,” IEEE Journal of Selected Topics in Quantum Electronics, vol. 17, no. 5, pp.1191-1197, Oct. 2011.
- T. Fujisawa, T. Kitoh, K. Watanabe, K. Suzuki, M. Kotoku, and H. Takahashi, “Wide-bandwidth, low-waveguide-width-sensitivity InP-based multimode interference coupler designed by wavefront matching method,” IEICE Electronics Express, vol.8, no.24, pp.2100-2105, Dec. 2011.
- T. Fujisawa, S. Kanazawa, K. Takahata, W. Kobayashi, T. Tadokoro, H. Ishii, and F. Kano, “1.3-mm, 4×25G, EADFB laser array module with large-output-power and low-driving-voltage for energy-efficient 100GbE transmitter,” Optics Express, vol.20, no. 1, pp.614-620, Jan. 2012.
- T. Tadokoro, W. Kobayashi, T. Fujisawa, T. Yamanaka, and F. Kano, “43-Gb/s 1.3-mm DFB laser for 40-km transmission,” IEEE/OSA Journal of Lightwave Technology, vol.30, no. 15, pp.2520-2524, Aug. 2012.
- T. Fujisawa, T. Itoh, S. Kanazawa, K. Takahata, Y. Ueda, R. Iga, H. Sanjo, T. Yamanaka, M. Kotoku, and H. Ishii, “Ultracompact, 160-Gbit/s transmitter optical subassembly based on 40-Gbit/s×4 monolithically integrated light source,” Optics Express, vol.21, no. 1, pp.182-189, Jan. 2013.
- T. Fujisawa, S. Kanazawa, W. Kobayashi, K. Takahata, A. Ohki, R. Iga, and H. Ishii, “50-Gbit/s uncooled operation (5~85°C) of 1.3-mm electroabsorption modulator integrated with a DFB laser,” IET Electronics Letters, vol. 49, no. 3, pp.204-205, Jan. 2013.
- S. Kanazawa, T. Fujisawa, N. Nunoya, A. Ohki, K. Takahata, H. Sanjoh, R. Iga, and H. Ishii, “Ultra-compact 100GbE transmitter optical sub-assembly for 40-km SMF transmission,” IEEE/OSA Journal of Lightwave Technology, vol. 31, no. 4, pp.602-608, Feb. 2013.
- W. Kobayashi, T. Ito, T. Yamanaka, T. Fujisawa, Y. Shibata, T. Kurosaki, M. Kotoku, T. Tadokoro, and H. Sanjo, “50-Gb/s direct modulation of 1.3-μm InGaAlAs-based DFB laser with ridge waveguide structure,” IEEE Journal of Selected Topics in Quantum Electronics, vol.19, no.4, pp.1500908, July/Aug. 2013.
- T. Fujisawa, S. Kanazawa, Y. Ueda, W. Kobayashi, K. Takahata, A. Ohki, T. Itoh, M. Kotoku, and H. Ishii, “Low-loss cascaded Mach-Zehnder multiplexer integrated 25-Gbit/s×4-lane EADFB laser array for future CFP4 100GbE transmitter,” IEEE Journal of Quantum Electronics, vol.49, no.12, pp.1001-1007, Dec. 2013.
- T. Ohyama, A. Ohki, K. Takahata, T. Itoh, N. Nunoya, T. Fujisawa, S. Kanazawa, R. Iga, and H. Sanjoh, “Compact 100Gbit/s Ethernet transmitter optical sub-assembly for 40-km transmission using polarization beam combiner,” IEEE Photonics Technology Letters, vol.25, no.24, pp.2416-2418, Dec. 2013.
- W. Kobayashi, T. Fujisawa, K. Tsuzuki, Y. Ohiso, T. Itoh, S. Kanazawa, T. Yamanaka, and H. Sanjoh, “Design and fabrication of wide wavelength range 25.8-Gb/s, 1.3-mm, push-pull-driven DMLs,” IEEE/OSA Journal of Lightwave Technology, vol.32, no.1, pp.3-9, Jan. 2014.
- S. Kanazawa, T. Fujisawa, N. Nunoya,A. Ohki, K. Takahata, H. Sanjoh, R. Iga, and H. Ishii, “Compact flip-chip interconnection 112-Gbit/s EADFB laser array module with high eye-mask margin,” IEEE/OSA Journal of Lightwave Technology, vol.32, no.1, pp.115-121, Jan. 2014.
- W. Kobayashi, T. Fujisawa, S. Kanazawa, and H. Sanjoh, “25 Gbaud/s 4-PAM (50Gb/s) modulation and 10-km SMF transmission with 1.3-mm InGaAlAs-based DML,” IET Electronics Letters, vol.50, no.4, pp.299-300, Feb. 2014.
- S. Kanazawa, T. Fujisawa, A. Ohki, K. Takahata, H. Sanjoh, R. Iga, and H. Ishii, “Compact flip-chip interconnection 8×50-Gb/s EADFB laser array module for 400-Gb/s transceiver,” IET Electronics Letters, vol.50, no.7, pp.533-534, Mar. 2014.
- Y Ueda, T. Fujisawa, K. Takahata, M. Kohtoku, and H. Ishii, “InP-based compact transversal filter for monolithically integrated light source array,” Optics Express, vol.22, no.7, pp.7844-7851, Apr. 2014.
- W. Kobayashi, T. Fujisawa, T. Itoh, S. Kanazawa, Y. Ueda, and H. Sanjoh, “Advantage of EADFB laser for 25 Gbaud/s 4-PAM (50Gb/s) modulation and 10-km SMF transmission,” IET Electronics Letters, vol.50, no.9, pp.683-685, Apr. 2014.
- Y Ueda, T. Fujisawa, S. Kanazawa, W. Kobayashi, K. Takahata, and H. Ishii, “Very-low-voltage operation of Mach-Zehnder interferometer-type electroabsorption modulator using asymmetric couplers,” Optics Express, vol.22, no.12, pp.14610-14616, June 2014.
- T. Sato, S. Makino, Y. Ishizaka, T. Fujisawa, and K. Saitoh, “Three-dimensional finite-element mode-solver for nonlinear periodic optical waveguides and its application to photonic crystal waveguides,” IEEE/OSA Journal of Lightwave Technology, vol.32, no.21, pp.3409-3417, Nov. 2014.
- W. Kobayashi, M. Arai, T. Fujisawa, T. Sato, T. Itoh, K. Hasebe, S. Kanazawa, Y. Ueda, T. Yamanaka, and H. Sanjoh, “Novel approach for chirp and output power compensation of 40-Gbit/s EADFB laser by integrating short SOA,” Optics Express, vol.23, no.7, pp.9533-9542, Apr. 2015, DOI: 10.1364/OE.23.009533.
- T. Ohyama, A. Ohki, K. Takahata, T. Itoh, N. Nunoya, H. Mawatari, T. Fujisawa, S. Kanazawa, R. Iga, and H. Sanjoh, “Transmitter optical sub-assembly using polarization beam combiner for 100Gbit/s Ethernet over 40 km transmission,” IEEE/OSA Journal of Lightwave Technology, vol.33, no.9, pp.1985-1992, May 2015.
- T. Fujisawa, and K. Saitoh, “Material gain analysis of GeSn/SiGeSn quantum wells for mid-infrared Si-based light sources based on many-body theory,” IEEE Journal of Quantum Electronics, vol.51, no.5, pp.7100108, May 2015, DOI: 10.1109/JQE.2015.2410283.
- T. Sato, S. Makino, Y. Ishizaka, T. Fujisawa, and K. Saitoh, “A rigorous definition of nonlinear parameter g and effective area Aeff for photonic crystal optical waveguides,” Journal of Optical Society of America B, vol.32, no.6, pp.1245-1251, June 2015, DOI: 10.1364/JOSAB.32.001245.
- S. Kanazawa, T. Fujisawa, K. Takahata, T. Itoh, Y. Ueda, W. Kobayashi, H. Ishii, and H. Sanjoh, “Flip-chip interconnection lumped-electrode EADFB laser for 100-Gb/s/l transmitter,” IEEE Photonics Technology Letters, vol.27, no.16, pp.1699-1701, Aug. 2015, DOI: 10.1109/LPT.2015.2438076.
- S. Makino, T. Sato, Y. Ishizaka, T. Fujisawa, and K. Saitoh, “Three-dimensional finite-element time-domain beam propagation method and its application to 1-D photonic crystal coupled resonator waveguide,” IEEE/OSA Journal of Lightwave Technology, vol.33, no.18, pp.3836-3842, Sep. 2015, DOI: 10.1109/JLT.2015.2446514.
- W. Kobayashi, S. Kanazawa, Y. Ueda, T. Fujisawa, H. Sanjoh, and M. Itoh, “4×25 Gbit/s (100 Gbit/s) simultaneous operation of InGaAlAs based DML array monolithically integrated with MMI coupler,” IET Electronics Letters, vol.51, no.19, pp.1516-1517, Sep. 2015, DOI: 10.1049/el.2015.1476.
- T. Fujisawa, and K. Saitoh, “Quantum-confined Stark effect analysis of GeSn/SiGeSn quantum wells for mid-infrared Si-based electroabsorption devices based on many-body theory,” IEEE Journal of Quantum Electronics, vol.51, no.11, pp.8400207, Nov. 2015, DOI: 10.1109/JQE.2015.2488363.
- S. Kanazawa, T. Fujisawa, H. Ishii, K. Takahata, Y. Ueda, R. Iga, and H. Sanjoh, “High-speed (400 Gb/s) 8-channel EADFB laser array module using flip-chip interconnection technique,” IEEE Journal of Selected Topics in Quantum Electronics, vol.21, no.6, pp.1501106, Nov./Dec. 2015, DOI: 10.1109/JSTQE.2015.2415197.
- Y. Ueda, T. Fujisawa, S. Kanazawa, W. Kobayashi, K. Takahata, H. Sanjoh, H. Ishii, and M. Kohtoku, “Low-driving-voltage operation of MZI-type EA modulator integrated with DFB laser using optical absorption and interferometric extinction,” IEEE Journal of Selected Topics in Quantum Electronics, vol.21, no.6, pp.1501306, Nov./Dec. 2015, DOI: 10.1109/JSTQE.2015.2420591.
- S. Makino, T. Fujisawa, and K. Saitoh, “Enhancement of optical nonlinearity in coupled resonator optical waveguide based on slotted 1-D photonic crystal cavity,” IEEE Photonics Journal, vol.7, no.6, pp.4501608, Dec. 2015, DOI: 10.1109/JPHOT.2015.2493729.
- T. Sato, S. Makino, T. Fujisawa, and K. Saitoh, “Design of reflection-suppressed all-optical diode based on asymmetric L-shaped nonlinear photonic crystal cavity,” Journal of Optical Society of America B, vol.33, no.1, pp.54-61, Jan. 2016, DOI: 10.1364/JOSAB.33.000054.
- (Invited paper) S. Kanazawa, T. Fujisawa, K. Takahata, Y. Ueda, H. Ishii, R. Iga, W. Kobayashi, and H. Sanjoh, “Flip-chip interconnection technique for beyond 100-Gbit/s EADFB laser array transmitter,” IEEE/OSA Journal of Lightwave Technology, vol.34, no.2, pp.296-302, Jan. 2016, DOI: 10.1109/JLT.2015.2462728.
- T. Fujisawa, and K. Saitoh, “A group delay spread analysis of strongly coupled 3-core fibers: A effect of bending and twisting,” Optics Express, vol.24, no.9, pp.9583-9591, May 2016, DOI: 10.1364/OE.24.009583.
- Y Ueda, T. Fujisawa, and M. Kohtoku, “8-channel Reflection-type Transversal Filter for Compact and Easy-to-Fabricate InP-based Optical Multiplexer,” IEEE/OSA Journal of Lightwave Technology, vol.34, no.11, pp.2684-2691, June 2016, DOI: 10.1109/JLT.2016.2541165.
- S. Nishimoto, T. Fujisawa, Y. Sasaki, H. Uemura, and K. Saitoh, “Theoretical investigation of 6 mode multi/demultiplexer based on fused type multicore fiber coupler,” IEEE Photonics Journal, vol.8, no.3, pp.7802908, June 2016, DOI: 10.1109/JPHOT.2016.2559438.
- S. Kanazawa, W. Kobayashi, Y. Ueda, T. Fujisawa, T. Ohno, T. Yoshimatsu, H. Ishii, and H. Sanjoh, “Low-crosstalk operation of directly modulated DFB laser array TOSA for 112-Gbit/s application,” Optics Express, vol.24, no.12, pp.13555-13562, June 2016, DOI: 10.1364/OE.24.013555.
- S. Kanazawa, W. Kobayashi, Y. Ueda, T. Fujisawa, K. Takahata, T. Ohno, T. Yoshimatsu, H. Ishii, and H. Sanjoh, “30-km error-free transmission of directly modulated DFB laser array transmitter optical sub-assembly for 100-Gbit/s application,” IEEE/OSA Journal of Lightwave Technology, vol.34, no.11, pp.3646-3652, Aug. 2016, DOI: 10.1109/JLT.2016.2520942.
- Y. Ishizaka, M. Nagai, T. Fujisawa, and K. Saitoh, “A photonic-plasmonic mode converter using mode-coupling-based polarization rotation for metal inserted silicon platform,” IEICE Electronics Express, vol.14, no.2, pp.1-10, Jan. 2017, DOI: 10.1587/elex.13.20160989.
- (Invited paper) K. Saitoh, N. Hanzawa, T. Sakamoto, T. Fujisawa, Y. Yamashita, T. Matsui, K. Tsujikawa, and K. Nakajima, “PLC-based mode multi/demultiplexers for mode division multiplexing,” Optical Fiber Technology, vol. 35, pp. 80-92, Feb. 2017, DOI: 10.1016/j.yofte.2016.08.002.
- Y. Ishizaka, S. Makino, T. Fujisawa, and K. Saitoh, “A metal-assisted silicon slot waveguide for highly-sensitive gas detection,” IEEE Photonics Journal, vol.9, no.1, pp. 6800609, Feb. 2017, DOI: 10.1109/JPHOT.2016.2630308.
- Y. Tobita, T. Fujisawa, T. Sakamoto, T. Matsui, S. Saitoh, K. Takenaga, K. Aikawa, S. Aozasa, K. Nakajima, and K. Saitoh, “Optimal design of 4LP-mode multicore fibers for high spatial density,” Optics Express, vol.25, no.5, pp. 5697-5709, Mar. 2017, DOI: 10.1364/OE.25.005697.
- T. Fujisawa, S. Makino, T. Sato, and K. Saitoh, “Low-loss, compact, and fabrication-tolerant Si-wire 90° waveguide bend using clothoid and normal curves for large scale photonic integrated circuits,” Optics Express, vol.25, no.8, pp. 9150-9159, Apr. 2017, DOI: 10.1364/OE.25.009150.
- Y. Yamashita, T. Fujisawa, S. Makino, N. Hanzawa, T. Sakamoto, T. Matsui, K. Tsujikawa, F. Yamamoto, K. Nakajima, and K. Saitoh, “Design and fabrication of broadband PLC-based 2-mode multi/demultiplexer using wavefront matching method,” IEEE/OSA Journal of Lightwave Technology, vol. 35, no. 11, pp. 2252-2258, June 2017, DOI: 10.1109/JLT.2016.2641461.
- T. Fujisawa, and K. Saitoh, “Group delay spread analysis of coupled-multicore fibers: A comparison between weak and tight bending conditions,” Optics Communications, vol.393, pp. 232-237, June 2017, DOI: 10.1016/j.optcom.2017.02.064.
- S. Makino, T. Fujisawa, and K. Saitoh, “Wavefront matching method based on full-vector finite-element beam propagation method for polarization control devices,” IEEE/OSA Journal of Lightwave Technology, vol. 35, no. 14, pp. 2840-2845, July 2017, DOI: 10.1109/JLT.2017.2700482.
- T. Fujisawa, T. Sato, and K. Saitoh, “Full-vector finite-element beam propagation method for helicoidal waveguides and its application to twisted photonic crystal fiber,” IEEE/OSA Journal of Lightwave Technology, vol. 35, no. 14, pp. 2894-2901, July 2017, DOI: 10.1109/JLT.2017.2703889.
- Y. Yamashita, S. Makino, T. Fujisawa, N. Hanzawa, T. Sakamoto, T. Matsui, K. Tsujikawa, F. Yamamoto, K. Nakajima, and K. Saitoh, “PLC-based LP11 mode rotator with curved trench structure devised from WFM method,” IEEE Photonics Technology Letters, vol. 29, no. 13, pp. 1063-1066, July 2017, DOI: 10.1109/LPT.2017.2700496.
- K. Saitoh, T. Fujisawa, and T. Sato, “Coiling size dependence of group delay spread in coupled multicore fibers without intentional twisting,” IEEE/OSA Journal of Lightwave Technology, vol. 35, no. 20, pp. 4559-4566, Oct. 2017, DOI: 10.1109/JLT.2017.2746756.
- T. Fujisawa, Y. Amma, Y. Sasaki, S. Matsuo, K. Aikawa, K. Saitoh, and M. Koshiba, “Crosstalk analysis of heterogeneous multicore fibers using coupled-mode theory,” IEEE Photonics Journal, vol. 9, no.5, pp.7204108, Oct. 2017, DOI:10.1109/JPHOT.2017.2749439.
- T. Sato, T. Fujisawa, and K. Saitoh, “Design of high-forward-transmission all-optical diode based on cascaded side-coupled photonic crystal cavities,” Journal of Optical Society of America B, vol. 34, no.12, pp.2493-2500, Dec. 2017 (selected as Editor’s pick), DOI: 10.1364/JOSAB.34.002493.
- T. Fujisawa, Y. Yamashita, T. Sakamoto, T. Matsui, K. Tsujikawa, K. Nakajima, and K. Saitoh, “Scrambling-type three-mode PLC multiplexer based on cascaded Y-branch waveguide with integrated mode rotator,” IEEE/OSA Journal of Lightwave Technology, vol. 36, no.10, pp.1985-1992, May 2018, DOI: 10.1109/JLT.2018.2798619.
- S. Ohta, T. Fujisawa, S. Makino, T. Sakamoto, T. Matsui, K. Tsujikawa, K. Nakajima, and K. Saitoh, “Si-based Mach-Zehnder wavelength/mode multi/demultiplexer for a WDM/MDM transmission system,” Optics Express, vol.26, no.12, pp. 15211-15220, June 2018, DOI: 10.1364/OE.26.015211.
- (Invited paper) E. Taguchi, T. Fujisawa, Y. Yamashita, S. Makino, N. Hanzawa, T. Sakamoto, T. Matsui, K. Tsujikawa, K. Nakajima, F. Yamamoto, and K. Saitoh, “A review on PLC-based two-mode multi/demultiplexer designed by wavefront matching method,” IEICE Transactions on Electronics, vol. E101-C, no.7, pp. 518-526, July 2018, DOI: 10.1587/transele.E101.C.518.
- S. Nakano, T. Fujisawa, T. Sato, and K. Saitoh, “Beam propagation analysis of optical activity and circular dichroism in helically twisted photonic crystal fiber,” Japanese Journal of Applied Physics, vol. 57, pp. 08PF06 Aug. 2018, DOI: 10.7567/JJAP.57.08PF06.
- Y. Sawada, T. Sato, T. Fujisawa, and K. Saitoh, “Development of the wavefront matching method based on the 3-D finite-element method and its application to Si-wire mode converters,” IEEE/OSA Journal of Lightwave Technology, vol. 36, no.17, pp.3652-3659, Sept. 2018, DOI: 10.1109/JLT.2018.2843383.
- T. Fujisawa, and K. Saitoh, “Off-axis core transmission characteristics of helically twisted photonic crystal fibers,” Optics Letters, vol. 43, no.20, pp.4935-4938, Oct. 2018, DOI: 10.1364/OL.43.004935.
- M. Akie, T. Fujisawa, T. Sato, M. Arai, and K. Saitoh, “GeSn/SiGeSn multiple-quantum-well electroabsorption modulator with taper coupler for mid-infrared Ge-on-Si platform,” IEEE Journal of Selected Topics in Quantum Electronics, vol. 24, no. 6, pp.3400208, Nov./Dec. 2018, DOI: 10.1109/JSTQE.2018.2827673.
- T. Fujisawa, M. Arai, and K. Saitoh, “Microscopic gain analysis of modulation-doped GeSn/SiGeSn quantum wells: Epitaxial design toward high-temperature lasing,” Optics Express, vol. 27, no. 3, pp.2457-2464, Feb. 2019, DOI: 10.1364/OE.27.002457.
- M. Kudo, S. Ohta, E. Taguchi, T. Fujisawa, T. Sakamoto, T. Matsui, K. Tsujikawa, K. Nakajima, and K. Saitoh, “Proposal of Mach-Zehnder mode/wavelength multi/demultiplexer based on Si/Silica hybrid PLC platform,” Optics Communications, vol.433, pp. 168-172, Feb. 2019, DOI: 10.1016/j.optcom.2018.10.004.
- T. Sato, T. Fujisawa, and K. Saitoh, “All-optical diode suppressing broadband backward transmission using single- and four-port photonic crystal cavities,” IEEE Photonics Journal, vol. 11, no.1, pp.4900214, Feb. 2019, DOI: 10.1109/JPHOT.2018.2888632.
- Y. Sawada, T. Fujisawa, T. Sato, and K. Saitoh, “CMOS-compatible Si-wire polarization beam splitter based on wavelength-insensitive coupler,” IEICE Electronics Express, vol. 16, no.8, pp.1-6, Apr. 2019, DOI: 10.1587/elex.16.20181126.
- K. Yoshida, T. Fujisawa, T. Sato, and K. Saitoh, “Optimum index profile of few-mode coupled multicore fibers for reducing the group delay spread,” Optics Express, vol. 27, no. 11, pp.16281-16295, May 2019, DOI: 10.1364/OE.27.016281.
- S. Nakano, T. Fujisawa, and K. Saitoh, “The effect of core offset on the mode converting characteristics in twisted single mode fibers,” IEEE/OSA Journal of Lightwave Technology, vol. 37, no. 21, pp. 5479-5485, Nov. 2019, DOI: 10.1109/JLT.2019.2940692.
- T. Fujisawa, J. Takano, Y. Sawada, T. Sakamoto, T. Matsui, K. Nakajima, and K. Saitoh, “A novel Si four-wavelength multiplexer for 100/400GbE using higher-order mode composed of (a)symmetric directional couplers and TE1-TM0 mode converter,” Optics Express, vol. 27, pp. 36286-36296, Dec. 2019, DOI: 10.1364/OE.27.036286.
- M. Shirata, T. Fujisawa, T. Sakamoto, T. Matsui, K. Nakajima, and K. Saitoh, “A design of small mode-dependent-loss scrambling-type mode (de)multiplexer based on PLC,” Optics Express, vol. 28, pp. 9653-9665, Mar. 2020, DOI: 10.1364/OE.387890.
- T. Fujisawa and K. Saitoh, “Geometric-phase-induced arbitrary polarization and orbital angular momentum generation in helically twisted birefringent photonic crystal fiber,” Photonics Research, vol. 8, no. 8, pp.1278-1288, Aug. 2020, DOI: 10.1364/PRJ.393255.
- Y. Sawada, T. Fujisawa, and K. Saitoh, “Broadband and compact silicon mode converter designed using a wavefront matching method,” Optics Express, vol. 28, no. 25, pp. 38196-38205, Dec. 2020, DOI: https://doi.org/10.1364/OE.411769.
- T. Fujisawa, J. Takano, Y. Sawada, and K. Saitoh, “Low-loss and small 2 × 4λ multiplexers based on 2 × 2 and 2 × 1 Mach-Zehnder interferometers with on-chip polarization multiplexing for 400GbE,” IEEE/OSA Journal of Lightwave Technology, vol. 39, no. 1, pp. 193-200, Jan. 2021, DOI: 10.1109/JLT.2020.3025369.
- K. Nakamura, T. Fujisawa, T. Sakamoto, T. Matsui, K. Nakajima, and K. Saitoh, “Tunable broadband mode dividers based on wavelength insensitive coupler using thermo-optic effect for flexible modal power adjustment in MDM network,” Journal of the Optical Society of America B, vol. 38, no. 3, pp. 946-952, Mar. 2021, DOI: https://doi.org/10.1364/JOSAB.415499.
- T. Fujisawa and K. Saitoh, “Bayesian direct-binary-search algorithm for the efficient design of mosaic-based power splitters,” OSA Continuum, vol. 4, no. 4, pp.1258-1270, Apr. 2021, https://doi.org/10.1364/OSAC.422116.
- K. Nakamura, T. Fujisawa, T. Sato, and K. Saitoh, “High-tolerance CWDM4 wavelength multiplexer based on 2×2/2×1 MZ filters with polarization multiplexing,” IEICE Electronics Express, vol. 18, no. 8, pp. 20210110, Apr. 2021, DOI: 10.1587/elex.18.20210110.
- T. Fujisawa, T. Sakamoto, M. Miyata, T. Matsui, T. Hashimoto, R. Kasahara, T. Mori, R. Imada, K. Nakajima, and K. Saitoh, “Six-mode scrambler based on cascaded side-wall grating waveguides,” Japanese Journal of Applied Physics, vol. 60, pp. 062002, May 2021, DOI: https://doi.org/10.35848/1347-4065/abfa31.
- Y. Sawada, T. Fujisawa, T. Sato, and K. Saitoh, “Broadband silicon four-mode multi/demultiplexer designed by wavefront matching method,” Optics Express, vol. 29, no. 17, pp. 27322-27331, Aug. 2021, DOI: https://doi.org/10.1364/OE.434178.
- T. Fujisawa and K. Saitoh, “Arbitrary polarization and orbital angular momentum generation based on spontaneously broken degeneracy in helically twisted ring-core photonic crystal fiber,” Optics Express, vol. 29, no. 20, pp. 31689-31705, Sep. 2021, DOI: https://doi.org/10.1364/OE.432401.
- Y. Wang, T. Fujisawa, Y. Sagae, T. Sakamoto, T. Matsui, K. Nakajima, and K. Saitoh, “A novel core allocation in heterogeneous step-index multi-core fibers with standard cladding diameter,” IEEE/OSA Journal of Lightwave Technology, vol. 39, no. 22, pp. 7231-7237, Nov. 2021, DOI: 10.1109/JLT.2021.3112656.
- N. Sugawara, T. Fujisawa, K. Nakamura, Y. Sawada, T. Mori, T. Sakamoto, R. Imada, T. Matsui, K. Nakajima, and K. Saitoh, “Modal amplitude and phase estimation of multimode near field patterns based on artificial neural network with the help of grey-wolf-optimizer,” Optical Fiber Technology, vol. 67, pp. 102720, Dec. 2021, DOI: https://doi.org/10.1016/j.yofte.2021.102720.
- Y. Wang, T. Fujisawa, and K. Saitoh, “Analytical expression for mode-coupling coefficient between non-identical step-index cores and its application to multi-core fiber design within 125-μm cladding diameter,” Optics Communications, vol. 506, pp. 127552, Mar. 2022, DOI: https://doi.org/10.1016/j.optcom.2021.127552.
- T. Muratsubaki, T. Fujisawa, Y. Sawada, T. Sato, and K. Saitoh, “Direct-binary-search algorithm for fabrication-tolerant photonic-crystal-like subwavelength structures and its application to a four-mode waveguide crossing in 2-μm waveband,” Japanese Journal of Applied Physics, vol. 61, no. 4, pp. 042003, Apr. 2022, DOI: https://doi.org/10.35848/1347-4065/ac54fc.
- Y. Sawada, T. Fujisawa, T. Sato, and K. Saitoh, “A novel algorithm of wavefront-matching method for stable and efficient design of Si waveguides,” IEEE Photonics Technology Letters, vol. 34, no. 7, pp. 359-362, Apr. 2022, DOI: 10.1109/LPT.2022.3159830
- K. Nakamura, T. Fujisawa, and K. Saitoh, “Hybrid algorithm based on grey wolf optimizer and direct binary search for the efficient design of a mosaic-based device,” Journal of the Optical Society of America B, vol. 39, no. 5, pp. 1329-1337, May 2022, DOI: https://doi.org/10.1364/JOSAB.451593.
- Y. Sawada, T. Fujisawa, T. Sato, and K. Saitoh, “Comparison of scalar and vector WFM method through the design of high-D waveguide lenses,” IEEE Photonics Technology Letters, vol. 34, no. 10, pp. 533-536, May 2022, DOI:10.1109/LPT.2022.3170940.
- T. Fujisawa and K. Saitoh, “Arbitrary higher-order optical spatial state generation by using spontaneously broken degeneracy modes in helically twisted ring-core hole assisted fibers,” Optics Express, vol. 30, no. 14, pp. 24565-24578, July 2022, DOI: https://doi.org/10.1364/OE.463607.
- T. Muratsubaki, T. Fujisawa, T. Sato, and K. Saitoh, “Proposal of mosaic-based 2×2 3-dB couplers for prospective on-chip communication in mid-infrared wavelengths around 2.1 μm,” Journal of the Optical Society of America B, vol. 39, no. 9, pp. 2522-2530, Sept. 2022, DOI:https://doi.org/10.1364/JOSAB.460644.
- H. Wang, T. Fujisawa, T. Sato, T. Mori, T. Sakamoto, Y. Yamashita, R. Imada, K. Nakajima, and K. Saitoh, “6-Mode and 10-Mode photonic lantern mode multi/demultiplexers based on silica planar lightwave circuit,” Optics Communications, vol. 529, pp. 129098, Feb. 2023, DOI: https://doi.org/10.1016/j.optcom.2022.129098.
- T. Sato, K. Homma, T. Fujisawa, Y. Sagae, T. Sakamoto, T. Matsui, K. Nakajima, and K. Saitoh, “Mode converter using bent and twisted coupled-multicore fibers for group delay spread reduction,” Optical Fiber Technology, vol. 77, pp. 103286, May 2023, DOI: https://doi.org/10.1016/j.yofte.2023.103286.
- Z. Zhao, Y. Wang, T. Sato, T. Fujisawa, and K. Saitoh, “Investigation of heterogeneous step-index 2LP-mode multi-core fibers based on two-ring layout with standard cladding diameter,” Optics Continuum, vol. 2, no. 5, pp. 1137-1147, May 2023, DOI: https://doi.org/10.1364/OPTCON.482118.
- T. Sato, T. Fujisawa, M. Wada, T. Mori, T. Sakamoto, R. Imada, T. Matsui, K. Nakajima, and K. Saitoh, “Design of silica-PLC LP11 mode rotator based on adiabatic mode conversion,” Optics Express, vol. 31, no. 15, pp. 23910-23922, July 2023, DOI: https://doi.org/10.1364/OE.493501.
- T. Fujisawa, T. Mitarai, T. Okimoto, N. Kono, N. Fujiwara, T. Sato, H. Yagi, and K. Saitoh, “Bayesian design of mosaic-based mode multiplexers for various wavelength bands,” Optics Express, vol. 31, no. 16, pp. 26842-26853, July 2023, DOI: https://doi.org/10.1364/OE.492673.
- Z. Zhao, Y. Wang, T. Sato, T. Fujisawa, T. Iwaya, Y. Sagae, T. Sakamoto, T. Matsui, K. Nakajima, and K. Saitoh, “Investigation of double-cladding heterogeneous step-index 2LP-mode multi-core fiber with two-ring layout,” Journal of the Optical Society of America B, accepted for publication.
- T. Fujisawa, T. Mitarai, Y. Sawada, T. Okimoto, N. Kono, N. Fujiwara, T. Muratsubaki, H. Yagi, “Ultrasmall power splitters with triangular lattice mosaic patterns designed by Bayesian DBS method,” IEEE Photonics Technology Letters, vol. 35, no. 21, pp. 1139-1142, Nov. 2023, DOI: https://doi.org/10.1109/LPT.2023.3306313.
- T. Mori, T. Fujisawa, J. Sakamoto, Y. Yamashita, T. Sakamoto, R. Imada, R. Ima, T. Sato, K. Watanabe, R. Kasahara, T. Hashimoto, K. Saitoh, and K. Nakajima, “Variable mode-dependent-loss equalizer based on silica-PLC for three-mode transmission,” Optical Fiber Technology, vol. 81, pp. 103547, Dec. 2023, DOI:https://doi.org/10.1016/j.yofte.2023.103547.
- H. Wang, T. Fujisawa, T. Sato, M. Wada, T. Mori, T. Sakamoto, R. Imada, T. Matsui, K. Nakajima, and K. Saitoh, “Design of PLC E31-E13 and E-LP tapered mode converters using fast quasiadiabatic dynamics,” IEICE Electronics Express, vol. 20, no. 23, pp. 20230392, Dec. 2023, DOI:DOI: 10.1587/elex.20.20230392.