Measured Switching Time Research Articles

Wavelength Bistability and Switching in Two-Section Quantum-Dot Diode Lasers

We report lasing wavelength bistability with respect to applied bias on the saturable absorbers in two-section mode-locked quantum dot lasers. We show data from three different devices exhibiting wavelength bistability. All lasers display wavelength bistability. Only one lasing wavelength is present at a time, with all other wavelengths totally quenched. The switchable ranges (the wavelength difference between two bistable lasing branches) are different for all three lasers and in one device can be manipulated by changing the current injection. All lasers show the remarkable property of switching only in integer multiples of about 8 nm. The bistable operation can be explained by the interplay of the cross-saturation and self-saturation properties in gain and absorber, and the quantum-confined Stark effect in absorber. The measured switching time between bistable wavelengths is 150 ps.

A NEW STRUCTURE OF MMI POLYMER THERMO-OPTIC SWITCH WITH A HIGH REFRACTIVE INDEX CONTRAST

The 2 £ 2 MMI polymer thermo-optic switch in a high refractive index contrast (0.102) with a new structure design is realized. This device was fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of i36:2dB has been achieved. Meanwhile the extinction ratio of 36.1dB has been achieved in this device. The polarization dependent loss (PDL) of 0.3dB and Insertion loss of 1.4dB were measured at 1550nm wavelength. In terms of wavelength dependency, the device shows a good performance within C-band wavelength with vacillation of the insertion loss value around 0.88dB. The power consumption of 1.85mW was measured to change the state of the switch from the cross to bar state. The measured switching time was 0.7ms.

The development of an 8 × 8 optical switch

In this paper, a novel 8×8 optical switch, which consists of a MEMS‐based silicon micro‐mirror array and a solenoid‐based bi‐stable mini‐actuator array, is presented. The silicon micro‐mirror array is realized by using a single‐step anisotropic silicon etching process. The anisotropic silicon etching technique is capable of fabricating the self‐aligned micro‐mirror array with high accuracy and high fabrication yield. The mini‐actuator array comprises 64 electromagnetic solenoid‐based bistable actuators integrated with pushing arms. Each micro‐mirror, which is connected to the substrate by a cantilever, can be individually actuated by a mini‐actuator. Because of the bi‐stability of the mini‐actuators, the power consumption of the system can be significantly reduced. When the pushing arm does not contact the cantilever, the micro‐mirror which is under zero external force can precisely reflect optical signals. When the pushing arm pushes up the micro‐mirror, the optical signal passes through under the mirror. The main advantages of this proposed switch include high precision, high fabrication yield, low actuation voltage, low cost, low power consumption, and easy fiber alignment. The optical performance and the dynamic response of the switch are also investigated. The measured insertion loss is about ‐2.2 ∼ ‐3.3 dB, cross‐talk is less than ‐60 dB, and the measured switching time is less than 12 ms.

A bi-stable 2x2 optical switch monolithically integrated with variable optical attenuators

This work presents the development of a novel micromachined 2x2 optical switch monolithically integrated with variable optical attenuators. The proposed device can be easily realized by a standard manufacturing process with single photo mask. The key to realizing this device by such a simple approach is the employment the split-cross-bar (SCB) configuration. With this configuration, the fabrication challenges and layout constraints for accommodating all the sub-components of this dual-function device can be completely eliminated. The monolithically-integrated system has four movable mirrors, two bi-stable mechanisms and six actuators. The switching of optical signals is achieved by moving the mirrors attached on the bi-stable mechanisms using four of the actuators. The attenuation of optical power is carried out by moving the mirrors using the other two actuators and the bi-stable mechanisms. Also, only simple in-plane motions are needed for these sub-components to achieve all the functionalities. In addition, the adaption of bi-stable mechanisms can reduce the power consumption and simplify the actuation scheme. The measured insertion losses for both channels are about 1.0~1.1 dB, and the cross-talk is less than -60 dB. The attenuation range is about 30 dB for a maximum applied voltage of 20 V. Also, the measured switching time is less than 4 ms.

A nanomechanical switch for integration with CMOS logic

We designed, fabricated and measured the performance of nanoelectromechanical (NEMS) switches. Initial data are reported with one of the switch designs having a measured switching time of 400 ns and an operating voltage of 5 V. The switches operated laterally with unmeasurable leakage current in the ‘off’ state. Surface micromachining techniques were used to fabricate the switches. All processing was CMOS compatible. A single metal layer, defined by a single mask step, was used as the mechanical switch layer. The details of the modeling, fabrication and testing of the NEMS switches are reported.

A Single-PLL UWB Frequency Synthesizer Using Multiphase Coupled Ring Oscillator and Current-Reused Multiplier

A single phase-locked loop (PLL) frequency synthesizer for a mode-1 multiband orthogonal frequency-division multiplexing (MB-OFDM) ultrawideband (UWB) system is realized in 0.13-mum CMOS. A current-reused multiply-by-1.5 circuit and a multiphase coupled ring oscillator are adopted to reduce the power consumption. For a 4.488-GHz signal, the measured image sideband is -40 dBc. The measured switching time from 3.342 to 4.488 GHz is 1.5 ns. The area is 0.85times0.9 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the power is 31.2 mW for a 1.2-V supply voltage.

A Novel 4$\, \times \,$4 Optical Switch Using an Anisotropically Etched Micromirror Array and a Bistable Mini-Actuator Array

This letter presents a novel approach to realize a 4 times 4 optical switch. The optical switch consists of a micromachined silicon micromirror array and a bistable mini-actuator array. The micromirror array, which comprises vertical mirrors, cantilevers, and trenches, can be monolithically fabricated by a simple anisotropic silicon etching process in high precision and high yield. The mini-actuator array consists of 16 commercially available bistable actuators integrated with L-shape arms. The advantages of this approach include high precision, easy alignment, high fabrication yield, and low cost. Because of bistable actuation, the power consumption is very low and thus the temperature elevation of a working device is less than 0.3 K. The measured insertion losses of the four channels are between - 1.6 and - 2.3 dB. The measured crosstalk is less than -60 dB, and the measured switching time is about 13 ms.

A Polarization-Independent Subnanosecond 2$\,\times\,$2 Multicast-Capable Optical Switch Using a Sagnac Interferometer

We design and demonstrate a cost-effective 2times2 ultrafast multicast-capable optical switch (MCOS) based on a Sagnac interferometer. The Sagnac interferometer is composed of a LiNbO3 phase modulator (PM) with two polarization-maintaining pigtail fibers and a 3-dB polarization-maintaining coupler. The MCOS works at three states: cross, bar, and multicast, in the entire C-band (1525-1565 nm) by controlling the driven voltage of the PM. Polarization- dependence is eliminated by splicing the pigtail fibers of the PM and the 3-dB coupler with 0degand 90deg angles, respectively. The measured switching time is ~0.6 ns. Multiple 2times2 MCOS elements can be constructed into a large nonblocking N x N MCOS matrix.

Spur-Suppression Techniques for Frequency Synthesizers

A frequency synthesizer with two spur-suppression circuits has been fabricated in 0.18 mum CMOS technology. The chip area is 1.3 mm times 1.3 mm. The frequency synthesizer consumes 18.9 mW from a 1.8-V supply. Compared with the conventional frequency synthesizer without the spur-suppression circuit, the measured reference spur at 8 MHz is reduced by 18 dBc for the first spur-suppression circuit and 31 dBc for the second one. The measured switching time from 1792 to 1824 MHz is 27.89 mus within 20 ppm of the target frequency.

Sub-Microsecond RF MEMS Switched Capacitors

This paper presents fast switching RF microelectromechanical systems (MEMS) capacitors with measured switching times between 150-400 ns. By introducing bent sides on a planar microbeam, it is shown experimentally that the resonance frequency of aluminum bridges is increased by a factor of 25 compared to standard RF MEMS components. In addition, this original shape can be implemented easily in post-processing of complementary metal-oxide-semiconductor circuits. Several designs are presented with measured mechanical resonance frequencies between 1-3 MHz and measured switching times under 400 ns. Using this original approach, sub-microsecond RF MEMS switched capacitors have been designed and fabricated on quartz substrate. Their resulting RF performance is presented with a measured capacitance ratio of 2.3. Reliability tests have also been performed and have demonstrated no significant mechanical behavior variation over 14 billion cycles and a moderate sensitivity to temperature variation.

A novel 2 × 2 MEMS optical switch using the split cross-bar design

In this paper, a novel 2 × 2 MEMS optical switch is presented. The switch, which employs the proposed split cross-bar (SCB) design, intrinsically possesses advantages over typical 2 × 2 MEMS switches of traditional designs, such as the cross-bar design and the mirror-array design. In comparison to the cross-bar switches, the SCB switch does not have the constraint on the mirror thickness which affects fiber alignment significantly. In comparison to the mirror-array switches, the SCB switch requires fewer movable mirrors and thus gives better fabrication yield. The SCB device can be easily fabricated by employing inductively-coupled-plasma etching (ICP) on a silicon-on-insulator (SOI) wafer with one photo-mask. Electro-thermal V-beam actuators integrated with the bi-stable mechanisms are employed to move and latch the movable mirrors of the proposed device. The displacement of the movable mirrors is at least 60 µm under a driving voltage of 40 V. The optical performance and the dynamic response of the SCB switch are also investigated. The measured average insertion loss is less than −1.4 dB with a deviation of 0.08 dB. Also, the measured switching time is about 10 ms.

A MEMS VOA Using Electrothermal Actuators

A comprehensive study of electrothermally driven microelectromechanical system (MEMS) variable optical attenuator (VOA) devices using an H-shaped structure is presented in this paper. Based on its unique structural design, a retroreflection-type VOA of smaller footprint is realized. The repeatability and stability of the static and transient characteristics of attenuation behavior at various ambient temperatures are characterized. The fluctuation of attenuation curves under the same driving voltage at the same ambient temperatures is less than plusmn0.1 dB. Again, comparing the attenuation curves measured at 25 degC to 75 degC and at 25 degC to 12.5 degC, the deviation of attenuation under the same driving voltage is within the 0.6-dB range. Within the 40-dB attenuation range, the measured switching time from nonattenuation state to a particular attenuation state or between two attenuation states is less than 10 ms. This electrothermally actuated MEMS VOA also demonstrates the state-of-the-art dynamic attenuation stability that complies with the Telecordia GR1221 regulations, where the dynamic fluctuation of attenuation at 20 dB is less than plusmn0.36 dB under a vibration testing condition of 20 G periodical shocks with frequency from 20 Hz to 2 kHz

2-bit $X$-Band Reflective Waveguide Phase Shifter With BCB-Based Bias Circuits

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The design and performance of a 2-bit p-i-n diode reflective &lt;formula&gt; &lt;tex&gt;$X$&lt;/tex&gt;&lt;/formula&gt;-band phase shifter are described. This phase shifter uses the spiraphase principle of phase changing. Benzocyclobutene-based bias circuits are used to decrease the insertion loss level and to reduce the fabrication costs. It has been proven that the phase shifter demonstrates insertion loss better than 0.5 dB in the frequency band from 9.75 to 11.5 GHz for all four phase states. The phase shifter is characterized by maximum phase errors of 11&lt;formula formulatype="inline"&gt; &lt;tex&gt;$^{\circ}$&lt;/tex&gt;&lt;/formula&gt; in the frequency band from 9.75 to 11.25 GHz. The measured switching time of the phase shifter is less than 150 ns. </para>

Temperature dependence of a silicon power device switching parameters

This study presents measurements of device switching parameters performed on a commercial power metal-oxide-semiconductor field-effect transistor under high-temperature conditions. Measured switching times show that the device response to being turned off becomes faster at high temperatures. The inverse drain-source current rapidly increases above the 300°C limit. I-V curves indicate that the saturation current in the channel increases with temperature.

Dielectric resonator with discrete electromechanical frequency tuning

A novel approach for discrete frequency tuning of dielectric resonators based on electromechanical actuators such as the microelectromechanical system is presented. The concept is based on the intermodal coupling between the TE/sub 01/spl delta// mode of a cylindrical dielectric resonator and the radially arranged planar slotline resonators. The resonance frequency of the dielectric resonator is changed by switching a resistive load at the open end of each quarter-wave slotline resonator leading to a variation of the coupling between the slotline resonator mode and the TE/sub 01/spl delta// mode of the dielectric resonator. As a consequence, the resonance frequency of the TE/sub 01/spl delta// mode changes. Based on this novel tuning concept, discrete tuning by 5 MHz in 0.25-MHz frequency steps was demonstrated for a test resonator at 2 GHz. The unloaded quality factor is about 12000 and the measured switching time is about 1 ms.

Investigations of rf shunt airbridge switches among different environmental conditions

This paper reports on extensive investigations on capacitive radio frequency (rf) microelectromechanical systems (MEMS) shunt airbridge switches especially among different environmental conditions. Single airbridge switches yield an insertion loss lower than 0.28 dB at 35 GHz and an isolation down to −38 dB at 35 GHz. The capacitance ratio C on/ C off is approximately 60 (best case). The measured temperature dependency of the pull-in voltage was −0.3 V/°C in the temperature range from −25 to 75°C. The measured switching time was 11 μs and the release time 7 μs. More than 5×10 4 switching cycles could be performed in a non-stabilised environment. For optimised switches no self-closing is observed up to 1 W rf power at 30 GHz. The measurement results are in good agreement with the simulated values.

Rb-doped potassium titanyl phosphate for periodic ferroelectric domain inversion

This article reports the dielectric, conductive, and ferroelectric properties of Rb-doped potassium titanyl phosphate (RKTP) crystals, of formula type RbxK1-xTiOPO4, where x=0.0065 or 0.013, both of which are shown to undergo ferroelectric switching at room temperature with coercive fields varying from 2.3 to 2.7 kV/mm. The measured spontaneous polarizations are 0.18(±0.01) and 0.19(±0.01) Cm-2 for RbxK1−xTiOPO4 with x=0.0065 and x=0.013, respectively. The dependence of the conductivity of Rb:KTP on electric-field amplitude at high fields leads to distorted ferroelectric hysteresis loops. As a result of thermal effects and the redistribution of vacancies, the switching times and switching current peaks vary throughout a series of switching processes at a frequency of 20 Hz. The measured switching times range from 2 to 6 ms and are inversely proportional to the peak current densities. The dielectric relaxation of Rb:KTP is found to be further from the Debye response than that of KTP. A correlation effect is seen to play an important role in reducing the ac conductivity of Rb:KTP at low frequencies relative to that of KTP. The results are discussed in the context of obtaining a KTP derivative, which is suitable for periodic patterning by electric field poling at room temperature.

Fast NbN superconducting switch controlled by optical radiation

The switching time and the optical control power of the NbN superconducting switch have been measured. The device is based on the ultrathin film 5-8 nm thick patterned as a structure of several narrow parallel strips (/spl sim/1 /spl mu/m wide) connected to wide current leads. The current-voltage characteristic of the switch at temperature 4.2 K demonstrated a hysteresis due to DC current self-heating. We studied the superconducting-to-resistive state transition induced by both optical and bias-current excitations. The optical pulse duration was /spl sim/20 ps and the rise time of the current step was determined to be less than 50 ps. The optical pulse was delivered to the switch by the semiconductor laser through an optical fiber. We found that the measured switching time is less than the duration of the optical excitation. The threshold optical power density does not exceed 3/spl middot/10/sup 3/ W/cm/sup 2/. The proposed device can be used in the fiber input of LTS rapid single flux quantum circuits.

A new method for characterizing ultrafast resonant-tunnelling diodes with electrooptic sampling

A new electrooptic sampling technique for characterizing ultrafast resonant-tunnelling diodes (RTD) is presented, in which the RTD is driven by the output of the photodiode irradiated by the same laser pulse that probes the output of the RTD. This method features a high time resolution, moderate slew rate and low heat load, which are the keys to characterizing RTD switching time. From the investigation of several factors, such as laser pulse width, interaction time between the probe pulse and electrical signal, and triggering jitter, the overall time resolution was found to be less than 1 ps. The measured switching times for In0.53Ga0.47As/AIAs RTDs were compared with the resistance-capacitance time constant for each device, and this confirmed that this driving method accurately measured RTD switching time at the order of 1 ps.

Based on high- T c superconducting films

A new microwave (37 GHz) filter-limiter containing two switching YBCO high-T/sub c/ superconductive film elements is presented. Its operating principle is based on the fast film switching from the superconducting (S) state to the normal conducting (N) state under microwave pulses. The measured switching time ( tau /sub S-N/), limited by the measuring electronics, was shorter than 2*10/sup -1/ ns, with theoretical value tau /sub S-N/ or=18 dB. >