We demonstrate experimentally the increase of optical-to-terahertz conversion efficiency for GaAs-based photoconductive terahertz emitters. This increase is achieved by preventing device breakdown through series resistors, which act as a current limiter. Pulsed photoexcitation and potential current fluctuations result in heat dissipation leading to local heating, which further increases the current and may lead to device breakdown. We manage to increase the maximum bias field before device breakdown by a factor of 3 under illuminated conditions. For a laser system with 250-kHz repetition rate, the terahertz emission amplitude increases linearly with applied bias field up to 120 kV/cm bias field, which results in 3 times higher signal as compared to the standard device. Furthermore, we have also achieved this expanded breakdown prevention at 78-MHz repetition rate, where an integrated on-chip resistance leads to an enhancement of the terahertz field amplitude by 70%. This simple technique can increase the performance of almost all photoconductive terahertz emitters by using appropriate resistances according to the emitter capacitance and laser repetition rate.

我们通过实验证明了基于GaAs的光电导太赫兹发射器的光到太赫兹转换效率的提高。通过防止用作电流限制器的串联电阻使器件击穿，可以实现这种增加。脉冲光激发和潜在的电流波动会导致散热，导致局部发热，从而进一步增加电流并可能导致器件击穿。在光照条件下，我们设法将器件击穿前的最大偏置场增加了3倍。对于具有250 kHz重复频率的激光系统，太赫兹发射幅度随施加的偏置场（直至120 kV / cm偏置场）线性增加，与标准器件相比，其信号强度高出3倍。此外，我们还以78 MHz的重复频率实现了这种扩展的击穿预防功能，其中集成的片上电阻可将太赫兹场振幅提高70％。通过根据发射器电容和激光重复频率使用适当的电阻，这种简单的技术可以提高几乎所有光电导太赫兹发射器的性能。