Papers by Keyword: Laser Diode

Abstract: In this paper, the far field of GaN based laser diode is discussed by using numerical simulation method. Results show that, the divergence angle θ_⊥ of far field increased with the thickness of the waveguide layer as exponential decay and the divergence angle θ_// of far field increased with the thickness of the waveguide layer. The aspect ratio of far field distribution increased with increasing the thickness of the waveguide layer as exponential decay.

Abstract: Thermoelectric couple was employed in traditional airplane engine temperature measurement system with the disadvantages of large size,heavy weight,big error and slow response.This paper presents a new kind of real—time temperature measurement system using laser diode InGaAs/I as light source,and using pyroelectric detector LiTa03 as optical receiving unit and using a microprocessor as signal processing center.This instrument consists of three parts:optical emitting and receiving system,signal amplifying and controlling system,and display system。The principle and structure of the system are introduced.Experimental results of airplane engine real—time temperature measurement show that temperature measurement accuracy and response time conform to our requirement in the range of 300°C一800°Cand agree with prediction of theory.All these prove that the design is correct.

Abstract: Laser Diode (LD) tester is widely used in the research, manufacturing and testing of laser diode, but no verification regulation or calibration specification for laser diode tester has been released until now. With the fully using of the standard instruments in our optical communication laboratory, and referring to the operational manual, specification and relevant calibration regulations, we provide approaches to the calibration of the laser diode tester. The evaluation processes and results of measurement uncertainty for optical power measurement, output DC current, and DC voltage measurement are delivered at the end of the paper.

Abstract: The light inspection on surface finishing of most product measurement is an important feature in the industries. In this study, a lab module tester for examination on the different type quality of tissue paper quality was done. The light reflectance element was used in this study to differentiate the quality of tissue paper. The laser diode and photodiode was used as manipulator to differentiate the tissue paper and photo detector to detect the reflected light from the surface of tissue paper. The both of laser diode and photodiode were placed in a light box. Different level of intensity reflected from the surface material will have different voltage output. The result showed that the total ply high quality tissue paper has a higher reflected voltage output compared to low quality tissue paper.

Abstract: Retracted paper: The conventional material for the optical fiber communication laser diode is based on InGaAsP, which might be substituted by a potential candidate, InGaAlN. The new active region material, InN, is introduced regarding to its crystal growth and characterization, including the structural, optical and electrical properties. This material is promising for providing good performance of temperature stability of the wavelength. In addition, it is environmentally friendly.

Abstract: Laser cleaning is a non-contact, green and environmental cleaning method, which can effectively remove particulate contaminations of sizes as small as 0.1 μm without damage to the optics. But most laser cleaning devices are large and heavy, also expensive due to using large lasers such as CO2 laser, YAG Laser etc. In this work a low power LD was tried to clean fingerprint and dust contaminated on the surface of the attenuator glasses plates. In the laser cleaning experiment with low power diode the fingerprint grease can be efficient to be cleaned, but there is no evident effect for cleaning inorganic dust. The cleaning different degree of fingerprint contaminations was investigated at the variable laser parameters, including laser power and irradiation time. An optical microscope was used to analyze the cleaning effect. The results show that low power LD can effectively remove the fingerprint on the surface of absorptive-type attenuator glass plates. On the premise that the attenuator optics glasses are not damaged, the cleaning area increases with the increase of radiation time and laser power. The cleaning area doesn't change much with the variation of laser frequency when the other parameters are the same.

Abstract: This paper presents a measurement system for 3-D micro structure using an optical fiber probe equipped with a piezo element generating vibration. The optical fiber probe consists of a stylus shaft with a diameter of 3 µm and a glass ball with a diameter of 5 µm attached to the tip. The stylus is set so as to circularly move in a plane. The measurement principle involves the monitoring of the vibrational amplitude of the stylus to prevent adhesion of the stylus tip to the measured surface due to the surface force, and this amplitude is measured optically. In this research, the stylus characteristics are examined. The effects of the relative humidity and the surface roughness on the surface force are then evaluated. As a result, it is shown that the surface force increases remarkably when the relative humidity is greater than 40%, and there is no adhesion of the stylus tip to the measured surface due to the surface force in case of the stylus vibrational amplitude of over 0.5 µm. Also, the adhesion of the stylus tip cannot be observed in the 0.2 - 0.8 µm surface roughness range.

Abstract: This paper focuses on the optical mode analysis of laser diodes to improve light emission. Under the mode analysis, we compare the optical confinement factor (OCF) percentage of the emitting light from the LDs. There are two structures which we analyze: a basic GaN waveguide structure and an InGaN waveguide structure. The second structure has additional InGaN waveguides and is analyzed under two additional design variations: the concentration of Indium and the thickness of the top waveguide layer. The results of this study indicate introducing InGaN waveguide layers correlates with lower order modes (zero and first order) and increase the OCF values. The top InGaN waveguide layer, which has a higher concentration of Indium, appears to increase the OCF. However, the increased thickness of the InGaN layer causes the lower modes’ OFC to decrease. Over all, in the best case, InGaN LD has an OCF of 1.8896%, which is about a 312% improvement compared to that of GaN LD ( OCF=0.4535%).

Abstract: By analyzing of thermoelectric cooler(TEC) working characteristics and using one-dimensional heat transfer equation, mathematical relationship between TEC working power and radiator equivalent thermal conductivity is derived. Temperature control efficiency could be improved by increasing equivalent thermal conductivity was proved. So that an optimization method using finned tubular radiator in LD temperature controller was presented, including theoretical foundation of radiator selection and system structure. Compared with normal radiator, the stable-time of the LD temperature controller using finned tubular reduces 50%, and stable-error reduces 60%, which was proved by mathematical calculation and experimental result of 2W LD system. Compared with forced air cooling and forced water cooling, the system has property of low vibration disturbance and simple structure. It followed that the finned tubular radiator was suitable for temperature control of medium and small power LD, which can improve temperature control efficiency and optimize the system.

Abstract: A circuit using the singlechip as key component for temperature control for DFB laser diode is designed in this article. An imbalance electrical bridge for measuring the temperature of laser diode is used in this circuit, and the result of measurement is converted to digital quantity by ADC. After that, the error signal is gotten through the digital PID calculation. At last, the DAC chip make error signal be voltage to drive power amplifier for TEC. The function of set point and display of real time temperature is also added. After the test for a long time, we confirm the precision of temperature is better than ±0.001°C.