All-optical NOR gate based on stimulated Raman scattering in silicon waveguide Tanay Chattopadhyay1 and Tamal Sarkar2 1

Mechanical Operation (Stage-II), Kolaghat Thermal Power Station, WBPDCL,

Mecheda, Purbamedinipur, KTPP sub post office, 721137, West Bengal, India. E-mail: [email protected] 2

USIC, University of North Bengal, Siliguri, West Bengal, India, E-mail: [email protected]

Abstract: The stimulated Raman scattering (SRS) in silicon-on-insulator (SOI) waveguide is used to design all-optical NOR gate in this present proposal.

Keywords:

stimulated

Raman

scattering,

all-optical

logic,

silicon-on-insulator

waveguide.

1. Introduction: Silicon on insulator technology (SOI) refers to the use of a layered silicon-insulatorsilicon substrate in place of conventional silicon substrates in semiconductor manufacturing, especially microelectronics, to reduce parasitic device capacitance and thereby improving performance. SOI-based devices differ from conventional silicon-built devices in that the silicon junction is above an electrical insulator, typically silicon dioxide or (less commonly) sapphire. (These types of devices are called silicon on sapphire, or SOS). The choice of insulator depends largely on intended application, with sapphire being used for radiation-sensitive applications and silicon dioxide preferred for improved performance and diminished short channel effects in microelectronics devices. The insulating layer and topmost silicon layer also vary widely with application. The first 1

industrial implementation of SOI was announced by IBM in August 1998. SOI wafers are widely used in silicon photonics. The crystalline silicon layer on insulator can be used to fabricate optical waveguides and other passive optical devices for integrated optics. The crystalline silicon layer in sandwiched between the buried insulator (Silicon oxide, Sapphire etc) and top cladding of air (or Silicon oxide or any other low refractive index material). This enables propagation of electromagnetic waves in the waveguides on the basis of total internal reflection. Raman spectroscopy has lot of applications. Among them stimulated Raman scattering (SRS) may plays a significant role in optical computing in near future. Recently SOI is done to archives optical amplification and it is possible to reach up to 10 dB of signal gain in optically pumped silicon waveguides with length < 2 cm [1]. Free carrier abortion (FCA) mitigates the performance of this amplification due to two photon absorption (TPA), if we use high intense pump beam with the probe beam [2]. Using this property Khorasaninejad et al [2] proposed all-optical AND gate in their proposal. In this present proposal, we make a design of all-optical NOR gate using SRS and FCA. 2. All-optical NOR gate: The schematic diagram of all-optical NOR gate is shown in the Fig-1. C1 is a constant Gaussian pulsed picoseconds light source to generate Raman amplification. Two Gaussian pulsed beams A, B are combined with a beam combiner and put it into the SOI waveguide to change the density of the free carrier (FC). The intensity of this light is 10 times higher than C1. A ‘CW’ probe beam (C2) at the stokes wavelength for pump C1 is also applied. When A, B are both absent (A = B = 0) then, Raman coupling happens between C1 and C2. Hence no FC generates and we get C2 at the output after wavelength

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filter, which rejects the original and anti-stokes beam. In other cases, FCA takes place which decreases the Raman amplification.

Fig: All-optical NOR gate and its truth table.

3. Conclusion: In this section all-optical NOR gate with the help of SRC is proposed and described. Optimal waveguide sizes have been selected for single-mode and polarization insensitivity, and threshold conditions for higher-order Stokes pulses have been found in order to increase the SLS ratio of NOR gate.

Acknowledgments: Author gratefully acknowledges M. Khorasaninejad regarding the reference [2].

References [1] R.Claps, D.Dimitropoulos and B.Jalali, “Stimulated Raman scattering in silicon waveguides”, Electronics letters, 38(22), (2002), 1352-1353. [2] M. Khorasaninejad and S.S Saini, "All Optical Logic Operations in Silicon on Insulator Waveguides Based on Nonlinear Effects of Free Carriers," the 22nd Annual Lasers and Electro Optics Society Meeting, paper ThJ 2, (2009).

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