Research Article
Co-Polarization Wideband Terahertz Metamaterial Absorber with a Wavy Split Ring Resonator
Kwang-Jin Ri*
,
Un-Ha Ri,
Ju-Song Ri,
Yong-Jun Kim,
In-Ho Pak
Issue:
Volume 13, Issue 2, December 2025
Pages:
15-23
Received:
16 July 2025
Accepted:
4 August 2025
Published:
20 August 2025
Abstract: A simple design of co-polarization wideband metamaterial absorber (MA) for terahertz devices is proposed, where the wavy split ring resonator has been conceived to broaden the absorption bandwidth of MA. Simulation results ensure that the average absorptivity of proposed MA reaches above 90% ranging from 2.07 THz to 4.80 THz. The relative absorption bandwidth (RAB) of proposed MA is 79.47%. In addition, the proposed MA may also be considered as a wideband polarization converter with high efficiency. The physical mechanism of wideband absorption is analyzed by using the electric field and the surface current distributions. The co-polarization absorption characteristics of proposed MA under oblique incident angle are also investigated. For TE mode, the absorptivity of proposed MA reaches above 81% ranging from 2.07 THz to 4.80 THz for incident angles below 40°. For TM mode, the proposed MA still retains absorptivity above 87% ranging from 2.07 THz to 4.80 THz for incidence angles below 40°. Due to the compact structure and co-polarization wideband absorption with wide incident angle stability, the proposed MA may be widely utilized for medical imaging, material detecting and stealth technology. Moreover, the wavy split ring resonator can be also applied to achieve wideband absorption in various frequency regions from microwave to visible light.
Abstract: A simple design of co-polarization wideband metamaterial absorber (MA) for terahertz devices is proposed, where the wavy split ring resonator has been conceived to broaden the absorption bandwidth of MA. Simulation results ensure that the average absorptivity of proposed MA reaches above 90% ranging from 2.07 THz to 4.80 THz. The relative absorptio...
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Research Article
Versatile Protrusive VO2 Metamaterials Enabling Tunable Ultra-broadband Terahertz Absorption
Issue:
Volume 13, Issue 2, December 2025
Pages:
24-32
Received:
1 August 2025
Accepted:
15 August 2025
Published:
8 September 2025
Abstract: Until now, it has been conventional to design tunable metamaterial absorbers with single layer scheme of metal-dielectric-VO2. For further expansion of the operating bandwidth, the construction method stacking several layers of dielctric-VO2 has been utilized. However, the single layer configuration of metal-dielectric-VO2 cannot extend the absorption bandwidth to the entire THz band. Meanwhile, In the stacking method, other VO2 resonators excepting the topmost VO2 resonator are embedded in the dielectric substrate. This unavoidably leads to the delay in response time to external stimuli. So, apart from these conventional methods, we have conceived the protrusive VO2 metamaterials, which are effective for overcoming the above limitations. The protrusive VO2 metamaterials consist of a VO2 square ring, a protrusive VO2 square patch and a polyimide substrate backed with a gold bottom plane. Based on the proposed design idea, we demonstrate a tunable ultra-broadband THz metamaterial absorber (MA) with bandwidth of 9.39 THz. That is, the protrusive VO2 metamaterials greatly enlarge the operating bandwidth with perfect absorption. The proposed MA can obtain the absorptivity above 90% in range of 1.67-11.06 THz, with relative absorption bandwidth of 147.52%. Moreover, the protrusive VO2 metamaterials can realize the absorption tunability by modifying the conductivity of VO2. Additionally, we also demonstrate that the idea of protrusive VO2 metamaterials is very useful for designing several tunable ultra-broadband THz MAs. Owing to the excellent structural versatility, the protrusive VO2 metamaterials are of great value for THz applications.
Abstract: Until now, it has been conventional to design tunable metamaterial absorbers with single layer scheme of metal-dielectric-VO2. For further expansion of the operating bandwidth, the construction method stacking several layers of dielctric-VO2 has been utilized. However, the single layer configuration of metal-dielectric-VO2 cannot extend the absorpt...
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Research Article
LD-pumped Nd: YAG Electro-optic Q-switched Laser and Its KTP Extra-cavity Frequency-doubling Characteristics
Lianju Shang*,
Zhenzhong Cao
Issue:
Volume 13, Issue 2, December 2025
Pages:
33-37
Received:
1 November 2025
Accepted:
13 November 2025
Published:
8 December 2025
Abstract: An Nd: YAG electro-optic Q-switched laser side-pumped by a laser diode and its extra-cavity frequency-doubling characteristics are reported in this paper. The laser employs a KD*P crystal as the electro-optic Q-switch and uses a combination of a 1/4 wave plate and a polarizer to achieve precise Q-switch control. Under the operating conditions of the pump power of 80W, the 1064 nm laser output with a pulse width of 10ns and a single-pulse energy of 3µJ was obtained, with a peak power of 300W. By inserting a 15mm long KTP frequency-doubling crystal outside the cavity, a 532nm single-pulse green of 1.75µJ was achieved with a frequency-doubling conversion efficiency of 58.3%. This experiment achieved high peak power pulsed output from an all-solid-state electro-optic Q-switched laser, with excellent pulse stability and energy fluctuations of less than ±1%. The results demonstrate that the KD*P crystal, as an electro-optic Q-switch, enables precise Q-switching control and generates laser output with narrow pulse width. Furthermore, the frequency-doubling crystal KTP is highly suitable for frequency doubling 1064nm laser radiation, achieving high conversion efficiency at moderate power densities. This study also effectively addressed potential thermal effects during laser operation by implementing a water-cooling system and optimized heat sink design, which successfully controlled the temperature of the Nd: YAG crystal, KD*P electro-optic crystal, and KTP frequency-doubling crystal.
Abstract: An Nd: YAG electro-optic Q-switched laser side-pumped by a laser diode and its extra-cavity frequency-doubling characteristics are reported in this paper. The laser employs a KD*P crystal as the electro-optic Q-switch and uses a combination of a 1/4 wave plate and a polarizer to achieve precise Q-switch control. Under the operating conditions of th...
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