Broadband Polarization Beam Splitter Research Articles

Ultra-compact broadband polarizing beam splitter using tilted nano-gratings based bridge waveguide

Ultra-compact broadband polarizing beam splitter using tilted nano-gratings based bridge waveguide

Compact and broadband polarization beam splitter based on a bridged hybrid plasmonic waveguide coupler on a thin-film lithium niobate.

We propose a compact and broadband polarization beam splitter (PBS) based on a thin-film lithium niobate. The hybrid plasmonic waveguide (HPW) is used as a bridge in a three-waveguide coupler to achieve large birefringence. A degree of phase-matching is introduced for optimization. The proposed PBS exhibits a 125-nm bandwidth (1495-1620 nm) of polarization extinction ratio (PER) over 20 dB or an 85-nm bandwidth (1515-1600 nm) of PER over 25 dB, with a device length of only 81 μm. An ultra-low insertion loss of 0.04 dB is achieved around the wavelength of 1550 nm. In addition, the proposed device exhibits high robustness of the fabrication tolerance.

Inverse design of highly-efficient and broadband polarization beam splitter on SOI platform

Polarization beam splitters (PBSs) are essential components in integrated optics, particularly for applications demanding high polarization purity. However, most existing PBS designs rely on complex forward design methods, often constrained by large size and limited performance. In this study, we introduce an inverse design approach based on shape optimization to develop a high-performance PBS on the silicon-on-insulator (SOI) platform. By optimizing the boundary shape, the proposed PBS exhibits low insertion loss (<1.4 dB) and high extinction ratio (>9.2 dB) across a bandwidth range of 65 nm (1500 nm–1565 nm), as confirmed by experimental results. The footprint of the device measures 1.7 × 16 μm2, and the entire structure can be fabricated through a single lithography step. This work holds great promise for the convenient and efficient design of on-chip PBSs.

Design and analysis of a compact and broadband polarization beam splitter on silicon nitride on silicon-on-insulator multilayer platform using a partially overlapped vertical asymmetrical directional coupler

Design and analysis of a compact and broadband polarization beam splitter on silicon nitride on silicon-on-insulator multilayer platform using a partially overlapped vertical asymmetrical directional coupler

Broadband free space 2 × 4 90° optical hybrid for satellite laser communication.

We design a broadband free space 2×4 90° optical hybrid over a spectral window of 1000-1200nm and 1470-1650nm and verify the feasibility of the scheme experimentally. The hybrid consists of three broadband polarization beam splitters, an achromatic λ/4 wave plate, and three achromatic λ/2 wave plates. The fabricated hybrid exhibits a good quadrature phase response with an interchannel imbalance of 0.93-1.07 and a low phase deviation of less than 0.2° under the typical communication wavelengths of 1064nm and C-band. The experimental results of the heterodyne method show that the proposed hybrid can effectively solve the wavelength incompatibility problem in satellite laser communication and realize interconnection at different wavelengths. The designed hybrid (without coupling) has a measured insertion loss of no more than 7.34dB at 1064nm and C-band. A high-speed transmission experiment with BPSK format has been conducted to verify the performance of the assembled device.

Broadband Polarization Beam Splitter Based on Silicon Dual-Core Photonic Crystal Fiber with Gold Layers Operating in Mid-Infrared Band

Broadband Polarization Beam Splitter Based on Silicon Dual-Core Photonic Crystal Fiber with Gold Layers Operating in Mid-Infrared Band

Ultra-compact, broadband polarization beam splitter based on x-cut lithium-niobate-on-insulator platform using hybrid plasmonic waveguide

We propose an ultra-compact, high-performance polarization beam splitter (PBS) on the x-cut lithium-niobate-on-insulator (LNOI) platform. The device based on asymmetrical directional coupler (ADC) consists of a single-mode waveguide (SMW) and a hybrid plasmonic waveguide (HPW). Whole length of the device is only 47 μm, which is the shortest PBS on the x-cut LNOI platform due to polarization-dependent characteristic of plasmonics. When choosing proper width of coupling waveguides (WGs), the phase-matching condition can be satisfied in TE polarization while phase-mismatching exists in TM polarization at the same time. Simulation result shows that bandwidth of the device can achieve at least 200 nm with −10 dB extinction for TE polarization and at least 200 nm with less than −20 dB extinction for TM polarization, which successfully covers entire C-band and L-band. Additionally, the device exhibits large fabrication tolerance and easily fabricated characteristic.

Broadband, compact and reflection-less silicon polarizer and polarization beam splitter using chirped anti-symmetric multimode nanobeams.

We present chirped anti-symmetric multimode nanobeams (CAMNs) based on silicon-on-insulator platforms, and describe their applications as broadband, compact, reflection-less, and fabrication-tolerant TM-pass polarizers and polarization beam splitters (PBSs). The anti-symmetric structural perturbations of a CAMN ensure that only contradirectional coupling between symmetric and anti-symmetric modes is possible, which can be exploited to block the unwanted back reflection of the device. The new possibility of introducing a large chirp on an ultra-short nanobeam-based device to overcome the operation bandwidth limitation due to the coupling coefficient saturation effect is also shown. The simulation results show that an ultra-compact CAMN with a length of ∼4.68 um can be used to develop a TM-pass polarizer or a PBS with an ultra-broad 20 dB extinction ratio (ER) bandwidth of >300 nm and an average insertion loss of <1.3 dB. The CAMN-based polarizer and PBS were fabricated and experimentally characterized in a wavelength range from 1507 to 1575 nm. The measured ERs were >20 dB over the entire tested wavelength range and the average insertion losses were <0.5 dB for both devices. The mean reflection suppression ratio of the polarizer was ∼26.4 dB. Large fabrication tolerances of ±60 nm in the waveguide widths of the devices were also demonstrated.

Compact and broadband polarization beam splitter on lithium-niobate-on-insulator using a hybrid plasmonic waveguide

A compact and broadband polarization beam splitter (PBS) is proposed based on an asymmetric directional coupler consisting of a hybrid plasmonic waveguide and a ridge waveguide on lithium-niobate-on-insulator. Due to the surface plasma polariton (SPP) effect, the phase-matching condition is satisfied for transverse electric polarization, whereas the transverse magnetic polarization has a significant phase mismatch by choosing reasonable widths of both waveguides. A short ( ∼ 28 μm long) PBS is designed while the gap width is chosen to be 200 nm to make it easy to fabricate. Numerical simulations show that the designed PBS has a broad bandwidth (>130 nm) for an extinction ratio of >15 dB and a large fabrication tolerance for the variation of the waveguide width (over ± 50 nm).

Broadband and CMOS-compatible polarization splitter and rotator built on a silicon nitride-on-silicon multilayer platform.

A broadband and CMOS-compatible polarization beam splitter and rotator (PSR) built on the silicon nitride-on-silicon multilayer platform is presented. The PSR is realized by cascading a polarization beam splitter and a polarization rotator, which are both subtly constructed with an asymmetrical directional coupler waveguide structure. The advantage of this device is that the function of PSR can be directly realized in the SiN layer, providing a promising solution to the polarization diversity schemes in SiN photonic circuits. The chip is expected to have high power handling capability as the light is input from the SiN waveguide. The use of silicon dioxide as the upper cladding of the device ensures its compatibility with the metal back-end-of-line process. By optimizing the structure parameters, a polarization conversion loss lower than 1dB and cross talk larger than 27.6dB can be obtained for TM-TE mode conversion over a wavelength range of 1450 to 1600nm. For TE mode, the insertion loss is lower than 0.26dB and cross talk is larger than 25.3dB over the same wavelength range. The proposed device has good potential in diversifying the functionalities of the multilayer photonic chip with high integration density.

Compact and broadband on-chip silicon polarization beam splitter based on tilted subwavelength grating

Efficient polarization management is a key issue for on-chip silicon photonic integrated circuits. Here, we propose a compact and broadband on-chip silicon polarization beam splitter (PBS) using tilted subwavelength grating (SWG) structure. The key polarization separation region consists of an input tapered SWG, a titled SWG, and two output tapered SWGs at both output ports. The tilted SWG has a strong polarization dependence for the mode coupling, and we have introduced different grating duty cycles, positional offset, and a new, to the best of our knowledge, output mode transition structure to enhance the device performance. Based on these techniques, the key coupling length of the proposed PBS is only 5 µm (total length, 12 µm), together with polarization extinction ratio (ER) 21.2 dB (19.7 dB) and insertion loss 0.21 dB (0.39 dB) for the TE (TM) mode. Moreover, the device working bandwidth can be extended to 311 nm (154 nm) by keeping E R &gt; 15 d B ( E R &gt; 18 d B ), satisfying the on-chip broadband applications. We believe the proposed device could become a good candidate to boost the on-chip polarization management toward compact and broadband directions.

Near-infrared broadband polarization beam splitter with an Au nanocube array

A near-infrared broadband polarization beam splitter (PBS) is proposed and numerically simulated, which is realized by a directional coupler assisted with an Au nanocube array. The fundamental transverse electric (TE) mode can be coupled to the output of the upper waveguide by exciting the surface plasmon polaritons (SPPs), while the fundamental transverse magnetic (TM) mode is output directly from the lower waveguide. The length of the coupling region of the PBS is only 1 μm. It has a working bandwidth of 210 nm in the range of 1420 ∼ 1630 nm, covering three bands: S-, C- and L-bands. The simulation shows that the extinction ratio of TE and TM polarization is 20.31 dB and 14.15 dB, respectively.

Design of Compact and Broadband Polarization Beam Splitters Based on Surface Plasmonic Resonance in Photonic Crystal Fibers.

In this work, a polarization beam splitter (PBS) based on surface plasmonic resonance is proposed and realized in a designed photonic crystal fiber (PCF). The PCF consists of two kinds of air holes with different diameters. Two solid silica cores near the center of the PCF are established by removing the cladding air holes. A gold film is plated at the external surface of the central air hole of the PCF to excite the surface plasmonic resonance. In order to minimize the length and improve the operation bandwidth of the PBS, the influences of the transversal structural parameters of the PCF are investigated in the context of both X and Y polarization beams. It was found that a 123.6-m-long PBS with an operation bandwidth of 314 nm could be realized after the global optimization of five structural parameters. The proposed PBS may have potential applications in micro-/nano-optical systems for sensing and communications.

HYPHa project: a low-cost alternative for integrated photonics

In this paper, a brief introduction to the Hybrid sensor platforms of integrated photonic systems based on ceramic and polymer materials (HYPHa) is presented. The project's goal is to establish a collaborative effort of institutes specialized in integrated optics. The newly formed group of professionals will be founded on research groups' experience, collaboration, and devotion. We intend to develop a method for combining competencies and a universal material platform for integrated photonics, based on newly validated hybrid materials as part of the project. Silica compounds with additions including TiO2, SnO2, used as structural matrices, polymer coatings with dopants (active or protective layers), organic dyes, and active two-dimensional materials such as transition metal dichalcogenides, graphene hybrids, and boron nitride will be the foundation for these materials. Full Text: PDF ReferencesK. Rola, A. Zajac, M. Czajkowski, A. Szpecht, M. Zdonczyk, M. Smiglak, J. Cybinska, K. Komorowska, "Ionic liquids for active photonics components fabrication", Opt. Mater. 89, 106-111 (2019). CrossRef D. Kowal, K. Rola, J. Cybinska, M. Skorenski, A. Zajac, A. Szpecht, M. Smiglak, S. Drobczynski, K. Ciesiolkiewicz, K. Komorowska, "Fluorescent ionic liquid micro reservoirs fabricated by dual-step E-beam patterning", Mater. Res. Bull. 142, 111434 (2021). CrossRef T. Martynkien, J. Olszewski, M. Szpulak, G. Golojuch, W. Urbanczyk, T. Nasilowski, F. Berghmans, and H. Thienpont, "Experimental investigations of bending loss oscillations in large mode area photonic crystal fibers", Opt. Express 15, 13547-13556 (2007). CrossRef E. Środa, J. Olszewski, and W. Urbańczyk, "Reducing bend-induced loss and crosstalk in a two-mode ridge waveguide by steplike thickness structuring", Appl. Opt. 61, 1164-1170 (2022). CrossRef P. Karasinski, C. Tyszkiewicz, A. Domanowska, A. Michalewicz, J. Mazur, "Low loss, long time stable sol–gel derived silica–titania waveguide films", Mater. Lett. 143, 5-7 (2015). CrossRef P. Karasinski, C. Tyszkiewicz, A. Maciaga, I.V. Kityk, E. Gondek, "Two-component waveguide SiO2:TiO2 films fabricated by sol–gel technology for optoelectronic applications", J. of Mater. Sci.: Mater. Electron. 26, 2733-2736 (2015). CrossRef M.A. Butt, A. Kazmierczak, C. Tyszkiewicz, P. Karasinski, R. Piramidowicz, "Mode Sensitivity Exploration of Silica–Titania Waveguide for Refractive Index Sensing Applications", Sensors 21, 7452 (2021). CrossRef A. Kazmierczak, M. Slowikowski, K. Pavlov, M. Filipiak, M. Vervaeke, C. Tyszkiewicz, H. Ottevaere, R. Piramidowicz, P. Karasinski, "Efficient, low-cost optical coupling mechanism for TiO2-SiO2 sol-gel derived slab waveguide surface grating coupler sensors", Opt. Appl. 50, 539 (2020). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazanskiy, "A highly sensitive design of subwavelength grating double-slot waveguide microring resonator", Laser Phys. Lett. 17, 076201 (2020). CrossRef N.L. Kazanskiy, M.A. Butt, S.N. Khonina, "Silicon photonic devices realized on refractive index engineered subwavelength grating waveguides-A review", Opt. Laser Technol. 138, 106863 (2021). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazanskiy, "Recent advances in photonic crystal optical devices: A review", Opt. Laser Technol. 142, 107265 (2021). CrossRef L. Xu, Y. Wang, E. El-Fiky, D. Mao, A. Kumar, Z. Xing, Md. G. Saber, M. Jacques, D.V. Plant, "Compact Broadband Polarization Beam Splitter Based on Multimode Interference Coupler With Internal Photonic Crystal for the SOI Platform", J. Light. Technol. 37, 1231 (2019). CrossRef R. Marchetti, C. Lacava, A. Khokhar, X. Chen, I. Cristiani, D.J. Richardson, G. T. Reed, P. Petropoulos, P. Minzioni, "High-efficiency grating-couplers: demonstration of a new design strategy", Sci. Rep. 7, 16670 (2017). CrossRef

Broadband tunable electro-optic switch/power divider as potential building blocks in integrated lithium niobate photonics.

We demonstrate an electro-optic (EO) switch or in general, an EO controllable power divider based on a periodically poled lithium niobate (PPLN) polarization mode converter (PMC) and a five-waveguide adiabatic coupler integrated on a Ti:LN photonic circuit chip. In this integrated photonic circuit (IPC) device, the PPLN works as an EO controllable polarization rotator (and therefore a PMC), while the adiabatic coupler functions as a broadband polarization beam splitter (PBS). The 1-cm long PPLN EO PMC of the IPC device is characterized to have a half-wave (or switching) voltage of Vπ∼20 V and a conversion bandwidth of ∼2.6 nm. The splitting ratios of the adiabatic coupler PBS in the IPC device are >99% for both polarization modes over a broad spectral range from 1500-1640 nm. The EO mode of the implemented IPC device is activated when the PPLN EO PMC section is driven by an external voltage; the characterized EO switching/power division behavior of the device is in good agreement with the theoretical fit. The tunability of the EO IPC device in the 100-nm experimental spectral range is also demonstrated via the temperature tuning. The featured broad tunability and high integrability of the EO device presented in this study facilitates it to be an advantageous building block for realizing an on-chip photonic system.

High extinction ratio and broadband polarization beam splitter based on bricked subwavelength gratings on SOI platform

A compact asymmetrical directional coupler (ADC) based on coupling between a conventional subwavelength grating (SWG) and a bricked subwavelength grating (BSWG) is proposed to realize broadband polarization beam splitter (PBS) with high extinction ratio (ER) on silicon-on-insulator (SOI) platform. Apart from conventional SWG structural parameters (duty cycle and period), the BSWG is utilized to provide a new design space to control TE and TM modal effective index for accurate phase match. Accordingly, as to the TM mode, it is possible to satisfy phase-matching condition and then can be coupled more efficiently with higher ER by introducing the BSWG. Meanwhile, there is a significant phase mismatch for the TE mode. In this way, the proposed PBS that separates TE and TM mode to the through and cross ports can be realized. Simulation results show that the proposed PBS with a compact coupling length of 8.4 μm can achieve a high ER of 35.06 dB and an insertion loss of 0.25 dB for the TM mode at 1.55 μm, while the ER is 18.92 dB and insertion loss is 0.01 dB for the TE mode. Moreover, the operating bandwidth is up to 300 nm (1400∼1700 nm) for the TE mode and 155 nm (1487∼1642 nm) for the TM mode when the ER is >15 dB.

Design of broadband and compact mid-infrared polarization beam splitter based on all-circular air holes with low loss

A mid-infrared (mid-IR) broadband polarization beam splitter (PBS) based on a gallium sulfide dual core highly birefringent photonic crystal fiber is proposed. The high birefringence and dual core are achieved by introducing two kinds of circular air holes with different diameters into the fiber core. The mode coupling characteristics of the even and odd modes in the proposed dual core PBS are investigated using the finite-difference time-domain method and coupled-mode theory. The numerical simulation results indicate that, when the incident light frequency is 4.5 μm and the PBS length is 277.1 μm, a wide bandwidth of 170 nm (from 4.472 to 6.642 μm) with a polarization extinction ratio (ER) >20 dB is obtained in the mid-IR waveband. The highest ER of 112.8 dB is realized. The designed PBS will find potential applications in mid-IR optical sensing, communication, and imaging systems because of its wide bandwidth and ultrashort length.

Broadband graphene-based optical power coupler and polarization beam splitter using a directional coupler

The utilization of directional couplers (DCs) as power splitters and combiners is ubiquitous for the realization of integrated silicon photonic devices in the silicon-on-insulator (SOI) platform. Benefiting from the excellent modal modulation performance of graphene in silicon waveguides, we present its high flexibility to engineer and reduce the wavelength dependence of devices based on the DC. In this regard, a wavelength-insensitive 3-dB optical power coupler (3-dB OPC) is firstly proposed, in which various power splitting ratios are realized for the TE mode. Next, we design a broadband polarization beam splitter (PBS) consisting of a silicon waveguide (SW) and a graphene-silicon vertical slot waveguide (GSVSW). The simulation results show that the proposed PBS has high polarization extinction ratios (PERs) of 20.93 and 20.4 dB and low insertion losses (ILs) of 0.12 and 0.21 dB at 1550 nm for the thru and cross ports, respectively. In addition, the designed PBS demonstrates the ability to work over a wide range of wavelengths by changing the chemical potential of graphene.

Tilted Nano-Grating Based Ultra-Compact Broadband Polarizing Beam Splitter for Silicon Photonics.

An ultra-compact broadband silicon polarizing beam splitter is proposed based on a tilted nano-grating structure. A light cross coupling can be realized for transverse-magnetic mode, while the transverse-electric light can almost completely output from the through port. The length of the coupling region is only 6.8 μm, while an extinction ratio of 23.76 dB can be realized at a wavelength of 1550 nm. As a proof of concept, the device was fabricated by a commercial silicon photonic foundry. It can realize a 19.84 dB extinction ratio and an 80 nm working bandwidth with an extinction ratio of larger than 10 dB. The presented device also shows a good fabrication tolerance to the structure deviations, which is favorable for its practical applications in silicon photonics.

Mid-infrared broadband polarization beam splitter based on GaS photonic crystal fiber with high extinction ratio

We design a mid-infrared polarization beam splitter (PBS) based on GaS chalcogenide dual-core photonic crystal fiber (PCF) with large bandwidth and high polarization extinction ratio (ER). The mode-coupling characteristics between the x- and y-polarized even and odd modes are investigated in the 3.5–4.5 µm range by employing the finite element method (FEM). The effects of PBS structure parameters on the coupling length (CL) and coupling length ratio (CLR) are analyzed. The results reveal that for the optimized structural parameters of a = 0.8 µm, b = 0.23 µm, d1 = 1 µm, d2 = 0.5 µm, e1 = 2.02 µm and e2 = 1.5 µm, an ultrabroad bandwidth of 412 nm (from 3.766 µm to 4.188 µm) with polarization ER better than 20 dB is achieved within an ultrashort length of 45.4 µm. The highest ER of 104 dB at the wavelength of 4 µm is obtained. The proposed PBS will become an excellent candidate for mid-infrared optical communication, optical sensing, optical precision metrology and optical nonlinearity.