Polarization-insensitive Modulator Research Articles

Polarization-insensitive multimode interference coupler on an x-cut thin-film lithium niobate platform.

Thin-film lithium niobate (TFLN) is a promising integrated photonics platform but currently lacks a polarization-insensitive multimode interference (MMI) coupler, a crucial component for polarization-related optical communication applications such as polarization management, polarization-division multiplexing, and polarization-insensitive modulation systems. This paper presents a novel, to the best of our knowledge, approach by rotating the MMI structure on an anisotropic x-cut TFLN at specific angles to compensate for the difference in the beat length between the two polarizations. A polarization-insensitive 1 × 2 MMI coupler is experimentally achieved with measured transmittances of -2.5 to -4 dB for both output ports and polarization modes in the wavelength range of 1520-1580 nm.

Polarization-Insensitive Graphene Modulator Based on Hybrid Plasmonic Waveguide

A polarization-insensitive graphene-assisted electro-optic modulator is proposed. The orthogonal T-shaped metal slot hybrid plasmonic waveguide allows the polarization-independent propagation of transverse electric field mode and complex mode. By the introduction of dual-layer graphene on the ridge waveguide, the polarization-insensitive modulation depths of the TE mode and complex mode are 0.511 dB/µm and 0.502 dB/µm, respectively. The 3 dB bandwidth of the modulator we have proposed is about 127 GHz at the waveguide length of 20 μm. The power consumption of 72 fJ/bit promised potential graphene electro-optic modulator applications for on-chip interconnected information transfer and processing.

Low Voltage Graphene-Based Amplitude Modulator for High Efficiency Terahertz Modulation.

In this paper, a high-efficiency terahertz amplitude modulation device based on a field-effect transistor has been proposed. The polarization insensitive modulator is designed to achieve a maximum experimental modulation depth of about 53% within 5 V of gate voltages using monolayer graphene. Moreover, the manufacturing processes are inexpensive. Two methods are adopted to improve modulation performance. For one thing, the metal metamaterial designed can effectively enhance the electromagnetic field near single-layer graphene and therefore greatly promote the graphene’s modulation ability in terahertz. For another, polyethylene oxide-based electrolytes (PEO:LiClO4) acts as a high-capacity donor, which makes it possible to dope single-layer graphene at a relatively low voltage.

Highly-Efficient, Ultra-Compact and Polarization-Insensitive Electro-Absorption Modulator Driven by Hybrid Silicon-Indium Tin Oxide-Based MOS Capacitors

Polarization-insensitive modulation plays a key role to be compatible with the current fiber communication systems and the further high-capacity multiplexing transmissions on-chip. Here, we propose a highly-efficient, ultra-compact and polarization-insensitive electro-absorption modulator (EAM), which is driven by the hybrid silicon-indium tin oxide (ITO) based metal-oxide-semiconductor (MOS) capacitors. The hybrid silicon-ITO waveguide is formed by embedding an ITO layer in the silicon waveguide center and depositing a second ITO layer on the waveguide surface, thus the light-matter interaction can be strongly enhanced inside the silicon waveguide based on the epsilon-near-zero (ENZ) effect of ITO rather than the commonly employed outside cladding region. By choosing the optimum ENZ condition of ITO layers at the designated wavelength and optimizing the waveguide dimensions, polarization-insensitive modulation is realized with a high modulation efficiency (ME) of ~3.18 dB/ $\mu \text{m}$ (ME discrepancy $\mu \text{m}$ ) for both polarizations, which is superior to the previous reports. Benefiting from this excellent modal modulation feature, we further design a polarization-insensitive EAM in a length of only $8~\mu \text{m}$ . The modulation depth and insertion loss are higher than 25 dB and lower than 0.24 dB at $1.55~\mu \text{m}$ for both polarizations, respectively. Moreover, the corresponding wavelength bandwidth and electric properties are also analyzed including fabrication procedures. The proposed EAM is expected to be applied in the polarization multiplexing transmissions on-chip.

Hybrid Graphene-Silicon Based Polarization-Insensitive Electro-Absorption Modulator with High-Modulation Efficiency and Ultra-Broad Bandwidth.

Polarization-insensitive modulation, i.e., overcoming the limit of conventional modulators operating under only a single-polarization state, is desirable for high-capacity on-chip optical interconnects. Here, we propose a hybrid graphene-silicon-based polarization-insensitive electro-absorption modulator (EAM) with high-modulation efficiency and ultra-broad bandwidth. The hybrid graphene-silicon waveguide is formed by leveraging multi-deposited and multi-transferred methods to enable light interaction with graphene layers in its intense field distribution region instead of the commonly used weak cladding region, thus resulting in enhanced light–graphene interaction. By optimizing the dimensions of all hybrid graphene-silicon waveguide layers, polarization-insensitive modulation is achieved with a modulation efficiency (ME) of ~1.11 dB/µm for both polarizations (ME discrepancy < 0.006 dB/µm), which outperforms that of previous reports. Based on this excellent modulation performance, we designed a hybrid graphene-silicon-based EAM with a length of only 20 µm. The modulation depth (MD) and insertion loss obtained were higher than 22 dB and lower than 0.23 dB at 1.55 µm, respectively, for both polarizations. Meanwhile, its allowable bandwidth can exceed 300 nm by keeping MD more than 20 dB and MD discrepancy less than 2 dB, simultaneously, and its electrical properties were also analyzed. Therefore, the proposed device can be applied in on-chip optical interconnects.

Multi-layer MOS capacitor based polarization insensitive electro-optic intensity modulator.

In this study, a multi-layer metal-oxide-semiconductor capacitor (MLMOSC) polarization insensitive modulator is proposed. The design is validated by numerical simulation with commercial software LUMERICAL SOLUTION. Based on the epsilon-near-zero (ENZ) effect of indium tin oxide (ITO), the device manages to uniformly modulate both the transverse electric (TE) and the transverse magnetic (TM) modes. With a 20μm-long double-layer metal-oxide-semiconductor capacitor (DLMOSC) polarization insensitive modulator, in which two metal-oxide-semiconductor (MOS) structures are formed by the n-doped Si/HfO2/ITO/HfO2/ n-doped Si stack, the extinction ratios (ERs) of both the TE and the TM modes can be over 20dB. The polarization dependent losses of the device can be as low as 0.05dB for the "OFF" state and 0.004dB for the "ON" state. Within 1dB polarization dependent loss, the device can operate with over 20dB ERs at the S, C, and L bands. The polarization insensitive modulator offers various merits including ultra-compact size, broadband spectrum, and complementary metal oxide semiconductor (CMOS) compatibility.

Acousto-Optic Devices Based on Potassium Rare-Earth Tungstates Laser Crystals

We present a family of original acousto-optical devices. They are based on new acousto-optical materials KRE(WO4)2, where RE = Y, Gd, Yb, Lu. A combination of features such as radiation resistance, optical biaxiality and appreciable acousto-optical gure of merit, makes possible creation of polarization-insensitive modulator with almost 100% of di raction e ciency. The de ector with wide angular aperture and broad range of de ection, and collinear tunable lter are also suggested.

Electro-optic polymer based devices and technology for optical telecommunication

Electro-optic polymer waveguide devices are very attractive for optical communication systems, because of their potentially simple and low-cost fabrication procedure. High bandwidth devices are enabled by the low dielectric constant of polymers with negligible dispersion from DC to optical frequencies. We first detail the modelization steps relating to the optical and electrical aspects of devices. We then outline the different steps of the fabrication process of electro-optic polymer based devices. By way of illustrating these considerations, we present some original realizations namely polarization insensitive modulators, switching devices using an asymetric X coupler and optic to RF converters based on difference frequency mixing. To cite this article: P. Labbé et al., C. R. Physique 3 (2002) 543–554.

Polarisation-insensitive modulator and influenceof propagation direction on bulk electroabsorption

The authors report measurements on electroabsorption in deep ridge waveguide structures. The polarisation sensitivity is found to depend not only on the detuning but also on the propagation direction. In an InGaAsP/InP double heterostructure, polarisation insensitivity is obtained over a large detuning range (80 nm) for propagation along the [-110] direction.

Full polarization insensitivity of a 20 Gb/s strained-MQW electroabsorption modulator

We report on a MQW electroabsorption modulator with tensile-strained wells. The device transmission is shown to be fully polarization insensitive, i.e. both in amplitude and phase. The modulation efficiency is over 20 GHz/V (bandwidth higher than 20 GHz and 1 V drive voltage) which is the highest figure of merit reported for any kind of polarization insensitive modulator. Full polarization independence is further demonstrated by 2.5 Gb/s transmission at 1.55 μm over 475 km of standard fiber without penalty at 10/sup -9/ BER whatever the polarization.