Effects In Vertical-cavity Surface-emitting Lasers Research Articles

Analysis of spatial hole burning and temperature effects in vertical-cavity surface-emitting lasers with internal photonic crystal waveguide

We investigate theoretically the effect of two-dimensional photonic crystal (PC) defect waveguide parameters embedded into vertical-cavity surface-emitting lasers (VCSELs) on static operation of PC-VCSEL, including spatial hole burning (SHB) and temperature in the active regions. In structures with larger pitch of PC holes, SHB occurs dramatically and temperature increases in the active region. In large-hole diameter to pitch ratio, SHB has little effect and temperature is decreased in the active regions. We also show that with higher input current, temperature rises and SHB occurs.

Nonlinear dynamics of the polarization of multitransverse mode vertical-cavity surface-emitting lasers under current modulation

In this paper we report on a theoretical investigation of the nonlinear dynamics of the polarization of multitransverse mode vertical-cavity surface-emitting lasers (VCSELs) under current modulation. Special attention is given to the comparison with a previously studied case of single-transverse mode VCSEL emitting in two orthogonal polarizations. The consideration of spatial effects in VCSEL modifies the polarization dynamics that accompanies the period doubling route to chaos for large modulation amplitudes. Depending on the modulation parameters, the excitation of a higher order transverse mode may either induce chaotic pulsing in an otherwise regularly pulsating VCSEL, or induce a time-periodic pulsing dynamics in an otherwise chaotic VCSEL. Bifurcation diagrams obtained for different modulation frequencies, several values of the dichroism, and different transverse mode characteristics allow us to identify the different scenarios of polarization dynamics in a directly modulated VCSEL. Temporal analysis of carrier number radial profile reveals considerable changes for the multitransverse mode case only constituting the physical origin of the reported changes in the temporal and polarization dynamics.

Tunable vertical-cavity surface-emitting laser with feedback to implement a pulsed neural model 2 High-frequency effects and optical coupling

The operation of an optoelectronic dynamic neural model implementation is extended to higher frequencies. A simplified model of thermal effects in vertical-cavity surface-emitting lasers correctly predicts the qualitative changes in the nonlinear mapping implementation with frequency. Experiments and simulations show the expected resonance properties of this model neuron, along with the possibility of other dynamic effects in addition to the ones observed in the original FitzHugh-Nagumo equations. Results of optical coupling between two similar pulsing artificial neurons are also presented.

Effects of Anisotropies on Vectorial Modes of Vertical-Cavity Surface-Emitting Lasers

The consequences of material anisotropies in vertical-cavity surface-emitting lasers (VCSELs) are analyzed in detail. To this aim we apply the full vectorial model recently published in Bava et al. [Phys. Rev. A 63, 023816 (2001)] which is based on the mode expansion of the vectorial electromagnetic field in the continuous basis of cylindrical TE and TM modes of a reference medium and on coupled mode theory. The self-consistency between backward and forward waves leads to an eigenvalue problem: the complex eigenvalues determine both the required gain and the lasing frequency of the cavity modes, while the eigenvectors allow the reconstruction of the fields. The capability of the fully vectorial treatment to experience the tensorial nature of the dielectrical permittivity is exploited to analyze in detail the consequences of the elasto-optic effect in VCSELs with reference to modal frequencies, gains and profiles.

Effects of Anisotropies on Vectorial Modes of Vertical-Cavity Surface-Emitting Lasers

The consequences of material anisotropies in vertical-cavity surface-emitting lasers (VCSELs) are analyzed in detail. To this aim we apply the full vectorial model recently published in Bava et al. [Phys. Rev. A 63, 023816 (2001)] which is based on the mode expansion of the vectorial electromagnetic field in the continuous basis of cylindrical TE and TM modes of a reference medium and on coupled mode theory. The self-consistency between backward and forward waves leads to an eigenvalue problem: the complex eigenvalues determine both the required gain and the lasing frequency of the cavity modes, while the eigenvectors allow the reconstruction of the fields. The capability of the fully vectorial treatment to experience the tensorial nature of the dielectrical permittivity is exploited to analyze in detail the consequences of the elasto-optic effect in VCSELs with reference to modal frequencies, gains and profiles.

Modal frequencies of vertical-cavity lasers determined by an effective-index model

Previously, an effective-index optical model was introduced for the analysis of lateral waveguiding effects in vertical-cavity surface-emitting lasers. We show that the resultant transverse equation obtained in that model is almost identical to the one typically obtained in the analysis of dielectric waveguide problems, such as a step-index optical fiber. In this letter, we extend the effective-index model to obtain predictions of the discrete frequencies of the microcavity modes. As an example, we apply the analysis to vertical-cavity lasers that contain thin-oxide apertures. The model intuitively explains our experimental data and makes quantitative predictions in good agreement with a highly accurate numerical model.

Misaligned anisotropies and nonlinear polarization effects in vertical-cavity surface-emitting lasers

We investigate the polarization properties of light emitted by vertical-cavity surface-emitting semiconductor lasers, determining the effects of nonlinearities due to the interaction between the light and the active material. We demonstrate that a VCSEL can operate in (i) a quasi-linear regime in which these nonlinearities play a minor role and (ii) a nonlinear regime in which they strongly affect the polarization characteristics of the light beam. The conditions which maximize the action of the system nonlinearities and the corresponding deviations from linearity are derived analytically.

Measurement of guiding effects in vertical-cavity surface-emitting lasers

Wave-guiding mechanisms in large area InGaAs-GaAs MQW vertical-cavity surface-emitting lasers (VCSELs) have been investigated using novel spatially and spectrally resolved measurements of spontaneous and stimulated emission. Carrier induced anti-guiding is found to be important despite the presence of other guiding mechanisms.

Self-consistent approach to thermal effects in vertical-cavity surface-emitting lasers

A self-consistent theory for semiconductor lasers, in which plasma and lattice temperatures are treated as two independent variables, is presented. This theory consists of a set of coupled equations for the total carrier density, field amplitude, and plasma and lattice temperatures with the coupling that is due to phonon-carrier scattering and to the band gap’s dependence on lattice temperature. The self-consistent theory is then employed to study thermal effects in vertical-cavity surface-emitting lasers. We first investigate the plasma heating by solving the stationary (cw) solution of the set of equations with a fixed lattice temperature. The solution is studied systematically with respect to different parameters for both bulk and quantum-well media. Significant plasma-heating effects are found. These include the carrier-density dependence on pumping, decrease of input–output efficiency, dependence of the cw frequency shift on pumping, and a pronounced Pauli-blocking effect that is due to plasma heating. Furthermore, we solve the whole set of equations, including that for lattice temperature. We show that the output power is strongly saturated or switched off with an increase of pumping. Details of the saturation depend on the position of the cavity frequency in the gain spectrum and on the heat transfer rate from the lattice to the ambient.

Effective index model for vertical-cavity surface-emitting lasers

A new effective index optical model is presented for the analysis of lateral waveguiding effects in verticalcavity surface-emitting lasers. In addition to providing a concise formalism for reducing the dimensionality of the Maxwell equations describing the lasing mode, this model also provides new insights into waveguiding phenomena in vertical-cavity lasers. In particular, it is shown that the effective index responsible for waveguiding is dependent only on lateral changes in the Fabry-Perot resonance frequency. This concept leads naturally to new design methods for these lasers that are expected to result in more eff icient devices with superior modal characteristics.