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We propose the two-stage cascaded-tapered silica photonic crystal fiber (PCF) for the supercontinuum (SC) generation. The cascaded-tapered silica PCF is designed to have a spatial periodic structure. The physical scenarios of the spectral broadening due to the interaction between the structure-induced periodic dispersion and Kerr nonlinearity under different pulse widths and peak powers are investigated. It is found that when the pump pulses with width of

An ultra-short polarization beam splitter (PBS) based on a dual-core photonic crystal fiber (PCF) with the surface plasmon resonance effect is proposed. The finite-element method is used to investigate the coupling characteristics between the core mode and surface plasmon polariton mode. The influences of the PCF structure parameters on the coupling length and coupling length ratio are also investigated. The normalized output powers of the x-polarization and y-polarization are calculated, and the optimized PBS achieves an ultra-short length of 62.5 μm. The splitting bandwidth of 110 nm (1.51 to 1.61 μm) is achieved when the extinction ratio (ER) is less than −20 dB. The minimum ER reaches −71 dB at the wavelength of 1.55 μm. The proposed PBS has an important application in high-speed optical communication systems.

Continuous depth maps are reconstructed based on depth estimation from light-field data of axially distributed image sensing (ADS). In the proposed method, the light field of ADS is introduced, and the light-field trajectory function is presented, which formulates the relationship between image point positions in different axially captured images and the depth of object point. The depth value of an object is achieved by searching the light-field trajectory through statistical regression, which leads to an accurate depth estimation by making use of the structure information among the densely sampled views in light-field data. Moreover, as regions with smooth texture and occlusions do not contain reliable depth information, an energy minimization-based depth map optimization is carried out from initial estimations to obtain continuous and robust depth maps. Experimental results demonstrate that the reconstructed depth maps are accurate, continuous, and able to preserve more details. Moreover, the synthesized light-field images calculated by reconstructed depth map show good effect in 3D light-field display, and the validity of the proposed method is verified.

It is insufficiently powerful to compute multi-view images at a high enough frame or data rate to support high quality dynamic three-dimensional displays with the current computer software and hardware. According to the correspondence between lens position and elemental image, a real-time computer-generated content generation method for integral imaging based on cross perspective is presented. A GPU-driven rendering pipeline (GDRP) with geometry instancing and instance culling technique is designed, and the number of triangles processed in the rasterization stage is reduced greatly. Several virtual dynamic scenes including various materials and millions of vertices are used to verify the performance of the GDRP method in the experiment. Experimental results show that the frame rate can reach 60 fps with 3840 × 2160 resolution.

A polarization beam splitter (PBS) based on dual-core photonic crystal fiber (DC-PCF) with three layers of elliptical air holes is proposed. The full-vector finite element method is used to investigate the coupling and propagation characteristics of the PBS, and the three-dimensional beam propagation method is used to demonstrate the evolutions of the x-pol and y-pol light fields in cores A and B of the DC-PCF. In this design, the elliptical air holes are introduced to enhance the birefringence of the DC-PCF. The simulation results show that, with the proposed PBS, the complete beam splitting can be achieved at wavelength 1.55 μm when the fiber length is 254 μm. Moreover, when the extinction ratio is less than −20 dB, the bandwidth of the PBS can be up to 48 nm, covering the whole C-band. It is believed that the proposed PBS will be a promising candidate in laser and sensor systems.

A modified single-pass multiview rendering method is proposed to achieve real-time large viewing angle volume data three-dimensional (3-D) display. By modifying the volume rendering pipeline, the mapping of the synthetic image pixel and multiperspective information is directly accomplished in once rendering pass. And then shear-transformed ray is cast to integrate multiperspective information into the synthetic image used for 3-D display. Proof-of-concept experimental setups are constructed with the autostereoscopic 3-D display and the 3-D light-field display to demonstrate the proposed method without loss of generality. The experimental results show that the real-time frame rates of the autostereoscopic 3-D display and the 3-D light-field display are more than 30 and 60 fps at 4K (3840 × 2160) resolution, respectively. The rendering efficiency of the proposed method is irrespective of the viewpoint number and viewing angle size. In addition, it is not only compatible with the volume drawing pipeline but also robust to different types of 3-D displays based on pixel coding. A feasible way of applying 3-D display to the biological and medical fields is presented.

Floating three-dimensional (3-D) display can provide a natural and realistic 3-D scene. Nowadays, because of stray light and aberration, most floating 3-D displays cannot realize a large viewing angle and high resolution simultaneously, and it directly deteriorates the viewing effect of the 3-D scene. A large viewing angle floating and high-resolution 3-D display based on multichannel and multivariable (MCMV) correction algorithm are presented. The optical system consists of a time-sequential autostereoscopic 3-D display with the directional backlight, a floating lens, and an eye tracker. The 3-D display with the directional backlight provides loss-free resolution for the system. To realize a large viewing angle floating 3-D display, MCMV correction algorithm based on eye tracking is proposed. The 3-D images can be reconstructed by the optical system within the viewing angle of 60 deg. The feasibility of the proposed display method is verified with the experimental results.

The extreme computational complexity in generating a hologram makes the interactive holographic display very difficult. An optimized layered rendering method for real-time interactive holographic display based on ray-tracing technique is presented in order to overcome this challenge and realize real-time interaction of three-dimensional scenes. Ray tracing is able to render more complex and photorealistic images for different illuminations and circumstances. Rays are launched in parallel and traced to obtain ray–object intersections, and then the complex wave field of the effective pixels in different layers is determined. The occlusions between different layers are also considered to effectively reduce the overall computation. A computer-generated hologram is fused with the multilayer-hologram-diffraction results using the layered fast Fourier transform algorithm. The experimental results demonstrate the effectiveness of the proposed method. The reconstructed holographic image with real depth cues is demonstrated by the experiments, and the optical reconstruction images can be interacted in real-time.

We demonstrate an all-optical quantization scheme by slicing the supercontinuum (SC) generated in the normal dispersion region of a highly nonlinear fiber. The −20 dB bandwidth of the SC is broadened from 12.9 to 49.7 nm when input average power varies from 0.062 to 0.692 mW, which is used for realizing subsequent quantization. In addition, in order to evaluate the system performance, we have calculated the values of differential nonlinear error, integral nonlinear error, and effective number of bit from the experimental results as 0.471 least significant bit (LSB), 0.519 LSB, and 4.39 bit, respectively.

The all-optical differential equation solver has great potential in high-speed and wide-band signal processing, such as special waveform generation and description of the complex dynamics. We propose an all-optical differential equation solver in a silicon microring resonator with tunable constant coefficient k. Using inverse Raman scattering effect, k can be tunable by changing the power of the incident pump light. The influences of the pump power and signal pulse width on the tunable range of k are investigated. It is demonstrated that k is continuously tunable in the range of 0.035 / ps to 0.130 / ps with the error of

We propose an all-optical spectral quantization scheme based on soliton self-frequency shift (SSFS) and spectral compression (SC) in cascaded chalcogenide-silicon slot waveguides. The optical spectrum can be compressed to 13 nm after the process of SSFS. Simulation results show that the effective-number-of-bit of 4.966-bit can be improved by 2.076-bit compared with the scheme without SC.

The ultraviolet to visible continuum generations are experimentally demonstrated by coupling femtosecond pump pulses around 800 nm into the normal dispersion region close to the zero-dispersion wavelength in the fundamental mode of a silica photonic crystal fiber (PCF). The ultraviolet to visible continuum is generated through a combination of nonlinear effects including degenerate four-wave mixing, cross-phase modulation, and stimulated Raman scattering. When pump pulses with the wavelength of 800 nm and the input average power of 500 mW are used, more than 40% of the incident pump power is converted to the ultraviolet to visible spectral region. The evolution of the output spectra for different PCF lengths is studied to understand the nonlinear propagation dynamics during the process of the continuum generation. The ultraviolet to visible continuum generation will find important applications in the ultraviolet and visible-based biophotonics and spectroscopy.

We experimentally demonstrated the generation of dispersive waves (DWs) at the visible wavelength by coupling femtosecond pulses into the anomalous dispersion region of the second-order mode of a homemade photonic crystal fiber. When center wavelengths of the pump pulses are located at 800 and 850 nm and input average powers Pav are increased from 300, to 400, and to 500 mW, the blue-shifted DWs can be generated during the soliton dynamics and are tunable within the wavelength range of 614 to 561 nm. Moreover, the conversion efficiency ηDW of DWs is enhanced from 5% to 21%, and the corresponding bandwidth BDW is broadened from 17 to 30 nm. It is believed that the DWs can be used as the ultrashort pulse source for visible photonics and spectroscopy.

An alternative light source for coherent anti-Stokes Raman scattering (CARS) microspectroscopy based on red-shifted solitons in a polarization-maintaining photonic crystal fiber (PM-PCF) is experimentally demonstrated. By coupling femtosecond pulses into the anomalous dispersion region of the fundamental mode of a PM-PCF along the slow and fast axes, the red-shifted solitons generated can be used as the Stokes beams when the pump pulses are chosen as the pump beams. Through the process of red-shift, the frequency differences of the pump-Stokes beams are tunable in the ranges of 0 to 4068 cm−1 and 0 to 4594 cm−1, respectively. Moreover, because of the well maintained polarization states of the pump and Stokes beams and the high output powers of the solitons, CARS microspectroscopy using the proposed source will have a high signal-to-noise ratio and short data acquisition time. CARS microspectroscopy based on the proposed all-fiber light source can be used for studying a wide range of vibrational Raman spectra.

We propose a scheme for the real-time optical sampling of a multicast signal based on the parametric process. The linearly chirped and time-broadened pulses are used instead of the traditional mode-locked sampling pulses. The amount of signal copies or the rate of sampling train can be efficiently reduced by the chirped pulses while keeping a high-equivalent sampling rate. Simulation results show that the equivalent sampling rate of 120 GSa/s can be obtained by using only a sampling source of 10 GHz together with three signal copies. This scheme can efficiently improve the sampling rate in the real-time optical sampling and reduce the requirement on electronic devices for signal processing.

An effective speckle suppression method in digital holography is experimentally demonstrated with a wavelength-tunable coherent light source and a moving diffuser. Multiple off-axis digital holograms with different wavelengths and random phases are obtained. The Fresnel transformation algorithm is used to calculate the diffraction integral in the reconstruction. The speckle noise in the reconstructed images is suppressed by super- posing and averaging the intensity of multiple reconstruction images. Experiment results and the parameter evaluation show that the presented method is effective and feasible. © 2014 Society of Photo-Optical Instrumentation Here, a novel method for generating multiple holograms and suppressing speckle is presented. A wavelength-tunable coherent light source (LS) and a moving diffuser are used to generate multiple holograms with random phases (RP) and DWs. The intensity superposition and average of recon- structed images are performed to suppress the speckle noise. The DW intervals are experimentally used to generate holograms. The presented method of speckle suppression is compared with the random-phase intensity superposition and DWs in the experiment. The performance parameters are cal- culated and compared to demonstrate the effect of the speckle suppression.

Raman effect brings the inevitable limitation of gain flatness in the fiber-optical parametric amplifier even if the phase-matched condition is well satisfied. Phase-matched gain is modulated by the real part of Raman susceptibility especially when it is on the anti-Stokes side. The real part mainly determines the gain profile and limits the flat-gain bandwidth to be less than 180 nm. An asymmetric modulated gain spectrum appears due to the assistance of the imaginary part on the Stokes side. Simulation results also show that the single- and dual-pump configurations have different gain amplitude modulation factors induced by Raman.

With recent advances in high-speed computer and video capture technology, holographic films used in classical holography can be replaced with charged-coupled devices (CCD) and complementary metal-oxide-semiconductor (CMOS) image sensors to record and numerically reconstruct a hologram, which is now known as digital holography. Digital holography introduces something new to optical science. Wet chemical processing and other time-consuming procedures can be removed, so numerical recording and reconstruction can be realized in almost real time. It allows us to characterize the phase of a light field as well the intensity, and so the whole wave field can be measured and stored in a computer. Digital holography is expanding applications of holography and becoming a scientific and technological tool. Its use has now increased for measuring amplitude and the phase of object waves, displacement and three dimensional shape, particle distributions and motions, characterization of the refractive index and biological tissues, and vibration analysis, etc. Here, basic principles of digital holography for optical measurement and characterization are described. Taking into consideration the rapid advance in CCD and CMOS sensors as the background, the state-of-the-art applications of digital holography to optical measurement and characterization are presented.

The three-dimensional (3D) display based on the holographic functional screen is theoretically and experimentally presented. By properly designing the subholograms on the holographic functional screen, the whole 3D light field distribution can be recovered with the recorded angular spectra through the pinhole CCD camera array. The holographic functional screen is fabricated by the laser speckle method. Experimental results show that the fully continuous, natural 3D display is achieved without the limitations of conventional holography. Further improvements could lead to applications in industry, medical operation, military affairs, architecture design, mapping, and entertainment.