基于回音壁模式微球腔的PDH稳频技术

光学微球腔因其回音壁模式可获得极高的品质因数而受到广泛关注.本文分析了Fabry-Perot腔和微球腔的基本原理,通过CO2激光熔融光纤实验制得了直径为1.2 mm的微球腔,并测试了微球腔和锥形光纤耦合结构的耦合特性.采用典型的PDH稳频系统设计了基于微球腔的稳频系统,分析了用于鉴频的误差曲线的吸收特性和色散特性,对比了不同调制频率、微球腔直径、耦合损耗、传输损耗下与误差曲线斜率的关系.结果表明:耦合状态下最大Q值可达到1.1×108,调节微球腔内横磁模和横电模的转换可优化耦合效率,匹配微球腔和锥形光纤的尺寸得到了径向二阶模式的透射谱,误差曲线效率达到15.4A mW/MHz.球腔在提高PDH稳频技术灵敏度上具有巨大潜力.

Analysis of the Pound-Drever-Hall Frequency Stabilization Technique Based on a Whispering Gallery Mode Optical Microsphere Cavity

Optical microsphere (OM) cavities supporting Whispering Gallery Modes (WGMs) have received much attention because of their high quality factor (Q).The study analyzes the Fabry-Perot (FP) cavity and OM cavity theories.An OM cavity with diameter of 1.2 mm was produced by melting a silica optical fiber using a CO2 laser,and the coupling structure for OM cavity and tapered fiber was tested.We designed an OM cavity frequency stabilization system based on basic PDH frequency stabilization system.Absorption and dispersion characteristics of error signal curves used to be frequency discrimination curves were analyzed.We compared the relationships between error signal slopes and different modulation frequency,OM cavity's diameter,coupling loss,transmission loss.The results show that the maximum Q factor of OM cavity coupled by the tapered fiber is 1.1 × 108.Transverse electric (TE) mode and transverse magnetic (TM) mode can be transformed to optimize coupling efficiency.The transmission spectrum of the second radial mode was obtained by matching dimensions between OM cavity and tapered fiber.The slope of the error signal is 15.4 A mW/MHz.Our work shows its potential to improve the sensitivity of the PDH technique.