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

Abstract

Crystalline optical cavities are the foundation of today's state-of-the-art ultrastable lasers. Building on our previous silicon cavity effort, we now achieve the fundamental thermal noise-limited stability for a 6 cm long silicon cavity cooled to 4 Kelvin, reaching 6.5 × 10 −17 from 0.8 to 80 seconds. We also report for the first time a clear linear dependence of the cavity frequency drift on the 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 ×

A simplified cryogenic optical resonator apparatus providing ultra-low frequency drift

“…The long-term frequency drift rate was found to depend on the power of the interrogating laser wave and on the duty cycle of the interrogation. Our results, together with previous studies 7, 24,27 , indicate that in the limit of very low interrogation laser power and very low duty cycle the drift rate becomes extremely small.…”

“…This value is a factor three higher then the drift measured on a resonator with comparable dimensions by Ref. 24 and a factor seventy higher compared to our previous result obtained with a 25 cm long silicon resonator 7 . However, this latter drift was measured after almost a yearlong continuous operation at 1.5 K. The drift after the first 100 days was almost identical to the current result, 1 × 10 −18 /s.…”

“…It follows the concept presented in refs. [22][23][24]26,27 , but was further simplified by avoiding the conical spacer shape and employing instead a simple cylindrical shape. The spacer diameter and length were chosen to be 37 mm and L = 50 mm, respectively, the mirror substrates are of standard one-inch diameter and 6.3 mm thick.…”

“…14). One approach for reducing both limitations is the operation of the resonators at cryogenic temperatures 6,7,[22][23][24][25][26][27][28][29] .…”

Lasing on a narrow transition in a cold thermal strontium ensemble

“…The high Q-value of the atomic transitions (Q > 10 17 ) exceeds that of the corresponding reference laser stability for the duration of the interrogation cycle [4][5][6][7][8]. State-of-the-art reference lasers now perform below the level of 10 −16 fractional frequency stability at 1 s [9][10][11]. This recent advance in performance is enabled by using crystalline mirror coatings and spacers as well as employing cryogenic techniques.…”