Center for Opto-Electronic Materials and Devices, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea. Department of Optical Engineering, Sejong University, Seoul 05006, Republic of Korea.
Nanotechnology. 2017 Nov 24;28(47):475207. doi: 10.1088/1361-6528/aa9429.
Black phosphorus (BP) has attracted increasing attention due to its unique electrical properties. In addition, the outstanding optical nonlinearity of BP has been demonstrated in various ways. Its functionality as a saturable absorber, in particular, has been validated in demonstrations of passive mode-locked lasers. However, normally, the performance of BP is degraded eventually by both thermal and chemical damage in ambient conditions. The passivation of BP is the critical issue to guarantee a stable performance of the optical devices. We quantitatively characterized the mode-locked lasers operated by BP saturable absorbers with diversified passivation materials such as polydimethylsiloxane (PDMS) or AlO, considering the atomic structure of the materials, and therefore the hydro-permeability of the passivation layers. Unlike the BP layers without passivation, we demonstrated that the AlO-passivated BP layer was protected from the surface oxidation reaction in the long-term, and the PDMS-passivated one had a short-term blocking effect. The quantitative analysis showed that the time-dependent characteristics of the pulsed laser without passivation were changed with respect to the pulse duration, spectral width, and time-bandwidth product displaying 550 fs, 2.8 nm, and 0.406, respectively. With passivation, the changes were limited to <43 fs, <0.3 nm, and <0.012, respectively.
黑磷（BP）由于其独特的电学性质而受到越来越多的关注。此外，BP 的突出的光学非线性已经以各种方式得到了证明。其作为可饱和吸收体的功能，特别是在被动锁模激光器的演示中得到了验证。然而，通常情况下，BP 在环境条件下的热和化学损伤最终会使其性能下降。BP 的钝化是保证光学器件稳定性能的关键问题。我们定量地研究了用 PDMS 或 AlO 等多种钝化材料作为可饱和吸收体的锁模激光器的性能，考虑到材料的原子结构，以及因此钝化层的水渗透性。与没有钝化的 BP 层不同，我们证明了 AlO 钝化的 BP 层在长期内免受表面氧化反应的影响，而 PDMS 钝化的 BP 层则具有短期的阻断效应。定量分析表明，没有钝化的脉冲激光的时间依赖性特征随着脉冲持续时间、光谱宽度和时间带宽乘积的变化而变化，分别为 550fs、2.8nm 和 0.406。有了钝化，变化限制在<43fs、<0.3nm 和<0.012 以内。
