Semiconductor Laser Amplifier Research Articles

Analysis of erasable fiber loop optical buffer

In this paper, we propose a model of a fiber loop buffer, which incorporates a semiconductor laser amplifier (SLA) as nonlinear element controlled by an optical control signal. The impact of the accumulated and amplified spontaneous emission noise of the SLA and data pattern dependent gain saturation effect in the SLA on the properties of the buffer is taken into account to give the optimum operation conditions theoretically.

All-optical switching in an angled-grating semiconductor Bragg amplifier

We propose an all-optical switching element based on forward Bragg diffraction in a periodically corrugated semiconductor laser amplifier. The device geometry is similar to that of an angled-grating distributed-feedback (/spl alpha/-DFB) laser except that there is no reflective feedback. Light induced changes in the refractive index cause the output to switch from a cross state to a bar state with input power levels of only a few milliwatts.

Modeling of NOLM demultiplexers employing optical soliton control pulse

An optical soliton pulse may be used as a control signal in non-linear optical loop mirror demultiplexers in order to reduce timing-jitter noise and cross-talk. A mathematical model for calculating the width of the soliton switching window and optimizing critical parameters such as walk-off time and pulse width has been presented, and its accuracy is verified by solving the non- linear Schrodinger equation. Key word: Semiconductor laser amplifier, optical switching, soliton, optical time division demultiplexer, optical loop mirrors.

THEORETICAL ANALYSIS OF NONDEGENERATE FOUR-WAVE MIXING IN SEMICONDUCTOR LASER AMPLIFIERS

Theoretical analysis and numerical solution of several physical mechanisms on nondegenerate four-wave mixing(NDFWM) in semiconductor laser amplifiers are presented. Starting from the general carrier rate equation, density-matrix equations and nonlinear wave equations, considering the effects of carrier-density pulsations, carrier heating, and spectral-hole burning, we obtained three sets of nonlinear coupled wave equations, and compared the contributions of the three different physical mechanisms to the NDFWM. We also investigated the effect of linewidth enhancement factor on the conversion efficiency of the NDFWM in semiconductor laser amplifiers.

TUNABLE FREQUENCY-SELECTIVE CONVERTER FOR HIGH-SPEED DWDM SYSTEMS

A kind of tunable frequency-selective converter based on nondegenerate four-wave mixing (ND-FWM) in semiconductor laser amplifier (SLA) is proposed in this paper.The coupling model of the frequency-selective converter in SLA is established first,and then the converting mechanism and characteristics are analyzed.The influences of its property parameters on the output efficiency,and the frequency shift are primarily discussed.And the property of the output noise of the frequency-se-lective converter has been studied as well.The superior performance of the converter,such as short response time,high conversion efficiency,and large conversion range,makes it favorable for use in DWDM networks where high speed and tunableness are required.

Demonstration of optical noise reduction using nonlinear absorption in a semiconductor laser amplifier

We propose a new way to use a semiconductor laser amplifier driven under a loss condition for a signal light that acts as an ultrafast noise reduction device using a nonlinear absorption effect. The absorption recovery time was reduced by stimulated recombination due to continuous-wave additional light (assist light) whose wavelength was longer than that of the signal. This simple method is an attractive technique to realize optical functional devices with an ultrahigh-repetition rate. We have successfully confirmed a receiver sensitivity improvement of 0.5 dB in a 5-Gb/s nonreturn-to-zero signal by using this principle. The improvement of the eye opening by passing through the noise reduction device was estimated theoretically to reveal design rules for an optimum optical noise reduction device.

The modulation response of a semiconductor laser amplifier

We present a theoretical analysis of the modulation response of a semiconductor laser amplifier. We find a resonance behavior similar to the well-known relaxation oscillation resonance found in semiconductor lasers, but of a different physical origin. The role of the waveguide (scattering) loss is investigated in detail and is shown to influence the qualitative behavior of the response. In particular, it is found that a certain amount of waveguide loss may be beneficial in some cases. Finally, the role of the microwave propagation of the modulation signals is investigated and different feeding schemes are analyzed. The nonlinear transparent waveguide, i.e., an amplifier saturated to the point where the stimulated emission balances the internal losses, is shown to be analytically solvable and is a convenient vehicle for gaining qualitative understanding of the dynamics of modulated semiconductor optical amplifiers.

Time-domain modeling of semiconductor optical amplifiers for OTDM applications

An advanced time-domain dynamical model for the investigation of semiconductor optical amplifiers (SOA) is presented. The model accounts for the ultrafast gain dynamics, the gain saturation and the gain spectral profile. It is also suitable for analyzing the amplifier in a system environment. As an example the model is used to investigate the gain dynamics of an SOA as well as the characteristics of an interferometer switch semiconductor laser amplifier in a loop mirror (SLALOM). Good agreement between modeling and experiment is shown. The model can be applied to the investigation of other optically time-division multiplexed (OTDM) applications, too.

A novel analytical expression of saturation intensity of InGaAsP tapered traveling-wave semiconductor laser amplifier structures

We have proposed a novel approximate analytical expression for saturation intensity for tapered traveling-wave semiconductor laser amplifier structures. The application of this analytical expression of saturation intensity has been demonstrated by considering the effect of gain saturation on polarization sensitivity of two tapered amplifier structures, linear and exponential tapered amplifier structures. It is found that polarization sensitivity of the tapered amplifier structure is several decibels higher than that of passive tapered waveguides in unsaturated condition. Polarization sensitivity of the two tapered amplifier structures has also been investigated in a highly saturated condition. The combined effects of mode conversion and gain saturation on fundamental TE gain have also been investigated using the proposed analytical expression for saturation intensity.

Distributed optical contention resolution using an optical token-ring

A novel distributed contention resolution using a token-ring for N/spl times/N photonic ATM or packet switching system is proposed. This method uses distributed optical data processing, to improve the switching capacity and link speed of a photonic switch. The token reduction part, the key function of the proposed method, was realized using a semiconductor laser amplifier loop mirror. Experimentally, a pulse in a 2.5 Gb/s token made of 50-ps full-width at half-maximum optical pulses was successfully eliminated and the extinction ratio was -6.85 dB.

Carrier-carrier interaction and ultrashort pulse propagation in a highly excited semiconductor laser amplifier beyond the rate equation limit

Carrier-carrier interaction and ultrashort pulse propagation in a highly excited semiconductor laser amplifier beyond the rate equation limit

Carrier diffusion effect in tapered semiconductor-laser amplifier

This paper proposes a theoretical model to study the beam amplification and the influence of the lateral drift and diffusion on the tapered semiconductor-laser amplifier in great detail. The overall effect of the lateral drift and diffusion could be represented by an effective diffusion coefficient. The analysis, which treats the effective diffusion coefficient as a controllable parameter, shows that both the beam quality and optoelectrical property can be improved using a large effective diffusion coefficient. The analysis also indicates that the effective diffusion in the separate-confinement heterostructure layer could affect the beam quality in the quantum-well amplifiers. In addition, the thermal effect on the device performance is studied and its influence is found to be extremely significant for the high-diffusion cases.

Analysis of all-semiconductor intracavity optical parametric oscillators

We propose a novel scheme for efficient parametric generation of mid-IR light by use of an optical cavity, incorporating a semiconductor nonlinear medium and a semiconductor laser amplifier. We evaluate theoretically the threshold and the conversion efficiency of the proposed scheme and show its advantages over conventional optical parametric oscillators.

Mechanism for reducing recovery time of optical nonlinearity in semiconductor laser amplifier

We propose and demonstrate a novel scheme to reduce the recovery time of optical nonlinearity in a semiconductor laser optical amplifier driven under a loss condition for the signal light pulse. Additional light, which is set at a transparency wavelength in the active layer, promotes stimulated recombination of excess carriers induced by the absorption of the signal light. This scheme excludes any additional carrier transport mechanism and nonradiative recombination and hence generation of heat. The principle of operation is experimentally verified by measuring time-domain transmission variance using a pump–probe method. A drastic reduction of the excess-carrier lifetime to less than 70 ps was confirmed.

High-brightness tapered semiconductor laser oscillators and amplifiers with low-modal gain epilayer-structures

The dependence of the beam quality of tapered laser oscillators and amplifiers on the modal optical gain is demonstrated experimentally and theoretically for the first time. Tapered devices with high- (HMG) and low-modal gain (LMG) structures are compared in terms of output power and beam quality. At high-output powers the beam quality of LMG devices is by a factor of ten better than the beam quality of high-modal gain devices. The beam quality remains nearly unchanged up to power levels of more than 2-W continuous-wave (CW) where a beam quality factor of M/sup 2/<3 is achieved for both, tapered laser oscillators and tapered amplifiers.

Wavelength measurement and tracking using semiconductor laser amplifiers for applications in photonic networks

Novel approaches for wavelength measurement and tracking using semiconductor laser amplifiers (SLA's) are proposed. The variation of the transparent current of a SLA with the wavelength of an incident light is utilized for wavelength discrimination. The principles, response speed, and resolution of these approaches are addressed. Experimental data show that optical frequencies that are 2.15 GHz apart can be resolved.

Harmonic and intermodulation distortion analysis by perturbation and harmonic balance methods for in-line photodetection in a semiconductor optical amplifier

Harmonic and intermodulation distortion in a semiconductor laser amplifier (SOA) used as an in-line photodetector is predicted, by using the harmonic balance technique and the perturbation method. Experimental and theoretical results are presented up to the third order.

Analytic theory of coherent cross-gain modulation in semiconductor travelling-wave amplifiers

We report a simple analytic solution to the problem of cross amplitude-phase modulation in nonlinear two-wave mixing, under the approximation of constant saturating power. The results are applied to travelling-wave semiconductor laser amplifiers where the linewidth enhancement factor inevitably leads to amplitude-phase coupling and asymmetric energy transfer. Our solution is used to obtain the transmission gain of each beam, the spectral profile and the amplifier input-output characteristics. Limits are established as to the applicability of the analytic solution, by comparison with numerical solutions to the related full four-wave mixing problem.

Analytic theory of coherent cross-gain modulation in semiconductor travelling-wave amplifiers

Abstract We report a simple analytic solution to the problem of cross amplitude-phase modulation in nonlinear two-wave mixing, under the approximation of constant saturating power. The results are applied to travelling-wave semiconductor laser amplifiers where the linewidth enhancement factor inevitably leads to amplitude-phase coupling and asymmetric energy transfer. Our solution is used to obtain the transmission gain of each beam, the spectral profile and the amplifier input-output characteristics. Limits are established as to the applicability of the analytic solution, by comparison with numerical solutions to the related full four-wave mixing problem.

Wide-range tunable semiconductor lasers using asymmetric dual quantum wells

Using asymmetric dual quantum wells for the laser material, the semiconductor lasers are broadly tunable. In a grating coupled ring cavity, the semiconductor laser is continuously tunable from 766 to 856 nm using a 400-μm semiconductor laser amplifier in the cavity. This letter also demonstrates that the grating coupled ring cavity could well eliminate the amplified stimulated emission noise and about 40-dB amplified spontaneous emission (ASE) suppression ratio is obtained over the entire tuning range.