Endoscopic laser surgery (ELS) is a class of minimally invasive surgical procedures used for treating head and neck conditions, such as laryngeal cancer. The main characteristic of ELS is the use of a fiber laser tool, which allows performing incisions on difficult to reach surgical sites. This avoids the need for highly invasive open surgeries.
To achieve high precision, traditional laser systems use optics to focus the laser beam into a sub-millimeter laser spot. However, this is not the case with fiber laser tools, since the limited space of endoscopic systems makes difficult to integrate advanced optics. In fiber laser tools, the fiber tip is placed very close to the tissue to be ablated to minimize the laser spot size. Nonetheless, due to beam divergence, the laser spot is slightly larger than the core of the fiber. This reduces the precision and quality of the ablation, often leading to undesired thermal damage to surround tissue.
To avoid thermal damages and tissue carbonization, we seek to develop a fiber laser tool capable of performing focused ablation. The major challenge of this is ensuring that the laser spot will be focused on the target tissue while the surgeon manipulates the tool. Without the visual feedback of near-contact ablation, adjusting the distance between the tool and the tissue becomes difficult, making the operation of the tool less intuitive and increasing the mental workload of the surgeon. To solve these problems, we are developing a compact optical system capable of automatically adjusting its focal length to match the distance to the target tissue.
To allow miniaturization and integration with an endoscopic laser tool, our focusing system is based on MOEMS (Micro-Opto-Electro-Mechanical Systems) devices, such as a varifocal mirror. A varifocal mirror is a thin membrane mirror, which can be mechanically deformed in order to change its curvature and consequently its focal length. Similar devices have been developed for imaging applications, but not for high-power lasers. Therefore, the key component of this project is the development of novel MOEMS devices specifically designed for high-power laser focusing.