Joint research on photonic integrated circuits based on gain-coupled distributed feedback semiconductor lasers

1.增益耦合系数的提取我们建立了一种新的参数提取方法，将理论光谱与低于激光阈值的实验放大自发辐射光谱进行数值拟合，首次使增益耦合系数的测量成为可能。利用该技术，对吸收栅型增益耦合分布反馈(GC DFB)激光器的耦合系数随注入电流变化的理论预测进行了实验验证。2.小信号直接调制特性测量了GC DFB激光器的小信号调制响应，提取了弛豫振荡频率和衰减因子。因此，与传统激光器不同的是，它们的衰减因数有一个随光输出功率增加而减小的区域。3.模拟调制失真的分析和测量我们用一种新的数值方法分析了吸收栅型GC DFB激光器的模拟调制失真。结果发现，由于有源层中的增益压缩被光栅中的吸收压缩所抵消，二次谐波失真被减小。4.首次采用四步金属有机气相外延(MOVPE)技术制备了1.55 nm波段的GC DFB激光器。5.利用V型槽衬底上生长的MOVPE制备了具有量子线有源区的GC DFB激光器。首次利用MOVPE生长出了具有InGaAs应变量子线有源区的GC DFB激光器。6.利用选区MOVPE制作MMI耦合器首次成功地用选择区MOVPE制作了多模干涉耦合器。

1.Extraction of gain-coupling coefficientWe established a new parameter extraction method where theoretical spectra were numerically fitted onto experimetal amplified spontaneous emission spectra below lasing threshold, and made measurement of gain coupling coefficients possible for the first time. Using this technique, we experimentally verified the theoretical prediction that the coupling coefficients in gain-coupled distributed feedback (GC DFB) lasers of absorptive grating type change with injection current.2.Small signal direct modulation characteristicsWe measured small signal modulation response in GC DFB lasers and extracted relaxation oscillation frequency and damping factor. As a result, unlike the conventional lasers, their damping factor had a region where it decreased with increasing optical output power. By making use of this phenomenon, we will be able to extend the modulation bandwidth beyond that of common DFB lasers.3.Analysis and measurement of analog modulation distortionWe analyzed analog modulation distortion in GC DFB lasers of absorptive grating type by a newly-developed numerical method. As a result, the second harmonic distortion was found to be reduced due to cancellation of gain compression in the active layr by absorption compression in the grating. A preliminary experiment was conducted to confirm the above theoretical prediction.4.Fabrication of GC DFB laser triode1.55mum wavelength band GC DFB laser triodes have successfully been fabricated for the first time by four step metal organic vapor phase epitaxy (MOVPE).5.Fabrication of a GC DFB laser with quantum wire active regionBy making use of MOVPE growth on V-grooved substrates, a GC DFB laser with InGaAs strained quantum wire active region has successfully been fabricated for the first time.6.Fabrication of MMI couplers by selective-area MOVPEWe successfully fabricated multimode interference (MMI) couplers by selective-area MOVPE for the first time.