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Characterization
Published in Luc B. Jeunhomme, Single-Mode Fiber Optics, 2019
The fiber Raman laser source yields many measurement data because of its broadband spectrum, and this in turn provides better accuracy than using a few (3 to 7) laser diodes at discrete wavelengths. Differences between the two measurement techniques are about 0.1 ps/nm × km around 1300 mm for unshifted fibers and 0.4 ps/nm × km for dispersion-flattened fibers.
Linear Raman Spectroscopy
Published in Helmut H. Telle, Ángel González Ureña, Laser Spectroscopy and Laser Imaging, 2018
Helmut H. Telle, Ángel González Ureña
Because of the aforementioned difficulties with blackbody radiation standards, when used in ordinary laboratory environments, dedicated, passive intensity calibration standards have been developed at NIST for the most common Raman laser excitation sources (Choquette et al. 2007). These standards consist of an optical glass element (in the shape of a thick slide) that emits a broadband luminescence spectrum when irradiated with light from the Raman excitation laser (e.g., luminescence curves related to common Raman excitation lasers are shown in Figure 12.5c). The actual shape of the luminescence spectrum is approximated a polynomial expression, based on NIST calibration, which replicates the shape to better than ~2% over the complete spectral range for which it is certified. Currently, standards exist for the Raman laser wavelengths λL = 488/514, 532, 633, 785, and 1064 nm. Utilizing this mathematical description of the luminescence spectrum in conjunction with the measured luminescence spectrum of the standard, one can determine the correction function for the intensity response of the complete spectrometer system.
Advanced Optical Components
Published in David R. Goff, Kimberly Hansen, Michelle K. Stull, Fiber Optic Video Transmission, 2013
David R. Goff, Kimberly Hansen, Michelle K. Stull
A Raman optical amplifier consists of little more than a high-power pump laser, usually called a Raman laser, and a WDM or directional coupler. The optical amplification occurs in the transmission fiber itself, distributed along the transmission path. With amplification up to 10 dB, Raman optical amplifiers provide a wide gain bandwidth (up to 100 nm), allowing them to operate using any installed optical fiber (single-mode optical fiber, TrueWave, etc). By boosting the optical signal in transit, Raman amplifiers reduce the effective span loss and improve noise performance.
Self-Raman Nd-doped vanadate laser: a pump source of organic crystal based difference frequency generation
Published in Journal of Modern Optics, 2020
Pengxiang Liu, Feng Qi, Weifan Li, Zhaoyang Liu, Yelong Wang, Xin Ding, Jianquan Yao
The schematic diagram of the self-Raman laser (Figure 1) is similar to that in a previous experiment [17]. A diffusion-bonded Nd:YVO4-YVO4 crystal (a-cut) is in-band pumped by 878.6 nm laser diodes. M2 is the input mirror with anti-reflection coating at 878.6 nm and high-reflection coating at the fundamental laser 1342 nm and Stokes wave 1525 nm (R2l,s = 99.8%, subscripts l and s denote the fundamental laser and Stokes wave). AO is the acousto-optically Q-switch with a length lAO. M1 is the output mirror with proper reflectivities at the two wavelengths R1l,s. The diffusion-bonded crystal and in-band pumping could well overcome the drawback of the thermal effect. Besides, we can control the Raman gain and the time delay between dual-wavelength pulses by varying the length of non-doped YVO4 crystal l2, which will be discussed later.
Investigation of radiation-induced surface activation effect in austenitic stainless steel under ultraviolet and γ-ray irradiations
Published in Journal of Nuclear Science and Technology, 2019
Sho Kano, Huilong Yang, John McGrady, Tomonori Ihara, Hazuku Tatsuya, Hiroaki Abe
Raman measurements of the oxide layer were performed at room temperature using a RamanRxn System manufactured by Kaiser Optical System, in which a green-laser with the wavelength of 532 nm was used. The spot size of the Raman laser was ~2 μm. It is generally believed that the vibration mode for the oxygen-sublattice can be detected in ceramic materials by Raman. Honjo et al. reported that from the XPS analyses of zirconia and titania before and after UV and γ-ray irradiation [15], the bridging oxygen of the surface became smaller due to irradiation, and the magnitude of chemisorbed hydroxyl groups increased with increasing irradiation damage. Thus, in this study, the Raman analyses were performed in the oxidized specimens to investigate the bonding state of oxygen in the oxide layer, based on which the hydrophilicity can be elucidated.
Oxidation behavior of Al2O3 added reaction-sintered SiC ceramics in wet oxygen environment at 1300°C
Published in Journal of Asian Ceramic Societies, 2018
Qingliang Shan, Jianbao Hu, Jinshan Yang, Yanmei Kan, Haijun Zhou, Guangxiang Zhu, Yudong Xue, Shaoming Dong
In order to better explain the corrosion resistance effect of Al2O3 in water vapor, the surface of oxidation layer after oxidized under O2/H2O atmosphere was analyzed by micro-zone Raman spectra. Although the glass phase at room temperature does not completely represent its true state at high temperatures, it can reflect the difference of bonded structure at high temperatures to some extent. There are some different vibrational modes originated from the relative arrangement of atomic or molecular units in the glass network. Apart from the amorphous glass phase, well-crystallized Si, SiC and C phases are also present in Figure 7. The appearance of Si, SiC and C is quite unexpected. It is probably resulted from Raman laser penetrating the oxide layer. Broad bands and protuberant are attributed to superposition of small adjacent peaks. According to the location of broad bands, the Raman spectra were divided into three regions for convenience, low-frequency region (LF) 450–750 cm−1, mediate frequency region (MF) 1100–1500 cm−1 and high frequency region (HF) 2500–3400 cm−1. Compared to that of sample without Al2O3, the broad bands of samples with Al2O3 have more obvious protuberant in LF region, less obvious protuberant in MF region and less broad bands in HF region.