Showing papers by "Luis Pesquera published in 1999"

Terahertz bandwidth prediction for amplitude modulation response of unipolar intersubband semiconductor lasers

Abstract: An analysis is performed of the direct-current (dc) amplitude modulation response of unipolar intersubband semiconductor lasers. It is shown that unipolar lasers have the potential for achieving terahertz dc modulation bandwidths.

Transverse-mode selection and noise properties of external-cavity vertical-cavity surface-emitting lasers including multiple-reflection effects

Abstract: A theoretical analysis has been undertaken of steady-state transverse-mode selection in vertical-cavity surface-emitting lasers (VCSEL’s) that are subject to optical feedback in an external-cavity configuration. Multiple reflections in the external cavity are taken into account. The influence of thermal effects on mode selection is also treated, and noise properties of the configuration are discussed. In the analysis specific attention is paid to the competition between the two lowest-order modes (LP01 and LP11 degenerate modes) that are appropriate to the chosen circularly symmetric vertical-cavity surface-emitting laser structure. It is shown that preferential excitation of either mode can be effected by the appropriate choice of optical feedback delay. It is also shown that multiple reflections in the external cavity can affect the mode selection, depending on the optical feedback delay. Thermal effects are shown to be detrimental for transverse-mode selection. Strategies for the minimization of thermal effects on mode selection are also discussed. Finally, the relative intensity noise spectrum for each transverse mode is shown to maintain its double-peaked structure and low mode-partition noise in the presence of optical feedback. A change from a twin-peaked to a single-peaked structure of this spectrum is also observed when the optical feedback delay is changed.

Relative intensity noise of multitransverse mode vertical cavity surface emitting lasers

Abstract: Summary form only given. Relative intensity noise (RIN) in vertical cavity surface emitting lasers (VCSELs) is important for applications in communications and optical interconnections. It is known that VCSELs tend to lase at high powers in multiple transverse modes due to spatial hole burning (SHE). This behavior can increase the RIN and limit the usefulness of VCSELs in high-speed communications. In the paper it is found that low RIN operation can be maintained for low spatially overlapping modes.

Mode partition noise in multi-transverse mode vertical-cavity surface-emitting lasers

Abstract: Relative intensity noise spectra of weakly index guided VCSELs in a multi—transverse mode regime are analyzedby using a model that takes into account all the transverse modes supported by the waveguide. Several resonancepeaks are obtained in the noise spectra that correspond to the relaxation oscillation frequencies of the transverse modes. In is shown that for low spatially overlapping transverse modes, low RIN operation can be maintained. However, the excitation of transverse modes with a significant mode overlap leads to a clear enhancement of theRIN at low frequencies. Keywords: Semiconductor Lasers, Vertical cavity lasers, Transverse modes, Relative Intensity Noise 1. INTRODUCTION Vertical-cavity surface-emitting lasers (VCSELs) are highly attractive light sources for applications in intercon- nections and optical communications, because of their useful characteristics such as single longitudinal modeoperation, low threshold current, circular output beam, and wafer scale integration.'2 An important consider-ation for such applications of VCSELs is the understanding of their noise characteristics. Several experimentalstudies of the relative intensity noise (RIN) in VCSELs have been performed.39 In general the noise perfor-inance of VCSELs operating in the fundamental mode is comparable to that of edge emitting lasers. However,

High-frequency beam steering in vertical-cavity surface-emitting lasers: optical gain and waveguiding effects

Abstract: Static and dynamic characteristics of weakly index-guided vertical-cavity surface-emitting lasers in a multi-transverse-mode regime are analyzed by use of a model that takes into account the transverse modes supported by the waveguide and a consistent spectral gain including many-body effects. Waveguide effects are addressed by consideration of different refractive-index steps. We show that stronger competition between transverse modes occurs when their confinement in the waveguide is increased. Selection of a particular high-order transverse mode by use of azimuthal-dependent current profiling can be obtained over a wide current range. We study the alternate current modulation of two orthogonal high-order transverse modes, taking into account thermal effects. This current-induced spatial switching leads to good-quality high-frequency beam steering in the laser azimuthal direction when an appropriate current profile is considered according to the refractive-index step.

High-frequency beam steering induced by transverse mode switching in VCSELs: optical gain effects

Abstract: Static and dynamic characteristics of weakly index guided VCSELs in a multi-transverse mode regime are analyzed by using a model that takes into account all the transverse modes supported by the waveguide and a consistent spectral gain including many-body effects. Selection of a particular high order transverse mode by using azimuthal dependent current profiling can be obtained over a wide current range. The alternate current modulation of two orthogonal high order transverse modes is studied taking into account thermal effects. This current induced spatial switching leads to high frequency beam steering in the laser azimuthal direction.

Transverse mode selection and light-current characteristics in index-guided VCSELs

Abstract: The recent rapid advances in the performance of vertical cavity surface emitting lasers (VCSELs) give significant impetus to identifying practical applications of these devices in, for example, optical data links and two-dimensional optical switching. In looking towards such applications serious consideration must be given to basic device performance characteristics and specifically to their operating efficiencies, threshold currents and transverse mode structures. Recent work has indicated the role of spatial hole-burning effects in determining both the transverse mode structure and the wall-plug efficiencies of gain-guided VCSELs. We show that the strength of the in-built transverse mode waveguide in index-guided VCSELs exerts a dramatic influence on the excitation of transverse modes. The influence is, in particular, revealed by calculated light-current characteristics of index guided VCSELs.

Analysis of bit error rate of an optical clock extraction system based on self pulsating laser diodes

Abstract: A theoretical analysis of the bit error rate (BER) in an optical clock extraction system using compact disk self-pulsating laser diodes (SPLDs) is performed. The dependence of the BER on the power of the incoming received data signal and on the detuning between the applied and free running SPLD pulse repetition frequencies is analysed. For a fixed detuning an optimum value of the input signal power at which the system BER is minimum is obtained. This minimum is due to the appearance of oscillations of the relative phase between the input and output signals at high values of the input power. An optimum value of the detuning at which the system BER is minimized is then identified. The influence of fluctuations of the input signal and data encoding on the system BER is also analysed.

Relative intensity noise of unipolar intersubband semiconductor lasers

Abstract: Intersubband lasers have become a topic of active research particularly following the development of mid-infrared quantum cascade lasers [1].