Yasuo Furukawa

Polarization and frequency control of a semiconductor laser with a new external cavity structure

A technique using a new external cavity structure to cause degeneration at the frequencies of two orthogonally polarized modes and to control the polarization and the frequency in a semiconductor laser has been devised. The phase difference between the polarizations in the gain medium can be canceled in a round trip through quarter‐wave plates set in the cavity. By rotating one of the quarter‐wave plates, orthogonally polarized laser beams can theoretically be made to oscillate at slightly different frequencies. Experimentally, two orthogonally polarized oscillations with rather large frequency differences occurred. The difference between the two frequencies alternated according to the quarter‐wave plate rotation. This phenomenon could be explained theoretically.

Quantitative Voltage Measurement By A Software Closed Loop Technique In Electron Beam Testing

A software closed loop technique was devised for quantitative voltage measurement in electron beam testing for LSIs. A retarding voltage of an energy analyzer is controlled iteratively by a computer to reduce difference between a slice level and a secondary electron signal to zero. The voltage is determined by the retarding voltage at the cross point of the slice level and the energy distribution curve. Using this technique, the waveform of 256 sampling phases with more than 5 V amplitude can be measured in about 30 s with 200 mV voltage resolution and 100 ps time resolution.

Current stability of single‐crystal and sintered LaB6 cathodes

The specimen current stability of single‐crystal and of sintered LaB6 cathodes are compared from the viewpoint of their dependence on the cathode tip temperature and the vacuum pressure. The specimen current of the single‐crystal LaB6 cathode is very stable during degradation of the vacuum in the gun chamber, while in the sintered LaB6 cathode it becomes very unstable in poor vacuum even though the total emission current is stable. The cause of this remarkable difference between the single‐crystal and sintered LaB6 cathodes is discussed.

Hologram Writer Using a Plasma Display Panel

A hologram writer for a read-only page-oriented hologram memory has been developed. Data masks are produced by photographing dot patterns of a plasma display panel on a long-size film. A data pattern is obtained by covering a fixed bit mask with each data mask and stored in a small hologram. A hologram memory plate with total capacity of 2 x 10(7) bits was prepared by this hologram writer. This paper describes the construction and features of this hologram writer, as well as the characteristics of the hologram memory plate produced on a trial basis.

An automatic adjustment system for the optical head of a magnetooptical disk drive

The authors developed a fully automatic adjustment system for mass production of the optical head for magnetooptical disk drives. The optical head is composed of small-sized (millimeter-scale) optical components, such as the laser diode, the collimator lens, the object lens, various prisms, and various detectors. In the assembly of the head, the positioning and fixation must be executed with an accuracy on the micrometer order, and the adjustment process is indispensable. Adjustment is a process where the object is iteratively measured and manipulated, and is finally fixed so that the specified performance is realized. A lens, for example, is moved, the shape of the convergence beam is observed, and the lens is then moved and fixed so that the beam takes the specified shape. Such an adjustment requires a considerable amount of time by an experienced worker, and has been one of the bottlenecks in the mass production of optical heads. The adjustment process for the optical head consists of adjustment of the optical axis of the laser diode, adjustment of the beam shape, and adjustment of the servo signal. The authors devised a series of adjustment algorithms composed of measurement, recognition, calculation of manipulation, execution of manipulation, verification, and fixation. They then developed the necessary techniques and installations that realize the algorithms. The key in the adjustment of the optical head is to process the measured value, to recognize the shape of the beam and the waveform, and to determine the manipulation, rather than simply using the measured value itself. Using the developed automatic adjustment system, the adjustment process, which requires approximately 9 minutes for an experienced worker, can be completed in about 6 minutes.

Production Efficiency And Intensity Distribution Of Pd X-Ray Source For Lithography

A technique to evaluate the X-ray intensity distribution on the wafer in an X-ray lithography system equipped with a conventional X-ray source with a Pd target was devised. A practical formula for the Pd L X-ray production efficiency, including parameters such as the incident electron beam energy, its incident angle, and the X-ray take-off angle was derived to develop a method of simulating the X-ray intensity distribution on the wafer. This simulation includes realistic factors such as the target shape, the profile and direction of the electron beam, and the X-ray absorption by the window and mask membrane. A good agreement between the calculated and the measured X-ray intensity distributions obtained in the application of this technique to a cone shaped target verified the usefulness of the technique in the design of Pd X-ray sources.