<p>This report has been written at SAAB Bofors Dynamics (SBD) AB in Gothenburg at the department of optronic systems.</p><p>In military observation operations, a target to hit is chosen by illumination of a laser designator. From the targetpoint laser radiation is reflected on a detector that helps identify the target. The detector is a semiconductor PIN-type that has been investigated in a laboratory environment together with a specially designed laser source. The detector is a photodiode and using purchased components, circuits for both the photodiode and the laserdiode has been designed and fabricated. The bandwidth of the op-amp should be about 30 MHz, in the experiments a bandwidth of 42 MHz was used. Initially the feedback network, which consists of a 5.6 pF capacitor in parallel with a 1-kohm resistor determined the bandwidth. To avoid the op-amp saturate under strong illuminated laser radiation the feedback network will use a 56-pF capacitor and a 100-ohm resistor respectively.</p><p>The laser should be pulsed with 10-20 ns width, 10 Hz repetition frequency, about 800 nm wavelength and a maximum output power of 80 mW. To avoid electrical reflection signals at measurement equipment connections, the laser circuit includes a resistor of about 50 ohm, that together with the resistance in the laserdiode forms the right termination that eliminate the reflection signals. The wire-wound type of resistor shall be avoided in this application and instead a surface mounted type was beneficial with much lower inductance. The detector showed a linear behaviour up to 40-mW optical power. Further investigation was hindered by the breakdown of the laserdiodes. The function generator limits the tests to achieve 80 mW in light power. In different experiments the responsivity of the photodiode is different from the nominal value, however it would have required more time to investigate the causes.</p>

This report has been written at SAAB Bofors Dynamics (SBD) AB in Gothenburg at the department of optronic systems. In military observation operations, a target to hit is chosen by illumination of a laser designator. From the targetpoint laser radiation is reflected on a detector that helps identify the target. The detector is a semiconductor PIN-type that has been investigated in a laboratory environment together with a specially designed laser source. The detector is a photodiode and using purchased components, circuits for both the photodiode and the laserdiode has been designed and fabricated. The bandwidth of the op-amp should be about 30 MHz, in the experiments a bandwidth of 42 MHz was used. Initially the feedback network, which consists of a 5.6 pF capacitor in parallel with a 1-kohm resistor determined the bandwidth. To avoid the op-amp saturate under strong illuminated laser radiation the feedback network will use a 56-pF capacitor and a 100-ohm resistor respectively. The laser should be pulsed with 10-20 ns width, 10 Hz repetition frequency, about 800 nm wavelength and a maximum output power of 80 mW. To avoid electrical reflection signals at measurement equipment connections, the laser circuit includes a resistor of about 50 ohm, that together with the resistance in the laserdiode forms the right termination that eliminate the reflection signals. The wire-wound type of resistor shall be avoided in this application and instead a surface mounted type was beneficial with much lower inductance. The detector showed a linear behaviour up to 40-mW optical power. Further investigation was hindered by the breakdown of the laserdiodes. The function generator limits the tests to achieve 80 mW in light power. In different experiments the responsivity of the photodiode is different from the nominal value, however it would have required more time to investigate the causes.

Universiẗat, Diss., 2002--Bremen.

Universiẗat, Diss., 2002--Heidelberg.

University, Diss., 2002--Bremen.

In dieser Dissertation werden verschiedene Methoden zur Simulation der Dynamik der optischen Moden einer Fabry-Pérot-Laserdiode diskutiert. Experimentell lässt sich hierbei der Effekt des Modenrollens oder Modenhüpfens beobachten. Hier sind zu einem gegebenem Zeitpunkt nur ein oder zwei longitudinale Moden aktiv, dabei wechseln sich die Moden in einem bestimmten Wellenlängenbereich ab. Eine Erklärung für diesen Effekt sind Vibrationen der Ladungsträgerdichten in den aktiven Schichten bzw. den Quantenfilmen. So werden in der ersten betrachteten Methode die Ladungsträgerdichten bzw. die Besetzungsfunktionen zunächst als ortsabhängig betrachtet, um die Ladungsträger-Vibrationen direkt zu bestimmen. Bei diesem Vorgehen wird eine hohe Rechenzeit benötigt, welche bei einer anderen Methode mithilfe eines effektiven Modenwechselwirkungsterms allerdings erheblich reduziert wird. Im ersten Teil dieser Arbeit wird gezeigt, dass diese beiden Methoden sehr ähnliche Ergebnisse liefern, außerdem wird der effektive Modenwechselwirkungsterm unter Berücksichtigung verschiedener Streuprozesse hergeleitet. Bei Strukturen mit mehreren Quantenfilmen oder größeren Stegbreiten spielt der Transport der Ladungsträger von den Kontakten zu den Quantenfilmen eine große Rolle, welcher in dieser Arbeit mithilfe der Drift-Diffusions-Gleichungen untersucht wird. Abschließend wird die Modendynamik mithilfe des Traveling-Wave-Modells simuliert. Im Gegensatz zu den bisher in dieser Arbeit verwendeten Methoden wird das optische Feld hierbei nicht mehr in die einzelnen Moden aufgeschlüsselt, sondern es wird partielle Differentialgleichung gelöst. / In this thesis different methods for the simulation of the mode dynamics in Fabry-Pérot laser diodes are discussed. These laser diodes show the effect of mode rolling, where the currently active longitudinal mode changes over time. This effect can be observed experimentally and can be explained by beating vibrations of the carrier densities in the quantum wells. In the first method used in this work the location dependence of the carrier densities and the distribution functions is considered. This procedure requires a lot of computing time, which is significantly reduced in another method using an effective mode interaction term. In the first part of this thesis it is shown that these two methods give very similar results, and the effective mode interaction term is derived taking into account various scattering processes. For structures with multiple quantum wells or broad ridge widths the transport of the charge carriers from the contacts to the quantum wells is important, which is examined in this work using the Drift-diffusion equations. Finally, the mode dynamics is simulated using the traveling wave model. In contrast to the methods used so far in this work the optical field is no longer broken down into the individual modes, instead a partial differential equation is solved.