Effects of spatial hole burning on gain switching invertical-cavity surface-emitting lasers

We present a numerical study of the effects of carrier diffusion and spatial hole-burning in vertical-cavity surface-emitting lasers under gain switching. Our model includes spatial and temporal dependences of both the optical field and the carrier density. Results show that spatial hole burning places a limit on the minimum achievable pulse width. We demonstrate that spatial hole-burning tan be avoided and shorter pulses can be obtained by using an appropriate pumping geometry. We also consider the case in which the laser operates simultaneously in two transverse modes and show that transverse-mode competition induced by spatial hole burning leads to period doubling and other interesting nonlinear behavior     

非均匀增宽增益烧孔的描述

激光物理学中,对于非均匀增宽介质,速率方程理论给出了强场I_v的增益系数为:G(v,I_v)=G_4~0(v)/(1+I_v/I_s) (1)式中G_i~0(v)是I_v=0时的小信号增益系数,I_s为介质的饱和强度.(1)式虽然很好地给出大信号增益系数与其自身小信号增益系数的关系,但不能反映出频率为v的大信号对频率为v’的小信号增益系     

Gain-coupled DFB lasers versus index-coupled and phase shifted DFBlasers: a comparison based on spatial hole burning corrected yield

A statistical yield analysis is presented for gain- and index-coupled distributed feedback (DFB) laser structures, allowing a comparison of their single longitudinal mode (SLM) yield capabilities. For the yield calculations, the threshold gain difference and the longitudinal spatial hole burning (SHB) are taken into account. By comparing the experimental and theoretical yield of index-coupled DFB lasers, the significance of SHB for correct yield predictions is illustrated. For the purpose of comparison, yield calculations for various λ/4-shifted DFB lasers (with low facet reflectivities) are presented. The most emphasis, however, is on partly gain-coupled DFB lasers. Estimations of practical gain coupling coefficient values for gain and for loss gratings are discussed     

Longitudinal spatial hole burning and associated nonlinear gain ingain-clamped semiconductor optical amplifiers

The longitudinal spatial hole burning (LSHB) in gain-clamped semiconductor optical amplifiers (GCSOAs) is investigated by means of a numerical model, which is based on position-dependent rate equations for the carrier density and the propagation equations for the optical power. The simulation results show that the carrier densities are nonuniformly distributed within the active layer of GCSOAs. The nonuniformity can be large, especially for high currents and optical signal powers near the saturation. It is found that the LSHB induces a gain nonlinearity, which causes interchannel cross talk when GCSOAs are used in wavelength division multiplexing (WDM) applications. In order to reduce this gain nonlinearity, two methods are analyzed: the use of low resistivity devices and the use of unbalanced Bragg mirror reflectivities     

Effects of carrier transport on the L-I characteristics of QWlasers in the presence of spatial hole burning

In this paper, we study the effects of carrier transport and carrier capture on the linearity of the light-current characteristics of a semiconductor laser using an analytically solvable model. We include various physical processes within the model and study how they affect laser linearity. The technique used shows how to integrate the photon and electron transport within a single model, and the conclusions reveal some interesting aspects of semiconductor laser characteristics     

Dynamic and noise properties of tunable multielectrodesemiconductor lasers including spatial hole burning and nonlinear gain

A general formalism based on the Green's function method is given for multielectrode semiconductor lasers. The effects of both spatial hole burning and nonlinear gain are included in this formalism. An effective nonlinear gain is introduced by taking into account the influence of the laser structure and the associated distribution of the mode intensity along the cavity length and the frequency and intensity modulation properties of multielectrode semiconductor lasers are studied. A general linewidth expression which includes contributions from spontaneous emission and carrier shot noise is given. It is found that the effective α-factor affecting the linewidth is in general different from its counterpart affecting modulation and injection locking properties due to spatial hole burning and nonlinear gain. The linewidth due to various contributions is calculated for both uniform intensity distributed lasers and phase-shifted distributed feedback (DFB) lasers     

Numerical analysis of static wavelength shift for DFB lasers with longitudinal mode spatial hole burning

The static wavelength shift induced by longitudinal mode spatial hole burning is analyzed numerically for lambda /4-shifted DFB lasers. The effective Bragg wavelength at each bias level is introduced to clarify the contribution of nonuniformity in carrier density distribution to the lasing wavelength shift. It is shown that the wavelength shift is caused by two separate factors: by the position-dependent deviation and by the average value in the exact N/sub eq/ distribution. The former factor induces both red- and blue-shifted tuning due to the nonuniformity itself in carried density distribution, while the latter results in blue-shifted tuning due to the increase in modal gain.<>     

Competing effects of well-barrier hole burning and nonlinear gainon the resonance characteristics of quantum-well lasers

The effects of the quantum capture and release of carriers from quantum wells (QWs) on the resonance response of QW lasers are investigated from a model of well-barrier hole burning with built-in nonlinear gain. Significant similarities and contrasts with the conventional single-mode model are noted in both the large-signal transient behavior and in the small-signal resonance characteristics. The competition between well-barrier hole burning and nonlinear gain is explored by studying of time responses, phase portraits, frequency transfer functions; and contour maps of constant resonance frequency, damping rate, and 3-dB bandwidth in the parameter spaces defined by the nonlinear gain coefficient versus the ratio of relaxation times for capture and release of carriers by the wells. A systematic treatment of the well-barrier model is presented along with these predicted dynamical trends     

Theoretical analysis of spectral hole burning and relaxationoscillation in all-optical gain stabilized multichannel erbium-dopedfiber amplifier (EDFA)

The spectral hole burning effects and gain dynamics of all-optical gain clamped multichannel erbium-doped fiber amplifiers (EDFAs) are modeled. The two-level laser model is used to write the propagation and rate equations of the inhomogeneous laser medium. The governing equations are an uncountable system of partial differential equations (PDEs). After some mathematical manipulations, averaging over the fiber length and introducing an approximation method, the system of PDEs is converted to a finite system of ordinary differential equations (ODEs). The gain dynamics and hole burning of an all-optical stabilized multiwavelength EDFA and the transient response of an optical fiber inverter are analyzed by the solution of the system of ODEs. Theoretical results are in good agreement with the published experimental result     

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.     

Modeling of gain, differential gain, index change, and linewidthenhancement factor for strain-compensated QWs

The gain, differential gain, index change, and linewidth enhancement factor for strain-compensated InGaAs-GaAsP-InGaP quantum wells (QWs) are modeled. The model we have developed builds upon the model-solid theory for determining the band offsets, the k·p method for calculating the matrix elements of dipole moment, and the density matrix approach for computing the complex susceptibility of strain compensated QWs. We also incorporate bandgap renormalization. The calculated results based on the model are consistent with available experimental results in the literature. It is shown that InGaAs-GaAsP-InGaP strain-compensated QWs could offer much higher gain, higher differential gain, and lower linewidth enhancement factor than AlGaAs-GaAs conventionally compressively strained QWs, but more because of its larger hand offset than anything else     

Spectral hole burning and carrier-heating effect on the transientoptical nonlinearity of highly carrier-injected semiconductors

An improved density-matrix theory is developed that can treat both spectral hole burning and carrier heating self consistently. Various intraband and interband relaxation terms characterized by different relaxation times and quasi-equilibrium distributions are introduced into the density-matrix equations within a relaxation-time approximation. Conservation of total number and energy densities of carrier systems in each band is considered to determine the quasi-equilibrium distributions. Formalism is applied to the calculation of the transient optical nonlinearity of highly carrier-injected semiconductors. Spectral hole burning and carrier-heating effects on the spectral and temporal characteristics are then clarified. In particular, the significant four-wave-mixing effect due to carrier heating is pointed out. An experiment that can be used to directly prove the existence of the carrier-heating effects on gain nonlinearity is also proposed     

Effects of the periodicity of the subwavelength hole arrays and hole shape of a thin gold film on the optical transmission characteristics

The influence of the periodicity of subwavelength hole arrays and hole shape on transmission frequency and intensity has been studied.The subwavelength hole array sample is prepared on the 220 nm Au film.The transmission characteristics are measured and analyzed.The transmission spectra show that the different transmission peaks depend on the periodicity of hole arrays and the shape of the holes.With the shorter hole array period,the transmission peak shows blue shift,and the ohmic losses of surface plasmon...     

Effect of inhomogeneous line broadening on gain and differential gain of quantum dot lasers

Detailed theoretical analysis of the size fluctuation in InAs-GaAs quantum dot (QD) lasers is presented. Analytical expressions for the inhomogeneous line broadening and the optical gain are derived for a Gaussian size fluctuation distribution. The effect of size fluctuations on the QD carrier density, modal gain, and differential gain is studied. Red shifts in the gain peak is observed when size fluctuations increases. The energy detuning between the gain peak and the differential gain peak for a pyramidal quantum dot system having an average base length of 130 /spl Aring/ and standard deviation of 7 /spl Aring/ is about 12 meV.     

基于频移和偏振烧孔的多波长掺铒光纤激光器

为了研究能够在室温下实现稳定多波长输出的掺铒光纤激光器,采用了在激光谐振腔中引入正弦相位调制和偏振烧孔来抑制腔中模式竞争的方法。在线形谐振腔中,利用半导体光波导作为一个反射腔镜,并用正弦信号对其进行驱动。这样,半导体光波导可以等效成一个对光信号产生移频反馈效果的正弦相位调制器和一个诱使掺铒光纤中产生偏振烧孔的非线性相位延时器。通过实验,得到了10波长输出的稳定光谱。相邻波长间隔为0．32nm,功率谱比较平坦,起伏小于3dB。结果表明,相位调制和偏振烧孔的共同作用,可有效地抑制由于掺铒光纤的均匀展宽效应引起的模式竞争。     

Modal analysis of a planar waveguide with gain and losses

In this study, we analyze the waveguiding properties of a planar waveguide amplifier in which losses and gain can be present simultaneously. It is found that the subsequent modes comprise both loss and gain modes. Also, the dependence of the gain on the state of polarization turns out to be significant for realistic dielectric structures. For strong losses or gain, the standard transfer matrix approach may become numerically unstable, therefore, a scattering matrices formalism is employed. A semiconductor-like gain profile enables us to study the gain as a function of ω for realistic laser amplifier structures     

基于多模光纤偏振烧孔效应的双波长掺铒光纤激光器

基于多模光纤(MMF)引入的偏振烧孔(PHB)效应,研制了一种环形双波长掺铒光纤(EDF)激光器.单模光纤(SMF)-MMF-SMF组成的结构使MMF不同偏振方向的反射模在波长上分开,利用PHB效应实现双波长的输出,输出波长间隔可通过改变MMF的长度改变.实验对比了1.6 m和3.0 m长的MMF输出波谱特性,结果表明...     

Influence of spatial hole burning on the output power of a CW dye ring laser

The output power of a single-mode CW dye ring laser can be enhanced by 50 percent by changing over from standing-wave (SW) operation to traveling-wave (TW) operation. This effect is attributed to smoothing out the SW pattern in the active medium, which gives rise to spatial inhomogeneities of the inversion.     

链路系统微分增益公式的建立和讨论

从微分增益的定义式和基本物理概念出发,以系统各设备同一阶梯电平所对应的ＤＧ值为依据,建立了传输链路的系统微分增益ＤＧｓ的计算公式,并对ＣＣＩＲ和ＧＢ相关的一些问题作了讨论。