Physics

Instability

Laser

Mechanics

Thermal stability

Noise (video)

Image (mathematics)

Optics

Artificial intelligence

Power (physics)

Materials science

Thermal

Computer science

Silicon

Quantum mechanics

Optoelectronics

Thermodynamics

Optica

Crystalline optical cavities are the foundation of today's stateof-the-art ultrastable lasers.Building on our previous silicon cavity effort, we now achieve the fundamental thermal-noiselimited stability for a 6 cm long silicon cavity cooled to 4 K, reaching 6.5 × 10 -17 from 0.8 s to 80 s.We also report for the first time, to the best of our knowledge, a clear linear dependence of the cavity frequency drift on incident optical power.The lowest fractional frequency drift of -3 × 10 -19 ∕s is attained at a transmitted power of 40 nW, with an extrapolated drift approaching zero in the absence of optical power.These demonstrations provide a promising direction to reach a new performance domain for stable lasers, with stability better than 1 × 10 -17 and fractional linear drift below 1 × 10 -19 ∕s.

Crystalline optical cavity at 4 K with thermal-noise-limited instability and ultralow drift