Silicon high-resistivity-substrate millimeter-wave technology

The application of molecular beam epitaxy (MBE) and X-ray lithography for the fabrication of monolithic integrated millimeter-wave devices on high-resistivity silicon has been investigated. Process compatibility and the retention of high-resistivity characteristics were measured using the spreading resistance method and Hall measurements after various process steps. Microstrip resonators of ring and linear geometry were fabricated on 10 000 Ω.cm silicon substrates. For linear microstrip resonators, the attenuation was found to be less than 0.6 dB/cm at 90 GHz. A 95-GHz IMPATT oscillator circuit and a planar microstrip antenna array have been fabricated on highly insulating silicon substrates. For the oscillator, a combined monolithic-hybrid integration technique was used to attach the discrete IMPATT diode to the resonator circuit. The oscillator does not require tuning elements. Preliminary experimental results are 8 mW of output power with 0.2 percent efficiency at 95 GHz.     

Monolithic 3-D silicon photonics

A monolithic CMOS compatible process has been developed to realize vertically integrated devices in silicon. The method involves the implantation of an oxygen into a patterned silicon substrate to form buried guiding structures. These buried devices are separated from a surface silicon layer by an intervening layer of silicon dioxide formed through the implantation process. Photolithography and etching is used to define devices on the surface silicon layer. The method has been utilized to realize the vertically coupled microdisk resonators and a variety of microresonator-based integrated optical elements. A new method for extraction of the unloaded Q of a cavity from its measured spectrum is also described.     

Precision fabrication techniques and analysis on high-Q evanescent-mode resonators and filters of different geometries

High-Q evanescent-mode resonators and filters are realized by both silicon micromachining and layer-by-layer polymer processing. Capacitively loaded cavities can be reduced to a size much smaller than a wavelength, but still have a much higher unloaded Q than lumped elements. The loaded resonators are utilized for reduced-size filters with a low insertion loss enabled by the relatively high-Q factor. The small fabrication tolerances of silicon micromachining and polymer stereolithography processing enable the realization of highly loaded evanescent-mode resonators and filters. A 14-GHz resonator micromachined in silicon has a volume of 5 mm /spl times/ 5 mm /spl times/ 0.45 mm, representing a resonant frequency reduction of 66.8% compared to an empty cavity of the same dimensions. The polymer-based fabrication is used to create resonators of different three-dimensional geometries with Q's up to 1940 and frequency reductions up to 49.9%. An insertion loss of 0.83 dB is measured in a 1.69% bandwidth filter created by polymer processing with a frequency reduction of 47% compared to an unloaded cavity. The frequency sensitivity to fabrication tolerances of these structures is also analyzed.     

Low-loss ring resonators fabricated from silicon based integrated optics technologies

The fabrication of low-loss ring resonators using silicon based integrated optics technologies is reported. Propagation losses of 0.028+or-0.009 dB/cm have been deduced from finesse measurements.<>     

Measurement of optical nonlinearity in silicon rich nitride waveguide ring resonators

The optical nonlinearities of amorphous silicon rich nitride corresponding to /spl chi//sup (3)/ in a static electric field have been measured by tracking wavelength shifts in the resonances of optical waveguide ring resonators as a function of an applied electrical field. The magnitude of the nonlinearity measured agrees well with expected values.     

All-optical 6- and 8-channel demultiplexers based on photonic crystal multilayer ring resonators in Si/C rods

In this paper, we employed multilayer ring resonators in a silicon rod base structure to realize 6-channel and 8-channel demultiplexers based on two-dimensional photonic crystals. Both the main rings and basic structures are composed of silicon rods, and the interior rings of the multilayer rings are composed of carbon. Employing silicon and carbon rods of different radii in multilayer ring resonators enhanced the coupling efficiency between the rings and waveguides. The average quality factor and power transmission efficiency were 4320 and 93%, respectively. Crosstalk values from \(-11\) to ?46 dB in conjunction with the mentioned characteristics suggest the use of the device for optical communication applications. The compact size of the proposed structure and the materials used make the proposed demultiplexer suitable for optical integrated circuits.     

Fabrication and characterization of stacked ZnO and ZnOGa2O3 layers for the realization of bulk acoustic wave resonated membranes

ZnOGa₂O₃ alloys have been deposited by electron beam co-evaporation technique below the piezoelectric radio frequency magnetron sputtered ZnO films, with the aim of reducing the compressive stress due to the piezoelectric zinc oxide elaborated by radio frequency magnetron technique. The structural characterizations of the Ga₂O₃ thin films show an amorphous structure. Co-evaporating gallium oxide with zinc oxide has improved the optical and structural qualities of the e-beam zinc oxide films. Thus, deposing compressive rf magnetron sputtered piezoelectric ZnO on tensile thin layers of ZnOGa₂O₃, has reduced the stress and improved the structural quality of the realized bulk acoustic wave resonators. The fabrication of less stressed ZnO resonators has permitted to liberate partially our membranes by attacking the silicon substrate on which the resonator is realized. Finally, hyper frequency characterizations have been done by a network analyzer to study the influence of the silicon substrate thickness on the piezoelectric activity.     

Effects of Material and Dimension on TCF,Frequency, and Q of Radial Contour Mode AlN-on-Si MEMS Resonators

This paper investigates the effects of material and dimension parameters on the frequency splitting, frequency drift, and quality factor (Q) of aluminium nitride (AlN)-on-n-doped/pure silicon (Si) microelectromechanical systems (MEMS) disk resonators through analysis and simulation. These parameters include the crystallographic orientation, dopant, substrate thickness, and temperature. The resonators operate in the elliptical, higher order, and flexural modes. The simulation results show that i) the turnover points of the resonators exist at 55 °C, –50 °C, 40 °C, and –10 °C for n-doped silicon with the doping concentration of 2×1019 cm–3 and the Si thickness of 3.5 μm, and these points are shifted with the substrate thickness and mode variations; ii) compared with pure Si, the modal-frequency splitting for n-doped Si is higher and increases from 5% to 10% for all studied modes; iii) Q of the resonators depends on the temperature and dopant. Therefore, the turnover, modal-frequency splitting, and Q of the resonators depend on the thickness and material of the substrate and the temperature. This work offers an analysis and design platform for high-performance MEMS gyroscopes as well as oscillators in terms of the temperature compensation by n-doped Si.     

Thermal effect analysis of silicon microring optical switch for on-chip interconnect

The silicon microring resonator plays an important role in large-scale, high-integrability modern switching matrixes and optical networks, as silicon photonics enables ring resonators of an unprecedented compact size. But as the nature of resonators is their sensitivity to temperature, their performances are vulnerable to being affected by thermal effect. In this paper, we analyze the dominant thermal effects to the application of silicon microring optical switch. On the one hand we theoretically analyze and experimentally measure the thermal crosstalk among adjacent microring optical switches with different distances, and give possible solutions to minimize the affect of thermal crosstalk. On the other hand we analyze and measure the thermooptic dynamic response of microring switch; the experiment shows for the thermal-tuning that the rising edge is around 2μs, and the falling edge is around 35μs. We give the explanation of the asymmetric rise-time and fall-time.     

Optical Quality Improvement of Si Photonic Devices Fabricated by Focused-Ion-Beam Milling

Focused-ion-beam directly milling strategy was used to fabricate photonic resonators on crystalline silicon-on-insulator substrate. In order to reduce damages such as implanting ions, amorphous layers and re-deposition process which are induced by the ions, a sacrificed silica layer was used as an etching mask and a silicon thermal oxidation process was performed. The transmission spectra of both photonic crystal cavities and micro-ring resonators were measured. The resulting data demonstrate that the Q factors are significantly improved after the oxidation treatment.      

Tunable Solidly Mounted Thin Film Bulk Acoustic Resonators Based on BaxSr1−xTiO3 Films

Electrically tunable solidly mounted thin film bulk acoustic resonators based on Ba_xSr_1-xTiO₃ films are reported for the first time. The films are acoustically isolated from the silicon substrate by a Bragg reflector stack. Applying DC bias induces piezoelectric effect and an acoustic resonance at approximately 4 GHz. Under 10 V applied DC bias the resonance frequency of the resonators based on Ba_0.25Sr_0.75TiO₃ films is tuned 1.2% to lower frequencies. The Q-factor of these resonators is approximately 120, and the electromechanical coupling coefficient is 0.5%. The resonant frequency of the BaTiO₃ based resonators shifts upwards 1.3% under 10 V DC bias, and the -factor is approximately 30, with an electromechanical coupling coefficient of 6.2%.     

基于硅基等离子超表面的可调太赫兹调制器

由于硅对太赫兹的调制效果较差,所以从理论上和实验上研究了基于硅基等离子诱导透明(PIT)超表面的太赫兹调制器。研究结果发现在透射光谱中可以观察到明显的透明窗口,该透明窗口是由2个谐振器之间的近场耦合引起的。实验结果表明,随着泵浦光功率的增加,透明窗口出现了蓝移。当光泵功率从0 m W增加到700 m W时,0.70 THz处的振幅调制深度可以达到80.75%,同时研究了它的慢光效应。设计的这种新型的超表面结构增强了硅的调制效果,提供了一种实际应用的可能。     

光激励微型硅谐振器研究

本文介绍了一种可以形成新型光纤传感器的微型硅谐振器，其基本原理是微型硅谐振器在调制光的光热作用下产生谐振，被测物理参数使谐振频率发生改变．文中给出了用单晶硅制作桥型微谐振器的方法，研究了微型谐振器在光激励下产生振动的机理．     

Design of a Silicon Beam Resonator for a Novel Gas Sensor

研究了一种基于硅悬臂梁谐振器的新型气体传感器.该传感器在敏感环境中,可同时获得敏感膜电导率和质量变化,测量被测气体分子的荷质比,具有高灵敏度和高选择性.根据这一原理,针对气体传感器的需求,设计了硅悬臂梁谐振器化学传感器结构,进行了仿真优化,并采用MEMS表面牺牲层工艺制备该器件,激光频率仪测量验证了该微型谐振梁的谐振频率.     

基于硅悬臂梁谐振器的新型气体传感器

研究了一种基于硅悬臂梁谐振器的新型气体传感器.该传感器在敏感环境中,可同时获得敏感膜电导率和质量变化,测量被测气体分子的荷质比,具有高灵敏度和高选择性.根据这一原理,针对气体传感器的需求,设计了硅悬臂梁谐振器化学传感器结构,进行了仿真优化,并采用MEMS表面牺牲层工艺制备该器件,激光频率仪测量验证了该微型谐振梁的谐振频率.     

Recent Progress in High-Speed Silicon-Based Optical Modulators

The evolution of silicon optical modulators is recalled, from the first effect demonstrations to the characterization of high-performance devices integrated in optical waveguides. Among possibilities to achieve optical modulation in silicon-based materials, the carrier depletion effect has demonstrated good capacities. Carrier depletion in Si and SiGe/Si structures has been theoretically and experimentally investigated. Large phase modulation efficiency, low optical loss, and large cutoff frequency are obtained by considering simultaneously optical and electrical structure performances. Integrated Mach-Zehnder interferometers and resonators are compared to convert phase modulation into intensity modulation. Finally, recent results on high-speed and low-loss silicon optical modulator using an asymmetric Mach-Zehnder interferometer are presented. It is based on a p-doped slit embedded in the intrinsic region of a lateral pin diode integrated in a silicon-on-insulator waveguide. This design allows a good overlap between the optical mode and carrier density variations. An insertion loss of 5 dB has been measured with a -3 dB bandwidth of 15 GHz.     

Influence of substrate conductivity on characteristics of ZnO/SiO2-diaphragm piezoelectric resonators

Most of the ZnO/SiO2-diaphragm piezoelectric composite resonators on silicon substrates exhibit Q-factors of the anti-resonance much lower than those of the resonance. It is demonstrated both theoretically and experimentally that this is caused by the conductivity of the substrate.     

Nonlinear vibrations and hysteresis of micromachined silicon resonators designed as frequency-out sensors

Experimental observation of nonlinear vibrations and hysteresis of micromachined silicon resonators is reported. The experimental results are explained using a simple model in which the restoring force acting in the resonator contains a small cubic term. The effects will impose a limit to the maximum amplitude which can be excited while still maintaining reliability of these devices as frequency-out sensors.     

Plucked excitation of micromachined silicon DETF resonators

A mechanism for driving micro-mechanical silicon double-ended tuning fork (DETF) resonators by statically deforming and then releasing the tines is described. In this way, the structure vibrates at its natural frequency and the influence of the driving force is removed     

Less than 1 dB per meter propagation loss of silica waveguidesmeasured using a ring resonator

Phosphorus doped silica on silicon waveguide propagation loss, bend loss and their polarization dependence have been measured using a set of different radii ring resonators. For a 30 mm ring radius a finesse of 132 was measured and the inferred propagation loss was 0.85 dB/m, the lowest value yet reported. To characterize the finesse of the high Q resonator we proposed and used for the first time a stable Er⁺³ fiber grating laser source which was thermally tuned. This configuration provides improved and accurate measurements capability for finesse values in the range well beyond 100