Sensing Earth rotation with a helium-neon laser operating on three transitions in the visible region.

We demonstrate an active Sagnac ring interferometer that operates on the previously unexploited 3s2→2p6 (611.8 nm), 3s2→2p7 (604.6 nm), and 3s2→2p8 (593.9 nm) neon transitions, in a helium-neon gain medium. The cavity was constructed using state-of-the-art ion-beam sputtered, ultralow-loss supermirrors designed to yield greater transmission loss at lower optical frequency, which partially compensates for the gain differential across the three transitions. For an optimized cavity fill of 0.3 mbar partial pressure of neon (50% Ne20 and 50% Ne22) and a total gas pressure of 2 mbar, for laser operation at 611.8 nm, the cavity Q is 1.2×1011, having a cold cavity ringdown time of 38 µs. The laser yielded a stable Sagnac frequency of 117.4 Hz due to the Earth's rotation. The usable gyroscopic sensitivity is determined to be 8.8×10-9 rad/s for a measurement time of 128 s.

Gyroscopic operation on the 3s2→2p10 543.3 nm transition of neon in a 2.56 m2 ring cavity.

We report the development and initial operation of a 6.4 meter perimeter laser gyroscope employing the 543.3 nm, 3s2→2p10 transition of neon. Employing fused silica based supermirrors yielding a cavity Q of 3.9×1011 and an inferred lock in threshold below 1 µHz, the gyroscope unlocked on the bias provided by Earth rotation alone with a measured Sagnac frequency of approximately 133 Hz, which is 16% larger than that of the 632.8 nm transition.

The Macek and Davis experiment revisited: a large ring laser interferometer operating on the 2s2 → 2p4 transition of neon.

We operate a large helium-neon-based ring laser interferometer with single-crystal GaAs/AlGaAs optical coatings on the 2s2→2p4 transition of neon at a wavelength of 1.152276 µm. For either single longitudinal- or phase-locked multi-mode operation, the preferable gas composition for gyroscopic operation is 0.2 and 0.3 mbar of 50:50 neon with total pressures between 6-12 mbar. The Earth rotation bias is sufficient to unlock the device, yielding a Sagnac frequency of approximately 60 Hz.

Sensing earth's rotation with a helium-neon ring laser operating at 1.15 µm.

We report on the operation of a 2.56 m2 helium-neon based ring laser interferometer at a wavelength of 1.152276 µm using crystalline coated intracavity supermirrors. This work represents the first implementation of crystalline coatings in an active laser system and expands the core application area of these low-thermal-noise cavity end mirrors to inertial sensing systems. Stable gyroscopic behavior can only be obtained with the addition of helium to the gain medium as this quenches the 1.152502 µm (2s4→2p7) transition of the neon doublet which otherwise gives rise to mode competition. For the first time at this wavelength, the ring laser is observed to readily unlock on the bias provided by the earth's rotation alone, yielding a Sagnac frequency of approximately 59 Hz.