Contents
2018
Volume: 6 Issue 12
13 Article(s)
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Reviews
Optical Devices
High efficiency solid–liquid hybrid-state quantum dot light-emitting diodes
Jia-Sheng Li, Yong Tang, Zong-Tao Li, Long-Shi Rao, Xin-Rui Ding, and Bin-Hai Yu
Quantum dots (QDs) can achieve high quantum yields close to unity in liquid solutions, whereas they exhibit a decreased conversion efficiency after being integrated into solid-state polymer matrices for light-emitting diode (LED) devices, which is called the host matrix effect. In this study, we propose a solid–liquid hybrid-state QD-LED to solve this issue. The ethylene-terminated polydimethylsiloxane (ethylene-PDMS) is used to establish a solid-state cross-linked network, whereas the methyl-terminated PDMS (methyl-PDMS) is used in its liquid state. From a macroscopic level, the cured solid–liquid hybrid-state PDMS (SLHP) composites reach a solid state, which is stable and flexible enough to be used in LED devices. Compared with LEDs using conventional QD/solid PDMS composites at equal color conversion efficiency ranging from 40% to 60%, the luminous flux of LEDs with QD/SLHP composites is increased by 13.0% using an optimized methyl-PDMS concentration of 85 wt. %. As a result, high efficiency QD-LEDs using QDs as the only color convertor with luminous efficacy of 89.6 lm/W (0.19 A) were achieved, which show a working stability comparable with that using conventional solid-state structures at a harsh condition. Consequently, the novel approach shows great potential for achieving high efficiency and high stability QD-LEDs, which is also compatible with current structures used in illumination and display applications.Quantum dots (QDs) can achieve high quantum yields close to unity in liquid solutions, whereas they exhibit a decreased conversion efficiency after being integrated into solid-state polymer matrices for light-emitting diode (LED) devices, which is called the host matrix effect. In this study, we propose a solid–liquid hybrid-state QD-LED to solve this issue. The ethylene-terminated polydimethylsiloxane (ethylene-PDMS) is used to establish a solid-state cross-linked network, whereas the methyl-terminated PDMS (methyl-PDMS) is used in its liquid state. From a macroscopic level, the cured solid–liquid hybrid-state PDMS (SLHP) composites reach a solid state, which is stable and flexible enough to be used in LED devices. Compared with LEDs using conventional QD/solid PDMS composites at equal color conversion efficiency ranging from 40% to 60%, the luminous flux of LEDs with QD/SLHP composites is increased by 13.0% using an optimized methyl-PDMS concentration of 85 wt. %. As a result, high efficiency QD-LEDs using QDs as the only color convertor with luminous efficacy of 89.6 lm/W (0.19 A) were achieved, which show a working stability comparable with that using conventional solid-state structures at a harsh condition. Consequently, the novel approach shows great potential for achieving high efficiency and high stability QD-LEDs, which is also compatible with current structures used in illumination and display applications..
Photonics Research
- Publication Date: Nov. 14, 2018
- Vol. 6, Issue 12, 1107 (2018)
Embedded whispering-gallery mode microsphere resonator in a tapered hollow annular core fiber
Jiawei Wang, Xiaobei Zhang, Ming Yan, Lei Yang, Fengyu Hou, Wen Sun, Xiaotong Zhang, Libo Yuan, Hai Xiao, and Tingyun Wang
We propose and demonstrate a tapered hollow annular core fiber (HACF) coupler for excitation of whispering-gallery modes (WGMs) of an embedded microsphere resonator. The coupler is simply fabricated by fusion splicing of a segment of HACF with the single-mode fiber (SMF), and then improved by tapering the splicing joint to reduce the cone-apex angle. Therefore, the coupling efficiency from the SMF to the HACF is enhanced to excite various WGMs via evanescent field coupling. Normal positive, negative symmetrical Lorentzian and asymmetric Fano line shapes can be obtained by varying the resonator size and location. Another interesting phenomenon is observed that a higher Q-factor mode in a lower Q-factor mode has a contrast as high as 58. Temperature sensing with good stability is also demonstrated. This embedded WGM microsphere resonator in the tapered HACF is expected to promote environmental adaptability in practical applications due to its simplicity and robustness.We propose and demonstrate a tapered hollow annular core fiber (HACF) coupler for excitation of whispering-gallery modes (WGMs) of an embedded microsphere resonator. The coupler is simply fabricated by fusion splicing of a segment of HACF with the single-mode fiber (SMF), and then improved by tapering the splicing joint to reduce the cone-apex angle. Therefore, the coupling efficiency from the SMF to the HACF is enhanced to excite various WGMs via evanescent field coupling. Normal positive, negative symmetrical Lorentzian and asymmetric Fano line shapes can be obtained by varying the resonator size and location. Another interesting phenomenon is observed that a higher Q Q
Photonics Research
- Publication Date: Nov. 19, 2018
- Vol. 6, Issue 12, 1124 (2018)
Resonance-assisted light–control–light characteristics of SnS2 on a microfiber knot resonator with fast response
Huihui Lu, Zhongmin Wang, Zhijin Huang, Jun Tao, Hanqing Xiong, Wentao Qiu, Heyuan Guan, Huazhuo Dong, Jiangli Dong, Wenguo Zhu, Jianhui Yu, Yongchun Zhong, Yunhan Luo, Jun Zhang, and Zhe Chen
An all-optical light–control–light functionality with the structure of a microfiber knot resonator (MKR) coated with tin disulfide (SnS2) nanosheets is experimentally demonstrated. The evanescent light in the MKR [with a resonance Q of ～59,000 and an extinction ratio (ER) of ～26 dB] is exploited to enhance light–matter interaction by coating a two-dimensional material SnS2 nanosheet onto it. Thanks to the enhanced light–matter interaction and the strong absorption property of SnS2, the transmitted optical power can be tuned quasi-linearly with an external violet pump light power, where a transmitted optical power variation rate ΔT with respect to the violet light power of ～0.22 dB/mW is obtained. In addition, the MKR structure possessing multiple resonances enables a direct experimental demonstration of the relationship between resonance properties (such as Q and ER), and the obtained ΔT variation rate with respect to the violet light power. It verifies experimentally that a higher resonance Q and a larger ER can lead to a higher ΔT variation rate. In terms of the operating speed, this device runs as fast as ～3.2 ms. This kind of all-optical light–control–light functional structure may find applications in future all-optical circuitry, handheld fiber sensors, etc.An all-optical light–control–light functionality with the structure of a microfiber knot resonator (MKR) coated with tin disulfide (
Photonics Research
- Publication Date: Nov. 19, 2018
- Vol. 6, Issue 12, 1137 (2018)
Fabrication and properties of high quality InGaN-based LEDs with highly reflective nanoporous GaN mirrors
Dezhong Cao, Xiaokun Yang, Lüyang Shen, Chongchong Zhao, Caina Luan, Jin Ma, and Hongdi Xiao
Distributed Bragg reflectors (DBRs) are essential components for the development of optoelectronic devices. In this paper, we first report the use of the nanoporous GaN (NP-GaN) DBR as a template for regrowth of InGaN-based light-emitting diodes (LEDs). The wafer-scale NP-GaN DBR, which is fabricated by electrochemical etching in a neutral solution, has a smooth surface, high reflectivity (>99.5%), and wide spectral stop band width (>70 nm). The chemical composition of the regrown LED thin film is similar to that of the reference LED, but the photoluminescence (PL) lifetime, PL intensity, and electroluminescence intensity of the LED with the DBR are enhanced several times compared to those of the reference LED. The intensity enhancement is attributed to the light reflection effect of the NP-GaN DBR and improved crystalline quality as a result of the etching scheme, whereas the enhancement of PL lifetime is attributable to the latter.Distributed Bragg reflectors (DBRs) are essential components for the development of optoelectronic devices. In this paper, we first report the use of the nanoporous GaN (NP-GaN) DBR as a template for regrowth of InGaN-based light-emitting diodes (LEDs). The wafer-scale NP-GaN DBR, which is fabricated by electrochemical etching in a neutral solution, has a smooth surface, high reflectivity (> 99.5 % > 70 nm
Photonics Research
- Publication Date: Nov. 19, 2018
- Vol. 6, Issue 12, 1144 (2018)
Graphene-loaded metal wire grating for deep and broadband THz modulation in total internal reflection geometry
Yiwen Sun, Riccardo Degl’Innocenti, David A. Ritchie, Harvey E. Beere, Long Xiao, Michael Ruggiero, J. Axel Zeitler, Rayko I. Stantchev, Danni Chen, Zhengchun Peng, Emma MacPherson, and Xudong Liu
We employed a metallic wire grating loaded with graphene and operating in total internal reflection (TIR) geometry to realize deep and broadband THz modulation. The non-resonant field enhancement effect of the evanescent wave in TIR geometry and in the subwavelength wire grating was combined to demonstrate a ～77% modulation depth (MD) in the frequency range of 0.2–1.4 THz. This MD, achieved electrically with a SiO2/Si gated graphene device, was 4.5 times higher than that of the device without a metal grating in transmission geometry. By optimizing the parameters of the metallic wire grating, the required sheet conductivity of graphene for deep modulation was lowered to 0.87 mS. This work has potential applications in THz communication and real-time THz imaging.We employed a metallic wire grating loaded with graphene and operating in total internal reflection (TIR) geometry to realize deep and broadband THz modulation. The non-resonant field enhancement effect of the evanescent wave in TIR geometry and in the subwavelength wire grating was combined to demonstrate a ～ 77 % SiO 2 / Si
Photonics Research
- Publication Date: Nov. 21, 2018
- Vol. 6, Issue 12, 1151 (2018)
Physical Optics
High efficiency generation of tunable ellipse perfect vector beams | On the Cover
Lin Li, Chenliang Chang, Caojin Yuan, Shaotong Feng, Shouping Nie, Zhi-Cheng Ren, Hui-Tian Wang, and Jianping Ding
We present a highly efficient method of generating and shaping ellipse perfect vector beams (EPVBs) with a prescribed ellipse intensity profile and continuously variant linear polarization state. The scheme is based on the coaxial superposition of two orthogonally polarized ellipse laser beams of controllable phase vortex serving as the base vector components. The phase-only computer-generated hologram is specifically designed by means of a modified iteration algorithm involving a complex amplitude constraint, which is able to generate an EPVB with high diffraction efficiency in the vector optical field generator. We experimentally demonstrate that the efficiency of generating the EPVB has a notable improvement from 1.83% in the conventional complex amplitude modulation based technique to 11.1% in our method. We also discuss and demonstrate the simultaneous shaping of multiple EPVBs with independent tunable ellipticity and polarization vortex in both transversal (2D) and axial (3D) focusing structures, proving potentials in a variety of polarization-mediated applications such as trapping and transportation of particles in more complex geometric circumstances.We present a highly efficient method of generating and shaping ellipse perfect vector beams (EPVBs) with a prescribed ellipse intensity profile and continuously variant linear polarization state. The scheme is based on the coaxial superposition of two orthogonally polarized ellipse laser beams of controllable phase vortex serving as the base vector components. The phase-only computer-generated hologram is specifically designed by means of a modified iteration algorithm involving a complex amplitude constraint, which is able to generate an EPVB with high diffraction efficiency in the vector optical field generator. We experimentally demonstrate that the efficiency of generating the EPVB has a notable improvement from 1.83% in the conventional complex amplitude modulation based technique to 11.1% in our method. We also discuss and demonstrate the simultaneous shaping of multiple EPVBs with independent tunable ellipticity and polarization vortex in both transversal (2D) and axial (3D) focusing structures, proving potentials in a variety of polarization-mediated applications such as trapping and transportation of particles in more complex geometric circumstances..
Photonics Research
- Publication Date: Nov. 19, 2018
- Vol. 6, Issue 12, 1116 (2018)
Research Articles
Nonlinear Optics
Low-power nonlinear enhanced electromagnetic transmission of a subwavelength metallic aperture
Yunsheng Guo, Saiyu Liu, Ke Bi, Ming Lei, and Ji Zhou
When a dielectric meta-atom is placed into a subwavelength metallic aperture, 20-fold enhanced electromagnetic transmission through the aperture is realized at the meta-atom’s resonant frequency. Additionally, when the incident electromagnetic power increases, thermal energy gathered by the meta-atom, which is converted from electromagnetic losses, can cause the meta-atom’s temperature to increase. Because of the high temperature coefficient of the meta-atom’s resonant frequency, this temperature increase causes a blueshift in the transmission peak. Therefore, this frequency-dependent enhanced electromagnetic transmission even produces a nonlinear effect at low incident powers. Over an incident power range from 0 to 20 dBm, measured and simulated spectra near the meta-atom’s resonant frequency show distinctly nonlinear transmission.When a dielectric meta-atom is placed into a subwavelength metallic aperture, 20-fold enhanced electromagnetic transmission through the aperture is realized at the meta-atom’s resonant frequency. Additionally, when the incident electromagnetic power increases, thermal energy gathered by the meta-atom, which is converted from electromagnetic losses, can cause the meta-atom’s temperature to increase. Because of the high temperature coefficient of the meta-atom’s resonant frequency, this temperature increase causes a blueshift in the transmission peak. Therefore, this frequency-dependent enhanced electromagnetic transmission even produces a nonlinear effect at low incident powers. Over an incident power range from 0 to 20 dBm, measured and simulated spectra near the meta-atom’s resonant frequency show distinctly nonlinear transmission..
Photonics Research
- Publication Date: Nov. 14, 2018
- Vol. 6, Issue 12, 1102 (2018)
Oxygen-containing-defect-induced synergistic nonlinear optical enhancement of graphene/CdS nanohybrids under single pulse laser irradiation
Baohua Zhu, Fangfang Wang, Guixia Wang, and Yuzong Gu
Oxygen-containing defects are very important for altering the nonlinear optical (NLO) properties of graphene. To investigate the correlation between oxygen-containing defects and the synergistic NLO response in graphene-based nanocomposites, we attached CdS nanocrystals on the surface of graphene (G) and prepared G/CdS nanohybrids (NHs) consisting of various oxygen-containing functional groups via a chemical method. The NLO absorption and refraction of G/CdS NHs under single pulse laser irradiation are enhanced by 10.8 times with the concentration decrease of surface oxygen-containing groups, which might be attributed to the local field effects and synergetic effects stemming from charge transfer between the two components. However, the optical nonlinearity is decreased with further concentration decrease, which might arise from sp2 fragment interconnection and surface defects in the NHs. The NLO absorption transformation from two-photon absorption to saturable absorption with oxygen decrease is observed, and intensity-related NLO absorption and refraction in NHs are also discussed. Meanwhile, the G/CdS NHs exhibit superior NLO properties, implying potential applications of NH material in NLO devices.Oxygen-containing defects are very important for altering the nonlinear optical (NLO) properties of graphene. To investigate the correlation between oxygen-containing defects and the synergistic NLO response in graphene-based nanocomposites, we attached CdS nanocrystals on the surface of graphene (G) and prepared G/CdS nanohybrids (NHs) consisting of various oxygen-containing functional groups via a chemical method. The NLO absorption and refraction of G/CdS NHs under single pulse laser irradiation are enhanced by 10.8 times with the concentration decrease of surface oxygen-containing groups, which might be attributed to the local field effects and synergetic effects stemming from charge transfer between the two components. However, the optical nonlinearity is decreased with further concentration decrease, which might arise from sp 2
Photonics Research
- Publication Date: Nov. 27, 2018
- Vol. 6, Issue 12, 1158 (2018)
Quantum Optics
Auxiliary-cavity-assisted vacuum Rabi splitting of a semiconductor quantum dot in a photonic crystal nanocavity
Hua-Jun Chen
The coherent light-matter interaction has drawn an enormous amount of attention for its fundamental importance in the cavity quantum-electrodynamics (C-QED) field and great potential in quantum information applications. Here, we design a hybrid C-QED system consisting of a quantum dot (QD) driven by two-tone fields implanted in a photonic crystal (PhC) cavity coupled to an auxiliary cavity with a single-mode waveguide and investigate the hybrid system operating in the weak, intermediate, and strong coupling regimes of the light-matter interaction via comparing the QD-photon interaction with the dipole decay rate and the cavity field decay rate. The results indicate that the auxiliary cavity plays a key role in the hybrid system, which affords a quantum channel to influence the absorption of the probe field. By controlling the coupling strength between the auxiliary cavity and the PhC cavity, the phenomenon of the Mollow triplet can appear in the intermediate coupling regime, and even in the weak coupling regime. We further study the strong coupling interaction manifested by vacuum Rabi splitting in the absorption with manipulating the cavity-cavity coupling under different parameter regimes. This study provides a promising platform for understanding the dynamics of QD-C-QED systems and paving the way toward on-chip QD-based nanophotonic devices.The coherent light-matter interaction has drawn an enormous amount of attention for its fundamental importance in the cavity quantum-electrodynamics (C-QED) field and great potential in quantum information applications. Here, we design a hybrid C-QED system consisting of a quantum dot (QD) driven by two-tone fields implanted in a photonic crystal (PhC) cavity coupled to an auxiliary cavity with a single-mode waveguide and investigate the hybrid system operating in the weak, intermediate, and strong coupling regimes of the light-matter interaction via comparing the QD-photon interaction with the dipole decay rate and the cavity field decay rate. The results indicate that the auxiliary cavity plays a key role in the hybrid system, which affords a quantum channel to influence the absorption of the probe field. By controlling the coupling strength between the auxiliary cavity and the PhC cavity, the phenomenon of the Mollow triplet can appear in the intermediate coupling regime, and even in the weak coupling regime. We further study the strong coupling interaction manifested by vacuum Rabi splitting in the absorption with manipulating the cavity-cavity coupling under different parameter regimes. This study provides a promising platform for understanding the dynamics of QD-C-QED systems and paving the way toward on-chip QD-based nanophotonic devices..
Photonics Research
- Publication Date: Nov. 30, 2018
- Vol. 6, Issue 12, 1171 (2018)
Ultrafast Optics
Extending optical filaments with phase-nested laser beams
Jia-Qi Lü, Ping-Ping Li, Dan Wang, Chenghou Tu, Yongnan Li, and Hui-Tian Wang
Extending the length of femtosecond laser filamentation has always been desired for practical applications. Here, we demonstrate that significant extending of a single filament in BK7 glass can be achieved by constructing phase-nested beams. The filamentation and the following energy replenishment are assembled in a single phase-nested beam. The central part of the phase-nested beam is an apertured Gaussian beam, which is focused into one focal spot to produce a short filament. In contrast, the rest of the annular part converges gradually towards the central axis to continuously replenish the energy for supporting the regeneration of filaments. The common-path generating system ensures the stability of generated filaments and easily optimizes the beam parameters to obtain the longest high-quality filament due to its flexibility. In addition, we discuss the significance of continuous replenishment for extending filaments and the potential for generating more extended filaments based on this method.Extending the length of femtosecond laser filamentation has always been desired for practical applications. Here, we demonstrate that significant extending of a single filament in BK7 glass can be achieved by constructing phase-nested beams. The filamentation and the following energy replenishment are assembled in a single phase-nested beam. The central part of the phase-nested beam is an apertured Gaussian beam, which is focused into one focal spot to produce a short filament. In contrast, the rest of the annular part converges gradually towards the central axis to continuously replenish the energy for supporting the regeneration of filaments. The common-path generating system ensures the stability of generated filaments and easily optimizes the beam parameters to obtain the longest high-quality filament due to its flexibility. In addition, we discuss the significance of continuous replenishment for extending filaments and the potential for generating more extended filaments based on this method..
Photonics Research
- Publication Date: Nov. 19, 2018
- Vol. 6, Issue 12, 1130 (2018)
Errata
Raman spectroscopy regulation in van der Waals crystals: publisher’s note
Wei Zheng, Yanming Zhu, Fadi Li, and Feng Huang
This publisher’s note corrects the order of the fourth author’s name in Photon. Res.6, 991 (2018)2327-912510.1364/PRJ.6.000991.This publisher’s note corrects the order of the fourth author’s name in Photon. Res. 6 , 991 (2018 )2327-9125 10.1364/PRJ.6.000991
Photonics Research
- Publication Date: Nov. 08, 2018
- Vol. 6, Issue 12, 1101 (2018)
Control of the phase of the magnetization precession excited by circularly polarized femtosecond-laser pulses: publisher’s note
Alexander I. Chernov, Mikhail A. Kozhaev, Anastasiia Khramova, Alexander N. Shaposhnikov, Anatoly R. Prokopov, Vladimir N. Berzhansky, Anatoly K. Zvezdin, and Vladimir I. Belotelov
This publisher’s note reports corrections to the funding acknowledgment in Photon. Res.6, 1079 (2018)PRHEIZ2327-912510.1364/PRJ.6.001079.This publisher’s note reports corrections to the funding acknowledgment in Photon. Res. 6 , 1079 (2018 )PRHEIZ 2327-9125 10.1364/PRJ.6.001079
Photonics Research
- Publication Date: Nov. 27, 2018
- Vol. 6, Issue 12, 1170 (2018)
About the Cover
Ellipse perfect vector beams in focal plane, generated by superposition of two orthogonally polarized (left and right handed circular) component ellipse perfect vortex beams with opposite phase topological charges.
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