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The use of semiconductor lasers is beneficial in long-distance communications. Practical communication systems based on these lasers need high ambient temperature, with temperature changes between $40^{\circ }$C and $85^{\circ }$C. The study of the temperature-dependent response of these lasers is important to improve them. This study investigates the effect of temperature on InGaN-based vertical cavity surface emitting lasers (VCSEL). The active region in this structure includes a single quantum well (SQW). The rate equations of carriers and densities are numerically solved. The time variations of carrier density, photon density and output power ($N$, $S$ and $P$) at $25^{\circ }$C and the current injection of 0.04 A are obtained. Values obtained for threshold current and output power include 7 mA and 44 mW, respectively. The effect of temperature on the time variations of $N$, $S$ and $P$ from $10^{\circ }$C to $35^{\circ }$C is studied. Results show that these parameters decrease and the threshold current increases with an increase in temperature. Furthermore, the investigation of the effect of injection current on $N$, $S$ and $P$ shows that raising the injection current can increase these parameters. Moreover, an increase in the injection current reduces the time response.

The popularization of smart mobile devices has led to the research on wireless power transfer (WPT) technology. Previous research shows that increasing the excitation coil or the energy transfer coil can increase the energy transmission distance of the WPT system. But the mutual inductance calculation of coils is not accurate enough when the distance is close. This paper presents an improved formula to calculate the mutual inductance between two round inductance coils. Contrasts with the previous calculation methods, computer simulation and experimental results are done to validate the accuracy of the formula, especially when the two inductance coils are close together. On the basis of this formula, the maximum output power (MOP) and the maximum output power distance (MOPD) of the two-, three- and four-coil series–series resonance WPT systems based on circuit models are studied and compared. The simulation and experimental results show a high consistency with the theoretical calculation results. We can find that the farther the MOPD of the system is, the smaller the MOP is. Moreover, when the operating frequency increases, the MOPD of the two-coil conformation increases, while the four-coil conformation is just opposite.

This paper reviews the current status of maximizing output power in spin transfer nano-oscillators (STNOs). The key factors affecting output power and the methods to maximize output power in STNOs are briefly introduced. The recent development trends for STNOs are also reviewed in this paper. This article is one of a series devoted to the subject of Latest Progress on Spintronics Devices.