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Contents
2017
Volume: 15 Issue 6
21 Article(s)
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Reviews
Optoelectronics
Graded index separate confinement heterostructure transistor laser: analysis of various confinement structures
Mohammad Hosseini, Hassan Kaatuzian, and Iman Taghavi
A new configuration of the confinement structure is utilized to improve optoelectronic performance, including threshold current, ac current gain, optical bandwidth, and optical output power of a single quantum well transistor laser. Considering the drift component in addition to the diffusion term in electron current density, a new continuity equation is developed to analyze the proposed structures. Physical parameters, including electron mobility, recombination lifetime, optical confinement factor, electron capture time, and photon lifetime, are calculated for new structures. Based on solving the continuity equation in separate confinement heterostructures, the threshold current reduces 67%, the optical output power increases 37%, and the 3 dB optical bandwidth increases to 21 GHz (compared to 19.5 GHz in the original structure) when the graded index layers of AlξGa1 ξAs (ξ:0.05→0 in the left side of quantum well, ξ:0→0.02 in the right side of quantum well) are used instead of uniform GaAs in the base region.A new configuration of the confinement structure is utilized to improve optoelectronic performance, including threshold current, ac current gain, optical bandwidth, and optical output power of a single quantum well transistor laser. Considering the drift component in addition to the diffusion term in electron current density, a new continuity equation is developed to analyze the proposed structures. Physical parameters, including electron mobility, recombination lifetime, optical confinement factor, electron capture time, and photon lifetime, are calculated for new structures. Based on solving the continuity equation in separate confinement heterostructures, the threshold current reduces 67%, the optical output power increases 37%, and the 3 dB optical bandwidth increases to 21 GHz (compared to 19.5 GHz in the original structure) when the graded index layers of Al ξ Ga 1 ξ As ξ : 0.05 → 0 ξ : 0 → 0.02
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 062501 (2017)
Research Articles
Fiber Optics and Optical Communications
Seven-core photonic liquid crystal fibers for simultaneous mode shaping and temperature sensing
Min Liu, Bingyue Zhao, Xu Yang, and Jingyun Hou
Through doping liquid crystals into the core region, we propose a kind of seven-core photonic crystal fiber (PCF) which can achieve mode shaping and temperature sensing simultaneously in the communication window of 1.1–1.7 μm. To the best of our knowledge, this is the first time that the function of seven-core PCFs as temperature sensors is investigated. By using the full vectorial finite element method, the characteristics of the fiber with the temperature, such as the effective mode area, the waveguide dispersion, and the confinement loss, are analyzed. This kind of PCF can be competitive in providing temperature sensing in multi-core PCF lasers.Through doping liquid crystals into the core region, we propose a kind of seven-core photonic crystal fiber (PCF) which can achieve mode shaping and temperature sensing simultaneously in the communication window of 1.1–1.7 μm. To the best of our knowledge, this is the first time that the function of seven-core PCFs as temperature sensors is investigated. By using the full vectorial finite element method, the characteristics of the fiber with the temperature, such as the effective mode area, the waveguide dispersion, and the confinement loss, are analyzed. This kind of PCF can be competitive in providing temperature sensing in multi-core PCF lasers..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 060601 (2017)
Pump induced birefringence in dual-polarization fiber grating lasers
Linghao Cheng, Yunbo Li, Yizhi Liang, Hao Liang, and Bai-Ou Guan
Birefringence is critical in dual-polarization fiber-laser-based fiber-optic sensing systems, as it directly determines the beat frequency between the two polarizations. A study of pump induced birefringence in dual-polarization fiber lasers is presented here, which shows that the pump induced birefringence is a result of the interplay among pump induced refractive index change, laser dynamics, and anisotropy inside fiber lasers. For erbium-doped fiber lasers, pumping at 1480 nm is better than pumping at 980 nm in lower pump induced birefringence. Moreover, injection at 532 nm for an adequately long enough time can permanently reduce anisotropy and, hence, reduce pump induced birefringence.Birefringence is critical in dual-polarization fiber-laser-based fiber-optic sensing systems, as it directly determines the beat frequency between the two polarizations. A study of pump induced birefringence in dual-polarization fiber lasers is presented here, which shows that the pump induced birefringence is a result of the interplay among pump induced refractive index change, laser dynamics, and anisotropy inside fiber lasers. For erbium-doped fiber lasers, pumping at 1480 nm is better than pumping at 980 nm in lower pump induced birefringence. Moreover, injection at 532 nm for an adequately long enough time can permanently reduce anisotropy and, hence, reduce pump induced birefringence..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 060602 (2017)
Experimental demonstration of 60 Gb/s optical OFDM transmissions at 1550 nm over 100 m OM1 MMF IMDD system with central launching
Jian Chen, Ling Fang, Qianwu Zhang, Junjie Zhang, Yingxiong Song, Yingchun Li, and Min Wang
Record-high 60 Gb/s optical orthogonal frequency division multiplexing (OFDM) transmissions over intensity modulation and direct-detection (IMDD)-based 100 m optical mode (OM1) multi-mode fiber (MMF) links are experimentally demonstrated, utilizing 10 GHz electro-absorption modulated laser intensity modulators at a single 1550 nm wavelength. Adaptive bit loading and a simple central launching scheme of the proposed scheme show an effective way for combating the channel fading and simplifying the system structure. It shows good potential in short reach data center interconnections.Record-high 60 Gb/s optical orthogonal frequency division multiplexing (OFDM) transmissions over intensity modulation and direct-detection (IMDD)-based 100 m optical mode (OM1) multi-mode fiber (MMF) links are experimentally demonstrated, utilizing 10 GHz electro-absorption modulated laser intensity modulators at a single 1550 nm wavelength. Adaptive bit loading and a simple central launching scheme of the proposed scheme show an effective way for combating the channel fading and simplifying the system structure. It shows good potential in short reach data center interconnections..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 060603 (2017)
Optical phase remodulation for Rayleigh noise mitigation in 10 Gb/s/channel WDM passive optical networks
Jing Xu, Yang Qiu, and Ning Deng
We investigate the principles of optical phase remodulation and demonstrate its application in a future-proof 10 Gb/s/channel wavelength-division-multiplexed (WDM) passive optical network to realize a colorless optical network unit and bidirectional transmission over a single fiber. The modulation depth of downstream differential phase-shift keying is properly reduced to facilitate phase remodulation and Rayleigh noise mitigation. For both downstream and upstream 10 Gb/s signals, error-free transmission via a 20 km single-mode fiber is demonstrated without dispersion compensation operation.We investigate the principles of optical phase remodulation and demonstrate its application in a future-proof 10 Gb/s/channel wavelength-division-multiplexed (WDM) passive optical network to realize a colorless optical network unit and bidirectional transmission over a single fiber. The modulation depth of downstream differential phase-shift keying is properly reduced to facilitate phase remodulation and Rayleigh noise mitigation. For both downstream and upstream 10 Gb/s signals, error-free transmission via a 20 km single-mode fiber is demonstrated without dispersion compensation operation..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 060604 (2017)
Study on a v-band signals and pulses generator with a tunable optical carrier to sideband ratio
Hongyao Chen, Tigang Ning, Jing Li, Li Pei, Jin Yuan, and Xiaodong Wen
This Letter demonstrates a filterless v-band signals and pulses generator scheme with a tunable optical carrier to sideband ratio (OCSR). Through complete theoretical analysis, the mathematical expression of the OCSR that contains the extinction ratio, phase modulation index, and bias angle is obtained. It is found that the OCSR has a wide tuning range, from 50 to 70 dB. By careful adjustment, a 60 GHz millimeter-wave signal with the OCSR at 50.72 dB and the electrical spurious suppression ratio at 36.6 dB can be achieved. Moreover, the discussions of using optimum OCSR to generate a Nyquist pulse or triangular-shaped pulse are also presented in this Letter.This Letter demonstrates a filterless v-band signals and pulses generator scheme with a tunable optical carrier to sideband ratio (OCSR). Through complete theoretical analysis, the mathematical expression of the OCSR that contains the extinction ratio, phase modulation index, and bias angle is obtained. It is found that the OCSR has a wide tuning range, from 50 to 70 dB
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 060605 (2017)
Holography
Gradation representation method using a binary-weighted computer-generated hologram based on pulse-width modulation | On the Cover
Masato Fujiwara, Naoki Takada, Hiromitsu Araki, Chun Wei Ooi, Shohei Ikawa, Yuki Maeda, Hiroaki Niwase, Takashi Kakue, Tomoyoshi Shimobaba, and Tomoyoshi Ito
We propose a simple gradation representation method using a binary-weighted computer-generated hologram (CGH) to be displayed on a high-speed spatial light modulator that can be controlled by the pulse-width modulation technique. The proposed method uses multiple bit planes comprising binary-weighted CGHs with various pulse widths. The object points of a three-dimensional (3D) object are assigned to multiple bit planes according to their gray levels. The bit planes are sequentially displayed in a time-division-multiplexed manner. Consequently, the proposed method realizes a gradation representation of a reconstructed 3D object.We propose a simple gradation representation method using a binary-weighted computer-generated hologram (CGH) to be displayed on a high-speed spatial light modulator that can be controlled by the pulse-width modulation technique. The proposed method uses multiple bit planes comprising binary-weighted CGHs with various pulse widths. The object points of a three-dimensional (3D) object are assigned to multiple bit planes according to their gray levels. The bit planes are sequentially displayed in a time-division-multiplexed manner. Consequently, the proposed method realizes a gradation representation of a reconstructed 3D object..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 060901 (2017)
Lasers and Laser Optics
Parasitic lasing in large aperture Ti:sapphire chirped pulse amplifier | Editors' Pick
Zutao Fan, Zebiao Gan, Xiaoyan Liang, Lianghong Yu, Wenqi Li, Zhen Guo, Xiaolong Yuan, He Cao, Pei Huang, Ruxin Li, and Zhizhan Xu
We research some properties of parasitic lasing (PL) in the Ti:sapphire chirped pulse amplifier with the crystal diameter of 100 mm. The evolutionary process from the spontaneous emission to the PL and its influence on amplified output energy, spectrum, and beam profile are experimentally measured. The threshold of PL in the crystal is 22 J, and the output signal can still keep rising with the pump when the pump energy is below 38 J. The PL has no obvious impact on the output spectrum and beam profile besides the energy.We research some properties of parasitic lasing (PL) in the Ti:sapphire chirped pulse amplifier with the crystal diameter of 100 mm. The evolutionary process from the spontaneous emission to the PL and its influence on amplified output energy, spectrum, and beam profile are experimentally measured. The threshold of PL in the crystal is 22 J, and the output signal can still keep rising with the pump when the pump energy is below 38 J. The PL has no obvious impact on the output spectrum and beam profile besides the energy..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 061401 (2017)
Simple and high efficient graded-index multimode fiber tweezers: simulation and experiment
Yaxun Zhang, Tong Wang, Zhihai Liu, Yu Zhang, Xiaoyun Tang, Enming Zhao, Xinghua Yang, Haili Jiang, Jianzhong Zhang, Jun Yang, and Libo Yuan
We propose and demonstrate a novel single fiber optical tweezer based on a graded-index multimode fiber (GIMMF), which works with a free length GIMMF (>30 cm). We achieve a three-dimensional stable trap of yeast cells by using the GIMMF optical tweezers. Compared with the single-mode fiber optical tweezers, the GIMMF optical tweezers possess large optical trapping forces. Owing to the freedom of the GIMMF length, the fabrication of the GIMMF optical tweezers is simple, repeatable, and highly efficient. The GIMMF tweezers have the penitential to become a new member of the single fiber optical tweezers family and have a wide range of applications in the medical and biological cytology fields.We propose and demonstrate a novel single fiber optical tweezer based on a graded-index multimode fiber (GIMMF), which works with a free length GIMMF (> 30 cm
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 061402 (2017)
Materials
Real-time observation of liquid crystal molecular directions based on a snapshot polarimeter
Jing Ma, Canhua Xu, and Yangguang Yao
The polarization state of transmitted light is linked to liquid crystal (LC) molecular distribution. The dynamic behavior of a twisted nematic LC molecule is measured with a home-built 10 kHz snapshot polarimeter. Only the transient molecule rotations are observed when the external voltage changes, and the molecules return to their original orientations quickly even when high voltage is applied. Our observations cannot be attributed to the traditional electro-optic effect. The invalidation of the static external field indicates the shielding effect of redistributing impurity ions in an LC cell.The polarization state of transmitted light is linked to liquid crystal (LC) molecular distribution. The dynamic behavior of a twisted nematic LC molecule is measured with a home-built 10 kHz snapshot polarimeter. Only the transient molecule rotations are observed when the external voltage changes, and the molecules return to their original orientations quickly even when high voltage is applied. Our observations cannot be attributed to the traditional electro-optic effect. The invalidation of the static external field indicates the shielding effect of redistributing impurity ions in an LC cell..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 061601 (2017)
Nonlinear Optics
Resonant and nonresonant second-harmonic generation in a single cadmium sulfide nanowire | Editors' Pick
Xiaoyang Huang, Shuwei Dai, Pengfei Xu, Yongmei Wang, Qing Yang, Yong Zhang, and Min Xiao
We experimentally investigate the resonant and nonresonant second-harmonic generation in a single cadmium sulfide (CdS) nanowire. The second-order susceptibility tensor is determined by analyzing the forward second-harmonic signals of the CdS nanowire. Our results show that (1) d33/d31= 2.5 at a nonresonant input wavelength of 1050 nm; (2) d33/d31= 1.9 at a resonant wavelength of 740 nm. The difference can be attributed to the polarization-dependent resonance.We experimentally investigate the resonant and nonresonant second-harmonic generation in a single cadmium sulfide (CdS) nanowire. The second-order susceptibility tensor is determined by analyzing the forward second-harmonic signals of the CdS nanowire. Our results show that (1) d 33 / d 31 = 2.5 d 33 / d 31 = 1.9
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 061901 (2017)
Harmonic generation at air–soil interface by femtosecond laser filament
Na Chen, Yaoxiang Liu, Tiejun Wang, Zhongbin Zhu, Haiyi Sun, Xiaona Yan, Yunhua Xia, Jinhua Xia, Juan Du, Jiansheng Liu, and Yuxin Leng
We observe the third-harmonic generation and second-harmonic generation together with element fluorescence from the interaction of a femtosecond laser filament with a rough surface sample (sandy soil) in non-phase-matched directions. The harmonics prove to originate from the phase-matched surface harmonics and air filament, then scatter in non-phase-matched directions due to the rough surface. These harmonics occurr when the sample is in the region before and after the laser filament, where the laser intensity is not high enough to excite the element fluorescence. The observed harmonics are related to the element spectroscopy, which will benefit the understanding of the interaction of the laser filament with a solid and be helpful for the application on filament induced breakdown spectroscopy.We observe the third-harmonic generation and second-harmonic generation together with element fluorescence from the interaction of a femtosecond laser filament with a rough surface sample (sandy soil) in non-phase-matched directions. The harmonics prove to originate from the phase-matched surface harmonics and air filament, then scatter in non-phase-matched directions due to the rough surface. These harmonics occurr when the sample is in the region before and after the laser filament, where the laser intensity is not high enough to excite the element fluorescence. The observed harmonics are related to the element spectroscopy, which will benefit the understanding of the interaction of the laser filament with a solid and be helpful for the application on filament induced breakdown spectroscopy..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 061902 (2017)
Optical Design and Fabrication
Versatile nanosphere lithography technique combining multiple-exposure nanosphere lens lithography and nanosphere template lithography
Yonghui Zhang, Zihui Zhang, Chong Geng, Shu Xu, Tongbo Wei, and Wen'gang Bi
A versatile nanosphere composite lithography (NSCL) combining both the advantages of multiple-exposure nanosphere lens lithography (MENSLL) and nanosphere template lithography (NSTL) is demonstrated. By well controlling the development, washing and the drying processes, the nanosphere monolayer can be well retained on the substrate after developing and washing. Thus the NSTL can be performed based on MENSLL to fabricate nanoring, nanocrescent and hierarchical multiple structures. The pattern size and the shape can be systemically tuned by shrinking nanospheres by using dry etching and adjusting the tilted angle. It is a natural nanopattern alignment process and possesses a great potential in the scope of nano-science due to its low cost, simplicity, and versatility for variuos nano-fabrications.A versatile nanosphere composite lithography (NSCL) combining both the advantages of multiple-exposure nanosphere lens lithography (MENSLL) and nanosphere template lithography (NSTL) is demonstrated. By well controlling the development, washing and the drying processes, the nanosphere monolayer can be well retained on the substrate after developing and washing. Thus the NSTL can be performed based on MENSLL to fabricate nanoring, nanocrescent and hierarchical multiple structures. The pattern size and the shape can be systemically tuned by shrinking nanospheres by using dry etching and adjusting the tilted angle. It is a natural nanopattern alignment process and possesses a great potential in the scope of nano-science due to its low cost, simplicity, and versatility for variuos nano-fabrications..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 062201 (2017)
Design of image-side telecentric freeform imaging systems based on a point-by-point construction-iteration process
Tong Yang, Guofan Jin, and Jun Zhu
In this Letter, we present a novel design method of image-side telecentric freeform imaging systems. The freeform surfaces in the system can be generated using a point-by-point design approach starting from an initial system consisting of simple planes. The proposed method considers both the desired object–image relationships and the telecentricity at the image-side during the design process. The system generated by this method can be taken as a good starting point for further optimization. To demonstrate the benefit and feasibility of our method, we design two freeform off-axis three-mirror image-side telecentric imaging systems in the visible band. The systems operate at F/1.9 with a 30 mm entrance pupil diameter and 5° diagonal field-of-view. The modulation-transfer-function curves are above 0.69 at 100 lps/mm.In this Letter, we present a novel design method of image-side telecentric freeform imaging systems. The freeform surfaces in the system can be generated using a point-by-point design approach starting from an initial system consisting of simple planes. The proposed method considers both the desired object–image relationships and the telecentricity at the image-side during the design process. The system generated by this method can be taken as a good starting point for further optimization. To demonstrate the benefit and feasibility of our method, we design two freeform off-axis three-mirror image-side telecentric imaging systems in the visible band. The systems operate at F/1.9 with a 30 mm entrance pupil diameter and 5° diagonal field-of-view. The modulation-transfer-function curves are above 0.69 at 100 lps/mm..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 062202 (2017)
Optical devices
Experimental evidence of photonic crystal waveguides with wide bandwidth in two-dimensional Al2O3 rods array
Yong Wang, Dengguo Zhang, Shixiang Xu, Biaogang Xu, Zheng Dong, and Tan Huang
A cross-shaped photonic crystal waveguide formed by a square lattice Al2O3 rods array is numerically and experimentally investigated. The band gap of the TE mode for the photonic crystals and transmission characteristics of waveguides are calculated by the plane wave expansion method and the finite element method. We perform the experiments in the microwave regime to validate the numerical results. The measured reflection and transmission characteristics of the photonic crystals show a large band gap between 8.62 and 11.554 GHz (relative bandwidth is 29.34%). The electromagnetic waves are transmitted stably in the waveguides, and the transmission characteristics maintain a high level in the band gap.A cross-shaped photonic crystal waveguide formed by a square lattice Al 2 O 3
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 062301 (2017)
Optics at Surfaces
Optical rectification and Pockels effect as a method to detect the properties of Si surfaces
Qi Wang, Li Zhang, Xin Wang, Haiyan Quan, Zhanguo Chen, Jihong Zhao, Xiuhuan Liu, Lixin Hou, Yanjun Gao, Gang Jia, and Shaowu Chen
The depth profile of electric-field-induced (EFI) optical rectification (OR) and EFI Pockels effect (PE) in a Si(110) crystal are investigated. The results show that EFI OR and PE signals are very sensitive to the electric field strength in the surface layers of the Si crystal. Theoretical formulas that include the electric field parameters and the widths of the space-charge region are presented and agreed very well with the experimental results. The experiments and simulations indicate that EFI OR and PE are potential methods for researching the surface/interface properties along the depth direction in centrosymmetric crystals such as Si.The depth profile of electric-field-induced (EFI) optical rectification (OR) and EFI Pockels effect (PE) in a Si(110) crystal are investigated. The results show that EFI OR and PE signals are very sensitive to the electric field strength in the surface layers of the Si crystal. Theoretical formulas that include the electric field parameters and the widths of the space-charge region are presented and agreed very well with the experimental results. The experiments and simulations indicate that EFI OR and PE are potential methods for researching the surface/interface properties along the depth direction in centrosymmetric crystals such as Si..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 062401 (2017)
Other Areas of Optics
Luminescent solar concentrators with a bottom-mounted photovoltaic cell: performance optimization and power gain analysis
Ningning Zhang, Yi Zhang, Jun Bao, Feng Zhang, Sen Yan, Song Sun, and Chen Gao
Polymethyl methacrylate (PMMA) plate luminescent solar concentrators with a bottom-mounted (BM-LSCs) photovoltaic (PV) cell are fabricated by using a mixture of Lumogen Red 305 and Yellow 083 fluorescent dyes and a commercial monocrystalline silicon cell. The fabricated LSC with dye concentrations of 40 ppm has the highest power gain of 1.50, which is the highest value reported for the dye-doped PMMA plate LSCs. The power gain of the LSC comes from three parts: the waveguide light, the transmitted light, and the reflected light from a white reflector, and their contributions are analyzed quantitatively. The results suggest that the BM-LSCs have great potential for future low-cost PV devices in building integrated PV applications.Polymethyl methacrylate (PMMA) plate luminescent solar concentrators with a bottom-mounted (BM-LSCs) photovoltaic (PV) cell are fabricated by using a mixture of Lumogen Red 305 and Yellow 083 fluorescent dyes and a commercial monocrystalline silicon cell. The fabricated LSC with dye concentrations of 40 ppm has the highest power gain of 1.50, which is the highest value reported for the dye-doped PMMA plate LSCs. The power gain of the LSC comes from three parts: the waveguide light, the transmitted light, and the reflected light from a white reflector, and their contributions are analyzed quantitatively. The results suggest that the BM-LSCs have great potential for future low-cost PV devices in building integrated PV applications..
Chinese Optics Letters
- Publication Date: Jun. 10, 2017
- Vol. 15, Issue 6, 063501 (2017)
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