Troelsenwright9596

A wavelength-tunable single-mode laser with a sub-kilohertz linewidth based on parity-time (PT)-symmetry is proposed and experimentally demonstrated. The proposed PT-symmetric laser is implemented based on a hybrid use of an optical fiber loop and a thermally tunable integrated microdisk resonator (MDR). The MDR, implemented based on the silicon-on-insulator, operates with the optical fiber loop to form two mutually coupled cavities with an identical geometry. By controlling two light waves passing through the two cavities, with one having a gain coefficient and the other a loss coefficient but with an identical magnitude, a PT-symmetric laser is implemented. Thanks to an ultranarrow passband of the cavity due to PT-symmetry, single-longitudinal mode lasing is achieved. The tuning of the wavelength is implemented by thermally tuning the MDR. The proposed PT-symmetric laser is demonstrated experimentally. Single-longitudinal mode lasing at a wavelength of around 1555 nm with a sub-kilohertz linewidth of 433 Hz is implemented. The lasing wavelength is continuously tunable from 1555.135 to 1555.887 nm with a tuning slope of 75.24 pm/°C.We provide a correction to the spectral dependence of the three-photon absorption in zinc-blende semiconductors using Kane's 4-band model in Opt. Lett.33, 2626 (2008).OPLEDP0146-959210.1364/OL.33.002626.Omni-directional, ultra-small-angle x-ray scattering imaging provides a method to measure the orientation of micro-structures without having to resolve them. In this letter, we use single-photon localization with the Timepix3 chip to demonstrate, to the best of our knowledge, the first laboratory-based implementation of single-shot, omni-directional x-ray scattering imaging using the beam-tracking technique. check details The setup allows a fast and accurate retrieval of the scattering signal using a simple absorption mask. We suggest that our new approach may enable faster laboratory-based tensor tomography and could be used for energy-resolved x-ray scattering imaging.We report on the relation between the localization length and level-spacing characteristics of two-dimensional (2D) optical localizing systems. Using the tight-binding model over a wide range of disorder, we compute spectro-spatial features of Anderson localized modes. The spectra allow us to estimate the level-spacing statistics while the localization length $ \xi $ξ is computed from the eigenvectors. We use a hybrid interpolating function to fit the level-spacing distribution, whose repulsion exponent $ \beta $β varies continuously between 0 and 1, with the former representing Poissonian statistics and the latter approximating the Wigner-Dyson distribution. We find that the $ (\xi ,\beta ) $(ξ,β) scatter points occupy a well-defined nonlinear locus that is well fit by a sigmoidal function, implying that the localization length of a 2D disordered medium can be estimated by spectral means using the level-spacing statistics. This technique is also immune to dissipation since the repulsion exponent is insensitive to level widths, in the limit of weak dissipation.In this work, we report and analyze the cause of the surprising observation of visible light generation in the cladding of silica-based continuous-wave (CW), near-infrared fiber lasers. We observe a visible rainbow of hues in a cascaded Raman fiber laser, which we attribute to second and third harmonic conversion of the different wavelength components propagating in the core of the fiber. The light in the cladding of the fiber occurs through Cherenkov-type phase matching, and a mathematical analysis is presented to estimate the power of the harmonic light generated. We then extend this theory to visible light generation in other types of fiber lasers. Specifically, we analyze the case of a CW supercontinuum generated in standard telecom fibers, and verify our theoretical predictions with experimental results through visible spectra collected.The performance of sensors, including optical fiber sensors, is commonly limited by the tradeoff between a large dynamic range and a high resolution. In this Letter, in order to optimize both, we propose an inline multimode interferometer sensor based on a suspended-core microstructured optical fiber. Due to the existence of multiple pairs of mode interferences, the transmission spectrum of the interferometer consists of dense fringes modulated by a lower envelope. Since these mode interferences take place in the uniform material with the same length, the dense fringes and the lower envelope have an identical sensing response without crosstalk. Hence, the sensor integrates the large dynamic range of the lower envelope and the high resolution of the dense fringes. Strain-sensing performance is investigated to validate the characteristic of the large dynamic range and the high resolution of the proposed sensor. The dynamic range, theoretically 0-9200 µɛ, is 12 times larger than for the dense fringes, and the resolution is 17.5 times higher than for the lower envelope.Precision spectroscopy of fundamental bands of molecules in the mid-infrared (MIR) region is of great interest in applications of trace detection and testing fundamental physics, where high-power and narrow-linewidth MIR lasers are needed. By using a frequency-stabilized near-infrared laser as a seed of the signal light of a continuous-wave optical parametric oscillator, we established a broadly tunable MIR light source that has an output power of several hundred milliwatts and a linewidth of a few tens of kilohertz. The MIR laser frequency drift was reduced to below 1 kHz by using an optical frequency comb to stabilize the frequency of the 1064 nm pumping laser. The performance of the light source was investigated and tested by measuring the saturated absorption spectroscopy of a few molecular transitions at 3.3 µm.We experimentally and numerically demonstrated the generation of a (3, 1) vector signal by a single Mach-Zehnder modulator (MZM) without pre-coding. The MZM is driven by the (3, 1) modulated signal after photoelectric conversion by the "square law" of a photodetector. Although the phase changes, the corresponding constellation distribution is consistent with that of the regular signal. Our proposed scheme effectively avoids the pre-coding process with a simple architecture. The bit-error-ratio (BER) results indicate that the (3, 1) signal has a better BER performance than the pre-coded quadrature phase shift keying vector signal, and both are below $3.8\times 10^ - 3$3.8×10-3 after 25 km optical fiber transmission.