A resonantly pumped monolithic Ho:YAG nonplanar ring oscillator (NPRO) with single-frequency and dual-wavelength laser outputs is demonstrated. The Ho:YAG NPRO is resonantly pumped by a 1907-nm Tm:YLF laser. In single-frequency operation, the output power is 3.09 W, with a slope efficiency of 61% and an optical efficiency of 48% with respect to the pump power. Up to 10 W dual-wavelength laser output at 2091 and 2097 nm is also obtained from the Ho:YAG NPRO with the maximum pump power, with a slope efficiency of 61% with respect to the pump power.
In self-powered wireless sensor nodes, the efficiency for environmental energy harvesting, storage and
management determines the lifetime and environmental adaptability of the sensor nodes. However, the method of
improving output efficiency for traditional photovoltaic power generation is not suitable for a solar micro-power
system due to the special requirements for its application. This paper presents a solar micro-power system
designed for a solar self-powered wireless sensor node. The Maximum Power Point Tracking (MPPT) of solar
cells and energy storage are realized by the hybrid energy storage structure and "window" control. Meanwhile, the
mathematical model of energy harvesting, storing and management is formulated. In the novel system, the output
conversion efficiency of solar cells is 12%.