[1] [1] Dong P, Chen Y K, Duan G H, et al. Silicon photonic devices and integrated circuits［J］. Nanophotonics, 2014, 3(4-5): 215-228.

[2] [2] Bogaerts W, Chrostowski L. Silicon photonics circuit design: Methods, tools and challenges［J］. Laser & Photonics Review, 2018, 12(4): 1700237.

[3] [3] Soref R A, Schmidtchen J, Petermann K. Large single-mode rib waveguides in GeSi-Si and Si-on-SiO2［J］. IEEE J. of Quantum Electronics, 1991, 27(8): 1971-1974.

[4] [4] Dai D, He S. Analysis of characteristics of bent rib waveguides［J］. J. of the Optical Society of America A, 2004, 21(1): 113-121.

[5] [5] Marchetti R, Lacava C, Khokhar A, et al. High-efficiency grating-couplers: demonstration of a new design strategy［J］. Scientific Reports, 2017, 7(1): 16670.

[6] [6] Hong J, Spring A M, Qiu F, et al. A high efficiency silicon nitride waveguide grating coupler with a multilayer bottom reflector［J］. Scientific Reports, 2019, 9: 12988.

[7] [7] Daniel B, Carlos A R, Diego P G, et al. L-shaped fiber-chip grating couplers with high directionality and low reflectivity fabricated with deep-UV lithography［J］. Opt. Lett.. 2017, 42(17): 3439-3442.

[8] [8] Zou J, Yu Y, Zhang X. Two-dimensional grating coupler with a low polarization dependent loss of 0.25dB covering the C-band［J］. Opt. Lett., 2016, 41(18): 4206-4209.

[9] [9] Rouifed M S, Littlejohns C G, Guo X T, et al. Ultra-compact MMI-based beam splitter demultiplexer for the NIR/MIR wavelengths of 1.55μm and 2μm［J］. Opt. Express, 2017, 25: 10893-10900.

[10] [10] Chen G Y, Ng J D, Lin H L, et al. Design and fabrication of high-performance multimode interferometer in lithium niobate thin film［J］. Opt. Express, 2021, 29: 15689-15698.

[11] [11] Shiran H. Dual-mode broadband compact 2×2 optical power splitter using sub-wavelength metamaterial structures［J］. Opt. Express, 2021, 29: 23864-23876.

[12] [12] Fukuda H, Yamada K, Tsuchizawa T, et al. Silicon photonic circuit with polarization diversity［J］. Opt. Express, 2008, 16(7): 4872-4880.

[13] [13] Hassan S, Chack D, Mahajan V. High extinction ratio and low loss polarization beamsplitter based on multimode interference for PICs［J］. Appl. Opt., 2020, 59(11): 3369-3375.

[14] [14] Bermello A H, Gonzalez J M L, Velasco A, et al. Design of a broadband polarization splitter based on anisotropy-engineered tilted subwavelength gratings［J］. IEEE Photonics J., 2019, 11(3): 1-8.

[15] [15] Wei Y, Yue X, Li Y, et al. A compact and wide-band polarization beam splitter based on wedge-shaped MMI coupler in silicon-on-insulator［C］// 2015 Optical Fiber Communication Conference and Exhibition, 2015, W2A. 12.

[16] [16] Sun X, Aitchison J S, Mojahedi M. Realization of an ultra-compact polarization beam splitter using asymmetric MMI based on silicon nitride/silicon-on-insulator platform［J］. Opt. Express, 2017, 25(7): 8296-8305.

[17] [17] Xu L, Wang Y, Kumar A, et al. Polarization beam splitter based on MMI coupler with SWG birefringence engineering on SOI［J］. IEEE Photon. Technol. Lett., 2018, 30(4): 403-406.

[18] [18] Herrero A, Ponte A D, Luque-Gonzlez J M, et al. Experimental demonstration of metamaterial anisotropy engineering for broadband on-chip polarization beam splitting［J］. Opt. Express, 2020, 28(11): 16385-16393.

[19] [19] Xu L H, Wang Y, El-Fiky E, et al. Compact broadband polarization beam splitter based on multimode interference coupler with internal photonic crystal for the SOI platform［J］. J. of Lightwave Technol., 2019, 37(4): 1231-1240.

[20] [20] Guan X, Wu H, Shi Y, et al. Extremely small polarization beam splitter based on a multimode interference coupler with a silicon hybrid plasmonic waveguide［J］. Opt. Lett., 2014, 39(2): 259-262.

[21] [21] Lin Z, Chen K, Huang Q, et al. Ultra-broadband polarization beam splitter based on cascaded Mach-Zehnder interferometers assisted by effectively anisotropic structures［J］. IEEE Photonics J., 2021, 13(1): 4500209.

[22] [22] Liang T K, Tsang H K. Integrated polarization beam splitter in high index contrast silicon-on-insulator waveguides［J］. IEEE Photon. Technol. Lett., 2005, 17(2): 393-395.

[23] [23] Dai D, Zhi W, Peters J, et al. Compact polarization beam splitter using an asymmetrical Mach-Zehnder interferometer based on silicon-on-insulator waveguides［J］. IEEE Photon. Technol. Lett., 2012, 24(8): 673-675.

[24] [24] Dai D, Zhi W, Bowers J E. Considerations for the design of asymmetrical Mach-Zehnder interferometers used as polarization beam splitters on a submicrometer silicon-on-insulator platform［J］. J. of Lightwave Lett., 2011, 29(12): 1808-1817.

[25] [25] Qiu H, Chen L, Wang Y, et al. Polarization beam splitter based on strong anti-symmetric multimode Bragg gratings［C］// 2017 Asia Communications and Photonics Conf. (ACP). IEEE, 2017: S3D.7.

[26] [26] Zhang Y, He Y, Wu J, et al. High-extinction-ratio silicon polarization beam splitter with tolerance to waveguide width and coupling length variations［J］. Opt. Express, 2016, 24(6): 6586-6593.

[27] [27] Zhan J, Brock J, Veilleux S, et al. Silicon nitride polarization beam splitter based on polarization-independent MMIs and apodized Bragg gratings［J］. Opt. Express, 2021, 29(10): 14476-14485.

[28] [28] Qiu H, Jiang J, Yu P, et al. Broad bandwidth and large fabrication tolerance polarization beam splitter based on multimode anti-symmetric Bragg sidewall gratings［J］. Opt. Lett., 2017, 42(19): 3912-3915.

[29] [29] Wu S B, Zhao Z, Feng T, et al. Compact cross-slot waveguide polarization beam splitter using a sandwich-type coupler［J］. Appl. Opt., 2020, 59(5): 1447-1453.

[30] [30] Li C, Dai D. Compact polarization beam splitter based on a three-waveguide asymmetric coupler with a 340-nm-thick silicon core layer［J］. J. of Lightwave Technol., 2018, 36(11): 2129-2134.

[31] [31] Ma Y Q, Farrell G, Semenova Y, et al. Low loss, high extinction ration and ultra-compact plasmonic polarization beam splitter［J］. IEEE Photonics Technol. Lett., 2014, 26(7): 660-663.

[32] [32] Wu H, Ying T, Dai D. Ultra-broadband high-performance polarizing beam splitter on silicon［J］. Opt. Express, 2017, 25(6): 6069-6075.

[33] [33] Chen W W, Zhang B, Wang P, et al. Ultra-compact and low-loss silicon polarization beam splitter using a particle-swarm-optimized counter-tapered coupler［J］. Opt. Express, 2020, 28(21): 30701-30709.

[34] [34] Dai D X, Wang Z, Bowers J E. Ultrashort broadband polarization beam splitter based on an asymmetrical directional coupler［J］. Opt. Lett., 2011, 36(13): 2590-2592.

[35] [35] Lou F, Dai D, Wosinski L. Ultracompact polarization beam splitter based on a dielectric-hybrid plasmonic-dielectric coupler［J］. Opt. Lett., 2012, 37(16): 3372-3374.

[36] [36] Ong J R, Ang T Y L, Ezgi S, et al. Broadband silicon polarization beam splitter with a high extinction ratio using a triple-bent-waveguide directional coupler［J］. Opt. Lett., 2017, 42(21): 4450-4453.

[37] [37] Kim Y, Hyeok L M, Yudeuk K, et al. High-extinction-ratio directional-coupler-type polarization beam splitter with a bridged silicon wire waveguide［J］. Opt. Lett., 2018, 43(14): 3241-3244.

[38] [38] Yin S J, Qiu H Q, Wang Z B, et al. On-chip silicon switchable polarization beam splitter［J］. Opt. Lett., 2022, 47(4): 961-964.

[39] [39] Huang J, Yang J, Chen D, et al. Ultra-compact broadband polarization beam splitter with strong expansibility［J］. Photonics Research, 2018, 6(6): 574-578.

[40] [40] Shi X D, Zhang J, Fan W, et al. Compact low-birefringence polarization beam splitter using vertical-dual-slot waveguides in silicon carbide integrated platforms［J］. Photonics Research, 2022, 10(1): A8-A13.

[41] [41] Cheng Z, Wang J, Huang Y, et al. Realization of a compact broadband polarization beam splitter using the three-waveguide coupler［J］. IEEE Photon. Technol. Lett., 2019, 31(22): 1807-1810.

[42] [42] Wang J, Liang D, Tang Y, et al. Realization of an ultra-short silicon polarization beam splitter with an asymmetrical bent directional coupler［J］. Opt. Lett., 2013, 38(1): 4-6.

[43] [43] Bhandari B, Im C, Sapkota O R, et al. Highly efficient broadband silicon nitride polarization beam splitter incorporating serially cascaded asymmetric directional couplers［J］. Opt. Lett., 2020, 45(21): 5974-5977.

[44] [44] Zhao N, Qiu C, He Y, et al. Broadband polarization beam splitter by using cascaded tapered bent directional couplers［J］. IEEE Photonics J., 2019, 11(4): 1-8.

[45] [45] Dai D X, Liu X, Liu D. Silicon polarization beam splitter at the 2μm wavelength band by using a bent directional coupler assisted with a nano-slot waveguide［J］. Opt. Express, 2021, 29(2).

[46] [46] Ye T, Qiu J, Chang L, et al. Compact polarization beam splitter with a high extinction ratio over S+C+L band［J］. Opt. Express, 2019, 27(2): 999.

[47] [47] Huang T Y, Xie Y, Wu Y H, et al. Compact polarization beam splitter assisted by subwavelength grating in triple-waveguide directional coupler［J］. Appl. Opt., 2019, 58(9): 2264-2268.

[48] [48] Yang J Y, Dong Y, Xu Y, et al. Broadband and high-extinction-ratio polarization beam splitter on tilted subwavelength gratings waveguides［J］. Appl. Optics, 2020, 59(25): 7705-7711.

[49] [49] Dai S J. Compact and broadband silicon-based polarization beam splitter using asymmetric directional couplers embedded with subwavelength gratings and slots［J］. Appl. Opt., 2022, 61(1): 126-134.

[50] [50] Mao S M, Cheng L, Zhao C, et al. Ultra-broadband and ultra-compact polarization beam splitter based on a tapered subwavelength-grating waveguide and slot waveguide［J］. Opt. Express, 2021, 29(18): 28066-28077.

[51] [51] Zhang J J, Shi X D, Zhang Z J, et al. Ultra-compact, efficient and high-polarization extinction-ratio polarization beam splitters based on photonic anisotropic metamaterials［J］. Opt. Express, 2022, 30(1): 538-549.

[52] [52] Liu L, Deng Q, Zhou Z. Manipulation of bent length and wavelength dependence of a polarization beam splitter using a subwavelength grating［J］. Opt. Lett., 2016, 41(21): 5126-5129.

[53] [53] Xu Y, Xiao J. Compact and high extinction ratio polarization beam splitter using subwavelength grating couplers［J］. Opt. Lett., 2016, 41(4): 773-776.

[54] [54] Li C L, Dai D. Compact polarization beam splitter for silicon photonic integrated circuits with a 340-nm-thick silicon core layer［J］. Opt. Lett., 2017, 42(21): 4243-4246.

[55] [55] Xu H N, Dai D, Shi Y. Ultra-broadband and ultra-compact on-chip silicon polarization beam splitter by using hetero-anisotropic metamaterials［J］. Laser & Photonics Rev., 2019, 13: 1800349.

[56] [56] Li C L, Li C, Zhang M, et al. Ultra-broadband polarization beam splitter with silicon subwavelength-grating waveguides［J］. Opt. Lett., 2020, 45(8): 2259-2262.

[57] [57] Tsuchizawa T, Yamada K, Fukuda H, et al. Microphotonics devices based on silicon microfabrication technology［J］. IEEE J. of Sel. Topics in Quantum Electronics, 2005, 11(1): 232-240.

[58] [58] Ni B, Xiao J B. Ultracompact silicon-based wavelength diplexer for 1.55/2μm using subwavelength gratings［J］. Opt. Lett., 2019, 44(11): 2775-2778.

[59] [59] Lu X H, Wang Y, Mao D, et al. Broadband 1310/1550nm wavelength demultiplexer based on a multimode interference coupler with tapered internal photonic crystal for the silicon-on-insulator platform［J］. Opt. Lett., 2019, 44(7): 1770-1773.

[60] [60] Liu D J, Zhang L, Jiang H, et al. First demonstration of an on-chip quadplexer for passive optical network systems［J］. Photonics Research, 2021, 9(5): 757-763.

[61] [61] Fukuda H, Yamada K, Tsuchizawa T, et al. Silicon photonic circuit with polarization diversity［J］. Opt. Express, 2008, 16(7): 4872-4880.

[62] [62] Uden R G H, Correa R A, Lopez E A, et al. Ultra-high-density spatial division multiplexing with a few-mode multicore fibre［J］. Nature Photonics, 2014, 8: 865-870.

[63] [63] Winzer P J, Peter J. Making spatial multiplexing a reality［J］. Nature Photonics, 2014, 8: 345-348.

[64] [64] Richardson D J, Fini J M, Nelson L E, et al. Space-division multiplexing in optical fibres［J］. Nature Photonics, 2013, 7: 354-362.

[65] [65] Zhao N B, Li X, Li G, et al. Capacity limits of spatially multiplexed freespace communication［J］. Nature Photonics, 2015, 9: 822-826.

[66] [66] Luo L W, Ophir N, Chen C P, et al. WDM-compatible mode-division multiplexing on a silicon chip［J］. Nature Communication, 2013, 5: 3069.

[67] [67] Chen Z Y, Yan L S, Yan P, et al. Use of polarization freedom beyond polarization-division multiplexing to support high-speed and spectral-efficient data transmission［J］. Light Science & Applications, 2017, 6(2): e16207.

[68] [68] Chen S T, Shi Y, He S, et al. Compact monolithically-integrated hybrid (de)multiplexer based on silicon-on-insulator nanowires for PDM-WDM systems［J］. Opt. Express, 2015, 23(10): 12840-12849.

[69] [69] Dai D X, Li C, Wang S, et al. 10-channel mode (de)multiplexer with dual polarizations［J］. Laser & Photonics Rev., 2018, 12: 1700109.