High-efficiency multijunction laser power converters are demonstrated for low temperature applications with an optical input at 808 nm. The photovoltaic power converting III-V semiconductor devices are designed with GaAs absorbing layers, here with 5 thin subcells (PT5), connected by transparent tunnel junctions. Unprecedented conversion efficiencies of up to 74.7% are measured at temperatures around 150 K. At temperatures around 77 K, a remarkably low bandgap offset value of W_oc = 71 mV is obtained at an optical input intensity of ~7 W/cm². At 77 K, the PT5 retains an efficiency of 65% with up to 0.3 W of converted output power.

The high-efficiency capabilities of multijunction laser power converters are demonstrated for high-power applications with an optical input of around 1470 nm. The InP-based photovoltaic power converting III-V semiconductor devices are designed here, with 10 lattice-matched subcells (PT10-InGaAs/InP), using thin InGaAs absorbing layers connected by transparent tunnel junctions. The results confirm that such long-wavelength power converter devices are capable of producing electrical output voltages greater than 4–5 V. The characteristics are compatible with common electronics requirements, and the optical input is well suited for propagation over long distances through fiber-based optical links. Conversion efficiencies of ~49% are measured at electrical outputs exceeding 7 W for an input wavelength of 1466 nm at 21 °C. The Power Converter Performance Chart has been updated with these PT10-InGaAs/InP results.

Stable and reliable optical power converting devices are obtained using vertical multi-junction laser power converters. They are based on the GaAs and the InP material systems and are used for power-over-fiber or power-beaming applications. This study demonstrates that, in addition to providing the overall best conversion efficiencies with output voltages ideal for various applications, these semiconductor photovoltaic devices are very tolerant to beam non-uniformity, partial illumination, or beam displacement variations. Examples are given with two tight beams, each covering as little as ~7% of the cell area. An optical input power of 10 W was converted with still an efficiency of Eff ~59.4%. For an input power of 20 W, the illuminated area was set to ~22% without significantly affecting the conversion efficiency of Eff ~60%. Remarkably, for a beam diameter at ~65% of the chip length (i.e., covering ~35% of the chip area), a converted power of 29.5 W was obtained using a 12-junction GaAs device with a conversion efficiency of 61%. For a 10 junction InP-based device, an efficiency of Eff = 51.1% was obtained at an output voltage reaching as high as V_oc = 5.954 V for an average optical intensity of 69 W/cm² and an illumination area of ~57%.

Photonic power converters (PPCs) are a class of photovoltaic devices designed for efficient conversion of monochromatic (laser or LED) light to electricity. These devices are composed of multiple p-n junction diodes arranged in a tandem configuration and connected in series. They have reached high energy conversion efficiencies (70%) and areal power densities of 100 W/cm$^{2}$. When these devices are illuminated with a high-efficiency diode laser they can provide isolated DC-DC conversion from the laser voltage (< 2.3 V) to the open-circuit voltage of the PPC (1.2 to 23 V) with low capacitance and low conducted electromagnetic interference compared to conventional switching power converters. The voltage conversion ratio is controlled by varying the number of p-n junctions in the PPC from 1 to 20 in demonstrated designs. In this article we demonstrate the use of photonic power conversion within two new applications. Firstly, the laser/PPC unit is applied as a linear photonic boost converter, producing a regulated 12V output stepped-up from a 3.3V input to the control board. Output ripple is negligible as compared with a switching boost converter of similar size. Efficiency of this linear, regulated DC/DC conversion system was 12.7%, compared with a 77.6% reference switch-mode converter. Power density was 0.18 W/cm$^{3}$, compared with 1.5 W/cm$^{3}$ for the reference. Relative to switch-mode power conversion, the photonic technology has lower efficiency and lower power density, but superior isolation and rejection of ripple and EMI. Both technologies are highly scalable. For the second application, the same unit is applied to power a 650V SiC MOSFET gate driver requiring high galvanic isolation, demonstrating a 20 dB reduction in conducted-current electromagnetic interference from the power circuit into the lowvoltage control systems.

High-performance optical power converters (OPCs) enable isolated electrical power and power beaming applications at new wavelengths and higher output powers. Broadcom’s vertical epitaxial heterostructure architecture (VEHSA) multi-junction OPCs permit optical-to-electrical conversion at high efficiency and at manageable external loads. This study provides details of how the power outputs have been extended from 20 W. The work also provides details of how the spectral range options have been extended from 800–830 nm to other key laser diode wavelengths such as 960–990 nm and 1500–1600 nm.

Mobile communication services are crucial during emergency disasters and temporary events, and future mobile communication systems should be able to provide such services. Airborne base stations using drones are highly effective as stand-in base stations in areas where the ground base stations are inoperable or at temporary event sites. However, it is difficult for conventional drones to provide mobile communication services without interruption due to flight time limitations caused by their limited battery capacity. Thus, a drone drive with a non-interrupted power supply is urgently needed. In this study, we developed an airborne base station that enables drones to be driven and maneuvered by optical fibers. We simultaneously transmitted radio frequency (RF) data signals for the airborne base station and control signals for the drone and evaluated the transmission performances of the RF signals and the controllability of the drone. Furthermore, we conducted a flight experiment on a medium-sized drone powered by optical fibers.