Abstract Using tightly focused ultrashort laser pulses allows the direct writing of three-dimensional photonic structures in different glasses and also crystalline media. One of the main drawbacks of this technology is, however, the limited writing speed achieved so far. In this paper we shall review our recent advances in the direct writing of three-dimensional integrated-optical devices and discuss a new approach using a fibre-based femtosecond laser system producing 300 fs pulses with pulse energies of 0.6 μJ at 2 MHz repetition rate. Using this laser system we fabricated low-loss waveguides (less than 0.5 dBcm?1) at writing speeds of 100 mms?1 for the first time. The influence of the writing speed on the produced structures as well as their optical properties will be discussed in detail. 相似文献
Different types of alkynes were reacted with 2,5‐disubstituted furans in order to evaluate the scope of the intermolecular furan‐yne reaction. With ethynyl aryl ethers as starting materials, 2‐phenoxy phenols were accessible in moderate to good yields. A different reaction mode was observed for alkynes bearing electron‐withdrawing substituents. For these starting materials a cis‐selective hydroarylation took place in an anti‐Markovnikov fashion in excellent yields. 1,2‐Diynes turned out to be suitable starting materials as well. Due to the second alkynyl moiety, after an initial phenol synthesis, a subsequent hydro‐alkoxylation by the newly formed phenolic oxygen gives access to benzofurans in a tandem process.