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Raman-excited spin coherences in NV centers in diamond. Maria Simanovskaia. Experiments. Non-degenerate four wave mixing Electromagnetically induced transparency. Non-degenerate four wave mixing.
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Raman-excited spin coherences in NV centers in diamond Maria Simanovskaia
Experiments • Non-degenerate four wave mixing • Electromagnetically induced transparency
Non-degenerate four wave mixing • NV diamond sample has ~30 ppm color centers, has peak optical density of ~0.6 for 1 W/cm2 probe intensity at 15 K • Used one dye laser, with acousto-optic frequency shifters • Downshifted R1, R2, P from original frequency by 400, 280, and 420 MHz, respectively • Intensities of R1, R2, P and repump beam were 1.2, 1.6, 5.6, 10 W/cm2 20 MHz R1 P R2 D S = −1 120 MHz S = 0
20 MHz R1 P R2 D S = −1 120 MHz S = 0 S = ±1 120 MHz 2.88 GHz S = 0 B-field 0 G 1050 G Fine structure • Sublevel splitting due to external magnetic field S = +1 S = −1
Non-degenerate four wave mixing • 3.5° intersection angle • To complete equivalence: kD = kR2 − kR1 + kP • 514.5 nm argon laser used as a repump • Protect against spectral hole burning • Helmholtz coils • Laser beams: linearly polarized, focused by 150-mm focal length lens • 15 K maintained by Janis helium-flow cryostat Detector Dye laser Optics
Results: NDFWM • Narrow linewidth is taken as evidence of Raman process • Homogeneous width of optical transition (~50 MHz) • Inhomogeneous width of spin transition (5 MHz) • Recall: for NDFWM, intensities of R1, R2, P and repump beam were 1.2, 1.6, 5.6, 10 W/cm2 • Saturation intensities are 36 W/cm2 and 56 W/cm2 for optical transitions resonant with R1 and R2, respectively
Electromagnetically induced transparency • Lambda EIT scheme • Used R2, R1 and repump beams R2, no diamond R2, with diamond R2, with diamond and R1 Probe: R2, 1 W/cm2 Coupling: R1, 280 W/cm2 % Transmission % Transmission % Transmission S = −1 120 MHz Freq. Freq. 120 MHz 120 MHz 120 MHz Freq. S = 0 difference difference difference
Results: EIT • Max value of transparency is 17% of background absorption • 70% of what is possible (random orientation of NV center in diamond) • EIT linewidth is substantially smaller than laser jitter (~100 MHz) and the optical homogeneous linewidth