Switching of one beam by another in a Kerr type nonlinear Mach–Zehnder interferometer Arpita Srivastava, S. Medhekar n Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835215, India article info Article history: Received 19 January 2010 Received in revised form 1 April 2010 Accepted 28 April 2010 Available online 13 May 2010 Keywords: Mach–Zehnder interferometer Kerr effect All-optical switching abstract This paper investigates switching of one beam by another in a Kerr type nonlinear Mach–Zehnder interferometer (NMZI) with two input ports and one output port. The present investigation has been carried out using the beam propagation method (BPM). The paper presents a detailed account on the procedures used to choose the parameters of the NMZI to make it behave like a NOT gate (inverter), an AND gate, an amplifier and a wavelength converter. The paper also gives details on the manipulation of the operating inputs of the NMZI to desired values. It is shown that the operating values of both the inputs of the NMZI can simultaneously be increased/decreased by decreasing/increasing the nonlinearity coefficient of nonlinear arm of the NMZI. Variation of NMZI length varies the operating value of only the first input, keeping the second unchanged, while variation of NMZI offset varies the operating value of only the second, keeping the first unchanged. The paper also gives a detailed account on amplification of the NMZI amplifier/wavelength converter. The present investigation is useful from the scientific as well as engineering point of view. & 2010 Elsevier Ltd. All rights reserved. 1. Introduction The Mach–Zehnder interferometer is one of the most important components in integrated optical circuits and has been extensively investigated for all-optical logic [1–9] applications due to its use in telecommunication systems. An all-optical AND gate can perform bit-level functions such as address recognition, packet–header modification, and data-integrity verification. The all-optical NOT/XOR gate is a key technology to implement primary systems for binary address and header recognition, binary addition and counting, decision and comparison, encoding and encryption, and pattern matching. Although numerous papers on a variety of applications exist on NMZI based devices, a systematic analysis on its switching behavior in different situation is missing in the literature. A thorough investigation on the switching behavior of a NMZI with one input beam has been carried out in Ref. [9]; however, as two incident beams must be mixed in order to realize logic functions in any manner, investigation on switching behavior of a NMZI with two inputs and one output is of importance. In this paper, using our own written code of beam propagation method (BPM), a detailed investigation on switching behavior of one beam by second in a Kerr type nonlinear Mach–Zehnder interferometer (NMZI) has been carried out. The paper presents a detailed account on the procedure used to make a NMZI behave like a NOT (inverter), an AND gate, a wavelength converter and an amplifier. The paper also gives intuitive understanding on manipulating/setting the operating inputs of the NMZI to desired values and on varying the amplification of the amplifier/ wavelength converter. In our opinion, this marvelous device (MZI) is still under- utilized in all-optical/opto-electronic systems due to lack of systematic analysis of its input–output characteristic. By providing a systematic and physically intuitive analysis, the present paper is intended to initiate further experimental research in implementation of MZI switches in all-optical/ opto-electronic systems. As the sole reason of switching in a MZI is the phase difference produced in the light waves propagating through two arms, we emphasize here that the utility of the analysis presented here is not limited to an all-optical version of the MZI switches. The present analysis is useful in all other types of MZI waveguide switches (electro-optic, magneto-optic, etc.). 2. Theory The considered NMZI is with one arm of a Kerr nonlinear material (NLA) and the other arm of a linear material (LA) as shown in Fig. 1. The MZI is provided with one suitable beam combiner (like Y-Junction) at the input side to have two input ports P 1 and P 2 . P o is the output port of the NMZI. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/optlastec Optics & Laser Technology 0030-3992/$ - see front matter & 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlastec.2010.04.021 n Corresponding author. E-mail address: sarangmedekar@rediffmail.com (S. Medhekar). Optics & Laser Technology 43 (2011) 29–35