Accelerating laser processes with a smart two-dimensional polygon mirror scanner for ultra-fast beam deflection

In laser processing, the possible throughput is directly scaling with the available average laser power. To avoid unwanted thermal damage due to high pulse energy or heat accumulation during MHz-repetition rates, energy distribution over the workpiece is required. Polygon mirror scanners enable high deflection speeds and thus, a proper energy distribution within a short processing time. The requirements of laser micro processing with up to 10 kW average laser powers and high scan speeds up to 1000 m/s result in a 30 mm aperture two-dimensional polygon mirror scanner with a patented low-distortion mirror configuration. In combination with a field programmable gate array-based real-time logic, position-true high-accuracy laser switching is enabled for 2D, 2.5D, or 3D laser processing capable to drill holes in multi-pass ablation or engraving. A special developed real-time shifter module within the high-speed logic allows, in combination with external axis, the material processing on the fly and hence, processing of workpieces much larger than the scan field.

National primary standard for the unit of average laser radiation power GET 28-2016

The description of the National primary standard for the unit of average laser radiation power GET 28-2016 with a power range from 10–9 to 5·10–3 W is described. The principle of operation of a standard based on a photoelectric trap detector in the range from 10–9 to 5·10–3 W is described. As a result of metrological studies at National primary standard, it was determined that the value of the total standard uncertainty of reproduction and transmission of an average power unit for the range from 10–9 to 5·10–3 W is no more than 0.36 %. The model and theoretical characteristics of the measuring beam splitter, allowing to expand the range of the National primary standard to the range of kilowatt power levels, are presented. National primary standard allows solving the problems of metrological support of promising low-level laser ranging systems both in the ground and in the aerospace field, ensuring the uniformity of measurements of radiometric parameters of low-intensity laser radiation fluxes.

Излучательная эффективность терагерцовых антенн с традиционной топологией и металлической метаповерхностью: сравнительный анализ

We report on experimental study of the photoconductive antennas (PCA)-emitters featuring conventional topology as well as metallic metasurface with plasmonic grating, based on the InGaAs/InAlAs superlattices. We measure and determine the photocurrents and the emission spectra of the PCAs, as well as the energy characteristics of the terahertz (THz) radiation, and the efficiency of the optical-to-THz conversion for different bias voltages and average laser excitation power. The integral THz emission power of 10 μW as well as conversion efficiency of 0.2% are demonstrated for the PCA with the metasurface, which are not reachable for the conventional due to thermal breakdown of the antenna. Therefore, the PCAs with the metasurface can be considered to be the attractive THz emitters that can potentially become among the elemental base for modern THz spectroscopic systems for biomedical applications.

Sensitivity studies for a space-based methane lidar mission

Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1% over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised.

Sensitivity studies for a space-based methane lidar mission

Methane is the third most important greenhouse gas in the atmosphere after water vapour and carbon dioxide. A major handicap to quantify the emissions at the Earth's surface in order to better understand biosphere-atmosphere exchange processes and potential climate feedbacks is the lack of accurate and global observations of methane. Space-based integrated path differential absorption (IPDA) lidar has potential to fill this gap, and a Methane Remote Lidar Mission (MERLIN) on a small satellite in Polar orbit was proposed by DLR and CNES in the frame of a German-French climate monitoring initiative. System simulations are used to identify key performance parameters and to find an advantageous instrument configuration, given the environmental, technological, and budget constraints. The sensitivity studies use representative averages of the atmospheric and surface state to estimate the measurement precision, i.e. the random uncertainty due to instrument noise. Key performance parameters for MERLIN are average laser power, telescope size, orbit height, surface reflectance, and detector noise. A modest-size lidar instrument with 0.45 W average laser power and 0.55 m telescope diameter on a 506 km orbit could provide 50-km averaged methane column measurement along the sub-satellite track with a precision of about 1 % over vegetation. The use of a methane absorption trough at 1.65 μm improves the near-surface measurement sensitivity and vastly relaxes the wavelength stability requirement that was identified as one of the major technological risks in the pre-phase A studies for A-SCOPE, a space-based IPDA lidar for carbon dioxide at the European Space Agency. Minimal humidity and temperature sensitivity at this wavelength position will enable accurate measurements in tropical wetlands, key regions with largely uncertain methane emissions. In contrast to actual passive remote sensors, measurements in Polar Regions will be possible and biases due to aerosol layers and thin ice clouds will be minimised.