微小型高分辨率光纤光谱仪在等离子体领域的应用

等离子体是继气体、液体、固体后的第4种物质聚集态。等离子体物理学是一门蓬勃发展的新兴学科,其应用领域包括受控热核聚变、空间科学、环境科学、微电子与信息产业、材料合成与处理、国防和高技术应用等诸多方面。目前,测量等离子体最简单的方法就是使用荷兰Avantes公司的微小型、高分辨率、多通道光纤光谱仪。

Design of fiber-optic collector for spectrometer based on curved mirror

To enlarge the detection range of traditional fiber-optic spectrometer,two rotating parabolic mirrors were first used in the design of fiber-optic collector for spectrometer,which can extend the detection range of spectrometer from centimeter-scale to50m,as a super-low altitude remote sensing detector under passive lighting conditions.According to the performance requirements of fiber-spectrometer for optical collector,this study deduced the calculation formulae of design size of parabolic optical collector applied to different sensitivity spectrometers,different detection targets,different detection ranges and different weathers.Based on the calculation results,the model of fiber-optic collector with a diameter of16mm and a height of7.8mm was designed by ZEMAX.And then,TracePro,a light simulation software,was applied to ray tracing.The simulation results of optical radiation magnification agrees well with theoretical value,and the relative error is less than0.78%.This optical collector can effectively extend the detection range of spectrometer and expand its application fields and scopes.Compared with traditional refractive optical collector,it has several advantages of compact structure,low weight and low cost.

Novel si mulation method for fiber Bragg grating under inhomogeneous strainfields

The spectra of fiber Bragg grating (FBG) in inhomogeneous strain fields are distorted due to its inhomogeneity of both the periods and the effective refractive index. The couple mode theory and the Runge-Kutta method can be employed for exact simulation of the spectrum of Bragg grating in such field, but the convergence speed is slow. On the other hand, although the transfer matrix method could be used with higher convergence speed, the precision is poor because of the neglect of the grads of strain change. By improving the FBG equivalent period, a novel simulation method based on a modified transfer matrix method is proposed, which has the advantage of quick-convergence as well as good accuracy.

Characteristics measurement of gain and refractive index of traveling-wave semiconductor optical amplifier

A novel method to measure the gain and refractive index characteristics of traveling-wave semiconductor optical amplifier（TMA） is presented. In-out fiber ends of TWA are used to construct an external cavity resonator to produce big ripple on amplified spontaneous emission（ASE） spectrum. By this means,Hakki-Paoli method is adepted to obtain the gain spectra of TWA over a wide spectral range. From measured longitudinal mode spacing and peak wavelength shift due to increased bias current, we further calculate the effective refractive index and the refractive index change. Special feature of refractive index change above lasing threshold is revealed and explained.

Novel Portable Oil Ingredient Instrument with Optical Fiber Link

The operation principle of a novel portable oil ingredient instrument is introduced. Using the theory of fluorescence measurement, this instrument can carry out fast and consecutive in-situ detection of oil ingredient in sea water, confirming fast and correctly the situation of oil contamination such as the concentration and the area, etc. The lowest detectable concentration for the instrument is 1×10 -8 g/ml with the precision of less than 3 %. The results of experiment and practice show that this system has well water-sealed characteristic and repeatability.

Gain Characteristics of Fiber Optical Parametric Amplifier

The theory model of fiber optical parametric amplifier (FOPA) was introduced, which is based on optical nonlinear effect. And then numerical simulation was done to analyze and discuss the gain spectral characteristics of one-pump and two-pump FOPA. The results show that for one-pump FOPA, when pump wavelength is near to fiber zero-dispersion wavelength(ZDW), the gain flatness is better, and with the increase of the pump power, fiber length and its nonlinear coefficient, the gain value will increase while the gain bandwidth will become narrow. For two-pump FOPA, when the pump central wavelength is near to fiber ZDW, the gain flatness is better. Moreover, by decreasing the space of two pumps wavelength, the gain flatness can be improved. Finally, some problems existing in FOPA were addressed.

Supercontinuum Generation in DSF Pumped by Actively Mode-Locked Fiber Laser

The supercontinuum (SC) generation at the repetition rate of 10 GHz is presented. The SC is generated in a 4.2 km conventional dispersion-shifted fiber ( DSF), which is produced with nonlinear effects and group velocity dispersion. The DSF is pumped by an actively mode-locked Er3+ -doped fiber laser with pulse width of 7.97 ps. A novel SC pulse source with a bandwidth up to 125 nm is obtained, which covers the whole C, L bands and part of S band. The stable, narrow pulses with mean pulse-width of 9.7 ps and time-bandwidth product of 0.48 are filtered out across the whole SC bandwidth. This supercontinuum pulse source is suitable for future high-speed optical communications.

PROBING PLASMA SPECIES IN A TM_(010) CAVITY

ith the aid of a fibre optical device, the profile of plasma parameters, such as plasma length and noise power spectrum, in a normally enclosed TM 010 cavity was probed. Experimental results show that the physical length of a plasma is linearly related to the microwave power applied and that the profile of noise power spectra varies significantly along the length of a plasma.

An all optical fiber gas sensor of NH3 and CO based on based on the spectral absorption and harmonic detection

An all optical fiber gas sensor is presented to detect the concentration of NH3 and CO. Based on the spectral absorption, The wideband light source is used to reflect two narrowband spectra by fiber grating of different duty. and piezoelectric ceramics to obtain narrowband output light. The high sensitivity detection can be measured from the second harmonic signal. The two narrowband spectra are corresponding to the absorption spectra of NH3 and CO. Concentration detection are realized by the detection of variety of light intensity. Sensitivity is proved and cost is reduced.

Optical Humidity Sensor Based on Air Guided Photonic Crystal Fiber

We proposed a novel relative humidity （RH） sensor based on the air guided photonic crystal fiber （AGPCF） using the direct absorption spectroscopic method in this paper. The wavelength scanning around the water vapor absorption peak around 1368.59nm was realized by injecting the saw-tooth modulated current to a distributed-feedback laser diode. A reference signal was used as a zero absorption baseline and to help reduce the interference from the distributed-feedback laser source and probed region. The humidity level was determined by the normalized voltage difference between the reference signal and sensor signal at the peak of water vapor absorption. We demonstrated that a length of 5-cm AGPCF with a fixed small air gap between the single mode fiber （SMF） and hollow core fiber as an opening achieved a humidity detection resolution of around 0.2%RH over the range 0 to 90%RH which did not require the use of any hygroscopic coating material.

Effect of Ce_2O_3 on the 1.53 μm spectroscopic properties in Er^(3+)-doped tellurite glasses

Er3＋/Ce3＋ co-doped tellurite-based glasses with composition of TeO2-ZnO-Na2O are prepared by high- temperature melt-quenching technique. Effects of Ce2O3 content on the 1.53 μm band fluorescence spectra and fluorescence lifetime of Er3＋ are measured and investigated. It is found that the tellurite glass containing Ce203 with molar concentration of 0.25% exhibits an increment of 13% in 1.53 μm fluorescence intensity and an increment of 15% in the 4I13/2 level lifetime. The results indicate that the prepared tellurite-based glass with a suitable Er3＋/Ce3＋ codoping concentration is an excellent gain medium applied for broadband Er3＋-doped fiber amplifier （EDFA） pumped with a 980 nm laser diode.