Broadband polarization-insensitive semiconductor optical amplifier gate with tensile InGaAs quasi-bulk and compressively strained InGaAs wells

A novel wideband polarization-insensitive semiconductor optical amplifier (SOA) gate containing compressively strained InGaAs quantum wells and tensile-strained InGaAs quasi-bulk layers is developed. The fabricated SOA gates have a wide 3-dB optical bandwidth of 102 nm, less than 0.8-dB polarization sensitivity, more than 50-dB extinction ratio, and less than 75-mA fiber-to-fiber lossless operating current. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

Wide-band polarization-insensitive high-output-power semiconductor optical amplifier based on thin tensile-strained bulk InGaAs

A polarization-insensitive semiconductor optical amplifier (SOA) with a very thin active tensile-strained InGaAs bulk has been fabricated. The polarization sensitivity of the amplifier gain is less than 1 dB over both the entire range of driving current and the 3 dB optical bandwidth of more than 80 nm. For optical signals of 1550 nm wavelength, the SOA exhibits a high saturation output power +7.6 dBm together with a low noise figure of 7.5 dB, fibre-to-fibre gain of 11.5 dB, and low polarization sensitivity of 0.5 dB. Additionally, at the gain peak 1520 nm, the fibre-to-fibre gain is measured to be 14.1 dB.

Monolithically integrated semiconductor optical amplifier and electroabsorption modulator with dual-waveguide spot-size converter input and output

We have demonstrated an electroabsorption modulator and semiconductor optical amplifier monolithically integrated with novel dual-waveguide spot-size converters (SSC) at the input and output ports for low-loss coupling to a planar light-guide circuit silica waveguide or cleaved single-mode optical fibre. The device was fabricated by means of selective-area MOVPE growth, quantum well intermixing and asymmetric twin waveguide technologies with only a three-step low-pressure MOVPE growth. For the device structure, in the SOA/EAM section, a double ridge structure was employed to reduce the EAM capacitances and enable high bit-rate operation. In the SSC sections, buried ridge structure (BRS) was incorporated. Such a combination of ridge, ATG and BRS structure is reported for the first time in which it can take advantage of easy processing of the ridge structure and the excellent mode characteristic of BRS. At the wavelength range of 1550-1600 nm, lossless operation with extinction ratios of 25 dB dc and more than 10 GHz 3 dB bandwidth is successfully achieved, The beam divergence angles of the input and output ports of the device are as small as 8.0 degrees x 12.6 degrees, resulting in 3.0 dB coupling loss with a cleaved single-mode optical fibre.

Lossless electroabsorption modulator monolithically rntegrated with a semiconductor optical amplifier and dual-wavegulde spot-size converters

Semiconductor optical amplifier and electroabsorption modulator monolithically integrated with dual-waveguide spot-size converters at the input and output ports is demonstrated by means of selective area growth, quantum-well intermixing, and asymmetric twin waveguide technologies. At the wavelength range of 1550 similar to 1600 nm, lossless operation with extinction ratios of 25-dB dc and 11.8-dB radio frequency and more than 10-GHz 3-dB modulation bandwidth is successfully achieved. The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3 degrees x 10.6 degrees, respectively, resulting in 3.0-dB coupling loss with cleaved single-mode optical fiber.

Numerical and theoretical analysis of the crosstalk in linear optical amplifiers

The dynamic characteristics, including the crosstalk and relaxation oscillation, of linear optical amplifiers (LOAs) are investigated by small-signal analysis under an averaging carrier density approximation and compared with the results of numerical simulation. The good agreement between the numerical simulation and the small-signal analysis indicated the averaging carrier density is an appropriate approximation for analyzing LOAs. Theoretical analyzes also show that the dynamic properties of the vertical laser fields dominate the dynamic performance of LOAs. Based on the small-signal analysis, a concise equation for the crosstalk under high bit rate was derived, which can be applied to measure the differential gain of LOAs.

Electroabsorption modulated semiconductor optical amplifier monolithically integrated with spot-size converters

We have demonstrated an electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) monolithically integrated with novel dual-waveguide spot-size converters (SSCs) at the input and output ports for low-loss coupling to planar light-guide circuit silica waveguide or cleaved single-mode optical fiber. The device is fabricated by means of selective-area MOVPE growth (SAG), quantum well intermixing (QWI) and asymmetric twin waveguide (ATG) technologies with only three steps low-pressure MOVPE growth. For the device structure, in SOA/EAM section, double ridge structure was employed to reduce the EAM capacitances and enable high bit-rate operation. In the SSC sections, buried ridge stripe (BRS) were incorporated. Such a combination of ridge, ATG and BRS structure is reported for the first time in which it can take advantage of both easy processing of ridge structure and the excellent mode characteristic of BRS. At the wavelength range of 1550-1600 nm, lossless operation with extinction ratios of 25 dB DC and more than 10 GHz 3-dB bandwidth is successfully achieved. The beam divergence angles of the input and output ports of the device are as small as 8.0 degrees x 12.6 degrees, resulting in 3.0 dB coupling loss with cleaved single-mode optical fiber. (c) 2005 Elsevier B.V. All rights reserved.

Semiconductor optical amplifier optical gate with graded strained bulk-like active structure

A novel semiconductor optical amplifier (SOA) optical gate with a graded strained bulk-like active structure is proposed. A fiber-to-fiber gain of 10 dB when the coupling loss reaches 7 dB/factet and a polarization insensitivity of less than 0.9 dB for multiwavelength and different power input signals over the whole operation current are obtained. Moreover, for our SOA optical gate, a no-loss current of 50 to 70 mA and an extinction ratio of more than 50 dB are realized when the injection current is more than no-loss current, and the maximum extinction ratio reaches 71 dB, which is critical for crosstalk suppression. (C) 2003 society of Photo-Optical Instrumentation Engineers.

High energy ion implantation enhanced intermixed quantum well structures and their absorption characteristics in passive optical waveguides

We have shown that high energy ion implantation enhanced intermixing (HE-IIEI) technology for quantum well (QW) structures is a powerful technique which can be used to blue shift the band gap energy of a QW structure and therefore decrease its band gap absorption. Room temperature (RT) photoluminescence (PL) and guided-wave transmission measurements have been employed to investigate the amount of blue shift of the band gap energy of an intermixed QW structure and the reduction of band gap absorption, Record large blue shifts in PL peaks of 132 nm for a 4-QW InGaAs/InGaAsP/InP structure have been demonstrated in the intermixed regions of the QW wafers, on whose non-intermixed regions, a shift as small as 5 nm is observed. This feature makes this technology very attractive for selective intermixing in selected areas of an MQW structure. The dramatical reduction in band gap absorption for the InP based MQW structure has been investigated experimentally. It is found that the intensity attenuation for the blue shifted structure is decreased by 242.8 dB/cm for the TE mode and 119 dB/cm for the TM mode with respect to the control samples. Electro-absorption characteristics have also been clearly observed in the intermixed structure. Current-Voltage characteristics were employed to investigate the degradation of the p-n junction in the intermixed region. We have achieved a successful fabrication and operation of Y-junction optical switches (JOS) based on MQW semiconductor optical amplifiers using HE-IIEI technology to fabricate the low loss passive waveguide. (C) 1997 Published by Elsevier Science B.V.

Electroabsorption modulated semiconductor optical amplifier monolithically integrated with spot-size converters

We have demonstrated an electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA) monolithically integrated with novel dual-waveguide spot-size converters (SSCs) at the input and output ports for low-loss coupling to planar light-guide circuit silica waveguide or cleaved single-mode optical fiber. The device is fabricated by means of selective-area MOVPE growth (SAG), quantum well intermixing (QWI) and asymmetric twin waveguide (ATG) technologies with only three steps low-pressure MOVPE growth. For the device structure, in SOA/EAM section, double ridge structure was employed to reduce the EAM capacitances and enable high bit-rate operation. In the SSC sections, buried ridge stripe (BRS) were incorporated. Such a combination of ridge, ATG and BRS structure is reported for the first time in which it can take advantage of both easy processing of ridge structure and the excellent mode characteristic of BRS. At the wavelength range of 1550-1600 nm, lossless operation with extinction ratios of 25 dB DC and more than 10 GHz 3-dB bandwidth is successfully achieved. The beam divergence angles of the input and output ports of the device are as small as 8.0 degrees x 12.6 degrees, resulting in 3.0 dB coupling loss with cleaved single-mode optical fiber. (c) 2005 Elsevier B.V. All rights reserved.

Influence of a tilted cavity on quantum-dot optoelectronic active devices

Quantum-dot laser diodes (QD-LDs) with a Fabry-Perot cavity and quantum-dot semiconductor optical amplifiers (QD-SOAs) with 7° tilted cavity were fabricated. The influence of a tilted cavity on optoelectronic active devices was also investigated. For the QD-LD, high performance was observed at room temperature. The threshold current was below 30 mA and the slope efficiency was 0.36 W/A. In contrast, the threshold current of the QD-SOA approached 1000 mA, which indicated that low facet reflectivity was obtained due to the tilted cavity design.A much more inverted carrier population was found in the QD-SOA active region at high operating current, thus offering a large optical gain and preserving the advantages of quantum dots in optical amplification and processing applications. Due to the inhomogeneity and excited state transition of quantum dots, the full width at half maximum of the electroluminescence spectrum of the QD-SOA was 81.6 nm at the injection current of 120 mA, which was ideal for broad bandwidth application in a wavelength division multiplexing system. In addition, there was more than one lasing peak in the lasing spectra of both devices and the separation of these peak positions was 6-8 nm,which is approximately equal to the homogeneous broadening of quantum dots.

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.

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 wideband polarization-insensitive SOA-gate is promising for use in future dense wavelength division multiplexing (DWDM) communication systems.

Design of Tensile Strained InGaAsP/InGaAsP MQW for 1.55μmpolarization Indepent Semiconductor Optical Amplifier

The theoretical optimization of tensile strained InGaAsP/InGaAsP MQW for 1.5μm window 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. LThe polarization dependent optical gain is calculated with various well width, strain, and carrier density.

A novel polarization-insensitive semiconductor optical amplifier structure with large 3dB bandwidth

A novel approach to achieving a polarization-insensitive semiconductor optical amplifier is presented. The active layer consists of graded tensile strained bulk-like structure. which can not only enhance TM mode material gain and further realize polarization-insensitivity, but also get a large 3dB bandwidth due to different strain introduced into the active layer. 3dB bandwidth more than 40nm. 65nm has been obtained in die experiment and theory, respectively. The characteristics of such polarization insensitive structure have been analyzed, The influence of the amount of strain and of the thickness of strain layer on the polarization insensitivity has been discussed.