Phase sensitivity with a coherent beam and twin beams via intensity difference detection

We focus on the Mach–Zehnder interferometer(MZI) with the input of a coherent beam and one of the bright entangled twin beams with an external power reference beam employed for measurement. The results show that the phase sensitivity can reach sub-Heisenberg limit and approach quantum Cramer–Rao bound by changing the squeezing parameters and the photon number of the coherent beam, under the phase-matching condition. The absence of the external power reference beam will degrade the performance of the phase sensitivity. Meanwhile, this scheme shows good robustness against the losses of the photon detectors. We present a detailed discussion about the phase sensitivities when the inputs are two coherent beams, or a coherent beam plus a single-mode squeezed vacuum beam based on the MZI. This scenario can be applied in the field of phase precision measurements and other optical sensors.

A study on singlet oxygen generation for tetracycline degradation via modulating the size ofα-Fe_(2)O_(3)nanoparticle anchored on g-C_(3)N_(4) nanotube photocatalyst

Photocatalysis is considered as an effective technique for mitigating ecological risks posed by residual tetracycline(TC).To improve the efficiency of this technique,it is necessary to enable photocatalysts to produce highly reactive species,such as singlet oxygen(1O2).However,due to the high activation energy of 1O2,photocatalysts can hardly produce 1O2 without assistance from external oxidants.Herein,we find that the size-reducedα-Fe_(2)O_(3)nanoparticles(~4 nm)that anchored on g-C_(3)N_(4)nanotube(α-Fe_(2)O_(3)@CNNT)can spontaneously generate ^(1)O_(2) for degradation of TC.In comparison,only hydroxyl radical(·OH)can be produced by g-C_(3)N_(4)nanotube loaded with~14 nmα-Fe_(2)O_(3)nanoparticles(α-Fe_(2)O_(3)/CNNT).Owing to the high reactivity of the ^(1)O_(2) species,the photocatalytic degradation rate(Kapp)of TC withα-Fe_(2)O_(3)@CNNT(0.056 min^(−1))was 1.8 times higher than that ofα-Fe_(2)O_(3)/CNNT.The experimental results and theoretical calculations suggested that reducing the size ofα-Fe_(2)O_(3)nanoparticles anchored on g-C_(3)N_(4)nanotube decreased the surface electron density ofα-Fe_(2)O_(3),which induces the generation of high-valent Fe(IV)active sites overα-Fe_(2)O_(3)@CNNT and turns the degradation pathway into a unique ^(1)O_(2) dominated process.This study provides a new insight on the generation of ^(1)O_(2) for effective degradation of environmental pollutant.

Controlled generation of order-switchable cylindrical vector beams from a Nd:YAG laser

We reporte and demonstrate a solid-state laser to achieve controlled generation of order-switchable cylindrical vector beams(CVBs).In the cavity,a group of vortex wave plates(VWPs)with two quarter-wave plates between the VWPs was utilized to achieve mode conversion and order-switch of CVBs.By utilizing two VWPs of first and third orders,the second and fourth order CVBs were obtained,with mode purities of 96.8%and 94.8%,and sloping efficiencies of 4.45%and 3.06%,respectively.Furthermore,by applying three VWPs of first,second,and third orders,the mode-switchable Gaussian beam,second,fourth,and sixth order CVBs were generated.