Showing papers by "Jinhui Yuan published in 2013"

Efficient red-shifted dispersive wave in a photonic crystal fiber for widely tunable mid-infrared wavelength generation

Abstract: Red-shifted dispersive waves (DWs) at the mid-infrared wavelengths are generated for the first time by pumping a photonic crystal fiber (PCF) with two zero dispersion wavelengths specially designed and fabricated in our laboratory, and the central wavelength of the soliton generated lies on the negative slope of the PCF dispersion profile. The experimental result shows that the conversion efficiency η of red-shifted DWs increases from 5 to 15% as the input power changes from 100 to 300 mW with the pump wavelength of 810 nm. By adjusting both the pump wavelength and power, the tunable range of the wavelength generated by red-shifted DWs can be over 100 nm.

Lumped Time-Delay Compensation Scheme for Coding Synchronization in the Nonlinear Spectral Quantization-Based All-Optical Analog-to-Digital Conversion

Abstract: In this paper, we propose a novel lumped time-delay compensation scheme for the all-optical analog-to-digital conversion based on soliton self-frequency shift and optical interconnection techniques. By inserting a segment of negative dispersion fiber between the quantization and the coding module, the time delay of different quantized pulses can be accurately compensated with a simple structure compared to the multiple time-delay lines. The simulation results show that the coding pulses can be well synchronized using a span of fiber, with the flattened negative dispersion within the wavelength range of 1558-1620 nm. In addition, the problems of pulse broadening and time error are discussed, and it is shown that no damage happens to the coding correctness within the sampling rate of 30 GSa/s.

Efficient and broadband Stokes wave generation by degenerate four-wave mixing at the mid-infrared wavelength in a silica photonic crystal fiber.

Abstract: Based on degenerate four-wave mixing (FWM), the broadband Stokes waves are efficiently generated at the mid-infrared wavelength above 2 μm, for the first time to our knowledge, by coupling the femtosecond pulses into the fundamental mode of a silica photonic crystal fiber designed and fabricated in our laboratory. Influences of the power and wavelength of pump pulses on the phase-matched frequency conversion process are discussed. When pump pulses with central wavelength of 815 nm and average power of 300 mW are used, the output power ratio of the Stokes wave generated at 2226 nm and the residual pump wave Ps/Pres is estimated to be 10.8∶1, and the corresponding conversion efficiency ηs and bandwidth Bs of the Stokes wave can be up to 26% and 33 nm, respectively. The efficient and broadband Stokes waves can be used as the ultrashort pulse sources for mid-infrared photonics and spectroscopy.

Coherent Anti-Stokes Raman Scattering Microscopy by Dispersive Wave Generations in a Polarization Maintaining Photonic Crystal Fiber

Abstract: The polarization maintaining photonic crystal flber (PM- PCF) with two zero dispersion wavelengths is designed and fabricated by the improved stack-and-draw technology in our laboratory. The broadband blue-shifted and red-shifted dispersive waves (DWs) are e-ciently generated from soliton self-frequency shift (SSFS) along the slow axis of PM-PCF. By optimizing the pump parameters and the flber length, the polarized DWs centered in the normal dispersion region can be used as the pump and Stokes pulses for the high resolution coherent anti-Stokes Raman scattering (CARS) microscopy. Moreover, it is demonstrated that the widely tunable relevant CARS wavelengths can be obtained by adjusting the pump wavelength. The CARS microscopy based on DWs can flnd important applications in detecting the biological and chemical samples with the C = N, S-H, C-H, and O-H stretch vibration resonances of 2100 to 2400cm i1 , 2500 to 2650cm i1 , 2700 to 3000cm i1 , and 3000 to 3750cm i1 .

Enhanced refractive index sensor using a combination of a long period fiber grating and a small core singlemode fiber structure

Abstract: An enhanced refractive index (RI) sensor based on a combination of a long period fiber grating (LPG) and a small core singlemode fiber (SCSMF) structure is proposed and developed. Since the LPG and SCSMF transmission spectra experience a blue and a red shift respectively as the surrounding RI (SRI) increases, the sensitivity is improved by measuring the separation between the resonant wavelengths of the LPG and SCSMF structures. Experimental results show that the sensor has a sensitivity of 1028 nm/SRI unit in the SRI range from 1.422 to 1.429, which is higher than individual sensitivities of either structure alone used in the experiment. Experimental results agree well with simulation results.

Widely tunable broadband deep-ultraviolet to visible wavelength generation by the cross phase modulation in a hollow-core photonic crystal fiber cladding

Abstract: The deep-ultraviolet (UV) to visible wavelengths are efficiently generated for the first time by the cross phase modulation (XPM) between the red-shifted solitons and the blue-shifted dispersive waves (DWs) in the fundamental guided mode of the multi-knots of a hollow-core photonic crystal fiber cladding (HC-PCFC). When the femtosecond pulses with a wavelength of 850 nm and average power of 300 mW are coupled into the knots 1–3, the conversion efficiency ηuv−v of 11% and bandwidth Buv−v of 100 nm in the deep-UV region are experimentally obtained. The multi-milliwatt ultrashort pulses are tunable over the deep-UV (below 200 nm) to visible spectral region by adjusting the wavelengths of the pump pulses in different knots. It is expected that these widely tunable broadband ultrashort deep-UV–visible pulse sources could have important applications in ultrafast photonics, femtochemisty, photobiology, and UV–visible resonant Raman scattering.

Efficient wavelength conversion based on quasi-phase-matched four-wave mixing in a silicon waveguide with a microring phase shifter

Abstract: An all-pass microring resonator is utilized in silicon waveguides to adjust the relative phase relationship among the involved waves in the degenerated four-wave mixing (FWM). By using the microring resonator as a phase shifter, the phase matching can be ameliorated, and the conversion efficiency can be enhanced effectively. The influences of key factors including the coupling strength of the ring resonator, and the nonlinear loss introduced by two-photon absorption and free carrier absorption, on the improvement of conversion efficiency are discussed. By properly selecting the parameters, the spectra of conversion efficiency are flattened in the wavelength range of 10 nm. Since the ring resonator has a periodic response spectrum and tunable resonant wavelength, the FWM with a microring phase shifter provides an efficient approach to wavelength conversion in silicon waveguides.

Optimization on bandwidth in the third-order pumped distributed fiber Raman amplifier

Abstract: The effect of higher-order amplified spontaneous scattering in Raman amplification is investigated With the effect, a structure of third-order distributed fiber Raman amplifier (DFRA) is introduced and its bandwidth is studied and optimized A method of multiorder pumps with multiwavelengths is adopted, which is different from that of multiwavelength pumps for the conventional DFRA Simulation results indicate that pumps in different orders have different functions: the first-order pump can improve the gain flatness and extend the bandwidth, the second-order pump can increase the gain value, whereas the third-order pump can provide powers for pumps in other orders and improve the noise figure (NF) together with them; a flat spectrum with the bandwidth of 80 nm, gain of 24 dB, ripple of less than 1 dB, and a low NF over a span of 120 km is achieved All these results are beneficial to design a broadband higher-order Raman pumping DFRA in future experimental work A modified genetic algorithm is also proposed in optimizing the bandwidth

Distance adaptive three-dimensional display based on mobile portable devices

Abstract: Three-dimensional (3D) display can offer the viewer the realism, which is the candidate for the next-generation imaging. 3D display technology without wearing glasses has become research focus. Currently the display of mobile devices is evolved towards 3D. Mobile devices limit the viewing range due to their mass production as well as the algorithm of relative fixity. Only in the area can be achieved a good viewing experience, which leads to the inconvenience for the viewer. The distance adaptive three-dimensional display based on mobile devices is presented. We analyzed the relationship between the viewing distance and the number of pixels for each viewpoint. Based on the viewing distance detected by sensor, the proposed method automatically adjusts the pixels for each viewpoint to accommodate different viewing distance for mobile portable devices. So the method realizes the adaptive distance between the viewer and the device, The experience of viewing 3D images is also improved, as well as the viewing areas is expanded. The crosstalk and the normalized brightness of the 3D picture after restructuring in different distance are measured. Experimental results show that the algorithm with matching parallax barrier can achieve a good 3D view experience at the different distances.

Polarization-dependent efficient Cherenkov radiation at visible wavelengths in hollow-core photonic crystal fiber cladding

Abstract: Efficient Cherenkov radiation (CR) is experimentally generated by a soliton self-frequency shift (SSFS) in a knot of hollow-core photonic crystal fiber (HC-PCF). When the angle of the half-wave plate is rotated from 0° to 45°, the Raman soliton shifts from 2227 to 2300 nm, the output power of the CR increases 8.15 times, and the maximum output power ratio of the CR at 556 nm to the residual pump is estimated to be 20:1. The width of the output optical spectrum at visible wavelengths broadens from 25 to 45 nm, and the conversion efficiency of the CR can be above 28%. Moreover, the influences of the pump polarization and wavelength on the CR are studied, and the corresponding nonlinear processes are discussed.

Investigation on a V-shape photonic crystal fiber with high birefringence and nonlinearity

Abstract: A highly birefringent and nonlinear photonic crystal fiber with a V-shape simplified structure is proposed and analyzed by the fully vectorial finite element method. It will have important applications in the nonlinear optics and biophotonics.

Design on a photonic crystal fiber with high nonlinearity and flattened dispersion for Raman soliton self-frequency shift

Abstract: A photonic crystal fiber (PCF) with high nonlinearity and flattened dispersion is designed. The structure of PCF is in a hexagon lattice. The larger air holes in the outer rings are used to confine the light field into the core region to enhance the nonlinearity, and the flattened dispersion can be achieved by adjusting the diameters of six smaller air holes in the first ring. By optimizing the sizes of the smaller and larger holes, the PCF can achieve high nonlinearity of 19 W -1 km -1 and low dispersion of 80.96 ps/(nm·km) with the fluctuation dispersion range of 8.49 ps/(nm·km) within the wavelength range of 1400 to 1800 nm. The PCF designed can find important applications in effectively realizing Raman soliton self-frequency shift and generating supercontinuum.

Characteristics of gain and pump-to-signal RIN transfer in a dual-pump SOPA with Raman effect

Abstract: We investigate the spectra of the gain and pump-to-signal relative intensity noise (RIN) transfer in silicon optical parametric amplifier (SOPA) with Raman effect, and draw a conclusion that Raman effect makes the spectra narrower from 260 nm to 180 nm. A maximum gain also appears at 1622 nm. Moreover, the effects of the related parameters in SOPA on the gain and the pump-to-signal RIN transfer characteristics are also discussed. The high gain (16 dB) and low pump-to-signal RIN transfer (7 dB) can be obtained by using the appropriate parameters of pump and silicon waveguide.

A Novel Time-delay Compensation Scheme Utilizing a Linearly Chirped Fiber Bragg Grating in Photonics Analog-to-digital Conversion

Abstract: We propose a novel lumped time-delay compensation scheme for coding synchronization. By the characteristics of a linearly chirped fiber Bragg grating, the time-delay of different quantized pulses can be accurately compensated with a simple structure

Complete Power Conversion in the Cascaded Fiber Optical Parametric Amplifier by Inserting the Idler-Phase-Shifters

Abstract: A novel gain enhancement scheme for the fiber-optic parametric amplifiers is reported in this paper. By inserting the idler-phase-shifters among several segments of highly nonlinear fibers, complete power conversion of pump-to-signal can be obtained.

Study on Extinction Ratio of 4-RZ-ASK Signal Generated by Optical Parametric Amplification

Abstract: Extinction ratio of 4-RZ-ASK signal generated by optical parametric amplification is studied. It is demonstrated that the extinction ratio of input signal and pump power have significant effects on the extinction ratio of output signal.