E.E. Ashkinazi

External-cavity diamond Raman laser performance at 1240 nm and 1485 nm wavelengths with high pulse energy

We report on an external-cavity diamond Raman laser (DRL) pumped with a Q-switched Nd:YAG and generating at 1st and 2nd Stokes (1240 nm and 1485 nm) with enhanced output energy. The slope efficiency of 54% and output energy as high as 1.2 mJ in single pulse at 1240 nm have been achieved with optimized cavity, while the pulse energy of 0.70 mJ was obtained in the eye-safe spectral region at 1485 nm. Calculations of thermal lensing effect indicate it as a possible reason for the observed decrease in conversion efficiency at the highest pump energies.

Growth of three-dimensional diamond mosaics by microwave plasma-assisted chemical vapor deposition

We realized the growth of a novel type of diamond mosaic crystal by chemical vapor deposition of a diamond layer on tightly placed oriented seed substrates, using a combination of seeds of different heights to form a three-dimensional structure. Here, a simple T-shaped mosaic is demonstrated as a proof of the principle. The 3D mosaic was epitaxially grown by microwave plasma CVD on (100)-oriented 3 × 3 × 1 mm3 type Ib HPHT diamond substrates arranged horizontally and vertically. Very straight and sharp junctions between the vertical and horizontal parts were observed and characterized with SEM. Confocal Raman spectroscopy mapping of the CVD diamond layer revealed only a narrow (∼20 μm wide) zone of enhanced defect abundance and/or non-uniform stress, if any, around the junction. The Raman and photoluminescence mapping of the mosaic’s cross-section gave further information on the spatial distribution of the epilayer with a thickness of up to 200 μm. The work demonstrates diamond growth on both sides of the vertically positioned seed plate, with a film thickness variation of less than 25%, thus doubling the diamond mass uptake achieved with the CVD process. The developed technique clears the way for the design and growth of various complex diamond shapes.