Herndonalbrektsen1367

Stimulated polariton scattering (SPS) and stimulated Raman scattering (SRS) in $\rm RbTiOPO_4$RbTiOPO4 (RTP) crystal are combined in an intracavity-pumped Stokes parametric oscillator (SPO) to extend the tunable Stokes laser spectral range. The pumping laser wavelength is 1064 nm from a diode-end-pumped acousto-optically Q-switched NdYAG laser. By the SPS process in the SPO, the SPS-Stokes wave can be discontinuously tuned in the range of 1075.7-1076.0 nm, 1077.7-1080.4 nm, 1081.8-1082.2 nm, and 1084.8-1087.8 nm, respectively. By the following SRS process in the same RTP crystal, the laser wavelength is further shifted in the range of 1107.7-1108.1 nm, 1109.0-1112.7 nm, 1114.3-1115.1 nm, and 1117.8-1121.1 nm, respectively. A maximal average output power of 970 mW is achieved for the SRS-Stokes wave at the peak wavelength of 1118.8 nm. It is obtained when the diode power is 7.9 W, and the pulse repetition frequency (PRF) is 10 kHz.We demonstrate an all-fiber wavelength conversion system from the C-band to the wavelength range of 2.30-2.64 µm of the mid-infrared (MIR). A series of nonlinear processes is used to perform this spectral shift in excess of 80 THz; from optical pulses in the C-band, self-phase modulation spectral broadening and offset filtering generate probe pulses in the C- and L-band. In parallel to this, Raman-induced soliton self-frequency shift converts pulses from the C-band into pump pulses in the 2 µm wavelength band. The resulting synchronized probe and pump pulses interact via degenerate four-wave mixing to produce wavelength-converted idler pulses in the MIR. Silica fiber is used for nonlinear processes at wavelengths $ \lt 2\;\unicodex00B5\rm m$ less then 2µm whereas chalcogenide glass is used for nonlinear processes at wavelengths $ \ge 2\;\unicodex00B5\rm m$≥2µm. This system is a major step toward the development of compact MIR optical sources generated from widespread pump lasers of the C-band.In Opt. Lett.45, 5755 (2019)OPLEDP0146-959210.1364/OL.44.005755, a factor is missing in the result of Eq. (1). Thus, the width of the comb spectrum $ \Delta u $Δν becomes $ \Delta u = 2\sqrt 3 \Gamma \alpha _e $Δν=23Γαe.In this Letter, a novel, to the best of our knowledge, structural configuration on a transparent microsphere is proposed to engineer the focusing light field. By patterning a hybrid diffractive Fresnel zone plate structure on a partially milled microsphere using a focused ion beam, wavelength-dependent switching between mono-focal and multi-focal functionalities can be achieved. Generation of on-axis tri-foci and mono-focus light fields under high numerical-aperture ($\rm NA\gt 0.67$NA>0.67) conditions at two working wavelengths (405 nm and 808 nm) have been demonstrated both numerically and experimentally.In this Letter, based on two advanced tunable ultra-flat optical frequency comb generators (T-FOCGs), a coherent channelized receiver with high channelized efficiency and reconfigurability is proposed. Raf inhibitor In the T-FOCG, the number of 1 dB comb lines increases with the gain, but the optical power of these 1 dB comb lines has almost the constant variance. In the proposed scheme, one optical carrier can support four sub-channels. Meanwhile, the number and bandwidth of sub-channels, as well as the bandwidth and center frequency of an original broadband signal, are all tunable. In this Letter, we verify the feasibility of the coherent channelized receiver by channelizing a 4 GHz signal with a 20 GHz center frequency into four 1 GHz sub-channels, and the reconfigurability is demonstrated by channelizing a 10 GHz signal with frequencies from 18 to 28 GHz into five 2 GHz sub-channels. Moreover, the error-vector magnitude curves of the directly received and the channelized quadrature amplitude modulation (QAM) signal at different amounts of beat noise are compared.We propose the asymmetric direct detection (ADD) of twin-single sideband (SSB) signals based on a simple receiver front-end composed of one optical filter and two photodiodes. ADD exploits the photocurrent difference between a filtered and unfiltered signal pair to reconstruct and linearize the received twin-SSB signal with a high electrical spectral efficiency (ESE). We evaluate the performance impact of the critical system parameters on ADD and demonstrate 231 Gb/s net rate 16-QAM twin-SSB transmission with 6.03 b/s/Hz ESE over an 80 km standard single-mode fiber below the $1 \times 10^ - 2$1×10-2 hard-decision forward error correction threshold. We also found that the bit error rate performance of ADD is robust against the relative center wavelength drifting of the optical filter.Offset aperture and split detector imaging are variants of adaptive optics scanning ophthalmoscopy recently introduced to improve the image contrast of retinal cells. Unlike conventional confocal scanning ophthalmoscopy, these approaches collect light laterally decentered from the optical axis. A complete explanation of how these methods enhance contrast has not been described. Here, we provide an optical model with supporting in vivo data that show contrast is generated from spatial variations in the refractive index as it is in phase contrast microscopy. A prediction of this model is supported by experimental data that show contrast is optimized when the detector is placed conjugate with a deeper backscattering screen such as the retinal pigment epithelium and choroid, rather than with the layer being imaged as in conventional confocal imaging. This detection strategy provides a substantial improvement in the contrast these new methods can produce.We present brain imaging experiments on rat cortical areas, demonstrating that, when combined with a suitable high-brightness, cell-specific genetically encoded fluorescent marker, three-photon-excited fluorescence (3PEF), enables subcellular-resolution, cell-specific 3D brain imaging that is fully compatible and readily integrable with other nonlinear-optical imaging modalities, including two-photon-fluorescence and harmonic-generation microscopy. With laser excitation provided by sub-100-fs, 1.25-µm laser pulses, cell-specific 3PEF from astrocytes and their processes detected in parallel with a three-photon-resonance-enhanced third harmonic from blood vessels is shown to enable a high-contrast 3D imaging of gliovascular interfaces.