Dichroic Two-Photon Rubidium Frequency Standard

Frequency standards find wide use in navigation and timing for industry, civilian, and defense applications. Unfortunately, the very best frequency standards are bulky, power-hungry, and confined to well-controlled laboratory environments. Here the authors aim to deliver a compact, high-performance standard, the key challenge being the need to produce a strong, narrow atomic transition. They produce a superstrong signal by driving a two-photon transition in ⁸⁷Rb vapor that exploits a fortuitous third atomic level to greatly enhance the effective strength of the atom-light interaction, allowing short-term clock performance comparable to today's best commercial frequency standards.