Transmission of infrared laser radiation through silver-halideoptical fibers during repeated plastic deformation

The infrared transmission of polycrystalline mixed silver-halide optical fibers was studied during repeated mechanical plastic bending of the fibers. Plastic bending is useful for various applications, and is not shown by other available types of fibers. The lifetime (number of cycles to failure) of the fibers was measured and characterized both optically and mechanically. Optical failure lifetime depends on composition, going through a maximum at around AgCl_0.5Br_0.5 composition, whereas the lifetime to mechanical fracture is not very sensitive to composition. The behavior and measured values are discussed in terms of the low-cycle fatigue phenomenon     

Ultrafast deep UV Lithography with excimer lasers

The use of high-power pulsed excimer lasers for photolithography is described for the first time. Short exposure times, high resolution and absence of speckle are experimentally demonstrated. Using a XeCl laser at 308 nm and a KrF laser at 248 nm, excellent quality images are obtained by contact printing in two positive photoresists. Resolution down to 1000 line-pairs/mm is demonstrated. These images are comparable to state-of-the-art lithography done with conventional lamps; the major difference is that the excimer laser technique is ∼ 2 orders of magnitude faster. Preliminary results on reciprocity behavior in several resists are also presented.     

Modeling of Novolak-based positive photoresist exposed to KrFexcimer laser UV radiation at 248 nm

A model is presented for calculating the local exposure and the development rate for a Novolak-resin naphtoquinone-diazide sensitized photoresist exposed to a KrF excimer laser UV radiation at 248 nm. The measured transmission of the pulsed UV radiation through the resist is presented and compared to the simulated one using the model. Classical bleaching characteristics (i.e. the resist transmittance increases with the dose) are observed at low dose exposure with low energy per pulse. When the dose is increased, the photoresist transmittance reaches a maximum and starts to decrease. This behavior is assumed to be due to UV radiation effect on the resin. The model describes a general photoresist with absorbing components, each with two distinctive initial and postexposure states. The model is applied to the case of a Novolak-based photoresist where the two components are the photoactive compound and the resin     

Far-field radiation of optical fibers with tapered end

In this paper, an accurate model of the far-field radiation of a tapered optical fiber, which is widely used in communication optics and biomedical tomography, is presented. The authors first analyze the far field that is radiated from the normally cut fiber then extend the model to a fiber with a tapered end by considering the different phase contributions of the emitted rays. The proposed technique shows the effects of the cut with a view of obtaining a high efficiency both in coupling and radiation pattern characteristics.     

Submicron resolution deep UV photolithography

A vacuum contact printing technique was used to evaluate the resolution limits of deep UV photolithography with a 300±30 nm exposure band. For the first time, an array of 200 chip sites containing 0.5 ?m meander patterns 3 cm long was clearly resolved in AZ 2415 positive resist across 2 in diameter silicon wafers.     

Transversely excited waveguide HCN laser with UV preionization

In order to obtain high-power submillimeter-wave pulses, UV preionization was applied to the transverse discharges in HCN-laser gas mixtures. Homogeneous discharges were obtained at pressures up to 1 atm. An increase of laser output and working pressure was achieved for the 337-μm emission.     

紫外激光刻蚀氧化锆陶瓷初步研究

描述了KrF准分子激光对氧化锆陶瓷的微刻蚀实验,研究了脉冲刻蚀深度与脉冲数的关系(刻蚀速率),刻蚀的槽的形貌,并进行了刻蚀小孔的初步研究,得到直径为40μm,深度为25μm的微孔矩阵。为KrF激光对该材料的加工提供实验数据。     

环行染料激光器内腔倍频—窄带可调谐紫外辐射的产生

报告了把角调谐的a-LiIO_3晶体用于若丹明6G连续波环行染料激光器内腔倍频,产生295～301.5nm窄带可调谐紫外辐射,单频连续扫描30GHz以上,最大输出近100μW。     

Generation of second-harmonic UV radiation using a nonlinear substrate coated with a UV absorbing thin-film waveguide

Second-harmonic Cerenkov radiation in the nonlinear substrate has been observed using a thin-film waveguide that is absorbing at the second harmonic but transparent at the fundamental wavelength.     

Modulator of laser radiation

A new mechanical modulator of laser radiation is proposed. The working principle is based on the specific diffraction of coherent radiation by a deep reflection grating with rectangular profile. The modulator can be used in various wavelength ranges.     

Azide-phenolic resin photoresists for deep UV lithography

A photosensitive composition, consisting of an aromatic azide compound (3,3'-diazidodiphenyl sulfone) and a phenolic resin (poly(p-vinylphenol)), called MRS-1, has been prepared and evaluated as a negative deep UV resist for high resolution lithography. Solubility of MRS-1 in an aqueous alkaline developer decreases upon exposure to deep UV radiation. The alkaline developer removes the unexposed areas of MRS-1 by an etching-type development process. No swelling-induced pattern deformation occurs, and images of submicrometer resolution are obtained. The resist is approximately two orders of magnitude more sensitive than PMMA(polymethyl methacrylate). The exposure time of 5 s is sufficient for deep UV contact printing using a 500-W Xe-Hg lamp. The resistance to dry etching of MRS-1 is comparable to that of conventional positive photoresists based on phenolic resin.     

RF transmission over multimode fibers using VCSELs-comparing standard and high-bandwidth multimode fibers

Fiber-optic radio-frequency links have been assembled using oxide-confined vertical-cavity surface-emitting lasers (VCSELs) and multimode fibers. Links with single and multimode VCSELs and with standard and high-bandwidth fibers have been evaluated and compared in the frequency range of 0.1-10 GHz. The best results were obtained for links with a multimode VCSEL and a high-bandwidth fiber. For a 500-m-long link, a spurious free dynamic range of 104 dB/spl middot/Hz/sup 2/3/ at 2 GHz and 100 dB/spl middot/Hz/sup 2/3/ at 5 GHz were obtained while allowing for a VCSEL-fiber misalignment of /spl plusmn/12 /spl mu/m. Corresponding numbers for the intrinsic link gain and noise figure are -29 and -33 dB, and 39 and 42 dB at 2 and 5 GHz, respectively. Inferior performance was observed for the standard fiber link due to a larger variation in modal group velocities. This paper also presents a detailed link analysis to identify performance limitations and to suggest modifications for improved performance.     

The effect of higher radiation modes on frequency shifts of a laser standard comprising an external interferometer with a nonlinear absorber

The effect of higher radiation modes on the characteristics of a laser frequency reference with an external interferometer is considered. It is shown that, in the case of local laser-beam detection, higher modes can have a significant effect on the shift in the reference frequency through the pulling mechanism.     

Accelerated recording of negative index gratings in Ge-doped optical fibers using 248-nm 500-fs laser radiation

The fabrication of Bragg gratings in commercial B-Ge and high-Ge optical fibers using 248-nm 500-fs laser radiation is demonstrated. The underlying photosensitivity process is that of Type IIA, where negative index change gratings are recorded, following a nonmonotonic index change growth. Refractive index evolution curves for both average and modulated index changes are presented. Index changes of the order of 10/sup -3/ are obtained for the fibers exposed, under 2.4 kJ/cm/sup 2/ accumulated energy density. For comparative purposes grating exposures using 248-nm nanosecond excimer laser radiation are also appended. Thermal annealing studies performed revealed that Type IIA negative index gratings fabricated using femtosecond pulses exhibit enhanced thermal stability, enduring temperatures up to 650/spl deg/C.     

Rail to rail radiation hardened operational amplifier in standard CMOS technology with standard layout techniques

This work presents a rail-to-rail operational amplifier hardened by design against ionizing radiation at circuit level, using only standard layout techniques. Not changing transistor layout, for instance by using enclosed layout structures, allows design and simulation using the standard models provided by the foundry. The circuit was fabricated on a standard 0.35 μm CMOS process, and submitted to a total ionizing dose (TID) test campaign using a ⁶⁰Co radiation source, at a dose rate of 0.5 rad(Si)/s, reaching a final accumulated dose of 500 krad(Si). The circuit proved to be radiation tolerant for the tested accumulated dose. The design practices used to mitigate TID effects are presented and discussed in detail.     

紫外可调频准分子激光系统

报道一种结构简单的紫外可调频放电泵浦准分子激光系统,只用一个火花隙控制两台准分子激光器实现了振荡放大。在XeCl(中心波长308毫微米)谱区实现了调频输出,单脉冲能量11毫焦耳,带宽0.07毫微米,束散角约为0.2毫弧度。     

用等离子体电极产生紫外激光发射

我们研制了一种新颖的放电泵浦形式,即采用金属片间的放电产生等离子体即作为预电离又作为主放电电极。在N_2气中获得了均匀放电。 装置结构和电原理图如图1所示。金属片均采用1mm厚的钼片,制成锯齿形,每片长约1cm。两金属片放电间距为5mm。装配时,根据需要金属片数量可多可少,纵向金属片间距可密可疏。贮能电容C_0为64.8nF(2700pF×24)陶瓷电容器。每对金属片配一个电容量为780pF的小陶瓷电容器C_1。主放电电极间距为2cm。当球隙导通时,主贮能电容C_0放电,上电极和金属片间产生电压差,由于每对金属片配有一个电容器C_1,因此,在主放电回路导通之前,金属片之间首先放电对C_1充电。金属片的放电为主放电提供了良好的预电离条件,此时     

Gas breakdown with nanosecond CO2 laser radiation

The thresholds for CO₂ laser induced breakdown and their variation with pulse width have been measured at various pressures for Ar, N₂ and an 8/1/1 laser mixture of He/CO₂/N₂ using 3–40 ns duration pulses. These measurements indicate that excited state production plays a dominant role in determining the threshold for nanosecond duration pulses. This has been confirmed by the good agreement obtained between the measured and theoretical thresholds.