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Semiconductor waveguide based high speed all optical wavelength converterSemiconductor waveguide based high speed all optical wavelength converter description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070171514, Semiconductor waveguide based high speed all optical wavelength converter. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] Embodiments of invention relate generally to optical devices and, more specifically but not exclusively relate to semiconductor-based optical wavelength conversion. [0003] 2. Background Information [0004] The need for fast and efficient optical-based technologies is increasing as Internet data traffic growth rate is overtaking voice traffic pushing the need for fiber optical communications. Transmission of multiple optical channels over the same fiber in the dense wavelength-division multiplexing (DWDM) system provides a simple way to use the unprecedented capacity (signal bandwidth) offered by fiber optics. Commonly used optical components in the system include wavelength division multiplexed (WDM) transmitters and receivers, optical filter such as diffraction gratings, thin-film filters, fiber Bragg gratings, arrayed-waveguide gratings, optical add/drop multiplexers and wavelength converters. [0005] A wavelength converter is a device that can be used to covert the wavelength of one optical beam to a different wavelength. Wavelength converters can be used to address the needs in future high speed, multi-wavelength optical networks. Known wavelength conversion techniques such as for example those that have been used in LiNbO.sub.3 crystal based wavelength converters have suffered from issues such as photorefractive damage and high cost. BRIEF DESCRIPTION OF THE DRAWINGS [0006] Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. [0007] FIG. 1 is a block diagram illustrating an optical system including an example of a high speed all optical wavelength converter in accordance with the teachings of the present invention. [0008] FIG. 2 is a diagram of example measured spectrum of FWM signals from an example high speed all optical wavelength converter illustrating a relationship between the pump (.lamda..sub.1), input (.lamda..sub.2), and converted (.lamda..sub.3) signals in accordance with the teachings of the present invention. [0009] FIG. 3 is a cross section view illustration of semiconductor-based optical waveguide including an example diode structure to reduce two-photon absorption generated carrier lifetimes in the semiconductor waveguide in accordance with the teachings of the present invention. [0010] FIG. 4 is a diagram illustrating conversion efficiency versus pump at -25 V bias in an example high speed all optical wavelength converter in accordance with the teachings of the present invention. [0011] FIG. 5A shows an eye diagram of an input optical signal that is directed into an example high speed all optical wavelength converter in accordance with the teachings of the present invention. [0012] FIG. 5B shows an eye diagram of a converted output optical signal generated from an example high speed all optical wavelength converter in accordance with the teachings of the present invention. DETAILED DESCRIPTION [0013] Methods and apparatuses for converting a wavelength of an optical beam are disclosed. In the following description numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one having ordinary skill in the art that the specific detail need not be employed to practice the present invention. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present invention. [0014] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments. In addition, it is appreciated that the figures provided herewith are for explanation purposes to persons ordinarily skilled in the art and that the drawings are not necessarily drawn to scale. [0015] FIG. 1 illustrates generally a system including an optical source coupled to transmit an optical beam to an optical receiver through an example of an optical device 107 in accordance with the teachings of the present invention. In particular, FIG. 1 shows system 101 including optical source 103 directing an input optical beam 105 into an optical waveguide 111 included in an optical device 107. As will be discussed, in one example, optical waveguide 111 is a four-wave mixing (FWM) optical waveguide as high speed all optical wavelength conversion is realized by utilizing a four-wave mixing effect in accordance with the teachings of the present invention. [0016] In the illustrated example, optical device 107 is a semiconductor-based high speed all optical wavelength converter in accordance with the teachings of the present invention. As shown in the illustrated example, input optical beam has a wavelength of .lamda.2 and information or data is encoded on input optical beam 105. As will be discussed, an output optical beam 127 having a different wavelength of .lamda.3 is generated in optical waveguide 111 and exits from an output of FWM optical waveguide. As shown, the data or information that was encoded on input optical beam 105 is also encoded on output optical beam 127. In one example, output optical beam 127 is directed from FWM optical waveguide through an optical filter 132 and is then transmitted through a standard optical fiber 129 to optical receiver 131. [0017] FIG. 1 shows that optical device 107 includes an optical waveguide 111 disposed in the semiconductor material 109 that is optically coupled to receive input optical beam 105. In one example, semiconductor material 109 includes silicon. Optical waveguide 111 is etched in the semiconductor material 109, which is also integrated with a diode structure 113. In one example, the diode structure 113 includes a p-i-n diode that is biased with voltage 125 to remove free carriers from an optical path through optical waveguide 111 in accordance with the teachings of the present invention. The free carriers are present along the optical path of optical waveguide 111 due to two photon absorption occurring within optical waveguide 111. [0018] The example illustrated in FIG. 1 shows that optical waveguide 111 is also optically coupled to receive a pump optical beam 117 from an optical pump115 through an optical waveguide 119 disposed in the semiconductor material 109. In the illustrated example, the pump optical beam 117 has a pump wavelength .lamda.1, which is a different wavelength than the wavelength .lamda.2 of the input optical beam 105 or the wavelength .lamda.3 of output optical beam 127. In one example, optical pump 115 is a continuous wave (CW) laser such that optical pump beam 117 is a CW laser beam having a wavelength .lamda.1. [0019] In one example, a four-wave mixing effect is employed in the semiconductor material 109 of optical waveguide 111 to convert an optical signal included in input optical beam 105 at wavelength .lamda.2 into a different wavelength .lamda.3. In the illustrated example, the waveguide structure of optical waveguide 111 is has appropriate dimension and design such that optical pump beam 117 and input optical beam 105 are collinearly coupled into optical waveguide 111. Due to a nonlinear interaction between pump optical beam and the input optical beam, a degenerated FWM effect occurs within the semiconductor material 109 of optical waveguide 111 resulting in a new wavelength .lamda.3 being generated for output optical beam 127 in accordance with the teachings of the present invention. [0020] In one example, the wavelengths .lamda.1, .lamda.2 and .lamda.3 of the optical pump beam 117, the input optical beam 105 and output optical beam 127, respectively, satisfy the following relationship:1/.lamda.3=2/.lamda.1-1/.lamda.2 (1) In other words, a reciprocal of the wavelength of the output optical beam 127 is equal to twice the reciprocal of the wavelength of the pump optical beam 117 minus the reciprocal of the wavelength of the input optical beam 105. [0021] Generally speaking FWM occurs when light of three different wavelengths is launched into a medium, giving rise to a new wave, the wavelength of which does not coincide with any of the others. FWM is a nonlinear optical effect and the third order nonlinear susceptibility is responsible for four-wave mixing processes. When the wavelengths of two of the input waves are identical, such as the pump beam in the example described herein, the term degenerated four-wave mixing is also used. 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