The Low Temperature Joining Technique (LTJT) using silver compounds enables to significantly increase the thermal conductivity between joined elements, which is much higher than for soldered joints. However, it also makes difficult to measure the thermal conductivity of the joint. The Laser Flash Analysis (LFA) is a non-intrusive method of measuring the temperature rise of one surface of a specimen after excitation with a laser pulse of its other surface. The main limitation of the LFA method is its standard computer software, which assumes the dimensions of a bonded component to be similar to those of the substrate, because it uses the standard Parker’s formula dedicated for one-dimensional heat flow. In the paper a special design of measured specimen was proposed, consisting of two copper plates of different size joined with the sintered silver layer. It was shown that heat properties of these specimens can also be measured after modifying the LFA method. The authors adapted these specimens by masking the false heat signal sourced from the uncovered plate area. Another adaptation was introducing a correcting factor of the heat travel distance, which was calculated with heat-flow simulations and placed into the Parker’s formula. The heat-flow simulated data were compared with the real LFA measurement results, which enabled estimation of the joint properties, e.g. its porosity.

Fractional slot PMSM motors enable high power density factors to be obtained provided that their electromagnetic circuit, appropriate mechanical structure and cooling system are properly designed, as well as when operating at a high frequency of power supply voltage (400–800 Hz) with high magnetic saturation and high current loads (approx. 12–15 A/mm2). Such operating conditions, especially in the case of fractional slot motors, may be the reason for excessive rotor losses, mainly in the rotor yoke and permanent magnets. One of the conditions for obtaining high values of continuous power of the motor is the reduction of these losses. This paper presents selected design methods for limiting the value of rotor losses with simultaneous consideration of their influence on other motor parameters. The analysiswas carried out for aPMSMmotor with an external rotorweighting approx. 10 kg and a maximum power of 50 kW at a rotational speed of 4 800 rpm.

In order to meet the application requirements of high-power mobile inductively-coupled power transfer (ICPT) equipment, the structure of the dual transmitter and pickup can be used to improve the transmission power of the ICPT system. However, this structure cannot easily describe the change of the mutual inductance parameter in the moving state, making the mathematical model difficult to establish. The change of load parameters during the movement will affect the current and voltage at the transmitter and pickup coils. Aiming at these problems, this paper proposes a dual transmitter and pickup ICPT system based on inductor-capacitor-inductor (LCL) compensation network, and analyzes its power trans- mission efficiency. By setting the shape and size of the coil, the influence of the change of the mutual inductance parameters on the system efficiency during the movement is reduced. The changes of the mutual inductance parameters of the ICPT system under the moving state are simulated by changing the coupling coefficient in the PSpice software. The results show that the structure of the ICPT system used in this paper can improve the output power and reduce the influence of the system when the load changes.

In this paper, we describe the development and design procedure of the new kind of coaxial TE_m,1 modes generator based on ring resonator with coupling apertures. The generator enables excitation of subsequent TE_m,1 modes in a cylindrical waveguide. The proposed design method allows to obtain high purity TE_m,1 modes. The angular mode number can be chosen by replacing the plate with coupling apertures. Structure and parameters of the generator was optimized using CST-Microwave Studio. The mode generator was fabricated and checked on the test bench in an anechoic chamber. The measured field distributions confirm excitation of the desired TE_m,1 modes. A good agreement between simulations and measurements is obtained. The presented mode generator, operating in non-rotating TE_m,1 modes, is easy to fabricate, and suitable for cold-test experiments of high power components and devices.

The double barrier separate confinement heterostructure (DBSCH) design aimed at reduction of vertical beam divergence and increase of catastrophic optical damage (COD) level for high power laser diodes (LDs) operation is presented. Insertion of thin, wide-gap barrier layers at the interfaces between waveguide and cladding layers of SCH gives an additional degree of freedom in design making possible more precise shaping of the optical field distribution in the laser cavity. By comparison with the large optical cavity (LOC) heterostructure design it has been shown that the low beam divergence emission of DBSCH LDs can be attributed to the soft-profiled field distribution inside the cavity. This ‘soft mode profile’ seems to determine narrow laser beam emission rather than the field distribution width itself.

The potential problem with the soft-profiled but relatively narrow (at half-maximum) mode distribution is a lower COD level. Widening of the mode profile by the heterostructure design corrections can increase it, but care must be taken to avoid excessive decrease of confinement factor (Γ). As a result it is shown that DBSCH design is possible, where the low beam divergence and high COD level is achieved simultaneously.

Wide stripe gain-guided LDs based on GaAsP/AlGaAs DBSCH SQW structures have been manufactured according to the design above. Gaussian-shaped narrow directional characteristics are in relatively good agreement with modelling predictions. Vertical beam divergences are 13–15◦ and 17–18◦ FWHM for design versions experimentally investigated. Threshold current densities of the order of 350–270 Acm-2 and slope efficiencies of 0.95 and 1.15 W/A have been recorded for these two versions, respectively. Optical power at the level of 1 W has been achieved. The version with lower beam divergence proves to be more durable. Higher optical power levels are to be obtained after heterostructure doping optimisation.

1) Background: the modeling, characterization, transformation and propagation of high-power CW laser beams in optical (including fiberoptic) trains and in the atmosphere have become hot topics in laser science and engineering in the past few years. Single-mode output is mandatory for high-power CW laser applications in the military field. Moreover, an unstationary, dynamic operation regime is typical. Recognized devices and procedures for laser-beam diagnostics could not be directly applied because of dynamic behavior and untypical non-Gaussian profiles. 2) Methods: the Wigner transform approach was proposed to characterize dynamically variable high-power CW laser beams with significant deterministic aberrations. Wavefront-sensing measurements by means of the Shack-Hartmann method and decomposition into an orthogonal Zernike basis were applied. 3) Results: deterministic aberration as a result of unstationary thermal-optic effects depending on the averaged power of the laser output was found. Beam quality determined via the Wigner approach was changed in the same way as the measurements of the beam diameter in the far field. 4) Conclusions: such an aberration component seems to be the main factor causing degradation in beam quality and in brightness of high-power CW laser beams.

High power fibre lasers need to be cooled efficiently to avoid their thermal damage. Temperature distribution in fibre should be estimated during the fibre laser design process. The steady-state heat equation in a cylindrical geometry is solved to derive a practical formula for temperature radial distribution in multi-layered optical fibres with arbitrary number of the layers. The heat source is located in one or more cylindrical domains. The validity of the analytical formula is tested by comparison with static heat transfer simulations of typical application examples including octagonal double clad fibre, air-clad fibre, fibre with nonuniform, microstructured core. The accuracy sufficient for practical use is reported even for cases with not exactly cylindrical domains.