Summary A new analog tunable Ka‐band band‐stop filter is proposed on high resistivity silicon (HRS) substrate using radio frequency microelectromechanical systems (RF MEMS) varactors for satellite and radar applications. The designed filter uses a λ/4 comb‐line resonator on the center line of a coplanar waveguide (CPW) with a new uncommon defected ground structure (DGS). Using the DGS in the proposed structure not only decreases the lateral size of the filter but also increases the quality factor. The tuning range of the proposed filter is 29.8–35.6 GHz with a maximum actuation voltage of 44.5 V and a band rejection between 37 and 45 dB. The quality factors of the designed filter in the up and down states of the MEMS varactors are 162 and 292, respectively. The equivalent circuit model of the filter is exactly extracted, and DGS dimensions are optimized. Based on the frequency simulation using ANSOFT HFSS 14, the insertion loss of the designed filter is about 0.51 dB in the 0–20 GHz range and 2 dB in the 0–15 GHz range in, respectively, up and down state of the bridge. The return losses are 0.51 and 0.33 dB at the center frequency for the up‐ and down‐state configuration of the bridge. A step‐by‐step fabrication process is also proposed for designing the band‐stop filter. High quality factor, small size, and improved structure are the advantages of the proposed design.

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Optical switches are very important devices for high-speed optical communications, optical digital integrated circuits, and optical conditioners such as analog to digital converters. High speed optical switching is one of the most important topics in this domain. For this purpose, we will investigate the effect of two-photon absorption phenomenon on switching speed in a novel structure. In this paper, Kerrlike nonlinear ring resonator coupled to MZI with considerable two-photon absorption coefficient as a fast optical switch is investigated.Keywords-Two-photon absorption based optical switching, MZI, and Ring-resonator L Introduction Optical teleconmnunication networks with transmission capability beyond 100 Gb/S require ultra fast signal processing such as demultiplexing, add-drop functions, wavelength conversion, and many other interesting applications. Interferometer based all-optical switching using ultra fast nonlinear processes in semiconductor optical amplifiers (SOAs) have been widely investigated for these applications [1]. Among various configurations, the symmetric MZI provides the highest flexibility and shortest switching windows [1]. So far, 160 Gb/S alloptical de-multiplexing has been successfully demonstrated with a hybrid integrated symmetric MZIswitch [1,21. In this switch, in each arm of the interferometer a semiconductor -optical amplifier are excited by short control pulses with an appropriate time delay. This particular switching mechanism cancels out the slow relaxation leading to nearly ideal switching window. However repetition rates higher than 500 Gb/S require sub-picosecond nonlinearities become of prime importance considerably influencing the switching performance [1]. Also, during the past few years, the demand for optical telecommunications has boomed. In order to satisfy this demand, new optical switches are required to replace the electrical switches used until now. In this work, we will try to investigate the optical switching properties of MZI and ring resonator as well as considerable two-photon absorption coefficient. Using ring-resonator having considerable two-photon absorption coefficient coupled to one arm of MZI, will decrease the switching threshold and create high speed switching. For simulation of our idea, the nonlinear Schr6dinger equation for Kerr-like nonlinear ring resonator and MZI with nonzero real and imaginary parts -of third order susceptibility [3-6] is solved using finite difference time domain (FDTD) method. The organization ofthis paper is as follows. In section 11, a new structure based on MZI and twophoton absorption for optical switching is proposed. Also, the mathematical formalism in this section is presented. Simulated results and discussion on these results is presented in section III. Finally, the paper is ended with a conclusion.IL Fast Optical Switching using Two-photon Absorption Fig. (1) shows our proposal for high speed and low threshold all-optical switch. This structure includes three linear directional coupler with coupling coefficients K,...

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