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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. [ABSTRACT FROM AUTHOR]

In this paper, a novel silicon-on-insulator (SOI) waveguide with the multiperiod vertical grating is proposed to realize broadband parametric wavelength conversion with a quasi-phase matching technique. The grating period in the former part of the SOI waveguide is optimized to enhance the conversion efficiency at designated signal wavelength and the 3-dB bandwidth. When the continuous-wave pump at 1550 nm is used, the conversion efficiency of -14.0 dB at 1750 nm and the 3-dB bandwidth of 387 nm can be obtained. Compared to the constant-width waveguide, the improvements of 26.7 dB and 298 nm are achieved, respectively. The results show that this SOI waveguide is an ideal device for broadband wavelength conversion without dispersion engineering. [ABSTRACT FROM AUTHOR]

All-optical analog-to-digital converters based on the third-order nonlinear effects in silicon waveguide are a promising candidate to overcome the limitation of electronic devices and are suitable for photonic integration. In this paper, a 2-bit optical spectral quantization scheme for on-chip all-optical analog-to-digital conversion is proposed. The proposed scheme is realized by filtering the broadened and split spectrum induced by the self-phase modulation effect in a silicon horizontal slot waveguide filled with silicon-nanocrystal. Nonlinear coefficient as high as 8708 W-1/m is obtained because of the tight mode confinement of the horizontal slot waveguide and the high nonlinear refractive index of the silicon-nanocrystal, which provides the enhanced nonlinear interaction and accordingly low power threshold. The results show that a required input peak power level less than 0.4 W can be achieved, along with the 1.98-bit effective-number-of-bit and Gray code output. The proposed scheme can find important applications in on-chip all-optical digital signal processing systems. [ABSTRACT FROM AUTHOR]

Higher-order solitons are formed by coupling femtosecond pulses into the fundamental mode of a highly nonlinear silica photonic crystal fiber (HNL-SPCF) fabricated in our laboratory. It is experimentally observed that the higher-order solitons break up into a series of stable and broadband discrete fundamental solitons at the mid-infrared wavelength longer than 2000 nm through the process of soliton self-frequency shift due to the perturbations induced by the higher-order dispersive and nonlinear effects. The maximum soliton red-shift and the tunable wavelength range can be up to 1600 nm and over 400 nm, respectively. The nonlinear dynamic processes of femtosecond pulse breakup are consistent with the solution of the generalized nonlinear Schrödinger equation. This multiple stable and broadband mid-infrared wavelengths generated in such an HNL-SPCF can be used as all-fiber multiwavelength ultrashort pulse sources for multiphoton microscopy and ultrafast photonics. [ABSTRACT FROM PUBLISHER]

A visible region of interest (ROI) extraction method based on region expansion is proposed. It is a method that is combined with a new reverse realization of calibration based on homography. The proposed method extracts the ROI automatically and successfully and simultaneously calibrates the distortion caused by the stereoscopic camera system. It is a practical and easy method because it does not require any extra processing before display. It can be used to discard the confusing margin of the synthesized image of several parallax images and reduce the data amount needed to be processed and encoded. Here, real-time capturing, transmitting, and three-dimensional displaying systems are demonstrated to verify its effectiveness and feasibility. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 superposing and averaging the intensity of multiple reconstruction images. Experiment results and the parameter evaluation show that the presented method is effective and feasible. [ABSTRACT FROM AUTHOR]

The polarization maintaining photonic crystal fiber (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 efficiently generated from soliton self-frequency shift (SSFS) along the slow axis of PM-PCF. By optimizing the pump parameters and the fiber 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 find 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 2400 cm-1, 2500 to 2650 cm-1, 2700 to 3000 cm-1, and 3000 to 3750 cm-1. [ABSTRACT FROM AUTHOR]

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 dualpump configurations have different gain amplitude modulation factors induced by Raman. [ABSTRACT FROM AUTHOR]

The dual-pump all-optical wavelength conversion based on a four-wave mixing (FWM) in a high-nonlinear dispersion shifted fiber (HNL-DSF) is demonstrated experimentally. The polarization sensitivity of the wavelength converter based on this dual-pump figuration is investigated experimentally and theoretically. The experimental results indicate that the wavelength-conversion configuration with copolarization pumps shows the smallest polarization sensitivity. A model of the beating-wave modulation from the dynamic wave equation is erected to explain the experimental phenomena, and the theoretical analyses agree well with the experimental results. [ABSTRACT FROM PUBLISHER]

We demonstrate dual-wavelength short pulses lasing at 1540 and 1675 nm based on a silicon waveguide. The inline silicon waveguide inside a laser cavity facilitates pulse compression and laser mode-locking due to two-photon absorption (TPA) and TPA-induced free-carrier absorption at 1540 nm. Compressed pulses provide pump for stimulated Raman scattering. Raman amplification and low threshold Raman lasing are observed based on the same silicon waveguide. [ABSTRACT FROM PUBLISHER]

A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber (PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio (ER) of lower than –20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of –279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems. [ABSTRACT FROM AUTHOR]

A chemical sensor based on a Bragg grating in the multimode fiber has been demonstrated experimentally. Experimental results indicate that the reflection peak of high-order mode P2 exhibits a much higher concentration sensitivity of the chemical solution than the reflection peak P1 of the high-order mode. The sensor has been used to measure the concentrations of propylene glycol solutions and sugar solutions, which could detect 0.05% and 0.04% concentration change for them with the wavelength interrogation module of 1-pm resolution. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1739–1741, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21761 [ABSTRACT FROM AUTHOR]

Anti-Stokes signals at the near-ultraviolet wavelength are efficiently generated based on degenerate four-wave mixing by coupling the femtosecond pulses into the fundamental mode of a photonic crystal fibre. When the pump pulses with the central wavelength of 840 nm and the average power of 300 mW are used, the conversion efficiency ηs of the anti-Stokes signal at 432 nm can be up to 40%, and the pulse width is measured to be 42 fs by the Talbot effect. [ABSTRACT FROM AUTHOR]

In this paper, we propose an integratable spectral quantization scheme for all-optical analog-to-digital conversion (AOADC) by slicing the supercontinuum, which is generated in a chalcogenide (As2S3) horizontal slot waveguide. The numerical simulation results show that a 4-bit quantization resolution is successfully achieved along with a signal-to-noise ratio of 23.96 dB and an effective number of bit (ENOB) of 3.98 bit. The required As2S3 waveguide length and input peak power are only 1.5 cm and 900 mW, respectively, owing to the high nonlinear coefficient of 115.8 W−1/m. It is believed that this proposed scheme can find important applications in the photonic integratable AOADC with low power consumption. [ABSTRACT FROM AUTHOR]

A photonic crystal fiber (PCF) is fabricated from silica material purified by the complexing method of rectification and adsorption in our laboratory. The parameters of pump pulses and fiber length are optimized in the experiment, and the nonlinear optical process of the high-order soliton generation is studied. The high peak power continuums at the mid-infrared wavelength are generated by the overlap among the high-order soliton peaks. Specifically, when a PCF with a length of 60 cm is used, the conversion efficiency η and bandwidth B of the continuum generated can be up to 65% and 358 nm, and the corresponding peak power Ppeak-o and pulse width Wp are 144 kW and 30 fs. It is believed that the high peak power and broadband mid-infrared continuum can be used as short pulse sources, which will find important applications in biophotonics and ultrafast science and technology. [ABSTRACT FROM AUTHOR]

The properties of an all-optical parametric amplifier (OPA) based on four-wave-mixing (FWM) in a silicon microring resonator (MR) side-coupled to a bus waveguide are investigated. The influences of microring structural parameters on amplification performance are analyzed in the presence of two-photon absorption (TPA) and free carrier absorption (FCA) caused by TPA. The simulation results show that, due to the field enhancement, an OPA inside an MR can achieve similar net gain with a much smaller waveguide and lower pump power compared with that based on a straight waveguide. [ABSTRACT FROM AUTHOR]

Gain and Noise figure (NF) characteristics in dual-pump parametric amplifier based on silicon on insulator (SOI) Rib waveguides are numerically investigated in the presence of nonlinear losses. The impact of structure parameters of the silicon optical parametric amplifiers (SOPAs) on the gain and the NF are also analyzed. The results show that both the height and the width of the silicon on insulator (SOI) can affect the gain and the NF of SOPAs. 354nm bandwidth (3dB) and 8.135 maximum gain can be achieved by tailoring the structure parameters of the SOI rib waveguides. Moreover, the dispersion and the effective mode area of SOI are also analyzed. [ABSTRACT FROM AUTHOR]

Broadband supercontinuums (SC) are generated by soliton self-frequency shift (SSFS) of hollow-core photonic crystal fiber (HC-PCF) in our laboratory. With the pump works at 810nm when the pump power increase from 400 to 600mW, the Raman Soliton shifts from 2089 to 2215nm, the bandwidth of SC increases from 2213 to 2320nm. The ultra-violet part of SC is below 180nm, and the mid-infrared part of SC exceeds 2500nm. Moreover, the influence of pump power on SC is also analyzed. [ABSTRACT FROM AUTHOR]