Optimization Design And Experimental Study On 1.3μm Distributed Feedback Lasers Epitaxially Grown On Si

When the size of microelectronic devices approaches the physical limit,it is difficult to achieve higher data transmission rates and lower transmission losses solely by using electrons to transmit information.However,silicon-based optoelectronic integration based on optical interconnection can reach this goal.Silicon-based optoelectronic integration integrates microelectronics and photonic devices onto a siliconbased platform.This method combines the advantages of them and can effectively achieve high-speed information transmission between data centers.At present,devices such as modulators and photodetectors used for optical interconnection have achieved silicon-based optoelectronic integration,but efficient silicon-based integrated lasers are still a huge challenge.This is because silicon(Si),as an indirect bandgap semiconductor material,has relatively low luminescence efficiency.To address this issue,it has been proposed to epitaxially grow III-V material on Si substrates to produce semiconductor lasers,which provides a reliable and efficient method for preparing silicon based light sources.At present,the performance of the Fabry Perot(F-P)cavity laser made using this method is already excellent,capable of achieving an extrapolation life of over 100 years at 35℃.However,it is difficult for F-P cavity lasers to achieve single longitudinal mode operation,so applying multiple F-P lasers to wavelength division multiplexing systems still faces difficulties.Therefore,further research is needed on distributed feedback(DFB)lasers.DFB lasers adjust their wavelength through grating periods,providing high side mode suppression ratio,narrow linewidth,and stable output wavelength.Therefore,they have become the core components of longdistance fiber optic communication and wavelength division multiplexing systems.At present,silicon-based DFB lasers have made some progress,but due to the low output power,it cannot meet the needs of actual optical communication systems.Therefore,designing high-performance Si-based DFB lasers is an urgent problem to be solved.Based on the above research background,this article focuses on the optimization design of 1.3 μm silicon-based quantum dot DFB lasers,and conducts simulation calculations and experiments.The specific research content and innovation points are as follows:(1)A design method combining mode refractive index method with one-dimensional time-domain traveling wave method has been proposed,which can comprehensively consider the transverse and longitudinal mode characteristics of silicon-based quantum dot DFB lasers.In the design,the optimal performance(threshold current density,slope efficiency,output power,side mode suppression ratio)of the lasers was selected as the optimization objective,and the ridge width,etching depth,grating thickness and position were selected as the optimization parameters to optimize the material and chip structure parameters of the lasers.The results show that when the ridge width is 2 μm,the etching depth is 1.3 μm,the grating thickness is 20 nm,and the distance between the grating and the active region is 200 nm,the DFB lasers operate under fundamental transverse mode and single longitudinal mode.Meanwhile,the threshold current density of the DFB lasers is 250 A/cm2,the slope efficiency is 0.77 mW/mA,and the side mode suppression ratio is 48 dB.When the injection current is 150mA,the output power exceeds 100mW.The results indicate that the optimized laser can achieve low threshold current density and high output power.(2)GaAs-based quantum dot lasers were fabricated using an improved double-layer photoresist process.The first layer of photoresist filled trenches to protect SiO2 on sidewalls.The second layer of photoresist was used for photolithography,solving the difficult problem of opening the electrode window of narrow ridge lasers.The first step is to fabricate wide ridge(30 μm,50 μm)GaAs-based lasers operating under pulsed condition at room temperature,which verified the feasibility of material and structure.Then,under existing experimental conditions,we fabricated double trenches narrow ridge(2 μm,3 μm,4 μm)GaAs-based lasers by using a double-layer photoresist process.Under continuous wave condition,the threshold current is 10 mA at 0℃;the corresponding threshold current density is 625 A/cm2.And when the injection current is 100 mA,the output power is 6 mW.