AlGaInAs-InP材料系1550nm偏振无关半导体光放大器

采用低压金属有机气相外延设备生长并制作了1550nm AlGaInAs-InP偏振无关半导体光放大器,有源区为3周期的张应变量子阱结构,应变量为-0.40%.器件制作成脊型波导结构,并采用7°斜腔结构以有效抑制腔面反射.经蒸镀减反膜后,半导体光放大器的自发辐射功率的波动小于0.3dB,3dB带宽为56nm.半导体光放大器小信号增益近20dB,带宽大于55nm.在1500～1590nm波长范围内偏振灵敏度小于0.8dB,峰值增益波长的饱和输出功率达7.2dBm.     

1.5 μm GaInAsP angled-facet flared-waveguide traveling-wavelaser amplifiers

A broadband laser amplifier requires extremely low facet reflectivity (<0.1%). Previously, a low effective facet reflectivity of 0.05% was realized by an angle-facet structure in the 1.3-μm wavelength band. Present work reports an improved structure for the 1.5-μm wavelength band by flaring the waveguide ends near the angled facets. With a conventional antireflection coating of ~1% reflectivity, the measured effective facet reflectivity is less than 0.01% and the resultant devices have a fiber-to-fiber gain of 15 dB centered at 1.49 μm     

Feasibility study on the application of the quantum disk to thegain-coupled distributed feedback laser

This numerical study investigated the possibility of using quantum disks in a gain-coupled distributed feedback (DFB) laser, specifically whether the laser would oscillate when the number of electrons in a disk (N_th) is less than the maximum possible number of electrons in the disk (i.e., oscillate at a threshold material gain (g_th) less than the maximum peak material gain for each quantum disk). The influences of the disk diameter and thickness, the number of disks stacked vertically in a layer (N_st), the device length, the period perpendicular to the light propagation direction, and facet reflectivity on the g_th, the threshold current density (J_th), and the normalized gain-coupling coefficient (K_gL) were also examined. When N_st is increased, g_th decreases to less than the value estimated when assuming that the product of g_th and N_st is constant. Although closely spaced disks are useful for reducing g_th , there is an optimum disk distribution minimizing J_th, and this distribution depends on the parameters described above. The J _th also depends on the disk size and is smallest when the diameter is 6 nm. The magnitude of K_gL is about 0.76 and is independent of the height of the gain grating (i.e., N_st), but it can be controlled by adjusting the disk diameter and the facet reflectivity     

Low residual reflectivity of angled-facet semiconductor laseramplifiers

Ridge-waveguide angled-facet semiconductor laser amplifiers for the 1.5 μm band have been fabricated with facet angles of 7° and 10°. Gain measurements performed with a stable, computer-controlled setup have revealed gain ripples as low as 0.025 dB at 22 dB gain for a 10° device. This corresponds to a residual reflectivity of 1×10^-5. Results demonstrate that the residual reflectivity of angled devices with one-layer antireflection coatings can be as low as that for normal facet devices with highly controlled double-layer antireflection coatings     

1.5 µm GaInAsP traveling-wave semiconductor laser amplifier

This paper presents a theoretical and experimental study in terms of small-signal gain, signal gain saturation, and noise characteristics of a 1.5 μm GaInAsP traveling-wave amplifier (TWA), realized through the application of SiOxfilm antireflection coatings. This TWA, having a residual facet reflectivity of 0.04 percent, exhibits a wide, flat signal gain spectrum and a saturation output power of +7 dBm at a 20 dB signal gain. The TWA also has a noise figure of 5.2 dB, which is the smallest value reported for semiconductor laser amplifiers. The experimental results are confirmed to be in good agreement with the theoretical predictions based on the multimode traveling-wave rate equations in conjunction with the photon statistic master equation analysis, which takes into account the amplifier material and device structural parameters. Signal gain undulation, saturation output power, and noise figure are also theoretically evaluated as functions of the facet reflectivity. The superior performance of the TWA demonstrates that the device is favorable for use in linear optical repeaters in fiber transmission systems.     

Angled-facet S-bend semiconductor optical amplifiers for high-gainand large-extinction ratio

The extinction ratio of an optical gate with a spot-size-converter-integrated semiconductor optical amplifier (SSC-SOA) is deteriorated following the direct coupling of unguided light between the input and output fibers. In this letter, an S-bend waveguide structure is introduced into an active waveguide to suppress such direct coupling. Angled facet structures are also introduced for obtaining low facet reflectivity. The fabricated SSC-SOA operating at 1.55-μm wavelength achieves an extinction ratio up to 70 dB and a fiber-to-fiber gain of 20 dB     

1.3μm高增益偏振无关应变量子阱半导体光放大器

采用低压金属有机化学气相外延法 (LP MOVPE)生长并制作了 1 3μm脊型波导结构偏振无关半导体光放大器 (SOA) ,有源区为基于四个压应变量子阱和三个张应变量子阱交替生长的混合应变量子阱 (4C3T)结构 ,压应变阱宽为 6nm ,应变量 1 0 % ,张应变阱宽为 11nm ,应变量 - 0 95 % ;器件制作成 7°斜腔结构以有效抑制腔面反射。半导体光放大器腔面蒸镀Ti3 O5/Al2 O3 减反 (AR)膜以进一步降低腔面剩余反射率至 3× 10 -4以下 ;在 2 0 0mA驱动电流下 ,光放大器放大的自发辐射 (ASE)谱的 3dB带宽大于 5 0nm ,光谱波动小于 0 4dB ,半导体光放大器管芯的小信号增益近 30dB ,在 12 80～ 1340nm波长范围内偏振灵敏度小于 0 6dB ,饱和输出功率大于 10dBm ,噪声指数 (NF)为 7 5dB。     

Improved selectivity and decreased spontaneous emission from anAR-HR coated SL-MQW DFB semiconductor laser amplifier

It is shown that the performance of a DFB filter/amplifier can be improved considerably with respect to selectivity and amplified spontaneous emission by applying a high reflective coating to the output facet. To illustrate this a strained-layer multiple quantum well DFB filter/amplifier with an output facet reflectivity of 97% is compared with a conventional, AR-coated phase adjusted DFB filter/amplifier. Peak fiber-to-fiber gains for these devices are 21 and 18 dB, respectively, when biased at 98% of their threshold current. The transmission gain of these DFB filter/amplifiers has been measured over a wavelength span of 30 nm. For the AR-HR coated SL-MQW DFB filter/amplifier the selectivity is improved with 11 dB resulting in an extinction ratio for interfering channels of better than 35 dB and the amplified spontaneous emission is reduced by 16 dB down to -37 dBm compared to the conventional DFB filter/amplifier     

1.3 μm GaInAsP near-travelling-wave laser amplifiers made bycombination of angled facets and antireflection coatings

1.3 μm GaInAsP near-travelling-wave laser amplifiers have been realised by the combination of angled facets and antireflection coatings. Without in situ monitoring on the device itself during dielectric coatings, one can routinely obtain a low effective modal facet reflectivity of 5-8×10^-4. The devices had an internal gain of 24±1.5 dB for the TE mode and a single-mode fibre coupling loss of 5 dB/facet     

1.5 mu m band travelling-wave semiconductor optical amplifiers with window facet structure

1.5 mu m band travelling-wave semiconductor optical amplifiers (TWAs), characterised by their window facet structure and symmetrised active waveguide, have been developed. 1.5 dB spectral gain ripple and 1.3 dB TE-TM mode gain difference at 22 dB signal gain were achieved simultaneously. An average facet reflectivity as low as 0.06% was estimated.<>     

Polarization-insensitive optical amplifiers in AlInGaAs

We report the theoretical modeling and the fabrication of polarization-insensitive optical amplifiers at 1300 nm in AlInGaAs-InP material system. Gain calculations, using the k.p method, show that the introduction of 0.33% tensile strain into a three-quantum-well structure can achieve gain-matching over a wide energy spectrum. The amplifiers, fabricated and tested, show excellent polarization insensitivity (less than 0.3 dB) at 1280 nm with a gain of 11 dB at 150 mA. Gain-bandwidth needs to be improved by employing antireflection coatings to suppress the facet reflectivity     

Influence of residual facet reflectivity on nonlinearities in semiconductor optical amplifiers

A dynamic model for multichannel amplification by semiconductor optical amplifiers is used to predict the influence of the residual facet reflectivities on intermodulation distortion. For 25 dB of singlepass gain a reflectivity of 5*10/sup -4/ will result in 3 dB excess distortion.<>     

1.3μm行波式半导体激光放大器

利用多级尝试法对主动监控法进行优化,获得了两端面剩余模式反射率几何平均值小于3×10-4的行波式半导体激光放大器,并在1.3μm波段获得了20dB的信号增益。     

Fabrication and characterization of 1 550 nm polarization-insensitive semiconductor optical amplifiers

Semiconductor Optical Amplifiers (SOAs) can beused asin-line amplifier ,preamplifier ,optical switch,andwavelength converter in future optical systems[1-3].Po-larization-independent gain,high output power and lowgain ripple are desirable features for most…     

Semiconductor optical amplifier for wavelength conversion in subcarrier multiplexed systems

The fabrication and performance of a InGaAsP-InP semiconductor optical amplifier for wavelength conversion in subcarrier multiplexed system is described. The amplifier is of the buried facet design and has polarization and reflectivity gain ripple of less than 1 dB. Using subcarrier multiplexing, multiple 50-Mb/s data streams at a wavelength of 1.553 /spl mu/m are infected into the amplifier. The gain nonlinearity of the amplifier transfers the data to a different wavelength of light simultaneously injected into the amplifier. Error free retrieval of subcarrier multiplexed data has been demonstrated for the wavelength converted output. The small signal bandwidth of the wavelength conversion process is 5 GHz. Calculation suggests that higher bandwidth is feasible at higher input powers at the expense of lower modulation transfer during wavelength conversion.     

低偏振灵敏度行波半导体光放大器的实验研究

本文报导了一种具有低偏振灵敏度的行波半导体光放大器。通过有效地设计放大器的端面增透膜系，使得端面残余反射率低于１０－４，从而获得低于２ｄＢ的偏振灵敏度。     

Nearly degenerate four-wave mixing in laser diodes subject tostrong probe injection power

Nearly degenerate four-wave mixing (FWM) in above-threshold laser diodes with symmetric or asymmetric facet reflectivities, subject to strong probe injection power, is investigated theoretically, taking into account the effects of pump depletion, carrier diffusion, gain saturation, gain compression, total power dependence of the gain and coupling coefficients as well as the longitudinal dependence of the nonlinear interaction. It is shown that the reflectivity efficiencies of probe and conjugate waves demonstrate significantly different behaviors for strong probe injection power, compared to small probe injection power, and a greater than 3 dB enhancement of reflectivity efficiencies can be achieved in an asymmetric laser diode, compared to a symmetric laser     

Detailed dynamic model for semiconductor optical amplifiers andtheir crosstalk and intermodulation distortion

An advanced dynamic model for multisection semiconductor optical amplifiers is presented. It accounts for the carrier and field distributions in the longitudinal direction as well as for the facet reflectivities. The model can handle arbitrary time-varying input signals and current modulations. The model is used to assess intermodulation distortion and crosstalk. Cascaded amplifiers are considered, and the crosstalk and intermodulation distortion due to cascaded amplifiers are found to accumulate by adding together in amplitude; this may limit the number or cascaded amplifiers in multichannel systems. Carrier-induced nonlinearities depend strongly on facet reflectivities; for 25 dB of single-pass gain, a reflectivity of 5×10^-4 will result in 3 dB excess distortion. Reduction of intermodulation distortion by use of multisection amplifiers is found to be possible only for small channel separations (<300 MHz). Simulations of 11-channel amplification showed a reduction of 13 dB in intermodulation distortion when random-phase optical carriers are applied     

Detailed model and investigation of gain saturation and carrier spatial hole burning for a semiconductor optical amplifier with gain clamping by a vertical laser field

A detailed model for semiconductor linear optical amplifiers (LOAs) with gain clamping by a vertical laser field is presented, which accounts the carrier and photon density distribution in the longitudinal direction as well as the facet reflectivity. The photon iterative method is used in the simulation with output amplified spontaneous emission spectrum in the wide band as iterative variables. The gain saturation behaviors and the noise figure are numerically simulated, and the variation of longitudinal carrier density with the input power is presented which is associated with the on-off state of the vertical lasers. The results show that the LOA can have a gain spectrum clamped in a wide wavelength range and have almost the same value of noise figure as that of conventional semiconductor optical amplifiers (SOAs). Numerical results also show that an LOA can have a noise figure about 2 dB less than that of the SOA gain clamped by a distributed Bragg reflector laser.     

Analysis and application of theoretical gain curves to the design of multi-quantum-well lasers

Gain/current curves for a single quantum well are calculated. The optimum well number, cavity length, threshold current, and current density of multi-quantum-well (MQW) lasers are derived in terms of this gain curve. The limiting performance of MQW lasers is found to be better than that of graded refractive index (GRIN) lasers, assuming comparable efficiencies and spontaneous emission linewidths. The optimum threshold current for an MQW laser with a 7 μm cavity and 90 percent facet reflectivity issim50 muA/μm.