All-Optical Sampling Using Nonlinear Polarization Rotation in a Single Semiconductor Optical Amplifier

We propose a novel all-optical sampling method using nonlinear polarization rotation in a semiconductor optical amplifier. A rate-equation model capable of describing the all-optical sampling mechanism is presented in this paper. Based on this model, we investigate the optimized operating parameters of the proposed system by simulating the output intensity of the probe light as functions of the input polarization angle, the phase induced by the polarization controller, and the ori- entation of the polarization beam splitter. The simulated results show that we can obtain a good linear slope and a large linear dynamic range,which is suitable for all-optical sampling. The operating power of the pump light can be less than lmW. The presented all-optical sampling method can potentially operate at a sampling rate up to hundreds GS/s and needs low optical power.

An Electroabsorption Modulator Monolithically Integrated with a Semiconductor Optical Amplifier and a Dual-Waveguide Spot-Size Converter

A semiconductor optical amplifier and electroabsorption modulator monolithically integrated with a spotsize converter input and output is fabricated by means of selective area growth,quantum well intermixing,and asymmetric twin waveguide technology. A 1550-1600nm lossless operation with a high DC extinction ratio of 25dB and more than 10GHz 3dB bandwidth are successfully achieved. The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3°× 18.0°, respectively, resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.

Design of Tensile Strained InGaAsP/InGaAsP MQW for 1.55μm Polarization Independent Semiconductor Optical Amplifier

The theoretical optimization of tensile strained InGaAsP/InGaAsP MQW for 1.55μm windows polarization-independent semiconductor optical amplifier is reported.The valence-band structure of the MQW is calculated by using k·p method,in which 6×6 Luttinger effective-mass Hamiltonian is taken into account.The polarization dependent optical gain is calculated with various well width,strain,and carrier density.

1550nm Polarization-Insensitive Semiconductor Optical Amplifier Based on AlGaInAs-InP

Polarization insensitive AlGaInAs InP semiconductor optical amplifier is realized at a wavelength of 1550nm.The active layer consists of three tensile strained wells with strain 0 40%.The amplifiers are fabricated to ridge waveguide structure with 7° tilted cavity.The two facets are coated with two layers of anti reflection Ti 3O 5/Al 2O 3 films.Residual facet reflectivity is found to be less than 0 03%.The semiconductor optical amplifer exhibits 20dB of signal gain and 7 2dBm of saturation output power with an excellent polarization insensitivity (less than 0 8dB) at 200mA and 1540nm window.

Wide-Band Polarization-Independent Semiconductor Optical Amplifier Gate with Tensile-Strained Quasi-Bulk InGaAs

A semiconductor optical amplifier gate based on tensile strained quasi bulk InGaAs is developed.At injection current of 80mA,a 3dB optical bandwidth of more than 85nm is achieved due to dominant band filling effect.Moreover,the most important is that very low polarization dependence of gain (<0 7dB),fiber to fiber lossless operation current (70～90mA) and a high extinction ratio (>50dB) are simultaneously obtained over this wide 3dB optical bandwidth (1520～1609nm) which nearly covers the spectral region of the whole C band (1525～1565nm) and the whole L band (1570～1610nm).The gating time is also improved by decreasing carrier lifetime.The wide band polarization insensitive SOA gate is promising for use in future dense wavelength division multiplexing (DWDM) communication systems.

Optical properties and local structure of Dy^(3+)-doped chalcogenide and chalcohalide glasses

Dy^3＋-doped Ge-Ga-Se chalcogenide glasses and GeSe2-Ga2Se3-CsI chalcohalide glasses were prepared. The absorption, emission properties, and local structure of the glasses were investigated. When excited at 808 nm diode laser, intense 1.32 and 1.55 μm near-infrared luminescence were observed with full width at half maximum （FWHM） of about 90 and 50 nm, respectively. The lifetime of the 1.32 μm emission varied due to changes in the local structure surrounding Dy^3＋ ions. The longest lifetime was over 2.5 ms, and the value was significantly higher than that in other Dy^3＋-doped glasses. Some other spectroscopic parameters were calculated by using Judd-Ofelt theory. Meanwhile, Ge-Ga-Se and GeSe2-Ga2Se3-CsI glasses showed good infrared transmittance. As a result, Dy^3＋-doped Ge-Ga-Se and GeSe2-Ga2Se3-CsI glasses were believed to be useful hosts for 1.3 μm optical fiber amplifier.

Photonic generation of power-efficient FCC-compliant ultra-wideband waveforms using semiconductor optical amplifier (SOA):theoretical analysis and experiment verification

We theoretically design a power-efficient ultra-wideband pulse generator by combining three monocycle pulses with different weights. We also experimentally demonstrate a feasible scheme to generate such power-efficient ultra-wideband waveforms using cross-phase modulation in a single semiconductor optical amplifier. The designed ultra-wideband pulse fully satisfies the requirements for the spectral mask specified by the Federal Communications Commission with high power efficiency. In the experiment, a power-efficient ultra-wideband waveform with a pulse duration of 310 ps is achieved, and the power efficiency is greatly improved compared with that of a single nlonocycle pulse or a mixture of two monoeycles.

Quantum-dot Semiconductor Optical Amplifiers in State Space Model

A state space model(SSM) is derived for quantum-dot semiconductor optical amplifiers(QD-SOAs).Rate equations of QD-SOA are formulated in the form of state update equations,where average occupation probabilities along QD-SOA cavity are considered as state variables of the system.Simulations show that SSM calculates QD-SOA′s static and dynamic characteristics with high accuracy.

Towards 640 Gbit/s wavelength conversion based on nonlinear polarization rotation in a semiconductor optical amplifier

Taking into account ultra-fast carrier dynamics, this paper models 640 Gbit/s wavelength conversion scheme based on nonlinear polarization rotation （NPR） in a single semiconductor optical amplifier （SOA） and investigates the performance of this kind of wavelength conversion scheme in detail. In this model, two carrier temperature equations are introduced to substitute two energy density equations, which reduce the complexity of calculation in comparison with the previous model. The temporary gain and phase shift dynamics induced by ultra-short optical pulses are numerically simulated and the simulated results are qualitatively in good agreement with reported experimental results. Simulated results show that non-inverted and inverted 640 Gbit/s wavelength conversions based on NPR are achieved with clear open eye diagrams. To further investigate the performance of the non-inverted wavelength conversion scheme, the dependence of output extinction ratio （ER） on some key parameters used in simulation is illustrated. Furthermore, simulated analyses show that high performance non-inverted wavelength conversion based on NPR can be achieved by using a red-shifted filtering scheme.

Device Design and Characteristics for SOA-basedAll Optical Signal 2R Regeneration

A new scheme based on SOA-MZI for all-optical 2R regeneration is proposed. The characteristics of gain and switching window of this device are investigated in detail. Numerical simulation results indicate that the nonlinear gain compression, the time delay between the input optical signal and the width of the optical pulse are essential parameters for a good performance of all-optical 2R regeneration.

Photonic multi-shape UWB pulse generation using a semiconductor optical amplifier-based nonlinear optical loop mirror

We propose and demonstrate a scheme to implement photonic multi-shape ultra-wideband（UWB） signal generation using a semiconductor optical amplifier（SOA） based nonlinear optical loop mirror（NOLM）.By employing the cross phase modulation（XPM） effect,cross gain modulation（XGM）,or both,multi-shape UWB waveforms are generated including monocycle,doublet,triplet,and quadruplet pulses.Both the shapes and polarities of the generated pulses are flexible to adjust,which may be very useful in UWB pulse shape modulation and pulse polarity modulation.

Semiconductor Optical Amplifier and Gain Chip Used in Wavelength Tunable Lasers

The design concept of semiconductor optical amplifier(SOA)and gain chip used in wavelength tunable lasers(TL)is discussed in this paper.The design concept is similar to that of a conventional SOA or a laser;however,there are a few different points.An SOA in front of the tunable laser should be polarization dependent and has low optical confinement factor.To obtain wide gain bandwidth at the threshold current,the gain chip used in the tunable laser cavity should be something between SOA and fixed-wavelength laser design,while the fixed-wavelength laser has high optical confinement factor.Detailed discussion is given with basic equations and some simulation results on saturation power of the SOA and gain bandwidth of gain chip are shown.

Entanglement of movable mirror and cavity field enhanced by an optical parametric amplifier

A scheme to generate entanglement in a cavity optomechanical system filled with an optical parametric amplifier is proposed. With the help of the optical parametric amplifier, the stationary macroscopic entanglement between the movable mirror and the cavity field can be notably enhanced, and the entanglement increases when the parametric gain increases.Moreover, for a given parametric gain, the degree of entanglement of the cavity optomechanical system increases with increasing input laser power.

High-Stability High-Energy Picosecond Optical Parametric Chirped Pulse Amplifier as a Preamplifier in Nd：Glass Petawatt System for Contrast Enhancement

We demonstrate a novel picosecond optical parametric preamplification to generate high-stability, high-energy and high-contrast seed pulses. The 5ps seed pulse is amplified from 60pJ to 300μJ with an 8.6ps/ 3mJ pump laser in a signal stage of short pulse non-collinear optical parametric chirped pulse amplification. The total gain is more than 106 and the rms energy stability is under 1.35%. The contrast ratio is higher than 10s within a scale of 20ps before the main pulse. Consequently, the improvement factor of the signal contrast is approximately equal to the gain 106 outside the pump window.

Optimization of regenerator based on semiconductor optical amplifier for degraded differential phase shift keying signal

Real time phase regeneration is necessary for degraded phase modulation format optical communication systems. A regenerator based on the discrimitive gain effect of a semiconductor optical amplifier was proposed in recent years. In this paper, for this type of regenerator, its optimal working condition is found by solving the dynamic equations which describe the variance of the optical field and carrier density in the semiconductor optical amplifier by the finite difference method. The results show that the optimal improvement of signal Q factor can reach more than 2.2 dB.

Analytic approach to the small-signal frequency response of saturated semiconductor optical amplifiers using multisection model

An analytic solution derived by multisection model to the small-signal frequency response （SSFR） of wavelength conversion based on cross-gain modulation （XGM） in semiconductor optical amplifiers （SOAs） is presented. The result contains details that can affect the characteristics of SSFR significantly more than previous ones.

Semiconductor optical amplifier used as regenerator for degraded differential phase-shift keying signals

Phase and amplitude regeneration are necessary for degraded differential phase-shift keying communication sys- tems. This paper proposes a regenerator based on semiconductor optical amplifier for differential phase-shift keying signals. The key regeneration mechanism is theoretically analysed. The effectiveness of semiconductor optical amplifier based regenerator is demonstrated by comparing the bit error rate and eye diagrams before and after regeneration for 40-Cbit/s differential phase-shift keying 1080-km transmission systems. The results show that regeneration effects are very well. Bit error rate is tess than 10-12 with the regenerator.

All-optical XNOR and AND gates simultaneously realized in a single semiconductor optical amplifier with improved dynamics

All-optical XNOR and AND logic gates using four-wave mixing （FWM） and cross-gain modulation （XGM） in a single semiconductor optical amplifier （SOA） with improved dynamics are simultaneously realized. By numerical simulation, the effects of the input optical wave powers and injection current on the critical factors of the logic gate performances, such as the ON-OFF contrast ratio, the power-output level of the logic ＇1＇, and the difference between power outputs of the logic ＇1＇, are investigated in detail. In addition, the effect of the counter-propagating CW pump on the gain recovery is analysed.

Amplification of fluorescence using collinear picosecond optical parametric amplification at degeneracy

We demonstrate the output characteristic of broadband parametric amplification of incoherent light pulses in a 355-nm pumped degenerate picosecond optical parametric amplification with either saturated or unsaturated amplification. The optical parametric amplifier is seeded by the fluorescence generated in a solution of pyridine-1 dye in ethanol. With the saturated amplification, we can obtain high energy incoherent light pulses, whose full width at half maximum bandwidth varies from 16 nm to 53 nm for the different phase matching angles near degeneracy. Moreover, the unsaturated bandwidth of the amplified pulses fits well to the calculated result at degeneracy. Selecting s-polarized fluorescence with a Glan-Taylor prism, the maximum bandwidth of the amplified fluorescence is found to be 59 nm for a purely s-polarized seed. The maximum output energy is 0.67 mJ for the optical parametric amplifier. By using an optical filter and compressor, the generated high energy incoherent light has great potential as the incoherent pump, signal or idler wave of a parametric down-conversion process, so that a wave with a high degree of coherence can be generated from an incoherent pump light.

Einstein-Podolsky-Rosen entanglement in time-dependent periodic pumping non-degenerate optical parametric amplifier

The solution of the time-dependent periodic pumping non-degenerate optical parametric amplifier （NOPA） is derived when the pump depletion is considered both above and below thresholds. Based on this solution, the quantum fluctuation calculated shows that a high entanglement and a good squeezing degree of the parametric light beams are achieved near and above thresholds. We adopt two kinds of pump fields： （i） a continuously modulated pump with a sinusoidal envelope; （ii） a sequence of laser pulses with Gaussian envelopes. We analyse the time evolution of continuous variable entanglement by analytical and numerical calculations, and show that the periodic driven pumping also improves the degree of entanglement. The squeezing and Einstein-Podolsky-Rosen （EPR） entanglement by using the two pumping driven functions are investigated from below to above the threshold regions, the tendencies are nearly the same, and the Caussian driven function is superior to that of the sine driven function, when the maximum squeezing and the minimum variance of quantum fluctuation are considered. In the meantime, the generalization of frequency degenerate OPA to frequency non-degenerated OPA problem is investigated.