The spectroscopic properties of Ni(2+)- doped nanocrystalline glass-ceramic fibers are reported. The cerammed fibers show strong fluorescence with peak wavelength at 1250 nm, 3-dB bandwidth at ~250nm, measured lifetimes at >1ms, and low-fluorescence saturation powers (~35mW) for 980-nm diode pumping. Current diode-pumped output powers are ~100microW .
We report an efficient glass-ceramic fiber laser and show that its slope efficiency (~30%) is not compromised by the presence of Nd-doped fluoride crystals embedded within the core of the single-mode optical fiber. In contrast, the spectroscopy (fluorescence and gain spectrum) of the Nd(3+) ions is dramatically changed by the ceramming process, an indication of strong partitioning of the rare-earth ions into the CdF(2):PbF(2):YF(3) crystal environment. The enormous potential for a new range of optical devices based on transparent glass-ceramic materials is highlighted.
Primarily to meet the dramatic increase in Internet traffic, a substantial expansion in new fiber-optic networks has been seen in the last few years, increasing the total amount of transmission fiber deployed in the field. However, increased capacity has also been achieved by utilizing more of the available bandwidth present in the currently installed fiber. A key component in facilitating this increase in bandwidth is the erbium-doped fiber amplifier (EDFA), which provides efficient broad-band gain in the 1530–1560-nm telecommunications window. Erbium-doped glasses can be drawn into low-loss fiber, and the width of the gain band can be controlled with glass composition. With appropriate composition and design, EDFAs can simultaneously amplify 32 or more wavelengths, providing a 32-fold increase in data capacity over single-channel systems. These devices can boost signal strength by a factor of 1000, with high reliability and low noise at data rates exceeding 1 Tbit/s. In this article, we review some of the properties that are key to the success of EDFAs and discuss the potential for other rare-earth-doped glass-fiber combinations that may find possible applications in future telecommunications networks.Fiber optics have revolutionized the telecommunications industry, providing more information capacity and greater distances between signal boosters than copper wire and coaxial cable. The attenuation in coaxial systems increases exponentially with signal frequency, making high-speed transmission over long distances impractical. The best copper systems have a bandwidth of about 10 Mbit/s and are limited to lengths of less than 200 m at high data rates. In contrast, the attenuation of SiO2 optical fibers is low and independent of signal frequency, thus optical fiber can easily support 100 Gbit/s (10,000 times the capacity of copper) over 80 km and is currently only limited by the speed of the transmission and receiving electronics, with capacities in excess of 50 Tbit/s theoretically possible.1 For links in excess of 80 km, signal amplification is necessary to prevent total loss of the signal. In the 1980s, amplification was done with electronic devices called repeaters that detected the light, converted it to an electronic signal, amplified, retimed, and then retransmitted it as an optical pulse.The field of optical telecommunications has itself undergone a revolution. In the late 1980s, the invention of the all-optical amplifier allowed for simultaneous amplification of multiple channels in a single optical fiber each at a different wavelength or color of light. SiO2 fibers have a minimum in attenuation in the infrared (IR) portion of the optical spectrum near 1550 nm, as shown in Figure 1. The EDFA fortuitously provides high gain and low noise in the 1530-1560-nm spectral window. This technology now enables simultaneous amplification of 32 channels in a single fiber without the need for optical-to-electronic conversion. Thus single-fiber capacities of 320 Gbit/s are currently being deployed today. To perform this electronically, each channel would have to be separated (demultiplexed), amplified by its own costly repeater, and then recombined (multiplexed) in the fiber. Researchers are now perfecting 100-channel EDFAs in the lab.
Infrared emission at 1.8, 2.9, and 4.3 microm is measured in dysprosium-doped gallium lanthanum sulfide (Ga:La:S) glass excited at 815 nm. Emission cross sections were calculated by Judd-Ofelt analysis, the Füchtbauer- Ladenburg equation, and the theory of McCumber. The sigmatau value for the 4.3-microm transition is ~4000 times larger in the Ga:La:S glass than in a dysprosium-doped LiYF(4) crystal, which has lased on this transition. The large sigmatau value and the recently reported ability of Ga:La:S glass to be fabricated into fiber form show the potential for an efficient, low-threshold mid-infrared fiber laser. The f luorescence peak at 4.3 microm coincides with the fundamental absorption of atmospheric carbon dioxide, making the glass a potential laser source for gas-sensing applications.
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