Chang Yong Park

Generation of 578-nm yellow light over 10 mW by second harmonic generation of an 1156-nm external-cavity diode laser

578-nm yellow light with an output power of more than 10 mW was obtained using a waveguide periodically-poled-lithium-niobate crystal as a nonlinear medium for second harmonic generation, which is the highest output power at this wavelength using second harmonic generation of a solid state laser source without an enhancement ring cavity, to our knowledge. To achieve this result we made a high power 1156-nm external-cavity diode laser with the maximum output power of more than 250 mW. This system is expected to be an excellent alternative to the system using the sum-frequency generation with the advantage of simplicity and cost-effectiveness, and will be used as a clock laser of the ytterbium optical lattice clock with robust and reliable operation.

Narrow linewidth 578 nm light generation using frequency-doubling with a waveguide PPLN pumped by an optical injection-locked diode laser.

This study demonstrates 578 nm yellow light generation with a narrow linewidth using a waveguide periodically poled lithium niboate (PPLN) and an optical injection-locked diode laser. The frequency of an external cavity diode laser used as a master laser operating at 1156 nm in optical injection-locking mode was locked into a high-finesse cavity with the Pound-Drever-Hall technique, which results in a linewidth reduction of the master laser. The linewidth of the master laser was estimated to be approximately 1.6 kHz. In an effort to amplify the optical power, a distributed feed-back laser was phase-locked to the master laser by an optical injection-locking technique. A waveguide PPLN was used for second harmonic generation. Frequency-doubled yellow light of approximately 2.4 mW was obtained with a conversion efficiency of 6.5%.

The uncertainty associated with the weighted mean frequency of a phase-stabilized signal with white phase noise

The weighted mean is widely used in combining data sets of experimental measurements with a weight proportional to the value of the data number divided by the sample variance in a conventional method. However, this standard procedure is not appropriate for obtaining the weighted mean frequency of a phase-stabilized signal with white phase noise, since the data are autocorrelated. The autocorrelation is obtained in the case of white phase noise and a new weighting method is proposed. Using this, the uncertainty associated with the weighted mean frequency of a phase-stabilized signal with white phase noise is given. The effect of counter dead-time is also discussed.

Linewidth reduction of a distributed-feedback diode laser using an all-fiber interferometer with short path imbalance

The linewidth of a distributed-feedback (DFB) diode laser at 1156 nm, of which free-running linewidth was 3 MHz, was reduced to 15 kHz using an all-fiber interferometer with 5-m-long path imbalance. Optical power loss and bandwidth limitation were negligible with this short optical fiber patch cord. This result was achieved without acoustic and vibration isolations, and the frequency lock could be maintained over weeks. In addition to its simplicity, compactness, robustness, and cost-effectiveness, this technique can be applied at any wavelength owing to the availability of DFB diode lasers and fiber-optic components.

Demonstration of an optical frequency synthesizer with zero carrier-envelope-offset frequency stabilized by the direct locking method

We developed an optical frequency synthesizer (OFS) with the carrier-envelope-offset frequency locked to 0 Hz achieved using the direct locking method. This method differs from a conventional phaselock method in that the interference signal from a self-referencing f-2f interferometer is directly fed back to the carrier-envelope-phase control of a femtosecond laser in the time domain. A comparison of the optical frequency of the new OFS to that of a conventional OFS stabilized by a phase-lock method showed that the frequency comb of the new OFS was not different to that of the conventional OFS within an uncertainty of 5.68x10(-16). As a practical application of this OFS, we measured the absolute frequency of an acetylene-stabilized diode laser serving as an optical frequency standard in optical communications.

Comparison of Fiber-Based Frequency Comb and Ti:Sapphire-Based Frequency Comb

For the first time we compare two kinds of optical frequency combs, one of which is based on a Ti:sapphire femtosecond laser and the other is based on a mode-locked erbium-doped fiber laser. The comparison is performed by measuring an optical frequency standard with these two combs simultaneously. The two frequency measurements agree within 1.8 Hz (

Drift-Compensated Low-Noise Frequency Synthesis Based on a cryoCSO for the KRISS-F1

3.8{times}10^{-15}

Optical frequency comb comparison between optical clock mode and optical frequency synthesizer mode

) with the uncertainty of 17.2 Hz (

Current status of an atomic gravimeter developing at KRISS

3.6{times}10^{-14}

KRISS atomic fountain clock: Current status

), from which it can be concluded that the Ti:sapphire-based frequency comb and the fiber-based frequency comb have no systematic discrepancy at this level of uncertainty.