The Research Of Hybrid Integrated Chaotic Semiconductor Laser

Chaotic laser is a special output form of the laser that has inherent randomness,sensitivity to initial values,wide spectrum,etc.It has important applications in many fields,such as chaotic confidential optical communications,high-speed physical random number(key)generation,high-precision optical network fault detection,anti-warning radar,ultra-wideband technology,distributed optical fiber sensing,and so on.And the chaotic light source is the core component of its application in various fields.Most of the traditional chaotic light sources are built on a laboratory platform using semiconductor laser combined with various external discrete optical components.It is large in size,vulnerable to environmental influences,and unstable in output,which affects the popularization of chaotic laser.In order to truly realize the practicality and industrialization of the chaotic light source,it is necessary to develop a photonic integrated chaotic semiconductor laser with small size,stable performance,and low cost.At present,the research work on integrated chaotic semiconductor lasers is based on the growth of laser chips,optical feedback components,light injection components,and amplification components on the same substrate material.It belongs to the monolithic integration category.These chaotic lasers reduce the volume of traditional chaotic sources,meet the requirements of integration,have stable performance,and are not susceptible to changes in the external working environment.However,monolithic integrated production process requires specialized technical,expensive and sophisticated instruments and delicate operations.The technology is complex,the yield is low and the cost is high,which is not conducive to industrial production.In present period,the implementation threshold is relatively high,and it is difficult to achieve mass production in a short time.For this situation that the traditional chaotic source has a large volume and unstable performance and the current research on integrated chaotic source is focused on the field of monolithic integration,this paper mainly carried out the following research:(1)It is proposed to develop a hybrid integrated chaotic semiconductor laser that utilizes existing commercial micro-devices,which has the characteristics of small volume,integration,stable performance,simple process,low cost,favorable mass production and high yield.(2)Based on the existing production technology of butterfly optical transmitter,an integrated chaotic semiconductor laser with two types of structures,including internal coupling(feedback cavity length is 2 mm)and external coupling(the feedback cavity length is 8.25 mm),was designed.It uses distributed feedback laser chip,collimating micro-lens,partially reflecting mirror,focusing micro-lens,and fiber coupling to generate and output chaotic laser.Among them,the feedback cavity is formed by the distributed feedback laser chip and the partially reflecting mirror.The above devices as well as chip sub-mount,heat sink,and thermoelectric cooler are integrated and will be sealed by a commercial 14-pin butterfly package with a lid and filled with nitrogen.In each type of structure,the partially reflecting mirror with 20%,10%and 5%reflectivity are used to find the best combination of feedback cavity length and reflectivity.This integrated chaotic semiconductor laser is not only integrated and has stable performance,but also simple in process,low in threshold and conducive to mass production.(3)The above two types of integrated chaotic semiconductor lasers were fabricated and their output characteristics were experimentally tested.It is found that the integrated semiconductor laser with external coupling structure and 20%reflectivity,and the integrated semiconductor laser with internal coupling structure and 5%reflectivity can generate chaotic laser with spectral bandwidth over 4.5GHz.The latter maintains its output in the chaotic state while changing the bias current.Such a robustness and stability is very helpful for the subsequent application of the chaotic source.