As part of the European Space Agency's AEOLUS mission, the global wind distribution in the atmosphere is currently being measured with a satellite based Doppler lidar. For the AEOLUS-2 mission, a more powerful laser is required which can emit single frequency pulses of 150 mJ energy at a pulse repetition rate of 50 Hz and a wavelength of 355 nm. Fraunhofer ILT is currently developing an engineering model of the laser beam source in cooperation with Airbus Defense and Space Germany. The work on the laser housing and heat removal system is performed by Airbus whereas the work on the laser opto-mechanical assembly is performed by ILT. This work is based on the results of previous projects and focuses on maximizing the use of heritage: The required optical parameters in the infrared have been validated by means of a breadboard demonstrator within the NIRLI project and the optomechanical platform suitable for AEOLUS-2 has been developed in the frame of the OPTOMECH, FULAS and MERLIN projects. For the engineering model presented in this article the proven optical design supplemented by a frequency tripling unit is transferred to the proven and to a large extent space qualified optomechanical platform with an adapted heat removal system. The design is ready, pending the detailed review.
For specific indications in neurosurgery, such as the removal of brain tumors in eloquent locations and the deep brain stimulation, awake craniotomy offers multiple advantages. However, due to the severe discomfort experienced during burr-hole drilling, patients are hesitant to opt for awake craniotomy. Laser systems provide an alternative to surgical drills as a silent and vibration-free bone cutting method. Until now no laser system achieved adequate ablation rates (> 2:5mm3/s) at sufficiently high aspect ratio (>5) to fulfill the requirements for craniotomy. The aim of this study is to investigate the ablation of bone tissue under the needs for neurosurgery using three different Q-switched infrared laser sources assisted by a water spray system. One of the laser sources is a commercial Q-switched CO2 laser system operating at 10:6 μm with a pulse energy of 4 mJ. In addition, two in-house developed, short-pulsed IR-laser sources operating at 2:91 μm (Cr:ZnSe) with a pulse energy of 0:76mJ and at 1:9 μm (Tm:YLF) with a pulse energy of 2:2mJ are investigated. The results show that highly efficient bone ablation with the CO2 laser at rates of 6mm3/s is possible without carbonization. With an ablation strategy using the effect of multiple reflections inside the kerf an aspect ratio of 17 was achieved for narrow incisions at widths smaller than 100 μm. Another ablation strategy shows a twofold higher ablation depth shifting the laser focus stepwise into propagation direction. Even though a high ablation efficiency can be achieved with the Cr:ZnSe laser source and the CO2 laser source, the Cr:ZnSe laser cannot fulfill the required ablation rates. The CO2 laser shows a fast ablation in significant depth with a maximum depth of 7 mm. Further investigations will concentrate on increasing the ablation depth to 10 mm.
Based on our study of a high stability ultra-narrow linewidth fiber amplifier for the gravitational wave detector LISA, we have set up a hybrid fiber and Innoslab amplifier for further power scaling into <100 Watt regime. The fiber amplifier can provide a seed power of up to 8 W at 1064 nm and a linewidth <10 kHz. The booster stage consists of an in-band pumped Innoslab amplifier, which is pumped by stabilized laser diodes at 880 nm. An output power of 437 W has already been demonstrated with almost diffraction-limited beam quality. Further investigations of power stability and modal properties are currently ongoing.
We report an in band pumped single-stage 410 W INNOSLAB laser amplifier based on Nd:YVO4. VBG stabilized diodes are used to pump the crystal from both end faces at 880 nm wavelength. At 3 W@800KHz input power and a pulse duration of 300 ps an extraction efficiency of 44% is achieved. A beam quality of M2<1.5 (4-Sigma Method) and M2<1.3 (10/90 Knife Edge Method) is measured over the whole power range. The output beam is free of self-lasing or CW-background.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.