Semiconductor Laser Amplifier Research Articles

Modeling and numerical simulation of the gain spectrum of Thulium-doped broadband fiber amplifiers

Nowadays, due to the complex signal medium conversion process of semiconductor laser amplifiers, the optical fiber amplifier, which is a new type of all-optical amplifier, is increasingly used in optical fiber communication lines for signal amplification because it can directly perform all-optical amplification of signals and are especially suitable for relay amplification of long-distance optical communications. Our research project is the gain spectrum of the Thulium-doped broadband fiber amplifier. The signal wavelength range is from to . The goal is to obtain the gain spectrum with fiber length variation, doping concentration, and pump power. This paper follows a logical order that presents the introduction, the formulas used in the experiment, and the result and analysis. According to the output wavelength range, energy level structure, and electronic transition process, we designed the pump wavelength and established the rate and power propagation equations. Eventually, gain spectrum with a variation of fiber length, doping concentration, and pump power is available using MATLAB for programming and calculating. With our research achievement, a more efficient optical fiber amplifier is possible to be made in the future.

Development of frequency comb generation by spectral broadening of periodic optical pulses in semiconductor laser amplifiers

This paper reports an approach for generating an ultra-flat and ultra-wide optical frequency comb by exploiting gain modulation, experienced by a periodic third ordered Gaussian-shaped optical pulse propagating through the semiconductor optical amplifier (SOA). The gain experienced by optical signal propagating inside SOA is independent of its polarization state and phase, makes the technique more favorable and stable to the optical frequency comb generation. This paper reports a 94-line optical frequency comb with 5 dB maximum power deviation and a 190-line optical frequency comb with 10 dB maximum power deviation.

Temperature-dependency performance of InGaAsP semiconductor laser amplifiers

We report a theoretical analysis on the influence of operation temperature on the static and dynamic properties of an InP/InGaAsP semiconductor Laser amplifier (SLA). We use a numerical wideband steady-state model and numerical algorithm, to study the (I-P) curves, gain bandwidth, noise figure, outpout noise power and outpout OSNR in a range between - 20 °C and 100 °C. InP/InGaAsP SLA exhibited a thershold curent as low as 55mA at 100 °C and the characteristic temperature (T0) of the SLA was found to be 142.8 0C, which confirms the high temperature operation of the device. Moreover, the results show that InP/InGaAsP SLA can cover 3dB operating at signal wavelengths between 1.54µm and 1.58µm with gains of up to 25dB at -20 0C. This peak slightly decreases with temperature. Furthermore, a high out power saturation of 7 dB was exhabited at -20 °C and a low noise figure of around 2.8 dB was achieved in the deviece. Finally, our model shows the elegant performance of InGaAsP/InP SLA in the range between -20 °C and 100 °C, which makes it a promising candidate for integrated photonics.

Antireflection coated semiconductor laser amplifier for Bose-Einstein condensation experiments

We present a slave laser highly suitable for the preparation and detection of 87Rb Bose-Einstein condensates (BEC). A highly anti-reflection coated laser diode serves as an optical amplifier, which requires neither active temperature stabilization nor dedicated equipment monitoring the spectral purity of the amplified light. The laser power can be controlled with a precision of 10 μW in 70 mW with relative fluctuations down to 2 × 10−4. Due to its simplicity and reliability, this slave laser will be a useful tool for laboratory, mobile, or even space-based cold-atom experiments. By the way of demonstration this slave laser was used as the sole 780 nm light-source in the production of 3 × 104 BECs in a hybrid magnetic/dipole trap.

Time-delayed behaviors of transient four-wave mixing signal intensity in inverted semiconductor with carrier-injection pumping

An analytical expression of transient four-wave mixing (TFWM) in inverted semiconductor with carrier-injection pumping was derived from both the density matrix equation and the complex stochastic stationary statistical method of incoherent light. Numerical analysis showed that the TFWM decayed decay is towards the limit of extreme homogeneous and inhomogeneous broadenings in atoms and the decaying time is inversely proportional to half the power of the net carrier densities for a low carrier-density injection and other high carrier-density injection, while it obeys an usual exponential decay with other decaying time that is inversely proportional to half the power of the net carrier density or it obeys an unusual exponential decay with the decaying time that is inversely proportional to a third power of the net carrier density for a moderate carrier-density injection. The results can be applied to studying ultrafast carrier dephasing in the inverted semiconductors such as semiconductor laser amplifier and semiconductor optical amplifier.

Rabi oscillations in a room-temperature quantum dash semiconductor optical amplifier

Quantum coherent light-matter interactions have been at the forefront of scientific interest since the fundamental predictions of Einstein and the later work of Rabi. Direct observation of quantum coherent interactions entails probing the electronic wavefunction which requires that the electronic state of the matter does not de-phase during the measurement, a condition that can be satisfied by lengthening the coherence time or by shortening the observation time. The short de-phasing time in semiconductors has dictated that all coherent effects reported to date have been recorded directly only at cryogenic temperatures. Here we report on the first direct electronic wavefunction probing in a room-temperature semiconductor. Employing an ultrafast characterization scheme we have demonstrated Rabi oscillations and self-induced transparency in an electrically driven, room-temperature semiconductor laser amplifier, revealing the most intimate details of the light-matter interactions seen to date. The ability to employ quantum effects in solid-state media, which operate at elevated temperatures, will finally bring true quantum mechanical concepts into the realm of practical devices.

Simultaneous multiple channel all-optical NRZ to CSRZ and RZ to CSRZ format conversion using an SOA-NOLM

The optical conversion bandwidth for an all-optical modulation format converter, based on a semiconductor laser amplifier in a nonlinear optical loop mirror (SOA-NOLM), is investigated. 4×10Gbit/s channels are all-optically converted between both non-return-to-zero (NRZ) and return-to-zero (RZ) format to carrier-suppressed return-to-zero (CSRZ). WDM transmission of the converted signals over a 194km fibre span is then demonstrated. The receiver sensitivity for the converted four wavelengths is measured and compared after transmission.

Large area single-mode parity–time-symmetric laser amplifiers

By exploiting recent developments associated with parity-time (PT) symmetry in optics, we here propose a new avenue in realizing single-mode large area laser amplifiers. This can be accomplished by utilizing the abrupt symmetry breaking transition that allows the fundamental mode to experience gain while keeping all the higher order modes neutral. Such PT-symmetric structures can be realized by judiciously coupling two multimode waveguides, one exhibiting gain while the other exhibits an equal amount of loss. Pertinent examples are provided for both semiconductor and fiber laser amplifiers.

Analytically describing pulse deformation arising from frequency dependent filling factor of wave guide amplifiers

After neglecting the frequency dependence of the material gain, the analytical expressions to the output pulses from the amplifier for the input pulses of sinc-type and Gaussian have been derived. According to the derived results, the pulse deformation arising from frequency dependent filling factor can be analyzed: for the sinc-type pulse train, the light intensity peak remains unchanged, but the valleys between the output pulse peaks cannot touch the zero floor anymore; For the Gaussian pulse, the amplifier will impose a frequency shift on the pulse, which is proportional to the first derivative of the filling factor ( Γ 1). Another, the analytical expression of Γ 1 for the semiconductor laser amplifier has been derived. And the calculated result shows that Γ 1 is a positive quantity, and the magnitude of it is about 10 −3/nm. The result indicates that Γ 1 is an important parameter for theoretical describing the pulse deformation of wave guide amplifier such as the ps and fs pulse amplifier.

Nonlinear semiconductor lasers and amplifiers for all-optical information processing

The nonlinear properties of semiconductor lasers and laser amplifiers when subject to optical injection are reviewed and new results are presented for multisection lasers, vertical cavity semiconductor optical amplifiers, and surface-emitting lasers. The main underlying material parameters are outlined and the key design approaches are discussed for both edge-emitting and vertical cavity devices. An overview of theoretical modeling approaches is discussed and a summary of key experimental results is presented. The practical use of optically injected edge-emitting and vertical cavity semiconductor lasers and laser amplifiers is illustrated with examples of applications including, among others, optical logic and chaotic communication.

Switching Behavior of Bistable DFB Semiconductor Laser Amplifiers

In this article, we have proposed a procedure to analyze transient response of bistable distributed feedback semiconductor laser amplifiers. The results of the analysis show that among bistable distributed feedback semiconductor laser amplifiers with uniform, quarter wavelength phase-shifted, and tapered gratings, the latter has the best switching behavior. This behavior includes relaxation oscillation, switching-on time, and switching-off time of the output pulse for an input pulse. Transfer matrix and the finite difference time-domain methods are utilized for numerical simulation.

Experimental determination of the thermal lens parameters in a broad area semiconductor laser amplifier

Due to the build-up of temperature gradients along their width, semiconductor laser diodes tend to be affected by thermal lensing effects. We propose a simple and easy-to-implement experiment in order to determine the thermal lens coefficient in a broad area semiconductor laser amplifier during operation. The results obtained are compared to simulations of the temperature distribution in the laser structure. In order to further validate our method, we compare the measured M2 value of a free running broad area laser diode with the calculated M2 of such a laser under the influence of a thermal lens as predicted by diffraction theory of first-order optical resonators. The experimental results are seen to be in good agreement with the calculations.

Steady state analysis of optical bistability in distributed coupling coefficient DFB semiconductor laser amplifiers

In this paper, optical bistability behavior in a distributed feedback (DFB) semiconductor laser amplifier (SLA), with nonuniform-grating is studied. The investigation is focused on distributed coupling coefficient (DCC) structures, in which the corrugation has a nonuniform depth along the cavity. A modified implementation of transfer-matrix method, which takes the longitudinal variation of coupling coefficient along the structure into account, and considers gain saturation, is utilized to examine switching characteristics of DCC DFB SLA’s in the steady state regime. Along with the wavelength dependence of bistability hysteresis, the structural dependence of switching performance in these devices is demonstrated. Low-power switching spectral range and ON–OFF contrast ratio is investigated and the results are discussed.

Improvement of transmission in fibre wireless system using semiconductor laser amplifier

Improvement in performance of fibre wireless systems using a semiconductor laser amplifier is experimentally demonstrated. The presented approach improves receiver sensitivity by over 4.5 dB by increasing the depth of optical modulation. The approach can support long-distance fibre-wireless systems.

Analysis of high bit rate operation of a vertically gain-clamped semiconductor laser amplifier

A detailed theoretical model of the high bit rate operation of a vertically gain-clamped semiconductor optical amplifier with high bit rate return-to-zero and non-return-to-zero input signals is presented. It is shown that good eye opening at 10–40 GBit/s can be achieved at sufficiently high operating currents (hundreds of mA in a realistic construction). A resonance between the relaxation oscillations of the vertical laser and the bit rate of the input signal is detrimental to the amplifier performance and should be avoided. When designing the length of the amplifier, a trade-off exists between the eye opening and the average gain.

Concept of internal mixing in semiconductor lasers and optical amplifiers for room-temperature generation of tunable continuous terahertz waves

We discuss the potential for creating a tunable continuous-wave source for the 1–5 THz frequency range based on nonlinear mixing in the active medium of a dual-color semiconductor laser or laser amplifier. Our analysis for the 1.55 μ m wavelength regime shows that intracavity mixing, after minimization of THz waveguide losses and optimization of the second-order nonlinearity of the active medium, should provide up to 100 μ W of THz power at an optical power of 100 mW per color.

Tapered grating effects on static properties of a bistable QWS-DFB semiconductor laser amplifier

Using the steady-state model based on the coupled-mode and carrier rate equations, in this paper, we analyze the effects of trapezoidal tapered gratings on the dispersive bistable characteristics of a quarter wavelength phase-shifted distributed feedback semiconductor laser amplifier (QWS-DFB-SLA). We also compare the results with those of a purely QWS-DFB-SLA. For laser amplifiers driven to yield the same unsaturated peak amplifier gain, trapezoidal taper widens the spectral range of low-threshold bistable switching and increases the on–off switching contrast. The transfer-matrix method (TMM) is utilized for the numerical simulations.

A simple spice model for traveling wave semiconductor laser amplifier

AbstractAn equivalent lumped element electric circuit model for traveling wave semiconductor laser amplifier has been developed using the rate equation for carriers. SPICE simulation of the circuits gives results in close agreement with the experimental data and values from sophisticated analyses. The modulation bandwidth and transient response were examined by including parasitic elements in the intrinsic model. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1558–1561, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22483

Two-wavelength switching with 1550 nm semiconductor laser amplifiers

Feature Issue on Photonics in SwitchingTwo-wavelength switching operation between two signals at different wavelengths is reported using the optical bistability occurring in two different semiconductor laser amplifiers. With this technique an optical signal can be set in either of the optical input wavelengths by appropriate choice of the powers of the input signals. Switching of a signal beam by another control beam at different wavelength is reported experimentally with a 1550 nm distributed feedback semiconductor optical amplifier. Also, a theoretical model has been generated to analyze the wavelength switching operation with a novel amplifier type--the 1550 nm vertical cavity semiconductor optical amplifier (VCSOA). Using a 1550 nm VCSOA, wavelength switching operation is reported with a calculated input power below 1 μW. This low input power requirement for switching added to the high-frequency response of the VCSOA, and the ease of fabricating 2D arrays of these devices due to the vertical structure, makes the VCSOA a very interesting device for use in optical switching applications in the optical telecommunication networks.

Investigation of the polarization dependence of the characteristics of a semiconductor laser amplifier in a loop mirror for all-optical pattern conversion

A complete analytical model of the polarization characteristics of a semiconductor laser amplifier in a loop mirror (SLALOM) is presented. Based on this model, various kinds of output for all-optical conversion of non-return-to-zero (NRZ) to pseudo-return-to-zero (PRZ) signals, based on a simple SLALOM scheme, are analyzed theoretically. Simulation results were in good agreement with experimental results on 20-Gbit/s all-optical NRZ-to-PRZ conversion. The results show that the theoretical model proposed in this paper is right, and proper polarization-state control is helpful for improving the output characteristics in all-optical pattern conversion.