Frontiers of Optoelectronics

Bài báo này giới thiệu một cấu trúc mới cho cảm biến từ tính sử dụng giao thoa kế sợi quang Mach-Zehnder/Sagnac. Cảm biến sợi quang có tính từ trở được đặt trong một trong hai nhánh của giao thoa kế Mach-Zehnder, có khả năng phát hiện độ dịch pha quang bằng cách kiểm tra sự khác biệt chiều dài của nhánh do trường từ trường môi trường gây ra. Nhờ vào việc truyền đi và truyền về trong các nhánh, giao thoa kế sợi quang Mach-Zehnder/Sagnac có thể luận suy chính xác gấp đôi độ dịch pha tỷ lệ với sự khác biệt chiều dài như giao thoa kế Mach-Zehnder. Về lý thuyết, mô tả về giao thoa kế Mach-Zehnder/Sagnac được đưa ra, và một số vấn đề chính trong cảm biến trường từ với giao thoa kế sợi quang được chứng minh thông qua thí nghiệm. Các cảm biến từ tính được thực hiện sử dụng các phương pháp đã đề xuất.

A novelty dispersion ultra-flattened Bragg photonic crystal fiber (PCF) has been fabricated in this paper. The fiber is composed of compound cores and periodical claddings with 11 coaxial rings. It has flattened dispersion of 8.5±1.3 ps·(nm·km)−1 in the communication wavelength range of 1460–1625 nm. Its dispersion slope alters from −0.0428 to 0.0392 ps·nm−2·km−1. The low attenuation of 0.52 dB/km and low bending loss of 0.09 dB at 1550 nm of the fiber are also achieved. The Bragg PCF has enormously potential application in the fields of dense wavelength division multiplexing systems because of its superior dispersion properties and easy splicing performances.

Phosphorus-doped p-type ZnO thin films are prepared on glass substrates by metalorganic chemical vapor deposition (MOCVD). DEZn, O2, and P2O5 powders are used as reactant and dopant sources. The p-type ZnO films are grown at a temperature between 673 K and 723 K. The best p-type sample has a low resistivity of 4.64 Ω·cm, a hole concentration of 1.61 × 1018 cm−3, and a Hall mobility of 0.838 cm2·(V·s)−1 at room temperature. A strong emission peak at 3.354 eV corresponding to neutral acceptor bound excitons is observed at 77 K in the photoluminescence spectra, which further verifies the p-type characteristics of the films.

Nanoflake-based flower-like CuO nanostructures have been synthesized through thermal decomposition of [Cu(NH3)4]2+ solution without any surfactants and catalysts at low temperature. The products are characterized by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM). The possible formation process based on the aggregation-recrystallization mechanism is proposed. Finally, the obtained flowerlike CuO hierarchical nanostructures have been used as the photocatalyst in the experiments. It is found that the asprepared flower-like CuO hierarchical nanostructures exhibit superior photocatalytic property on photocatalytic decomposition of Rhodamine B due to their hierarchical structures.

In recent decades, diffuse optical tomography (DOT) has drawn more and more interest in molecular imaging because of its advantage of large penetration depth in optical image technology. However, ill-posedness problems have dramatically limited this application technique. In this paper, a new method to remove the ill-posedness of DOT is introduced. With a rotating steady-state domain experiment system, by increasing experimental data that could be obtained from any visual angle, four contrast experiments were simulated. It was proved that when the sum of the experiment data is larger than that of the unknown optical coefficient of phantom, ill-posedness would be reduced and the quality of the reconstructed image could be improved.

In this paper, vanadium oxide thin film of TCR of −3.5%/K has been deposited by pulsed DC magnetron sputtering method. The property of this VO x has been investigated by X-ray diffractometer (XRD) and atomic force microscopy (AFM) in detail. XRD test indicates that this film is composed of V2O3, V3O5 and VO2.VO x microbolometer with infrared (IR) absorbing structure is fabricated based on porous silicon sacrificial layer technology. Optimized micro-bridge structure is designed and carried out to decrease thermal conductance and this structure shows good compatibility with micromachining technology. This kind of bolometer with 74% IR absorption of 8–14 μm, has maximum detectivity of 1.09×109 cm·Hz1/2/W at 24 Hz frequency and 9.8 μA bias current.

The performance of the hybrid optical code-division multiple-access (OCDMA) and wavelength division multiplexing (WDM) network is analyzed. End-to-end bit error rate (BER) of the network adopting error correction coding is calculated, and the expressions which show spectral efficiency performance, including the effects of polarization mode dispersion (PMD), are derived. The result demonstrates that PMD can decrease spectral efficiency dramatically. Analysis of the blocking performance with and without orthogonal optical codes (OOCs) and wavelength conversion shows that OOC and wavelength can improve the performance of the network. Since the wavelength conversion is much more costly than OOC conversion, a scheme for spare placement wavelength conversion is introduced to balance the cost and performance.

A laser ranging system using a two-frequency laser is demonstrated, and the lidar-radar concept is introduced. A laser beam carrying 100 MHz radio frequency is obtained by a monolithic nonplanar ring single-frequency oscillator and an acousto-optical modulator, which is used as the light source of the two-frequency detecting experimental setup. With the optical transmitting and collecting system, the displacement information of a target mounted on a motorized translation stage is achieved. In signal processing, the displacement is obtained by calculating the phase difference between the reference and detection signals executed by a radio-frequency lock-in amplifier. The ranging system turns the optical heterodyne into an electronic demodulation, and the repetition error is less than 3%. The system takes advantage of the signal processing technologies of radar, and meanwhile maintains the advantages of laser detection.

Self-assembled InAs quantum dots with graded composition strain-reducing layer (SRL) grown on exact substrates were studied. It is shown that a graded In x Ga1 − x As SRL leads to growth quality improvement, emission efficiency enhancement, and wavelength blueshift. Samples grown on 2° misoriented substrates with different In contents in graded In x Ga1 − x As SRL were also investigated, and emission efficiency enhancement and wavelength blueshift were found when graded SRL was introduced and when the change rate of In content in graded In x Ga1 − x As SRL was enlarged.