Monolithic optical cavities with low thermal noise and

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06_simpozium_kolachevskiy.ppt

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Monolithic optical cavities with low thermal noise and perspectives for laser frequency stabilization N.Monolithic optical cavities with low thermal noise and perspectives for laser frequency stabilization N. Kolachevsky, K. Khavarova, A. Gribov, N. Zadnov, S. Sluysarev

Request for the short time stability ( Doppler radars, etc. ) carrier target frequency.Request for the short time stability ( Doppler radars, etc. ) carrier target frequency. S p ectral p ow er d en sity. Emitted carrier Doppler responce

Interrogating oscillator  Cs-fountains Optical clock 9 GHz 300 THz Interrogating oscillator Cs-fountains Optical clock 9 GHz 300 THz

Quartz oscillators ( OXCO ) ( e. g. “Morion”, Oscilloquartz ) Temperature drift Time,Quartz oscillators ( OXCO ) ( e. g. “Morion”, Oscilloquartz ) Temperature drift Time, sdeviation

Cryogenic sapphire oscillators Sapphire critical temperature @ 6. 12 К Frequency 9. 9 GHzCryogenic sapphire oscillators Sapphire critical temperature @ 6. 12 К Frequency 9. 9 GHz

Cryogenic sapphire oscillators Superior stability Cryogenic sapphire oscillators Superior stability

University of Western Australia How to lower the instability further? University of Western Australia How to lower the instability further?

Optical domain ! Increasing the carrier freqeuncy Optical domain ! Increasing the carrier freqeuncy

N. Hinkley at al. , Science Vol. 341 no. 6151 pp. 1215 -1218 (2013)OpticalN. Hinkley at al. , Science Vol. 341 no. 6151 pp. 1215 -1218 (2013)Optical clocks ( × 104 carrier freqeuncy ) Ultrastable laser Cold atomic ensemble

The problem is solved: optical clocks with laser-cooled atoms (ions) provide necessary specifications forThe problem is solved: optical clocks with laser-cooled atoms (ions) provide necessary specifications for instability and accuracy. How about technological aspects ? ? ? • Bulky and very sensitive to adjustment: laser cooling, trapping in the lattice, reading the clock transition • From 5 to 10 laser systems are required. Lasers are yet much less robust compared to microwave components.

“ Transportable ”  ytterbium optical clocks ( Duesseldorf ) “ Transportable ” ytterbium optical clocks ( Duesseldorf )

 • One needs a compact setup with minimal number of robust laser systems • One needs a compact setup with minimal number of robust laser systems • One can restrict requirements for the short/long term instabitliy to 10 -1 6 — 10 —

A laser locked to the passive optical cavity Limitations? Vladimir  Braginsky dream: 10A laser locked to the passive optical cavity Limitations? Vladimir Braginsky dream: 10 -20 !

Stabilized lasers at LPI • Compact systems based on ULE glass cavitites • RoomStabilized lasers at LPI • Compact systems based on ULE glass cavitites • Room temperature operation ( critical point T с 300 K ) • Vibration compensation

Clock lasers @ 6 98  nm (VNIIFTRI+LPI) A. Galyshev ,  Ph. DClock lasers @ 6 98 nm (VNIIFTRI+LPI) A. Galyshev , Ph. D A. Gribov , Ph. D.

Typical beatnote FWHM 1. 7 Hz ( RBW = 1 Hz ) Typical beatnote FWHM 1. 7 Hz ( RBW = 1 Hz )

Experiment 0, 01 0, 1 1 10 100001 E-151 E-14  1 s Experiment 0, 01 0, 1 1 10 100001 E-151 E-14 1 s Gat e t im e, 5. 5 Hours of meas urem ent 10 m s Gat e t im e, 350 s of m eas urem ent gate time, s. A lla n d e v ia tio n. Thermal noise limit Without drift compensation

Instability sources:  1) Thermal noise   ( fundamental )  2) AgingInstability sources: 1) Thermal noise ( fundamental ) 2) Aging of composite materials ( + technical noise )

Nature of thermal noisel l Random Brownian motion of mirror surfaces due to thermalNature of thermal noisel l Random Brownian motion of mirror surfaces due to thermal excitation of vibrational modes l

Thermal noise of ULE cavity  Multilayer dielectric structure 0 ( ) 2 1Thermal noise of ULE cavity Multilayer dielectric structure 0 ( ) 2 1 1 coating mirror coat sub S S d w 17 ( ) 5. 4 10 coat. S f f m Hz Spectral density 6 10 10 мd 25 coat spacer Material losses Thickness of the coating

Contribution to thermal noise  Allan deviation Spacer Substrate Coating Net: ( ) ,Contribution to thermal noise Allan deviation Spacer Substrate Coating Net: ( ) , S f m Hz ( ) , S f Hz Hz 18 1. 7 10 17 4. 9 10 17 5. 4 10 17 7. 2 10 0. 4 0. 30 0. 27 0. 01 y 15 1.

How to improve stability? • Lowering the temperature • Crystalline materials  How to improve stability? • Lowering the temperature • Crystalline materials

Fritz Riehle,  PTB The first silicon cavity Fritz Riehle, PTB The first silicon cavity

Silicon  - Optical material for - Critical temperature 124 К - Low mechanicalSilicon — Optical material for — Critical temperature 124 К — Low mechanical losses — High thermal conductivity ( ULE× 100)7 10 1200 nm

Cryogenic silicon cavities JILA & PTB C. Hagemann et al. , Opt. Lett. 39,Cryogenic silicon cavities JILA & PTB C. Hagemann et al. , Opt. Lett. 39, 5102 (2014)

Crystalline mirrors (Al. Ga. As)  • Infrared region •  99. 99R •Crystalline mirrors (Al. Ga. As) • Infrared region • 99. 99%R • Low mechanical losses • High reflectivity

Crystalline cavities project at LPI & VNIIFTRI Cryogenic Si cavities, Ga. As cavities Crystalline cavities project at LPI & VNIIFTRI Cryogenic Si cavities, Ga. As cavities

Prototype for compact system with 10 -15 instability/day Prototype for compact system with <10 -15 instability/day

Laser source  Fiber laser @ 1. 5 m  LASUS system Laser source Fiber laser @ 1. 5 m LASUS system

Space-specified frequency comb  FOKUS (Menlo Systems) Space-specified frequency comb FOKUS (Menlo Systems)

Conclusion/outlook  • Microwave systems with 10 -15 instability in 1 second are alreadyConclusion/outlook • Microwave systems with <10 -15 instability in 1 second are already commercially available (Menlo Systems) • Space-specified systems may appear on 5 -year horizon • Optical-to-microwave systems with 10 -16 — 10 -15 instability will be available based on crystalline/cryogenic technologies • Strong competition to H-masers on 10 -year horizon