A photonic chip. In some embodiments, the photonic chip includes a waveguide; and an optically active device comprising a portion of the waveguide. The waveguide may have a first end at a first edge of the photonic chip; and a second end, and the waveguide may have, everywhere between the first end and the second end, a rate of change of curvature having a magnitude not exceeding 2,000/mm.sup.2.

An optoelectronic device, including: a rib waveguide, the rib waveguide including: a ridge portion, which includes a temperature-sensitive optically active region, and a slab portion, positioned adjacent to the ridge portion; the device further comprising a heater, disposed on top of the slab portion wherein a part of the heater closest to ridge portion is at least 2 μm away from the ridge portion. The device may also have a heater provided with a bottom cladding layer, and may also include various thermal insulation enhancing cavities.

An electro-optically active device comprising: a silicon on insulator (SOI) substrate including a silicon base layer, a buried oxide (BOX) layer on top of the silicon base layer, a silicon on insulator (SOI) layer on top of the BOX layer, and a substrate cavity which extends through the SOI layer, the BOX layer and into the silicon base layer, such that a base of the substrate cavity is formed by a portion of the silicon base layer; an electro-optically active waveguide including an electro-optically active stack within the substrate cavity; and a buffer region within the substrate cavity beneath the electro-optically active waveguide, the buffer region comprising a layer of Ge and a layer of GaAs.

A semiconductor device according to the present invention includes a substrate, an active layer provided on the substrate, a cladding layer provided on the active layer, a contact layer provided on the cladding layer, the contact layer having an upper surface, a back surface which is a surface on an opposite side to the upper surface, and a side surface connecting the upper surface and the back surface, the contact layer is larger in width than the cladding layer; and an electrode that is in contact with the upper surface of the contact layer and the side surface of the contact layer from an upper end to a lower end of the side surface of the contact layer.

A transmitter optical subassembly may include an optical modulator for modulating output light from the light source. The optical modulator has a characteristic that a current depending on amount of optical absorption has a positive correlation with an applied voltage thereto. The transistor at the second terminal is connected in series to the optical modulator. A drive voltage applied to the optical modulator and the transistor is divided into a first voltage applied to the optical modulator and a second voltage applied to the transistor. A drive current flowing through the optical modulator and the transistor depends on the control signal input to the first terminal. The first voltage is based on the drive current and is subject to the characteristic of the optical modulator. The second voltage fluctuates in response to the first voltage.

An optical interconnect device and the method of fabricating it are described. The device includes an in-plane laser cavity transmitting a light beam along a first direction, a Franz Keldysh (FK) optical modulator transmitting the light beam along the first direction, a mode-transfer module including a tapered structure disposed after the FK optical modulator along the first direction to enlarge the spot size of the light beam to match an external optical fiber and a universal coupler controlling the light direction. The tapered structure can be made linear or non-linear along the first direction. The universal coupler passes the laser light to an in-plane external optical fiber if the fiber is placed along the first direction, or it is a vertical coupler in the case that the external optical fiber is placed perpendicularly to the substrate surface. The coupler is coated with highly reflective material.

Provided is an optical switch element capable of adjusting an output strength of light output from an optical switch to a fixed level. The optical switch element includes: an optical coupler configured to divide an input light into N fractions of light and output the N fractions of light, where N represents an integer equal to or larger than 2; N branch optical waveguides connected to an output side of the optical coupler; N light absorption gates connected to the respective N branch optical waveguides; and N output optical waveguides connected to the respective N light absorption gates, the optical coupler, the N branch optical waveguides, the N light absorption gates, and the N output optical waveguides being connected to one another in order, the N light absorption gates each being controlled to adjust an output strength of transmitted light output from the N output optical waveguides based on a loss amount acquired in advance by a light absorption effect or light amplification effect of the N light absorption gates.

A photonic waveguide assembly has a first arm comprising a first photonic waveguide transmitting a first light, an optical refractive index modulator positioned about said first photonic waveguide to modulate the phase or amplitude, or combination thereof of the first light traveling in the first photonic waveguide; a second arm comprising a second photonic waveguide transmitting a second light; and a passive contact that contacts at least a portion of the second photonic waveguide of said second arm.

In one embodiment, an electro-absorption modulator is configured to receive an optical light from an optical light source and outputs a modulated optical signal. The electro-absorption modulator includes a bias voltage that is used to set optimum predetermined modulation performance and an output power of the electro-absorption modulator. A controller is configured to measure a bias current of the optical light source and use a change of the bias current to determine a detuning change that occurs between the electro-absorption modulator and the optical light source. The controller uses the detuning change to automatically control the bias voltage of the electro-absorption modulator to maintain the predetermined modulation performance and maintain the output power of the electro-absorption modulator.

An electro-absorption modulator (EAM) is configured to include an on-chip AC ground plane that is used to terminate the high frequency RF input signal within the chip itself. This on-chip ground termination of the modulation input signal improves the frequency response of the EAM, which is an important feature when the EAM needs to support data rates in excess of 50 Gbd. By virtue of using an on-chip ground for the very high frequency signal content, it is possible to use less expensive off-chip components to address the lower frequency range of the data signal (i.e., for frequencies less than about 1 GHz).