摘要:
A photodetector for use with relatively thin (i.e., sub-micron) silicon optical waveguides formed in a silicon-on-insulator (SOI) structure comprises a layer of poly-germanium disposed to couple at least a portion of the optical signal propagating along the silicon optical waveguide. Tight confinement of the optical signal within the waveguide structure allows for efficient evanescent coupling into the poly-germanium detector. The silicon optical waveguide may comprise any desired geometry, with the poly-germanium detector formed to either cover a portion of the waveguide, or be butt-coupled to an end portion of the waveguide. When covering a portion of the waveguide, poly-germanium detector may comprise a “wrap-around” geometry to cover the side and top surfaces of the optical waveguide, with electrical contacts formed at opposing ends of the detector.
摘要:
A silicon-based electro-optic modulator is based on forming a gate region of a first conductivity to partially overly a body region of a second conductivity type, with a relatively thin dielectric layer interposed between the contiguous portions of the gate and body regions. The modulator may be formed on an SOI platform, with the body region formed in the relatively thin silicon surface layer of the SOI structure and the gate region formed of a relatively thin silicon layer overlying the SOI structure. The doping in the gate and body regions is controlled to form lightly doped regions above and below the dielectric, thus defining the active region of the device. Advantageously, the optical electric field essentially coincides with the free carrier concentration area in this active device region. The application of a modulation signal thus causes the simultaneous accumulation, depletion or inversion of free carriers on both sides of the dielectric at the same time, resulting in high speed operation.
摘要:
A set of planar, two-dimensional optical devices is able to be created in a sub-micron surface layer of an SOI structure, or within a sub-micron thick combination of an SOI surface layer and an overlying polysilicon layer. Conventional masking/etching techniques may be used to form a variety of passive and optical devices in this SOI platform. Various regions of the devices may be doped to form the active device structures. Additionally, the polysilicon layer may be separately patterned to provide a region of effective mode index change for a propagating optical signal.
摘要:
A set of planar, two-dimensional optical devices is able to be created in a sub-micron surface layer of an SOI structure, or within a sub-micron thick combination of an SOI surface layer and an overlying polysilicon layer. Conventional masking/etching techniques may be used to form a variety of passive and optical devices in this SOI platform. Various regions of the devices may be doped to form the active device structures. Additionally, the polysilicon layer may be separately patterned to provide a region of effective mode index change for a propagating optical signal.
摘要:
A set of planar, two-dimensional optical devices is able to be created in a sub-micron surface layer of an SOI structure, or within a sub-micron thick combination of an SOI surface layer and an overlying polysilicon layer. Conventional masking/etching techniques may be used to form a variety of passive and optical devices in this SOI platform. Various regions of the devices may be doped to form the active device structures. Additionally, the polysilicon layer may be separately patterned to provide a region of effective mode index change for a propagating optical signal.
摘要:
A silicon-based IR photodetector is formed within a silicon-on-insulator (SOI) structure by placing a metallic strip (preferably, a silicide) over a portion of an optical waveguide formed within a planar silicon surface layer (i.e., “planar SOI layer”) of the SOI structure, the planar SOI layer comprising a thickness of less than one micron. Room temperature operation of the photodetector is accomplished as a result of the relatively low dark current associated with the SOI-based structure and the ability to use a relatively small surface area silicide strip to collect the photocurrent. The planar SOI layer may be doped, and the geometry of the silicide strip may be modified, as desired, to achieve improved results over prior art silicon-based photodetectors.
摘要:
A planar optical isolator is formed within the silicon surface layer of an SOI structure. A forward-directed signal is applied to an input waveguiding section of the isolator and thereafter propagates through a non-reciprocal waveguide coupling region into an output waveguide section. A rearward-directed signal enters via the output waveguide section and is thereafter coupled into the non-reciprocal waveguide structure, where the geometry of the structure functions to couple only a small amount of the reflected signal into the input waveguide section. In one embodiment, the non-reciprocal structure comprises an N-way directional coupler (with one output waveguide, one input waveguide and N−1 isolating waveguides). In another embodiment, the non-reciprocal structure comprises a waveguide expansion region including a tapered, mode-matching portion coupled to the output waveguide and an enlarged, non-mode matching portion coupled to the input waveguide such that a majority of a reflected signal will be mismatched with respect to the input waveguide section. By cascading a number of such planar SOI-based structures, increased isolation can be achieved—advantageously within a monolithic arrangement.
摘要:
A wafer-level testing arrangement for opto-electronic devices formed in a silicon-on-insulator (SOI) wafer structure utilizes a single opto-electronic testing element to perform both optical and electrical testing. Beam steering optics may be formed on the testing element and used to facilitate the coupling between optical probe signals and optical coupling elements (e.g., prism couplers, gratings) formed on the top surface of the SOI structure. The optical test signals are thereafter directed into optical waveguides formed in the top layer of the SOI structure. The opto-electronic testing element also comprises a plurality of electrical test pins that are positioned to contact a plurality of bondpad test sites on the opto-electronic device and perform electrical testing operations. The optical test signal results may be converted into electrical representations within the SOI structure and thus returned to the testing element as electrical signals.
摘要:
An arrangement for achieving and maintaining high efficiency coupling of light between a multi-wavelength optical signal and a relatively thin (e.g., sub-micron) silicon optical waveguide uses a prism coupler in association with an evanescent coupling layer. A grating structure having a period less than the wavelengths of transmission is formed in the coupling region (either formed in the silicon waveguide, evanescent coupling layer, prism coupler, or any combination thereof) so as to increase the effective refractive index “seen” by the multi-wavelength optical signal in the area where the beam exiting/entering the prism coupler intercepts the waveguide surface (referred to as the “prism coupling surface”). The period and/or duty cycle of the grating can be controlled to modify the effective refractive index profile in the direction away from the coupling region so as to reduce the effective refractive index from the relatively high value useful in multi-wavelength coupling to the lower value associated with maintaining confinement of the optical signals within the surface waveguide structure, thus reducing reflections along the transition region.
摘要:
A conventional CMOS fabrication technique is used to integrate the formation of passive optical devices and active electro-optic devices with standard CMOS electrical devices on a common SOI structure. The electrical devices and optical devices share the same surface SOI layer (a relatively thin, single crystal silicon layer), with various required semiconductor layers then formed over the SOI layer. In some instances, a set of process steps may be used to simultaneously form regions in both electrical and optical devices. Advantageously, the same metallization process is used to provide electrical connections to the electrical devices and the active electro-optic devices.