Investigation of oscillator strength enhancement of electric dipole forbidden transitions in optical near field

1亚波长狭缝阵列产生的近场电偶极禁戒跃迁效率的估算采用本课题提出的时域有限差分法（FDTD）计算了50 nm厚金膜上50 nm宽周期性狭缝阵列产生的近场光场。的电四极（E2）和磁偶极子（M1）的转换，这是由激发光场的梯度修改的效率，计算的光场进行了评估。在入射光的光偏振垂直于狭缝方向的情况下，E2跃迁效率大大提高，而在该偏振的M1跃迁中看不到这种提高。E2跃迁效率的大幅度提高主要来源于狭缝边缘的场集中和大的空间调制。在入射光平行于狭缝的情况下， ...更多信息 对于E2和M1跃迁，水泥都很小，这与修正因子（k_0ld）^一致<-2>，其中K_0和d分别是真空中均匀传播光的波数和狭缝宽度。计算了亚波长狭缝阵列产生的近场效应对Cu_2O中1 s邻位激子激发效率的影响。2亚波长狭缝阵列观察Cu_2O中1 s-邻位激子的发射光谱利用电子束光刻方法，在Cu_2O晶体表面制备了厚度为50 nm的周期性金狭缝阵列。我们证实了通过狭缝阵列可以观察到Cu_2O中1 s邻位激子的电四极（E2）和电偶极（El）跃迁的发射。到目前为止，狭缝阵列对E2发射的影响还没有被检测到。3 O_2分子磁偶极跃迁的观测我们建立了一个偶极激光光谱系统，观测了O_2分子磁偶极（M1）跃迁（A波段，763 nm）引起的光吸收。为了提高系统的灵敏度，我们将系统与离轴腔合并。已证实，可以以足够的光谱分辨率测量吸收光谱。同时也证实了腔内多次反射对提高灵敏度的作用。少

1 Estimation of electric dipole forbidden transition efficiency in optical near fields generated by a sub-wavelength slit arrayOptical near fields generation by a periodically structured 50 nm width slit array of a 50 nm thick gold film were calculated with the FDTD (Finite Difference Time Domain) method, which was developed in this project. The efficiencies of the electric quadrupole (E2) and magnetic dipole (M1) transitions, which are modified by the gradient of the excitation light field, were evaluated for the calculated optical fields. The E2 transition efficiency is largely enhanced in the case where the light polarization of the incident light is perpendicular to the slit direction while such enhancement is not seen for the M1 transition in this polarization. The large enhancement of the E2 transition efficiency mainly originates from the field concentration and the large spatial modulation at the slit edge. In the case where the incident light is parallel to the slit, the enhan … More cement is small for both the E2 and Ml transition, which is consistent with the modification factor of (k_0ld)^<-2>, where K_0 and d are the wavenumber of the homogenously propagating light in vacuum and the slit width, respectively. The enhancement of the E2 excitation efficiency was also calculated for the 1s-ortho exciton in Cu_2O in the optical near field generated by a sub-wavelength slit array. It was suggested that the enhancement is affected by the surface plasmon resonance.2 Observation of emission spectra of the 1s-ortho exciton in Cu_2O through a sub-wavelength slit arrayWith an electron beam lithographic method, a periodically structured gold slit array with 50 nm thickness was fabricated on a Cu_2O crystal surface. We confirmed that the emissions of the electric quadrupole (E2) and dipole (El) transitions of the 1s-ortho excitons in Cu_2O can be observed through the slit array. So far, effects of the slit array to the E2 emission have not been detected. The polarization and slit-period dependences of the emission intensities were observed.3 Observation of the magnetic dipole transition of O_2We developed a spectroscopic system with a dipole laser to observe the light absorption due to the magnetic dipole (M1) transition of O_2 (A-band, 763 nm). In order to make the system high sensitive, we merged the system with an off-axis cavity. It was confirmed that the absorption spectrum can be measured with sufficient spectral resolution. The effect of multi-reflection in the cavity for the increase in the sensitivity was also confirmed. Less