Teknologian Tutkimuskeskus Vtt Oy

Valtion Teknillinen Tutkimuskeskus

Timo Aalto

Matteo Cherchi

Mikko Harjanne

Manfred Eich

Dirk Jalas

Markku Rono

Sanna Arpiainen

Markku Kapulainen

Alexander Petrov

An optical assembly for realizing horizontal and vertical spot-size conversion to couple light from a thin waveguide to a thick waveguide is disclosed. The assembly comprises at least one first thin waveguide with a first section having a first optical mode field and a horizontal spot-size expansion section providing spot-size conversion for a first horizontal dimension of said first optical mode field of a light beam propagating in said first waveguide, and at least one second thick waveguide with a second section having a second optical mode field and a horizontal spot-size reduction section providing spot-size conversion for a second horizontal dimension of said second optical mode field of a light beam propagating in said second waveguide. The expanded end of said first waveguide is aligned and rotated to interface with the reduced end of said second waveguide, so that the mode fields in said first and second waveguides are rotated 90 degrees with respect to each other, whereby the spot size of a light beam so coupled between the first and second waveguides is expanded or shrunk in both transverse dimensions, depending on the direction of the light beam.

Optical 2D spot-size conversion

The invention concerns a polarization rotator, comprising a first waveguide layer containing at least a first waveguide, said first waveguide having an input end and an output end, a second waveguide layer having at least a second waveguide, said second waveguide having an input end and an output end, and at least a first vertical mirror element arranged at the end of at least one of said waveguides to couple light between the output end of the first waveguide and the input end of the second waveguide. The optical axis of said first or second waveguide which has the vertical mirror element at its end is rotated in its waveguide layer at a first angle in order to induce rotation of polarization of light coupled between said first and second waveguides with an amount that corresponds to said first angle.

Polarization rotators

The invention concerns a polarization rotator. The inventive polarization rotator comprises an optical coupler comprising a waveguide having at one first end at least a first port configured as an input port for polarized light and a second port configured as an output port for reflected polarized light, said waveguide having a second end opposite to said first end. It further comprises a birefringent waveplate having on one side a reflective surface, which waveplate is arranged to receive light from said second end of said waveguide and to reflect light transmitted out from said coupler back into said coupler. According to the invention, the waveplate is further configured to cause said birefringent material to rotate the polarization of said reflected light, which amount of rotation depends on an angle of rotation of said birefringent waveplate with respect to said optical coupler.

Polarization rotator

The invention relates to devices and methods for polarization splitting, where a first optical coupler having at least one input port which receives an input light beam, and at least two output ports at which said light beam, is split into at least a first and a second arms at a first end of said arms. At least one total internal reflection mirror is coupled to the second arm for inducing polarization-dependent phase shifts to the light beam propagating in the second arm, and a polarization-dependent phase difference between the second and the first arm. A second optical coupler having input ports is coupled to the second and opposite ends of the arms. The second coupler has at least one first output port at which light is coupled from said arms, so that the polarization-dependent phase shift of the at least one total internal reflection mirror causes polarization-dependent coupling of light from said input port to said output port.

Devices and methods for polarization splitting

The invention relates to optical waveguide components, such as Faraday rotators and their manufacture Faraday rotators based on silicon waveguides are provided, where the waveguide has folded or wound sections that are parallel to an externally applied magnetic field.

Integrated faraday rotator

The invention relates to photonic circuits, in particular to photonic circuits where light is escalated transferred between optical waveguides which are coupled to photonic devices. A first waveguide on a silicon substrate is provided having a first thickness and a first refractive index. A tapered second waveguide having a second thickness less than the first thickness and a second refractive index higher than said first refractive index is deposited on the first waveguide. At least one layer of an optically active material comprising a photonic device is deposited on the first waveguide adjacent to the second waveguide. The photonic device is interfaced with the wide end of the tapered second waveguide to provide an optical coupling, and the opposite narrow end of the tapered second waveguide is interfaced on top of the first waveguide to provide adiabatic light transfer between said first and second waveguides.

Light escalators in optical circuits between thick and thin waveguides

An optical multi-mode HIC (high index contrast) waveguide () for transporting electromagnetic radiation in the optical waveband, the waveguide comprising a guiding core portion () with higher refractive index, and cladding portion () with substantially lower refractive index configured to at least partially surround the light guiding core in the transverse direction to facilitate confining the propagating radiation within the core, the waveguide being configured to support multiple optical modes of the propagating radiation, wherein the waveguide incorporates a bent waveguide section () having bend curvature that is configured to at least gradually, preferably substantially continuously, increase towards a maximum curvature of said section from a section end.

Bent optical waveguide

The present invention concerns an optical fiber acting as a slab-coupled waveguide. The optical fiber has a cross-section comprising a core (), which is two dimensional and responsible for the horizontal confinement of the fiber's fundamental mode. A slab () is placed in the vicinity of the core (). The slab () extends substantially in a plane, acts as a mode sink for the core, and is at least three times wider than the core (). A cladding () surrounds the core () and the slab (). The cladding () is made of one or several materials with refractive indices lower than the core and slab materials. The core (), slab () and cladding () and any other protective or supportive structures attached to them form an overall structure that determines the mechanical properties of the fiber. The cross-section of the fiber is formed to make the fiber significantly more flexible in the direction perpendicular to the plane of the slab than in the plane of the slab.

Optical fiber with mode sink

A structure comprises an inner strip waveguide () and an outer rib waveguide () on a common substrate. The thicker inner waveguide () is patterned into an inner core layer (). The thinner outer waveguide () is patterned into an outer core layer (). The inner and outer waveguides are separated by a gap () being less than 500 nm. The structure forms an adiabatic coupler. In the method, the first (inner) waveguide () is patterned into the thicker inner core layer () by etching trenches (). A thinner outer silicon layer () is attached on top of the inner-core layer () and the first waveguide () to form an outer core layer (). The second (outer) waveguide () is patterned into the outer core layer ().

Structure comprising an adiabatic coupler for adiabatic coupling of light between two optical waveguides and method for manufacturing such a structure

A method for controlling an optoelectronic component that includes two waveguides. The refractive index of the first waveguide is changed periodically with a first control signal, the amplitude of which is changed between a first amplitude level and higher second amplitude level. The refractive index of the second waveguide is changed periodically with a second control signal, the amplitude of which is changed between the aforementioned first amplitude level and a lower third amplitude level. When the control signals are on their common first amplitude level, the refractive indices of the waveguides are equal and the phase difference between them is zero. When the first control signal is on the second amplitude level and the second control signal on the third amplitude level, the refractive indices of the waveguides are unequal so that their mutual phase difference has a predetermined target value.

Method for controlling an optoelectronic component

A waveguide, which is part of an integrated optical circuit is arranged onto a planar substrate, and has a core section propagating light to a direction of propagation. The waveguide is a conversion waveguide between a ridge-type waveguide and a strip waveguide. In the conversion waveguide, the core section is made of the one and same material so that the cross-section of the core section transverse to the direction of propagation of light is two-step from both edges. The conversion waveguide has two layers of different widths so that the height of the first layer is equal to the height of the ridge of the ridge-type waveguide, and the height of the second layer is equal to the height of the base part of the ridge-type waveguide.

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Espoo, Finland

Timo Aalto