Electro-optically tunable single-frequency VCSELs for atomic clocks

We report on the design and performance of single-frequency VCSELs that are electro-optically tunable in the 852nm wavelength range. Electro-optic tuning of the index of refraction is achieved by changing the reverse-bias electric field in a secondary p-i-n junction that contains coupled quantum wells. The electro-optic tuning is enhanced by putting the index-tuning region in a secondary cavity of a dual-cavity VCSEL. Electro-optic tuning can achieve 1nm of wavelength tuning without changing laser power and can operate at modulation frequencies up to 1GHz.