1. Maria Simanovskaia Raman-excited spin coherences in NV centers in diamond

2. Experiments Non-degenerate four wave mixing Electromagnetically induced transparency

3. Non-degenerate four wave mixing NV diamond sample has ~30 ppm color centers, has peak optical density of ~0.6 for 1 W/cm 2 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/cm 2 120 MHz 20 MHz D P R1 R2 S = −1 S = 0

4. Fine structure Sublevel splitting due to external magnetic field S = −1 S = +1 S = ±1 0 G1050 G B-field S = 0 2.88 GHz 120 MHz 20 MHz D P R1 R2 S = −1 S = 0

5. Non-degenerate four wave mixing 3.5° intersection angle To complete equivalence: k D = k R2 − k R1 + k P 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 Dye laser Detector Optics

6. 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/cm 2 Saturation intensities are 36 W/cm 2 and 56 W/cm 2 for optical transitions resonant with R1 and R2, respectively

7. Electromagnetically induced transparency Lambda EIT scheme Used R2, R1 and repump beams 120 MHz Coupling: R1, 280 W/cm 2 Probe: R2, 1 W/cm 2 S = −1 S = 0 R2, no diamond Freq. % Transmission 120 MHz R2, with diamond Freq. % Transmission 120 MHz R2, with diamond and R1 Freq. % Transmission 120 MHz difference

8. 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

9. Thank you!