Effect of DBR Geometry on Reflectivity and Spectral Linewidth of DBR Lasers

The linewidths of InGaAs-GaAs-AlGaAs DBR lasers with varied DBR dimensional parameters are measured and analyzed. These lasers were built with different DBR grating lengths and depths in order to explore the effect of the size of the DBR on its coupling coefficient and reflectivity,and hence on the linewidth of the laser diodes. The linewidths were measured by employing a self heterodyne linewidth measurement system. The experimental and calculated data for DBR reflectivity and spectral linewidth are given. The relationship between these data and the dimensions of the DBR is analyzed. Based on this analysis,the effect of the DBR geometry on the linewidth of the lasers is explored. The results give useful information related to the design and fabrication of such DBR lasers.

LC2024-03F新型载重斜交胎成型机(拉入法)应用

介绍新型斜交胎成型机的扩布器 (吹气式 )、拉布器的结构及应用。

Modified Holographic Exposure to Fabricate Varied Bragg Grating in an Identical Chip

A new fabricating method is demonstrated to realize two different Bragg gratings in an identical chip using traditional holographic exposure. Polyimide is used to protect one Bragg grating during the first period. The technical process of this method is as simple as that of standard holographic exposure.

Widely Tunable Sampled-Grating DBR Laser

The 3-section SG-DBR tunable laser is fabricate d using an ion implantation quantum-well intermixing process.The over 30nm discontinuous tuning range is achieved with the SMRS greater than 30dB.

Optimization for Top DBR’s Reflectivity in RCE Photodectector

The monolithic integration of vertical-cavity surface-emitting lasers (VCSEL) with photodetectors is very important in the application of free-space optical interconnects.Theoretical and experimental results on the resonant-cavity-enhanced (RCE) photodetector with VCSEL Structure are presented.The compatible requirement in input mirror reflectivity between the VCSEL and the RCE detector is achieved by precisely etching the top mirror.In this way,the RCE detector with relatively high quantum efficiency and necessary optical bandwidth has been obtained.[KH8/9D]

Novel hybrid optimal algorithm for broad-band Raman amplifier

A hybrid optimal algorithm, named the SAA-PA in brief, based on the simulated annealing algorithm （SAA） and the Powell algorithm （PA） is proposed. The proposed algorithm puts the random search strategy of the SAA into the PA, which can prevent optimizing courses from trapping in local optima. The SAA-PA can effectively solve multimodal optimization in the distributed multi-pump Raman amplifier （DMRA）. Optimal results show that, under the conditions of the on-off gain of 10 dB, the gain bandwidth of larger than 80 nm and the fiber length of 80 km, the gain ripple of less than 1.25 dB can be designed from the DMRA with only four backward pumps after the optimization of the proposed SAA-PA. Compared with the pure SAA, the SAA-PA can attain a lower gain ripple with the same number of pumps. Also, the relationship between the optimal signal bandwidth and the number of pumps can be simulated numerically with the SAA-PA.

Wet Oxidation of Al_x Ga_(1-x)As/GaAs Distributed Bragg Reflectors

The wet oxidation of AlGaAs with high Al content in a distributed Bragg reflectors （DBR） is studied by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Some voids distribute along the oxide/GaAs interfaces due to the stress induced by the wet oxidation of the AlGaAs layers. These voids decrease the shrinkage of the Al2O3 layers to 8% instead of the theoretical 20% when compared to the unoxidized AlGaAs layers. With the extension of oxidation time, the reactants are more completely transported to the front interface and the products are more completely transported out along the porous interfaces. As a result,the oxide quality is better.

Tunable Distributed Bragg Reflector Laser Fabricated by Bundle Integrated Guide

The tunable BIG RW distributed Bragg reflector lasers with two different coupling coefficient gratings are proposed and fabricated.The threshold current of the laser is 38mA and the output power is more than 8mW.The tunable range of the laser is 3 2nm and the side mode suppression ratio is more than 30dB.The variation of the output power within the tunable wavelength range is less than 0 3dB.

Counting wavelength demodulation of FBG sensors

Measuring amplitude of signal is the usual method in wavelength demodulation of fiber Bragg grating (FBG) sensors recently. This method is easy to be disturbed and has low precision. In this paper, a novel counting wavelength demodula- tion scheme of FBG sensors using a high birefringent fiber (HBF) loop mirror is reported. This demodulator has simple structure, high precision, cheap price and convenient use. The resolution of the loop mirror device with a HBF of 30 meters long is 0.067 nm. For a center wavelength of FBG of about 1550 nm and a 40 nm shift range of its reflection wavelength, the relative error of measurement is only ± 0.001. This wavelength demodulation device has significance for widespread application of FBG sensors.

Linewidth Narrowing and Intensity Enhancement of Wavelength Tunable MOLEDs

Microcavity structure consisting of distributed Bragg reflector and metal aluminum mirror is designed. Using tris (8-hydroxyquinoline) aluminum as electron-transport layer and emissive layer, and N, N′-bis (3-methylphenyl)-N, N′-diphenylbenzidine as a hole-transport layer, microcavity organic light-emitting diodes(MOLEDs) are fabricated. Compared to the electroluminescence spectra of non-cavity OLEDs, the linewidth of the MOLEDs is compressed from 75 nm to 7 nm, and the peak intensity enhances by a factor of about 3. When the effective length of the microcavity is modified, resonance wavelength can be selectively scanned over a very wide range of wavelengths that cover almost 140 nm.

Study of a high-temperature and high-pressure FBG sensor with Al_2O_3 thin-wall tube substrate

A fiber Bragg grating(FBG) high-temperature and high pressure sensor has been designed and fabricated by using the Al2O3 thin-wall tube as a substrate.The test results show that the sensor can withstand a pressure range of 0-45 MPa and a temperature range of -10-300 ℃,and has a pressure sensitivity of 0.0426 nm/MPa and a temperature sensitivity of 0.0112 nm /

A Novel Sensor for Detecting the Vibration

The micro-cantilever beam with a twin long period optic fiber grating sensitive to the strain and the vibration is designed to use as the sensor head.The micro-displacement of wavelength caused by strain or vibration is amplified in the system.Special cladding material is used to eliminate the interference brougth about the temperature.The designing structure is enabled to detect the micro-information.

An active temperature compensated fiber Bragg grating vibration sensor for high-temperature application

An active temperature compensated fiber Bragg grating(FBG)vibration sensor with a constant section cantilever beam is proposed for the simultaneous measurement of temperature and vibration,and the sensor is verified by a temperature compensation feedback system.The high-temperature vibration sensor is composed of a quartz cantilever beam and a femtosecond Bragg grating.The feedback control demodulation system of active temperature compensation can adjust the laser wavelength to stabilize the grating offset point and realize simultaneous measurement of temperature and vibration.On this basis,the performance of the sensor is tested and analyzed within the range of 20-400℃by setting up a high-temperature vibration test system.The experimental results show that the sensitivity of the sensor is about 132.33 mV/g,and the nonlinearity is about 3.33%.The sensitivity between the laser wavelength and temperature is about 0.01307 nm/℃.In addition,the active temperature compensated fiber Bragg grating vibration sensor has the advantages of a simple structure,stable performance,easy demodulation and high sensitivity.Moreover,the sensor can achieve high temperature vibration signal monitoring and has good practical application value.

Engineering approach to in-situ bridge health monitoring with fiber bragg gratings

In this presentation the feasibility and capability of fiber Bragg gratings （FBG） employed in bridge health monitoring are demonstrated on a real bridge. FBG＇ s wavelength shift depending on strain variance has been tested. The technique of FBG installation on bridges has been developed. 12 FBG strain sensors and 3 temperature sensors have been successfully embedded in the prestressed concrete box girder during the construction of Heilongjiang Hulan River Bridge. The prestressing tension process and quasi-static loading process of the girder were monitored with those sensors before it was installed onto the bridge. After the bridge was completed, the FBG sensors embedded have been utilized to monitor the strain shift of the beam under quasi-static load, traffic load and temperature. The results show that the traffic fluxes, possible tatigue damage and deflection of the bridge can be revealed conveniently through strain measurements with these FBG sensors, which provide key information for structural health diagnosis. The fact that the FBG strain sensors have withstood the ordeal of harsh construction process and lasted for more than one year proves that their durability and stability can satisfy the requirements for bridge health monitoring. It is also shown that the FBG strain sensor is more adaptive to long-term structural health monitoring than the electric resistance strain gauge.

Photoluminescence and X-ray Diffraction of Distributed Bragg Reflector

Spectral and structural characteristics of distributed Bragg reflector (DBR) in vertical-cavity surface-emitting lasers were studied with photoluminescence and double-crystal X-ray diffraction measurement.The expected high quality epitaxial DBR structure was verified.In the X-ray double-crystal rocking curves of DBR the zeroth-order peak,the first and second order satellite peaks were measured.Splitting of diffraction peak appeared in the rocking curves was analyzed.The effects of introduced deep energy levels on the structural perfection and optical properties were discussed.

Transmission Characteristics of Sagnac Loop with Fiber Bragg Grating

A transmission filter composed of a Sagnac loop and a fiber Bragg grating is studied in detail. It is found that the transmission spectrum of this filter is the splitting of the reflection spectrum of the fiber Bragg gratings. The filter can behave as a multiple-passband filter when the fiber Bragg grating is strong and as a single-band filter when the fiber Bragg grating is weak. Very narrow transmission filters can be Obtained in this way.

P-type AlAs/[GaAs/AlAs] Semiconductor/Superlattice DBR Grown by MBE

A p-type AlAs(70.2 nm)/16.5 period [GaAs(3 nm)/AlAs(0.7 nm)] semiconductor/superlatice distributed Bragg reflector (DBR) has been grown on n +-GaAs(100) substrate by V80H molecular beam epitaxy system. Experimental reflection spectrum shows that its central wavelength is 820 nm, with the peak reflectivity for 10-pair DBR of as high as 96 %, and the reflection bandwidth of as wide as 90 nm. We formed a 20×20 μm 2 square mesa to measure the series resistance using wet chemical etching. From the measurement result, the series resistance of about 50 Ω is obtained at a moderate doping (3×10 18 cm -3 ). Finally, the dependence of the resistance of the DBR on the temperature is analyzed. From the experimental result, it is found that the mechanism of the low series resistance of this kind of DBR may increase the tunneling current in the semiconductor/superlattice mirror structure, which will result in a decrease in series resistance.

Novel shape detection systems based on FBG sensor net for intelligent endoscope

This dissertation aims at providing steady sensing for the shape detection of colonoscopes. The research especially deals with the key techniques of fiber bragg grating (FBG) large curvature sensor and sensor net, integrates the techniques of mechatronics and computer graphics, and develops real time FBG shape sensing system and incremental shape sensing system for colonoscopies.

Application of fiber Bragg grating sensor network in aluminum reduction tank shell temperature monitoring

A fiber Bragg grating temperature sensor network was designed to implement the real-time health monitoring of the aluminum reduction cell. The heat transfer process was simulated using software ANSYS, and an on-line shell monitoring system was established based on optical sensing technology. According to aluminum reduction cell heat transfer theory, the 2D slice finite element model was developed. The relationship between shell temperature and cell status was discussed. Fiber Bragg grating （FBG） was chosen as the temperature sensor in light of its unique advantages. The accuracy of designed FBG temperature sensors exceeds 2 ~C, and good repeatability was exhibited. An interrogation system with 104 sensors based on VPG （volume phase grating） filter was established. Through the long-term monitoring on running state, the status of the aluminum reduction cell, including security and fatigue life could be acquired and estimated exactly. The obtained results provide the foundation for the production status monitoring and fault diagnosis. Long-term test results show good stability and repeatability which are compatible with electrolysis process.

Efficiency Improvement of 590 nm AIGalnP Light Emitting Diode with a Reflective Top Electrode

In this work, enhancement of the light extraction efficiency of a 590 nm AIGaInP light-emitting diodes （LED） with a reflective top electrode （RTE） was investigated. A distributed Bragg reflector （DBR）, consisting of AIAs/AIGaAs pairs, grown on an AlGaInP structure was used as a reflector for a reflective top electrode. It was found that a higher output power was observed from the AIGalnP LED with a RTE than from a conventional one. In addition, it was noted that the improvement in the output power depends strongly on the reflectivity of the reflector and that it exhibits a more effective performance with low injection currents. The increase in the optical output power was attributed to the enhanced extraction efficiency caused by a reduction of light absorbed from the emission region to top electrode through the RTE.