Enhancement of the beam quality of non-uniform output slab laser amplifier with a 39-actuator rectangular piezoelectric deformable mirror.

We present a slab laser amplifier beam cleanup experimental system based on a 39-actuator rectangular piezoelectric deformable mirror. Rather than use a wave-front sensor to measure distortions in the wave-front and then apply a conjugation wave-front for compensating them, the system uses a Stochastic Parallel Gradient Descent algorithm to maximize the power contained within a far-field designated bucket. Experimental results demonstrate that at the output power of 335W, more than 30% energy concentrates in the 1x diffraction-limited area while the beam quality is enhanced greatly.

Retarded oxygen diffusion in heavily phosphorus-doped Czochralski silicon: experiments and first-principles calculations.

The effect of heavy phosphorus (P) doping on oxygen diffusion in Czochralski (Cz) silicon has been experimentally and theoretically investigated. It is experimentally found that the oxygen diffusion in heavily P-doped Cz silicon is retarded, with a diffusion activation energy which is ∼0.12 eV larger than that of its lightly P-doped counterpart. First-principles calculations suggest that the P-O complexes in the -P-Si-O-Si- configuration can form in heavily P-doped Cz silicon, leading to the trapping of interstitial oxygen (O(i)) atoms at the twelve equivalent second-nearest neighbors of the P atoms. Furthermore, the calculated increase of the oxygen diffusion activation energy, taking account of the trapping effect of such P-O complexes, is in accordance with the experimental result. This indicates that the retarded oxygen diffusion in the heavily P-doped Cz silicon can be ascribed to the trapping of O(i) atoms associated with the formation of the aforementioned P-O complexes.