We show two external cavity-enhanced second-harmonic generations of 922 nm with periodically poled potassium titanyl phosphate crystal,whose doubling cavities are locked separately with Hansch-Couillaud and intra-modulation methods.The outputs of second-harmonic generation reach 310 mW,54.8%of the conversion efficiency from the Ti:sapphire laser with the crystal length of 10 mm,and 208 mW,59% of the conversion efficiency from the MOPA system with the crystal length of 30 mm.It consists of heterodyning the Ti:sapphire laser and the MOPA system,and compares the phase of the beat frequency signal with the phase of a reference RF local oscillator.The resulting phase error is used as a feedback signal and fed back to the reference cavity of the Ti:sapphire laser to lock the two lasers in phase.A stable blue power of 520 mW is obtained,which supplies enough power for the cooling and trapping step of the strontium (Sr)optical lattice clock.Four stable isotopes of Sr, 84 Sr, 86 Sr, 87 Sr,and 88 Sr,are detected by probing the laser during a strong 460.7-nm cycling transition(5s 21 S0?5s5p 1 P1).
We demonstrate two self-injection locking extended cavity diode lasers(ECDLs)using resonant optical feedback independently from s-and p-polarizations of a monolithic folded Fabry–Perot confocal cavity(MFC).The relative frequency shift of adjacent axial modes of s resonance and p resonance of MFC is around 1.030 GHz.Beat note measurements between the two ECDLs are performed and present a relative linewidth of 4 kHz.With the help of a narrow-linewidth reference laser,the linewidth of s-component and p-component ECDLs are measured to be about 32 kHz and 40 kHz,respectively.
