In this paper we report that the electro-absorption modulators can also enable long haul and ultra-long haul transmission in the wavelength-division multiplexed fiber optic networks, with potentially much smaller equipment size and at much lower cost. The error-free transmission distance can be as long as 2,000 km using standard single-mode fiber for both non-return-to-zero and return-to-zero data formats, and can be even longer with forward-error correction technology. Sufficient optical signal-to-noise ratios are maintained and wide-open eye diagrams are observed. No significant path penalties attributable to chirp are observed. A low cost return-to-zero transmitter, simple in architecture and small in physical size, is demonstrated by using only one electro-absorption modulator. These results indicate the maturity, particularly the chirp manageability, of the electro-absorption modulator technology for metro and long haul as well as ultra-long haul applications. Therefore, large-scale opto-electronics integration in wavelength-division multiplexing equipment becomes a promising reality.
The vacuum spark is an excellent source of pulsed X-rays (also called flash X-rays) suitable for high speed photography. In the vacuum spark concept a capacitor is discharged through two properly shaped electrodes, made of selected materials, in a vacuum. This high current (over 1 kA) discharge produces intense pulsed hard X-rays with a pulse width of about 10 ns (FWHM, Full Width at Half Maximum). The measured source size by pinhole photography is smaller than 0.5 mm. Efforts have been made to reduced the total inductance (below 200 nH) and to use a relatively small capacitor (just a few nF), so as to increase the X-ray intensity. A vacuum spark X-ray source (VSX I) has been under routine operation at ALFT and has logged over 1,200 shots during X-ray tests carried out with Los Alamos National Laboratory. The radiation head was designed and built by ALFT and the remaining components are all commercial, off-the-shelf products. An external signal of 10 V, 1 ns rise time and 500 ns width triggers the machine at rep-rates up to 10 Hz, and higher rep-rate operation of the vacuum spark is being studied at ALFT.
Spherical pinch and vacuum spark have been pursued by Advanced Laser and Fusion Technology, Inc. for a number of years as candidates for point radiation source needed in microlithography. In the spherical pinch electrical energy is used to generate spherical imploding shock waves that compress a performed plasma into small (diameter < 1.0 mm) radiation source. The temperature of the central plasma can be high enough for emission of broadband radiation from the UV to the soft X-ray region of the spectrum. In the vacuum spark a small capacitor (a few nF) is discharged through two properly shaped electrodes in a vacuum. During the discharge 'hot spots' (minute high temperature plasmas) are formed in the vicinity of the anode and intense pulsed soft X-rays can be generated around the characteristic lines of the electrode materials. High rep-rate operation of the vacuum spark is necessary to provide sufficient dosage for microlithography.
In this paper we describe the performances of two kinds of high-flux radiation sources that have been developed at Advanced Laser and Fusion Technology, Inc. The first kind is the spherical pinch which exploits the principle of spherical convergence of strong shock waves in noble gases to generate a hot plasma at the center of a spherical vessel. The temperature of the central plasma can be high enough for emission of broadband radiations from the UV to the soft X-ray region of the spectrum. The second kind is the vacuum spark in which a capacitor is discharged through two properly shaped electrodes in a high vacuum. During the discharge minute spots of hot plasmas are formed on or around the electrodes and strong line radiation (characteristic of the electrode materials) can be generated in the soft X-ray region. High repetition rate operation of the vacuum spark may lead to the dosage required by the submicron lithography technology.
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