Integrated InP polarization rotator using the plasmonic effect

Compact and efficient polarization rotator using laterally asymmetric rib waveguides on a lithium-niobate-on-insulator platform

Photonic devices based on a lithium-niobate-on-insulator (LNOI) are current research hotspots; however, owing to the high refractive index contrast of the LNOI platform and inherent birefringence of lithium niobate itself, such photonic devices are generally polarization sensitive, affecting their further wide application. This paper proposes a simple, compact, and efficient polarization rotator (PR) based on a laterally asymmetric rib waveguide by depositing a layer of semi-infinite silicon nitride dielectric material on one side of the rib waveguide. The results show that a PR with a polarization rotation region length of 15.77 µm is achieved, and the polarization extinction ratio (PER), insertion loss (IL), and polarization conversion efficiency (PCE) are 38.57/68.95 and 0.2/0.22 dB, and 99.99%/almost 100%, respectively, for the fundamental transverse electric mode (T E 0) and transverse magnetic mode (T M 0) at a 1.55 µm wavelength. The operation bandwidth is around 120 nm for the T E 0 mode and T M 0 mode when the PER, IL, and PCE are greater than 20 dB, less than 0.32 dB, and more than 99%, respectively. Fabrication tolerances to the key structural parameters are investigated in detail. In addition, the evolution fields of the T E 0 mode and T M 0 mode along the propagation direction through the proposed device are presented.

Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser

We report, to the best of our knowledge, the first demonstration of a 1555-nm stepped-height ridge waveguide polarization mode converter monolithically integrated with a sidewall grating distributed-feedback (DFB) laser using the identical epitaxial layer scheme. The device shows stable single longitudinal mode (SLM) operation with the output light converted from TE to TM polarization with an efficiency of >94% over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The highest TM mode purity of 98.2% was obtained at IDFB = 180 mA. A particular advantage of this device is that only a single step of metalorganic vapor-phase epitaxy and two steps of III-V material dry etching are required for the whole integrated device fabrication, significantly reducing complexity and cost.

Design of Reflective Polarization Rotator in Silicon Waveguide

In this work, we investigate theoretically the reflective polarization rotator in a silicon waveguide formed by periodically arranged rectangular air holes. The etched air holes generate the large birefringence for the waveguide. The effective refractive index of the non-etched waveguide is isotropic. The structure can be regarded as a stack of alternating birefringent waveplates and isotropic material similar to the folded Šolc filter. The band structure of the stack of birefringent waveplates with isotropic background is calculated to confirm the fact that high reflection peaks in the reflection spectra of the waveguide result from the photonic bandgap. The polarization extinction ratio for the reflected light is 15.8 dB. The highest reflectivity of the device is 93.1%, and the device length is 9.21 μm. An ultra-wide operation bandwidth from 1450.3 to 1621.8 nm can be achieved.

Active control of polarization state of the light in InP waveguide

We demonstrate an InP deep-ridge type multi-quantum-wells (MQWs) waveguide-based active polarization control scheme by using two positive-intrinsic-negative diode phase shifters. The polarization state of horizontal/vertical linearly polarized input light is rotated along the ± 45°-linear polarization axis on the Poincaré sphere by 45°-eigenmode-rotated first phase shifter 1 and subsequently rotated along the vertical/horizontal axis by second normal phase shifter 2. The rotation of the eigenmode axes is obtained by using the surface plasmonic effect. The effective index of the waveguide is changed via quantum-confined Stark effect in the MQW core. The length of each phase shifter is 240 µm. The applied reverse bias voltages are -2.7 V and -1.95 V for the phase shifter 1 and 2, respectively.

Towards Deep Integration of Electronics and Photonics

A combination of computational power provided by modern MOSFET-based devices with light assisted wideband communication at the nanoscale can bring electronic technologies to the next level. Obvious obstacles include a size mismatch between electronic and photonic components as well as a weak light–matter interaction typical for existing devices. Polariton modes can be used to overcome these difficulties at the fundamental level. Here, we review applications of such modes, related to the design and fabrication of electro–optical circuits. The emphasis is made on surface plasmon-polaritons which have already demonstrated their value in many fields of technology. Other possible quasiparticles as well as their hybridization with plasmons are discussed. A quasiparticle-based paradigm in electronics, developed at the microscopic level, can be used in future molecular electronics and quantum computing.