Theoretical Analysis of On-chip Vertical Hybrid Plasmonic Nanograting

a CMOS compatible photonic-plasmonic waveguide with nanoscale optical confinement has been proposed for the infrared (IR)-band applications. The design is based on the multilayer hybrid plasmonic waveguide (Si-SiO2-Au) structure. The 3D-finite element method (FEM) numerical simulation of single slot HPWG confirms 2.5 dB/cm propagation loss and 15 um− 2 confined intensity. Moreover, its application as dual-slot nanograting is studied which shows better propagation length and ultra-low dispersion near the 1550 nm wavelength. Hence, proposed low-dispersion design is suitable for future on-chip nanophotonic components in the IR band.

High Performance p-i-n Photodetectors on Ge-on-Insulator Platform

In this article, we demonstrated novel methods to improve the performance of p-i-n photodetectors (PDs) on a germanium-on-insulator (GOI). For GOI photodetectors with a mesa diameter of 10 μm, the dark current at −1 V is 2.5 nA, which is 2.6-fold lower than that of the Ge PD processed on Si substrates. This improvement in dark current is due to the careful removal of the defected Ge layer, which is formed with the initial growth of Ge on Si. The bulk leakage current density and surface leakage density of the GOI detector at −1 V are as low as 1.79 mA/cm2 and 0.34 μA/cm, respectively. GOI photodetectors with responsivity of 0.5 and 0.9 A/W at 1550 and 1310 nm wavelength are demonstrated. The optical performance of the GOI photodetector could be remarkably improved by integrating a tetraethylorthosilicate (TEOS) layer on the oxide side due to the better optical confinement and resonant cavity effect. These PDs with high performances and full compatibility with Si CMOS processes are attractive for applications in both telecommunications and monolithic optoelectronics integration on the same chip.

Elongated-Hexagonal Photonic Crystal for Buffering, Sensing, and Modulation

A paradigm for high buffering performance with an essential fulfillment for sensing and modulation was set forth. Through substituting the fundamental two rows of air holes in an elongated hexagonal photonic crystal (E-PhC) by one row of the triangular gaps, the EPCW is molded to form an irregular waveguide. By properly adjusting the triangle dimension solitary, we fulfilled the lowest favorable value of the physical-size of each stored bit by about μ5.5510 μm. Besides, the EPCW is highly sensitive to refractive index (RI) perturbation attributed to the medium through infiltrating the triangular gaps inside the EPCW by microfluid with high RI sensitivity of about 379.87 nm/RIU. Furthermore, dynamic modulation can be achieved by applying external voltage and high electro-optical (EO) sensitivity is obtained of about 748.407 nm/RIU. The higher sensitivity is attributable to strong optical confinement in the waveguide region and enhanced light-matter interaction in the region of the microfluid triangular gaps inside the EPCW and conventional gaps (air holes). The EPCW structure enhances the interaction between the light and the sensing medium.

The Overlap Factor Model of Spin-Polarised Coupled Lasers

A general model for the dynamics of arrays of coupled spin-polarised lasers is derived. The general model is able to deal with waveguides of any geometry with any number of supported normal modes. A unique feature of the model is that it allows for independent polarisation of the pumping in each laser. The particular geometry is shown to be introduced via ’overlap factors’, which are a generalisation of the optical confinement factor. These factors play an important role in determining the laser dynamics. The model is specialised to the case of a general double-guided structure, which is shown to reduce to both the spin flip model in a single cavity and the coupled mode model for a pair of guides in the appropriate limit. This is applied to the particular case of a circular-guide laser pair, which is analysed and simulated numerically. It is found that increasing the ellipticity of the pumping tends to reduce the region of instability in the plane of pumping strength versus guide separation.

Numerical Design and Frequency Response of all group-IV alloys based MQW Transistor Laser

In this work, a theoretical model is developed for n-p-n mid-infrared transistor laser (TL) with strain-balanced Ge0.85Sn0.15 multiple quantum well (MQW) structure in the base. Variation of optical confinement factor, modal gain and threshold current density have been rigorously investigated for different number of QWs (N) in MQW structure. The result shows that overall optical confinement factor and modal gain increase with N. The frequency response of MQWTL for common base (CB) configuration is estimated from small signal relationship between the photon density and emitter current density by solving laser rate equation and continuity equation considering the virtual states as a conversion mechanism. Increment of N causes modulation bandwidth to initially increase and then decreases with N, which reveals a shifting of device nature for higher values of N. The results also suggest that on judicious selection of N, the proposed device can become a viable monolithic light source.

Влияние латерального оптического ограничения на характеристики вертикально-излучающих лазеров cпектрального диапазона 1.55 μm с заращенным туннельным переходом

The impact of transverse optical confinement on the static and spectral characteristics of 1.55 µm vertical-cavity surface-emitting lasers (WF-VCSEL) with a buried tunnel junction (BTJ) n++-InGaAs/р++-InAs/р++-InAlGaAs, implemented using molecular-beam epitaxy and wafer fusion. For lasers with a tunnel junction (TJ) etching depth of ~ 15 nm, it was found that the single-mode lasing occurs up to 8 μm BTJ mesa size due to a relatively weak lateral optical confinement, while the effect of a saturable absorber (SA) appears when the BTJ mesa size is less than 7 µm. Enhancing lateral optical confinement by increasing the BTJ etching depth up to ~ 20 nm leads to suppression of the SA effect at the BTJ mesa size of 5–6 µm, but at the same time limits the maximum single-mode optical power. According to the results of the analysis, an increase in the spectral mismatch between the maximum of the gain spectrum of the active region and the resonance wavelength of the WF-VCSEL up to ~35-50 nm will make it possible to suppress the undesirable SA effect in a wide range of the BTJ mesa sizes maintaining the single-mode lasing.

Влияние конструкции активной области и волновода на характеристики лазеров на основе структур квантовые ямы-точки InGaAs/GaAs

We study edge-emitting lasers with the active area based on novel InGaAs/GaAs quantum heterostructures of transitional dimensionality referred to as quantum well-dots, which are intermediate in properties between quantum wells and quantum dots. We show that the rate of the lasing wavelength blue-shift occurring with the reduction in cavity length decreases with an increase in the number of quantum well-dot layers in the active region and the optical confinement factor. In the laser based on 10 quantum well-dot layers, the position of the lasing wavelength remains in the optical region corresponding to the emission from the ground state down to the cavity lengths as short as 100 μm. In the devices based on a single quantum well-dot layer and/or with low optical confinement factor, lasing directly switches from the ground state to the GaAs waveguide states omitting excited state lasing with decrease in cavity length below 200 μm. Such an effect has not been observed in quantum well and quantum dot lasers and is attributed to the abnormally low density of excited states in quantum well-dots.