Design Of An Ultra-Broadband Tunable Laser Based On The Distributed Moire-Grating Reflector

With the rapid development of optical communication network for higher speed and capacity,the structure of optical network is becoming more and more complex.In order to reduce the pressure of optical network reconfiguration,semiconductor lasers with broad tuning range of the lasing wavelength are highly desirable.In this work,a broadband tunable laser based on the distributed Moire-grating reflector(DMR)is designed and analyzed.Compared to the conventional sampled-grating tunable lasers,the tuning range of DMR laser can be much broader and will only be limited by the material gain bandwidth.Moreover,since there is no need to exploit the Vernier effect,the tuning curve of DMR can be continuous and monotonic.By changing the period of either one of the two basic gratings,the equivalent period of their combined Moire envelope AM will change significantly in the real-space domain monotonically.The Bragg reflection wavelength ?B for the Moire grating structure will have a broad tunable spectrum range,so that the tunable spectrum range can be greatly extended.To demonstrate and verify this Moire effect,the transfer matrix method(TMM)and finite difference time-domain(FDTD)method are used to simulate the Moire grating structure.Digital filter technique is also implemented in the traveling wave model(TWM)to simulate and verify the Moire effect functionality for tunable laser operation.The previously calculated Moire grating reflection and transmission spectra from TMM or FDTD can be converted into time-domain sequences of discrete sampling points by the inverse Fourier transform.Then,they are used as filters to do convolution with the forward traveling optical fields from the active region facet to obtain the final output fields of the laser.At the end of the thesis,we propose a feasible structure model of Moire grating laser based on DBR.We discuss the possibility for realizing basic grating period change by using the ceramic perovskite materials,which is compatible with the III-V type material and the silicon wafer,and has a much larger piezoelectric coefficient to achieve electrical tuning.With a low applied voltage,vertical expansion of the upper PZT layer can press and deform elastically one of the underlying basic gratings,such that period of the Moire envelope as well as the Bragg wavelength may be tuned continuously and monotonically in ultra-broad bandwidth.Our simulation result has shown that the lasing wavelength of the DMR laser can be tuned over a range of 40 nm(up to 150 nm)in a continuous and monotonic fashion.