Åsa Marie Lindberg

Observations on the dynamics of semiconductor lasers subjected to external optical injection

We report on the experimental investigation of the dynamics of semiconductor lasers subjected to external optical injection. We have mapped the nonlinear regions in the parameter space consisting of the detuning between the master and slave lasers and the injection intensity. The map is based on optical and radio-frequency spectra sampled and collected continuously as one parameter is changed while the other is fixed. The chaotic oscillations of the slave laser can clearly be seen to form distinct regions in the map. Within the chaotic regions islands of periodic oscillation are found.

Experiments on the Linewidth-Enhancement Factor of a Vertical-Cavity Surface-Emitting Laser

Nine different experimental techniques for measuring the linewidth-enhancement factor alpha are discussed and tested on a single 760-nm vertical-cavity surface-emitting laser. Techniques included in the comparison are based on linewidth measurements, current modulation, optical injection, and optical feedback

Periodic oscillation within the chaotic region in a semiconductor laser subjected to external optical injection

We report on the experimental observation of periodic windows within the chaos of the output of a semiconductor laser that is subjected to external optical injection. Continuously sampled spectra of the slave-laser output as the injection level is increased reveal the general behavior of the system as well as features that suggest that the periodic oscillation forms a distinct island within the chaotic region in the parameter space.

Modulation and the linewidth enhancement factor of a diode-pumped Nd:YVO 4 laser

A technique based on an FM/AM method is proposed for measuring the linewidth enhancement factor a of a diode-pumped Nd:YVO4 laser. A standard rate equation model is complemented with temperature effects to explain the observed behavior under pump modulation. The result alpha = 0.25 +/- 0.13 agrees with values deduced from recent optical injection experiments.

A Vertical-Cavity Surface-Emitting Laser at Threshold

Linewidth is measured over the threshold transition of a vertical-cavity surface-emitting laser and results are compared to a Fokker-Planck semiconductor laser model. The linewidth shows nonmonotonous behavior at threshold similar to that previously observed in distributed feedback lasers. The behavior agrees with the Fokker-Planck model if the linewidth enhancement factor alphaap5.0. Measurement of the relaxation oscillation frequency and the damping rate using an injected optical probe allows, together with the Fokker-Planck model, the extraction of major laser parameters

Noise Correlation, Regenerative Amplification, and the Linewidth Enhancement Factor of a Vertical-Cavity Surface-Emitting Laser

This letter reports on amplitude and frequency noise correlation measurements as well as on optical injection experiments related to the linewidth enhancement factor a of a vertical- cavity surface-emitting laser (VCSEL). It is shown that the correlation in VCSELs is not dominated by alpha; consequently, such experiments yield very little information on its value. Measuring the regenerative amplification of a weak injected optical probe turned out to be a robust approach that can not only give accurately the relaxation oscillation frequency and the damping rate but a good estimate of alpha as well. Finally, these experiments are combined with previously published data to increase the number of techniques applied to the measurement of alpha of a single semiconductor laser up to 11.

Mapping the dynamics of an optically injected solid state laser

Experimental and simulated maps describing dynamical regions of an injected solid state laser are demonstrated and found to be in excellent agreement with each other with a value of /spl alpha/ = 0.4 for the Nd:YVO/sub 4/ laser. Both experimental estimate for /spl alpha/ and an experimental map of the dynamics with injection are presented for the first time for a solid state laser.

Dynamics, bifurcations and chaos in coupled lasers

Experiments and numerical modelling on two different class B lasers that are subjected to external optical light injection are presented. This presentation includes ways of measuring the changes in the laser output, how to numerically describe the systems and how to construct diagrams of the dynamical states in the plane frequency detuning between lasers and injection strength. The scenarios for the semiconductor laser include an area of frequency locking and islands of chaotic behaviour embedded in and mixed with periodic doubling regimes. Using a rate equation model, the largest Lyapunov exponent is calculated as a measure of the stability of equilibriums and the amount of chaos in chaotic regimes. In the solid-state laser case, different dynamical regions were clearly observed. The found boundaries were identified experimentally, using an identification method, and numerically, from bifurcation analysis, as Hopf, saddle-node, period-doubling and torus bifurcations.

Nonlinear dynamics of semiconductor lasers subject to external optical injection

Summary form only given. External optical injection of coherent light into a semiconductor laser has received considerable attention recently. Many of the basic elements of nonlinear dynamics, such as a period-doubling route to chaos, have been observed in master-slave systems. This term refers to the situation in which the injection source is undisturbed by the light from the injected laser. We have recently reported on a new method of presenting optical spectra of the slave laser. Consecutively sampled spectra as the injection power is increased while the frequency detuning between lasers is fixed, are plotted next to one another with color representing intensity. We find variations including islands of periodic oscillation within the chaotic regions.

MAGNETO-OPTIC SPECTROSCOPY ON NEON USING LASER-INDUCED FORWARD SCATTERING

The forward-scattered light observed when a single-mode dye laser interacts with the three neon transitions 1s5(J = 2)-2ps(J = 2), 1s3(J = 0)-2p5(J = 1), and 1s4(J = 1)-2p7(J = 1) has been investigated as an applied longitudinal magnetic field is varied. The 1s5 and the 1s3 states are metastable. This condition allows a comparison of the spectra for the cases 1s5(J = 2)-2p8(J = 2) and 1s3(J = 0)-2p5(J = 1) in order to discuss whether the complex line shapes obtained for the J = 2 to J = 2 atomic system are due to higher-order coherences or whether they originate from coherences between m = ±1 states. Experimental and calculated line shapes are presented. The calculations have been performed with the use of a semiclassical model for the light/matter interaction. A J = 0 to J = 1 (or a J = 1 to J = 1) model reproduces the overall shapes of the recorded spectra for all three transitions. The results show that, even when laser beam spatial effects and the sample isotopic effects are taken into account, interpretations of forward-scattering spectra in order to determine atomic parameters can reliably be done for simple J = 0 to J = 1 systems only.