Ž . Sensors and Actuators 86 2000 127–134 www.elsevier.nlrlocatersna Micro-opto-mechanical grating switches A.Q. Liu a, ) , B. Zhao b , F. Chollet a , Q. Zou a , A. Asundi b , H. Fujita c a MEMS Technology, Institute of Materials Research & Engineering, 3 Science Link, National UniÕersity of Singapore, Singapore 117206, Singapore b School of Mechanical and Production Engineering, Nanyang Technological UniÕersity, Singapore 639798, Singapore c Institute of Industrial Science, The UniÕersity of Tokyo, 7-22-11 Roppongi, Minato-ku, Tokyo 106, Japan Received 8 January 1999; received in revised form 18 January 2000; accepted 25 January 2000 Abstract This paper reports the design, fabrication, and testing of a Micro-opto-mechanical grating switch driven by electrostatic actuator for fiber-optic communication applications. It consists of two bounded silicon wafers. One input fiber with a hemispherical lens at its end and three photodetectors are mounted on the upper wafer. A movable platform with two gratings and one mirror are fabricated on the lower wafer. When the movable platform is at a certain position, the input beam can be split into three beams by the gratings. The reflectivity of the mirror is about 85% while the efficiency in the three different order is 29%, 26%, and 26%. The switching speed is about 500 ms. Details of the grating switching design, theoretical analysis, fabrication and experimental results are presented in this paper. q 2000 Elsevier Science B.V. All rights reserved. Ž . Keywords: Micro-opto-electro-mechanical systems MOEMs ; Micromirror; Micrograting; Optics switch; Multiplexer; Wavelength division multiplexing Ž . Ž . WDM ; Passive optical network PON 1. Introduction One attractive feature of optics especially for communi- cation and information processing is its ability to transmit huge amounts of digital stream in parallel. Fiber optics switches are used to reconfigure the high-speed digital fiber-optics network. For example, a passive optical net- Ž . work PON or hybrid electronicroptical network needs various types of optics switches. The rapid growth of fiber-based local area networks has created a large demand for low-loss, low-cost, reliable, and mass-producible fiber optics switches. The significant advantage of using Microelectromechan- Ž . ical Systems MEMS for optics switches are its small w x size, low cost, and high reliability and stability 1,2 . Micro-opto-mechanical gratings are very attractive for im- Ž . plementing wavelength division multiplexing WDM switches, as reflection grating is used to disperse incident light into angular directions determined by the incident light’s wavelength and the construction properties of the ) Corresponding author. Tel.: q 65-874-8161; fax: q 65-872-0785. Ž . E-mail address: aq-liu@imre.org.sg A.Q. Liu . Ž . wx grating. Variable blaze gratings VBGs 3 have adjustable Ž . blaze angles with a fast time response less than 10 ms are suitable to be designed as 1 = N multiplexer using MEMS technology. It provides the important capability of high density digital transmission communication with a band width as high as 2.5 Gbps. Diffraction grating without any movable mechanical part has been used to produce a wx diffraction spot pattern for optical interconnection 4 . The type of interconnection is mainly used for computing network. Two other type of diffraction grating switches of used in broadband optical network have been reported w x 5,6 . This paper proposes a micro-opto-mechanical gratingr mirror switch that is a programmable addrdrop multi- plexer to be used as a spatial terminal switch for single- wavelength optical local network or passive optical telecommunication network. Firstly, the design of a grat- ingrmirror switch with one-input and three-outputs used as a miniaturized fiber-optics network terminal switch is described. The design includes grating structure, mechani- cal actuators and electronic signal processing. The main effort is concentrated on improving the diffraction effi- ciency of the interested diffraction order. Then, the simula- tion results of the grating diffraction efficiency is shown. 0924-4247r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0924-4247 00 00404-0