Diamantbasierte Raman-Oszillatoren

High-power laser sources have essential applications in the fields of industry and research. However, the spectral gain of the active medium often limits the output power of highly demanded laser sources at uncommon wavelengths. Driven by higher requirements of industry and science, laser sources with process-optimized emission wavelengths represent a key technology in our society. Among other systems, Raman lasers provide an excellent technology to shift and adapt the emission spectrum to the process. These are less complex than comparable systems based on other nonlinear effects such as optical parametric gain. In this work, high-performance diamond-based Raman oscillators are developed and realized in double and single resonant operation to shift the emissions spectrum into the infrared range. Furthermore, parasitic nonlinear effects are shown and a method of their suppression is presented. Two different fiber-based lasers were developed for oscillator operation, which were used as pump sources for the Raman frequency converters. Both pump Wavelength 1060 nm and 1018 nm and the corresponding Raman frequency converters were used to shift the output spectrum into the infrared range. Going beyond the state of the art, high continuous wave power of 105Wat 1234 nm and 56Wat 1178 nm were shown for the single resonant Diamond- Raman-Oscillator. Furthermore, a double resonant system was developed to shift the emission spectrum even further into the infrared range to 1477 nm. The Raman oscillators have been characterized at high powers in a modulated and continuous mode operation. In particular, the transient behavior of the double-resonant oscillator was investigated. Here, an unstable behavior strongly dependent on the resonator length and the power range was found. In addition, upcoming intense pulse trains and spectral broadenings were investigated

Reconfigurable Si Nanowire Nonvolatile Transistors

Reconfigurable transistors merge unipolar p- and n-type characteristics of field-effect transistors into a single programmable device. Combinational circuits have shown benefits in area and power consumption by fine-grain reconfiguration of complete logic blocks at runtime. To complement this volatile programming technology, a proof of concept for individually addressable reconfigurable nonvolatile transistors is presented. A charge-trapping stack is incorporated, and four distinct and stable states in a single device are demonstrated

Feasibility and performance study for a space-borne 1645nm OPO for French-German satellite mission MERLIN

We present a theoretical and experimental analysis of a pulsed 1645 nm optical parametric oscillator (OPO) conducted to prove the feasibility of such a device for a spaceborne laser transmitter in an integrated path differential absorption (IPDA) lidar system. The investigation is part of the French-German satellite mission MERLIN (Methane Remote Sensing Lidar Mission). As an effective greenhouse gas, methane plays an important role for the global climate. The architecture of the OPO is based on a conceptual design developed by DLR, consisting of two KTA crystals in a four-mirror-cavity. One of the cavity mirrors is piezo-driven to provide single frequency operation of the OPO. Using numerical simulations, we studied the performance and alignment tolerances of such a setup with KTP and KTA and investigated means to optimize the optical design by increasing the efficiency and decreasing the fluence on the optical components. For the experimental testing of the OPO, we used the INNOSlab-based ESA pre-development model ATLAS as pump laser at 1064 nm. At a pulse frequency of 25 Hz this MOPA delivers a pump energy up to 45 mJ with a beam quality factor of about M² = 1.3. With KTP as nonlinear crystal the OPO obtained 9.2 mJ pulse energy at 1645 nm from 31.5 mJ of the pump and a pump pulse duration of 42 ns. This corresponds to an optical/optical efficiency of 29%. After the pump pulse was reduced to 24 ns a similar OPO performance could be obtained by adapting the pump beam radius