Single ion fluorescence excited with a single mode of an UV frequency comb

Abstract

Optical frequency combs have revolutionized the measurement of optical frequencies and improved the precision of spectroscopic experiments. Besides their importance as a frequency-measuring ruler, the frequency combs themselves can excite target transitions (direct frequency comb spectroscopy). The direct frequency comb spectroscopy may extend the optical frequency metrology into spectral regions unreachable by continuous wave lasers. In high precision spectroscopy, atoms/ions/molecules trapped in place have been often used as a target to minimize systematic effects. Here, we demonstrate direct frequency comb spectroscopy of single 25Mg ions confined in a Paul trap, at deep-UV wavelengths. Only one mode out of about 20,000 can be resonant at a time. Even then we can detect the induced fluorescence with a spatially resolving single photon camera, allowing us to determine the absolute transition frequency. The demonstration shows that the direct frequency comb spectroscopy is an important tool for frequency metrology for shorter wavelengths where continuous wave lasers are unavailable.

Quantum Zeno Effect assisted Spectroscopy of a single trapped Ion

“…Larger comb power can be used to broaden the lines and optimizing the alignment of the cooling laser and the comb. The observation is in contrast with direct fluorescence collection method for which the entire comb power and longer measurement time had to be employed to obtain a comparable signal-to-noise ratio 31 .…”

“…In determining the centroid frequency, the magnetic-field component along the spectroscopy beam is measured by performing radio frequency spectroscopy of the ground state magnetic sublevels. The mode number of the comb is determined using our previous spectroscopy results 30 , 31 .…”

Quantum Interference Line Shifts of Broad Dipole‐Allowed Transitions

“…However, when driving a dipole-allowed single-photon transition in this way, [22] the emissions that belong to the various laser modes take place at different laser frequencies. In the extreme case, one might use a frequency comb with typically 10 5 equidistant laser frequencies.…”

“…Detecting the final state instead of the fluorescence means that we can simply evaluate the scattering cross section (20) or (22) with the matrix elements (18) to obtain the line shape function: …”

All-solid-state VUV frequency comb at 160 nm using high-harmonic generation in nonlinear femtosecond enhancement cavity

“…The extension of frequency comb metrology beyond the UV spectral range into the DUV [1][2][3][4] and even into the VUV and XUV [5][6][7][8][9] gives an opportunity to measure new important atomic and molecular transitions for testing quantum electrodynamics or to look for new atomic clock transitions. Perturbative non-linear conversion methods in solids such as second-and sum-frequency generation are limited at about 160 nm by the transparency of the used non-linear crystal [10][11][12], and have been realized at low (kHz or lower) repetition rates.…”