Ciattoni Alessandro, Marini Andrea, Rizza Carlo, Conti Claudio
1Consiglio Nazionale Delle Ricerche (CNR-SPIN), Via Vetoio 10, 67100 L'Aquila, Italy.
2Department of Physical and Chemical Sciences, University of L'Aquila, Via Vetoio 10, 67100 L'Aquila, Italy.
Light Sci Appl. 2018 May 18;7:5. doi: 10.1038/s41377-018-0011-3. eCollection 2018.
Optical parametric oscillators are widely used as pulsed and continuous-wave tunable sources for innumerable applications, such as quantum technologies, imaging, and biophysics. A key drawback is material dispersion, which imposes a phase-matching condition that generally entails a complex design and setup, thus hindering tunability and miniaturization. Here we show that the burden of phase-matching is surprisingly absent in parametric micro-resonators utilizing mono-layer transition-metal dichalcogenides as quadratic nonlinear materials. By the exact solution of nonlinear Maxwell equations and first-principle calculations of the semiconductor nonlinear response, we devise a novel kind of phase-matching-free miniaturized parametric oscillator operating at conventional pump intensities. We find that different two-dimensional semiconductors yield degenerate and non-degenerate emission at various spectral regions due to doubly resonant mode excitation, which can be tuned by varying the incidence angle of the external pump laser. In addition, we show that high-frequency electrical modulation can be achieved by doping via electrical gating, which can be used to efficiently shift the threshold for parametric oscillation. Our results pave the way for the realization of novel ultra-fast tunable micron-sized sources of entangled photons-a key device underpinning any quantum protocol. Highly miniaturized optical parametric oscillators may also be employed in lab-on-chip technologies for biophysics, detection of environmental pollution and security.
光学参量振荡器作为脉冲和连续波可调谐光源被广泛应用于无数领域，如量子技术、成像和生物物理学。一个关键缺点是材料色散，它施加了一个相位匹配条件，这通常需要复杂的设计和设置，从而阻碍了可调谐性和小型化。在这里，我们表明，在利用单层过渡金属二硫属化物作为二次非线性材料的参量微谐振器中，相位匹配的负担出人意料地不存在。通过非线性麦克斯韦方程的精确解和半导体非线性响应的第一性原理计算，我们设计了一种新型的无相位匹配的小型化参量振荡器，它在传统泵浦强度下工作。我们发现，由于双共振模式激发，不同的二维半导体在不同光谱区域产生简并和非简并发射，这可以通过改变外部泵浦激光的入射角来调谐。此外，我们表明，通过电门控掺杂可以实现高频电调制，这可用于有效地改变参量振荡的阈值。我们的结果为实现新型超快可调谐微米级纠缠光子源铺平了道路，这是任何量子协议的关键器件。高度小型化的光学参量振荡器也可用于生物物理学、环境污染检测和安全的芯片实验室技术。
