We present a high-efficiency 532 nm green light conversion from an external cavity-enhanced second harmonic generation(SHG)with a periodically poled KTP crystal(PPKTP).The cavity is a bow-tie ring configuration with a unitized structure.When the impedance matching is optimized,the coupling efficiency of the fundamental is as high as 95%.Taking into account both the high power output of the second harmonic and the stability of the system,we obtain over 500 mW green passing through the output cavity mirror,corresponding to a net conversion efficiency higher than 75.2%.Under these operating conditions,the power stability is better than±0.25%during 5 h.It is the highest conversion efficiency and power stability ever produced in the bow-tie ring cavity with PPKTP for 532 nm generation.
The tunneling between double wells of atom in crossed electromagnetic fields is investigated by a one-dimensional Hamiltonian model.The crossed fields induced outer well is apart from the nuclear origin and it is very difficult to access by means of spectroscopy but it will be possible if there exists the tunneling of the electron between the outer well and the Coulomb potential predominated well at the nuclear origin.A one-dimensional quantum calculation with B-spline basis has been performed for hydrogen atom in crossed fields accessible in our laboratory,at B=0.8 T and F= 220 V·cm 1.The calculation shows that the wavefunctions of some excited states close to the Stark saddle point in the outer well extend over to the Coulomb potential well,making it possible to penetrate the quantum information of the outer well.However,the tunneling rate is very small and the spectral measurement of the transitions from the ground state should be of a high resolution and high sensitivity.
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 observe strong energy-dependent quantum defects in the scaled-energy Stark spectra for |M| = 1 Rydberg states of barium atoms at three scaled energies: ε = 2.000,ε = 2.500 and ε = 3.000.In an attempt to explain the observations,theoretical calculations of closed orbit theory based on a model potential including core effect are performed for non-hydrogenic atoms.While such a potential has been uniformly successful for alkali atoms with a single valence electron,it fails to match experimental results for barium atoms in the 6snp Rydberg states with two valence electrons.Our study points out that this discrepancy is due to the strong perturbation from the 5d8p state,which voids the simple approximation for constant quantum defects of principle quantum number n.
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.
