Eok Bong Kim

Sweep optical frequency synthesizer with a distributed-Bragg-reflector laser injection locked by a single component of an optical frequency comb

A sweep optical frequency synthesizer is demonstrated by using a frequency-stabilized optical frequency comb and injection-locked distributed-Bragg-reflector (DBR) laser diode. The injection-locked DBR laser acts as a single-frequency filter and, simultaneously, a high-gain amplifier of the optical frequency comb. The frequency instability of the heterodyne beat signal between two independently injection-locked DBR lasers is measured to be 2.3 x 10(-16) at 1 s averaging time. The output frequency of the sweep optical frequency synthesizer can be precisely tuned over 1 GHz, and a saturated absorption spectrum of the Cs D2 line at 852 nm is recorded by the injected DBR laser.

Absolute frequency measurement of 1S0(F = 1/2)–3P0(F = 1/2) transition of 171Yb atoms in a one-dimensional optical lattice at KRISS

We measured the absolute frequency of the optical clock transition 1S0 (F = 1/2) - 3P0 (F = 1/2) of 171Yb atoms confined in a one-dimensional optical lattice and it was determined to be 518 295 836 590 863.5(8.1) Hz. The frequency was measured against Terrestrial Time (TT; the SI second on the geoid) by using an optical frequency comb of which the frequency was phase-locked to an H-maser as a flywheel oscillator traceable to TT. The magic wavelength was also measured as 394 798.48(79) GHz. The results are in good agreement with two previous measurements of other institutes within the specified uncertainty of this work.

Selection and amplification of modes of an optical frequency comb using a femtosecond laser injection-locking technique

The authors have demonstrated the selection and the amplification of the components of an optical frequency comb using a femtosecond laser injectionlocking technique. The author used a mode-locked femtosecond Ti:sapphire laser as the master laser and a single-mode diode laser as the slave laser. The femtosecond laser injection-locking technique was applied to a filter for mode selection of the optical frequency comb and an amplifier for amplification of the selected mode. The authors could obtain the laser source selected only the desired mode of the optical frequency comb and amplified the power of the selected modes several thousand times.

Frequency-stabilized high-power violet laser diode with an ytterbium hollow-cathode lamp

We have demonstrated in an ytterbium laser cooling and trapping experiment a high-power violet extendedcavity diode laser (ECDL) stabilized to the Yb resonant transition at 398.9 nm in an Yb hollow-cathode lamp. A frequency-dispersion signal, which we obtained by applying a modulation-free dichroic-atomic-vapor laser lock technique, allowed us to stabilize the violet ECDL at a frequency stability below 1 MHz at 1-s average time and a useful output power of 15 mW.

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%.

A discretely tunable multifrequency source injection locked to a spectral-mode-filtered fiber laser comb

We present a discretely tunable multifrequency source injection locked to an optical frequency comb (OFC) based on the spectral-mode-filtered femtosecond fiber laser. The spectral-mode-filtered OFC with a 1.5 GHz mode spacing, which is based on an femtosecond fiber laser (FSFL) with 250 MHz mode spacing, was achieved using the spectral-mode-filtering method with a Fabry–Perot cavity. With the spectral-mode-filtered OFC as the master laser and two distributed-feedback lasers as the slave lasers, we simultaneously selected and amplified the desired modes of the OFC using the IL technique. We generated the coherent multifrequency optical source to synthesize in the frequency range from gigahertz to terahertz.

Direct comparison of optical frequency combs using a comb-injection-lock technique.

This paper demonstrates a direct comparison of optical frequency combs (OFCs) with different repetition rates without a stable intermediate laser using a single-mode comb-injection-lock technique. Two OFCs based on Ti:Sapphire mode-locked lasers were compared utilizing a single-mode diode laser for the selection and the amplification of one mode of an OFC by comb-injection, which makes the direct comb comparison possible. The frequencies of the two combs were found to agree within 0.019 Hz at 352 THz with the uncertainty of 0.25 Hz (7.1 x 10(-16) ). This is one of the best results among the comparisons of combs referenced to a microwave frequency. This technique simplifies the comb comparison utilities and can be applied even when repetition rates differ.

Orthogonal control of femtosecond mode-locked laser having zero carrier-offset frequency with three-axis PZT

The authors demonstrate an optical frequency synthesizer based on a femtosecond (fs) mode-locked Ti:sapphire (Ti:s) laser by simultaneously stabilizing the carrier-offset frequency f/sub ceo/ and repetition rate f/sub rep/, referenced to the Cs atomic frequency standard. By using two wide-band digital phase-detectors they realize a phase-coherent link between f/sub rep/ and f/sub ceo/ with the relation f/sub ceo/=f/sub AOM/-5/6f/sub rep//spl equiv/0, where f/sub AOM/=5/6f/sub rep/ is the phase-locked driving frequency of an acousto-optic modulator in a self-referencing interferometer and f/sub rep/=100 MHz. For the simultaneous control of f/sub rep/ and f/sub ceo/, an orthogonalization scheme using a three-axis piezoelectric transducer is introduced by which the end mirror of fs laser is controlled. As a result, the authors could stabilize all components of the fs laser comb at once with an equal frequency separation f/sub rep/=100 MHz with f/sub ceo/=0. In their optical frequency synthesizer, the frequency of the nth component (f/sub n/) is given exactly by the simple relation f/sub n/=nf/sub rep/, enabling them to use the fs laser comb as a frequency ruler in the optical frequency metrology.

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 (

Selective amplification of optical frequency comb using anti-reflect coated laser

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