Semiconductor Devices for Control of Laser Dynamics

十多年来，半导体可饱和吸收体已在实验室中非常成功地用于各种固态和光纤激光器的锁模。 在这个项目中，将研究两种用于控制激光动力学的新型半导体器件。 第一个器件是用于激光器锁模的传统半导体可饱和吸收镜的扩展，通过将其与附加的光学可控调制器集成，例如通过自由载流子吸收。即使激光器没有Q开关，吸收体也必须强烈饱和，即取决于激光器设计甚至超过十倍的饱和能量，以抑制这种不期望的Q开关。 然而，这种操作对吸收器施加了沉重的热负荷，这降低了其寿命。 因此，该提案的第一个目标是证明吸收器不仅控制锁模，而且还控制激光器的Q开关。 这种器件能够抑制不期望的Q开关，这通常发生在可饱和吸收体锁模激光器中，并大大降低了吸收体的寿命。有了这些吸收器，激光系统可以在连续或调Q锁模制度独立于其他激光参数，如泵浦功率，重复率，输出功率，模式体积，上态寿命等，在这个项目中，该设备将被应用于高重复率激光器的锁模。该研究项目的第二个目标是寻找全新的控制元件，即半导体器件，能够直接从激光输出中检测脉冲的绝对光学相位。 这样的装置允许对几个周期的激光脉冲和绝对光学相位对其超敏感的相关量（诸如腔内脉冲能量）进行相位控制。具体来说，我们要调查是否最近发现的载波rabi-flopping在GaAs中，这也应该发生在其他材料系统，可以用来构建一个光学相位检测器。通过所设想的设备对固态激光器动力学控制的改进将使新一代更紧凑、稳定和可靠的激光源具有扩展的参数范围，例如更高的重复率和更高的功率处理能力。 此外，这些器件将导致全新一代的少周期激光源，其中可以控制从振荡器直接发射的激光脉冲的绝对光学相位。 这在频率计量和强场超快激光物理中有广泛的应用。 该项目之所以成为可能，是因为各小组之间的密切合作，这些小组提供了设备制造所需的材料科学专业知识，并能够在先进的激光系统中表征和测试设备。

For over a decade semiconductor saturable absorbers have been used very successfully in laboratories to modelock a variety of solid-state and fiber lasers. In this project, two new semiconductor devices for control of laser dynamics shall be investigated. The first device is an extension of the conventional semiconductor saturable absorber mirror used for modelocking of lasers by integrating it with an additional optically controllable modulator, for example by free carrier absorption. Even if the laser does not Q-switch, the absorber has to be saturated strongly, i.e. depending on the laser design by even more than ten times the saturation energy, to suppress this undesired Q-switching. However, such operation puts a heavy thermal load on the absorber, which reduces its lifetime. Therefore, the first goal of this proposal is to demonstrate absorbers that do not only control the mode locking but in addition the Q-switching of the laser. Such a device is able to suppress the undesired Q-switching, which often occurs in saturable absorber modelocked lasers and greatly reduces the life time of the absorber. With these absorbers a laser system can be operated in the continuous or Q-switched mode-locked regime independent of its other laser parameters such as pump power, repetition rate, output power, mode volume, upper-state lifetime, etc. In this project, the device will be applied to modelocking of high-repetition rate lasers. The second goal of this research project is to search for entirely novel control elements, i.e. semiconductor devices, that are able to detect the absolute optical phase of the pulses directly from the laser output. Such devices allow for phase control of few-cycle laser pulses and related quantities to which the absolute optical phase is ultra-sensitive, such as the intracavity pulse energy. Specifically, we want to investigate whether the recently discovered carrier-wave rabi-flopping in GaAs, which should also occur in other material systems, can be used to construct an optical phase detector. The improvement in control of solid-state laser dynamics by the envisioned devices will enable a new generation of more compact, stable and reliable laser sources with extended parameter ranges such as higher repetition rates and higher power handling capabilities. In addition, these devices will lead to a completely new generation of few-cycle laser sources, in which the absolute optical phase of the laser pulse directly emitted from the oscillator can be controlled. This has a broad range of applications in frequency metrology and strong-field ultrafast laser physics. The project is only possible because of the close cooperation between groups, which provide the know-how in material science necessary for device fabrication and groups that are able to characterize and test the devices in advanced laser systems.