In this paper, we present the design, simulation, and experimental verification of a dual-band free-standing metamaterial filter operating in a frequency range of 1 THz–30 THz. The proposed structure consists of peri...In this paper, we present the design, simulation, and experimental verification of a dual-band free-standing metamaterial filter operating in a frequency range of 1 THz–30 THz. The proposed structure consists of periodically arranged composite air holes, and exhibits two broad and flat transmission bands. To clarify the effects of the structural parameters on both resonant transmission bands, three sets of experiments are performed. The first resonant transmission band shows a shift towards higher frequency when the side width w;of the main air hole is increased. In contrast, the second resonant transmission band displays a shift towards lower frequency when the side width w;of the sub-holes is increased, while the first resonant transmission band is unchanged. The measured results indicate that these resonant bands can be modulated individually by simply optimizing the relevant structural parameters（w;or w;） for the required band. In addition, these resonant bands merge into a single resonant band with a bandwidth of 7.7 THz when w;and w;are optimized simultaneously. The structure proposed in this paper adopts different resonant mechanisms for transmission at different frequencies and thus offers a method to achieve a dual-band and low-loss filter.展开更多
Decoherence of fiber laser sources is of great importance in imaging applications,and most current studies use ordinary multi-mode fibers(MMFs).Here,a newly designed single-trench fiber(STF)is investigated to reduce t...Decoherence of fiber laser sources is of great importance in imaging applications,and most current studies use ordinary multi-mode fibers(MMFs).Here,a newly designed single-trench fiber(STF)is investigated to reduce the spatial coherence of fiber light source and compared with MMFs.By bending two fibers with different turns,speckle contrast of a 0.8-m-long STF can be reduced from 0.13 to 0.08,while a 0.8-m-long MMF shows an inverse result.Through speckle contrast and decoupling-mode analysis,the reason of this inverse trend is revealed.Firstly,the STF supports more modes than the MMF due to its larger core diameter.Secondly,mode leak from the first core of the STF can couple to the second core when bending the STF.Thus,power distribution among high and low-order modes become more even,reducing the spatial coherence considerably.However,in the MMF,high-order modes become leaky modes and decrease slightly when bending the fiber.This work provides a new method to modulate coherence of light source and a new angle to study decoherence principle using special fibers.展开更多
基金supported by the Doctorate Scientific Research Foundation of Hezhou University,China(Grant No.HZUBS201503)the Promotion of the Basic Ability of Young and Middle-aged Teachers in Universities Project of Guangxi Zhuang Autonomous Region,China(Grant No.KY2016YB453)+1 种基金the Guangxi Colleges and Universities Key Laboratory Symbolic Computation,ChinaEngineering Data Processing and Mathematical Support Autonomous Discipline Project of Hezhou University,China(Grant No.2016HZXYSX01)
文摘In this paper, we present the design, simulation, and experimental verification of a dual-band free-standing metamaterial filter operating in a frequency range of 1 THz–30 THz. The proposed structure consists of periodically arranged composite air holes, and exhibits two broad and flat transmission bands. To clarify the effects of the structural parameters on both resonant transmission bands, three sets of experiments are performed. The first resonant transmission band shows a shift towards higher frequency when the side width w;of the main air hole is increased. In contrast, the second resonant transmission band displays a shift towards lower frequency when the side width w;of the sub-holes is increased, while the first resonant transmission band is unchanged. The measured results indicate that these resonant bands can be modulated individually by simply optimizing the relevant structural parameters（w;or w;） for the required band. In addition, these resonant bands merge into a single resonant band with a bandwidth of 7.7 THz when w;and w;are optimized simultaneously. The structure proposed in this paper adopts different resonant mechanisms for transmission at different frequencies and thus offers a method to achieve a dual-band and low-loss filter.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974071 and 61635005)in part by Sichuan Science and Technology Program,China(Grant No.2018HH0148)。
文摘Decoherence of fiber laser sources is of great importance in imaging applications,and most current studies use ordinary multi-mode fibers(MMFs).Here,a newly designed single-trench fiber(STF)is investigated to reduce the spatial coherence of fiber light source and compared with MMFs.By bending two fibers with different turns,speckle contrast of a 0.8-m-long STF can be reduced from 0.13 to 0.08,while a 0.8-m-long MMF shows an inverse result.Through speckle contrast and decoupling-mode analysis,the reason of this inverse trend is revealed.Firstly,the STF supports more modes than the MMF due to its larger core diameter.Secondly,mode leak from the first core of the STF can couple to the second core when bending the STF.Thus,power distribution among high and low-order modes become more even,reducing the spatial coherence considerably.However,in the MMF,high-order modes become leaky modes and decrease slightly when bending the fiber.This work provides a new method to modulate coherence of light source and a new angle to study decoherence principle using special fibers.
