Ma Long-Sheng

Clock-transition spectrum of 171Yb atoms in a one-dimensional optical lattice

An optical atomic clock with 171Yb atoms is devised and tested. By using a two-stage Doppler cooling technique, the 171Yb atoms are cooled down to a temperature of 6?3 ?K, which is close to the Doppler limit. Then, the cold 171Yb atoms are loaded into a one-dimensional optical lattice with a wavelength of 759 nm in the Lamb?Dicke regime. Furthermore, these cold 171Yb atoms are excited from the ground-state 1S0 to the excited-state 3P0 by a clock laser with a wavelength of 578 nm. Finally, the 1S0?3P0 clock-transition spectrum of these 171Yb atoms is obtained by measuring the dependence of the population of the ground-state 1S0 upon the clock-laser detuning.

Two-hertz-linewidth Nd:YAG lasers at 1064 nm stabilized to vertically mounted ultra-stable cavities

Two Nd:YAG lasers operating at 1064 nm are separately servo-locked to two vertically mounted ultra-stable cavities. The optical heterodyne beat between two cavity-stabilized lasers shows that the linewidth of each laser reaches 2 Hz and the average frequency drift reduces to less than 1 Hz/s.

Progress and trend of narrow-linewidth lasers

High frequency stability, narrow-linewidth lasers have been long dreamed of since the invention of the laser. They have recently developed dramatically due to the advent of optical clocks. State-of-the-art narrow-linewidth lasers have been constructed by using the Pound-Drever-Hall (PDH) technique to lock the laser frequencies to the resonance of ultra-stable external optical cavities with high finesse. This paper introduces the developments of narrow-linewidth lasers, with a focus on the improvements of length stability of optical reference cavities, including optical cavity designs of vibration insensitivity and low thermal noise. Future trends and alternative methods for narrow-linewidth lasers are also discussed.

Coherence transfer from 1064 nm to 578 nm using an optically referenced frequency comb

A laser at 578 nm is phase-locked to an optical frequency comb (OFC) which is optically referenced to a subhertz-linewidth laser at 1064 nm. Coherence is transferred from 1064 nm to 578 nm via the OFC. By comparing with a cavity-stabilized laser at 578 nm, the absolute linewidth of 1.1 Hz and the fractional frequency instability of 1.3 × 10−15 at an averaging time of 1 s for each laser at 578 nm have been determined, which is limited by the performance of the reference laser for the OFC.

Observation of Collimated Atoms by Light Pressure Force in Absorption Cell

Experimental observation of laser cooling and collimation of moving atoms in an absorption cell by light pressure force of an intense standing light wave field is reported. The hyper fine structure of atomic sodium has been observed due to the cooled and collimated atoms. The mechanism of laser cooling and collimation of atoms is discussed.

Vibration insensitive optical ring cavity

The mounting configuration of an optical ring cavity is optimized for vibration insensitivity by finite element analysis. A minimum response to vertical accelerations is found by simulations made for different supporting positions.

STUDY OF THE DOPPLER-FREE OPTICAL-OPTICAL TRIPLE-RESONANCE(DF-OOTR) SPECTROSCOPY AND ITS LINESHAPES

The Doppler-free optical-optical triple-resonance (DF-OOTR) spectroscopy and its line-shapes have been studied in detail theoretically and experimentally. The line center, linewidth and lineshape of an isolated DF-OOTR spectra compenent have been derived by using density matrix motion equation describing the interaction of a three-level system with three optical fields. The variations of the lineshape symmetry, the relative position and the strength of the Doppler-free Lorentzian dip to its background are comparable to the experimental traces varying with the relative intensities of the two mutual-saturating probe laser beams, as well as with the detuning of the first pumping laser from the intermediate level. The DF-OOTR technique shows a distinguished advantage especially in the labeling of the transitions and in the determination of absolute position of the upper level affected by perturbation shift, as these happened often in the dense molecular highly excited states.

A new Doppler-free optical-optical triple-resonance (DF-OOTR) spectroscopy

A new Doppler-free optical-optical triple-resonance (DF-OOTR) spectroscopy is reported for the first time. This high resolution technique is simply carried out using one single mode laser like Doppler-free two-photon spectroscopy, and can reach arbitrary levels in the high-lying g-parity states like the optical-optical double-resonance technique in atomic or molecular systems. It is an effective but simple method for the systematic study of atomic or molecular structures and their intra or internal dynamics.

Optical-Optical Double-Resonance Excitation Spectra of the (6d)1Πg, (7d)1Πg High-Lying Rydberg States in Na2

Two 1Πg states of Na2 for v ≤ 13 have been observed by using optical-optical double resonance (OODR) fluorescence excitation spectroscopy. The intermediate levels in B1Πu state are identified by the numerical calculations with the molecular constants for B1Πu ← X1Σg+ transitions and confirmed by the complementary A1Σu+ ← X1Σg+ polarization spectra. Absolute vibrational numberings of the (6d)1Πg and (7d)1Πg states are determined by comparing the experimental OODR excitation intensities with the simulated Franck-Condon factors. The Dunham coefficients and the Rydberg-Klein-Rees (RKR) potential energy curves of the (6d)1Πg, (7d)1Πg states are reported.