Vi Systems Gmbh

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Vertically Integrated (vi) Systems Gmbh

Nikolay Ledentsov

Vitaly Shchukin

Joerg-Reinhardt Kropp

James A Lott

An in-plane-emitting semiconductor diode laser employs a surface-trapped optical mode existing at a boundary between a distributed Bragg reflector and a homogeneous medium, dielectric or air. The device can operate in both TM-polarized and TE-polarized modes. The mode exhibits an oscillatory decay in the DBR away from the surface and an evanescent decay in the dielectric or in the air. The active region is preferably placed in the top part of the DBR close to the surface. The mode behavior strongly depends on the wavelength of light, upon increase of the wavelength the mode becomes more and more extended into the homogeneous medium, the optical confinement factor of the mode in the active region drops until the surface-trapped mode vanishes. Upon a decrease of the wavelength, the leakage loss of the mode into the substrate increases. Thus, there is an optimum wavelength, at which the laser threshold current density is minimum, and at which the lasing starts. This optimum wavelength is temperature-stabilized, and shifts upon temperature increase at a low rate less than 0.1 nm/K, indicating wavelength-stabilized operation of the device. The approach applies also to semiconductor optical amplifiers or semiconductor gain chips which are also wavelength-stabilized. Reflectivity of the surface-trapped mode from an uncoated facet of the device can be extremely low, also &#x3c;1E&#x2212;4 or even &#x3c;1E&#x2212;5 which is particularly advantageous for amplifiers or gain chips. For diode lasers, a specific intermediate reflective coating can be deposited on the facet to put its reflectivity into a range from 0.5% to 3%, which lies within targeted values for lasers. An optical integrated circuit can employ wavelength-stabilized amplifiers operating in a surface-trapped mode, wherein such devices amplify light propagating along a dielectric waveguide.

Wavelength-stabilized near-field optoelectronic device

An optoelectronic device employs a surface-trapped TM-polarized optical mode existing at a boundary between a distributed Bragg reflector (DBR) and a homogeneous medium, dielectric or air. The device contains a resonant optical cavity surrounded by two DBRs, and an additional DBR section on top supporting the surface-trapped mode. Selective chemical transformation, like selective oxidation, etching or alloy composition intermixing form a central core and a periphery having different vertical profiles of the refractive index. Therefore, the longitudinal VCSEL mode in the core is non-orthogonal to the surface-trapped mode in the periphery, and the two modes can be transformed into each other. Such transformation allows fabrication of a number of optoelectronic devices and systems like a single transverse mode VCSEL, an integrated optical circuit operating as an optical amplifier, an integrated optical circuit combining a VCSEL and a resonant cavity photodetector, etc.

Optoelectronic device based on a surface-trapped optical mode

The invention discloses a semiconductor optoelectronic micro-device comprising at least one cavity and at least one multilayer interference reflector. The device represents a micrometer-scale pillar with an arbitrary shape of the cross section. The device includes a vertical optical cavity, a gain medium and means of injection of nonequilibrium carriers into the gain medium, most preferably, via current injection in a p-n-junction geometry. To allow high electric-to-optic power conversion at least one contact is placed on the sidewalls of the micropillar overlapping with at least one doped section of the device. Means for the current path towards the contacts and for the heat dissipation from the gain medium are provided. Arrays of micro-devices can be fabricated on single wafer or mounted on single carrier. Devices with different cross-section of the micropillar emit light at different wavelengths.

Micropillar optoelectronic device

An oxide-confined vertical cavity surface emitting laser including a distributed Bragg reflector (DBR) wherein the layers of the (DBR) includes a multi-section layer consisting of a first section having a moderately high aluminum composition, an second section which is an insertion having a low aluminum composition, and a third section which is an oxide-confined aperture formed by partial oxidation of a layer having a high aluminum composition (95% and above). A difference in aluminum composition between a high value in the aperture layer and a moderately high value in the first section prevents non-desirable oxidation of the first section from the mesa side while the aperture layer is being oxidized. A low aluminum composition in the second section prevents non-desirable oxidation in the vertical direction of the layer adjacent to the targeted aperture layer.

Reliable high-speed oxide-confined vertical-cavity surface-emitting laser

Optoelectronic device undergoes selective chemical transformation like alloy compositional intermixing forming a non-transformed core region and an adjacent to it periphery where transformation has occurred. Activated by selective implantation or diffusion of impurities like Zinc or Silicon, implantation or diffusion of point defects, or laser annealing, transformation results in a change of the refractive index such that the vertical profile of the refractive index at the periphery is distinct from that in the core. Therefore the optical modes of the core are no longer orthogonal to the modes of the periphery, are optically coupled to them and exhibit lateral leakage losses to the periphery. High order transverse optical modes associated to the same vertical optical mode have higher lateral leakage losses to the periphery than the fundamental transverse optical mode, thus supporting single transverse mode operation of the device. This approach applies to single transverse mode vertical cavity surface emitting lasers, edge-emitting lasers and coherently coupled arrays of such devices.

Optoelectronic device with enhanced lateral leakage of high order transverse optical modes into alloy-intermixed regions and method of making same

Optical beam quality of an optoelectronic device is improved by suppression of high-order transverse optical modes by their resonant interaction with the continuum of modes in the surrounding regions, such continuum being realized by replacement of one or several layers by layers having a lower refractive index. In particular, selective oxidation of GaAlAs-based vertical cavity surface emitting laser results in (Ga)AlO layers surrounding the aperture and having a lower refractive index than the original (Ga)AlAs layers. The continuum of optical modes originates due to the modification of the optical field in the areas surrounding the aperture caused by the low index insertions positioned to result in enhancement of the optical field in their vicinity. High-order lateral optical modes in the aperture region exhibit larger leakage losses than the fundamental lateral optical mode due to the resonant interaction with the continuum of modes outside the aperture, enabling single-mode lasing from a broad aperture vertical cavity surface emitting laser.

Optoelectronic device with resonant suppression of high order optical modes and method of making same

A laser system for generation of three-dimensional (3D) colored images based on laser sources generating light at a plurality of wavelengths including basic color range (red, green and blue) that illuminate a two-dimensional display, at a given color range wherein a plurality of 2D images formed at different depths by image light impinges on a first optical element, with wavelength-sensitive focal length. All images of the given colored range are perceived by the human's eyes as a single 3D image of this color range. 3D images in red, green and blue that are formed at different positions, are fused by a second optical element, with adjustable focal length. As the light is switched between red, green and blue color ranges, the adjustable focal length is adjusted to compensate a change of the focal length of the first element, so the human's eyes see a fully colored 3D image.

Laser system for generation of colored three-dimensional images

A method for fabrication of three-dimensional nanostructures on top of the surface of a first solid state material is disclosed, which includes steps of (i) deposition of a layer of a second solid state material forming a stable layer-like coverage of the surface, (ii) the subsequent deposition of a third solid state material, having a stronger binding energy with the first solid state material than the second solid state material, (iii) wherein the third solid state material replaces the second solid state material forming an interface with the first material and thus reduces the energy of the system, and (iv) where the resulting excess second solid state material forms three-dimensional nanostructures. The structure can be covered with another (fourth) solid state material, which eventually can be the same as the first material or a different one, and the three dimensional nanostructures form capped quantum dots or quantum wires. The deposition steps can be repeated and extended to provide necessary functionality in the resulting device structure.

Three-dimensional semiconductor nanoheterostructure and method of making same

A device for generation of three-dimensional images in the observer's eye using at least one two-dimensional display and an optical system with an adjustable focal length. The display generates planar images corresponding to the different depths of the designed three dimensional (3D) image and the images are then directed to at least one mirror or lens with the adjustable focal length synchronized to the particular image. The optical system generates virtual images at different virtual planes in such a way that the eye receives a complete 3D virtual image.

Device for generation of colored virtual three-dimensional images

An optoelectronic semiconductor device is disclosed wherein the device is a vertical-cavity surface-emitting laser or a photodiode containing a section, the top part of which is electrically isolated from the rest of the device. The electric isolation can be realized by etching a set of holes and selective oxidation of AlGaAs layer or layers such that the oxide forms a continuous layer or layers everywhere beneath the top surface of this section. Alternatively, a device can be grown epitaxially on a semi-insulating substrate, and a round trench around a section of the device can be etched down to the semi-insulating substrate thus isolating this section electrically from the rest of the device. Then if top contact pads are deposited on top of the electrically isolated section, the pads have a low capacitance, and a pad capacitance below two hundred femto-Farads, and the total capacitance of the device below three hundred femto-Farads can be reached.

Low capacitance optoelectronic device

A light-emitting device epitaxially-grown on a GaAs substrate which contains an active region composed of AlGaAs alloy or of related superlattices of this materials system is disclosed. This active region either includes tensile-strained GaP-rich insertions aimed to increase the forbidden gap of the active region targeting the bright red, orange, yellow, or green spectral ranges, or is confined by regions with GaP-rich insertions aimed to increase the barrier height for electrons in the conduction band preventing the leakage of the nonequilibrium carriers outside of the light-generation region.

Optoelectronic device with a wide bandgap and method of making same

A device representing a reflector, for example an evanescent reflector or a multilayer interference reflector, with at least one reflectivity stopband is disclosed. A medium with means of generating optical gain is introduced into the layer or several layers of the reflector. The optical gain spectrum preferably overlaps with the spectral range of the reflectivity stopband. This reflector is attached to multilayer passive cavity structure made of semiconducting, and/or dielectric, and/or metallic materials with the inserted tools of achieving wavelength selection of the optical modes. For example, volume Bragg gratings, distributed feedback gratings or patterns, using of vertical optical cavities surrounded by multilayer Bragg reflectors can be applied. The optical modes of the passive optical cavity partially penetrate into the gain region of the reflector. As a result of the interaction of the gain medium in the reflector region and the passive cavity modes, photons are generated or amplified in the passive cavity at wavelengths defined by the passive cavity modes. The materials selected for the passive cavity layers are chosen to provide the necessary temperature dependence of the effective index of refraction of the related optical modes of the passive cavity and serve as a tool to achieve the controlled temperature dependence of the wavelength of the emitted photons. In particular a complete suppression of the wavelength to temperature variations can be achieved. In another case a strong shift of the resonant wavelength or wavelengths with temperature may be realized. Thus the structure represents an optoelectronic device with controlled temperature dependence of the emission wavelength.

Optoelectronic device with controlled temperature dependence of the emission wavelength and method of making same

A device representing a reflector, for example, an evanescent reflector or a multilayer interference reflector with at least one reflectivity stopband is disclosed. A medium with means of generating optical gain is introduced into the layer or several layers of the reflector. The optical gain spectrum preferably overlaps with the spectral range of the reflectivity stopband. This device can be attached to air, semiconductor or dielectric material or multilayer structures and provide a tool for preferential amplification of the optical waves propagating at larger angles with respect to the interface with the evanescent or the multilayer interference reflector. Thus angle selective amplification or generation of light is possible. Several evanescent or interference reflectors can be used to serve the goal of preferable amplification the said optical waves.

Optoelectronic device and method of making same

An optoelectronic interconnect which includes optical transmitter and detector having capacitances below 150 femto-Farads each suitable for transmission of optical signals at speeds at and above 20 Gigabit per second at power consumption below 10 milliWatt per Gigabit per second.

Growing community of inventors

Berlin, Germany

Nikolay Ledentsov