Continuous-frequency measurements of high-intensity microwave electric fields with atomic vapor cells

We demonstrate continuous-frequency electric field measurements of high-intensity microwaves via optical spectroscopy in a small atomic vapor cell. The spectroscopic response of a room-temperature rubidium atomic vapor in a glass cell is investigated and employed for absolute measurements of Ka-band microwave electric fields from ∼200 V/m to >1 kV/m over a continuous frequency range of ±1 GHz (15% band coverage). It is established that in strong microwave fields, frequency-specific spectral features allow for electric field measurements over a large continuous frequency range.