In high power laser systems, the stability of the seed laser is vitally important. This paper focuses on work undertaken to design and make a high stable LD pumped solid state seed laser which had the advantage of being all solid state, compact, easy to manufacture and low cost. The laser was composed of two parts. One part was a LD pumped 0.5 mm thick Nd:YLF laser system in which the instability was around +/- 6% (3(sigma) ). The other part was a close-looped laser power control system using external cavity power feedback. Using an electro-optic modulator, a 1 X 2 optical fiber splitter and a signal processing circuit, we successfully realized the high stable LD pumped Nd:YLF laser in which the instability of laser output power was lower than +/- 0.2%/hour (3(sigma) ). A digital PID control method was used in which the control frequency was 40 kHz. We obtained 3 mW of high stability laser power through the optical fiber.
This paper analyzes the reasons that the dust concentration can not be measured accurately by the present optical methods, and proposed a new optical technique which employs the principles of interference of light to measure the dust concentration. The laboratorial experiment shows the feasibility of the new method.
This paper describes a mixed fiber optical measuring system for the isolated phase busbar. As the magnetic field in the isolated phase busbar is only related to the busbar current, the current sensor, which makes up of the diamagnetic SF-6 glass with the thin-film polarizer and analyzer at both its ends, is placed inside the enclosed shell but outside the busbar, and the distance from the current sensor to the axis of the busbar depends upon the value of the current measured. The laboratorial experiment shows that the optical measuring system is reliable for using in the power system instead of the conventional current transformer.
Fluorescence properties of stomach tissues have been investigated to determine whether malignant specimens can be discriminated in vitro. Differences between normal and tumor tissues are found that concern both the intensity distribution and spectral shape of the autofluorescence emission. According to the distinctions tumor tissues would be differed from the normal tissues. The resulting spectra could be differentiate histologically stomach abnormal tissues from normal tissues with a sensitivity and specificity value of 90 percent and 92 percent. Furthermore, fluorescence spectra from human stomach normal and malignant tissues have been measured in real time in vivo.