Integrated Pulse Shaping On The Silicon-on-insulator Platform

The continuous development of microelectronics technology makes earth-shaking changes to our lives.The integration density of semiconductor chips raises day by day,and the performance and function of them are also promoting.But with the linewidth of the electronic components decreasing,the influence of quantum effects in the electronic circuit becomes more and more obvious.And it makes the loss,crosstalk and delay larger.So the improvement of the integration density slows down.Photonics is the best information carrier due to its large bandwidth and anti-electromagnetic interference.And silicon is the most likely material to achieve large-scale integration because it is compatible with complementary metal-oxide-semiconductor transistor process.Silicon-based devices have attracted widespread attentions.Pulse shaper can be widely used in various fields because it can tailor the waveform or spectrum of the input signal.In communication system,the pulse shaper can implement format generation,format conversion and signal recovery,which can increase the communication capacity and improve the reliability,flexibility and quality of the communication system.Pulse shaper can also be used in signal processing and optical computing.It can realize a programmable filter which is the core component of optical signal processing system.Furthermore,it can implement an optical differentiator,optical integrator and differential equation solver.Another important application of pulse shaper is high frequency microwave signal generation.Taking advantage of the photonic technology,pulse shaper can generate microwave signal with central frequency larger than 60 GHz and large time bandwidth product.This kind of microwave signal has widely applications in anti-collision of automotive,prevention and control of the helicopter,precision tracking,space target recognition,electronic countermeasures,artillery ballistic measurement and guidance.And it is also the significant method to increasing the spatial resolution of the radar system,spreading the spectrum in the electronic countermeasure and realizing miniaturization of the microwave communication system.This dissertation mainly studies the pulse shaper based on silicon on insulator,and the major contect are summarized as the followings:1)Firstly,the development tendency of the communication network is introduced briefly,and the research results of silicon-based laser,detector,modulator,signal processing devices and micro-system are summarized.Then,we introduce the research background and significance of pulse shaper in detail and compare the proposed schemes of pulse shapers.The merits and demerits of these schemes are also analyzed.At last,we summarize the current research status of the pulse shaper,and the development tendency of pulse shaping is proposed.2)An on-chip arbitrary waveform generator based on transverse gradient force effect and finite impulse response structure has been proposed.Utilizing the theoretical knowledge of finite impulse response filter,we design a finite impulse response structure which is easy to fabricate on silicon on insulator.This structure contains a pair of couplers(for beam splitting),amplitude modulators,phase modulators and time delay.The amplitude modulators and phase modulators can be obtained by using transverse gradient force.We calculate and design the pulse shaper based on ridge waveguide and stripe waveguide,respectively.And several typical waveforms are simulated by this pulse shaper.We also discuss the fabrication process of the gradient force component and the influence of the fabrication error.3)Multi-functional pulse shapers based on thermo-optic effect are proposed and demonstrated.The refractive index of silicon enlarges during the temperature increasing,and two schemes of optical pulse shaper are designed based on this property.In the first scheme,a series of waveguides with different widths are fabricated on each tap of the shaper to realize phase modulators,and the phase differences for all taps are controlled by an external thermal source.We further demonstrate optical arbitrary waveform generation based on the optical pulse shaper assisted by an optical frequency comb injection.Four different optical waveforms are generated.In the second scheme,we propose and demonstrate a multi-functional pulse shaper.The pulse shaper can implement a programmable filter,an optical arbitrary waveform generator and a high order differentiator.Based on amplitude and phase modulation of each tap controlled by thermal heaters,we demonstrate the tunability of the central wavelength,bandwidth and variable passband shape of the pulse shaper.And we further obtain several typical waveforms such as triangular waveform,sawtooth waveform,square waveform and Gaussian waveform,etc.In addition,we demonstrate first-,second-and third-order differentiators based on the optical pulse shaper.Our scheme can switch the differentiator patterns from first-to third-order freely.4)A silicon-on-insulator on chip optical arbitrary waveform generator based on Taylor synthesis method is firstly experimental demonstrated.In our scheme,a Gaussian pulse is launched to some cascaded microrings to obtain first-,second-and third-order differentiations.By controlling amplitude and phase of the initial pulse and successive differentiations,we can realize an arbitrary waveform generator according to Taylor expansion.In addition,we analyze the impact of the number of Taylor order on the performance of waveform generation.5)We propose and experimentally demonstrate an on-chip pulse shaper for 125 GHz microwave waveform generation.By controlling the thermal heaters on the amplitude modulator,we obtain several signals centered at 125 GHz with typical envelopes,such as square envelope,triangular envelope,sawtooth envelope and Gaussian envelope and so on.Furthermore,we verify the complete amplitude control,stability and overall power consumption of our pulse shaper.We also propose an improvement idea of frequency tunable microwave waveform generator.