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2018
Volume: 16 Issue 5
20 Article(s)
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ADVANCES IN METASURFACES
Editorial for special issue on advances in metasurfaces
Qiwen Zhan, and Qiaoqiang Gan
Metasurface refers to a type of artificial thin film materials with sub-wavelength features that can generate the desired and/or new optical phenomena. The past decade has witnessed significant advances in the metasurface, ranging from fundamental physics to nanomanufacturing methods and practical applications. Typical research efforts include wave-front engineering and detection [e.g., Yu, Science 334, 333 (2011); Capasso, Nat. Commun. 3, 1278 (2012)], flat optics for focusing and imaging [e.g., Cappaso, Nano Lett. 12, 4932 (2012); Yu, Nat. Mater. 13, 139 (2014)], polarization manipulation [e.g., Zhan, Opt. Lett. 40, 4711 (2015); Sci. Rep. 6, 29626 (2016)], metahologram [e.g., Genevet, Rep. Prog. Phys. 78, 24401 (2015); Tsai, Nano Lett. 14, 225 (2014)], light trapping and localization [e.g., Gan, Adv. Mater. 26, 2737 (2014); Adv. Opt. Mater. 5, 1700223 (2017)], absorption engineering [Gan, Adv. Opt. Mater. 5, 1700166 (2017); Sci. Adv. 3, e1602783 (2017)], and colorimetric display. Being able to manipulate the optical properties of metasurfaces will create new regimes of optical physics and impact a broad range of photonic, energy, and biomedical technologies, including new commercial product research and development. Research and development efforts of these artificial thin film materials in promising areas continue to emerge. To capture the latest developments in this important emerging field of optics, it is our pleasure to introduce the Chinese Optics Letters Special Issue on Advances in Metasurface with contributions from scientists around the world who are active in this field.
Metasurface refers to a type of artificial thin film materials with sub-wavelength features that can generate the desired and/or new optical phenomena. The past decade has witnessed significant advances in the metasurface, ranging from fundamental physics to nanomanufacturing methods and practical applications. Typical research efforts include wave-front engineering and detection [e.g., Yu, Science
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050001 (2018)
Near-field manipulation of terahertz surface waves by metasurfaces [Invited]
Quan Xu, Xueqian Zhang, Yuehong Xu, Chunmei Ouyang, Yanfeng Li, Jiaguang Han, and Weili Zhang
Surface waves (SWs) are a special form of electromagnetic waves that travel along the boundary between a metal and a dielectric. The special optical properties of SWs render them very attractive in applications, such as subdiffractional lithography, novel biochemical sensors, and ultrafast integrated circuitries. Herein, we present a review of our recent progress in excitation and manipulation of terahertz SWs due to interference or coupling between a pair of slit resonators in metasurfaces, showing the ability to devise ultrathin and compact plasmonic components.Surface waves (SWs) are a special form of electromagnetic waves that travel along the boundary between a metal and a dielectric. The special optical properties of SWs render them very attractive in applications, such as subdiffractional lithography, novel biochemical sensors, and ultrafast integrated circuitries. Herein, we present a review of our recent progress in excitation and manipulation of terahertz SWs due to interference or coupling between a pair of slit resonators in metasurfaces, showing the ability to devise ultrathin and compact plasmonic components..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050002 (2018)
High-efficiency multi-wavelength metasurface with complete independent phase control
Jing Yan, Yinghui Guo, Mingbo Pu, Xiong Li, Xiaoliang Ma, and Xiangang Luo
As a consequence of Kramers–Kronig relations, the wavelength-dependent behavior of the metasurface is one of the critical limitations in existing metasurface structures, which reduces the design freedom among different wavelengths. Here, we present an approach to construct a high-efficiency multi-wavelength metasurface with independent phase control by coding different wavelengths into orthogonal polarizations. As proof of the concept, two dual-band metasurfaces have been proposed and numerically demonstrated by multiple vortex beam generation in near-field and polarization multiplexing achromatic beam deflection. Furthermore, simulated results show that the proposed metasurface exhibits high transmission efficiency at both wavelengths, which may find widespread applications in subwavelength electromagnetics.As a consequence of Kramers–Kronig relations, the wavelength-dependent behavior of the metasurface is one of the critical limitations in existing metasurface structures, which reduces the design freedom among different wavelengths. Here, we present an approach to construct a high-efficiency multi-wavelength metasurface with independent phase control by coding different wavelengths into orthogonal polarizations. As proof of the concept, two dual-band metasurfaces have been proposed and numerically demonstrated by multiple vortex beam generation in near-field and polarization multiplexing achromatic beam deflection. Furthermore, simulated results show that the proposed metasurface exhibits high transmission efficiency at both wavelengths, which may find widespread applications in subwavelength electromagnetics..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050003 (2018)
Mid-infrared superabsorbers based on quasi-periodic moiré metasurfaces
Yaoran Liu, Zilong Wu, Eric H. Hill, and Yuebing Zheng
We report on mid-infrared superabsorbers based on quasi-periodic moiré metasurfaces in metal-insulator-metal form. By varying the spacer thickness, moiré rotation angle, and filling factor of the superabsorbers, we can tune narrowband or broadband absorption in a systematic way. With their high tunability of near-unity absorption and simple fabrication, in combination with decoupled mode theory for an efficient design, moiré superabsorbers are well-suited for a wide range of applications in sensing, imaging, and communication.We report on mid-infrared superabsorbers based on quasi-periodic moiré metasurfaces in metal-insulator-metal form. By varying the spacer thickness, moiré rotation angle, and filling factor of the superabsorbers, we can tune narrowband or broadband absorption in a systematic way. With their high tunability of near-unity absorption and simple fabrication, in combination with decoupled mode theory for an efficient design, moiré superabsorbers are well-suited for a wide range of applications in sensing, imaging, and communication..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050004 (2018)
Optical cavity resonance with magnetized plasma
Dongyang Wang, Jiaguang Han, and Shuang Zhang
Indefinite media with mixed signs of dielectric tensor elements possess unbounded equifrequency surfaces that have been utilized for diverse applications such as superimaging, enhanced spontaneous emission, and thermal radiation. One particularly interesting application of indefinite media is an optical cavity supporting anomalous scaling laws. In this Letter, we show that by replacing an indefinite medium with magnetized plasma one can construct a tunable indefinite cavity. The magnetized plasma model is based on realistic semiconductor material properties at terahertz frequencies that show hyperbolic dispersion in a certain frequency regime. The hyperbolic dispersion features are utilized for the design of optical cavities. Dramatically different sizes of cavities can support the same resonance mode at the same frequency. For a cavity of fixed size, the anomalous scaling law between the resonance frequency and mode number is confirmed. The resonance frequency can be strongly modulated by changing the strength of the applied magnetic field. The proposed model provides active controllability of terahertz resonances on the deep subwavelength scale with realistic semiconductor materials.Indefinite media with mixed signs of dielectric tensor elements possess unbounded equifrequency surfaces that have been utilized for diverse applications such as superimaging, enhanced spontaneous emission, and thermal radiation. One particularly interesting application of indefinite media is an optical cavity supporting anomalous scaling laws. In this Letter, we show that by replacing an indefinite medium with magnetized plasma one can construct a tunable indefinite cavity. The magnetized plasma model is based on realistic semiconductor material properties at terahertz frequencies that show hyperbolic dispersion in a certain frequency regime. The hyperbolic dispersion features are utilized for the design of optical cavities. Dramatically different sizes of cavities can support the same resonance mode at the same frequency. For a cavity of fixed size, the anomalous scaling law between the resonance frequency and mode number is confirmed. The resonance frequency can be strongly modulated by changing the strength of the applied magnetic field. The proposed model provides active controllability of terahertz resonances on the deep subwavelength scale with realistic semiconductor materials..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050005 (2018)
Metasurfaces enabling structured light manipulation: advances and perspectives [Invited]
Jian Wang
Metasurfaces and structured light have rapidly advanced over the past few years, from being paradigms to forming functional devices and tailoring special light beams for wide emerging applications. Here, we focus on harnessing metasurfaces for structured light manipulation. We review recent advances in shaping structured light by metasurfaces on different platforms (metal, silica, silicon, and fiber). Structured light manipulation based on plasmonic metasurfaces, reflection-enhanced plasmonic metasurfaces, metasurfaces on fiber facets, dielectric metasurfaces, and sub-wavelength structures on silicon are presented, showing impressive performance. Future trends, challenges, perspectives, and opportunities are also discussed.Metasurfaces and structured light have rapidly advanced over the past few years, from being paradigms to forming functional devices and tailoring special light beams for wide emerging applications. Here, we focus on harnessing metasurfaces for structured light manipulation. We review recent advances in shaping structured light by metasurfaces on different platforms (metal, silica, silicon, and fiber). Structured light manipulation based on plasmonic metasurfaces, reflection-enhanced plasmonic metasurfaces, metasurfaces on fiber facets, dielectric metasurfaces, and sub-wavelength structures on silicon are presented, showing impressive performance. Future trends, challenges, perspectives, and opportunities are also discussed..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050006 (2018)
Fabrication of electrically contacted plasmonic Schottky nanoantennas on silicon
Mohammad Alavirad, Anthony Olivieri, Langis Roy, and Pierre Berini
We fabricate Schottky contact photodetectors based on electrically contacted Au nanoantennas on p-Si for the plasmonic detection of sub-bandgap photons in the optical communications wavelength range. Based on a physical model for the internal photoemission of hot carriers, photons coupled onto the Au nanoantennas excite resonant plasmons, which decay into energetic “hot” holes emitted over the Schottky barrier at the Au/p-Si interface, resulting in a photocurrent. In our device, the active Schottky area consists of Au/p-Si contact and is very small, whereas the probing pad for external electrical interconnection is larger but consists of Au/Ti/p-Si contact having a comparatively higher Schottky barrier, thus producing negligible photo and dark currents. We describe fabrication that involves an electron-beam lithography step overlaid with photolithography. This highly compact component is very promising for applications in high-density Si photonics.We fabricate Schottky contact photodetectors based on electrically contacted Au nanoantennas on p-Si for the plasmonic detection of sub-bandgap photons in the optical communications wavelength range. Based on a physical model for the internal photoemission of hot carriers, photons coupled onto the Au nanoantennas excite resonant plasmons, which decay into energetic “hot” holes emitted over the Schottky barrier at the Au/p-Si interface, resulting in a photocurrent. In our device, the active Schottky area consists of Au/p-Si contact and is very small, whereas the probing pad for external electrical interconnection is larger but consists of Au/Ti/p-Si contact having a comparatively higher Schottky barrier, thus producing negligible photo and dark currents. We describe fabrication that involves an electron-beam lithography step overlaid with photolithography. This highly compact component is very promising for applications in high-density Si photonics..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050007 (2018)
Enhancing magnetic dipole emission with magnetic metamaterials
Shang Sun, Chen Zhang, Haitao Zhang, Yisheng Gao, Ningbo Yi, Qinghai Song, and Shumin Xiao
Magnetic dipole (MD) transitions are important for a range of technologies from quantum light sources and displays to lasers and bio-probes. However, the typical MD transitions are much weaker than their electric counterparts and are usually neglected in practical applications. Herein, we experimentally demonstrate that the MD transitions can be significantly enhanced by the well-developed magnetic metamaterials in the visible optical range. The magnetic metamaterials consist of silver nanostrips and a thick silver film, which are separated with an Eu3+:polymethyl methacrylate (PMMA) film. By controlling the thickness of the Eu3+:PMMA film, the magnetic resonance has been tuned to match the emission wavelength of MDs. Consequently, the intensity of MD emission has been significantly increased by around 30 times at the magnetic resonance wavelength, whereas the intensity of electric dipole emission is well-preserved. The corresponding numerical calculations reveal that the enhancement is directly generated by the magnetic resonance, which strongly increases the magnetic local density of states around the MD emitter and can efficiently radiate the MD emission into the far field. This is the first demonstration, to the best of our knowledge, that MD transitions can be improved by an additional degree of magnetic freedom, and we believe this research shall pave a new route towards bright magnetic emitters and their potential applications.Magnetic dipole (MD) transitions are important for a range of technologies from quantum light sources and displays to lasers and bio-probes. However, the typical MD transitions are much weaker than their electric counterparts and are usually neglected in practical applications. Herein, we experimentally demonstrate that the MD transitions can be significantly enhanced by the well-developed magnetic metamaterials in the visible optical range. The magnetic metamaterials consist of silver nanostrips and a thick silver film, which are separated with an Eu 3 + Eu 3 +
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050008 (2018)
Deflection angle switching with a metasurface based on phase-change nanorods [Invited]
Chulsoo Choi, Sun-Je Kim, Jeong-Geun Yun, Jangwoon Sung, Seoul-Yeol Lee, and Byoungho Lee
We propose the active metasurface using phase-change material Ge2Sb2Te5 (GST), which has two distinct phases so called amorphous and crystalline phases, for an ultrathin light path switching device. By arranging multiple anisotropic GST nanorods, the gradient metasurface, which has opposite directions of phase gradients at the two distinct phases of GST, is demonstrated theoretically and numerically. As a result, in the case of normal incidence of circularly polarized light at the wavelength of 1650 nm, the cross-polarized light deflects to 55.6° at the amorphous phase and +55.6° at the crystalline phase with the signal-to-noise ratio above 10 dB.We propose the active metasurface using phase-change material Ge 2 Sb 2 Te 5 55.6 ° + 55.6 °
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050009 (2018)
Reviews
Optoelectronics
Polarization and structure dependent optical characteristics of the three-arm nanoantenna with C 3v symmetry and broken symmetry
Mian Wang, Cheng Yin, Youqiao Ma, Jun Zhou, Hanhua Zhong, and Xianfeng Chen
The optical properties of a three-arm plasmonic nanoantenna with and without broken symmetry were analyzed in detail. For the symmetrical structure, the local electric field can be significantly enhanced and well confined within the feed gap, whilst the extinction spectrum illustrates polarization independence. With broken symmetry, multi-wavelength resonances are observed due to the single dipole resonance and dipole–dipole coupling effect, and wide tunability is also available through minor structural adjustment. Especially when illuminated by a circularly polarized light beam, the extinction and the electric field distribution can be effectively modulated by just varying the incident wavelength.The optical properties of a three-arm plasmonic nanoantenna with and without broken symmetry were analyzed in detail. For the symmetrical structure, the local electric field can be significantly enhanced and well confined within the feed gap, whilst the extinction spectrum illustrates polarization independence. With broken symmetry, multi-wavelength resonances are observed due to the single dipole resonance and dipole–dipole coupling effect, and wide tunability is also available through minor structural adjustment. Especially when illuminated by a circularly polarized light beam, the extinction and the electric field distribution can be effectively modulated by just varying the incident wavelength..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 052501 (2018)
Research Articles
Atmospheric and oceanic optics
52 m /9 Gb/s PAM4 plastic optical fiber-underwater wireless laser transmission convergence with a laser beam reducer
Chung-Yi Li, Hai-Han Lu, Xu-Hong Huang, Yun-Chieh Wang, Jen-Chieh Chang, and Pei-Hsien Chew
A 52 m/9 Gb/s four-level pulse amplitude modulation (PAM4) plastic optical fiber (POF)-underwater wireless laser transmission (UWLT) convergence with a laser beam reducer is proposed. A 52 m/9 Gb/s PAM4 POF-UWLT convergence is practically demonstrated with the application of a laser beam reducer to reduce the collimated beam diameter. A 50 m graded-index (GI)-POF is employed as an underwater extender to efficiently enhance the coverage of UWLT. The performances of PAM4 POF-UWLT convergence in view of bit error rate (BER) and eye diagrams improve with the decrease of the collimated beam diameter because of the small amount of light absorbed by clear ocean water. Competent BER and eye diagrams (three independent eye diagrams) are achieved over a 50 m GI-POF transmission with a 2 m clear ocean water link.A 52 m/9 Gb/s four-level pulse amplitude modulation (PAM4) plastic optical fiber (POF)-underwater wireless laser transmission (UWLT) convergence with a laser beam reducer is proposed. A 52 m/9 Gb/s PAM4 POF-UWLT convergence is practically demonstrated with the application of a laser beam reducer to reduce the collimated beam diameter. A 50 m graded-index (GI)-POF is employed as an underwater extender to efficiently enhance the coverage of UWLT. The performances of PAM4 POF-UWLT convergence in view of bit error rate (BER) and eye diagrams improve with the decrease of the collimated beam diameter because of the small amount of light absorbed by clear ocean water. Competent BER and eye diagrams (three independent eye diagrams) are achieved over a 50 m GI-POF transmission with a 2 m clear ocean water link..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050101 (2018)
Atomic and Molecular Physics
Widely tunable laser frequency offset locking to the atomic resonance line with frequency modulation spectroscopy
Anqi Wang, Zhixin Meng, and Yanying Feng
A simple and robust technique is reported to offset lock a single semiconductor laser to the atom resonance line with a frequency difference easily adjustable from a few tens of megahertz up to tens of gigahertz. The proposed scheme makes use of the frequency modulation spectroscopy by modulating sidebands of a fiber electro-optic modulator output. The short-term performances of a frequency offset locked semiconductor laser are experimentally demonstrated with the Allan variance of around 3.9×10 11 at a 2 s integration time. This method may have many applications, such as in Raman optics for an atom interferometer.A simple and robust technique is reported to offset lock a single semiconductor laser to the atom resonance line with a frequency difference easily adjustable from a few tens of megahertz up to tens of gigahertz. The proposed scheme makes use of the frequency modulation spectroscopy by modulating sidebands of a fiber electro-optic modulator output. The short-term performances of a frequency offset locked semiconductor laser are experimentally demonstrated with the Allan variance of around 3.9 × 10 11
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 050201 (2018)
Integrated Optics
Research on photodiode integrated with wide spectrum focusing reflector using nonperiodic subwavelength gratings
Tao Liu, Yongqing Huang, Jiarui Fei, Gang Wu, Xiaokai Ma, Xiaofeng Duan, Kai Liu, and Xiaomin Ren
The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental results show that the gratings can reflect and focus the incident light on the absorber of the photodiode, and thus can simultaneously achieve high speed and high efficiency. For the gratings’ integrated photodiodes, the responsivity is improved over a wide spectral range, and when the absorber was 600 nm and the mesa diameter was 40 μm, a responsivity of 0.46 A/W at a wavelength of 1.55 μm and a 3 dB bandwidth of 21.6 GHz under a reverse bias of 3 V were simultaneously obtained.The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental results show that the gratings can reflect and focus the incident light on the absorber of the photodiode, and thus can simultaneously achieve high speed and high efficiency. For the gratings’ integrated photodiodes, the responsivity is improved over a wide spectral range, and when the absorber was 600 nm and the mesa diameter was 40 μm, a responsivity of 0.46 A/W at a wavelength of 1.55 μm and a 3 dB bandwidth of 21.6 GHz under a reverse bias of 3 V were simultaneously obtained..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 051301 (2018)
Lasers and Laser Optics
Highly efficient CW laser operation in 4 at. % Tm3+ and 4 at. % Y3+ codoped CaF2 crystals
Xinsheng Guo, Qinghui Wu, Linyang Guo, Fengkai Ma, Fei Tang, Cheng Zhang, Jie Liu, Bingchu Mei, and Liangbi Su
Tm:CaF2 and Tm,Y:CaF2 single crystals were prepared by the temperature gradient technique. The spectral properties of Tm,Y:CaF2 single crystals were investigated and compared with those of Tm:CaF2. It was demonstrated that codoping with Y3+ ions could efficiently improve the spectroscopic properties. Tm,Y:CaF2 crystals have larger absorption cross-sections at the pumping wavelength, larger mid-infrared stimulated emission cross-sections, and much longer fluorescence lifetimes of the upper laser level (Tm3+: H43 level) than Tm:CaF2 crystals. Continuous-wave (CW) lasers around 1.97 μm were demonstrated in 4.0 at. % Tm,4.0 at. % Y:CaF2 single crystals under 792 nm laser diode (LD) pumping. The best laser performance has been demonstrated with a low threshold of 0.368 W, a high slope efficiency of 54.8%, and a maximum output power of 1.013 W.Tm : CaF 2 Tm , Y : CaF 2 Tm , Y : CaF 2 Tm : CaF 2 Y 3 + Tm , Y : CaF 2 Tm 3 + : H 4 3 Tm : CaF 2 Y : CaF 2
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 051401 (2018)
An improved strontium lattice clock with 10−16 level laser frequency stabilization
Ye Li, Yige Lin, Qiang Wang, Tao Yang, Zhen Sun, Erjun Zang, and Zhanjun Fang
A clock laser based on a 30-cm-long ultrahigh finesse optical cavity was developed to improve the frequency stability of the Sr optical lattice clock at the National Institute of Metrology. Using this clock laser to probe the spin-polarized Sr87 atoms, a Rabi transition linewidth of 1.8 Hz was obtained with 500 ms interrogation time. Two independent digital servos are used to alternatively lock the clock laser to the S01 (mF=+9/2)→P03 (mF=+9/2) transition. The Allan deviation shows that the short-term frequency stability is better than 3.2×10 16 and averages down followed by 1.8×10 15/τ.A clock laser based on a 30-cm-long ultrahigh finesse optical cavity was developed to improve the frequency stability of the Sr optical lattice clock at the National Institute of Metrology. Using this clock laser to probe the spin-polarized Sr 87 S 0 1 ( m F = + 9 / 2 ) → P 0 3 ( m F = + 9 / 2 ) 3.2 × 10 16 1 . 8 × 10 15 / τ
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 051402 (2018)
Materials
Absorption modification by laser irradiation in DKDP crystals
Xiaocong Peng, Yuanan Zhao, Yueliang Wang, Guohang Hu, Liujiang Yang, and Jianda Shao
Laser-induced modification at 355 nm of deuterated potassium dihydrogen phosphate (DKDP) crystals following exposure to nanosecond (ns) and sub-ns laser irradiation is investigated in order to probe the absorption mechanism in damage initiation. Laser damage resistance is greatly improved by sub-ns laser conditioning, whereas only a little improvement occurred after ns laser conditioning at the same laser fluence. Moreover, scattering and transmittance variations after the two types of laser conditioning indicate similar reduction of linear absorption. However, by contrast, large differences on nonlinear absorption modification are discovered using Z-scan measurement. This characteristic absorption modification by laser irradiation provides evidence that a nonlinear absorption mechanism plays a key role in damage initiation at 355 nm.Laser-induced modification at 355 nm of deuterated potassium dihydrogen phosphate (DKDP) crystals following exposure to nanosecond (ns) and sub-ns laser irradiation is investigated in order to probe the absorption mechanism in damage initiation. Laser damage resistance is greatly improved by sub-ns laser conditioning, whereas only a little improvement occurred after ns laser conditioning at the same laser fluence. Moreover, scattering and transmittance variations after the two types of laser conditioning indicate similar reduction of linear absorption. However, by contrast, large differences on nonlinear absorption modification are discovered using Z-scan measurement. This characteristic absorption modification by laser irradiation provides evidence that a nonlinear absorption mechanism plays a key role in damage initiation at 355 nm..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 051601 (2018)
Other Areas of Optics
Single fiber dual-functionality optical tweezers based on graded-index multimode fiber
Zhihai Liu, Tong Wang, Yaxun Zhang, Xiaoyun Tang, Peikun Liu, Yu Zhang, Xinghua Yang, Jianzhong Zhang, Jun Yang, and Libo Yuan
We propose and demonstrate single fiber dual-functionality optical tweezers based on a graded-index multimode fiber. By using the multi-angle fiber grinding and polishing technology, we fabricate the multimode fiber tip to be a special tapered shape, contributing to focus the outgoing beam with a large intensity gradient for the first functionality—three-dimensional contactless trapping of a microparticle. By adjusting the radial direction offset between the lead-in single mode fiber and the graded-index multimode fiber, we perform the second functionality—axial shift of the trapped microparticle with respect to the fiber tip without need of moving the fiber probe itself. It is convenient for practical applications. The theoretical and experimental results about the relationship between the radial offset and the equilibrium positions of the microparticle have the good consistency. Tailoring the trap and axial shift of the microparticle based on the graded-index multimode fiber provides convenient avenues for fiber optical tweezers applied in practical researches.We propose and demonstrate single fiber dual-functionality optical tweezers based on a graded-index multimode fiber. By using the multi-angle fiber grinding and polishing technology, we fabricate the multimode fiber tip to be a special tapered shape, contributing to focus the outgoing beam with a large intensity gradient for the first functionality—three-dimensional contactless trapping of a microparticle. By adjusting the radial direction offset between the lead-in single mode fiber and the graded-index multimode fiber, we perform the second functionality—axial shift of the trapped microparticle with respect to the fiber tip without need of moving the fiber probe itself. It is convenient for practical applications. The theoretical and experimental results about the relationship between the radial offset and the equilibrium positions of the microparticle have the good consistency. Tailoring the trap and axial shift of the microparticle based on the graded-index multimode fiber provides convenient avenues for fiber optical tweezers applied in practical researches..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 053501 (2018)
Quantum optics
Generation of intensity difference squeezed state at a wavelength of 1.34 μm
Meiru Huo, Jiliang Qin, Yingrong Sun, Zhihui Yan, and Xiaojun Jia
The intensity difference squeezed state, which means that the fluctuation of the intensity difference between signal and idler beams is less than that of the corresponding shot noise level (SNL), plays an important role in high sensitivity measurement, quantum imaging, and quantum random numbers generation. When an optical parametric oscillator consisting of a type-II phase-matching periodically poled KTiOPO4 crystal operates above the threshold, an intensity difference squeezed state at a telecommunication wavelength can be obtained. The squeezing of 7.7±0.5 dB below the SNL is achieved in an analysis frequency region of 2.4–5.0 MHz.The intensity difference squeezed state, which means that the fluctuation of the intensity difference between signal and idler beams is less than that of the corresponding shot noise level (SNL), plays an important role in high sensitivity measurement, quantum imaging, and quantum random numbers generation. When an optical parametric oscillator consisting of a type-II phase-matching periodically poled KTiOPO 4 7.7 ± 0.5 dB 2.4 – 5.0 MHz
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 052701 (2018)
Ultrafast Optics
Experimental investigation on pulse-contrast degradation caused by surface reflection in optical parametric chirped-pulse amplification
Xinliang Wang, Xiaoming Lu, Xiaoyang Guo, Rongjie Xu, and Yuxin Leng
In this Letter, we experimentally explore the pulse-contrast degradation caused by surface reflection in optical parameter chirped-pulse amplification. Different pump-to-signal conversion efficiencies and post-pulses with different intensities are obtained by changing the seed-pulse or pump-pulse energy and inserting etalons with different reflection coefficients, respectively. The contrast measurements show that the generated first pre-pulse intensity is proportional to the product of the surface reflection intensity ratio and the square of the pump-to-signal conversion efficiency.In this Letter, we experimentally explore the pulse-contrast degradation caused by surface reflection in optical parameter chirped-pulse amplification. Different pump-to-signal conversion efficiencies and post-pulses with different intensities are obtained by changing the seed-pulse or pump-pulse energy and inserting etalons with different reflection coefficients, respectively. The contrast measurements show that the generated first pre-pulse intensity is proportional to the product of the surface reflection intensity ratio and the square of the pump-to-signal conversion efficiency..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 053201 (2018)
Vision, Color, and Visual Optics
Objective visual performance evaluation with visual evoked potential measurements based on an adaptive optics system
Yanrong Yang, Junlei Zhao, Haoxin Zhao, Fei Xiao, Jiaxin Xie, Tiejun Liu, and Yun Dai
An objective visual performance evaluation with visual evoked potential (VEP) measurements was first integrated into an adaptive optics (AO) system. The optical and neural limits to vision can be bypassed through this system. Visual performance can be measured electrophysiologically with VEP, which reflects the objective function from the retina to the primary visual cortex. The VEP measurements without and with AO correction were preliminarily carried out using this system, demonstrating the great potential of this system in the objective visual performance evaluation. The new system will provide the necessary technique and equipment support for the further study of human visual function.An objective visual performance evaluation with visual evoked potential (VEP) measurements was first integrated into an adaptive optics (AO) system. The optical and neural limits to vision can be bypassed through this system. Visual performance can be measured electrophysiologically with VEP, which reflects the objective function from the retina to the primary visual cortex. The VEP measurements without and with AO correction were preliminarily carried out using this system, demonstrating the great potential of this system in the objective visual performance evaluation. The new system will provide the necessary technique and equipment support for the further study of human visual function..
Chinese Optics Letters
- Publication Date: May. 10, 2018
- Vol. 16, Issue 5, 053301 (2018)
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