Frontiers of Optoelectronics

Most cited articles
Baidu Crossref WebOfScience Sciencedirect
Published within: In last 1 yearsIn last 2 yearsIn last 3 yearsAll

Condition: Crossref + All
Please wait a minute...
For Selected: View Abstracts Toggle Thumbnails
Characterization of basic physical properties of Sb2Se3 and its relevance for photovoltaics
Chao CHEN,David C. BOBELA,Ye YANG,Shuaicheng LU,Kai ZENG,Cong GE,Bo YANG,Liang GAO,Yang ZHAO,Matthew C. BEARD,Jiang TANG
Front. Optoelectron..  2017, 10 (1): 18-30.
Abstract   HTML   PDF (480KB)

Antimony selenide (Sb2Se3) is a promising absorber material for thin film photovoltaics because of its attractive material, optical and electrical properties. In recent years, the power conversion efficiency (PCE) of Sb2Se3 thin film solar cells has gradually enhanced to 5.6%. In this article, we systematically studied the basic physical properties of Sb2Se3 such as dielectric constant, anisotropic mobility, carrier lifetime, diffusion length, defect depth, defect density and optical band tail states. We believe such a comprehensive characterization of the basic physical properties of Sb2Se3 lays a solid foundation for further optimization of solar device performance.

Table and Figures | Reference | Supplementary Material | Related Articles | Metrics
Cited: Crossref(112)
Status and prospects for phosphor-based white LED packaging
Zongyuan LIU, Sheng LIU, Kai WANG, Xiaobing LUO
Front Optoelec Chin.  2009, 2 (2): 119-140.
Abstract   HTML   PDF (740KB)

The status and prospects for high-power, phosphor-based white light-emitting diode (LED) packaging have been presented. A system view for packaging design is proposed to address packaging issues. Four aspects of packaging are reviewed: optical control, thermal management, reliability and cost. Phosphor materials play the most important role in light extraction and color control. The conformal coating method improves the spatial color distribution (SCD) of LEDs. High refractive index (RI) encapsulants with high transmittance and modified surface morphology can enhance light extraction. Multi-phosphor-based packaging can realize the control of correlated color temperature (CCT) with high color rendering index (CRI). Effective thermal management can dissipate heat rapidly and reduce thermal stress caused by the mismatch of the coefficient of thermal expansion (CTE). Chip-on-board (CoB) technology with a multi-layer ceramic substrate is the most promising method for high-power LED packaging. Low junction temperature will improve the reliability and provide longer life. Advanced processes, precise fabrication and careful operation are essential for high reliability LEDs. Cost is one of the biggest obstacles for the penetration of white LEDs into the market for general illumination products. Mass production in terms of CoB, system in packaging (SiP), 3D packaging and wafer level packaging (WLP) can reduce the cost significantly, especially when chip cost is lowered by using a large wafer size.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(76)
Brillouin distributed time-domain sensing in optical fibers: state of the art and perspectives
Front. Optoelectron..  2010, 3 (1): 13-21.
Abstract   PDF (387KB)
Optical fiber sensors based on stimulated Brillouin scattering have now clearly demonstrated their excellent capability for long-range distributed strain and temperature measurements. The fiber is used as sensing element, and a value for temperature and/or strain can be obtained from any point along the fiber. After explaining the principle and presenting the standard implementation, the latest developments in this class of sensors will be introduced, such as the possibility to measure with a spatial resolution of 10 cm and below while preserving the full accuracy on the determination of temperature and strain.
Reference | Related Articles | Metrics
Cited: Crossref(74)
Hydrazine processed Cu2SnS3 thin film and their application for photovoltaic devices
Jun HAN, Ying ZHOU, Yang Tian, Ziheng HUANG, Xiaohua WANG, Jie ZHONG, Zhe XIA, Bo YANG, Haisheng SONG, Jiang TANG
Front Optoelec.  2014, 7 (1): 37-45.
Abstract   HTML   PDF (633KB)

Copper tin sulfide (Cu2SnS3) was a potential earth abundant absorber material for photovoltaic device application. In this contribution, triclinic Cu2SnS3 film with phase pure composition and large grain size was fabricated from a hydrazine solution process using Cu, Sn and S as the precursors. Absorption measurement revealed this Cu2SnS3 film had a direct optical band gap of 0.88 eV, and Hall effect measurement indicated the film was p-type with hole mobility of 0.86 cm2/Vs. Finally Mo/Cu2SnS3/CdS/ZnO/AZO/Au was produced and the best device efficiency achieved was 0.78%. Also, this device showed improved device performance during ambient storage. This study laid some foundation for the further improvement of Cu2SnS3 solar cell.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(42)
Review of fiber Bragg grating sensor technology
Jinjie CHEN, Bo LIU, Hao ZHANG
Front Optoelec Chin.  2011, 4 (2): 204-212.
Abstract   HTML   PDF (455KB)

The current status of the fiber Bragg grating (FBG) sensor technology was reviewed. Owing to their salient advantages, including immunity to electromagnetic interference, lightweight, compact size, high sensitivity, large operation bandwidth, and ideal multiplexing capability, FBG sensors have attracted considerable interest in the past three decades. Among these sensing physical quantities, temperature and strain are the most widely investigated ones. In this paper, the sensing principle of FBG sensors was briefly introduced first. Then, we reviewed the status of research and applications of FBG sensors. As very important for industrial applications, multiplexing and networking of FBG sensors had been introduced briefly. Moreover, as a key technology, the wavelength interrogation methods were also reviewed carefully. Finally, we analyzed the problems encountered in engineering applications and gave a general review on the development of interrogation methods of FBG sensor.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(42)
Parameters that control and influence the organo-metal halide perovskite crystallization and morphology
Front. Optoelectron..  2016, 9 (1): 44-52.
Abstract   HTML   PDF (1996KB)

This review discusses various parameters that influence and control the organo-metal halide perovskite crystallization process. The effect of the perovskite morphology on the photovoltaic performance is a critical factor. Moreover, it has a dramatic effect on the stability of the perovskite, which has significant importance for later use of the organo-metal perovskite in assorted applications. In this review, we brought together several research investigations that describe the main parameters that significantly influence perovskite crystallization, for example, the annealing process, the precursor solvent, anti-solvent treatment, and additives to the iteite solutions.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(36)
2-channel all optical demultiplexer based on photonic crystal ring resonator
Front Optoelec.  2013, 6 (2): 224-227.
Abstract   HTML   PDF (212KB)

In this paper, we proposed a 2-channel demultiplexer based on photonic crystal ring resonator (PCRR). For performing wavelength selection, we used two ring resonators, two different wavelengths were obtained by using two resonant rings with different values for the radius of dielectric rods. All the simulations and calculations have been done using Rsoft Photonic CAD software, which employs finite difference time domain (FDTD) method. The output channels were respectively at 1590.8 and 1593.8 nm, correspondingly had the quality factors of 7954 and 3984, the crosstalk values of -22 and -11 dB separately. The total footprint of our proposed structure is 681.36 μm2. Results suggest that 2-channels in the proposed structure are characterized with high transmission efficiency and low band width, resulting in a very sharp output spectrum and high quality factor values.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(30)
Recent progress on tandem structured dye-sensitized solar cells
Front Optoelec.  2012, 5 (4): 371-389.
Abstract   HTML   PDF (935KB)

Tandem structured dye-sensitized solar cells (DSSCs) can take full advantage of sunlight, effectively broadening the absorption spectrum of the cell, resulting in a higher open circuit voltage or short circuit current than that of the conventional DSSC with single light absorber. The theoretical maximum efficiency is therefore suggested to be over the Schottky-Queisser limit of 33%. Accordingly, tandem design of DSSC is thought to be a promising way to break the performance bottleneck of DSSC. Besides, the tandem designs also broaden the application diversity of DSSC technology, which will accelerate its scale-up industrial application. In this paper, we have reviewed the recent progress on photo-electrochemical applications associated with kinds of tandem designs of DSSCs, in general, which are divided into three kinds: “n-type DSSC+n-type DSSC,” “n-type DSSC+p-type DSSC” and “n-type DSSC+other solar conversion devices.” The working principles, advantages and challenges of these tandem structured DSSCs have been discussed. Some possible solutions for further studies have been also pointed out together.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(30)
Photonic crystal fibers, devices, and applications
Wei JIN, Jian JU, Hoi Lut HO, Yeuk Lai HOO, Ailing ZHANG
Front Optoelec.  2013, 6 (1): 3-24.
Abstract   HTML   PDF (1824KB)

This paper reviews different types of air-silica photonic crystal fibers (PCFs), discusses their novel properties, and reports recent advances in PCF components and sensors as well as techniques for splicing PCFs to standard telecomm fibers.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(24)
High-performance, stable and low-cost mesoscopic perovskite (CH3NH3PbI3) solar cells based on poly(3-hexylthiophene)-modified carbon nanotube cathodes
Xiaoli ZHENG,Haining CHEN,Zhanhua WEI,Yinglong YANG,He LIN,Shihe YANG
Front. Optoelectron..  2016, 9 (1): 71-80.
Abstract   HTML   PDF (2195KB)

This work explores the use of poly(3-hexylthiophene) (P3HT) modified carbon nanotubes (CNTs@P3HT) for the cathodes of hole transporter free, mesoscopic perovskite (CH3NH3PbI3) solar cells (PSCs), simultaneously achieving high-performance, high stability and low-cost PSCs. Here the thin P3HT modifier acts as an electron blocker to inhibit electron transfer into CNTs and a hydrophobic polymer binder to tightly cross-link the CNTs together to compact the carbon electrode film and greatly stabilize the solar cell. On the other hand, the presence of CNTs greatly improve the conductivity of P3HT. By optimizing the concentration of the P3HT modifier (2 mg/mL), we have improved the power conversion efficiencies (PCEs) of CNTs@P3HT based PSCs up to 13.43% with an average efficiency of 12.54%, which is much higher than the pure CNTs based PSCs (best PCE 10.59%) and the sandwich-type P3HT/CNTs based PSCs (best PCE 9.50%). In addition, the hysteresis of the CNTs@P3HT based PSCs is remarkably reduced due to the intimate interface between the perovskite and CNTs@P3HT electrodes. Degradation of the CNTs@ P3HT based PSCs is also strongly retarded as compared to cells employing the pure CNTs electrode when exposed to the ambient condition of 20%-40% humidity.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(24)
Laser-based micro/nanofabrication in one, two and three dimensions
Wei XIONG,Yunshen ZHOU,Wenjia HOU,Lijia JIANG,Masoud MAHJOURI-SAMANI,Jongbok PARK,Xiangnan HE,Yang GAO,Lisha FAN,Tommaso BALDACCHINI,Jean-Francois SILVAIN,Yongfeng LU
Front. Optoelectron..  2015, 8 (4): 351-378.
Abstract   HTML   PDF (9304KB)

Advanced micro/nanofabrication of functional materials and structures with various dimensions represents a key research topic in modern nanoscience and technology and becomes critically important for numerous emerging technologies such as nanoelectronics, nanophotonics and micro/nanoelectromechanical systems. This review systematically explores the non-conventional material processing approaches in fabricating nanomaterials and micro/nanostructures of various dimensions which are challenging to be fabricated via conventional approaches. Research efforts are focused on laser-based techniques for the growth and fabrication of one-dimensional (1D), two-dimensional (2D) and three-dimensional (3D) nanomaterials and micro/nanostructures. The following research topics are covered, including: 1) laser-assisted chemical vapor deposition (CVD) for highly efficient growth and integration of 1D nanomaterial of carbon nanotubes (CNTs), 2) laser direct writing (LDW) of graphene ribbons under ambient conditions, and 3) LDW of 3D micro/nanostructures via additive and subtractive processes. Comparing with the conventional fabrication methods, the laser-based methods exhibit several unique advantages in the micro/nanofabrication of advanced functional materials and structures. For the 1D CNT growth, the laser-assisted CVD process can realize both rapid material synthesis and tight control of growth location and orientation of CNTs due to the highly intense energy delivery and laser-induced optical near-field effects. For the 2D graphene synthesis and patterning, room-temperature and open-air fabrication of large-scale graphene patterns on dielectric surface has been successfully realized by a LDW process. For the 3D micro/nanofabrication, the combination of additive two-photon polymerization (TPP) and subtractive multi-photon ablation (MPA) processes enables the fabrication of arbitrary complex 3D micro/nanostructures which are challenging for conventional fabrication methods. Considering the numerous unique advantages of laser-based techniques, the laser-based micro/nanofabrication is expected to play a more and more important role in the fabrication of advanced functional micro/nano-devices.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(24)
Recent progresses on optical arbitrary waveform generation
Ming LI,José AZA?A,Ninghua ZHU,Jianping YAO
Front. Optoelectron..  2014, 7 (3): 359-375.
Abstract   HTML   PDF (3867KB)

This paper reviews recent progresses on optical arbitrary waveform generation (AWG) techniques, which could be used to break the speed and bandwidth bottlenecks of electronics technologies for waveform generation. The main enabling techniques for optically generating optical and microwave waveforms are introduced and reviewed in this paper, such as wavelength-to-time mapping techniques, space-to-time mapping techniques, temporal pulse shaping (TPS) system, optoelectronics oscillator (OEO), programmable optical filters, optical differentiator and integrator and versatile electro-optic modulation implementations. The main advantages and challenges of these optical AWG techniques are also discussed.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(22)
FBG-based smart bed system for healthcare applications
Jianzhong HAO, Maniyeri JAYACHANDRAN, Poh Leong KNG, Siang Fook FOO, Phyo Wai AUNG AUNG, Zhaohui CAI,
Front. Optoelectron..  2010, 3 (1): 78-83.
Abstract   PDF (306KB)
This paper presents a smart fiber Bragg grating (FBG) sensor system with an unobtrusive and easy-to-use FBG sensor bed, which automatically monitors the behavior of bedridden patients and their vital signs based on indicative spatio-temporal signature for adaptive intervention triggering and activity planning. We present the subtle design, fabrication, calibration, implementation and deployment issues of the FBG pressure sensors to be used in hospitals or nursing homes to prevent bedsore generation, patient falling out of the bed, and life-threatening situations such as patient’s heart rate weakening, breathing pattern change, etc. Through trials conducted in the laboratory for respiratory rate monitoring with a sample group of 10 subjects, the system showed maximum error of±€1 breaths per minute as compared to manual counting.
Reference | Related Articles | Metrics
Cited: Crossref(22)
Two-dimensional material functional devices enabled by direct laser fabrication
Tieshan YANG, Han LIN, Baohua JIA
Front. Optoelectron..  2018, 11 (1): 2-22.
Abstract   HTML   PDF (1167KB)

During the past decades, atomically thin, two-dimensional (2D) layered materials have attracted tremendous research interest on both fundamental properties and practical applications because of their extraordinary mechanical, thermal, electrical and optical properties, which are distinct from their counterparts in the bulk format. Various fabrication methods, such as soft-lithography, screen-printing, colloidal-templating and chemical/dry etching have been developed to fabricate micro/nanostructures in 2D materials. Direct laser fabrication with the advantages of unique three-dimensional (3D) processing capability, arbitrary-shape designability and high fabrication accuracy up to tens of nanometers, which is far beyond the optical diffraction limit, has been widely studied and applied in the fabrication of various micro/nanostructures of 2D materials for functional devices. This timely review summarizes the laser-matter interaction on 2D materials and the significant advances on laser-assisted 2D materials fabrication toward diverse functional photonics, optoelectronics, and electrochemical energy storage devices. The perspectives and challenges in designing and improving laser fabricated 2D materials devices are discussed as well.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(21)
Donor design and modification strategies of metal-free sensitizers for highly-efficient n-type dye-sensitized solar cells
Xiaoyu ZHANG,Michael Grätzel,Jianli HUA
Front. Optoelectron..  2016, 9 (1): 3-37.
Abstract   HTML   PDF (6036KB)

Dye-sensitized solar cells (DSSCs) cannot be developed without the research on sensitizers. As the key of light harvesting and electron generation, thousands of sensitizers have been designed for the application in DSSC devices. Among them, organic sensitizers have drawn a lot of attention because of the flexible molecular design, easy synthesis and good photovoltaic performance. Recently, new record photovoltaic conversion efficiencies of 11.5% for DSSCs with iodide electrolyte and 14.3% for DSSCs with cobalt electrolyte and co-sensitization have been achieved with organic sensitizers. Here we focus on the donor design and modification of organic sensitizers. Several useful strategies and corresponding typical examples are presented.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(21)
Low phase noise hybrid silicon mode-locked lasers
Front. Optoelectron..  2014, 7 (3): 265-276.
Abstract   HTML   PDF (2773KB)

In this paper, we review recent results on hybrid silicon mode-locked lasers with a focus on low phase noise optical pulse generation. Taking a high level design approach to lowering phase noise, we show the need for long on-chip optical delay lines for mode-locked lasers to reach and overcome material limits. Key results include demonstration of the longest (cavity length 9 cm) integrated on-chip mode locked laser, 14 dB reduction of Lorentzian noise on a 20 GHz radio-frequency (RF) signal, and greater than 55 dB optical supermode noise suppression using harmonically mode locked long cavity laser, 10 GHz passively mode locked laser with 15 kHz linewidth using on-chip all optical feedback stabilization.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(20)
Broadband and conformal metamaterial absorber
Xiangkun KONG, Junyi XU, Jin-jun MO, Shaobin LIU
Front. Optoelectron..  2017, 10 (2): 124-131.
Abstract   HTML   PDF (451KB)

In this study, a new broadband and conformal metamaterial absorber using two flexible substrates was proposed. Simulation results showed that the proposed absorber exhibited an absorption band from 6.08 to 13.04 GHz and a high absorption of 90%, because it was planar. The absorber was broadband as its relative absorption bandwidth was 72.8%. Moreover, the proposed absorber was insensitive to the polarization of the TE and TM waves. The absorber was ultra-thin; its total thickness was only 0.07λ at the lowest operating frequency. Furthermore, different regions of absorption can be adjusted by lumping and loading two resistors onto the polyimide film, respectively. Moreover, compared with the conventional microwave absorber, the absorption bandwidth of the proposed absorber can be broadened and enhanced when it was bent and conformed to the surface of objects. Experimental and simulation results were in agreement. The proposed absorber is a promising absorbing element in scientific and technical applications because of its broadband absorption, polarization insensitivity, and flexible substrates.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(20)
Chemical sensing through photonic crystal fiber: sulfuric acid detection
Etu PODDER, Md. Bellal HOSSAIN, Rayhan Habib JIBON, Abdullah Al-Mamun BULBUL, Himadri Shekhar MONDAL
Front. Optoelectron..  2019, 12 (4): 372-381.
Abstract   HTML   PDF (1902KB)

A photonic crystal fiber (PCF) for sensing of sulfuric acid is designed and analyzed using Comsol Multiphysics. To analyze the sensor performance, 0%, 10%, 20%, 30%, 40% H2SO4 solution is placed into the fiber separately and then relative sensitivity, confinement loss, birefringence, effective area etc. are investigated for each solution over wavelength ranging from 0.8 to 1.8 mm. The sensor structure affords moderately high relative sensitivity and around 63.4% sensitivity is achieved for the highest concentration of H2SO4 at the wavelength 1.5 mm in x polarization direction. This PCF model also shows zero confinement loss for all solutions of H2SO4 over wavelength ranging from 1 to 1.35 mm and later on approximately 1.422 × 1017 dB/km confinement loss is found for the highest concentration of H2SO4 at 1.5 mm wavelength. Besides, higher birefringence is attained when the concentration of sulfuric acid is lower and it is achieved 7.5 × 104 at 1.5 mm wavelength. Moreover, higher sensing area is achieved at high concentration of sulfuric acid.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(20)
All-optical AND/OR/NOT logic gates based on photonic crystal ring resonators
Front. Optoelectron..  2016, 9 (4): 578-584.
Abstract   HTML   PDF (812KB)

Photonic crystal based ring resonators are best choice for designing all-optical devices. In this paper, we used a basic structure of photonic crystal ring resonators and designed all optical logic gates which are working using the Kerr effect. The proposed gates consisted of upper and lower waveguides coupled through a resonator which was designed for dropping of special wavelength. The resonance wavelength was designed for 1550 nm telecom operation wavelength. We used numerical methods such as plane wave expansion and finite difference time domain (FDTD) for performing our simulations and studied the optical properties of the proposed structures. Our results showed that the critical input power for triggering the gate output was lower compared to previously reported gates.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(19)
Investigation of ultra-broadband terahertz time-domain spectroscopy with terahertz wave gas photonics
Xiaofei LU,Xi-Cheng ZHANG
Front. Optoelectron..  2014, 7 (2): 121-155.
Abstract   HTML   PDF (1403KB)

Recently, air plasma, produced by focusing an intense laser beam to ionize atoms or molecules, has been demonstrated to be a promising source of broadband terahertz waves. However, simultaneous broadband and coherent detection of such broadband terahertz waves is still challenging. Electro-optical sampling and photoconductive antennas are the typical approaches for terahertz wave detection. The bandwidth of these detection methods is limited by the phonon resonance or carrier’s lifetime. Unlike solid-state detectors, gaseous sensors have several unique features, such as no phonon resonance, less dispersion, no Fabry-Perot effect, and a continuous renewable nature. The aim of this article is to review the development of a broadband terahertz time-domain spectrometer, which has both a gaseous emitter and sensor mainly based on author’s recent investigation. This spectrometer features high efficiency, perceptive sensitivity, broad bandwidth, adequate signal-to-noise ratio, sufficient dynamic range, and controllable polarization.

The detection of terahertz waves with ambient air has been realized through a third order nonlinear optical process: detecting the second harmonic photon that is produced by mixing one terahertz photon with two fundamental photons. In this review, a systematic investigation of the mechanism of broadband terahertz wave detection was presented first. The dependence of the detection efficiency on probe pulse energy, bias field strength, gas pressure and third order nonlinear susceptibility of gases were experimentally demonstrated with selected gases. Detailed discussions of phase matching and Gouy phase shift were presented by considering the focused condition of Gaussian beams. Furthermore, the bandwidth dependence on probe pulse duration was also demonstrated. Over 240 times enhancement of dynamic range had been accomplished with n-hexane vapor compared to conventional air sensor. Moreover, with sub-20 fs laser pulses delivered from a hollow fiber pulse compressor, an ultra-broad spectrum covering from 0.3 to 70 THz was also showed.

In addition, a balanced detection scheme using a polarization dependent geometry was developed by author to improve signal-to-noise ratio and dynamic range of conventional terahertz air-biased-coherent-detection (ABCD) systems. Utilizing the tensor property of third order nonlinear susceptibility, second harmonic pulses with two orthogonal polarizations was detected by two separated photomultiplier tubes (PMTs). The differential signal from these two PMTs offers a realistic method to reduce correlated laser fluctuation, which circumvents signal-to-noise ratio and dynamic range of conventional terahertz ABCD systems. A factor of two improvement of signal-to-noise ratio was experimentally demonstrated.

This paper also introduces a unique approach to directly produce a broadband elliptically polarized terahertz wave from laser-induced plasma with a pair of double helix electrodes. The theoretical and experimental results demonstrated that velocity mismatch between excitation laser pulses and generated terahertz waves plays a key role in the properties of the elliptically polarized terahertz waves and confirmed that the far-field terahertz emission pattern is associated with a coherent process. The results give insight into the important influence of propagation effects on terahertz wave polarization control and complete the mechanism of terahertz wave generation from laser-induced plasma.

This review provides a critical understanding of broadband terahertz time-domain spectroscopy (THz-TDS) and introduces further guidance for scientific applications of terahertz wave gas photonics.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(19)
Terahertz pulse imaging in archaeology
Front. Optoelectron..  2015, 8 (1): 81-92.
Abstract   HTML   PDF (4129KB)

The work presented in this paper was performed at the Oriental Institute at the University of Chicago, on objects from their permanent collection: an ancient Egyptian bird mummy and three ancient Sumerian corroded copper-alloy objects. We used a portable, fiber-coupled terahertz (THz) time-domain spectroscopic imaging system, which allowed us to measure specimens in both transmission and reflection geometry, and present time- and frequency-based image modes. The results confirm earlier evidence that THz imaging can provide complementary information to that obtainable from X-ray computed tomography (XRCT) scans of mummies, giving better visualisation of low density regions. In addition, we demonstrated that THz imaging can distinguish mineralized layers in metal artifacts.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(19)
Highly nonlinear enhanced-core photonic crystal fiber with low dispersion for wavelength conversion based on four-wave mixing
Front Optoelec.  2013, 6 (3): 297-302.
Abstract   HTML   PDF (203KB)

In this paper, a new structure of highly nonlinear low dispersion photonic crystal fiber (HN-PCF) by elliptical concentration of GeO2 in the PCF core has been proposed. Using finite difference time domain (FDTD) method, we have analyzed the dispersion properties and effective mode area in the HN-PCF. Simulative results show that the dispersion variation is within±0.65 ps/(nm?km) in C-band, especially 0.24 ps/(nm?km) in 1.55 μm wavelength. Effective area and nonlinear coefficient are 1.764 μm2 and 72.6 W-1?km-1 respectively at 1.55 μm wavelength. The proposed PCF demonstrates high nonlinear coefficient, ultra small effective mode area and nearly-zero flattened dispersion characteristics over C-band, which can have important application in all-optical wavelength conversion based on four wave mixing (FWM).

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(19)
Brief introduction to optical microfibers and nanofibers
Limin TONG,
Front. Optoelectron..  2010, 3 (1): 54-60.
Abstract   PDF (192KB)
When its diameter goes close to or below the wavelength of the guided light, an optical microfiber/nanofiber (MNF) exhibits favorable properties such as tight optical confinement, strong near-field interaction, and excellent mechanical strength, which offers plenty of choices for combining a variety of functionalized materials ranging from semiconductors and metals to laser dyes; opens up plenty of opportunities for developing microphotonic or nanophotonic devices; and inspires new opportunities for near-field optics, nonlinear optics, and quantum optics.
Reference | Related Articles | Metrics
Cited: Crossref(19)
Homeostatic photobiomodulation
Timon Chengyi LIU , Ruochun LIU , Ling ZHU , Jianqin YUAN , Min HU , Songhao LIU ,
Front. Optoelectron..  2009, 2 (1): 1-8.
Abstract   PDF (146KB)
Photobiomodulation (PBM) is a modulation of laser irradiation or monochromatic light (LI) on biosystems, which stimulates or inhibits biological functions but does not result in irreducible damage. LI might be of low intensity LI (LIL) (about 10 mW/cm2), or moderate intensity LI (MIL) (102―103 mW/cm2). PBM of LIL or MIL (LPBM or MPBM) is studied from the homeostatic viewpoint in this paper. Homeostasis is redefined as the function-specific homeostasis (FSH), a negative-feedback response of a biosystem which maintains the function-specific conditions inside it. PBM is classified into two kinds, the FSH-specific PBM (fPBM) and developmental PBM (dPBM). For fPBM, there is no PBM of LI on the function in FSH, but there is PBM of LI on the function far from FSH. dPBM can disrupt FSH. It can be found that LPBM is an fPBM, and whether MPBM is fPBM or dPBM depends on MIL dose and cell sensitivity. Low level LI therapy is just clinical applications of fPBM, so that it is a cellular rehabilitation.
Reference | Related Articles | Metrics
Cited: Crossref(18)
Thermal conductivity of doped YAG and GGG laser crystal
WANG Baosong, JIANG Haihe, JIA Xiande, ZHANG Qingli, SUN Dunlu, YIN Shaotang
Front. Optoelectron..  2008, 1 (1-2): 138-141.
Abstract   HTML   PDF (110KB)
Reference | Related Articles | Metrics
Cited: Crossref(18)
Direct band gap luminescence from Ge on Si pin diodes
Front Optoelec.  2012, 5 (3): 256-260.
Abstract   HTML   PDF (103KB)

Germanium (Ge) pin photodiodes show clear direct band gap emission at room temperature, as grown on bulk silicon in both photoluminescence (PL) and electroluminescence (EL). PL stems from the top contact layer with highly doped Ge because of strong absorption of visible laser light excitation (532 nm). EL stems from the recombination of injected carriers in the undoped intrinsic layer. The difference in peak positions for PL (0.73 eV) and EL (0.80 eV) is explained by band gap narrowing from high doping in n+-top layer. A superlinear increase of EL with current density is explained by a rising ratio of direct/indirect electron densities when quasi Fermi energy level rises into the conduction band. An analytical model for the direct/indirect electron density ratio is given using simplifying assumptions.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(18)
Antimony doped Cs2SnCl6 with bright and stable emission
Jinghui LI, Zhifang TAN, Manchen HU, Chao CHEN, Jiajun LUO, Shunran LI, Liang GAO, Zewen XIAO, Guangda NIU, Jiang TANG
Front. Optoelectron..  2019, 12 (4): 352-364.
Abstract   HTML   PDF (3339KB)

Lead halide perovskites, with high photoluminescence efficiency and narrow-band emission, are promising materials for display and lighting. However, the lead toxicity and environmental sensitivity hinder their potential applications. Herein, a new antimony-doped lead-free inorganic perovskites variant Cs2SnCl6:xSb is designed and synthesized. The perovskite variant Cs2SnCl6:xSb exhibits a broadband orange-red emission, with a photoluminescence quantum yield (PLQY) of 37%. The photoluminescence of Cs2SnCl6:xSb is caused by the ionoluminescence of Sb3+ within Cs2SnCl6 matrix, which is verified by temperature dependent photoluminescence (PL) and PL decay measurements. In addition, the all inorganic structure renders Cs2SnCl6:xSb with excellent thermal and water stability. Finally, a white light-emitting diode (white-LED) is fabricated by assembling Cs2SnCl6:0.59%Sb, Cs2SnCl6:2.75%Bi and Ba2Sr2SiO4:Eu2+ onto the commercial UV LED chips, and the color rendering index (CRI) reaches 81.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(18)
Recent advances in microwave photonics
Ming LI,Ninghua ZHU
Front. Optoelectron..  2016, 9 (2): 160-185.
Abstract   HTML   PDF (6583KB)

Microwave photonics (MWP) is an interdisciplinary field that combines two different areas of microwave engineering and photonics. It has several key features by transferring signals between the optical domain and microwave domain, which leads to the advantages of broad operation bandwidth for generation, processing and distribution of microwave signals and high resolution for optical spectrum measurement. In this paper, we comprehensively review past and current status of MWP in China by introducing the representative works from most of the active MWP research groups. Future prospective is also discussed from the national strategy to key enabling technology that we have developed.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(17)
Asymmetric resonant cavities and their applications in optics and photonics: a review
Yun-Feng XIAO, Yan LI, Qihuang GONG, Chang-Ling ZOU, Chun-Hua DONG, Zheng-Fu HAN,
Front. Optoelectron..  2010, 3 (2): 109-124.
Abstract   PDF (844KB)
Asymmetric resonant cavities (ARCs) with smoothly deformed boundaries are currently under intensive study because they possess distinct properties that conventional symmetric cavities cannot provide. On one hand, it has been demonstrated that ARCs allow for highly directional emission instead of the in-plane isotropic light output in symmetric whispering-gallery cavities, such as microdisks, microspheres, and microtoroids. On the other hand, ARCs behave like open billiard system and thus offer an excellent platform to test classical and quantum chaos. This article reviews the recent progresses and prospects for the experimental realization of ARCs, with applications toward highly directional microlasing, strong-coupling light-matter interaction, and highly sensitive biosensing.
Reference | Related Articles | Metrics
Cited: Crossref(17)
Application of broadband terahertz spectroscopy in semiconductor nonlinear dynamics
I-Chen HO,Xi-Cheng ZHANG
Front. Optoelectron..  2014, 7 (2): 220-242.
Abstract   HTML   PDF (1153KB)

Semiconductor nonlinearity in the range of terahertz (THz) frequency has been attracting considerable attention due to the recent development of high-power semiconductor-based nanodevices. However, the underlying physics concerning carrier dynamics in the presence of high-field THz transients is still obscure. This paper introduces an ultrafast, time-resolved THz pump/THz probe approach to study semiconductor properties in a nonlinear regime. The carrier dynamics regarding two mechanisms, intervalley scattering and impact ionization, was observed for doped InAs on a sub-picosecond time scale. In addition, polaron modulation driven by intense THz pulses was experimentally and theoretically investigated. The observed polaron dynamics verifies the interaction between energetic electrons and a phonon field. In contrast to previous work which reported optical phonon responses, acoustic phonon modulations were addressed in this study. A further understanding of the intense field interacting with solid materials will accelerate the development of semiconductor devices.

This paper can be divided into 4 sections. Section 1 starts with the design and performance of a table-top THz spectrometer, which has the advantages of ultra-broad bandwidth (one order higher bandwidth compared to a conventional ZnTe sensor) and high electric field strength (>100 kV/cm). Unlike the conventional THz time-domain spectroscopy, the spectrometer integrated a novel THz air-biased-coherent-detection (THz-ABCD) technique and utilized gases as THz emitters and sensors. In comparison with commonly used electro-optic (EO) crystals or photoconductive (PC) dipole antennas, the gases have the benefits of no phonon absorption as existing in EO crystals and no carrier life time limitation as observed in PC dipole antennas. In Section 2, the newly development THz-ABCD spectrometer with a strong THz field strength capability provides a platform for various research topics especially on the nonlinear carrier dynamics of semiconductors. Two mechanisms, electron intervalley scattering and impact ionization of InAs crystals, were observed under the excitation of intense THz field on a sub-picosecond time scale. These two competing mechanisms were demonstrated by changing the impurity doping type of the semiconductors and varying the strength of the THz field.

Another investigation of nonlinear carrier dynamics in Section 3 was the observation of coherent polaron oscillation in n-doped semiconductors excited by intense THz pulses. Through modulations of surface reflection with a THz pump/THz probe technique, this work experimentally verifies the interaction between energetic electrons and a phonon field, which has been theoretically predicted by previous publications, and shows that this interaction applies for the acoustic phonon modes. Usually, two transverse acoustic (2TA) phonon responses are inactive in infrared measurement, while they are detectable in second-order Raman spectroscopy. The study of polaron dynamics, with nonlinear THz spectroscopy (in the far-infrared range), provides a unique method to diagnose the overtones of 2TA phonon responses of semiconductors, and therefore incorporates the abilities of both infrared and Raman spectroscopy. Finally, some conclusions were presented in Section 4. In a word, this work presents a new milestone in wave-matter interaction and seeks to benefit the industrial applications in high power, small scale devices.

Table and Figures | Reference | Related Articles | Metrics
Cited: Crossref(17)