Study of paramagnetic properties of Fe 3+ ions in sapphire for the - - PowerPoint PPT Presentation

Study of paramagnetic properties of Fe3+ ions in sapphire for the realization of a cryogenic whispering gallery maser oscillator

Introduction = WG resonator = WG maser

Experiments

Conclusions

• E. Rubiola on behalf of
• K. Benmessai, P.-Y. Bourgeois, M. Oxborrow*, N. Bazin, Y. Kersalé and V. Giordano

FEMTO-ST Institute, dept LPMO, Université de Franche-Comté, Besançon, France * National Physical Laboratory, Teddington, UK

Outline

download from http://www.lpmo.edu/~pybourgeois/download/cpem-2006.pdf

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Introduction – WG resonator and oscillator QL = 2x105 @ 300 K QL = 3x107 @ 77 K QL = 108 – 109 @ 4 K WGMm,n,l Low dielectric losses: Q0 = 1 / tan δ

Introduction – Whispering gallery mode maser oscillator

Pump WGH17,0,0 Gallery mode @ 31.2 GHz Maser @ 12.04 GHz

Fe+3 Resonator @ 4.2 K

Storage

Energy recycling

ν12 = 12.04 GHz

Sapphire Zero dc magnetic field

Pump @ 31.2 GHz Fast relaxation Population inversion

12.038

ν12 =12.04 Frequency (GHz) Absorption WGH17,0,0 low losses Line shape of Fe3+ BW = 27 MHz

Fe3+=[Ar]3d5 6S5/2

BW » 50 MHz

Experiments – Whispering gallery mode maser oscillator

Pump 31.2 GHz, 2 dBm

Output power –54 dBm (H-maser –90 dBm) Simple system, as compared to the sapphire oscillator All the oscillator is at cryogenic temperature

Maser 12.04 GHz, –54 dBm

Theoretical expectation σy = 1.5x10-16 τ–1/2 (T=4 K, P=10 nW)

T = 8 K

νmaser- νLO

Experiments – Maser stability

Low pass

νmaser

Counter

Local Oscillator Ref Ref Hydrogen Maser

νLO

50 dB LO RF

Results

Temperature control at 8 K No power control, no Pound servo ! Short term limited by H-maser stability σy(30s) = 2.5x10–14 t>100 s: random walk σy (τ) τ (s)

H maser

χ0 dc magnetic susceptibility χ’ ac magnetic susceptibility T2 spin to spin relaxation time N ions concentration g Landé factor (g » 2) β Bohr magneton νESR = 12.38 GHz » ν17,0,0

Two sets of measurements: PUMP off: identification of the WGHm,0,0 mode (9<m<20) νm,0,0 PUMP on: frequency shift measurement νm,0,0 sat

Experiments – Paramagnetic parameters : N,T2 and χ0

after data fitting:

In the literature the ESR width is about 27 MHz => T2 = 10 ns NHEMEX = 2 ppm

REF: Trace element studies in HEM™ sapphire LIGO report M030336-00-M

~

Experiments – Paramagnetic parameters : N,T2 and χ0

For each WG mode: pump off => identify the mode pump on => measure Δν

EXPERIMENTS:

Spin-lattice relaxation time T1

T1 = 10 ms @ 8 K

CSO at WGH18,0,0 frequency = 12.65 GHz QL~ 30x106 over-coupled mode

Vosc

Conclusions

Implementation Simple, as compared to CSO The whole oscillator is inside the cryostat No pump power control, no phase control Temperature control at the 8K turnover Available power –54 dBm (40 dB higher than the H-Maser) Short-term stability σy(30s) = 2.5×10–14 achieved σy(τ) ⋲1.5x10-

16 τ–1/2 expected, at T=4K & P=10nW

Paramagnetic properties spin-lattice relaxation time T1 = 10 ms at 8 K (law: 1/temperature) spin-to-spin relaxation time T2 = 2 ns qualitative agreement with T2 = 10 ns in the literature χ0 = 1×10-9 N = 12 ppb [while N(HEMEX) = 2 ppm] => only a small fraction of the Fe3+ ion mase

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download from http://www.lpmo.edu/~pybourgeois/download/cpem-2006.pdf