In this work, we discuss the scattering features of a dipolar particle made of large refractive index material by employing the concept of virtual gain and virtual loss. The virtual gain and loss can be achieved in a lossless passive nanostructure by shaping the temporal waveform of incident signals in the complex frequency plane. We show that an appropriate tuning of excitation time of the impinging field allows to capture and release the electromagnetic energy on-demand for an arbitrary time scale in a lossless nanosphere. Thus, the nanosphere obliges to emit monochromatic magnetic light which can be tuned throughout the whole visible spectrum by varying the size of the nanosphere. This proposal may find fruitful applications in lab-on-a-chip technologies and the realization of monochromatic sectoral multipole light source with a large quality factor at nanoscale level.

在这项工作中，我们利用虚增益和虚损耗的概念讨论了由大折射率材料制成的偶极粒子的散射特性。通过在复频率平面中对入射信号的时间波形进行整形，可以在无损无源纳米结构中实现虚拟增益和损耗。我们表明，适当调整撞击场的激发时间允许在无损纳米球中的任意时间尺度内按需捕获和释放电磁能。因此，纳米球必须发射单色磁光，可以通过改变纳米球的尺寸在整个可见光谱范围内进行调谐。