Fourier analysis of a polymer directional coupler electro-optic switch with two-section cosine-transitive CPWG electrodes: A new theoretical view

By using two-section cosine-transitive coplanar waveguide grounded (CPWG) electrodes, a polymer directional coupler (DC) electro-optic (EO) switch is optimally designed with both relaxed fabrication tolerance under cross-state and high switching speed over 100 GHz. As a new theoretical view, based on Fourier transformation, a Fourier analysis technique and related formulas are presented with respect to the time- and frequency-domain responses under high-speed modulating and switching operations. Under 1550 nm, the bar- and cross-state voltages are 0 and 2.669 V, respectively, for the switch with a total length of 8378 μm. The insertion loss and crosstalk are less than 3.887 and ? 30 dB, respectively. The 3-dB modulating bandwidth and cutoff switching frequency are about 110 and 131.6 GHz, respectively, and the 10–90% rise time and fall time are both about 3.80 ps. Owning to this configuration, its cutoff switching frequency is enhanced to 9 times of that of our previously reported EO switch with two-section separated reversed electrodes, which expands the ultra-high speed and large capacity applications for such switches. The proposed Fourier analysis method can also be adopted to evaluate the responses under the operation of any other form driving signals with Fourier transformation.     

Analysis on skin-effect of a polymer shielded push–pull directional coupler electro-optic switch

By using the extended point-matching method, coupled mode theory, and electro-optic modulation theory, design and optimization are carried out for a polymer shielded push–pull directional coupler electro-optic switch. A novel technique and the relative formulas are presented for analyzing the influences of the skin-effect on the microwave characteristic parameters and the switching performances. Simulation results show that the voltages of the cross- and bar-states are 0 and ±2.93 V, respectively, and the coupling length is 4.139 mm. Considering the influences of the skin-effect, the cutoff switching frequency is 172 GHz, the insertion loss is in the range of 1.920–1.975 dB, the crosstalk is less than ?20 dB, and the switching time is 31.18–31.40 ps within the range of the switching frequency from 0.72 to 172 GHz. The designed switch exhibits superior characteristics including good impedance match, low switching voltage, and high cutoff switching frequency.     

Simulation and optimization of a polymer 2×2 multimode interference-Mach Zehnder interferometer electro-optic switch with push-pull electrodes

Structural model and design technique are proposed for a polymer 2×2 multimode interference-Mach Zehnder interferometer electro-optic (MMI-MZI EO) switch with push-pull electrodes. The electric field distribution is analyzed by the conformal transforming method and image method. To get the minimum mode loss and half-wave voltage, the parameters of the waveguide and electrodes are optimized, such as the core width, core thickness, buffer layer thickness, size of the MMI couplers and the modulating region, electrode thickness, electrode width, and electrode gap. Switching characteristics are analyzed, including the output power, crosstalk, and wavelength shift. Simulation results show that the half-wave voltage is 0.74 V, the optical 3 dB bandwidth is 12.66 GHz, and the crosstalk is less than −30 dB for the designed device.     

Analysis of response characteristics for polymer directional coupler electro-optic switches

By using the coupled mode theory, electro-optic modulation theory, conformal transforming method, image method and the proposed transfer matrix technique, novel expressions for the both cases of the low switching frequency and the ultra-high switching frequency are presented for analyzing the transmission powers, rise time, fall time, switching time and switching frequency of the polymer directional coupler electro-optic switches. Simulation results of an application based on the technique show that, the switching voltage and coupling length are about 1.457 V and 4.374 mm, respectively, and the switching time and cutoff switching frequency are about 32.8 ps and 114.7 GHz, respectively, for the designed switch.     

Design of a polymer directional coupler electro-optic switch using two-section reversed electrodes

By using the coupled mode theory, electro-optic modulation theory, conformal transforming method and image method, the structure is designed, the parameters are optimized, and the characteristics are analyzed for a polymer directional coupler electro-optic switch with two-section reversed electrodes. Simulation shows that the designed device exhibits excellent switching functions. Under the operation wavelength of 1550 nm, the electro-optic coupling region length is 4751 μm, the cross-state and bar-state voltages are about 1.22 and 2.65 V, and the insertion loss and crosstalk are less than 2.21 and −30 dB, respectively. By slightly adjusting the state voltages, the blight of the fabrication errors on the switching characteristics can be easily eliminated. The calculation results of the presented technique are in good agreement with those of the beam propagation method (BPM).     

Thermo-optic multimode interference switches with air and silicon trenches

A novel thermo-optic multimode interference (MMI) switch with air and silicon trenches was proposed, and the performance of the switch was simulated. In the design, one heating electrode is used to alter the refractive index at a spot image which changes the phase of this image to realize the switching function. The simulation results clearly indicate that the MMI switch can satisfy −39 dB crosstalk at two states. The electric power consumption for the MMI switch with these trenches is less than half of that of a conventional MMI switch.     

Systematic investigation of silicon digital 1×2 electro-optic switch based on a microdisk resonator through carrier injection

We perform a systematic investigation on the silicon digital 1×2 electro-optic switch based on a microdisk resonator with the refractive index tuned by carrier injection and extraction. Analytical expressions are proposed to quantify the crosstalk, insertion loss and switching time, and then they are used to analyze the effect of the coupling-in/out coefficient, internal loss, and quality factor. Both electron beam lithography and photolithography were employed to construct the asymmetrically coupled microdisk resonator integrated with a p-i-n diode. A high-performance switch has been demonstrated with a crosstalk of less than −20 dB, a switching time of ∼2 ns, as well as a power consumption of 0.46 mW. Moreover, the switching of optical signals with high data rates has been characterized and analyzed under different working conditions.     

Y-branch - the key component for crosstalk reduced optical switches: modelling analysis

A novel design method for switching devices is demonstrated based on waveguide structures with Y-branches and abrupt waveguide changes as key elements. A combination of BPM calculation and eigenmode analysis is shown to be a promising tool to obtain deep insight into the physical mode behaviour. Based on the analysis, a mode converter to match the eigenmodes in amplitudes and phase can be developed and introduced as a correcting device. This method is demonstrated for the crosstalk compensation of a digital switch (DOS) and a Δβ-reversal switch. A crosstalk of about −20 dB can be reduced to −40 dB by this method. This revised version was published online in November 2006 with corrections to the Cover Date.     

Design of an insensitive-polarization all-optical switch based on multimode interference structures

This paper presents a new design for an insensitive-polarization all-optical switch using 2 × 2 multimode interference (MMI) couplers. The switching structure can operate at central operating wavelength 1550 nm for both polarizations. A nonlinear directional coupler is used to realize the phase shifter and therefore switching mechanism is obtained. The transfer matrix method and beam propagation method are used to design and optimize the whole device structure.     

Fabrication and characterization of polymer thermo-optic switch based on mmi coupler

The 2 × 2 polymer thermo-optic switch based on MMI coupler is realized. This device is fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of −36.2 dB is achieved at cross and bar states. A power consumption of 1.85 mW is applied to change the state of the switch from the cross to the bar state. A switching time of less than 0.7 ms is traced to change a state of the realized switch.     

Theoretical investigation of a polymer Mach–Zehnder electro-optic switch using 2N + 1 serial-coupled microrings with ultralow-driving voltage

Universal structure and thorough analysis are proposed for a kind of (2N + 1)th order polymer microring resonator Mach–Zehnder interferometer (MRR-MZI) electro-optic (EO) switch. Formulas and expressions of output power, insertion loss and crosstalk are derived, and detailed design and optimization are carried out. Analytical results indicate that, besides the first-order MRR-MZI EO switch (N = 0), other devices for N ≥ 1 can all perform normal switching function, and 5 ≥ N ≥ 2 is preferred for dropping the crosstalk below ?10 dB. For the four MRR EO switches (N = 2–5), their switching voltages are 0.99, 0.73, 0.57 and 0.47 V, respectively; their insertion losses are within the range of 1.15–2.26 dB at bar state, whereas those are within the range of 1.95–2.42 dB at cross state; their crosstalks are within the range of 11.04–17.82 dB at bar state, whereas those are within the range of 10.34–12.51 dB at cross state. Compared with the traditional MZI EO switch, the voltage–length product (0.21 V mm) of this switching element is decreased by ~111.7 times under the same waveguide parameters. Therefore, due to small footprint size and extremely low switching voltage, this switching configuration can be densely integrated onto optoelectronic chips.     

Design of a spectrum-expanded polymer Mach�CZehnder interferometer electro-optic switch using two-phase generating couplers

A novel structure, thorough analysis and design technique are presented for a kind of polymer Mach?CZehnder Interferometer (MZI) electro-optic (EO) switch consisting of two-phase generating couplers (PGCs). By optimizing the PGCs structure, the output spectrum of the two PGCs based MZI EO switch is greatly expanded to almost six times of that of the traditional MZI EO switch with two 3?dB directional couplers. Under a central wavelength of 1550 nm, the driving voltages of the designed switch are as low as about 0 (ON state) and ±0.925?V (OFF state) with an EO region length of 5000???m. A wide spectrum more than 350 nm (1380??1730?nm) is achieved, and within this wavelength range, the crosstalk is less than ?30?dB, and the insertion loss is less than 5.91?dB which is larger than that of the traditional MZI EO switch due to the longer waveguide length by introducing two PGCs. The design technique on the two PGCs based MZI EO switch is supported to be reasonable compared with the beam propagation method (BPM). The proposed structure shows potential wide applications especially in optical cross-connect (OXC) and optical add-drop multiplexing (OADM) systems.     

In vitro monitoring of goat-blood glycemia with a microwave biosensor

We used an electromagnetic microwave cavity sensor for real time measurement of the glycemia in goat-blood for three animals. We could determine the concentration of d-glucose in blood in the range of 90–550 mg/dl at the resonance frequency near 4.76 GHz with a bandwidth of 300 MHz. The change in microwave reflection coefficient S₁₁ (due to the variation of d-glucose concentration in blood) was about 16.33 dB, 23.92 dB, 7.66 dB and resonance frequency shift was about 21.78 MHz, 36.29 MHz, 20.77 MHz, respectively, for the three different samples. The in vitro results show the measured signal-to-noise ratio of about 32 dB, and the minimum detectable signal level of about 0.025 dB/(mg/dl). The results clearly show the sensitivity and usefulness of this microwave sensor for these types of biological investigations. This proposed system provides a unique approach for real contactless glucose monitoring and, it may serve as a bloodless glucometer for the calibration of different glucose levels.     

Simulation and optimization of a polymer directional coupler electro-optic switch with push-pull electrodes

Structural model and design technique are proposed for a polymer directional coupler electro-optic switch with rib waveguides and push-pull electrodes, of which the electric field distribution is analyzed by the conformal transforming method and image method. In order to get the minimum mode loss and the minimum switching voltage, the parameters of the waveguide and electrode are optimized, such as the core with, core thickness, buffer layer between the core and the electrode, coupling gap between the waveguides, electrode thickness, electrode width and electrode gap. Switching Characteristics are analyzed, which include the output power, insertion loss, and crosstalk. To realize normal switching function, the fabrication error, spectrum shift, and coupling loss between a single mode fiber (SMF) and the waveguide are discussed. Simulation results show that the coupling length is 3082 μm, push-pull switching voltage is 2.14 V, insertion loss is less than 1.17 dB, and crosstalk is less than −30 dB for the designed device.     

Extracting microwave energy from a cavity by mode conversion at a coupling window

A study is made of the production of high power nanosecond rf pulses by extracting microwave energy from an oversized cavity by means of conversion, at a coupling window, of the high-Q working mode to an auxiliary mode which is strongly coupled to an external load. It is shown that microwave rf pulse compressors with copper storage cavities and energy extraction by mode conversion at a coupling window can provide gains of 5–13 dB with output signal durations of 20–150 ns and peak powers of 5–10 MW in the 3-cm band and 50–100 MW in the 10-cm band. Rf pulses lasting 30 ns with peak powers of 0.5 MW have been obtained experimentally at a frequency of 9.4 GHz with a gain of 9 dB. Zh. Tekh. Fiz. 68, 92–96 (July 1998)     

A 1 × 2 optical switch using one multimode interference region

A 1 × 2 optical switch using only one multimode interference (MMI) region is designed and demonstrated in GaAs/AlGaAs. This design makes a single MMI region works as MMI coupler using paired interference at “off” state and symmetric interference at “on” state. By injecting a current of 110 mA, the measured on/off ratio and crosstalk are 23 dB and 33 dB, respectively in the demonstrated device with GaAs/GaAlAs.     

Self-excitation and establishment of generation in a two-section relativistic diffraction generator

Starting conditions for generation and features of oscillation establishment in a relativistic diffraction generator for different beam current values are numerically studied using the matrix multimode method. The efficiency boost and generation frequency stabilization are found to arise at overlap of two electron mechanisms—excitation of the fundamental oscillation of the system in the region of the 2π-type frequencies with a resonance near the cutoff frequency of the bulk mode nearest to the 2π type in a smooth waveguide.     

Robust 2 × 2 Multimode Interference Optical Switch

A robust 2 × 2 photonic switch based on multimode interference (MMI) effects is proposed. We demonstrate that the device is very tolerant to material modifications and typical fabrication errors. This is a result of the MMI design and the high symmetry of the switch. The key parameter for the operation of the device is that the input light forms a pair of well defined self-images exactly in the middle of the switch. The index modulated regions precisely overlap the positions where these two self-images are formed. By creating identical contact features at these locations, any refractive index change induced in the material as a result of electrical isolation will be replicated in both self-images, and therefore the off-state output will not be altered. In the same way, offset and dimension errors are reflected symmetrically on both self-images and do not seriously affect the imaging. The characteristics of the switch under different scenarios are investigated using the finite difference beam propagation method. By employing this configuration, crosstalk levels better than −20 dB are achievable over a wavelength range of 100 nm while maintaining polarization independence.     

Experimental studies of a gyroklystron operating in the field of a permanent magnet

We have developed and tested a gyroklystron operating with the second harmonic of the electron cyclotron frequency at a frequency of 32.3 GHz in the field of a permanent magnet. In the two-and three-cavity versions of the gyroklystron, the peak power of the output radiation reached 320 kW with an efficiency of 30%, an amplification coefficient of 20–25 dB, and an operating frequency bandwidth of 0.05%. In the wide-band version of the gyroklystron, the amplification bandwidth was equal to 0.27% for an output power of 200 kW and an amplification coefficient of 13 dB.     

Novel optic-fiber switches based on the wobble-type MEMS electromagnetic microactuator

Some novel optic-fiber switches based on an MEMS electromagnetic microactuator are developed in this paper and their design, fabrication and performance are described. A new kind of wobble-type MEMS electromagnetic microactuator is successfully developed, which can drive mirrors to enter or leave the optical path of a switch. It is layered, composed of two stators and one wobble disc, which improve the output torque of the actuator. Finally, 1×2, 2×2, 1×4 and 1×8 single mode optic-fiber switches, which have been fabricated, are measured. The operating voltage is less than 8 V, switching time is less than 5 ms, insertion loss is less than 0.8 dB, crosstalk is 60 dB, and extinction ratio is 60 dB. These optic-fiber switches show a promising future in optical fiber communication systems.