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1.
We report our transport studies in quasi-one-dimensional (1D) conductors-helical polyacetylene fibers doped with iodine-and the data analysis for other polymer single fibers and tubes. We found that at 30 K相似文献   

2.
Stepanov S  Cota FP 《Optics letters》2007,32(17):2532-2534
We report results of transient two-wave mixing (TWM) in Er-doped fibers with saturable absorption in a linear configuration of an adaptive interferometric vibrometer with essentially different powers of recording waves. The TWM signal modulation depth detected in the weak (reflected) wave was shown to be twice as strong as in the symmetric configuration with equal recording powers. In accordance with theoretical predictions, the experimentally observed TWM signal amplitude grew continuously with the fiber optical density in the whole investigated range of alpha(0)L approximately 0.2-4. At the recording wavelength 1492 nm it proved to be quite close to the theoretical limit of approximately alpha(0)L/2 for weakly absorbing fibers, and in 1-m-long fiber of high optical density reached maximal value of approximately 0.8. The TWM response time went down with the recording light power and for P(0) approximately 10 mW was in the submillisecond region.  相似文献   

3.
We have demonstrated Raman small-core As-Se fiber. More than 20-dB of gain was observed in a 1.1-m length of fiber pumped by a nanosecond pulse of approximately 10.8-W peak power at 1.50 microm. The peak of the Raman gain occurred at a shift of approximately 240 cm(-1). The Raman gain coefficient is estimated to be approximately 2.3 x 10(-11) m/W, which is more than 300 times greater than that of silica. The large Raman gain coefficient coupled with the large IR transparency window of these fibers shows promise for development of As-Se Raman fiber lasers and amplifiers in the near-, mid-, and long-IR spectral regions.  相似文献   

4.
Delivery of high peak-power femtosecond pulses with fibers is constrained by nonlinear distortions accumulated during pulse propagation. We address this problem with a novel, to our knowledge, fiber schematic, where the pulse propagates in a small Aeff (18 microm2) but highly dispersive (record value of approximately -900 ps/nm km) medium, enabled by transmission in the LP02 mode of a few-mode fiber. The novel fiber yields a low dispersion-to-nonlinear-length ratio (due to its large dispersion) despite its small Aeff, hence enabling mitigation of nonlinearities. This enables fiber delivery of distortion-free <150 fs, approximately 1 nJ, and 840 nm pulses--an order-of-magnitude improvement over single-mode fibers of similar Aeff.  相似文献   

5.
We present experimental results of two-wave mixing in single-mode Er-doped optical fibers for which dynamic Bragg reflectance gratings are formed as a result of saturation of fiber-optic absorption (i.e., by means of the effect of spatial hole burning). The gratings are probed by the same recording waves at lambda approximately = 1549 nm and are detected as periodic changes of the intensity of light reflected from a Sagnac interferometer (with a piece of the doped fiber included) observed when periodic phase modulation is induced in one of the waves. Both rectangular and sinusoidal modulation were used, which permitted evaluation of the grating recording time (tau(g) approximately = 3 ms for OFS-Fitel EDF-HG980 fiber) and the grating amplitude, which proved to be approximately 6-7 times lower than expected from measurements of saturation of fiber-optic absorption by one wave only.  相似文献   

6.
Dasgupta S  Pal BP  Shenoy MR 《Optics letters》2005,30(15):1917-1919
We report a novel idea for achieving highly efficient dispersion-compensating Bragg fiber by exploiting a modified quarter-wave stack condition. Our Bragg fiber yielded an average dispersion of approximately -1800 ps/(nm km) across the C band for the fundamental TE mode and an ultrahigh figure of merit of approximately 180,000 ps/(nm dB), which is at least 2 orders of magnitude higher than that of conventional dispersion-compensating fibers. The proposed methodology could be adopted for the design of a dispersion compensator across any desired wavelength range.  相似文献   

7.
Stepanov S  Hernández E 《Optics letters》2005,30(15):1926-1928
The influence of spatial migration of excitation among neighboring Er3+ ions on the dynamics of population grating formation in Er-doped optical fibers is reported. The effect manifests itself in an additional increment in the grating formation rate compared with the fluorescence growth rate observed for the same spatially uniform average light power. The experiments, performed at lambda=1549 nm in the configuration of transient two-wave mixing with two similar single-mode Er-doped fibers with significantly different erbium concentrations (approximately 640 and approximately 5600 parts in 10(6)), demonstrated the essential contribution of this effect to the grating formation rate in the latter fiber. The evaluated diffusion coefficient proved to be approximately 2.3 x 10(-9) cm2/s, which ensures effective migration of the excitation by approximately 48 nm, i.e., by approximately 18 average inter-ion distances in this fiber.  相似文献   

8.
Miao H  Weiner AM  Mirkin L  Miller PJ 《Optics letters》2007,32(16):2360-2362
We demonstrate wideband all-order polarization mode dispersion (PMD) compensation by applying high-speed spectral polarization sensing and ultrafast pulse shaping techniques to characterize and correct the frequency-dependent Jones matrix associated with PMD of optical fibers on a wavelength-by-wavelength basis. We report full compensation of approximately 800 fs pulses distorted to more than 10 ps by a PMD module with approximately 5.5 ps mean differential group delay. The sensing and compensation of Jones matrix take approximately 200 and approximately 500 ms, respectively.  相似文献   

9.
Ding Z  Meng Z  Yao XS  Chen X  Liu T  Qin M 《Optics letters》2011,36(11):2173-2175
We present a method to accurately measure the group birefringence variation with temperature in high-birefringence polarization-maintaining (PM) fibers using a distributed polarization analyzer. By analyzing polarization cross-talk peaks purposely induced at both ends of a PM fiber, the temperature coefficient of group birefringence can be accurately obtained. We confirm the theoretical prediction that the group birefringence of PANDA and TIGER PM fibers decrease linearly with temperature from -40 °C to 80 °C, and find that the temperature coefficients are -5.93 × 10(-7) °C(-1) and -5.29 × 10(-7) °C(-1) for two types of PANDA fibers, and -5.36 × 10(-7) °C(-1) for a TIGER fiber.  相似文献   

10.
Yatsenko Y  Mavritsky A 《Optics letters》2007,32(22):3257-3259
Concentration dependence of nonlinear refractive index n2 in fibers heavily doped with GeO2 is studied by using the D-scan method. Good agreement with an empirical dependence established earlier with lower GeO2 concentrations by the cw dual-frequency beat signal technique is shown for GeO2 concentrations up to approximately 100 mol.%. The highest values of the nonlinear coefficient gamma at 1.25 microm of 47.9, 57.7, and 70.9 W(-1) km(-1) were obtained in fibers doped with 67, 75, and 97 mol.% GeO2, respectively.  相似文献   

11.
We report what is to our knowledge the first delivery of nanosecond laser pulses through flexible fibers to produce optical sparks in atmospheric-pressure gases. Our work employs a Nd:YAG laser beam (1.064 microm) delivered through a cyclic olefin polymer-coated silver hollow fiber. We studied the beam properties at the fiber exit as a function of the fiber launch geometry. We found that for a low-angle launch (approximately 0.01 rad half-angle), the exit beam has relatively high optical intensity (approximately 2 GW/cm2) and low light divergence (approximately 0.01 rad half-angle) and allows downstream spark formation. The effect of fiber bending on the exit beam and on the ability to make sparks is also investigated.  相似文献   

12.
Fluorescence microscopy (FM) has recently been applied to the detection of airborne asbestos fibers that can cause asbestosis, mesothelioma and lung cancer. In our previous studies, we discovered that the E. coli protein DksA specifically binds to the most commonly used type of asbestos, chrysotile. We also demonstrated that fluorescent-labeled DksA enabled far more specific and sensitive detection of airborne asbestos fibers than conventional phase contrast microscopy (PCM). However, the actual diameter of the thinnest asbestos fibers visualized under the FM platform was unclear, as their dimensions were below the resolution of optical microscopy. Here, we used correlative microscopy (scanning electron microscopy [SEM] in combination with FM) to measure the actual diameters of asbestos fibers visualized under the FM platform with fluorescent-labeled DksA as a probe. Our analysis revealed that FM offers sufficient sensitivity to detect chrysotile fibrils as thin as 30–35 nm. We therefore conclude that as an analytical method, FM has the potential to detect all countable asbestos fibers in air samples, thus approaching the sensitivity of SEM. By visualizing thin asbestos fibers at approximately tenfold lower magnifications, FM enables markedly more rapid counting of fibers than SEM. Thus, fluorescence microscopy represents an advanced analytical tool for asbestos detection and monitoring.  相似文献   

13.
A mid-infrared supercontinuum (SC) is generated in ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF...) fluoride fibers from amplified nanosecond laser diode pulses with a continuous spectrum from approximately 0.8 microm to beyond 4.5 microm. The SC has an average power of approximately 23 mW, a pump-to-SC power conversion efficiency exceeding 50%, and a spectral power density of approximately -20 dBm/nm over a large fraction of the spectrum. The SC generation is initiated by the breakup of nanosecond laser diode pulses into femtosecond pulses through modulation instability, and the spectrum is then broadened primarily through fiber nonlinearities in approximately 2-7 m lengths of ZBLAN fiber. The SC long-wavelength edge is consistent with the intrinsic ZBLAN material absorption.  相似文献   

14.
Qi B  Tausz A  Qian L  Lo HK 《Optics letters》2005,30(24):3287-3289
We propose and experimentally demonstrate a single-mode fiber length and dispersion measurement system based on what we believe to be a novel frequency-shifted asymmetric Sagnac interferometer incorporating an acousto-optic modulator (AOM). By sweeping the driving frequency of the AOM, which is asymmetrically placed in the Sagnac loop, the optical length of the fiber can be determined by measuring the corresponding variation in the phase delay between the two counterpropagating light beams. Combined with a high-resolution data processing algorithm, this system yields a dynamic range from a few centimeters to 60 km (limited by our availability of long fibers) with a resolution of approximately 1 part per million for long fibers.  相似文献   

15.
Han YG  Song S  Kim GH  Lee K  Lee SB  Lee JH  Jeong CH  Oh CH  Kang HJ 《Optics letters》2007,32(15):2245-2247
We propose and experimentally demonstrate a simple and flexible scheme for the simultaneous measurement of strain and temperature using long-period fiber gratings (LPFGs) based on versatile holey fibers (HFs) with different air-hole sizes. The strongly resonant LPFGs (as much as approximately 24 dB) can be successfully achieved. The LPFGs inscribed in the HFs have similar temperature sensitivities regardless of air-hole size because of the same material composition. The strain sensitivities of the LPFGs, however, are different, since holey fibers have different cross-sectional areas depending on the air-hole size. The strain sensitivities of the HF-based LPFGs are enhanced by a factor larger than 2 as the air-hole size increases.  相似文献   

16.
We design and model a highly compact and tunable optical add-drop multiplexer (OADM) device that consists of long-period gratings and piezoelectric ceramic fiber stretchers. The proposed OADM shows that 50 dense wavelength-division multiplexing channel signals can be selected in the wavelength range from 1526.25 to 1563.75 nm with 0.75-nm channel spacing, which covers the whole C-band gain spectrum of an erbium-doped fiber amplifier. The cross talk between channels is less than -39 dB, and the total insertion loss of the device is approximately 0.24 dB, which includes the splicing losses, the mode mismatching loss, and the expected losses in the two side-by-side coupled fibers.  相似文献   

17.
Membrane tubes (spicules) arise in cells, or artificial membranes, in the nonlinear deformation regime due to, e.g., the growth of microtubules, actin filaments, or sickle hemoglobin fibers towards a membrane. We calculate the axial force f exerted by the tube, and its average radius, taking into account steric interactions between the fluctuating membrane and the enclosed rod. We find a smooth crossover of the axial force between f approximately square root of (sigma) and f approximately sigma as the membrane tension sigma increases and the tube radius shrinks. This crossover occurs around the most physiologically relevant membrane tensions. Our work may be important in (i) interpreting experiments in which axial force is related to the tube radius or membrane tension, and (ii) constructing dynamical theories for biopolymer growth in narrow tubes where these fluctuation effects control the tube radius.  相似文献   

18.
Drawing single mode fibers over a flame generates tapered fibers with waist diameters of approximately 1–3 micrometers and waist lengths of up to 90?mm. We demonstrate how the profile of such tapered fibers can be determined. We then characterize the white light that is generated in a variety of such fibers, showing its dependence on waist length and waist diameter and demonstrating its dependence on pulse parameters such as pulse duration, spectral position, and pulse power. A comparison with theoretical calculations using a nonlinear Schrödinger equation model including Kerr nonlinearities is given. Furthermore, we show XFROG spectrograms of the pulses propagating through tapered fibers, confirming the model of soliton splitting in the anomalous dispersion regime.  相似文献   

19.
Microstructured crystalline optical fiber from silver halides is described. Both experimental and theoretical evidences are presented to establish that the fiber is effectively single mode at wavelength 10.6 micro m with numerical aperture NA=0.16 and optical losses of approximately 2 dB/m. Crystalline microstructured optical fibers offer key advantages over step-index optical fibers from silver halide crystals. The wide transmission range of wavelengths 2-20 micro m provides great potential for applications in spectroscopy and for the development of a range of new crystalline-based nonlinear optical fibers.  相似文献   

20.
Polarization mode dispersion (PMD) measurements are presented for a sample of installed optical fibers. High PMD values are fairly common, with 9 of the 71 fibers having PMD coefficients above 0.3 ps km1 2. The results are analyzed in terms of the age of the fibers and the type of cabling. Measurements are presented for a number of concatenated fiber links, and the results show that the PMD value of the link is approximately equal to the square root of the sum of the squares of the PMD values of the individual fibers.  相似文献   

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