High power laser transmission is being intensively researched as a potential solution to transfer power to remote systems, being the power converter (PC) one of the main limiting factor to improve the system efficiency ( $\eta $ ). Current PCs are mostly horizontal structures in which the $\eta $ heavily decreases at large input power. In this work, we propose a novel GaAs-based vertical-tunnel-junction (VTJ) PC suitable for ultra-high (UH) input power density (P in ). This structure does not suffer from $\eta $ degradation at high P in because it is designed to have low current density, high output voltage and reduced series resistance (~ 2 orders of magnitude lower than the state-of-the-art PCs). We have demonstrated increasing $\eta $ with P in , reaching values higher than 76% at 3000 $\text{W}\cdot $ cm −2 . This vertical-based architecture enables a new set of potential applications for wireless PC to power remote systems with $\eta $ exceeding today’ s state-of-the-art PC designs.