共查询到20条相似文献,搜索用时 326 毫秒
1.
A shielded velocity-matched Ti:LiNbO3 optical modulator is investigated, focusing on the characteristics of the traveling-wave (TW) electrode and the optical waveguide. The optical waveguide is analyzed and its parameters are determined using the newly developed modified-step-segment method (MSSM). The TW electrode is analyzed using the second-order triangular element quasi-TEM finite element method (FEM). By taking the thickness of the coplanar waveguide (CPW) traveling-wave (TW) electrode into consideration, it is confirmed that there is an optimum overlaid layer thickness for a given electrode thickness. It is also shown that very wide modulation bandwidth can be attained by using the optimum CPW TW electrode thickness and overlaid layer thickness 相似文献
2.
Reem Song Hyun-Chae Song Steier W.H. Cox C.H. 《Quantum Electronics, IEEE Journal of》2007,43(8):633-640
Analysis, design, and experimental demonstration of polymer Mach-Zehnder (MZ) modulators with a newly proposed in-plane coplanar waveguide (CPW) electrode are presented in this paper. Compared to the conventional CPW electrode, the new in-plane CPW configuration significantly enhances the overlap factor between microwave and optical wave by 40% from the theoretical calculations. Different from polymer modulators using the traditional microstrip electrodes, this structure can suppress dc bias voltage drift and widen modulation bandwidth. Using CLD1/APC and AJL8/APC electrooptic polymers, MZ modulators using the in-plane CPW are fabricated and tested. The measured Vpi's of the MZ with 15-mum gap spacing and 2 cm electrode length are 5.4 and 9.5 V at 1.55 mum for the AJL8/APC and CLD1/APC devices, respectively. The evaluated Upsi33's are 46 pm/V for the AJL8/APC and 26 pm/V for the CLD1/APC MZ. The dc bias stability is tested and compared for both the microstrip and the in-plane CPW electrode modulators. Experimental results show that the in-plane CPW modulator greatly improves the bias stability. From the microwave measurement, the microwave signal loss of the modulator using the in-plane CPW is much reduced to 0.2 dB/cmradicGHz, while 0.7 dB/cmradicGHz using the microstrip. 相似文献
3.
Gopalakrishnan G.K. Burns W.K. McElhanon R.W. Bulmer C.H. Greenblatt A.S. 《Lightwave Technology, Journal of》1994,12(10):1807-1819
The design, fabrication and characterization of a traveling wave Ti:LiNbO3 Mach-Zehnder interferometric modulator are discussed. The dependence of the velocity match condition on electrode thickness and wall angle is demonstrated experimentally and with finite element calculations. A set of test electrode structures is fabricated to study electrical losses in the modulator electrode. Loss coefficients are assigned to different sections of the device, and dielectric and radiative losses are shown to play an important role at high frequencies. This information is used in conjunction with finite-element calculations to develop accurate models for both the electrical and optical responses. The frequency dependence of the half-wave voltage is measured and shown to be in good agreement with a model 相似文献
4.
Chew W. Bajuk L.J. Cooley T.W. Foote M.C. Hunt B.D. Rascoe D.L. Riley A.L. 《Electron Device Letters, IEEE》1991,12(5):197-199
Coplanar waveguide (CPW) low-pass filters made of YBa2Cu3O7-δ (YBCO) on LaAlO3 substrates, with dimensions suited for integrated circuits, were fabricated and packaged. A complete filter gives a true idea of the advantages and difficulties in replacing thin-film metal with a high-temperature superconductor in a practical circuit. Measured insertion losses in liquid nitrogen were superior to the loss of a similar thin-film copper filter throughout the 0- to 9.5-GHz passband. These results demonstrate the performance of fully patterned YBCO in a practical CPW structure after sealing in a hermetic package 相似文献
5.
Kwok Wah Hui Kin Seng Chiang Boyu Wu Zhang Z.H. 《Lightwave Technology, Journal of》1998,16(2):232-238
Different electrode configurations for LiNbO3-based Mach-Zehnder traveling-wave electrooptic modulators are analyzed. It is found that the Z-cut coplanar waveguide (CPW) configuration provides the best compromise between the characteristic impedance, the half-wave voltage, and the driving power. To increase the bandwidth and simultaneously reduce the half-wave voltage, an optimum design of multisection phase reversal electrode is proposed. To verify the theoretical predictions experimentally, two modulators, both using the Z-cut LiNbO3 CPW configuration, were fabricated and characterized, one with an optimized five-section phase reversal electrode and the other with a conventional single-section electrode. By comparing the performances of these two devices, it is confirmed that significant improvements on the bandwidth to half-wave voltage ratio and the flatness of the frequency response can indeed be obtained from using an optimized multisection phase reversal electrode 相似文献
6.
Multiple-quantum-well (MQW) optical modulator structures using the quantum-confined Stark effect (QCSE) manifested by the application of an electric field induced by a propagating surface acoustic wave (SAW) are proposed. The magnitudes of the parallel E ∥ and perpendicular E ⊥ electric-field components are computed to determine the electroabsorption and change of index of refraction for the AlGaAs-GaAs system. The proposed structures are shown to be less cumbersome than conventional p-i-n configurations used to impress E . In addition, an enhanced performance Bragg modulator/switch which utilizes the QCSE as well as the acoustic phase grating produced by the SAW beam is described 相似文献
7.
Safwat A.M.E. Zaki K.A. Johnson W. Lee C.H. 《Microwave and Wireless Components Letters, IEEE》2002,12(4):128-130
New designs of coplanar waveguide (CPW)-microstrip, CPW-stripline, conductor backed CPW (CBCPW)-microstrip, and CBCPW-stripline transitions are presented. Simulation using the high frequency structures simulator (HFSS) shows that the return loss of the CPW-microstrip transition is less than -25 dB up to 11 GHz. Similarly is the CPW-stripline transition. In the case of two back to back CBCPW-stripline transitions, the return loss is less than -22 dB up to 9 GHz. Experimentally, the S 11 of two back to back CBCPW-microstrip transitions on an alumina substrate is less than -15 dB up to 25 GHz 相似文献
8.
Ho-Gyeong Yun Kwang-Seong Choi Yong-Hwan Kwon Joong-Seon Choe Jong-Tae Moon 《Advanced Packaging, IEEE Transactions on》2008,31(2):351-356
We have developed 40-Gb/s traveling-wave electroabsorption-modulator-integrated distributed feedback laser (TW-EML) modules using several advanced technologies. First, we have adopted a selective area growth (SAG) method in the fabrication of the 40-Gb/s EML device to provide active layers for the laser and the electroabsorption modulators (EAMs) simultaneously. The fabricated device shows that the measured 3-dB bandwidth of electrical-to-optical (E/O) response reaches about 45 GHz and the return loss (S11) is kept below -10 dB up to 50 GHz. For the module design of the device, we mainly considered electrical and optical factors. The measured S11 of the fabricated 40 Gb/s TW-EML module is below -10 dB up to about 30 GHz and the 3-dB bandwidth of the E/O response reaches over 35 GHz. We also have developed two types of coplanar waveguide (CPW) for the application of the driver amplifier integrated 40 Gb/s TW-EML module, which is a system-on-package (SoP) composed of an EML device and a driver amplifier device in a module. The measured S11 of the two-step-bent CPW is below -10 dB up to 35 GHz and the measured S11 of the parallel type CPW is below -10 dB up to 39 GHz. 相似文献
9.
Namordi M.R. Mogro-Campero A. Turner L.G. Hogue D.W. 《Microwave Theory and Techniques》1991,39(9):1468-1474
A 50-Ω coplanar waveguide (CPW) resonator designed for a fundamental frequency of about 4.75 GHz was fabricated on LaAlO3 . Two versions were fabricated: the first using 1.9-μm-thick gold and the second using 0.6-μm-thick YBa2Cu3O 7. The devices were identically packaged and tested at 77 K. It was found that the high-temperature superconductor (HTS) resonator had a surface resistance, R s, about six to nine times lower than the Au one. At 45 K, the R s of the HTS resonator decreases by another factor of 4 compared with its 77 K value. Device characteristics for the HTS resonator are presented 相似文献
10.
《Quantum Electronics, IEEE Journal of》1989,25(7):1682-1690
A theoretical investigation is presented of the dependence of electroabsorption in GaAs/AlxGa1-xAs multiple-quantum-well (MQW) structures on the MQW parameters (Al mole fraction x , well thickness L z barrier thickness L b and interface quality) and on the applied electric field studied. The on/off ratio of a modulator using MQWs with x =0.45, L z=75 Å, and L b=78 Å is predicted to increase by 20% compared to that of a modulator using MQWs with x =0.3, L z =100 Å, and L b=100 Å, when the MQW total active region thickness is 1 μm 相似文献
11.
Colodro F. Torralba A. Laguna M. 《IEEE transactions on circuits and systems. I, Regular papers》2008,55(3):775-785
A new Continuous-Time (CT) sigma-delta modulator (SDM) based on the well-known asynchronous SDM is proposed in this paper. To this end, the flash quantizer and the digital-to-analog converter (DAC) in a multibit (MB) CT-SDM clocked at a rate fmax are replaced by a single-bit (SB) comparator with hysteresis clocked at a higher rate fs and a SB-DAC, respectively. By proper selection of the hysteresis in the comparator and the ratio F = fs/fmax, the performances of both modulators are shown to be equivalent. The comparator with hysteresis and the loop filter produce, in the modulator output, a limit cycle of frequency /max which is modulated by the input signal. Therefore, the modulator output can be considered to be a pulsewidth (PW) modulated signal with a frequency approximately equal to /max, and the proposed modulator is called a PW-SDM. Despite the high sampling rate of the comparator output, the integrators and the SB-DAC of the proposed modulator have the same speed requirements as those of the equivalent conventional MB-SDM. On the other hand, in the proposed modulator there are not MB (analog-to-digital or digital-to-analog) converters. Therefore, for a given set of specifications, the proposed PW-SDM is expected to consume less power and area than its equivalent conventional MB modulator. 相似文献
12.
Ackerman E. Wanuga S. Kasemset D. Daryoush A.S. Samant N.R. 《Microwave Theory and Techniques》1993,41(8):1299-1306
We fully analyze the analog performance of an external modulation fiber-optic link. We express relevant figures of merit-including gain, noise figure, third-order intermodulation distortion, AM compression, and dynamic range-in terms of the microwave scattering matrices of the modulator and detector circuits, and we predict the modulator bias condition promoting optimum link performance. Our predictions match the measured gain, noise figure, and dynamic range of an experimental 870-930 MHz external modulation fiber-optic link. Maximum spurious-free dynamic range-77 dB·MHz2/3 (117 db·Hz2/3 )-occurs when the modulator is biased at its halfwave voltage, where the optical throughput is nearly pinched off 相似文献
13.
Lahiji R. R. Sharifi H. Katehi L. P. B. Mohammadi S. 《Microwave Theory and Techniques》2010,58(1):48-56
14.
Low-loss coplanar waveguide (CPW) transmission lines integrated on a standard (5 -10 Omega ldr cm) silicon substrate are realised by using an artificial dielectric shield with a very high in-plane dielectric constant. The shield consists of a 30 nm-thick Al2O3 film sandwiched by two 100 nm-thick aluminium layers patterned into lattices of mum-size elements. The individual metallic elements are micro-patterned to suppress the flow of eddy currents at microwave frequencies. Inserted below the CPW, the shield blocks the electric field of the line from entering the silicon substrate. The resulting line attenuation (measured up to 25 GHz) is comparable to that of identical CPWs built on a high-resistivity silicon wafer. 相似文献
15.
An MQW electro-absorption optical modulator integrated with low-loss input and output waveguides is proposed to achieve larger modulation bandwidth with a shorter modulation region, keeping the total device length large enough for easy fabrication and packaging. A fabricated 1-mm-long modulator with a modulation-region length of 50 μm shows a low insertion loss (7 dB), low driving voltage (V10 dB=2.6 V), and large modulation bandwidth f3 dB =40 (GHz) extrapolated from measurements up to 20 GHz. This modulator is suitable for application to ultra-high-speed fiber transmission systems 相似文献
16.
The microwave characteristics of a traveling-wave electrode in electrooptic modulators on z -cut LiNbO3 crystals with buffer layers with various dielectric constants are calculated by a quasi-TEM analysis. The theoretical results are compared with the measured results on z -cut crystals for coplanar waveguide (CPW) electrodes. The agreement between the calculated and the measured results is good 相似文献
17.
Sang-Shin Lee Garner S.M. Chuyanov V. Hua Zhang Steier W.H. Fang Wang Dalton L.R. Udupa A. Fetterman H.R. 《Quantum Electronics, IEEE Journal of》2000,36(5):527-532
We have synthesized a novel electrooptic (EO) polymer based on a high μβ chromophore incorporating tricyanobutadiene acceptors. A crosslinked polyurethane network was also adopted to enhance its thermal stability. In order to find the optimum poling condition for the polymer, the influence of the electric poling profile on optical characteristics such as the EO effect, thermal stability, and damage was investigated. Then a high-speed intensity modulator using the EO polymer was designed and fabricated. The measured half-wave voltage Vπ was 4.5 V at the wavelength of 1.31 μm. Accordingly, the achieved EO coefficient r33 was as high as 25 pm/V, and the thermal stability of the poled polymer was as high as 95°C. Finally, the modulator was successfully operated up to 40 GHz 相似文献
18.
19.
《Microwave Theory and Techniques》2009,57(11):2753-2760
20.
Pao Y.-C. Nishimoto C.K. Majidi-Ahy R. Archer J. Bechtel N.G. Harris J.S. Jr. 《Electron Devices, IEEE Transactions on》1990,37(10):2165-2170
High-performance 0.3-μm-gate-length surface-undoped In0.52 Al0.48As/In0.53Ga0.47As/InP high-electron-mobility transistors (HEMTs) grown by molecular beam epitaxy (MBE) have been characterized and compared with a surface-doped structure. At 18 GHz, the surface-undoped HEMT has achieved a maximum stable gain (MSG) of 19.2 dB compared to 16.0 dB for the surface-doped structure. The higher MSG value of the surface-undoped HEMTs is obtained due to the improved g m/g 0 ratio associated with the surface-induced electric field spreading effect. Comparison of identical 0.3-×150-μm-gate devices fabricated on surface-undoped and -doped structures has shown greatly improved gate leakage characteristics and much lower output conductance for the surface-undoped structure. It is demonstrated that the surface potential, modulated by different surface layer designs, affects the charge control in the conducting channel, especially the carrier injection into the buffer, resulting in excess output conductance. Several millimeter-wave coplanar waveguide (CPW) monolithic distributed amplifiers have been successfully fabricated by using the surface-undoped HEMT structure. A high gain per stage distributed amplifier with 170-dB±1-dB small-signal gain across a frequency band of 24-40 GHz, a W -band monolithic integrated circuit with 6.4-dB gain at 94 GHz, and a broad bandwidth distributed amplifier with 5-dB gain across a frequency band of 5 to 100 GHz have been demonstrated by using the surface-undoped structures 相似文献