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.
A high-power all-fiber single-frequency polarization-maintained（PM）laser operating at 1 083 nm is demonstrated using a master oscillator power amplifier（MOPA）structure.The seed source of this MOPA laser system is an in-house-built ring-cavity fiber oscillator.Four-stage amplification configuration is employed, in which the maximal output power of the main amplifier is 90.4 W,corresponding to a conversion efficiency of 72.5%.The polarization extinction ratio of the output light is 13 dB.The amplified spontaneous emission is suppressed by a factor of over 25 dB,and no stimulated Brillouin scattering effect is observed when a large-mode-area and high absorption coefficient PM gain fiber is employed.
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.
