Abstract: Enhanced reflectivity High-Contrast Gratings are described which operate in different medium. An HCG is described with a deep/buried metallization layer separated at a distance of least three to four grating thicknesses from the grating. Reflective bandwidth of the HCG is substantially increased, such as by a factor or five, by inclusion of the deep/buried metallization layer. An HCG is described which provides high reflectivity, even when embedded into materials of a moderate to high index of refraction, such as semiconductor material. Vertical cavity surface emitting laser embodiments are described which utilize these reflectivity enhancements, and preferably utilize HCG reflectors for top and/or bottom mirrors.

Abstract: A saturable absorber (SA) based on a high-contrast grating (HCG) having a buried layer of quantum structures for absorption, and which is particularly well suited for use in a mode-locked application. The HCG-SA provides three times the bandwidth compared with traditional DBR structures, while exhibiting a lower saturation fluence due to the field enhancement inside the grating. Varying grating bar width over one or two axis provides lensing effects on the optical output, while chirping of the period and duty cycle changes optical phase relationships. Novel VCSEL embodiments with external or internal cavities are described using the HCG-SA.

Abstract: Multiple-wavelength VCSEL array apparatus and method having a high contrast grating (HCG) mirror which can be implemented on a single substrate in which only the dimensions of the HCG (e.g., duty cycle or the period) need be changed to alter the wavelength of a given VCSEL in response to changing the reflectivity phase of the HCG mirror. The HCG can be defined by any desired lithographic process. By using a broadband HCG mirror a large wavelength span over 100 nm is provided, such as covering the entire C-band. The HCG multi-wavelength VCSEL array enables single-transverse mode emission and polarization control and scalability with respect to wavelength.

Abstract: Adjustable chirp is achieved in injection-locked, 10-Gb/s directly modulated, multimode 1.55-?m VCSELs for the first time, leading to 90× increase in standard single-mode fiber transmission distance to 90 km.

Abstract: A Vertical Cavity Surface Emitting Laser (VCSEL) and its fabrication are taught which incorporate a high contrast grating (HCG) to replace the top mirror of the device and which can operate at long-wavelengths, such as beyond 0.85 ?m. The HCG beneficially provides a high degree of polarization differentiation and provides optical containment in response to lensing by the HCG. The device incorporates a quantum well active layer, a tunnel junction, and control of aperture width using ion implantation. A tunable VCSEL is taught which controls output wavelength in response to controlling a micro-mechanical actuator coupled to a HCG top mirror which can be moved to, or from, the body of the VCSEL. A fabrication process for the VCSEL includes patterning the HCG using a wet etching process, and highly anisotropic wet etching while precisely controlling temperature and PH.

Abstract: Optical waveguides using segmented periodically-spaced high contrast gratings bounding a hollow core propagation region on at least two sides. Incident light is received in a hollow waveguide (HW) region (core) between opposing HCG faces which provide lateral confinement in response to glancing reflections of the incident light beam from high refractive index segments of the HCG as it traverses the core. Embodiments are described for planar waveguides (1D) having a planar core between two planar HCGs, as well as 2D waveguides, such as having rectangular segments of the HCG through which light is propagated. Additionally, other configurations of HCG-HW, including those having arbitrary incidence and azimuth, angled HCG segments, propagation in a direction which is transverse, or alternatively parallel, to the segments of the HCG.

Abstract: The present disclosure provides a catalyst-free growth mode of defect-free Gallium Arsenide (GaAs)-based nanoneedles on silicon (Si) substrates with a complementary metal-oxide-semiconductor (CMOS)-compatible growth temperature of around 400° C. Each nanoneedle has a sharp 2 to 5 nanometer (nm) tip, a 600 nm wide base and a 4 micrometer (?m) length. Thus, the disclosed nanoneedles are substantially hexagonal needle-like crystal structures that assume a 6° to 9° tapered shape. The 600 nm wide base allows the typical micro-fabrication processes, such as optical lithography, to be applied. Therefore, nanoneedles are an ideal platform for the integration of optoelectronic devices on Si substrates. A nanoneedle avalanche photodiode (APD) grown on silicon is presented in this disclosure as a device application example. The APD attains a high current gain of 265 with only 8V bias.

Abstract: Apparatus and method for increasing optical transmission bandwidth in response to chaining, in cascade, one or more slave lasers onto a master laser. Each laser is configured for optical injection locking (OIL) and each slave laser is locked onto the master laser. The first and each subsequent slave laser are detuned to tailor frequency characteristics of apparatus output. The transmitter can be scaled up by cascading additional injection-locked lasers together. The invention supports multiple compatible modulation formats, such as amplitude modulation (AM), phase modulation (PM), and frequency modulation (FM), for tailoring the output to the application of interest, while any type of laser can be used for the master and slave lasers.

Abstract: Low cost implementation of broadband upstream transmission for local and access network applications is made possible through the use of modulated downstream signals in a wavelength division multiplexed (WDM) passive optical network (PON) to injection-lock vertical-cavity surface-emitting lasers (VCSELs) for operation as stable, uncooled, and directly-modulated upstream transmitters. By way of example and not limitation, an optical network unit comprises: downstream input, photoreceiver, tunable laser, upstream output, and means for directionally coupling the downstream input into the tunable laser for modulating the output wavelength which is coupled to the upstream output.

Abstract: A vertical cavity surface emitting laser (VCSEL) is described using a sub-wavelength grating (SWG) structure that has a very broad reflection spectrum and very high reflectivity. The grating comprises segments of high and low refractive index materials with an index differential between the high and low index materials. By way of example, a SWG reflective structure is disposed over a low index cavity region and above another reflective layer (either SWG or DBR). In one embodiment, the SWG structure is movable, such as according to MEMS techniques, in relation to the opposing reflector to provide wavelength selective tuning. The SWG-VCSEL design is scalable to form the optical cavities for a range of SWG-VCSELs at different wavelengths, and wavelength ranges.

Abstract: A sub-wavelength grating structure that has a very broad reflection spectrum and very high reflectivity comprising segments made of high refractive index material disposed on a layer of low refractive index material and a low refractive index material disposed above and between the segments. The index differential between the high and low index materials determines the bandwidth and modulation depth. The larger difference in refractive indices gives rise to wider reflection bands. The reflection is sensitive to parameters such as the grating period, the grating thickness, the duty cycle of the grating, the refractive index and the thickness of the low index layer underneath the grating. The design is scalable for different wavelengths, and facilitates monolithic integration of optoelectronic devices at a wide range of wavelengths from visible to far infrared.

Abstract: A variable semiconductor all-optical buffer and method of fabrication is provided where buffering is achieved by slowing down the optical signal using a control light source to vary the dispersion characteristic of the medium based on electromagnetically induced transparency (EIT). Photonic bandgap engineering in conjunction with strained quantum wells (QWs) and quantum dots (QDs) achieves room temperature operation of EIT. Photonic crystals are used to sharpen the spectral linewidths in a quantum well structure due to its density of states and in a quantum-dot structure caused by the inhomogeneity of the dot size, typically observed in state-of-the-art QD materials. The configuration facilitates monolithic integration of an optical buffer with an amplifier and control laser to provide advantages over other material systems as candidates for optical buffers.