In condensed matter, THz optical resonances (1–5 THz) are very sensitive to thermally activated phenomena that can either equate the populations between the levels or irremediably broaden the transition to a point where it disappears. It is therefore very difficult to exploit THz electronic transitions for thermal emission. To bypass this problem, we have used a transition in the mid-infrared (10–50 THz), ultrastrongly coupled to a resonant mode of a highly subwavelength microcavity. The coupling strength in our system reaches 90% of the energy of the matter resonance and becomes so high that the lower-polariton state lies in the THz region. This mixed light–matter resonance is therefore issued from an optical transition that is much less sensitive to thermal effects, as we have experimentally demonstrated. Our system has been optimized by tailoring the cavity thickness and engineering the matter resonance, which arises from a set of heavily doped quantum wells, in order to increase the THz emissivity. By injecting a lateral current in the quantum wells that raises the electronic temperature, we have observed THz emission up to room temperature.

中文翻译：

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中红外超强光-质子耦合，用于太赫兹热发射

在凝聚态中，太赫兹光学共振（1-5太赫兹）对热激活现象非常敏感，这些现象可以使种群在两个能级之间相等，或者不可避免地将过渡变宽到消失的程度。因此，很难利用太赫兹电子跃迁进行热发射。为了绕过这个问题，我们使用了中红外（10–50 THz）的过渡，与高亚波长微腔的共振模式超强耦合。我们系统中的耦合强度达到了物质共振能量的90％，并且变得如此之高，以至于低极化态处于THz区域。因此，正如我们实验证明的那样，这种混合的光-物质共振是由对热效应不太敏感的光学跃迁引起的。我们的系统已通过调整腔体厚度和设计物质共振（由一组重掺杂量子阱产生）进行了优化，以提高THz发射率。通过在提高电子温度的量子阱中注入横向电流，我们观察到高达室温的THz发射。