Sergey Slyusarev

Phase-coherent optical frequency division by 3 of 532-nm laser light with a continuous-wave optical parametric oscillator

Phase-locked 3:1 division of an optical frequency was achieved with a continuous-wave monolithic optical parametric oscillator (OPO) pumped by a 532-nm Nd:YAG laser, by use of 5% MgO-doped LiNbO(3) as a nonlinear optical crystal. The OPO generated signal light (798 nm) with 4-mW power and idler light (1596 nm) with 3-mW power for a pump power of 68 mW. Approximately 2microW of second harmonics (SHs) of the idler light was produced by external-cavity-enhanced SH generation by use of a periodically poled LiNbO(3) crystal. The beat signal between the signal light and the SH of the idler light was observed with a signal-to-noise ratio of 40 dB at a 10-kHz bandwidth and was successfully phase locked to a signal from a synthesizer through the electro-optic effect of the crystal.

Accuracy of an Optical Parametric Oscillator as an Optical Frequency Divider

Abstract The coherence and the accuracy of a cw optical parametric oscillator (OPO) as an optical frequency divider was measured. The phase coherence between the pump and the signal or the idler was confirmed. The accuracy of the OPO as an optical frequency divider was found to be better than 5 × 10−18.

Long-term, mode-hop-free operation of a continuous-wave, doubly resonant, monolithic optical parametric oscillator

Abstract More than 24-h mode-hop-free operation of a continuous-wave doubly resonant monolithic optical parametric oscillator (OPO) was demonstrated using 5% MgO-doped LiNbO 3 as a nonlinear crystal. The OPO was pumped by a 532-nm Nd:YAG laser with 68 mW power, and generated 4 mW of signal power at 807 nm and 3 mW of the idler power at 1561 nm. The OPO maintained a single longitudinal signal and idler mode pair even under the free running condition, owing to the high mechanical stability of the monolithic structure and the strong thermal self-locking mechanism. By stabilizing the crystal temperature so as to maintain the output power constant, the drift of the output power could be suppressed completely and a power fluctuation of 1.3% rms was achieved.

Frequency measurement of accurate sidebands of an optical frequency comb generator

Abstract The accuracy of the optical sideband generation of an optical frequency comb generator (OFCG) was examined. The fundamental light and its second harmonics from a YAG laser were used as input to the OFCG and as pump light to an optical parametric oscillator (OPO), respectively. The frequency between the +15th order OFCG sideband and the OPO signal light was compared with that between the -15th order sideband and the idler. The frequency shift of the generated sideband was estimated to be smaller than 6 × 10 −13 at a frequency span of 276 GHz.

Optical Frequency Measurement Using Chirped-Mirror-Dispersion-Controlled Mode-Locked Ti:Al2O3 Laser

An optical frequency measurement system based on an octave-spanning optical frequency comb generated by a chirped-mirror-dispersion-controlled mode-locked Ti:Al2O3 laser and a photonic-crystal fiber is developed. All of the modes of the octave-spanning optical frequency comb are frequency-stabilized to a microwave frequency standard, where the carrier-envelope offset frequency is phase-locked with self-referencing of the comb. We investigate the methods of controlling carrier-envelope offset frequency in a chirped-mirror-dispersion-controlled mode-locked laser. The rotation of a pair of chirped mirrors is useful for setting the bias of carrier-envelope offset frequency. Although our mode-locked laser has a low pulse-repetition frequency of 150 MHz, a high signal-to-noise ratio in beats results in the direct measurement of beat frequency with a laser to be measured using a frequency counter, and enables us to phase lock carrier-envelope offset frequency merely by using a mixer analogously without the need for a prescaler, with a servo bandwidth at approximately 500 kHz. The uncertainty of our optical frequency measurement system, besides the uncertainty of microwave reference frequency, is 4×10-14, and is limited by the uncertainty of the rf synthesizer used for phase locking and by that of the beat frequency measurement. Frequency measurements of an iodine-stabilized frequency-doubled Nd:YAG laser at 532 nm, an iodine-stabilized He–Ne laser at 633 nm and a rubidium two-photon-absorption stabilized extended-cavity laser diode at 778 nm are conducted. The results contributed to the revision of the practical realization of the metre adopted by the International Conference on Weights and Measures (CIPM) in 2001.

Long Term Operation of a CW Doubly Resonant Optical Parametric Oscillator

Long-term operation of a cw doubly resonant optical parametric oscillator was demonstrated. The minimum threshold was 9mW and the slope efficiency was 25%. Using a rigid structure cavity and a stable pump laser, it operated in a single longitudinal signal-idler mode pair for over 3 h without any mode hopping.

Frequency control of a chirped-mirror-dispersion-controlled mode-locked Ti:Al2O3 laser for comparison between microwave and optical frequencies

The use of an optical frequency comb generated by an ultrafast mode-locked laser has been realized as a promising method of the direct comparison between microwave and optical frequencies. We are currently investigating frequency control of a chirped-mirror-dispersion-controlled mode-locked Ti:Al2O3 laser. We stabilized the pulse repetition rate frep to a rf synthesizer locked to a cesium (Cs) clock to the Allan deviation of 4 X 10-12 in 1 s. We found that the position of the crystal, rotation of the chirped mirrors, and change of the pump-laser power can be used in controlling the carrier-envelope offset frequency fCEO. We extended the span of the comb to over one octave, i.e., from 530 nm to 1190 nm, at -20 dB using a photonic-crystal fiber made at the University of Bath. We are currently trying to measure the frequency of an iodine-stabilized Nd:YAG laser using a floating ruler of a f:2f frequency interval chain. We detected the self-referencing beat between the fundamental and second- harmonic frequencies of the comb, which will enable further precise comparison between microwave and optical frequencies through the control of the fCEO.

Realization of a 3:2 optical frequency divider using a cw optical parametric oscillator

Summary form only given. The 3:1 optical frequency divider is one of the key devices to realize an all solid state frequency chain. We report here the 3:1 division with a cw optical parametric oscillator in the visible and the first observation of the beat signal between the signal and the second harmonics (SH) of the idler; toward the realization of an truly phase coherent 3:1 optical frequency divider.

Characteristics of continuous-wave double-resonant optical parametric oscillators as spectroscopic tools

Tuning and output characteristics of widely-tunable, continuous-wave, doubly-resonant optical parametric oscillators (cw-DROs) are reported from a practical viewpoint. Using 5% MgO-doped LiNbO3 as a nonlinear crystal, we fabricated a 532 nm pumped, monolithic cw-DRO which is tunable over 1 octave from 777 nm to 1687 nm. The threshold of the DRO was 10 mW and the DRO produced the signal power of 4 mW and the idler power of 3 mW when it is pumped at 68 mW pump-power. It operated very stably in a single-longitudinal-mode pair of signal and idler without any mode-hopping over 1 day even under free-running condition, owing to the high mechanical stability of the monolithic cavity and the strong thermal self-locking mechanism. By stabilizing the crystal temperature so as to maintain the output power constant, the output power fluctuation was suppressed to 1.3% rms. The arbitrary longitudinal-mode-selection was possible by combining the crystal temperature and the pump-frequency tuning. By the simultaneous control of the crystal temperature and the pump- frequency, the continuous frequency tuning over 500 MHz was achieved.

Continuous-wave RbTiOAsO4 Optical Parametric Oscillator in Optical Frequency Interval Divider Scheme.

A continuous-wave optical parametric oscillator (OPO) of RbTiOAsO4 (RTA) is used as a light source for an optical frequency interval divider. Pumped by 1.5 W of the 532-nm second harmonic of the high power YAG laser, the OPO generates a power-stable signal-idler mode pair at 912 nm and 1292 nm with an output of 40 mW and spectral bandwidth of less than 5 KHz. The tuning characteristics are examined in detail. The result of the optical frequency interval division is presented.