5.6 μm quantum cascade lasers based on the Al0.78In0.22As/In0.69Ga0.31As active region composition with the measured pulsed room temperature wall plug efficiency of 28.3% are reported. Injection efficiency for the upper laser level of 75% was measured for the design by testing devices with variable cavity lengths. A threshold current density of 1.7 kA/cm2 and a slope efficiency of 4.9 W/A were measured for uncoated 3.15 mm × 9 μm lasers. Threshold current density and slope efficiency dependence on temperature in the range from 288 K to 348 K for the structure can be described by characteristic temperatures T0 ∼ 140 K and T1 ∼ 710 K, respectively.
Bessel beams with tunable spot size are desirable for many applications such as laser material processing, optical trapping, and imaging. In this paper, we report experimental and simulation results of using a segmented deformable mirror to generate zero- and higher-order Bessel beams that have a controllable transverse and longitudinal shape. The tilt angle and piston position of the mirror segments are optimized to recreate the phase structure of a reflective axicon. Zero-order Bessel beams are generated at various beam converging angles, and their core diameter, peak intensity, and depth-of-focus are found to agree with the calculated results. By applying a phase ramp along the azimuthal direction, the first-order Bessel beam is generated with the characteristic annular shape. Because deformable mirrors have low absorption and dispersion and operate at a fast frame rate, they are a promising candidate for spatial beam shaping of high-power ultrafast lasers, which are used in material processing applications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.