Coherent Spectroscopy of RareEarth-Ion Doped Whispering Gallery Mode Resonators D. L. McAuslan, D. Korystov, and J. J. Longdell Jack Dodd Centre for Photonics and Ultra-Cold Atoms, University of Otago, Dunedin, New Zealand. David McAuslan – QIP-REIDS2011 Outline Whispering Gallery Modes (WGMs). Strong Coupling Regime of Cavity QED. Experiments. ◦ ◦ ◦ ◦ ◦ Atom-Cavity Coupling. Coherence Time. Population Lifetime. Spectral Hole Lifetime. Optical Bistability/Normal-Mode Splitting. David McAuslan – QIP-REIDS2011 Whispering Gallery Modes Electric field confined to equator. High quality factor. [1] Small mode volume. Ideal for strong coupling cavity QED. [1] S. Arnold et al., Opt. Lett. 28 (2003). David McAuslan – QIP-REIDS2011 Whispering Gallery Modes [1] [2] [2] [3] [3] [4] Microdisk Microtoroid Microsphere Crystalline r~10-100 μm. Q=107. r~20-100 μm. Q=108. r~10-500μm. Q=109. r~100-5000μm. Q=1011. [1] T. J. Kippenberg, PhD. Thesis (2004). [2] A. Schliesser et al., Nature Physics 4 (2008). [3] Y. Park et al., Nano Lett. 6 (2006). [4] J. Hofer et al., PRA 82 (2010). David McAuslan – QIP-REIDS2011 Strong Coupling Regime κ – cavity decay rate: γ – atomic population decay rate: γh – atomic phase decay rate: g – coupling between atoms and cavity: David McAuslan – QIP-REIDS2011 Strong Coupling Regime Critical atom number: Saturation photon number: N0<1, n0<1. “Good cavity” strong coupling regime: g > κ, γ, γh. “Bad cavity” strong coupling regime: κ > g >> γ, γh. David McAuslan – QIP-REIDS2011 Why Strong Coupling? Reversible State Transfer Single Atom Detection D. L. McAuslan et al., Physical Review A 80, 062307 (2009) David McAuslan – QIP-REIDS2011 Aim of Experiments Measure the properties of a Pr3+:Y2SiO5 resonator. ◦ ◦ ◦ ◦ Atom-cavity coupling. Coherence time. Population lifetime. Spectral hole lifetime. Calculate cavity QED parameters to determine viability of strong-coupling regime. David McAuslan – QIP-REIDS2011 Experimental Setup Resonator: ◦ 0.05% Pr3+:Y2SiO5. ◦ r = 1.95mm. ◦ Q = 2 x 106. LO Probe Sample: ◦ 0.02% Pr3+:Y2SiO5. ◦ 5x5x5mm cube. David McAuslan – QIP-REIDS2011 D. L. McAuslan et al., ArXiv:1104.4150 (2011) D. L. McAuslan et al., ArXiv:1104.4150 (2011) π Pulse Length π = 0.32μs for Pin = 700μW David McAuslan – QIP-REIDS2011 D. L. McAuslan et al., ArXiv:1104.4150 (2011) D. L. McAuslan et al., ArXiv:1104.4150 (2011) Atom-Cavity Coupling Rabi frequency: Atom-Cavity Coupling: Compare to g calculated from the theoretical mode volume (V = 5.40 x 10-13 m3 for r = 1.95mm): David McAuslan – QIP-REIDS2011 D. L. McAuslan et al., ArXiv:1104.4150 (2011) D. L. McAuslan et al., ArXiv:1104.4150 (2011) Coherence Time Through Resonator e-2τ/T Coupled into Resonator 2 e-2τ/T 2 David McAuslan – QIP-REIDS2011 D. L. McAuslan et al., ArXiv:1104.4150 (2011) D. L. McAuslan et al., ArXiv:1104.4150 (2011) Coherence Time Through Resonator Coupled into Resonator e-2τ/T 2 e-2τ/T 2 T2 = 30.8 μs David McAuslan – QIP-REIDS2011 T2 = 21.0 μs D. L. McAuslan et al., ArXiv:1104.4150 (2011) D. L. McAuslan et al., ArXiv:1104.4150 (2011) Population Lifetime Through Resonator e-Τ/T 1 David McAuslan – QIP-REIDS2011 Coupled into Resonator e-Τ/T 1 D. L. McAuslan et al., ArXiv:1104.4150 (2011) D. L. McAuslan et al., ArXiv:1104.4150 (2011) Population Lifetime Through Resonator Coupled into Resonator e-Τ/T 1 T1 = 205μs David McAuslan – QIP-REIDS2011 e-Τ/T 1 T1 = 187μs D. L. McAuslan et al., ArXiv:1104.4150 (2011) D. L. McAuslan et al., ArXiv:1104.4150 (2011) Spectral Hole Lifetime D. L. McAuslan et al., ArXiv:1104.4150 (2011) David McAuslan – QIP-REIDS2011 Optical Bistability Optical bistability and normal-mode splitting studied by Ichimura and Goto in a Pr3+:Y2SiO5 Fabry-Perot resonator [1]. Theory modified for a WGM resonator. 800μW Sweep 400μW Sweep 200μW 100μW 80μW 40μW Fitting to experimental data gives: ◦ g = 2π x 2.2 kHz. [1] K. Ichimura and H. Goto, PRA 74 (2006) David McAuslan – QIP-REIDS2011 Cavity QED Parameters This resonator: ◦ ◦ ◦ ◦ ◦ κ = 2π x 138 MHz. γ = 2π x 0.851 kHz. γh= 2π x 2.34 kHz. g = 2π x 1.73 kHz. N0 = 2.15 x 105, n0 =0.166. Need: ◦ Smaller resonators. ◦ Higher Q factors. ◦ Different materials. David McAuslan – QIP-REIDS2011 Smaller V Single point diamond turning. ◦ Crystalline resonators with R = 40 μm. ◦ Possible to reduce V by 3 orders of magnitude. [1] [1] I. S. Grudinin et al., Opt. Commun. 265 (2006) David McAuslan – QIP-REIDS2011 Higher Q We have measured Q = 2 x 108 in Y2SiO5 resonators. Q = 3 x 1011 in CaF2 [1]. Bulk losses in Y2SiO5 measured using Fabry-Perot cavity [2]. ◦ α ≤ 7 x 10-4 cm-1. ◦ Max Q ~ 3 x 108. At least 2 orders of magnitude improvement possible. Bulk losses should be lower in IR. [1] A. A. Savchenkov et al., Opt Exp. 15 (2007) [2] H. Goto et al., Opt. Exp. 18 (2010) David McAuslan – QIP-REIDS2011 Materials N0<1 for different materials. David McAuslan – QIP-REIDS2011 Conclusions Performed an investigation into strong coupling cavity QED with rare-earth-ion doped WGM resonators. Direct measurement of cavity QED parameters of a Pr3+:Y2SiO5 WGM resonator. ◦ g = 2π x 1.73 kHz. ◦ γ = 2π x 0.851 kHz. ◦ γh = 2π x 2.34 kHz. Observed optical bistability and normal-mode splitting in resonator. Achieving the strong coupling regime of cavity QED is feasible based on existing resonator technology. David McAuslan – QIP-REIDS2011