University of California

Connie J Chang-Hasnain

Forrest G Sedgwick

Michael Chung-Yi Huang

Carlos Fernando Rondina Mateus

Wai Son Ko

Vadim Karagodsky

Christopher Chase

Ye Zhou

Chih-Wei Chuang

Li Yan Zhu

Pei-Cheng Ku

Sui F Lim

Kam-Yin Lau

Fang Liu

Pengfei Qiao

Tianbo Sun

Kar Wei Ng

Jeffrey Michael Waite

Fanglu Lu

Steven M Chase

Janice A Hudgings

Forrest Grant Sedgwick, Iv

Roger Chen

Weijian Yang

Kevin Taylor Cook

Thai-Truong Du Tran

Vertical-cavity surface-emitting laser (VCSEL) structures are described which enable their use as widely wavelength-swept coherent light sources and multiple-wavelength VCSEL arrays. Three general configurations are described: (a) a semiconductor-cavity-dominant (SCD) with high reflection at the semiconductor-air interface, (b) an extended-cavity (EC) design in which reflections at the semiconductor-air interface is reduced to insignificance compared to the SCD design with a refractive index-matched layer (i.e., AR layer) so the entire structure resonates as one cavity, and (c) an air-cavity-dominant (ACD) design which facilitates a larger field confinement in the air gap, and the increased field confinement causes the air gap to be the dominant cavity.

Air-cavity dominant vertical cavity surface emitting lasers

An optical sensing platform with an array of sensors, a laser or broadband light source and an optical detector that utilizes surface plasmon resonance based transduction and optical detection is provided. The sensor structure of the platform has a low index support layer, a high contrast grating, a low index spacer and a thin metal film with a target recognition element. The surface plasmon resonance based sensor uses surface plasmon waves to detect changes on the surface of the sensor when a target interacts with the target recognition element. The binding of the target with a recognition element receptor will induce changes in the refractive index of the metal layer, which changes the resonance wavelength of the plasmon wave on the sensor surface, which is used to measure or observe the reaction.

Optical sensor using high contrast gratings coupled with surface plasmon polariton

A color changing or beam steering photonic device, which combines a high contrast metastructure (HCM) having a plurality of high index grating structures, into a low index membrane. In response to physical (or electrical) deformation of the membrane the low index gaps between adjacent grating bars changes which results in changing reflectance and transmission angles for steering a single wavelength of light and for causing a color change in said photonic device when subject to multiple light wavelengths. Deformation can result from direct physical stimulus, conversion from electrical or thermal to physical, and so forth. Refractive index change can also be initiated by carrier injection through electrodes. The apparatus is exemplified for use in color displays, beam steering, labeling micro entities, mechanical deformation sensing, camouflage, anti-counterfeiting, and other fields.

Actively controllable color using high contrast metastructures

Monolithically integrated optical resonators are disclosed. An optical resonator may be a nanopillar optical resonator that is formed directly on a substrate and promotes a helically-propagating cavity mode. The helically-propagating cavity mode may result in significant reflection or, total internal reflection at an interface of the nanopillar optical resonator and the substrate even if refractive indices of the nanopillar optical resonator and the substrate are the same or similar. As a result, strong optical feedback, and thus strong resonance, may be provided in the nanopillar optical resonator.

Nanopillar optical resonator

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&#xb0; C. Each nanoneedle has a sharp 2 to 5 nanometer (nm) tip, a 600 nm wide base and a 4 micrometer (&#x3bc;m) length. Thus, the disclosed nanoneedles are substantially hexagonal needle-like crystal structures that assume a 6&#xb0; to 9&#xb0; 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.

Nanoneedle plasmonic photodetectors and solar cells

Planar lenses and reflectors are described comprising subwavelength high-contrast gratings (HCG) having high index of refraction grating elements spaced apart from one another in straight and/or curved segments and surrounded by low index material. The high-contrast grating is configured to receive an incident wave which excites multiple modes within the high-contrast grating and is focused for reflection and/or transmission by said high contrast grating. The width of the high contrast grating bars vary along a distribution direction of the grating bars which is perpendicular to the length of the grating bars and/or varies along the length of one or more grating bars to focus said reflection and/or transmission. The HCG is configured to provide double focusing, whose use is exemplified within a vertical cavity surface emitting laser (VCSEL) structure using focusing HCG structures for both the top and bottom mirrors.

Planar, high NA, low loss transmitting or reflecting lenses using sub-wavelength high contrast grating

The present disclosure provides a method for 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&#xb0; C. Each nanoneedle has a sharp 2 to 5 nanometer (nm) tip, a 600 nm wide base and a 4 micrometer (&#x3bc;m) length. Thus, the disclosed nanoneedles are substantially hexagonal needle-like crystal structures that assume a 6&#xb0; to 9&#xb0; 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.

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.

High contrast grating based saturable absorber for mode-locked lasers and its applications in passively mode-locked vertical-cavity surface-emitting lasers

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.

HCG reflection enhancement in diverse refractive index material

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.

Ultra-low loss hollow core waveguide using high-contrast gratings

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.

Sub-wavelength grating integrated VCSEL

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. The sub-wavelength grating reflectors may be used in a variety of settings such as tunable etalon filters and as a replacement for conventional distributed Bragg reflectors.

Ultra broadband mirror using subwavelength grating

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.

Growing community of inventors

Union City, CA, United States of America

Connie J Chang-Hasnain