Remzi Yildirim

Applications of the single-mode laser-diode system theory

In this paper, we present a numerical analysis of the system theory of the single-mode laser-diode developed in [Opt. Commun. (Submitted for consideration with this paper)] to obtain numerical results of the gain, pulse response, and the harmonic distortion for electronic feedback. The dependence of the system gain on the feedback gain and delay are presented. The pulse response is studied and it is shown that a transmission rate over 1 Gbyte/s can be achieved. Finally, the harmonic distortion and its dependence on frequency, input amplitude, and feedback delay is presented. Some sources of error and their avoidance in the measurement of harmonic distortion are discussed. Finally, it is shown how, with electronic feedback, distortion can be reduced or even eliminated.

System theory of the single-mode laser-diode

The system theory of the single-mode laser-diode is developed in this paper. Limits of the mathematical validity of the rate equations are analyzed and discussed. The theoretical model of the single-mode laser-diode obtained is shown to be a stable low-pass system whose pole positions are injection current dependent. A Volterra model of the laser diode with electronic feedback is obtained. Conditions for stability are obtained from the model and stability is shown to be dependent on the injection current. It is shown that the system is a bandpass filter whose center frequency and bandwidth can be specified by the feedback parameters. The Volterra model also allows the determination of the nonlinear distortion and, in contrast to optical feedback, methods for reducing it by modifying the feedback operator.

Computer-aided design model for a quantum-cascade laser

This study presents a simple, single and an accurate computer-aided design model for quantum-cascade laser based on multi-layer perceptrons. Each critical quantity (optical gain, differential refractive index change, linewidth enhancement factor) that is used in the model requires long mathematical calculations with a strong background knowledge. In addition to that, these quantities use different theories, estimations and assumptions of some parameter values. The model tremendously decreases the computational time in the order of microseconds and is in very good agreement with previously published results.

Semiconductor laser modeling with ANFIS

In this study, neuro-fuzzy (NF) models are used which are well-known robust learning systems that combine the advantages of fuzzy sets and neuro-computation theory. Particularly, a single model based on the adaptive network-based fuzzy inference system (ANFIS) is successfully developed from the amplified spontaneous emission (ASE) spectra of a semiconductor laser diode in order to obtain the critical quantities and their dependences on wavelength and currents. These critical quantities are the differential gain, the induced effective index change and the linewidth enhancement factor (¿ parameter). The comparison of single model results and the experimental measurements validate the presented approach.

Modeling quantum cascade lasers by multilayer perceptrons

This study presents the computer aided design (CAD) of type-I quantum-cascade lasers (QCLs) based on Artificial Neural Networks (ANNs). QCLs have critical quantities named modal gain, differential refractive index change and the linewidth enhancement factor (LEF, ¿ parameter). Each of these quantities requires lengthy mathematical calculations using different theories and assumptions. The single model is based Multi-layer Perceptrons (MLPs) approach which decreases the computational time with accurate values. MLPs are trained and tested with different learning algorithms and different network configurations in order to get an accurate model. The results are in very good agreement with the previously published results.

Alternative intermodulation frequency components

Volterra power series expansion is performed for four tone small signal input laser diode (LD) with optoelectronic feedback. The analysis is carried out for the IMD frequency components that are obtained from the carrier frequency (ω0) which can be alternatively used in sub-carrier systems.

Design of a chaotic optical communication system by using RAMAN with noise addition technique

In this study. optical carrier and data, which is coining from the 1550 am. CW laser-diode is modulated by using an external optical modulator. The noise that is obtained from the Gaussian white noise source is added to the modulated signal with the help of optical combiners. This combined signal is inputted to the Rarnan Amplifier and the data is transmitted in a 80 kin. fiber optic transmission system. The system is implemented by using chaotic communication tecirnique and the chaotic signal is obtained out of laser diode. Non-return to zero (NRZ) network system is selected in the design.

Asymmetric condition computed from the four tone input GaN HEMT

Asymmetric condition among the IMD components with respect to gate to source voltage (Vgs) of four tone input GaN HEMT is determined which is based on the carrier frequency (¿0). In addition to that, the critical operating frequency interval is established.

Neural computation of alpha parameter with the use of differential gain, wavelength, and number of quantum wells

A different method to determine α (Alpha) parameter for different number of Quantum-wells is presented. The Levenberg-Marquardt algorithm is used to train the Artificial Neural Networks (ANNs) which has a quadratic speed of convergence. Both the computed and the test results are in very good agreement with the experimental results reported elsewhere.

Optical power distribution and phase variation in external-cavity laser diodes

In this study external-cavity laser diodes is analysed from the rate equations approach. Optical power distribution in to the modes is examined as a function of external cavity length and mode number. Also phase variation is analysed in the same way.