TM-pass Polarizer Research Articles

Ultra-broadband and high extinction ratio silicon TM-pass polarizer based on grating-assisted antisymmetric multimode waveguide

We propose an all-silicon TM-pass polarizer using a grating-assisted antisymmetric multimode waveguide (GAMW). The GAMW design facilitates the conversion of the undesired TE0 mode into the back-reflected TE1 mode, enabling efficient transmission of the desired TM0 mode with low insertion loss (IL) and high extinction ratio (ER). Furthermore, by cascading multiple GAMW structures, the device can filter TE0 mode over a broader spectral range effectively. The simulation results indicate that the single-GAMW-based polarizer achieves IL < 0.17 dB and ER > 40 dB in the wavelength range from 1480 nm to 1620 nm. When cascaded, the device expands the bandwidth to 275 nm (1435 nm–1710 nm), maintaining IL < 1 dB and ER > 40 dB simultaneously. The bandwidth can be further improved by cascading more GAMW structures working at different central Bragg wavelength. Limited by the measuring equipment, the measured wavelength range is between [1470 nm, 1630 nm]. The results of experiment demonstrate that the fabricated single-GAMW-based polarizer achieves IL < 0.65 dB and ER > 28.4 dB in 144 nm bandwidth ranging from 1470 nm to 1614 nm. For the cascaded-GAMW-based polarizer, IL < 0.83 dB and ER > 28.8 dB is achieved throughout the entire measuring wavelength range.

Compact, low-loss, and high-polarized-extinction ratio terahertz TM-pass polarizer based on a hybrid plasmonic waveguide with a graphene ridge

A compact, low-loss, and high-polarized-extinction ratio TM-pass polarizer based on a graphene hybrid plasmonic waveguide (GHPW) has been demonstrated for the terahertz band. A ridge coated by a graphene layer and the hollow HPW with a semiround arch (SRA) Si core is introduced to improve structural compactness and suppress the loss. Based on this, a TM-pass polarizer has been designed that can effectively cut off the unwanted TE mode, and the TM mode passes with negligible loss. By optimizing the angle of the ridge, the height of the ridge, air gap height, and the length of the tapered mode converter, an optimum performance with a high polarization extinction ratio of 30.28 dB and a low insert loss of 0.4 dB is achieved in the 3 THz band. This work provides a scheme for the design and optimization of polarizers in the THz band, which has potential application value in integrated terahertz systems.

Demonstration of an Ultra-Compact and Broadband TM-Pass Polarizer Using Nano-Elliptical Holes

Demonstration of an Ultra-Compact and Broadband TM-Pass Polarizer Using Nano-Elliptical Holes

Ultra-broadband TM-pass polarizer based on anisotropic metamaterials in lithium niobate on an insulator.

An ultra-broadband TM-pass polarizer is designed, fabricated, and experimentally demonstrated based on subwavelength grating (SWG) metamaterials in a lithium niobate on an insulator (LNOI) platform. According to our simulation, the designed device is predicted to work at a 220 nm wavelength range from 1460 to 1680 nm, covering the S-, C-, L-, U-bands of optical fiber communication. By depositing and subsequently etching a silicon nitride thin film atop the LNOI chip, the SWG structures are formed successfully by using complementary metal-oxide semiconductor (CMOS)-compatible fabrication processes. The measured results show a high polarization extinction ratio larger than 20 dB and a relatively low insertion loss below 2.5 dB over a 130 nm wavelength range from 1500 to 1630 nm, mainly limited by the operation bandwidth of our laser source.

High performance TM-pass polarizer using multimode Bragg grating waveguide

A novel ultra-broadband TM-pass polarizer with high polarization extinction ratio (PER) and low reflection has been proposed and demonstrated by utilizing multimode Bragg grating waveguide (MBGW) and two tapered waveguides. By optimizing the period of the MBGW, the injected TE0 mode is coupled into the backward TE2 mode and effectively leaked into the cladding. Meanwhile, the injected TM0 mode propagates through the polarizer without any negative impact. The operation bandwidth can be significantly expanded by cascading multiple MBGW structures, each of which operates at a different central Bragg wavelength. The simulation results indicate that the designed polarizer can achieve an insertion loss (IL) below 0.24 dB and a PER above 39 dB simultaneously across a bandwidth of 300 nm (1400 nm∼1700nm), while the reflected signal is below −9.1 dB. The experiment results demonstrate that the fabricated polarizer can realize an IL below 0.56 dB and a PER above 33 dB in a 160 nm bandwidth ranging from 1470 nm to 1630 nm. Due to limitations in the equipment used, measurements for other wavelength ranges are not conducted. With these merits, the proposed device would find significant applications in optical communication systems.

High-performance TM-pass polarizer based on anti-symmetric Bragg gratings.

We present an all-silicon transverse-magnetic-pass (TM-pass) polarizer based on anti-symmetric Bragg gratings. We obtain wide operation bandwidth and high polarization extinction ratio (PER) by maximizing the coupling between the forward TE0 mode and the backward TE1 mode through the reduction of the bridge element width. In the meantime, low insertion loss (IL) is acquired with long tapered structures and the exclusion of the center grating part. Experimental results indicate IL below 0.74 dB and PER over 40 dB covering the wavelength ranges of 1275-1360 nm and 1500-1523 nm, while the average IL within these ranges is as low as 0.27 dB. Additionally, simulation results suggest that the performance can be further improved by introducing chirp in the period of Bragg gratings, thus achieving IL < 0.11 dB and PER > 60 dB over a wide range of 280 nm (1290-1570 nm).

Multi-band all-silicon TM-pass polarizer based on one-dimensional photonic crystals nanohole array

We propose an on-chip transverse magnetic (TM)-pass polarizer utilizing one-dimensional photonic crystals for multi-band operation. The TE0 modes in the 1550/2000nm wave band are suppressed by carefully selecting the pitch lengths of the nanoholes, leveraging the bandgap of the nanohole array. Conversely, the TM0 modes remain almost unaffected. The TM-pass polarizer employs a single-etched design on a standard 220 nm SOI platform and has a compact length of ∼ 17.9 µm. The simulated bandwidths (BWs) for polarization extinction ratios (PERs) &gt; 20 dB and &gt; 25 dB are about 210 nm and 195 nm for the 1550 nm wave band, and 265 nm and 240 nm for the 2000nm wave band. Moreover, the insertion losses (ILs) are ∼ 0.5/0.3 dB at wavelengths of 1550/2000nm, respectively. For the fabricated device, the measured BWs for PER &gt; 20 dB and &gt; 25 dB are evaluated to be larger than 100 nm for both 1550/2000nm wave bands. The measured ILs are 1/0.8 dB at wavelengths of 1550/2000nm. This straightforward and compatible design opens possibilities for the development of practical multi-band silicon photonic integrated circuits.

On-chip multifunctional polarizer based on phase change material.

Polarizers are used to eliminate the undesired polarization state and maintain the other one. The phase change material Ge2Sb2Se4Te1 (GSST) has been widely studied for providing reconfigurable function in optical systems. In this paper, based on a silicon waveguide embedded with a GSST, which is able to absorb light by taking advantage of the relatively large imaginary part of its refractive index in the crystalline state, a multifunctional polarizer with transverse electric (TE) and transverse magnetic (TM) passages has been designed. The interconversion between the two types of polarizers relies only on the state switching of GSST. The size of the device is 7.5µm∗4.3µm, and the simulation results showed that the extinction ratio of the TE-pass polarizer is 45.37dB and the insertion loss is 1.10dB at the wavelength of 1550nm, while the extinction ratio (ER) of the TM-pass polarizer is 20.09dB and the insertion loss (IL) is 1.35dB. For the TE-pass polarizer, a bandwidth broader than 200nm is achieved with ER>20dB and IL<2.0dB over the wavelength region from 1450 to 1650nm and for the TM-pass polarizer, ER>15dB and IL<1.5dB in the wavelength region from 1525 to 1600nm, with a bandwidth of approximately 75nm.

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.

Ultrahigh-extinction-ratio and broadband all-silicon TM-pass polarizer by employing multimode anti-symmetric apodized Bragg grating

On-chip polarizers are the essential components for polarization management in integrated systems. Hence, polarizers with broad operation bandwidth (BW), low insert loss (IL), and high polarization extinction ratio (PER) are highly desired. A broadband and ultra-high ER all-silicon transverse-magnetic-pass polarizer is presented and experimentally demonstrated on the 220 nm silicon-on-insulator platform. The proposed device consists of a TE1 mode filter and a multimode anti-symmetric apodized Bragg grating (MASABG). The MASABG works as a Bragg reflector to convert forward TE0 to backward TE1 mode, and then the reflected TE1 gradually evolves into the TE0 mode in the mode filter and finally leaks out. The device exhibits efficient polarization selectivity, facilitated by fully etched rectangular holes inside the waveguide to introduce strong periodic perturbations in the MASABG. Simulation results predict that the designed polarizer achieves ultra-high PER ∼60 dB with low IL &amp;lt; 0.2 dB at around 1550 nm, and the calculated BWs for PER &amp;gt;30 and &amp;gt;40 dB are estimated to be 275 and 268 nm, respectively. More importantly, the reflection of the eliminated TE polarization is suppressed to below −12 dB. For the fabricated polarizer, the measured BWs for PER &amp;gt;30 and &amp;gt;40 dB are about 260 and 150 nm, respectively, and the measured IL is &amp;lt;0.9 dB in a wide wavelength range of 1410–1700 nm.

Ultra-compact and broadband all-silicon TM-pass power splitter using subwavelength holey-structured metamaterial waveguides.

Power splitters with polarization management features are highly desired to construct high-density silicon photonic integrated circuits. However, few attempts have been made to design a single device that can act as both a power splitter and a TE- or TM-pass polarizer. In this paper, for the first time, we experimentally demonstrate an ultra-compact and broadband all-silicon TM-pass power splitter, where a triple-guide directional coupler (TGDC) composed of three parallel subwavelength holey-structured metamaterial waveguides (SHMWs) is located at central coupling region and three regular strip waveguides are connected at the input/output ports. Such a SHMW can enhance the reflection to realize a wide stop-band for the undesired TE polarized light, while achieving the low loss transmission for the TM polarized light. Besides, the TM dispersion can be significantly flattened by the designed SHMWs, leading to a broadband power splitting for TM polarization. Simulated results show that an ultra-compact device of 1.7 × 4 µm2 in size is obtained with an insertion loss (IL) of 0.34 dB and an extinction ratio (ER) of 36 dB at 1550 nm, and its working bandwidth can be extended to ∼240 nm by keeping IL < 0.9 dB and ER > 16 dB. The measurements of the fabricated devices show low IL (<1 dB) and high ER (>15 dB) over the measured wavelength range of 1460 to 1580 nm, which is consistent with the simulation results.

Broadband and low-loss TM-pass polarizer using tilted subwavelength structures

Photonic systems built on the Silicon-on-Insulator platform exhibit a strong birefringence, and must thus be operated with a single polarization for most applications. Hence, on-chip polarizers that can effectively suppress an undesired polarization state are key components for these systems. Polarizers that extinguish TE polarized light while letting TM polarized light pass with low losses are particularly challenging to design for the standard 220 nm Silicon-on-Insulator platform, because the modal confinement is stronger for TE polarization than for TM polarzation. Here, we propose and design a broadband, low loss and high extinction ratio TM-pass polarizer by engineering a Bragg grating that reflects the fundamental TE mode into the first order TE mode using a subwavelength metamaterial which at the same time allows the TM mode to pass. Our device achieves an extinction ratio in excess of 20 dB, insertion losses below 0.5 dB and back-reflections of the fundamental TE mode of the order of -20 dB in a bandwidth of 150 nm as demonstrated with full 3D-FDTD simulations.

Compact and ultra-broadband all-silicon TM-pass and TE-reflected polarizer using grating based weakly coupled nanowires.

On-chip silicon polarizers with broad operating bandwidth and compact footprint have recently attracted increasing attention for their applications in large capacity and high density integrated optical systems. However, strong waveguide dispersion usually limits the bandwidth of the silicon polarizers, especially for the TM-pass polarizers. In this paper, we overcome the bandwidth limit of the TM polarizer by utilizing a novel waveguide structure composed of two weakly coupled nanowires with gratings sandwiched in between. Such a structure can effectively enlarge the bandgap for the undesired TE polarized light, while act as a low loss subwavelength metamaterial for TM polarized light over an extremely large wavelength range. In simulation, we obtain a compact polarizer of 13.6 µm × 1.3 µm in size with an ultra-broad operating bandwidth of ∼362 nm for extinction ratios (ERs) >21 dB and insertion losses (ILs) <1 dB, which covers E-, S-, C-, L-, and U-bands and part of O-band. The measurements of fabricated devices show that the device performed well in the test wavelength range from 1300 to 1600 nm with an ER >15 dB and an average IL ∼1 dB, consistent with the simulation results. This work paves a new way for designing compact and ultra-broadband on-chip polarizers.

Compact and low-loss TM-pass polarizer based on a hybrid plasmonic waveguide with a semiround arch Si core.

A compact and low loss TM-pass polarizer based on a hybrid plasmonic waveguide (HPW) has been demonstrated. By introducing the hollow HPW with a semiround arch (SRA) Si core, the unwanted TE mode can be effectively cut off and the TM mode can pass through by hybrid plasmonic mode with excellent transmission characteristics. The hollow structure realizes lower index with n=1 due to the air region, and the SRA construction effectively suppresses the energy loss of the TM mode caused by the corner effect. Thus, TM modes pass through with negligible loss and exhibit the characteristic of strong mode limitation. By optimizing the width of metal, the width of the HPW, and the length of the tapered mode converter, an optimum performance with a high polarization extinction ratio of 67.87 dB and a low insert loss of 0.029 dB at the work wavelength=1550nm is achieved. Detailed analysis also proves that the proposed polarizer has a compact size of only 7 µm and a great fabrication tolerance. This work offers a simple and effective scheme of polarization control on-chip.

Ultra-Broadband and Compact TM-Pass Polarizer Based on Graphene-Buried Polymer Waveguide.

We report an ultra-broadband and compact TM-pass polarizer based on graphene-buried polymer waveguides. The characteristic parameters of the polarizer were carefully designed and optimized. The standard microfabrication processes were employed to fabricate the device. The presented polarizers exhibit high polarization-dependent transmission imposing a TE mode cutoff while leaving the TM mode almost unaffected. We experimentally demonstrated the polarizer that has an ultra-high extinction ratio of more than 22.9 dB and 41.9 dB for the monolayer graphene film placed on the surface of core layer and buried in the center of core layer, respectively, and as low insertion loss as ~4.0 dB for the TM mode with the bandwidth over 110 nm. The presented polarizer has the advantages of high extinction ratio, ultra-broadband, low cost, and easy integration with other polymer-based planar lightwave devices.

Ultra-compact SOS-based bi-metallic TM-pass polarizer

Ultra-compact transverse magnetic (TM)-pass polarizer based on silicon on sapphire (SOS) platform is proposed and analysed. Low power consumption, high linearity and high speed of transmission are the major advantages of the SOS platform in different commercial applications especially in the mid infrared region.The suggested structure has bimetallic configuration of aluminium doped zinc oxide (AZO) and zirconium nitride (ZrN) to highly attenuate the quasi transverse electric (TE) mode. This is due to the coupling between the fundamental TE and the surface plasmon modes. However, the transverse magnetic mode can propagate with minimal losses. At 2.0 µm operating wavelength, the proposed TM-pass polarizer realizes 20.3 dB extinction ratio (ER) with 0.14 dB insertion loss (IL) at a device length of 3.0 µm. Therefore, the reported design has advantages of compact length, high efficiency and CMOS-compatibility.

All-silicon multi-band TM-pass polarizer on a 220 nm SOI enabled by multiplexing grating regimes.

We propose an all-silicon design of a multi-band transverse-magnetic-pass (TM-pass) polarizer. The device is based on one-dimensional gratings that work under different regimes that depend on the polarization. With a tapered structure, it is revealed that the operation bandwidth can be extended by multiplexing the diffraction in O-band and the reflection in S-, C-, and L-bands for the transverse-electric (TE) mode. By simulation, we achieve a 343 nm device bandwidth with insertion loss (IL) < 0.4 dB and polarization extinction ratio (PER) > 20 dB. The operation wavelength range covers commonly-used optical telecommunication bands including the O-, S-, C-, and L- bands. Experimental results also show IL < 1.6 dB and PER > 20 dB from 1265 nm to 1360 nm corresponding to the O-band, and from 1500 nm to 1617 nm that corresponds to the C-band. The device is a single-etched design on the standard 220 nm silicon-on-insulator (SOI) with silicon oxide cladding. Such a simple and compatible design paves the way for developing practical multi-band silicon photonic integrated circuits.

Leaky-mode long-period grating on a lithium-niobate-on-insulator waveguide

Lithium niobate on insulator (LNOI) is a promising platform for the construction of high-density integrated photonics circuits. In this paper, we propose compact long-period gratings (LPGs) formed on LNOI rib waveguides for achieving light coupling from the guide mode to the leaky mode. Our LPGs are polymer gratings coated on the surfaces of LNOI waveguides and can be designed to achieve strong mode coupling at specific resonance wavelengths for the TE-like and the TM-like polarization. By means of a numerical analysis, we find that the LPGs exhibit turning points in the phase-matching curves, which promises the realization of broadband wavelength filters and polarizers with such grating structures on the LNOI platform. To experimentally verify the theoretical results and demonstrate the LPG characteristics, we fabricate a number of LPG filters on LNOI rib waveguides, which include two broadband LPGs operating near the turning points: a TE-pass polarizer with a 20 dB extinction ratio over a bandwidth of 270 nm from 1430 to 1700 nm and a TM-pass polarizer with a 20 dB extinction ratio over a bandwidth of 90 nm from 1500 to 1590 nm. The insertion losses for the passing polarization are smaller than 2 dB in the C + L band. Our LPGs can serve as building blocks for the development of a wide range of integrated LNOI devices for application in on-chip signal processing.

Utilizing thermally induced selective mode shaping for a high extinction ratio in-line fiber modulator/polarizer.

Light-matter interactions of guided modes strongly depend on mode shape. This Letter presents an ultrahigh extinction ratio (ER) polarizer/modulator at λ=1.55µm, enabled by selective mode reshaping for different orthogonal modes. This bi-function device benefits from a designed side-polished fiber (SPF) with a three-layer stack of graphene/VO2/PMMA overlay. Thermally induced insulator-metal transition (IMT) in VO2 via a graphene microheater leads to the polarization-selective mode shaping (PSMS), which is used to manipulate orthogonal modes separately. As a result, a TE modulator (TM-pass polarizer) with an ultrahigh ER=168.4dB/mm (175.1 dB/mm) and low insertion loss (IL) of IL=3.38dB/mm (0.34 dB/mm) is achieved.

Design and simulation of tunable TE and TM pass polarizers based on VO2/Si hybrid waveguide

Active transverse electric and transverse magnetic pass polarizers with lengths of only 1.92 μm and 5.95 μm based on silicon waveguides and phase change material VO2 films are theoretically demonstrated. The optical characteristics of the polarizers are simulated by using finite difference mode simulation. By controlling the phase state of VO2 film, the polarizers can realize the regulation of TE and TM polarizations. The insertion losses of both polarizers are less than 2.2 dB in the insulating state. When trigger to the metallic state, the unwanted polarization attenuation exceeds 21.07 dB while insertion losses are kept below 0.71 dB at a center wavelength of 1550 nm. Both polarizers have a high extinction ratio in the operating bandwidth of 200 nm. This provides a new way for polarizers based on VO2 film and silicon waveguide.