Narrow-stripe Semiconductor Lasers Research Articles

Self-Pulsation Dynamics in Narrow Stripe Semiconductor Lasers

In this paper, we address the physical origin of self-pulsation in narrow stripe edge emitting semiconductor lasers. We present both experimental time-averaged polarization- resolved near-field measurements performed with a charged-coupled device camera and picosecond time resolved near-field measurements performed with a streak camera. These results demonstrate dynamic spatial-hole burning during pulse formation and evolution. We conclude from these experimental results that the dominant process which drives the self-pulsation in this type of laser diode is carrier induced effective refractive index change induced by the spatial-hole burning.

Self-Pulsation Dynamics in Narrow Stripe Semiconductor Lasers

In this paper, we address the physical origin of self-pulsation in narrow stripe edge emitting semiconductor lasers. We present both experimental time-averaged polarization-resolved near-field measurements performed with a charged-coupled device camera and picosecond time resolved near-field measurements performed with a streak camera. These results demonstrate dynamic spatial-hole burning during pulse formation and evolution. We conclude from these experimental results that the dominant process which drives the self-pulsation in this type of laser diode is carrier induced effective refractive index change induced by the spatial-hole burning.

How to have narrow-stripe semiconductor lasers self-pulsate

The rate equations of narrow-stripe semiconductor lasers are considered. These equations represent the dynamics of the photon number and the electron densities in the active and absorbing regions. Having the rate equations, (i) it is shown that the laser is the bounded-input bounded-state (BIBS) and the bounded-input bounded-output (BIBO) stable; (ii) the amplitudes of step inputs are determined for which all equilibrium points of the laser are unstable. The boundedness of the laser output and the instability of its equilibrium points imply that the laser can have a periodic, a quasi-periodic, or a chaotic output. When the output is periodic, the laser is self-pulsating, which is the desirable behavior of the laser. Moreover, a procedure is given to determine the values of laser parameters for which the laser self-pulsates.

Optical feedback on self-pulsating semiconductor lasers

Weak optical-feedback effects on the statistical properties of self-pulsations in narrow-stripe semiconductor lasers are analyzed using Lang-Kobayashi-type equations. The self-pulsation features are compared with the characteristics of excited relaxation oscillations. We determine the operating regime in which the randomizing effect of spontaneous-emission noise destroys pulse coherence. In this regime, only phase-insensitive effects of optical feedback are possible, and optimum jitter reduction is achieved with delay times of the order of an integer-odd multiple of the free-running pulsation period. In the high-pump operating regime, interpulse coherence is retained and the optical-feedback phase is shown to be instrumental for pulse-jitter control. Our results show that for cavity lengths up to 10 cm, variations on the order of half an optical wavelength induce jitter variations of one order of magnitude.

A theoretical analysis of self-sustained pulsation phenomena in narrow-stripe semiconductor lasers

Phenomena of the self-sustained pulsation are being utilized for reduction of the excess noise in the semiconductor injection laser. The generating mechanism of the self-sustained pulsation in semiconductor lasers having a narrow strip structure was theoretically analyzed. The pulsation is generated by the existence of the active region as well as the saturable absorbing regions located outside of the active region. The width of the active region (stripe width) should be narrower than several microns in a GaAs laser to get the pulsation. The gain guiding or the antiindex guiding with narrower active region is profitable to get higher operation keeping the pulsation. >

Lateral-mode analysis of narrow-stripe semiconductor lasers with a cylindrically concave end facet

A beam-propagation method is used to investigate numerically the lateral-mode characteristics of GaAlAs semiconductor lasers having a cylindrically concave facet at one end. Various degrees of index guiding have been considered. Simulations were made for both below- and above-threshold regimes. As expected, the numerical results show that the optical beam divergence parallel to the junction plane can be significantly reduced. In addition, this far-field narrowing is accompanied by lower threshold currents. However, for values of the radius of curvature of the concave facet lying in some specific ranges, the losses of the fundamental lateral mode are higher than that calculated for conventional lasers, and the corresponding eigenvalue shows nonmonotonic variations as the injection current is increased. This phenomenon is due to an enhancement of the index antiguiding over the gain-guiding mechanism. >

Circuit modeling of the effect of diffusion on damping in a narrow-stripe semiconductor laser

This paper describes a circuit modeling technique for directly modulated narrow-stripe semiconductor lasers with strong carrier confinement and index guiding. It is shown that diffusion damping of the modulation response, due to a nonuniform electron density distribution in the active layer, can be accounted for in terms of an equivalent optical gain saturation. Based on this equivalence, a small-signal ac circuit model of a narrow-stripe laser is derived. The model can be used to determine the intensity modulation and frequency modulation response characteristics of a packaged device.