College of William and Mary, Williamsburg, Virginia 23185, USA.
Opt Lett. 2011 Aug 15;36(16):3027-9. doi: 10.1364/OL.36.003027.
In this Letter we report experimental demonstration of nonlinear frequency conversion at several optical frequencies in a whispering-gallery mode resonator (WGMR). Because of the enhancement of nonlinear interactions inside a WGMR, interaction of a 1064 nm pump field with a LiNbO(3) disk produced a weak but measurable non-phase-matched 532 nm second-harmonic field at room temperature (>100 °C below the phase-matching temperature) for pump powers of a few tens of milliwatts. For higher pump powers, we observed the generation of four additional fields at 545, 559, 573, and 587 nm. The relative spectral shift between two consecutive fields corresponds to a 455 cm(-1) vibrational mode in LiNbO(3) crystal. Our preliminary analysis indicates that these fields are the result of a multiphonon hyper-Raman scattering in which two photons of the pump field are converted into one photon of a higher-frequency field and one or several optical phonons.
在这封信件中，我们报告了在 whispering-gallery 模式谐振器（WGMR）中几个光频的非线性频率转换的实验演示。由于 WGMR 内非线性相互作用的增强，1064nm 泵浦场与 LiNbO(3) 盘的相互作用在室温下（低于相匹配温度 100°C 以上）产生了微弱但可测量的非相位匹配 532nm 二次谐波场，泵浦功率为几十毫瓦。对于更高的泵浦功率，我们观察到在 545、559、573 和 587nm 处产生了另外四个场。两个连续场之间的相对光谱位移对应于 LiNbO(3)晶体中的一个 455cm(-1)振动模式。我们的初步分析表明，这些场是多声子超拉曼散射的结果，其中泵浦场的两个光子转换为高频场的一个光子和一个或几个光学声子。
