Structures for a laser-detection device including a magnetic-tunneling-junction layer stack and related methods. The structure has a magnetic-tunneling-junction layer stack including a fixed layer, a free layer, and an insulating spacer between the fixed layer and the free layer, and a power supply coupled to the magnetic-tunneling-junction layer stack. The power supply is configured to bias the magnetic-tunneling-junction layer stack to modulate an energy barrier of the magnetic-tunneling-junction layer stack for switching between a low-resistance state and a high-resistance state in response to receiving incident electromagnetic radiation of an intensity.