| Abstract |
Tunable semiconductor laser diodes are of great technological interest to a variety of fields such as telecommunication and chemical analysis. Contemporary tunable laser diodes offer solutions that cover the necessary tunability range, as well as performance characteristics (such as tuning speed, single mode operation e.t.c.) at the expense of excessive complexity both in fabrication as well as in operation.
In this thesis we explore a new concept that may lead to simple yet high performance tunable edge emitting laser diodes. For the first time we investigate the behavior of LD's operating with dynamically created electric fields in the active layer. This offers a series of unique characteristics ranging from reduced operating threshold all the way to ultra fast, broad range tunability utilizing the quantum confined Stark effect. In this class of devices, tunability is obtained by directly varying the gain current of the device.
This thesis dealt with three main issues concerning tunable laser diodes.
Initially, a thorough investigation of structure design and growth issues was performed leading to high quality semiconductor structure optimized for edge emitting laser diodes device fabrication. Besides a broad range of experimental methods necessary for semiconductor characterization, a set of theoretical tools were also developed to fully optimize these structures. Laser structure on polar as well as non polar orientations were investigated so as to understand and explore the effects of electric fields present in LD's. Subsequently the fabrication of edge emitting laser diodes was investigated and optimization of the process was carried out leading to state of the art devices.
Finally, the knowledge gained from the initial parts of this thesis were combined with the novel idea of dynamic electric fields to provide tunable edge emitting laser diodes.Τunable semiconductor LD's were successfully demonstrated based on the concept of dynamic electric fields in the active region of these devices. A record high, low temperature, emission wavelength tuning reaching 20nm tuning at 980nm was demonstrated. For the first time room temperature tunability was achieved and a device exhibiting more than 5nm tuning range was demonstrated using the above mentioned technique. To conclude, the physical mechanism causing temperature degradation of the tuning characteristics was elucidated pointing the way to further improvement of the tuning characteristics of these devices.
|
Κατασκευή και μελέτη διόδων laser με μεταβλητό εσωτερικό ηλεκτρικό πεδίο
