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Recent advances in development of vertical-cavity based short pulse source at 1.55 μm
Zhuang ZHAO, Sophie BOUCHOULE, Jean-Christophe HARMAND, Gilles PATRIARCHE, Guy AUBIN, Jean-Louis OUDAR
Front Optoelec. 2014, 7 (1): 1-19.
https://doi.org/10.1007/s12200-014-0387-5
This paper reviews and discusses recent developments in passively mode-locked vertical external cavity surface emitting lasers (ML-VECSELs) for short pulse generation at 1.55 μm. After comparing ML-VECSELs to other options for short pulse generation, we reviewed the results of ML-VECSELs operating at telecommunication wavelength and point out the challenges in achieving sub-picosecond operation from a ML-VECSEL at 1.55 μm. We described our recent work in the VECSELs and semiconductor saturable absorber mirrors (SESAMs), their structure design, optimization and characterization, with the goal of moving the pulse width from picosecond to sub-picosecond.
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Semitransparent organic solar cells
Furong ZHU
Front Optoelec. 2014, 7 (1): 20-27.
https://doi.org/10.1007/s12200-014-0395-5
The organic solar cell technology has attracted great interests due to its potential of low cost solution process capability. Bulk heterojunction organic solar cells offer a potentially much cheaper alternative way to harness solar energy, and can be made flexible and large area. They can also be made translucent and in different colors. As a result, the inexpensive fabrication process such as solution-process techniques, mechanical flexibility, light weight and visible-light transparency features make organic solar technology attractive for application in new markets, such as smart sensors, power generating window panes, building architecture, greenhouses and outdoor lifestyle, etc. After a brief overview of basics of organic photovoltaics, the enhancement of semitransparent organic solar cells over the two competing performance indices of power conversion efficiency and transmittance will be discussed.
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Recent progress of traditional Chinese medical science based on theory of biophoton
Xiuxiu WANG, Jinzhao HUANG, Jinxiang HAN, Meina YANG, Jingxiang PANG, Xiaolei ZHAO
Front Optoelec. 2014, 7 (1): 28-36.
https://doi.org/10.1007/s12200-013-0367-1
With the development of biophotonics, biophoton detection technology has been appropriately used. In this paper, the main features and fundamental conceptions of biophotonics were introduced basically. Then the coherence theory of biophoton emission was reviewed. Furthermore, based on this coherence concept, the quantum theory of traditional Chinese medicine (TCM) and properties of Chinese medicinal herbs were presented. To show the nature of biophoton emission in living systems and clarify its basic detection mechanism, high sensitive detection system which allows non-invasive and non-destructive (or less) recording was finally presented.
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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.
https://doi.org/10.1007/s12200-014-0389-3
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.
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Texturization and rounded process of silicon wafers for heterojunction with intrinsic thin-layer solar cells
Kunpeng MA, Xiangbin ZENG, Qingsong LEI, Junming XUE, Yanzeng WANG, Chenguang ZHAO
Front Optoelec. 2014, 7 (1): 46-52.
https://doi.org/10.1007/s12200-013-0386-y
Heterojunction with intrinsic thin-layer (HIT) solar cells are sensitive to interface state density. Traditional texture process for silicon solar cells is not suitable for HIT one. Thus, sodium hydroxide (NaOH), isopropanol (IPA) and mixed additive were tentatively introduced for the texturization of HIT solar cells in this study. Then, a mixture including nitric acid (HNO3), hydrofluoric acid (HF) and glacial acetic acid (CH3COOH) was employed to round pyramid structure. The morphology of textured surface and the influence of etching time on surface reflectance were studied, and the relationship between etching time and surface reflectance, vertex angle of pyramid structure was analyzed. It was found that the mixture consisting of 1.1 wt% NaOH, 3 vol% IPA and 0.3 vol% additives with etching time of 22.5 min is the best for HIT solar cells under the condition of 80°C. Uniform pyramid structure was observed and the base width of pyramid was about 2–4 μm. The average surface reflectance was 11.68%. Finally the effect of different processes on the performance of HIT solar cells was investigated. It was shown that these texturization and rounding techniques used in this study can increase short circuit current (Jsc), but they have little influence on fill factor (FF) and open circuit voltage (Voc) of HIT solar cells.
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A micro-spectrometer with phase modulation array
Tao YANG, Yuchao CHEN, Xing’ao LI, Wei HUANG, Yongyuan ZHU
Front Optoelec. 2014, 7 (1): 59-63.
https://doi.org/10.1007/s12200-013-0363-5
A micro-spectrometer with phase modulation array is investigated in this paper. The vital component of this micro-spectrometer is a micro-interferometer array, which is built on a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). Each element of micro-interferometer array is formed by polymethyl methacrylate (PMMA) grooves with different depth. When we illuminate the surface of the interferometer array, different interference intensity distribution would be formed at the bottom of each micro-interferometer. Optical power of this interferometer can be measured by the pixels of CCD or CMOS. The data can be substituted into a linear system. By solving the linear system with Tikhonov regularization method, spectrum of the incident beam can be reconstructed. Simulation results prove that the detection range of the spectrometer is a wide wavelength range covering from 300 to 1100 nm. Furthermore, the wavelength resolution of the device reaches picometer level. In comparison with conventional spectrometers, the novel spectrometer has distinct advantages of small size, low cost, high resolution, wide spectral measurement range, real-time measurement, and so on.
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Simulation analysis of combined UV/blue photodetector in CMOS process by technology computer-aided design
Changping CHEN, Xiangliang JIN, Lizhen TANG, Hongjiao YANG, Jun LUO
Front Optoelec. 2014, 7 (1): 69-73.
https://doi.org/10.1007/s12200-013-0375-1
A composite ultraviolet (UV)/blue photodetector structure has been proposed, which is composed of P-type silicon substrate, Pwell, Nwell and N-channel metal-oxide-semiconductor field-effect transistor (NMOSFET) realized in the Pwell. In this photodetector, lateral ring-shaped Pwell-Nwell junction was used to separate the photogenerated carriers, and non-equilibrium excess hole was injected to the Pwell bulk for changing the bulk potential and shifting the NMOSFET’s threshold voltage as well as the output drain current. By technology computer-aided design (TCAD) device, simulation and analysis of this proposed photodetector were carried out. Simulation results show that the combined photodetector has enhanced responsivity to UV/blue spectrum. Moreover, it exhibits very high sensitivity to weak and especially ultral-weak optical light. A sensitivity of 7000 A/W was obtained when an incident optical power of 0.01 μW was illuminated to the photodetector, which is 35000 times higher than the responsivity of a conventional silicon-based UV photodiode (usually is about 0.2 A/W). As a result, this proposed combined photodetector has great potential values for UV applications.
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Multiband infrared luminescence of Er3+-Ho3+-Nd3+/Tm3+-codoped telluride glasses
Yaojing ZHANG, Lu SUN, Ying CHANG, Wenbin LI, Chun JIANG
Front Optoelec. 2014, 7 (1): 74-76.
https://doi.org/10.1007/s12200-013-0374-2
This paper reports the simultaneous emissions around 1.53, 1.80, 2.10, 2.70 and 3.00 μm in Er3+-Ho3+ -Nd3+/Tm3+-codoped telluride glasses upon excitation of a conventional 808 nm laser diode. Both emission bands of 1.53 and 2.70 μm were assigned to the transitions of 4I13/2 -4I15/2, 4I11/2 -4I13/2 of Er3+ ions, respectively, the emission near 1.80 mm was assigned to the transition 4F4 -4H6 of Tm3+ ions, and the emissions at 2.10 and 3.00 mm arose from the transitions of 5I7 -5I8, 5I6 -5I7 of Ho3+ ions. The materials are promising for ultra-broad band amplified spontaneous emission optical sources at near and middle infrared region.
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