Remote measurements of Earth's surface from ground, airborne, and spaceborne instruments show that its albedo is highly variable and is sensitive to solar zenith angle (SZA) and atmospheric opacity. Using a vali-dated radiative transfer calculating toolbox, DISORT and a bidirectional reflectance distribution function library, AMBRALS, a land surface albedo (LSA) lookup table (LUT) is produced with respect to SZA and aerosol optical depth. With the LUT, spectral and broadband LSA can be obtained at any given illumination geometries and atmospheric conditions. It provides a fast and accurate way to simulate surface reflectance over large temporal and spatial scales for climate study.

We experimentally demonstrate one-to-five quadrature phase-shift keying (QPSK) wavelength multicasting based on four-wave mixing in bulk semiconductor optical amplifier. The input 25 Gb/s nonreturn-to-zero QPSK signal is successfully multicast to five new wavelengths with all information preserved. All the multicast channels are with a power penalty less than 1.1 dB at a bit error rate (BER) of 10-3. A characterization of the conversion efficiency in terms of pump and signal powers using the BER as figure of merit is also presented, the results indicate that the pump and signal powers should be optimized to eliminate the introduced deleterious nonlinear components.

The rapid growth of the Internet raises the importance of resource planning of Internet protocol (IP) over elastic optical networks (EONs), which is a challenging task due to more complex and obscure physical -constraints of it. Compared with network cost, the power consumption may eventually become the barrier to the expansion of the Internet. We present an energy-efficient virtual topology design (VTD) scheme for IP over EON. We explicitly explain and analyze the mixed integer linear programming model and the heuristic algorithm for this scheme. Numerical results show that the proposed VTD scheme can significantly save power consumption.

An endless polarization stabilization control system is proposed in this letter. The system is independent of transmission data rate and modulation format, and it does not need high-speed circuit to track fast polarization change. Adaptive inertia weight particle swarm optimization algorithm is used and the effectiveness of polarization stabilization control is experimentally verified.

We experimentally investigate multigranularity optical subband switching functionality between two superchannels with slight error vector magnitude penalty. One is 4×39 Gb/s polarization-division-multiplexed (PDM) quadrature phase shift keying discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-spread-OFDM) superchannel with 12.5 GHz band spacing. The other is 8×29 Gb/s PDM-16-quadrature amplitude modulation Nyquist pulse shaping superchannel with 6.25 GHz band spacing. To the best of our knowledge, this is the first time that optical switching functionality for individual band between different superchannels with multigranularity is realized.

A tunable two-section amplified feedback laser, which employs an amplifier section as the integrated feedback cavity, is designed and fabricated for dual-mode operation with mode separation of 100 GHz. Detailed simulations and experimental characterizations on the performance of the laser are presented. Promising dual-mode emission with continuous tuning range over 16 GHz (87.41–103.64 GHz) is experimentally demonstrated.

We demonstrate a visible light communication system based on DC-biased optical orthogonal frequency-division multiplexing (DCO-OFDM) and achieve a bit rate of 481 Mb/s at a communication distance of 65 cm by employing single 1-W commercial phosphorescent light-emitting diode (LED). The average bit error rate of the received data is 2.3×10-3, which is below the forward error correction limit, 3.8×10-3. The effect of -signal clipping in DCO-OFDM system is studied and resource allocation algorithms are utilized. At least 13% capacity improvement can be obtained by suitable signal clipping and resource allocation.

In this work, we propose a new design of all-optical triplexer based on of metal–insulator–metal (MIM) plasmonic waveguide structures and ring resonators. By adjusting the radii of ring resonators and the gap distance, certain wavelengths can be filtered out and the crosstalk of each channel can also be reduced. The numerical results show that the proposed MIM plasmonic waveguide structure can really function as an -optical triplexer with respect to the three wavelengths, that is, 1310, 1490, and 1550 nm, respectively. It can be widely used as the fiber access network element for multiplexer–demultiplexer wavelength selective in -fiber-to-the-home communication systems with transmission efficiency higher than 90%. It can also be a potential key component in the applications of the biosensing systems.

Double-weight optical code division multiple access (OCDMA) systems are proposed for studying differentiated quality-of-service transmission. Based on quadratic congruence code (QCC), we construct a one-dimensional double-weight code family, which can be well utilized in incoherent synchronous double-weight OCDMA networks. By introducing algebraic transformation to code sequences of QCC in level 1, we obtain multiple double-weight codes with cross-correlation 1. Under the same-bit-power assumption, the performance of low-weight codes can be significantly improved and is always superior to that of high-weight codes in double-weight OCDMA systems with power control. This property is contrary to previous conclusions under the same-chip-power assumption.

We present a down-looking synthetic aperture imaging ladar demonstrator and its experiments over 1.2 km in the field. The achieved imaging resolution is in agreement with the theoretical design, and the resulting two-dimensional image is satisfied. The capability to eliminate the influence from atmospheric turbulence is fully proven by the experiments.

The monitoring of increased intracranial pressure (ICP) is necessary in the diagnosis and treatment of patients with neurological disease because it can provide an insight into the mechanism of the head injury. In this letter, we develop a novel miniature Fabry–Perot (F-P) sensor for ICP measurement. The proposed sensor is fabricated by using a commercially available fusion splicer and a fiber cleaver, by which many difficult art problems involved in fabrication are solved and the online monitoring of the F-P cavity is actualized. The sensor exhibits a linear response to the applied pressure over the range of 0–25 kPa (ample for ICP measurement), with a sensitivity of 10.18 nm/kPa, a resolution of 0.1 kPa, and a reduced thermal sensitivity of 0.068 nm/°C, which shows it can meet the requirements of ICP measurement.

We demonstrate an all-fiber, high-power, and high stability ultrafast laser source operating at 1563 nm. A highly stable, self-starting carbon nanotube (CNT) mode-locked femtosecond fiber laser is used as the seed source. The amplifier stage uses a fiber chirped pulse amplification configuration. The main power amplifier is based on a cladding-pumped Er–Yb co-doped fiber with 10 μm active single-mode core diameter. The laser source provides 3.4 W average output power at 75 MHz repetition rate. The pulses are compressed to 765 fs by a low-loss transmission grating pair. The robust, compact, and high-power 1560 nm fiber laser source can be used for eye surgery and solar cell micromachining.

We propose and experimentally demonstrate a multi-wavelength thulium-doped fiber (TDF) laser based on all-fiber Mach–Zehnder interferometer (MZI) at 1.9 mm. Here a segment of 4 m single-mode TDF is pumped by 1568 nm fiber laser for 2 mm band optical gain. The MZI includes two cascaded 3 dB coupler. A segment of 3.5 m long un-pumped polarization-maintaining TDF and polarization controller (PC) are joined in the ring cavity to suppress the mode competition. Multi-wavelength lasers at 1.9 mm with wavelength number from one to four are obtained by adjusting the PC and the stability of output power of multi-wavelength fiber laser is analyzed.

We study the influence of alkali oxides on the near-infrared (NIR)-emitting thermal stability of Bi-doped R2O–SiO2–B2O3–Al2O3 (R = Li, Na, K) glasses below Tg. Results show that undergoing heat treatment, re-markable luminescence quenching occurs for the glasses containing Na2O and K2O due to the formation of Bi metallic colloids, whereas the glass with Li2O shows much better thermal stability. These changes can be understood by the tendency of modifier cations with lower mobility and higher tightness network to restrain the transport of Bi-related NIR-emitting centers. The results provide a scientific reference for composition design of Bi-doped optical fiber.

We examine the temperature-dependent reflection shifts, microscopic morphology, and laser emission of polymer-stabilized cholesteric liquid crystals. The preparation parameters, including the concentration of photo-initiator and laser dye, are evaluated and their influence on reflection band is considered not to be ignorable. Inadequate ultraviolet (UV) curing time less than the required value to fully photo-polymerize the monomer can also influence the spectral position and shape of the reflection band but still favor possible band-edge lasing, whereas extending UV curing duration can weaken and eventually eliminate the laser emis-sion. The behaviors are explained using the results derived from the mean field theory.

Noninvasive glucose monitoring (NIGM) techniques based on optical coherence tomography (OCT) are affected by several perturbing factors, including variation of tissue temperature. We first design a temperature control module integrated with an optical scanning probe to precisely control the temperature of skin tissues. We investigate the influence of temperature on NIGM with OCT by correlation analysis at different depths of in vivo human skin. On average, the relative changes in attenuation coefficient ( μt ) per 1 °C of temperature lead to 0.30 ± 0.097 mmol/L prediction error of blood glucose concentration. For improving the accuracy of NIGM, this temperature dependence must be taken into account.

The accuracy of the background optical properties has a considerable effect on the quality of reconstructed images in near-infrared functional brain imaging based on continuous wave diffuse optical tomography (CW-DOT). We propose a region stepwise reconstruction method in CW-DOT scheme for reconstructing the background absorption and reduced scattering coefficients of the two-layered slab sample with the known geometric information. According to the relation between the thickness of the top layer and source–detector separation, the conventional measurement data are divided into two groups and are employed to recon-struct the top and bottom background optical properties, respectively. The numerical simulation results demonstrate that the proposed method can reconstruct the background optical properties of two-layered slab sample effectively. The region-of-interest reconstruction results are better than those of the conventional simultaneous reconstruction method.

We propose a novel method by combining the total variation (TV) with the high-degree TV (HDTV) to improve the reconstruction quality of sparse-view sampling photoacoustic imaging (PAI). A weighing function is adaptively updated in an iterative way to combine the solutions of the TV and HDTV minimizations. The fast iterative shrinkage/thresholding algorithm is implemented to solve both the TV and the HDTV minimizations with better convergence rate. Numerical results demonstrate the superiority and efficiency of the proposed method on sparse-view PAI. In vitro experiments also illustrate that the method can be used in practical sparse-view PAI.

We report low pump power high-efficiency frequency doubling of a fundamental laser beam at 795 nm, corresponding to the rubidium D1 line, to generate UV light at 397.5 nm using a periodically poled KTiOPO4 (PPKTP) crystal in a ring cavity. We obtain maximum stable output power of 49 mW for mode-matching pump power of 110 mW, corresponding to 45% raw efficiency (56% net efficiency when considering the output coupling mirror's 80% transmission). This is the highest efficiency obtained at this wavelength in PPKTP with such low pump power. We obtain 80% beam coupling efficiency to single-mode fiber, demonstrating high beam quality.

The temperature acceptance bandwidth of second-harmonic generation (SHG) can be dramatically improved by using two different kinds of nonlinear crystals with opposite signs of temperature derivation of phase mismatch. We study two SHG processes for the existing 1064 and 1550 nm high-average-power lasers. The numerical results show that the temperature acceptance bandwidth for SHG at 1064 nm can be three to five times larger than that of traditional single-crystal design, and it is also larger than that of using temperature-insensitive yttrium calcium oxyborate crystal. Importantly, the proposed design is applicable to various wavelengths, which suggests its potential in high-average-power SHG applications.

The spontaneous emission spectrum in the optically excited single-electron-tunneling device coupled to the side dot is analytically found to be determined by the 12 exciton-complex optical channels with different optical weight functions. The electronic tunneling channels and optical transition channels co-determine the emission, where the competition between the electron-like and hole-like channels leads to the tail effect and the competition between the lower and higher energy resonant optical channels leads to the blueshift (redshift) of the emission signal.

We fabricate low threshold current monolithic distributed feedback (DFB) laser with a multi-mode interface (MMI) combiner using butt-joint metal-organic chemical vapor deposition technology with different waveguide structures. Multi-layer mask self-aligned photolithography technology is used to form different waveguides in active and passive regions, respectively. The result shows that the laser threshold current is lower than 10 mA, with 50 dB side-mode suppression ratio.

We propose new types of hybrid plasmonic waveguides for low-threshold nanolaser applications. Modal properties and lasing threshold under different geometric shapes and parameters are investigated and -analyzed by the finite element method, aiming to realize both low propagation and high field confinement. Results show that a smaller gap width and a larger round corner radius of the metal film reduce the lasing threshold. These new structures can open up new avenues in the fields of active plasmonic circuits.

Liquid 4,7-bis(1-decynl)-2,1,3-benzothiadiazole (DOBT) is found to exhibit good photoluminescence (PL) with high PL efficiency up to 17.8%. In particular, DOBT shows electron mobility of 5.2×10-6 cm2V-1s-1, demonstrating a promising n-type liquid semiconductor for optoelectronic application.

The even-order dispersion cancellation effect based on the frequency anti-correlated photon pairs has attracted much attention in the research of quantum dispersion cancellation in two-photon systems. In this letter, we demonstrate a four-photon quantum interferometry in which we can not only observe the even-order dispersion cancellation effect but also the odd-order cancellation. Importantly, the four-photon scheme can get a much better resolution than the two-photon case and help us get a better understanding of the -interference phenomenon in a four-photon interferometry.

We demonstrate the control of neutral fragmentation of methane (CH4) induced by a Ti:sapphire intense laser pulse (800 nm, 40 fs) by using a pump–probe spectroscopy. Enhancement of the fluorescence emission from the neutral radical CH (A2Δ → X2Π) induced by the intense laser field (~1014 W/cm2) is observed when the wavelength of the probe laser pulse is tuned to 400 nm. The phenomena are explained based on excitation enhancement of the super-excited state of the parent molecule resulting in an increase in neutral dissociation of the methane molecules.

We experimentally show dark pulse generation in all-normal dispersion multiwavelength erbium-doped fiber laser (EDFL) with a long cavity of figure-of-eight configuration. The EDFL generates a stable multiwavelength laser with 0.47 nm spacing at 24 mW threshold pump power, while the number of lines obtained increases with the pump power. A dark pulse emission is observed as the pump power is increased above 137 mW, with fundamental repetition rate of 29 kHz and pulse width of 2.7 μs. It is observed that the dark pulse train can be shifted to second-, third-, and fourth-order harmonic dark pulses by carefully adjusting the polarization controller. For the fundamental dark pulse, the maximum pulse energy of 32.4 nJ is obtained at pump power of 146.0 mW.

We report the formation dynamics of periodic ripples on GaAs induced by femtosecond laser pulses (800 nm, 50 fs) via a collinear time-resolved imaging technique with a temporal resolution of 1 ps and a spatial resolution of 440 nm. The onset of periodic ripples emerges in the initial tens of picoseconds in the timescale of material ejection. The periodic ripples appear after irradiation of at least two pump pulses at surface defects produced by the first pulse and the ripple positions kept stable until the formation processes complete. The formation mechanisms of laser-induced periodic ripples are also discussed.

An optical model of bright pupil effect based on Chinese human eye model is presented. The effects of the incident rays angle and the size of pupil on bright pupil effect are analyzed theoretically. For the incident rays with 5°–15° field of view, the spot diagram of emergent light is also presented. With the pupil diameters of 3–8 mm, the intensity distributions formed by emergent light are calculated. The optical model of bright pupil effect based on Chinese human eye provides a suitable model for the related further research studies and applications on bright pupil effect with Chinese eye.

A method based on the XYZLMS interim connection space is proposed to accurately acquire the multi-spectral images by digital still cameras. The XYZLMS values are firstly predicted from RGB values by polynomial model with local training samples and then spectral reflectance is constructed from XYZLMS values by pseudo-inverse method. An experiment is implemented for multi-spectral image acquisition based on a commercial digital still camera. The results indicate that multi-spectral images can be accurately acquired except the very dark colors.