Selective reflection from a potassium atomic layer with a thickness as small as λ/13. (6th September 2019) - Sargsyan, A
Abstract: We demonstrate that a method using the derivative of the selective reflection (SR) signal from a nanocell is a convenient and robust tool for atomic laser spectroscopy, achieving a nearly Doppler-free spectral resolution. The recorded linewidth of the signal from a potassium-filled cell, whose thickness ℓ lies in the range 350–500 nm, is 18 times smaller than the Doppler linewidth (∼900 MHz full width at half maximum) of potassium atoms. We also show experimentally a sign oscillation of the reflected signal's derivative with a periodicity of λ /2 when ℓ varies from 190 to 1200 nm confirming the theoretical prediction. We report the first measurement of the van der Waals atom-surface interaction coefficient C 3 = 1.9 ± 0.3 kHz × μ m 3 of potassium 4 S 1 / 2 → 4 P 3 / 2 transitions with the nanocell's sapphire windows, demonstrating the usefulness and convenience of the derivative of SR technique for cell thicknesses in the range 60–120 nm.