Scaling properties of active-grating amplified surface emittinglasers

The effect of amplified spontaneous emission on the coherent power output, brightness, and conversion efficiency of an active-grating amplified surface-emitting laser is analyzed. The optimum amplifier length for maximizing the brightness of the amplified coherent light is calculated. Although the coherent output power and brightness increase monotonically with length up to the optimum amplifier length, the conversion efficiency decreases monotonically. Beyond the optimum amplifier length, the coherent power output rapidly decreases to zero, as the amplified spontaneous emission intensity coupled into the amplifier mode increases and quenches the gain     

Demonstration of an InGaAsP/InGaAs multiquantum well active-gratingsurface-emitting amplifier

The design and operating characteristics of an InGaAsP/InGaAs strained-layer multiquantum-well active-grating surface-emitting amplifier operating at a wavelength of 1.6 μm are reported. Single-wavelength operation was obtained with 25-dB suppression of amplified spontaneous emission at 150-mW peak power output with a differential quantum efficiency of 24%. This result verifies earlier theoretical predictions that a power output per unit length of ~1 W/cm is feasible     

Analysis of monolithic integrated master oscillator poweramplifiers

An analysis of a novel, monolithic integrated master oscillator power amplifier (M-MOPA) is presented. The M-MOPA consists of a DBR master oscillator which injects power into a linear chain of amplifiers and detuned second-order grating output couplers. The analysis self-consistently includes amplified spontaneous emission buildup and residual reflections throughout the amplifier stages. It predicts that output powers in excess of 1 W can be expected from a single-lateral-mode waveguide multistage amplifier less than 1 cm in length, injected with less than 15 mW of input power. In addition to the signal gain of >25 dB, the signal-to-noise ratio at 1-W output exceeds 15 dB. Because of the small reflections associated with the grating output couplers, and gain saturation by the injected signal, the amplifier self-oscillation threshold is suppressed to current densities above 15 kA/cm²     

Coherent lasers turn up the power

Three categories of multiwatt, coherent laser designs are discussed. The designs are single-mode waveguides suitable for output powers in the order of 200 mW, single-mode operation of multimode lasers, which are suitable for operation between 0.5 and 1.0 W, and the monolithically integrated master-oscillator power amplifier (M-MOPA) designs that have demonstrated 4.5 W of spectrally coherent output power and more than 0.8 W of single-lobe diffraction-limited output power in a technology that is scalable to even higher output powers. Laser-diode design architectures and the unique properties of semiconductor materials are reviewed     

Coherent Array of Nonlinear Regenerative Fiber Amplifiers

A coherent array of high power fiber amplifiers (lasers) with a nonlinear refractive index is described and discussed. By adding reflectivity to the inputs of the fibers, each fiber laser is transformed into a regenerative amplifier, with an internal circulating power that varies depending on the round trip phase shift of the field within the fiber. The variation of the internal circulating power results in a preferential shift in the output phase of each amplifier due to the high nonlinearity within the fiber. The resulting phase shift is predicted to substantially compensate for the inherent randomness in the output phase distribution usually associated with the long lengths of fiber amplifiers. The individual outputs of the coherent array are shown to exhibit a ldquofuzzyrdquo phase distribution that can be partially quantified based on a statistical analysis and is dependent on the parameters of the array. A simple example is given of a coherent array of fiber lasers in a Self-Fourier cavity and the degree of coherence is predicted under simplifying assumptions.     

System performance of coherent transmission over cascaded in-linefiber amplifiers

The limitations of cascaded in-line amplifier systems using coherent modulation-demodulation schemes are examined by evaluating the product of the data rate and the transmission distance. The linear amplified spontaneous emission (ASE) accumulation is shown to make the maximum value of the data rate-distance product increase proportionally with the ratio of the amplifier output signal power to the noise figure. It is also shown that the Kerr-nonlinearity-induced phase noise limits the product of the data rate and the third power of the distance, the maximum value of which is inversely proportional to both the amplifier output signal power and the noise figure. The fiber dispersion is known to limit the product of the distance and the square of the data rate by causing waveform distortion. By taking these three relations into account, it is concluded that coherent signal transmission has a maximum in-line amplifier system length of 10³-10⁴ km in the gigabit-per-second range. Among these three factors, the nonlinearity-induced phase noise has the greatest impact     

X波段GaN收发前端芯片设计

本文设计了一款基于0.25 um氮化镓PHEMT工艺的8.5-10.5GHz MMIC收发前端芯片,该收发前端由一个功率放大器和一个单刀双掷开关组成.经仿真优化后,在工艺线上进行了流片,并载片测试了其性能参数.测试结果显示,发射路的功率放大器饱和输出功率大于33dBm,功率附加效率39%.接收路开关插入损耗0.6dB,开关隔离度大于37dB.     

Large signal RF power transmission characterization of InGaP HBT for RF power amplifiers

The large signal RF power transmission characteristics of an advanced InGaP HBT in an RF power amplifier are investigated and analyzed experimentally. The realistic RF powers reflected by the transistor, transmitted from the transistor and reflected by the load are investigated at small signal and large signal levels. The RF power multiple frequency components at the input and output ports are investigated at small signal and large signal levels, including their effects on RF power gain compression and nonlinearity. The results show that the RF power reflections are different between the output and input ports. At the input port the reflected power is not always proportional to input power level; at large power levels the reflected power becomes more serious than that at small signal levels, and there is a knee point at large power levels. The results also show the effects of the power multiple frequency components on RF amplification.     

InGaP HBT 大信号RF功率传输特性

本文实验研究了用于RF功率放大器的先进的InGaP HBT 器件大信号RF功率传输特性。研究了InGaP HBT在小信号和大信号状态下输出端的发射功率和反射功率及输入端的反射功率的规律。分析了InGaP HBT RF功率信号的多频率功率成份及其对大信号功率增益压缩,非线性和RF输出功率饱和的影响。     

Influence of Reflections of the Output Port on Beam-wave Interaction in Gyrotron Traveling Wave Amplifier

Based on the nonlinear self-consistent theory of gyrotron traveling wave amplifier (gyro-TWA), the influence of the reflections of the output port with the taper on the beam-wave interaction in the gyro-TWA is studied. The simulation results show that the reflections have great effects on the TE₀₁ mode gyro-TWA operating at the fundamental. The influence of the taper angle and the interaction length on the beam-wave interaction and the power profile is discussed and the corresponding physical mechanism is analyzed. The saturated output power keeps same approximately with the increase of the taper angle in the presence of reflection while the saturated gain decreases obviously.     

The dependence of the output of an external-cavity laser on therelative phases of inputs from five gain elements

Five diode lasers that each have one facet antireflection (AR) coated are fiber coupled into an external-cavity and operated as a coherent ensemble. The external-cavity laser output power and spectrum are functions of the relative phases of the inputs from the optical fibers. The phases can be adjusted for an optimum single-mode spectrum simultaneous with maximum output power. In this case, the residual reflections from the AR-coated facets are also properly phased. Dephasing reduces the output power and tunes the wavelength through a series of discrete, lower-power maxima. These maxima occur at wavelengths for which the fiber inputs to the cavity are again in phase but the reflections from the AR-coated facets are not in phase     

基于GaN 的3. 4~ 3. 6 GHz 高增益Doherty 功率放大器

基于两级功率放大器架构,设计了一款平均输出功率为37 dBm(5 W)的高增益Doherty 功率放大器。 该器件通过增加前级驱动功率放大器提高Doherty 功率放大器的增益,采用反向Doherty 功率放大器架构,将λ/4 波 长传输线放置在辅助功放后端,相位补偿线放置在主功放前端,并使主功放输出匹配网络采用双阻抗匹配技术实现 阻抗变换,如此可扩宽功率放大器的工作带宽。连续波测试结果显示:3. 4~3. 6 GHz 工作频段内,饱和输出功率在 44. 5 dBm 以上,功率饱和工作点PAE 在43. 9%以上;在平均输出功率(37 dBm,5 W)工作点,回退量大于7. 5 dB,功 率附加效率PAE 为36. 8%以上,功率增益在31 dB 以上。     

180 W单频全光纤激光器

高功率单频光纤激器在相干探测、功率光谱合成等方面具有广泛的应用前景。分析了高功率单频光纤激光器中受激布里渊散射效应的抑制方法,研究了放大级特性对受激布里渊散射效应的影响。采用线宽为70 kHz的单频光纤激光器作为种子源,经两级光纤放大,实现了中心波长1 064.1 nm、线宽70 kHz、最高功率为180 W的单频全光纤激光输出,光-光转换效率71.1%,光束质量Mx2=1.2,My2=1.21。分析了改变放大级特性前后输出功率提升的原因,认为改变放大级的温度分布减小了受激布里渊散射效应的增益系数,提高了输出激光的受激布里渊散射阈值,促使改变放大级温度分布后的输出功率大幅提高。该激光器的输出功率仅受限于泵浦功率,进一步提高泵浦功率,有望实现更高功率的单频光纤激光输出。     

All-fiber phase-modulated master oscillator power amplifier forcoherent communication

An all-fiber phase-modulated master oscillator power amplifier for free-space coherent communication is presented. A distributed-feedback fiber laser at 1.06 μm is used as master oscillator. A novel phase modulator based on a ZnO-coated single-mode fiber modulates the single frequency communication signal. The modulated signal is then amplified in a double-clad doped fiber power amplifier. Up to 1 W cw single-frequency output power, phase modulated at 196 MHz, has been obtained     

High-power Nd-doped fiber amplifier for coherent intersatellitelinks

Intersatellite optical communication links require laser beams of at least 1 W of power modulated at gigahertz frequencies. They can be delivered by a master oscillator power amplifier system which consists of a stable single-frequency Nd:YAG laser, a high-speed phase modulator, and an optical amplifier. To allow coherent detection, the polarization state must be stable and controllable at the amplifier output and the phase noise must be kept low. We report here the design and the experimental results of a diode laser-pumped double clad Nd-doped fiber amplifier with polarization control, 30-dB gain, and about 1.3 W of output power     

GaAs laser amplifiers

Experimental results are presented on the operational characteristics of GaAs laser amplifiers very closely coupled to a laser oscillator. The separation between the oscillator and the amplifier was varied from 0.2 to 2.0 microns. The amplifiers were made by lapping one end at an angle of 10 to 15 degrees. This angle is several times larger than the critical angle for confinement of radiation in GaAs lasers that is estimated from experimental data to be between 2 and 3 degrees. The measured signal gain is a decaying function of input power and approaches a value of 2 to 4 for large input signals. A maximum amplifier gain of about 150 was obtained for an input signal of 2 mW/mil junction width (corresponding to an optical flux-density of about 8 kW/cm²incident on the input side of the amplifier). At this input power level, the output fluoresence is reduced by about 50 percent and the internal oscillatory modes of the amplifier are almost completely quenched. The ratio of the oscillator output actually coupled into the amplifier to the measured output from the oscillator was estimated from gain saturation measurements. It was found to be inversely proportional to the cleaved separation between the oscillator and the amplifier and was estimated as 0.5 and 0.07 for separations of 0.2 and 2 microns, respectively. The output quantum efficiency of the laser amplifier was demonstrated to be comparable to the output quantum efficiency of a single oscillator. Tests of a new structure for a low-noise, constant-gain laser amplifier are described.     

Multiple-Stokes stimulated Brillouin scattering generation in pulsed high-power double-cladding Er/sup 3+/-Yb/sup 3+/-codoped fiber amplifier

Cascaded Stokes waves generation due to stimulated Brillouin scattering (SBS) of coherent optical pulses in a double-cladding Er/sup 3+/-Yb/sup 3+/ codoped fiber amplifier is reported. The highest attainable output power strongly depends on the amplifier pumping arrangement. A maximum of 40-W peak power has been obtained in counterpumping configuration. The highest energy extracted from the single-mode fiber amplifier in 1-/spl mu/s pulses is limited SBS to 15 /spl mu/J. Theses results have been theoretically confirmed using coupled-waves SBS model.     

1～4GHz 80W GaN超宽带功率放大器

基于南京电子器件研究所0.25μmGaN HEMT工艺平台,设计了一款工作频率为1~4GHz,连续波输出功率大于80W的超宽带功率放大器.放大器采用低通L-C匹配网络实现管芯输入输出阻抗到实阻抗的变换;并利用切比雪夫变换器结构实现超宽带匹配;以单路输入输出端口匹配到100Ω后,两路直接电路合成到50Ω的方法实现了大功率超宽带功放的功率合成.放大器偏置电压32V,静态电流0.4A.测试结果显示,在1~4GHz带宽内,放大器连续波输出功率大于49.05dBm （80.3W）,最高输出功率为50.6dBm （114.8W）,饱和功率增益大于9dB,功率平坦度小于±0.8dB,最大漏极效率为62.5%.     

一种高效率逆F类Doherty射频功率放大器

为了进一步提高射频功放的输出能力,基于GaN HEMT功率器件,采用平衡式结构设计了一款工作频率为3.3 GHz 3.6 GHz的高效率逆F类Doherty结构射频功放。参照功放管的寄生参数等效电路网络,为获得逆F类功放理想的开关特性,设计了具有寄生参数补偿作用的谐波控制网络来抑制功放输出端的二次、三次谐波,同时结合Doherty功放结构特点,使其在6 dB功率回退的情况下仍具有较高的输出效率。仿真后,可得到其在3.3 GHz^3.6 GHz工作频带内的输出功率在40.4 dBm^41.8 dBm内,PAE为66%~77%,最大DE达到82.6%,功率回退6 dB处,功放的DE仍在69%左右,增益平坦度约为±1.5 dB。     

适用于4G无线LTE通信系统的紧凑型谐波抑制功率放大器

为了满足4G无线移动通信LTE系统对功率放大器的性能需求,提出了一种新型采用低通滤波器（Low-Pass Filter,LPF）集成的n次谐波抑制紧凑型功率放大器。该功率放大器使用低通滤波器作为输出阻抗变换网络,以便得到所需阻抗产生最大功率,从而省略了传统的输出匹配网络。所以,相较于传统的功率放大器,提出的功率放大器尺寸减少了25%。此外,由于在输出端使用了低通滤波器,大幅抑制了（2次-5次）谐波,衰减程度较大。提出的功率放大器的设计频率为2.6 GHz,适用于LTE系统。仿真结果与实测结果比较吻合,证明了提出的设计有效性。