Emission-Frequency Separated High Quality Single-Photon Sources Enabled by Phonons
Emission-Frequency Separated High Quality Single-Photon Sources Enabled by Phonons
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DOI：
10.1103/physrevlett.123.017403
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发表时间：
2019-07-03
影响因子：
8.6
通讯作者：
Axt, V. M.
中科院分区：
文献类型：
--
作者：
Cosacchi, M.;Ungar, F.;Axt, V. M.
我们从理论上证明，从声子辅助的非共振激发制备的量子点激子发射的光子的单光子纯度可以显着高于在很宽的参数范围内，在其他相同的条件下，通过共振制备。尽管非共振激发，亮度保持在高水平。这些令人惊讶的发现利用了这样的事实，即声子辅助制备是一个两步的过程，其中声子首先导致激光修饰状态之间的弛豫，而高激子占据仅通过对点状态的非修饰而延迟到激光脉冲最大值来达到。由于这种延迟，可能的后续过程，特别是多光子激发，出现在激光脉冲几乎消失的时候。由此产生的再激发过程的抑制增加了单光子纯度。由于信号光子与激光频率的光谱分离，这使得能够发射不受激光背景干扰的高质量单光子，同时利用声子辅助方案的鲁棒性。
We demonstrate theoretically that the single-photon purity of photons emitted from a quantum dot exciton prepared by phonon-assisted off-resonant excitation can be significantly higher in a wide range of parameters than that obtained by resonant preparation for otherwise identical conditions. Despite the off-resonant excitation, the brightness stays on a high level. These surprising findings exploit the fact that the phonon-assisted preparation is a two-step process where phonons first lead to a relaxation between laser-dressed states while high exciton occupations arc reached only with a delay to the laser pulse maximum by adiabatically undressing the dot states. Due to this delay, possible subsequent processes, in particular multiphoton excitations, appear at a time when the laser pulse is almost gone. The resulting suppression of reexcitation processes increases the single-photon purity. Due to the spectral separation of the signal photons from the laser frequencies this enables the emission of high quality single photons not disturbed by a laser background while taking advantage of the robustness of the phonon assisted scheme.