Influence of cavity wall elasticity on resonant frequency of small underwater cylindrical Helmholtz resonator is studied theoretically and experimental. Based on the theory of electroacoustic analogy, the simplified low frequency lumpedparameter model of the Helmholtz resonator is constructed. A general, convenient for calculation expression of the resonant frequency is given by circuit analysis. The influence of the thickness and the material of the resonator on the resonant frequency is investigated by numerical method. And the approximate rigid conditions for small underwater cylindrical Helmholtz resonators of different sizes are given. Small cylindrical Helmholtz resonators of different wall thickness and material were tested in a standingwave tube filled with water. Experimental results well testified the theoreticl results and the approximate rigid condition. This paper is useful for the design and application of the underwater cylindrical Helmholtz resonators.
It is preferred to insert a saturable absorber grating in Er-doped fiber ring lasers for obtaining a stable single-longitudinal-mode laser operation; however, mode hopping is hardly avoided in various applications. A new mode hopping mechanism is found by utilizing the interferometric phase-demodulation method to transfer the optical frequency hops to the phase changes in real time. The regular mode hops triggered by fast cavity-length modulation are measured, and the characteristics and the origin of the mode hopping are obtained. Experimental results show that this kind of mode hopping, usually occurring between two neighboring longitudinal modes, may appear near the maximum slope of the modulation curve, and the laser frequency with shift about the space of the longitudinal modes before mode hopping. In addition, both the threshold frequency of the optical frequency modulation and the minimal frequency shift, which can triggered a mode hop, increase with the pump power at the same modulation amplitude. These experimental results can provide the stable operation condition if vibration or modulation exists, and they are helpful for optimal designing of the isolated assemblage or determining the operation range under the modulation condition.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.