A multi-stack graphene structure includes a graphene stack that includes graphene layers including amorphous graphene and thin film dielectric layers. The graphene layers include amorphous graphene. The graphene layers and the thin dielectric layers are alternately stacked on one another. The multi-stack graphene structure also includes an electric field former configured to apply an electric field to the graphene layers.

An optoelectronic device. The optoelectronic device operable to provide a PAM-N modulated output, the device comprising: M optical modulators, M being an integer greater than 1, the M optical modulators being arranged in a cascade, the device being configured to operate in N distinct transmittance states, as a PAM-N modulator, wherein, in each transmittance state of the N distinct transmittance states, each of the M optical modulators has applied to it a respective control voltage equal to one of: a first voltage or a second voltage. One or more of the modulators may include a substrate; a crystalline cladding layer, on top of the substrate; and an optically active region, above the crystalline cladding layer. The crystalline cladding layer may have a refractive index which is less than a refractive index of the optically active region.

A method for increasing the bandwidth of an electroabsorption modulator (EAM) includes the following steps. First, a plurality of p-i-n active waveguides for the EAM are defined on a p-i-n optical waveguide forming an EAM having a shorter p-i-n active waveguide length. Then, the bandwidth of the EAM can be increased. Second, the high-impedance transmission lines are used in series to connect the EAM sections to reduce the microwave reflection and then increase the device bandwidth. Finally, the impedance-controlled transmission lines for the signal input and output can not only reduce the parasitic effects resulting from packaging, but also reduce the microwave reflection resulting from the impedance mismatch at the device input and load.

Disclosed are integrated electro-absorption modulators (EAM) that are structured and/or operated to improve uniformity of the photocurrent density along the active region. In various embodiments, this improvement results from increased optical absorption at the rear of the EAM, e.g., as achieved by heating a region at the rear, increasing a bias voltage applied across the EAM towards the rear, or changing a material composition of an intrinsic layer towards the rear. In another embodiment, the improvement is achieved by coupling light from a waveguide into the EAM active region continuously along a length of the EAM, using overlap between a tapered section of the waveguide and the EAM.

An integrated differential Electro-Absorption Modulator (EAM) device. The device includes a substrate, an electrical driver, and two EAM modules. The electrical driver circuit is configured overlying the substrate member and has one output electrically coupled to the first EAM module and the other output electrically coupled to the second EAM module. The first and second EAM modules have a first and a second output, respectively. A beam splitter can be configured to split an optical input into two optical outputs, each of which can be optically coupled to the optical inputs of the first and second EAM modules.

An optical modulator of an optical transceiver can be calibrated using intermediate frequency (IF) signals to generate accurate crossing point values (e.g., DC bias). A photodiode can measure output from the optical modulator at intermediate and high-speed frequencies to generate crossing point values that avoid crossing point errors. A target crossing point can be selected at any value (e.g., 40%, 50%) and bias values can be generated from IF signals and then stored in a lookup date for setting the modulator bias during operation.

An electro absorption modulating apparatus is provided. A plurality of electro absorption modulators are disposed on a light transmission path. A controller controls a selection driving circuit to select one of the plurality of electro absorption modulators to perform light modulation on a light beam transmitted by the light transmission path, so as to generate a light modulation signal.

One general aspect includes a system to tint at least a portion of a vehicle window, the system including: a memory configured to include one or more executable instructions and a processor configured to execute the executable instructions, where the executable instructions enable the processor to: monitor ambient light in a surrounding vehicle environment; and based on the ambient light, dim at least a portion of an OLED window located at a vehicle.

An optoelectronic device comprising: a silicon-on-insulator (SOI) substrate, the substrate comprising: a silicon support layer; a buried oxide (BOX) layer on top of the silicon support layer; and a silicon device layer on top of the BOX layer; a waveguide region, where a portion of the silicon device layer and a portion of the BOX layer underneath the portion of the device layer have been removed, the portion of the BOX layer having been replaced with a layer of silicon and a layer of crystalline oxide on top of the silicon; and a waveguide structure located directly on top of the crystalline oxide layer, the waveguide structure including a P doped region, and an N doped region with an intrinsic region in-between, creating a PIN junction across which a bias can be applied to create a modulation region.

A multi-stack graphene structure includes a graphene stack that includes graphene layers including amorphous graphene and thin film dielectric layers. The graphene layers include amorphous graphene. The graphene layers and the thin dielectric layers are alternately stacked on one another. The multi-stack graphene structure also includes an electric field former configured to apply an electric field to the graphene layers.