Transportable clock laser system with an instability of 1.6 × 10⁻¹⁶

Abstract

We present a transportable ultra-stable clock laser system based on a Fabry–Perot cavity with crystalline Al 0.92 Ga 0.08 As/GaAs mirror coatings, fused silica (FS) mirror substrates, and a 20 cm-long ultra-low expansion (ULE) glass spacer with a predicted thermal noise floor of mod σ y = 7 × 10 −17 in modified Allan deviation at one second averaging time. The cavity has a cylindrical shape and is mounted at 10 points. Its measured sensitivity of the fractional frequency to acceleration for the three Cartesian directions are 2(1) × 10 −12 /(ms −2 ), 3(3) × 10 −12 /(ms −2 ), and 3(1) × 10 −12 /(ms −2 ), which belong to the lowest acceleration sensitivities published for transportable systems. The laser system’s instability reaches down to mod σ y = 1.6 × 10 −16

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