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We report experiments on the observation of the 1S0-3P0 transition spectrum of 88Sr in the Lamb-Dicke regime. After going through a two-stage magneto-optical trap (MOT), 88Sr cold atoms with number of about 1 \times 105 and a longitudinal temperature of 8.4 μK are loaded into a one-dimensional (1D) optical lattice, which is realized with a semiconductor laser at 813.4 nm. Using the magnetic field-inducing 3P1 state mixing into 3P0 state, the spectroscopy of the 1S0-3P0 transition with a linewidth of 180 Hz is detected.

We report the 87Sr optical lattice clock developed at the National Time Service Center. We achieved a closed-loop operation of the optical lattice clock based on 87Sr atoms. The linewidth of the spin-polarized clock peak is 3.9 Hz with a clock laser pulse length of 300 ms, which corresponds to a Fourier-limited linewidth of 3 Hz. The fitting of the in-loop error signal data shows that the instability is approximately , affected primarily by the white noise. The fractional frequency difference averages down to for an averaging time of 3000 s.

In this paper, we report on the active filtering and amplification of a single mode from an optical femtosecond laser comb with mode spacing of 250 MHz by optical injection of two external-cavity diode lasers operating in cascade to build a narrow linewidth laser for laser cooling of the strontium atoms in an optical lattice clock. Despite the low injection of individual comb mode of approximately 50 nW, a single comb line at 689 nm could be filtered and amplified to reach as high as 10 mW with 37 dB side mode suppression and a linewidth of 240 Hz. This method could be applied over a broad spectral band to build narrow linewidth lasers for various applications.

We report a new method for obtaining a stable single-frequency Yb-doped fiber laser by introducing a graphene film into a fiber loop mirror combined with a simple linear cavity. The graphene film acts as a saturable absorber so as to form a dynamic absorbing grating in the 3 dB fiber loop. This grating is like a narrow-band filter for discriminating and selecting longitudinal modes. Moreover, we use a polarization controller in the linear resonator to suppress the spatial hole burning effect. The maximum output power is 16 mW at 1 064 nm with a pump power of 110 mW at 975 nm, the slope efficiency is 15%, and the SNR is about 60 dB. To the best of our knowledge, this is the first demonstration of a 1 064 nm single-frequency laser based on a linear cavity with a graphene-loop mirror filter.