用注入锁模法改善DFB激光器的频率响应

验证了通过注入锁模方法,分布反馈(DFB)半导体激光器的频率响应可以得到明显的改善.实验中通过一个环形器,将主激光器的输出光注入到从激光器.测量了从激光器在有注入光和没有注入光时的光谱和频率响应.发现在不同的注入光强度和波长下,激光器的调制带宽和弛豫振荡峰频率会发生变化.通过适当选择注入光的强度和波长,频率响应可以得到改善.激光器频率响应的改善可以用两个模式的拍频来解释,一个模式是从激光器的主模,另一个是主激光器的模式,该模式与从激光器的边带重合.该理论与实验结果符合得很好.     

用注入锁模法改善DFB激光器的频率响应

验证了通过注入锁模方法,分布反馈(DFB)半导体激光器的频率响应可以得到明显的改善.实验中通过一个环形器,将主激光器的输出光注入到从激光器.测量了从激光器在有注入光和没有注入光时的光谱和频率响应.发现在不同的注入光强度和波长下,激光器的调制带宽和弛豫振荡峰频率会发生变化.通过适当选择注入光的强度和波长,频率响应可以得到改善.激光器频率响应的改善可以用两个模式的拍频来解释,一个模式是从激光器的主模,另一个是主激光器的模式,该模式与从激光器的边带重合.该理论与实验结果符合得很好.     

Bandwidth enhancement of injection-locked 1.3 μm quantum-dot DFB laser

Optical injection locking of a quantum-dot distributed-feedback laser at 1.3 mum is reported. Using an injection ratio of 5.3 dB, an optical detuning of -40 pm, and a slave laser biased at 20 mA, the modulation bandwidth of the injection-locked laser was 16.3 GHz. This is over four times higher than the modulation bandwidth of the free-running quantum-dot laser. At a slave laser bias of 5.0 mA, injection locking resulted in a resonance frequency of 21.9 GHz, over eleven times higher than the relaxation frequency of the free-running slave laser.     

Submillimeter wave generation through optical four-wave mixingusing injection-locked semiconductor lasers

This paper presents a comprehensive analysis of submillimeter wave generation through optical four-wave mixing (FWM) in an injection-locked semiconductor laser. The probe wave introduces pump-probe difference frequency amplitude modulation (AM) and phase modulation (PM) of the slave laser injection locked to the pump wave. The AM and PM indexes of the locked laser output lightwave modulated at the submillimeter wave frequency have been calculated. The submillimeter wave power generated through this technique has also been calculated theoretically. The analysis predicts a submillimeter wave power of -3.7 dBm at 300-GHz frequency for a free-running slave laser output power of 30 mW. In the presence of amplitude modulation of the probe wave, the same modulation is transferred to the submillimeter wave. The suppression of output lightwave amplitude noise relative to the pump, probe, or free-running slave laser amplitude noise has also been estimated in this analysis. At a submillimeter wave frequency of 300 GHz and a probe power equal to the pump power, typical amplitude noise reduction occurs by 7 dB     

用IQ调制器产生载波抑制单边带信号的研究

载波抑制单边带调制是一种特殊的幅度调制形式,它将载波和另一个边带抑制,提高频带利用率,增加了光纤的传输容量.并可有效抑制色散,延长信号的传输距离.被广泛应用于长距离高频微波ROF系统中.文中详细分析了利用商用铌酸锂调制器产生载波抑制单边带信号的原理,并据此分析,搭建了试验系统,分别产生了±1阶(即长波方向和短波方向)的...     

Phase locking and chaos synchronization in injection-locked semiconductor lasers

We theoretically studied synchronization of chaotic oscillation in semiconductor lasers with chaotic light injection. Feedback-induced chaotic light generated from a master semiconductor laser was injected into a solitary slave semiconductor laser. The slave laser subsequently exhibited synchronized chaotic output for a wide parameter range with strong injection and frequency detuning within the injection-locking regime. Our numerical simulation revealed that the synchronized slave laser exhibits remarkable phase locking, even for chaotic light injection. Consequently, synchronization in phase fluctuations becomes dominant over intensity fluctuations. We found that there exists a parameter range where the slave can synchronize in phase only, with no intensity synchronization. However, synchronization can be completely destroyed, both in phase and in intensity, when the phase locking becomes unstable due to four-wave mixing or excited resonance oscillation. The phase locking was studied analytically and the correspondence between numerical and analytical results was shown. We also analytically examined chaos synchronization based on a linear stability analysis from the viewpoint of modulation response of injection-locked semiconductor lasers to a chaotic light signal. As a result, we verified that such injection-locking-induced chaos synchronization results from a quasilinear response of the bandwidth-broadened slave laser due to strong optical injection.     

All-optical clock distribution with synchronous frequency division and multiplication

A master optical clock from a mode locked laser is distributed to two slave twin section lasers. One slave laser divides the optical modulation frequency by 2, the other slave laser multiples the frequency by 2. It is also possible to vary the multiplication-division ratio in a slave laser using only DC control of the absorber of the twin section laser.<>     

Amplitude-modulation sideband injection locking characteristics ofsemiconductor lasers and their application

Amplitude-modulation (AM) sideband injection-locking characteristics of 1.3-μm distributed-feedback lasers are studied experimentally. When the master laser light, which is amplitude-modulated, is injected into slave lasers, the slave lasers can be phase-locked to each sideband of the master laser. This means that the frequency separation between slave lasers can be controlled by the modulation frequency of the master laser. By controlling the injection power, it is possible to achieve a very stable AM sideband injection-locked state of slave lasers. Results on phase-noise and phase-modulation measurements, the frequency stabilization between two channels, and the injection locking to a short pulse are presented. On the basis of the experimental results, an example for designing the multifrequency laser transmitter by means of the AM sideband injection-locking and the mode-locking techniques is described     

Optical frequency modulation and intensity modulation suppression in a master-slave semiconductor laser system with direct modulation of the master laser

An injection-locked laser system where the master laser is directly modulated is analyzed using rate equations. Both quasi-static and dynamic analyses are carried out in order to ensure that the parameters lie inside the locking range. The analysis is valid for all injection levels. The quasi-static analysis provides a good basis for explaining the phenomena. It is shown that, for a given detuning frequency, maximum suppression of intensity modulation (IM) occurs at a specific value of the injection ratio. At low frequencies, the frequency modulation (FM) index of the slave laser bears a constant ratio to the FM index of the master laser of less than unity. It is illustrated that the direct FM scheme is only viable for modulation frequencies up to about 100 MHz. Large IM suppression can only be achieved for large values of the linewidth enhancement factor of the slave laser, small magnitude of the detuning frequency, and low injection ratio. The latter two conditions are associated with narrow limits on stable operation, and care should be taken to avoid instability.     

注入锁定法布里-珀罗激光器的单模工作特性

使用分布式反馈(DFB)激光器对法布里-珀罗(F-P)激光器进行单模注入锁定.通过改变F-P激光器的偏置电流,DFB激光器的输出功率以及两激光器间的波长失谐量,对注入锁定F-P激光器的光谱特性、功率特性以及频率响应特性进行实验分析.找出影响注入锁定F-P激光器稳定性的因素,并测量注入锁定F-P激光器的稳定锁定区;通过优化注人条件实现F-P激光器的高边模抑制比(SMSR)输出,最高可达55 dB;通过与自由运转F-P激光器比较,发现注入锁定可以明显抑制半导体激光器在高频调制下光谱的展宽.注入锁定后F-P激光器的3 dB调制带宽接近14 GHz.实验结果表明,通过合理设计光注入条件,注入锁定技术可以明显改善F-P激光器的光谱特性以及高频响应特性,并在高速光纤通信领域中得到广泛应用.     

Small signal analysis of optical FM signal amplification by aninjection-locked type semiconductor laser amplifier

A small-signal analysis for optical FM signal amplification by an injection-locked type semiconductor laser amplifier with consideration of the spurious intensity modulation (SIM) is presented. In general, the performance of optical FM signal amplification by a laser amplifier is affected by the value of the injection power, by the performance of the injecting laser (the master laser), and by the difference between the emission frequencies of the master and slave optical cavities. In particular, when the modulation frequency is very low, the output frequency deviation (FD) of the laser amplifier turns out to coincide with that of the master laser. However, SIM of the laser amplifier in this case is influenced by the injection conditions. A suitable definition, the ratio of the output FD to SIM to the input FD to SIM, is given to evaluate the performance of an injection-locked-type semiconductor laser amplifier     

Modulation Bandwidth Enhancement in Optical Injection-Locked Semiconductor Ring Laser

The modulation bandwidth of a optical injection-locked (OIL) master–slave configuration using a semiconductor ring laser (SRL) as the slave laser is investigated. The modulation bandwidth depends on the detuning frequency, input optical power into the slave SRL, and the bias current to the SRL in the master–slave configuration. Modulation bandwidth of $> $40 GHz has been achieved when modulating the master laser, in contrast to the 15-GHz modulation bandwidth of the free-running SRL. The unidirectional operation of the SRL as a slave laser allows monolithic integration of such OIL scheme as it produces little feedback to the master laser.      

垂直腔面发射激光器的内调制特性

面向芯片原子钟(Chip Scale Atomic Clock,CSAC)的垂直腔面发射激光器(Vertical Cavity Surface-Emitting Laser,VCSEL)通过微波调制产生具有特定光频差的相干激光,与原子作用后的跃迁谱线频率作为参考标准,最终可获取高精度的频率信号。因此,垂直腔面发射激光器在芯片原子钟系统中至关重要。介绍了VCSEL激光器的内调制原理,搭建了其内调制特性实验测试平台,开展了激光器对射频调制响应特性研究,记录了激光器边带信号随着注入电流和射频输出功率的变化情况,并分析了射频调制对激光器边带信号的影响特性以及Bogatov现象引起的边带不对称现象。实验结果显示:当射频信号频率为3.41734 GHz,注入电流为1.2 mA,射频输出功率为3.5 dBm时,可获得优化的高频调制光谱,为芯片原子钟提供优质的光源。     

Reduction of nonlinear distortion in directly modulatedsemiconductor lasers by coherent light injection

A theoretical investigation of the second- and third-order intermodulation distortions (IMDs) in an injection-locked semiconductor laser under small-signal modulation is presented. The results show that a substantial reduction of the laser nonlinearity can be obtained, depending on both the injection level and frequency detuning between the master and slave lasers. The intensity modulation frequency response is also reported and shows that the injection-locked laser may also have a significantly improved behavior over the same free-running laser, revealed mostly in the reduced resonance peak and the broadening of the modulation bandwidth available     

Microwave Frequency Division and Multiplication Using an Optically Injected Semiconductor Laser

Nonlinear dynamics of semiconductor lasers is applied for microwave frequency division. Optical injection is used to drive a slave laser into the dynamical period-two state. A fundamental microwave frequency and its subharmonic are generated in the power spectrum. Both frequencies will be simultaneously locked when an external microwave near either frequency is applied on the bias. In our experiment, precise microwave frequency division is demonstrated by modulating the laser at the fundamental of 18.56 GHz. A locked subharmonic at 9.28 GHz with a low phase variance of 0.007$hbox rad^2$is obtained from a 10-dBm input. A large locking range of 0.61 GHz is measured under a 4-dBm modulation. Similarly, precise frequency multiplication is demonstrated by modulating at 9.65 GHz. At an input power of$-$5 dBm, a multiplied signal at 19.30 GHz is obtained with a phase variance of 0.027$hbox rad^2$and a locking range of 0.22 GHz.     

跟踪和数据中继卫星系统的微波光调制技术研究

为了提高跟踪和数据中继卫星系统的传输容量,采用ITU推荐的Ka波段为星间微波链路的通信波段,跟踪和数据中继卫星之间采用激光链路.设计采用了激光链路透明传输微波信号的调制技术,包括直接微波信号调制和微波信号变频调制两种方案.通过分析和计算,得到了Ka波段微波光调制器的主要技术参数,论证了宽带LiNbO3行波调制器用于该系统的可行性,并讨论了两种方案的优缺点.     

Microwave modulation of a quantum-well laser with and withoutexternal optical injection

We compare three microwave modulation methods experimentally and theoretically using a semiconductor quantum-well (QW) Fabry-Perot test laser: (1) direct microwave current modulation of the test laser (electrical modulation); (2) optical modulation by an external single-wavelength pump laser with a modulated optical injection power; and (3) electrical modulation of the test laser that is injection locked by an external single-wavelength pump laser with a constant injection power. This is the first direct comparison of the three modulation methods on the same QW laser, to the best of our knowledge. The bandwidth of optical absorption modulation is 7.7 GHz, which is 1.45 times the direct electrical modulation bandwidth (5.3 GHz) at a bias current of 30 mA in the test laser. On the other hand, the electrical modulation of the test laser under injection-locking condition has a significantly higher modulation bandwidth (10.5 GHz) than both the electrical and optical modulation methods     

Multiplexing of millimeter-wave signals for fiber-radio links by direct modulation of a two-mode locked Fabry-Pe/spl acute/rot laser

In this paper, we introduce generation of multiplexed signals on the millimeter-wave bands for fiber-radio systems where an optical millimeter-wave generator is based on a two-mode locked Fabry-Pe/spl acute/rot (FP) slave laser, whose injection current is directly modulated by a signal source. We qualitatively consider the distortion of the millimeter-wave signals from the FP slave laser. The distortion components on the millimeter-wave bands are induced from the simultaneous modulation of the locked modes and the nonlinear modulation response of the FP laser. Two-tone modulation of the locked FP laser is examined to evaluate the dynamic range of the millimeter-wave signals against the second- and third-order distortion components. We also perform fiber transmission of three 156-Mb/s-BPSK signals on the 60-GHz band to demonstrate fiber-radio down-link systems. The total capacity of the down-link system is discussed. In addition, two methods for multicarrier generation on the millimeter-wave bands are proposed. Multicarrier generators supported by these methods can be used as local signals for up-link millimeter-wave signals. The first method is based on multitone modulation of the FP slave laser. We attempt the down-conversion of a 52-Mb/s ASK signal on the 60-GHz band by using the millimeter-wave local signals. The second method depends on the distorted modulation of the FP slave laser by using a single continuous wave signal where the DC-bias level of the FP laser's injection current is partly under the threshold value. We confirm that five carriers on the 60-GHz band are effectively generated by using the second method. Furthermore, the influences of the chromatic dispersion effects on the millimeter-wave local signals are investigated for both methods.     

Nondegenerate Phase-Locking of a Semiconductor Laser by Sideband Injection

A semiconductor laser rate equation theory is presented that describes sideband injection locking under both weak optical injection and current modulation. By simultaneous optical injection and current modulation, control of both the phase and the frequency of a semiconductor laser is demonstrated. The phase-locked semiconductor laser operates at a different frequency to the optical injection source, with a frequency-difference given by the current modulation frequency. This method can be used to produce broadband sources, such as those producing ultrashort pulses and those required for coherent control, or to create high-frequency electronic oscillator sources with phase control by interference beating     

Spectral, phase noise and phase modulation characteristics of AM sideband injection-locked semiconductor lasers

AM sideband injection locking is demonstrated experimentally using 1.3?m DFB lasers. The slave laser is injection-locked to a 3 GHz AM sideband of the master laser. By controlling the injection power, a very stable injection-locked state of the slave laser can be achieved. The phase noise and phase modulation characteristics are also discussed.