Efficient electrical generation of mid-infrared light is challenging because of the dearth of materials with natural dipole-active electronic transitions in this spectral region. One approach to solve this problem is through quantum-engineering of the electron dispersion to create artificial transitions, as in quantum cascade devices. In this work we propose an alternative method to generate mid-infrared light, utilizing the coupling between longitudinal and transverse degrees of freedom due to the nonlocal optical response of nanoscopic polar dielectric crystals. Polar crystals support sub-diffraction photonic modes in the mid-infrared. They also support longitudinal phonons, which couple efficiently with electrical currents through the Fröhlich interaction. As we have shown in previous theoretical and experimental works, these two degrees of freedom can hybridize forming longitudinal-transverse polaritons. Here we theoretically demonstrate that longitudinal-transverse polaritons can be efficiently generated by electrical currents, leading to resonant narrowband photonic emission. This approach can therefore be utilised to electrically generate far-field mid-infrared photons in the absence of dipole-active electronic transitions, potentially underpinning a novel generation of mid-infrared optoelectronic devices.

中文翻译：

---

表面声子极化激元的发电

中红外光的高效发电具有挑战性，因为在该光谱区域缺乏具有天然偶极活性电子跃迁的材料。解决这个问题的一种方法是通过电子色散的量子工程来创建人工跃迁，就像在量子级联设备中一样。在这项工作中，我们提出了一种产生中红外光的替代方法，利用由于纳米级极性介电晶体的非局部光学响应而导致的纵向和横向自由度之间的耦合。极性晶体支持中红外的亚衍射光子模式。它们还支持纵向声子，通过 Fröhlich 相互作用与电流有效耦合。正如我们在之前的理论和实验工作中所展示的那样，这两个自由度可以杂化形成纵向-横向极化激元。在这里，我们从理论上证明了纵向-横向极化激元可以通过电流有效地产生，从而导致谐振窄带光子发射。因此，这种方法可用于在没有偶极活性电子跃迁的情况下产生远场中红外光子，有可能支撑新一代中红外光电器件。