Generation of regular optical vortex arrays using double gratings

In order to generate high quality regular optical vortex array(OVA),we present an experimental method for generating OVA using phase only liquid crystal spatial light modulator(LC-SLM)assisted two gratings.In the scheme,holograms of two grating are displayed on the screen of two LC-SLMs respectively;the diffraction optical fields are captured by a CCD camera.The simulated and experimental results show that the regular OVA can be generated by using double diffraction gratings.The generated OVAs have a constant topological charge of±1.The method can provide a useful pathway to produce regular OVA for some applications in optical communication,particle trapping and optical metrology.

Narrow-wavelength-spread spectral combining laser with a reflector for a double pass with a single grating

We proposed a novel wavelength-spread compression technique for spectral beam combining of a diode laser array. A reflector, which is parallel to the grating, is introduced to achieve a double pass with a single grating.This facilitated the reduction of the wavelength spread by half and doubled the number of combined elements in the gain range of the diode laser. We achieved a power of 26.1 W under continuous wave operation using a19 element single bar with a wavelength spread of 6.3 nm, which is nearly half of the original wavelength spread of 14.2 nm, demonstrating the double-compressed spectrum capability of this structure. The spectral beam combining efficiency was 63.7%. The grating efficiency and reflector reflectance were both over 95%; hence, the efficiency loss of the double-pass grating with a reflector is acceptable. In contrast to double-grating methods,the proposed method introduces a reflector that efficiently uses the single grating and shows significant potential for a more efficient spectral beam combining of diode laser arrays.