This paper reports a novel method for measuring the effective refractive index (RI) of single living cell with a small integrated chip. This microchip is able to determine the RI of living cell in real time without extra requirements of fluorescence labeling and chemical treatments, offering low cost and high accuracy meanwhile. It might provide an efficient approach for diseases or cancer diagnosis. The measurement system integrates laser diode, microlenses, and microfluidic channels onto a monolithic chip. In the experiments, two standard polystyrene beads with nominal RIs are employed to calibrate the system and five types of cancerous cells are subsequently measured. The results indicate that the RI of the tested cells ranges from 1.392 to 1.401, which is larger than typical value 1.35-1.37 for normal cells.
In this paper, the application of fiber interferometry in the nano-scale displacement measurement of microelectromechanical system (MEMS) device is being presented. Fiber optic interferometry combines the benefits of the optical fiber such as lightweight, small size and wide bandwidth with the high resolution, high sensitivity capability of the interferometry. It also provides easier setup and offers lower energy loss than the conventional free-spaced interferometry. The fiber optic interferometric system comprises a laser source and a 2 X 2 fiber coupler. The reference arm and the sensing arm of the interferometer are formed within a single output of the coupler. The resultant interference intensity is measured at one of the fiber coupler input. The fiber optic interferometry could be used for the MEMS with moving structure. A case study is being carried out to investigate the displacement of the micromirror in the MEMS Fabry-Perot Filter. The mirror is being driven by the comb drive actuator under the effect of applied voltage. It selectively reflects certain wavelengths while allows others to pass through determined by the air cavity length. The displacement under different applied voltages will be measured using the fiber optic interferometry. The experiment and the result will be demonstrated.
Tunable lasers have wide applications in DWDM systems to save inventory cost and to improve the optical network functionalities. The Microelectromechanical Systems (MEMS) technology has shown strong promise to miniaturize the conventional mechanical tunable lasers with adding merits of high compactness, high speed, batch production and so on. In this paper, external cavity tunable diode lasers using MEMS movable mirrors and rotary gratings as the external reflectors are presented. One tunable laser of 2 mm × 1.5 mm is formed by integration of a surface-micromachined 3D mirror with a diode laser and an optical fiber. In addition, deep-etched structures such rotary gratings, circular mirror, microlens, and grooves for diode laser and fiber are illustrated to form widely tunable lasers.
This paper reports the design, modeling, fabrication and testing of a novel variable optical attenuator for multi-channel power equalizers to be used in dense wavelength division multiplexed (DWDM) systems. The attenuator is fabricated by silicon surface micromachining technology and is then manually assembled and integrated with two single mode optical fibers that act as optical input and output. A 40 × 40 μm2 mirror coated with gold is driven by a proprietary drawbridge structure to cut partially into the light path between two fibers, enabling the attenuation. The attenuator has a dimension of 0.6 × 1 μm2 excluding the fibers. It has 1.5 dB insertion loss and 45 dB attenuation range, and requires only 8 V driving voltage, showing that it is promising for DWDM applications. Optical and mechanical models of the attenuator have also been established. Although the models are developed with the initial intention of modeling the MEMS attenuator, they are also available to the other types of devices in which the preconditions of the models are satisfied.
Tunable lasers have wide applications in DWDM systems to save inventory cost and to improve the optical network functionalities. The Microelectromechanical Systems (MEMS) technology has shown strong promise to miniaturize the conventional mechanical tunable lasers with adding merits of high compactness, high speed, batch production and so on. In this paper, external cavity tunable diode lasers using MEMS movable mirrors and rotary gratings as the external reflectors are presented. One tunable laser of 2 mm × 1.5 mm is formed by integration of a surface-micromachined 3D mirror with a diode laser and an optical fiber. A wavelength tuning range of 16 nm is obtained. In addition, deep -etched structures such rotary gratings, circular mirror, microlens, and grooves for diode laser and fiber are illustrated to form widely tunable lasers.
This paper reports the design, modeling, fabrication and testing of a novel variable optical attenuator for multi-channel power equalizers to be used in dense wavelength division multiplexed (DWDM) systems. The attenuator is fabricated by silicon surface micromachining technology and is then manually assembled and integrated with two single mode optical fibers that act as optical input and output. A 40 × 40 ?m2 mirror coated with gold is driven by a proprietary drawbridge structure to cut partially into the light path between two fibers, enabling the attenuation. The attenuator has a dimension of 0.6 × 1 mm2 excluding the fibers. It has 1.5 dB insertion loss and 45 dB attenuation range, and requires only 8 V driving voltage, showing that it is promising for DWDM applications. Optical and mechanical models of the attenuator have also been established. Although the models are developed with the initial intention of modeling the MEMS attenuator, they are also available to the other types of devices in which the preconditions of the models are satisfied.
Variable optical attenuators (VOAs) have wide applications in DWDM optical communication systems, for example, equalizing the power levers of different wavelength channels, flattening the gain of optical amplifiers, etc. A MEMS variable optical attenuator with fibers connectorized has been developed using proprietary drawbridge structure, which has achieved 1.5 dB insertion loss, 45 dB dynamic range and 37 ms response time, and requires only 8 V driving voltage. Finite element model and analytical model have also been studied and compared with the experimental data, showing that the two models predict the mechanical characteristics of MEMS VOA with reasonable accuracy.
This paper reports the design, fabrication, and testing of drawbridge micromirrors that is used to form a monolithic 4 X 4 optical crossconnect (OXC) having dimensions about 4 mm X 4 mm. The OXC is composed of 16 individual drawbridge micromirrors that are fabricated by the surface micromachining technology and then manually assembled. In each drawbridge micromirror the mirror is driven by electrostatic force to cut off the laser beam or let it pass through, enabling the switching. The measured switching times range from 94 microsecond(s) to 181.1 microsecond(s) for the switches with different bending bean sizes. The configuration of this OXC is scalable and capable to build up a large array of OXC system.
KEYWORDS: Micromirrors, Signal attenuation, Variable optical attenuators, Single mode fibers, Deep reactive ion etching, Optical switching, Optical interconnects, Quantum wells, Wavelength division multiplexing, Control systems
Variable optical attenuator (VOA) is undergoing to be a mainstream component of wavelength division multiplex (WDM) networks to monitor and control the optical power of wavelength channels. In this paper, a free-space VOA fabricated by micro electromechanical systems (MEMS) technology to operate in the 1.55 micrometers wavelength region is described. It employs a micromirror driven by an electrostatic comb drive to cut partially into the light beam between two single mode fibers (SMFs), enabling the attenuation. The micromirror has a size of 30 micrometers X 30 micrometers and is coated with aluminum to increase the reflectance. The moving fingers of comb drive and the micromirror are supported by folded suspension beams over the substrate. By applying different voltage to the comb drive, the micromirror translates to different position to achieve an attenuation ranging from 0.4dB to 50dB, and even higher. The nonlinear relationship between the position of the micromirror and attenuation is analyzed. The distributions of the light beams at the micromirror and the output fiber end are investigated respectively. And the influence of the separations between the micromirror, the input and output fiber ends is also discussed to obtain different attenuation resolutions. At low attenuation stages, fine tuning of attenuation is obtainable. The largest attenuation is driven by 21voltage. Deep reactive ion etching (DRIE) process is employed to fabricate the VOA and the micro loading effect is remedied by mask design.
This paper presents finite element (FE) simulation and theoretical analysis of novel MEMS fiber-optical switches actuated by electrostatic attraction. FE simulation for the switches under static and dynamic loading are first carried out to reveal the mechanical characteristics of the minimum or critical switching voltages, the natural frequencies, mode shapes and response under different levels of electrostatic attraction load. To validate the FE simulation results, a theoretical (or analytical) model is then developed for one specific switch, i.e., Plate_40_104. Good agreement is found between the FE simulation and the analytical results. From both FE simulation and theoretical analysis, the critical switching voltage for Plate_40_104 is derived to be 238 V for the switching angel of 12 degree(s). The critical switching on and off times are 431 microsecond(s) and 67 microsecond(s) , respectively. The present study not only develops good FE and analytical models, but also demonstrates step by step a method to simplify a real optical switch structure with reference to the FE simulation results for analytical purpose. With the FE and analytical models, it is easy to obtain any information about the mechanical behaviors of the optical switches, which are helpful in yielding optimized design.
An integrated MEMS tunable laser of approximately 2 mm X 1.5 mm size is demonstrated in this paper. The tunable laser is formed by the integration of a surface-micromachined 3D micromirror with a Fabry-Perot laser diode and an optical fiber. The micromirror can be driven to translate by a comb drive to change the external cavity length of laser diode, enabling the wavelength tuning. A tunable range of 16 nm is obtained, which covers 20 channels of WDM systems spaced by 100GHz. The three-mirror Fabry-Perot cavity model is modified to explain the continuous wavelength change as well as the mode hopping. An array of the tunable laser is potential to supply light sources for multiple channels of WDM systems.
This paper reports the design, fabrication and test of a monolithically-integrated 4 X 4 free-space optical crossconnect using microfabricated polysilicon 3D-mirror to enable light-path switching for optical communication applications. The switch consists of 16 pairs of three- dimensional movable mirrors and draw-bride plate actuators, and four input and output fiber-optic guiding rails. The draw- bridge plates actuated by the electrostatic force drive the 3D-mirrors up and down to cut off the light beam or to let the light beam pass through. The optical crossconnect is fabricated using three-layer-polysilicon surface micromachining technology. The size of the whole structures is 5 mm X 5 mm . The maximum driving voltage is about 45 V, and its resonant frequency is about 5 KHz (200 micrometer switch time). The optical insertion loss of about 1.5 dB and the crosstalk of less than -60 dB have been obtained while using GRIN-lens to collimate the input optical signals.
This paper reports the design, fabrication and test of a monolithically-integrated 4 X 4 free-space optical crossconnect using microfabricated polysilicon 3D-mirror to enable light-path switching for optical communication applications. The switch consists of 16 pairs of 3D movable mirrors and draw-bridge plate actuators, and four input and output fiber-optic guiding rails. The draw-bridge plates actuated by the electrostatic force drive the 3D-mirrors up and down to cut off the light beam or to let the light beam pass through. The optical crossconnect is fabricated using three-layer-polysilicon surface micromachining technology. The size of the whole structures is 5 mm X 5 mm. The maximum driving voltage is about 45 V, and its resonant frequency is about 5 KHz (200 micrometers switch time). The optical insertion loss of about 1.5 dB and the crosstalk of less than -60 dB have been obtained while using GRIN- lens to collimate the input optical signals.
Two monolithically-integrated tunable lasers have been analyzed, designed and fabricated. The potential applications for WDM have also been studied. The tunable lasers use 3D micromirrors integrated with single-mode Fabry-Perot laser diodes and anti-reflection coated optical fibers. The difference between the two tunable lasers is that one uses the movable 3D micromirror driven by comb- drive to change the external cavity length, and the other uses the rotatable 3D micromirror driven by thermal-actuator to change the external feedback strength. For the frequency tuner that uses movable 3D micromirror, a wavelength tunability of 16 nm is obtained using 3V driving voltage. As for the frequency tuner that uses rotatable 3D micromirror, a wavelength tunability of 7 nm is obtained while using 10 mA driving current.
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