Picowatts

Picowatts (symbol pW) are a unit of power in the International System of Units (SI). One picowatt equals 10^-12 watts, representing one trillionth of a watt. The prefix pico- denotes 10^-12, and the watt is the base unit of power in the SI system.

In relation to other common submultiples of the watt, 1 pW equals 0.001 nanowatts (nW) and 10^-3 nW. In decibel terms, 1 pW corresponds to -90 dBm when measured against a reference of 1 milliwatt.

Picowatts are used to describe extremely low-power levels encountered in fields such as electronics, photonics, and precision instrumentation. They are relevant in optical communication at the receiver input, in quantum experiments, and in nanoscale devices where signals or leaked power are minute.

Measuring and working with picowatts pose challenges due to noise, thermal fluctuations, and detector sensitivity. Specialized equipment such as low-noise photodetectors, calibrated attenuators, and carefully shielded measurement setups are often required. Calibration and traceability to SI standards are important for accuracy in research and metrology.

Related units include femtowatts (10^-15 W) and attowatts (10^-18 W), which describe even smaller power levels. Picowatts occupy a practical middle ground for describing faint but detectable signals in modern low-power technologies.