Agnieszka Mossakowska-Wyszynska

Relaxation oscillations in a laser with a Gaussian mirror

We present an analysis of the relaxation oscillations in a laser with a Gaussian mirror by taking into account the three-dimensional spatial field distribution of the laser modes and the spatial hole burning effect. In particular, we discuss the influence of the Gaussian mirror peak reflectivity and a Gaussian parameter on the damping rate and frequency of the relaxation oscillation for two different laser structures, i.e., with a classically unstable resonator and a classically stable resonator.

Light generation in planar waveguide DFB and F-P lasers with photonic crystal

In this paper, for the first time we present an analysis of the nonlinear operation of the F-P and DFB lasers based on photonic crystal structure. In our theoretical mode, we take into account the gain saturation effect, transverse and longitudinal field distribution. That model allows to define in easy ways the influence of the real structures parameters (for example photonic crystal cell geometry) on the normalized small signal gain.

Bistable Operation of 1-D Photonic Crystal Laser With Saturable Absorber

Bistable operation of a 1-D photonic crystal (PC) laser with a nonlinear absorber is presented. The model is based on a modified transfer matrix method with a Bloch wave formalism and allows to define, in an easy way, the influence of the real structures parameters, such as a period of the structure, contrast of the refractive indices of crystal layers, the number of the primitive cells creating the PC, the loss level, and the pumping level on the bistable operation of the investigated structures. The geometry of the PC primitive cell (i.e., a period of the PC structure and the number of the primitive cells creating the PC) is chosen in such a way as to obtain the laser wavelength at the bandgap edge where considerable enhancement of the laser gain is observed. Furthermore, four laser structures, in which the absorber is located at different positions relating to the active medium in the resonator, are examined. The influences of the PC geometry, the output mirror reflectivity, and the saturable losses on the hysteresis loop are investigated.

Modulation bandwidth of planar circular grating distributed Bragg reflector lasers

This paper presents an analysis of the 3-dB-modulation bandwidth in planar circular grating distributed Bragg reflector lasers. The theoretical model takes into account both the spatial hole burning effect and the transverse and longitudinal field distribution. That model allows the study of the influence of real structure parameters on the 3-dB-modulation bandwidth.

Effect of Nonlinear Loss and Gain in Multilayer PT -Symmetric Bragg Grating

The analysis of a nonlinear gain and loss in multilayer PT-symmetric Bragg grating structure is presented. The simple model shows wave propagation through nonlinear multilayer grating in an optical way (without the need to use complex methods). A new behavior of output intensity versus input intensity in such a structure has been obtained for the first time. At the beginning, the structure is examined without taking into account the gain and loss saturation. In this case, the characteristics of reflection and transmission coefficients, and eigenvalues of S matrix are obtained as a function of geometrical parameters of Bragg gratings. The characteristics reveal special points, discussed later, where the structure is PT-symmetric or has a broken symmetry phase. In the first case, the amplitudes of both waves, travelling in opposite directions, do not change, which corresponds to the unimodularity of the S matrix eigenvalues. In the other case, the increase of one amplitude forces the decrease of the other one, and the eigenvalues have reciprocal magnitudes. For these points, the systematic study including the gain and loss saturation effects is conducted. The obtained characteristics illustrate the influence of the saturation intensities on the output intensities, reflection and transmission coefficients, and eigenvalues of S matrix for the incident plane wave with a given intensity. The characteristics demonstrate strong nonreciprocal response and the bistable behavior of the structure. Moreover, for certain values of Bragg gratings geometrical parameters, the investigated structure transits from broken symmetry phase to a PT-symmetric one.

Transmission properties analysis of 1D PT-symmetric photonic structures

The transmission properties of one dimensional PT-symmetric photonic crystal (PC) structure with gain and loss regions are presented. Obtained characteristics illustrate the influence of the structures parameters such as the ratio of the PC period to the operating wavelength, the number of the primitive cells creating PC, the loss and gain level (imaginary part of the refractive indices) on reflection and transmission coefficients. It demonstrates strong nonreciprocal response of the structure.

Approximate model of a DBR/F-P laser based on Raman effect in a silicon-on-insulator rib waveguide

An approximate method of modeling of Raman generation in silicon-on-insulator(SOI) rib waveguide with DBR/F-P resonator including nonlinear effects such as Raman amplification and free-carrier absorption (FCA), is presented. In our detailed theoretical model, we consider coupled set of differential equations for pump signal and Stokes signal inside the laser cavity. In threshold analysis of steady-state Raman laser operation, we assume that the pump signal distribution is determined from linear equations. An analytical formula relating threshold pump power to the system parameters is obtained. The analysis of the above threshold operation is based on an energy theorem and threshold field approximation. In exact energy conservation relation, we approximate the pump and Stokes field distributions by these proportional to linear field distribution existing at the threshold, obtaining an approximate, semi-analytical expression related the Raman output power (i.e. the output power of Stokes lasing) to the pump power and system parameters. With this formula, the laser characteristics revealing the optimal rib waveguide geometry and the optimal coupling coefficients, which provide the maximal power efficiency, can be obtained.

Modeling of light generation in photonic crystal lasers

In this paper, we present an analysis of light generation in various lasers based on photonic crystal structures. In our theoretical model, we take into account the gain saturation effect, transverse and longitudinal field distribution. That model allows defining in easy way the influence of the real structures parameters (for example photonic crystal cell geometry) on the normalized small signal gain, spontaneous emission, relaxation oscillation parameters, and 3dB modulation bandwidth.

Nonlinear operation of planar waveguide laser with 2D photonic crystal

We present semi analytical, approximate model of nonlinear operation of planar waveguide laser manufactured on the base of 2D photonic crystal. We consider laser structure with F-P cavity and take into account the gain saturation effect, transverse as well as longitudinal field distribution. Our model, based on energy theory, allows to investigate in relatively easy way the influence of the real structure parameters such as photonic crystal geometry, waveguide geometry, losses as well as strength of feedback (i.e. cavity parameters) on output power level. The laser characteristics obtained reveal optimal feedback strength for given laser structure, which provide maximal power efficiency for given pumping level.

Analysis of relaxation oscillations in planar circular grating DFB and DBR lasers

In this paper, we present an analysis of relaxations oscillations in planar circular grating DFB and DBR lasers. In our theoretical model, we take into account the transverse and longitudinal field distribution. That model allows to study the influence of the real structures parameters on the relaxation oscillations.