Improved Measurement of the Differential Polarizability Using Co-Trapped Ions.

We present a novel approach for measuring the differential static scalar polarizability of a target ion utilizing a "polarizability scale" scheme with a reference ion co-trapped in a linear Paul trap. The differential static scalar polarizability of the target ion can be precisely extracted by measuring the ratio of the ac Stark shifts induced by an add-on infrared laser shed on both ions. This method circumvents the need for the calibration of the intensity of the add-on laser, which is usually the bottleneck for measurements of the polarizability of trapped ions. As a demonstration, ^{27}Al^{+} (the target ion) and ^{40}Ca^{+} (the reference ion) are used in this work, with an add-on laser at 1068 nm injected into the ion trap along the trap axis. The differential static scalar polarizability of ^{27}Al^{+} is extracted to be 0.416(14) a.u. by measuring the ratio of the ac Stark shifts of both ions. Compared to the most recent result [Phys. Rev. Lett. 123, 033201 (2019)PRLTAO0031-900710.1103/PhysRevLett.123.033201], the relative uncertainty of the differential static scalar polarizability of ^{27}Al^{+} is reduced by approximately a factor of 4, to 3.4%. This improvement is expected to be further enhanced by using an add-on laser with a longer wavelength.

[Study on the Supercontinuum Generation with Femtosecond Pulse in Photonic Crystal Fiber].

Physical mechanism of supercontinuum generation in photonic crystal fiber by femtosecond laser pulse has been investigated experimentally. In this study, we used the tunable output wavelength Ti: sapphire optical parametric amplifier as the pump source and the fiber spectrometer acquired the spectrogram of supercontinuum generation in photonic crystal fiber under different power and wavelength conditions, then we normalized the spectrograms and make a comparison of them. PCF supercontinuum differences affected by physical mechanisms were analyzed. We found that when increasing the incident pump pulse power, the spectral width will be gradually widened, there are more peaks, part of the energy will transfer in to the short-wave- length region; as long as it reaches a certain intensity, width of supercontinuum finally saturated, the shape of supercontinuum was also stabilized. As the incident power was settled at 300 milliwatt and the length of PCF was settled at 105 millimeter, experimental results show that width and shape of supercontinuum are affected by the wavelength of pump pulse, in the range of 760 to 840 nm, there appears more and more peaks with the increase of incident wavelength; at anomalous dispersion the spectrogram of supercontinuum generation will be more flat and more wider as the wavelength of pump pulse closer to zero point.