High-power vertical cavity surface emitting lasers (VCSELs) are widely used in optical communication, optical storage, optical interconnection, sensing, and other fields. High-power VCSELs usually adopt a high-density array layout, and temperature is one of the key factors affecting their performance. In this work, the thermal characteristics of the VCSEL array with 1273 elements have been studied. A series of photoelectric characteristics such as the working voltage, output optical power, slope efficiency, electro-optical conversion efficiency, and spectrum of the device have been analyzed through a precision temperature control system. According to the relationship between the measured wavelength shift and the dissipated power, it is calculated that the thermal resistance value of the device increases from 1.319℃/W to 1.952℃/W, and the temperature rise of the active area is extracted. It can be seen that more temperature rises in the active region at higher ambient temperature for a given injection current, with a maximum value of 105.6℃. A thermo-electric coupling model was established to simulate the thermal distribution. The equivalent array method is employed to simplify the high-density array. The simulated results agree well with the measurement. As the ambient temperature rises, the thermal crosstalk phenomenon in the VCSEL array becomes more obvious. Heat diffusion becomes more difficult, resulting in more heat accumulation inside the device. The internal loss of the device is severe and the gain-cavity mode is seriously mismatched, so the photoelectric performance decays sharply. This research provides important guidance for the optimization and application of future devices.
In the field of laser engineering, various beam quality criterion has poor scalability, and the description of the laser spot is blurry. Most of the already published spot quality analyses focus on the uniformity of the laser spot, without considering the laser spot features. A generally applicable evaluation system has not been established. Follow standardization thinking, an ideal reference spot model was established, and an evaluation method of laser spot quality was proposed. With substituting simulation and experimental images into calculations, it is confirmed that this method can eliminate the interference from spot picture inherent attributes like the number of pixels, size, and luminance. This method makes the spots of various lasers measurable, especially be appropriate for evaluating semiconductor laser spot, multi-mode fiber spot where the beam quality is insufficient.
KEYWORDS: Vertical cavity surface emitting lasers, Mirrors, Reflectivity, Resonators, Resistance, Near field diffraction, Transmittance, Lithium, Light sources, High power lasers
For the past years, ArF immersion has been employed as the major lithography tool in the foundry manufacturing to fabricate the patterns of minimum pitch and size. However, for semiconductor scaling beyond N7 the application of EUV lithography is considered to be crucially important to overcome the physical limitation of ArF immersion and to realize even smaller patterns. In the case of ArF photo processes, the best mask size for a specific pitch could be selected with the consideration of optical performances such as NILS, MEEF, etc. In contrast, for the EUV processes the optical and resist stochastic effect should also be taken into account as an important factor in deciding the best mask size. In this paper, we are going to discuss the dose and mask size optimization process for an DRAM contact hole layer with EUV lithography utilizing stochastic simulations; this contains also the stochastic response of the resist. In order to calibrate a predictive stochastic resist model, which is required for this application, measurements of the stochastic resist response are necessary. In addition, the systematic and stochastic errors of CD-SEM measurements have to be estimated. We will compare experimentally obtained NILS and MEEF to simulated results, which are in very good agreement. Also, we show a comparison of experimental and computational analysis of LCDU (Local CD Uniformity).
The contrastive damage experiments of CCD irradiated by 800nm femtosecond laser with the pulse duration of 330fs
and 1064nm laser with the pulse duration of 10ns were studied from the energy density and power density. The failure
problems of the CCD devices irradiated by the two kinds of laser pulses were studied. The experimental results show
that the failure threshold of CCD irradiated by femtosecond laser is 2.3 nJ / cm2and it is 3~4 order lower than that by
nanosecond laser. According to the micro-analysis of CCD, it is found that the damage takes place at the light activated
elements.
KEYWORDS: Missiles, System integration, Control systems, Data acquisition, Software development, Telecommunications, Human-machine interfaces, Reliability, Data communications, Databases
Based on virtual instrument, software design precept of missile integrated test system is proposed in this paper. The integrated test system software was developed under modular, intelligent and structured precept. In this way, the expansion capability of the test software is improved, and it is very convenient for second-development and maintenance. This test software is of higher-degree automation, its integrated test environment gives full play to the hardware platform of the missile integrated test system. In response to the specific hardware configuration of the test system and special missile test requirements, the application of test resources was optimized in the test procedure to improve test speed greatly and satisfy the power-on time limit for missile test. At the same time, by applying multithreading and hardware clock on a data acquisition card, accurate data acquisition, data calculating and data injecting can be completed in a millisecond to satisfy the harsh missile test requirement. This automatic test equipment can automatically test the nose cabin and control cabin only of a missile and a training missile; all the missile test items can be accomplished in a short period of time to enhance the efficiency and reliability of the test.
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