High-power ytterbium-doped fibre master-oscillator power-amplifier at 1018 nm

A high-power master-oscillator power-amplifier (MOPA) at 1018 nm employing ytterbium (Yb)-doped fibres as a gain medium is reported. Utilizing a diffraction grating as a reflector, we could successfully suppress the influence of the broadband amplified spontaneous emission on the master-oscillator or the power-amplifier, resulting in stable amplification of the laser signal at 1018 nm. Based on a simple theoretical simulation on gain spectra and experimental investigation on parasitic lasing thresholds, the Yb fibre MOPA constructed in-house yielded 220 W of output at 1018 nm with a beam propagation factor (M2) of 1.1. The prospects for further power scaling are considered.

Creative Approaches for Thermal Hot Spot Identification on Analog IC

With the increase in the complexity of semiconductor wafer fabrication processes, the timing in responding and discovering the failure mechanism to a product failure at the initial product development stage or at the end of production line becomes a crucial factor. Effectively utilization the fault localization technique such as Photon Emission Microscopy (PEM), Laser Signal Injection Microscopy (LSIM) and Thermal Hotspot Localization (THS) may be significantly shortened the cycle time in the fault localization process. This paper will illustrate the creative approaches for thermal hot spot identification using modulated THS technique coupled with modified external electrical connection.

Influence of Fiber Properties on Harmonic and Intermodulation Distortions of Semiconductor Lasers

This paper introduces modeling and simulation of the harmonic and intermodulation distortions of semiconductor laser radiating an optical fiber link. The study is based on the rate equation model of semiconductor lasers excited by injection current with two sinusoidal tones separated by a radio frequency. The modulated laser signal is modeled in both the time and frequency domains. The laser signal distortions include the 2nd and 3rd harmonic distortion (2HD and 3HD), and the third-order intermodulation distortion IMD3. The laser is assumed to be modulated around its relaxation frequency. Influence of the modulation depth on the signal distortion is investigated when the laser is free running and when it is radiating a fiber link. In the latter case, influences of the attenuation and chromatic dispersion on the signal dispersion are elucidated when the fiber length increases up to 10 km. The results show that the fiber attenuation does not affect the signal distortion, whereas the chromatic dispersion affects both the harmonic distortions and intermodulation distortion. Sending the laser signal down an optical fiber of length ~ 5km can help in minimizing 2HD which is the dominant harmonic distortion of the modulated signal. This range of optical fiber is also characterized with intermodulation distortion less than 0dBc.

In-SEM Fault Isolation Using Voltage Contrast, EBIC/EBAC and Resistive Contrast Imaging

With the ever shrinking semiconductor device features coupled with the increasing circuit density, optical level fault localization techniques such as Photon Emission Microscopy (PEM), Laser Signal Injection Microscopy (LSIM) and Thermal Hotspot Localization (THS) can only get you so far due to these limitations: magnification, spot size and drop in detection sensitive at higher magnification. Using a 100x objective can put you in the ball park. Test data such as ATE & ATPG can point you to a specific block of circuitry but still far from defect localization. With in-SEM fault isolation and localization techniques such as Voltage Contrast (VC), Electron Beam Induced/Absorb Current (EBIC/EBAC) and Resistive Contrast Imaging (RCI), the nano-scale defect can be further localized due to the advantage of the magnification and spot size. This paper offers the combined techniques of optical level fault localization (PEM, LSIM & THS) and in- SEM or E-beam techniques (VC, EBAC, RCI) to successfully perform fault localization when challenged with the above scenarios.

Impact Analysis of the Atmosphere Optical State on Wind Lidar Sounding Range

One of the most important questions for correlation lidars is the sounding range question.Correlation lidar sounding range greatly depends not only on the parameters of the equipment, but also on the optical state of the earth's atmosphere.In addition, there are currently two approaches to the estimation of lidar sounding range. In one approach, an estimate of the sounding range is obtained by equating the detector threshold power to the laser signal power recorded by the detector. In another approach, an estimate of the sounding range is obtained by equating the minimum detectable energy of the detected laser signal energy.This paper is about impact research of the atmosphere optical state on wind correlation lidar sounding range and compare sounding range estimates obtained under the two different approaches to the energy calculation lidar.The analysis is carried out for the surface layer of the atmosphere, the horizontal sounding path and the radiation wavelength of 0.532 μm. In atmospheric haze conditions, an empirical formula is used for the attenuation factor. The signal-to-noise ratio is assumed to be 100.Solid-state Nd:YAG Ekspla lasers NL319 (lamp pumping, pulse energy 5 J) and NL231-100 (diode pumping, pulse energy 90 mJ) were chosen as radiation sources.Hamamatsu photomultiplier tube R5070A with radiant sensitivity ~ 50 mA/W was chosen as a detector.It is shown that in a wide optical state range (meteorological range of visibility from 20 to 2 km) the lamp-pumped laser source sounding range with pulse energy 5 J varies from ~ 3,8 km to ~ 1,2 km and the diode-pumped laser source sounding range with pulse energy 90 mJ varies from ~ 1,1 km to ~ 0,64 km.The approach based on comparison of the detector threshold power with the received laser signal power overestimates the sounding range due to incomplete influencing consideration factors.

Atom-molecule conversion with quantum manipulations

In this paper, we investigate quantum manipulations in an open atom-molecule conversion system. Through the transformation for the basis of the system, a set of time-dependent equations are derived under mean field approximation. We find that transitions between different dynamic areas of the system can be realized through manipulating an external rotating magnetic field, which corresponds to the tunneling rate in the equation. Through investigating the phase space of the system, we design an efficient method to combine pure cold molecule and pure molecular state so that it can be reached with much shorter time. Furthermore, manipulation of laser signal modulation, external diving and the distance-selective diffusion are also discussed in this paper.

Knitting needle fault detection system for hosiery machine based on laser detection and machine vision

The knitting needle cylinder is one of the core parts of a hosiery machine. The operation of its needles can directly affect the production quality and efficiency of the hosiery machine. To reduce the production loss of a hosiery machine caused by knitting needle faults, a knitting needle fault detection system for hosiery machines based on a synergistic combination of laser detection and machine vision is proposed in this paper. When the system was operating normally, a photoelectric detector collected the laser signal reflected by the knitting needle and the system monitored the operation of the knitting needle using the ratio of adjacent peak-to-peak distances of the signals. When a fault signal was detected, the hosiery machine was stopped by the system immediately, and a charge-coupled device camera was used to take an image of the faulty knitting needle. After image preprocessing, the faulty knitting needle could be identified quickly and accurately using an image region size classifier based on a decision tree. The experimental results showed that a single image classification by the classifier could be performed in as little as 0.002 s.