The carrier envelope phase (CEP) has a direct impact on the physical properties of an isolated attosecond pulse (IAP) and many strong field processes, but it is difficult to measure in reality. Aiming at obtaining more accurate and complete characterization of CEP, we numerically investigate the annular photoelectron momentum spectra of the hydrogen atom ionized by overlapped fields of an IAP and an infrared (IR) pulse. By defining an overlapping parameter, the momentum patterns are classified and optimized for unambiguously measuring the rotation angle of a momentum pattern versus the CEP value. A series of simulations verify its robustness.

We present a technique for fabricating a fluorescence enhancement device composed of metal nanoparticles (NPs) and porous silicon (PSi) diffraction grating. The fluorescence emission enhancement properties of the PSi and the fluorescence enhancement of the probe molecules are studied on PSi gratings. The fluorescence enhancement of the probe molecules on a fluorescence enhancement device is further improved through the deposition of metal NPs onto the PSi grating. In comparison to metal NP/PSi devices, metal NP periodic distributions can produce a stronger fluorescence enhancement that couples with the PSi grating fluorescence enhancement to achieve an overall three-fold enhancement of the fluorescence intensity.

A scheme of triangular-shaped pulses with full duty cycle generation is proposed and analyzed. Benefiting from the feature of orthogonal polarization, two approximate sinusoidal signals on different polarization states can be combined without inducing coherent interference. By tuning the time mismatching between the two signals, an approximately triangular-shaped profile can be obtained in the optical intensity. It is found that the modulation index β is no longer a fixed one, but it can be aligned within a proper range of 0.92 to 1.57. To evaluate the proposal, impacts of radio frequency voltage fluctuation, bias voltage drift, and time mismatching are discussed. Within the defined fitting error (η≤3%), the tolerable range of the modulation index, time mismatching, and voltage have been found, which insures a simple operation in practice.

A simple configuration dual-wavelength fiber laser, by combining the first-order Brillouin laser and the residual pump laser, is proposed and experimentally demonstrated. A 1 km long single-mode fiber is used as the stimulated Brillouin scattering gain medium pumped by a narrow linewidth tunable laser source (TLS). Through simply adjusting the TLS output power, power-equalized dual-wavelength lasing can be achieved with a high optical signal to noise ratio (OSNR) of >80 dB. With the good tunability of the TLS, the dual-wavelength fiber laser has a tunable range of ～130 nm, and simultaneously the beat frequency of the two lasing wavelengths can be tuned from 10.1875 to 11.0815 GHz with the tunable range of 0.8940 GHz. The high stability of the dual-wavelength operation is experimentally verified by the measured beat frequency fluctuation of ≤6 MHz in 1 h and power fluctuation of ≤0.03 dB in 2 h. The temporal characteristics of the fiber laser are also investigated experimentally. The fiber laser will find good applications in fiber sensing and microwave photonics areas.

A passband frequency-electable microwave photonic multiband bandpass filter based on a cascaded fiber Sagnac loop is presented and experimentally demonstrated. A broadband light is sliced by the cascaded fiber Sagnac loop, which serves as a spectrum slicer. After broadband light passes through the spectrum slicer, the sliced broadband light will have the varied periodical spectral characteristics that will cause a transmitted spectral distribution with uniform or multiple periods, then will be modulated by an optical phase modulator and delayed by a dispersive medium. Therefore, a frequency-band-selectable microwave photonic multiband bandpass filter with a suppressed baseband is achieved that can be switched between the single-passband, dual-passband, and triple-passband state. The presented filter exhibits a maximal out-of-band rejection ratio of about 30 dB.

We propose and experimentally demonstrate an adaptive multiple-input multiple-output (MIMO) mode switching scheme for an indoor visible light communication system combined with orthogonal frequency division multiplexing modulation. Only requiring 1 bit feedback from the receiver, the MIMO mode at the transmitter switches between spatial multiplexing and transmit diversity adapting to the channel correlation. In such a way, we can take advantage of both spatial multiplexing and transmit diversity, where the spatial multiplexing benefits for its multiplexing gain in the low channel correlation environment, and the transmit diversity is robust to high channel correlation. Experimental results validate the performance improvement over the pure spatial multiplexing or transmit diversity system. With the increasing of the channel correlation, the measured bit error rates of the proposed system are below the 7% pre-forward error correction (pre-FEC) limit of 3.8 × 10 3 when the transmitted data rate is 50 Mb/s, and below the 20% pre-FEC threshold of 5.0 × 10 2 when the transmitted data rate is raised up to 100 Mb/s.

A model that is based on the propagation equation and coupled mode theory is introduced in order to describe stimulated Raman scattering (SRS) effects in long tapered fiber amplifiers. Based on the presented model, fiber amplifiers with uniform and long tapered fibers are theoretically and numerically simulated. It can be drawn from the results of our simulations that the long tapered fiber has the advantage in suppressing SRS when applied in fiber laser amplifiers. Our results can provide guidance in the designing of system configuration in long tapered-fiber-based fiber laser systems.

Osteoporosis is a progressive bone disease, which is characterized by a decrease in the bone mass and deterioration in bone micro-architecture. In theory, photoacoustic (PA) analysis has the potential to obtain the characteristics of the bone effectively. In this study, we try to compare the PA spectral analysis (PASA) method with the quantitative ultrasound (QUS) method in osteoporosis assessment. We compare the quantified parameter slope from the PASA and broadband ultrasound attenuation from QUS among different bone models, respectively. Both the simulation and ex vivo experiment results show that bone with lower bone mineral density has the higher slope in the PASA method. Our comparison study proves that the PASA method has the same efficiency as QUS in osteoporosis assessment.

The use of a computer-generated hologram (CGH) in interferometric testing provides new methods for highly accurate optical measurement. To fabricate a CGH, polygons are used to approximate the smooth CGH pattern. Because the data size supported by CGH writing machines is limited, the number of polygon vertices must be limited. Therefore, the CGH-encoding method determines the encoding accuracy. To realize a highly accurate optical measurement using CGHs, we propose a CGH-pattern-encoding method based on non-maxima suppression. A self-aligned CGH is designed to verify the accuracy. The experimental result shows that a highly accurate CGH can be fabricated using this method.

The Giant Steerable Science Mirror (GSSM) is the tertiary mirror of the Thirty Meter Telescope (TMT). To evaluate the performance of GSSM, normalized point source sensitivity (PSSn) is investigated. Calibration and metrology allow the estimation of telescope performance at different zenith angles. PSSn also realizes the prediction of the TMT main mirror assembly optical performance. The relationship between PSSn and slope root mean square (RMS) is analyzed theoretically when evaluating the performance of GSSM. First and foremost, the pointing performance of the GSSM prototype (GSSMP) is specified by PSSn and calibrated by a laser tracker. Then, the tracking performance influence on PSSn is taken into consideration. The jitter of the GSSMP also contributes to the degradation of PSSn, and it is also discussed. Lastly, the interaction between GSSM and the main mirror unit is also revealed by PSSn.

A method based on slope stitching for measurement of a large off-axis parabolic trough collector is proposed and applied to the surface shape reconstructed from the gradient data acquired by using the reverse Hartmann test. The entire reflector is divided into three sections with overlapping zones along the concentration direction. A mathematical model for the slope stitching algorithm is developed. An improved reconstruction method combining Zernike slope polynomials iterative fitting with the Southwell integration algorithm is utilized to recover the real three-dimensional (3D) shape of the collector. The efficiency and validity of the improved reconstruction method and the stitching algorithm are experimentally verified.

Sodium-ethane excimer pairs are studied and proved to be a great choice of excimer pumped sodium laser (XPNaL) gain media. The lifetime of the sodium D2 line is studied in a sodium-ethane excimer system excited by a 553 nm laser, and the observed phenomenon of lifetime lengthening is discussed. Amplified spontaneous emission (ASE) of the sodium D2 line is successfully obtained, and its time-resolved and spectroscopic characteristics are studied experimentally. According to the intensity of the ASE signal under different sodium vapor atom densities, the sodium D2 line gain feature of sodium-ethane excimer pairs excited by the 553 nm laser is concluded.

We report a continuous-wave Er:ZBLAN fiber laser with the operation wavelength reaching 3.68 μm. The mid-infrared Er:ZBLAN fiber laser is pumped with the dual-wavelength sources consisting of a commercial laser diode at 970 nm and a homemade Tm-doped fiber laser at 1973 nm. By increasing the launched pump power at 1973 nm, the laser wavelength can be switched from 3.52 to 3.68 μm. The maximum output power of 0.85 W is obtained with a slope efficiency of 25.14% with respect to the 1973 nm pump power. In the experiment, the laser emission at 3.68 μm is obtained with a significant power of 0.62 W, which is the longest emission wavelength in free-running Er:ZBLAN fiber lasers.

A novel H-plane cross-shaped circulator based on magneto-photonic crystals is experimentally investigated. The band gap of the TE mode for the photonic crystals is calculated by the plane wave expansion method. The transmission characteristics of the circulator are simulated by the finite element method. We perform the experiments in the microwave regime to validate the numerical results. At the central frequency of 10.15 GHz, the measured isolation and insertion loss of the circulator reaches 30.2 and 3.93 dB, respectively. The bandwidth of the circulator is about 550 MHz. The optimal experimental value of isolation is higher than the numerical value.

The optical constants, photoluminescence properties, and resistivity of Al-Alq3 thin films prepared by the thermal co-evaporation method on a silicon substrate are studied with various Al fractions. A variable angle spectroscopic ellipsometry is employed to determine the optical constants in the wavelength from 300 to 1200 nm at incidence angles of 65°, 70°, and 75°, respectively. Both the refractive indices and extinction coefficient apparently increase with increasing Al fractions. The intensity of photoluminescence spectra gradually increases with decreasing Al fractions due to intrinsic energy level transition of Alq3 organic semiconductor in the ultraviolet wave band. The resistivity decreases from 42.1 to 3.36 Ω·cm with increasing Al fraction from 40% to 70%, resulting in a larger emission intensity in photoluminescence spectra for the 40% Al fraction sample.

Photoacoustic tomography is a noninvasive and nonionized biomedical imaging modality but it cannot reveal the inner structure and sideward boundary information of blood vessels in the linear array detection mode. In contrast, Monte Carlo (MC) light transport could provide the optical fluence distribution around the entire vascular area. This research explores the combination of linear array transducer-based photoacoustic tomography and MC light transport in the blood vessel quantification. Simulation, phantom, and in vivo experiments are in good correlation with the ultrasound imaging, validating this approach can clearly visualize the internal region of blood vessels from background tissue.

We develop an improved global reconstruction method for Fourier ptychographic microscopy, a newly reported technique for wide-field and high-resolution microscopic observation. The gradational strategy and graphic processing unit computing are applied to accelerate the conventional global reconstruction method. Both simulations and experiments are carried out to evaluate the performance of our method, and the results show that this method offers a much faster convergence speed and maintains a good reconstruction quality.

We experimentally demonstrate a metamaterials (MMs)-based terahertz (THz) sensor to quickly distinguish the cancer tissues from normal tissues. The MMs-based THz sensor has two strong resonance absorption peaks at about 0.706 and 1.14 THz, respectively. When the sensor is covered with cancer tissues, the redshifts at about 0.706 and 1.14 THz are 31 and 19 GHz, respectively. However, if normal tissue is attached to the surface of the sensor, the corresponding redshifts are only 15 and 12 GHz, respectively. This study proposes a new method for quick diagnosis of early lung cancer and other cancers.

We present a new compact radar system to measure a terahertz radar cross section (RCS) of metal plates, trihedral corner reflectors, and an aircraft scaled model with a 0.1 THz continuous wave. We both numerically and experimentally investigate the terahertz RCS of the metal plates and trihedral corner reflectors. The numerical simulations are obtained by using commercial software, i.e., computer simulation technology, which agree well with the experimental results. Then, the RCS of an aircraft scaled model is measured, and the experimental results are in good agreement with the physical characteristics of the scaled model. The effectiveness of our compact radar system is verified to get the RCS of complex targets, such as the scaled models of the tactical targets.

A frequency-tunable wireless access scheme based on optoelectronic oscillating technology is proposed and experimentally demonstrated. By using this scheme, the frequency of the transmitted wireless signals can be tuned by adjusting the wavelength of the input light. The 1.25 Gb/s on-off keying signals with the carrier frequency of 8–14.5 GHz are generated and transmitted through a radio over fiber link. The envelope detecting technique is employed in the receiver to support the down-conversion and demodulation. Electrical local oscillators are not required in the transmitter and receiver end, which simplifies the system structure and lowers the cost.

Real-time and high-resolution imaging is demonstrated based on field trial detection of a non-cooperative target using a photonics-based inverse synthetic aperture radar (ISAR). By photonic generation and de-chirping of broadband linear frequency modulation signals, the radar can achieve a high range resolution thanks to the large instantaneous bandwidth (8 GHz at the K band), as well as real-time ISAR imaging using low-speed analog-to-digital conversion (25 MSa/s). A small-size unmanned aerial vehicle is employed as the non-cooperative target, and ISAR imaging is realized with a resolution far better than those achieved by the previously reported photonics-based ISARs. The capability for real-time ISAR imaging is also verified with an imaging frame rate of 25 fps. These results validate that the photonics-based radar is feasible in practical real-time and high-resolution ISAR imaging applications.