Terahertz optical asymmetric demultiplexer based tree-net architecture for all-optical conversion scheme from binary to its other 2^n radix based form

To exploit the parallelism of optics in data processing, a suitable number system and an efficient encoding/decoding scheme for handling the data are very essential. In the field of optical computing and parallel information processing, several number systems like binary, quaternary, octal, hexadecimal, etc. have been used for different arithmetic and algebraic operations. Here, we have proposed an all-optical conversion scheme from its binary to its other 2^n radix based form with the help of terahertz optical asymmetric demultiplexer （TOAD） based tree-net architecture.

Optical Analog-to-digital Conversion Scheme Based on Tunable Fabry-Perot Resonator

Proposed is an interference type of optical analog-to-digital conversion(ADC). The refractive index of Fabry-Perot cavity changes with different voltages. The Fabry-Perot resonator converts electronic intensity into light wavelength through selecting lights of different wavelengthes. The parameters of the scheme are acquired with the transmission matrix of optical element and the time of steady-state light field. The maximum sampling speedes of 4-bit, 6-bit, 7-bit, 8-bit and 9-bit(ADC) are 1.695×1010 count/s, 4.33×109 count/s, 2.38×109 count/s, 1.24×109 count/s and 5.9×108 count/s, respectively.

High-energy picosecond single-pass multi-stage optical parametric generator and amplifier

We demonstrate a new management of multi-stage optical parametric generator(OPG)and amplifier(OPA)to obtain high-energy picosecond sources with high beam quality.The setup of multi-stage OPG-OPA requires mode-matching between the pump beam and the stable mode of the OPG-OPA.In a proof-of-principle experiment,the single-pass multi-stage OPG-OPA consists of three walk-off compensated KTP crystal pairs and two lenses,pumped by an 86 ps,1064 nm 10 kHz picosecond laser.The signal light at~1.77μm has an average output power of 502 mW with record energy up to 50.2μJ.The beam quality factor of the signal light can be improved toM^(2)_(x) ×M^(2)_(y)after filtering out about 40%signal power.To the best of our knowledge,it is the first picosecond single-pass multi-stage OPG-OPA pumped at kHz regime.

Cascaded four-wave mixing all-optical wavelength converter based on highly nonlinear fiber deposited graphene oxide

The all-optical wavelength conversion using cascaded four-wave mixing(FWM)phenomena with graphene oxide(GO)and a highly nonlinear fiber(HNLF)device is demonstrated experimentally.GO has a strong third-order nonlinear effect and is an excellent nonlinear optical material for nonlinear optical wavelength conversion.The group velocity matching of pump and signal,HNLF,and GO amplification promote the cascaded nonlinear frequency mixing process.From the experimental and analytical results,the maximum spacing between signal and pump is 21 nm,and specifically,the order of cascaded FWM light increases from order 1 to order 2 with increasing GO,and the first-order FWM conversion effi-ciency increases to a maximum of−14.5 dB.To the best of our knowledge,this is the first time that cascaded FWM-based all-optical wavelength conversion in HNLF-GO with wide wavelength selectivity is investigated with combined pump and signal light.Our findings not only provide an effective method for achieving all-optical wavelength conversion in cascaded FWM but also offer the possibility of fabricating high-performance nonlinear optical devices.

Efficiency-enhanced picosecond mid-infrared optical parametric downconversion based on a cascaded optical superlattice

We demonstrate an efficiency-enhanced picosecond （ps） mid-infrared radiation via optical parametric downconversion. Based on a cascaded periodically poled MgO-doped stoiehiometric lithium tantalate crystal （MgO：sPPLT）, a tandem optical parametric oscillation-optical parametric amplification （OPO-OPA） process is achieved. Compared with a single OPO process, the conversion efficiency obtains an enhancement of 71%.

All-optical NRZ-to-AMI conversion using linear filtering effect of silicon microring resonator

We experimentally demonstrate 10-Gb/s format conversion from non-return-to-zero （NRZ） to alternatemark-inversion （AMI） using the linear filtering effect of silicon microring resonator. Our discussion and analysis in simulation further show that a 10-Gb/s AMI signal with good quality can be obtained by a resonator with a notch depth larger than 25 dB when the 3-dB bandwidth is 0.4 nm.

Multi-Wavelength Conversion Using FP-LD with Linear Optical Amplifier

We propose and demonstrate a multi-wavelength converter using FP-LD with linear optical amplifier (LOA) which based on cross-gain modulation can convert an input signal to many wavelengths simultaneously for reconfigurable wavelength conversion in OXC and broadcasting in WDM systems.

All-optical NRZ wavelength conversion using a Sagnac loop with optimized SOA characteristics

We investigated the all-optical wavelength conversion technique for non-return-to-zero（NRZ） signals based on a Sagnac loop interferometer using an SOA. For the wavelength conversion of the NRZ signal at and above40 Gbit/s, we used an in-house numerical SOA model to analyze the influence of the SOA carrier characteristics and the SOA length on the performance of the Sagnac loop. We found that the SOA carrier recovery time should be between 2 and 3 times of one bit duration in order to get optimum NRZ wavelength conversion. In addition to the carrier recovery time requirement, SOAs with a shorter physical length are preferred to be used in the Sagnac interferometer.

Mutual optical format conversion between on-of keying and binary phase-shift keying based on stimulated brillouin scattering

We propose and experimentally demonstrate mutual optical format conversion between signals characterized as 10-Gb/s nonreturn-to-zero on-of-keying(NRZ-OOK) and NRZ binary phase-shift keying(BPSK) types. The conversion is based on stimulated Brillouin scattering(SBS) in a single-mode optical fber. An OOK signal is converted into a BPSK signal through optical carrier absorption, for which a SBS loss of 30 MHz is used in long-haul transmission. The converted BPSK signal is reverted to an OOK signal with a corresponding SBS gain of 30 MHz for direct detection. The proposed OOK-to-BPSK and BPSK-to-OOK format conversions can be implemented in transmitter and receiver nodes by using a laser source as the Brillouin pump.

Optical Wavelength Filter Using Mode Conversion in Multimode Waveguide

A wavelength filter with simple structure using multimode waveguide is proposed. The device uses mode conversion by a grating structure fabricated simultaneously with the multimode waveguide.

Theoretical study of all-optical NRZ to RZ format conversion with tunable pulse width based on XPM in a silicon waveguide

An all-optical format conversion from non-return-to-zero （NRZ） to return-to-zero （RZ） is presented based on cross-phase modulation （XPM） in a silicon waveguide with a detuned optical bandpass filter （OBPF）. The simulation results show that the tunable bandwidth of the OBPF leads.to RZ signals with tunable pulse width. The conversion efficiency （CE） and the pattern effect of the RZ signal are attributed to the parameters of the pump pulse and the OBPE The converted RZ signal exhibits lower timing jitter than the NRZ signal.

A periodically poled LiNbO_3 optical parametric generator in wavelength conversion from 2 to 3.88——4.34 μm

A periodically poled lithium niobate （PPLN） optical parametric generator （OPG） pumped by a laser diode （LD）-pumped Q-switched Tm,Ho：GdVO4 laser operated at 2.048 μm with pump pulse of 25 ns and repetition rate of 10 kHz is reported. A continuous tunable middle-infrared （mid-IR） spectrum of 3.88 - 4.34 μm is obtained by changing the crystal temperature from 50 to 124℃. When the incident pump power is 3 W, the total OPG output power is 95 mW, corresponding to optical conversion efficiency of 3.2%.

Analysis of ultra-broadband high-energy optical parametric chirped pulse amplifier based on YCOB crystal

A new type of optical parametric chirped pulse amplifier is designed and analyzed for the amplification of pulse centered at 808 nm. A novel crystal, yttrium calcium oxyborate YCa40（BO3）3 （YCOB）, is utilized in the power amplification stage of optical parametric amplification （OPA）. Noncollinear phase matching parameters in the xoz principle plane of YCOB, compared with those in BBO and DKDP, are analyzed by numerical simulation. The results show that YCOB rather than DKDP can be used in the power amplification stage of OPA to realize the amplification of chirped pulse to several joules with a gain bandwidth exceeding 100 nm. This can be used to gain a high intensity pulse of -10 fs after the compressor.

Experiment study of wavelength conversion in a dispersion-flattened photonic crystal fiber

Wavelength conversion based on four-wave mixing （FWM） has been demonstrated using a 40-m dispersion flattened highly nonlinear photonic crystal fiber （HNL-PCF）. A conversion efficiency of -26 dB for a pump power of 19.5 dBm and a conversion bandwidth of 28 nm have been obtained, which are limited by the continuous wave （CW） laser wavelength range and tunability of optical band pass filters （OBPFs）.

Widely continuous-tunable 2.789-4.957 μm twin-MgO:PPLN cascaded optical parametric oscillator

An all-solid-state mid-infrared optical parametric oscillator with wide tunability by using two identical multi-grating periodically poled 5-mol.-% MgO-doped lithium niobate cascaded is reported. The pump laser is an acousto-optically Q-switched Nd：YAG laser with 150-ns pulse width at repetition rate of 10 kHz. Wide tunability from 2.789 to 4.957μm at the idler wavelength is achieved by varying the temperature from 40 to 200 ~C and translating the grating periods from 26 to 31 μm with a step of 0.5μm. When the incident pump average power is 8.15 W, the maximum idler output average power is 2.23 W at 3.344 μm and the optic-optic conversion efficiency is about 27.4%.

High-average-power,high-repetition-rate dual signal optical parametric oscillator based on PPMgLN

A high-average-power,high-repetition-rate dual signal optical parametric oscillator based on periodically poled MgO-doped lithium niobate（PPMgLN） with a phase-reversed grating is reported.The pump laser is an acousto-optically Q-switched Nd：YVO_4 laser with a maximum average power of 7.6 W.When the repetition rate is 50 kHz and the pulse width of the pump source is 23 ns,the maximum average dual signal output power is about 1.9 W,leading to a conversion efficiency of 25%.Over a 30-min interval,the instability of the signal power measured is less than 0.5%.

Novel high-sensitivity coherent transceiver for optical DPSK/DQPSK signals based on heterodyne detection and electrical delay interferometer

We present a novel coherent transceiver for optical differential phase-shift keying/differential quadrature phase-shift keying （DPSK/DQPSK） signals based on heterodyne detection and electrical delay interferometer. A simulation framework is provided to predict a theoretical sensitivity level for the reported scheme. High sensitivity of –45.18 dBm is achieved for 2.5-Gb/s return-to-zero （RZ）-DPSK signal, and high sensitivities of –36.83 dBm （I tributary） and –35.90 dBm （Q tributary） are observed for 2.5-GBaud/s RZ-DQPSK signal in back-to-back configuration. Transmission for both signals over 100 km is also investigated. Experimental results are discussed and analyzed.

Numerical analysis for four-wave mixing based wavelength conversion of differential phase-shift keying signals

We numerically investigate the main constrains for high efficiency wavelength conversion of differential phase-shift keying （DPSK） signals based on four-wave mixing （FWM） in highly nonlinear fiber （HNLF）. Using multi-tone pump phase modulation techniques, high efficiency wavelength conversion of DPSK signals is achieved with the stimulated BriIlouin scattering （SBS） effects effectively suppressed. Our analysis shows that there is a compromise between conversion efficiency and converted idler degradation. By optimizing the pump phase modulation configuration, the converted DPSK idler＇s degradation can be dramatically decreased through balancing SBS suppression and pump phase modulation degradation. Our simulation results also show that these multi-tone pump phase modulation techniques are more appropriate for the future high bit rate systems.

Wavelength conversion of chaotic message through gain modulation by injection-locked Fabry-Perot laser diode

We propose a wavelength conversion scheme for chaotic optical communications（COC） based on a Fabry-Perot （FP） laser diode.The FP laser,as a wavelength converter,is injection-locked at one of longitudinal modes by an external continuous-wave（CW） light.The simulation results demonstrated that the chaos masked signal at wavelengthλ_1,which corresponds to the other longitudinal mode of FP laser,can be converted to the injection-locked mode（wavelengthλ_2） based on cross-gain modulation in a closed-loop COC link.A 1.2-GHz chaos masked sinusoidal signal is successfully decoded with signal-to-noise ratio （SNR） beyond 8 dB in 15-nm wavelength conversion range,and the effects of SNR on the signal frequency and conversion span are also investigated.

Optical properties and CO_2 laser SHG with HgGa_2S_4

Optical properties and nonlinearity on phase-matching (PM) of two (yellow and orange) phase crystals were investigated in details. Damage threshold was determined in comparison with middle infrared (IR) crystal at identical experimental conditions. Second harmonic generation (SHG) of 30 ns TEA CO2 laser pulses was realized with 5% efficiency in energy and 6.9% in peak power.