This paper presents a robust model free controller (RMFC) for a class of uncertain continuous-time single-input single-output (SISO) minimum-phase nonaffine-in-control systems. Firstly, the existence of an unknown dynamic inversion controller that can achieve control objectives is demonstrated. Afterwards, a fast approximator is designed to estimate as best as possible this dynamic inversion controller. The proposed robust model free controller is an equivalent realization of the designed fast approximator. The perturbation theory and Tikhonov’s theorem are used to analyze the stability of the overall closed-loop system. The performance of the developped controller are verified experimentally in the position control of a pneumatic actuator system.

On-chip optical-interconnect technology emerges as an attractive approach due to its ultra-large bandwidth and ultra-low power consumption. Silicon-on-insulator (SOI) wire waveguides, on the other hand, have been identified to potentially replace copper wires for intra-chip communication. To take advantage of the wide bandwidth of SOI waveguides, wavelengthdivision multiplexing (WDM) has been implemented. However, WDM have inherent drawbacks. Mode-division multiplexing (MDM) is a viable alternative to WDM in MIMO photonic circuits on SOI as it requires only one carrier wavelength to operate. In this vein, mode converters are key components in on-chip MDM systems. The goal of this paper is to introduce a transverse electric mode converter. The suggested device can convert fundamental transverse electric modes to first-order transverse electric ones and vice versa. It is based on small material perturbation which introduces gradual coupling between different modes. This device is very simple and highly compact; the size of which is 3 μm2. Mathematical expressions for both the insertion loss and crosstalk are derived and optimized for best performance. In addition, three-dimensional finite-difference time-domain (3D-FDTD) simulations are performed in order to verify the mathematical model of the device. Our numerical results reveal that the proposed device has an insertion loss of 1.2 dB and a crosstalk of 10.1 dB. The device’s insertion loss can be decreased to 0.95 dB by adding tapers to its material perturbation.

This paper presents results of the characterisation of type I GaSb/AlSb superlattices (SLs) with a thin GaSb layer and varying thicknesses of an AlSb layer. Nextnano software was utilized to obtain spectral dependence of absorption and energy band structure. A superlattice (SL) with an energy bandgap of ~ 1.0 eV and reduced mismatch value was selected for experimental investigation. SLs with single (sample A) and double (sample B) AlSb barriers and a single AlSb layer (sample C) were fabricated using molecular beam epitaxy (MBE). Optical microscopy, high-resolution X-ray diffractometry, and photoluminescence were utilized for structural and optical characterisation. The presence of satellite and interference peaks in diffraction curves confirms the high crystal quality of superlattices. Photoluminescence signal associated with the superlattice was observed only for sample B and contained three low-intensity peaks: 1.03, 1.18, and 1.25 eV. The first peak was identified as the value of the energy bandgap of the SL. Other two peaks are related to optical transitions between defect states located at the interface between the SL and the top AlSb barrier. The time-dependent changes observed in the spectral characteristics are due to a modification of the SL/AlSb interface caused by the oxidation and hydroxylation of the AlSb layer.