Continuous-wave operation of InGaN green laser diodes (LDs) on semipolar f2021g GaN substrates with output powers of over 100 mW in the spectral region beyond 530 nm is demonstrated. Wall plug efficiencies (WPEs) as high as 7.0-8.9% are realized in the wavelength range of 525-532 nm, which exceed those reported for c-plane LDs. The longest lasing wavelength has reached 536.6 nm under cw operation. These results suggest that the InGaN green LDs on the f20 21g plane are better suited as light sources for applications requiring wavelengths over 525 nm.

True green GaInN laser diodes with a lasing wavelength above 525 nm under continuous wave operation have been successfully fabricated on semipolar {2021} GaN substrates by improving both the diode structure and epitaxial growth conditions. At a case temperature of 55 °C, their lifetime was estimated to be over 5000 h for an optical output power of 50 mW and over 2000 h at 70 mW.

A linear generator system is expected to realize a highly efficient free-piston generation engine. The efficiency of the system mainly depends on the generation and thermal efficiencies of the engine. The generation efficiency decreases owing to a large braking force on the expansion stroke and a speed reduction at the ends of the stroke. This paper proposes generation control with resonance and output drop that improves the generation efficiency during the expansion stroke. When changing the amount of consumed fuel, the condition to maximize the electricity generation can be achieved by optimizing the ratio of the iron to copper losses. Furthermore, the proposed method improves the combustion performance of the engine by ensuring ideal speed at the combustion start position.

A free-piston engine linear generator (FPEG) system is a linear generator, which generates electricity when a free piston reciprocates the combustion thrust produced by internal combustion. It is expected that this system can be applied to hybrid vehicles. In an FPEG system, the high combustion energy is instantly added to a free piston. Nevertheless, it is difficult for a linear synchronous generator (LSG) to convert combustion energy into electric energy by using the output of the LSG given the limit of the inverter capacity. Hence, it is necessary for an LSG to convert combustion energy into electric energy while distributing the combustion energy in one stroke. Moreover, if an LSG is driven at high velocity and high thrust within the limit of an inverter capacity, then the LSG converts the high combustion energy into electric energy. In this study, we propose a configuration of an LSG with a typical output of 10 kW and a generation efficiency of 97% for an FPEG, and we evaluate its static thrust and magnetic flux density distribution using finite element method (FEM) analysis. Moreover, we examine the driving range of the LSG for an FPEG system.

No abstract