Patent Description:
The use of devices utilizing free-space laser beams have been proven for numerous applications in three-dimensional mapping and imaging, such as geological surveying, and control and navigation for autonomous vehicles. Light detection and ranging (LiDAR) has emerged as a technology for determining a variable distance of an object by transmitting a beam towards an object and measuring the time for light reflected off the object to return. In this context, the light beam has to be transmitted towards the object. To be able to map a target area around the sensor, the sensor's beam has to be oriented or steered in different directions.

Of course, mechanically moving the sensor is one way to achieve beam steering. One way to steer the beam of a LiDAR sensor without mechanical movement of the sensor is an Optical Phased Array (OPA). OPAs provide a more flexible and efficient beam steering device.

OPAs are designed to generate beams with different phase shifts so as to create patterns of constructive and destructive interference forming an output beam. However, conventional OPAs are not scalable and complex in both the architecture as well as electrical control when a large number of outputs are to be realized.

<CIT> discloses an optical beam steering device comprising a laser source, a beam splitter network, a plurality of networks of phase shifter coupled to respective antennas.

<CIT> and <CIT> disclose similar optical beam steering devices.

Thus, an aim of the present invention is to overcome the drawbacks of the prior art.

According to the invention, a optical beam steering device and a method for beam steering are provided, as defined in the accompanying claims.

OPAs (Optical Phased Arrays) operate by transmitting a plurality of beams through an array antenna that superimpose (i.e., combine) in the far-field to form an output beam. Each of the plurality of beams undergoes a different phase shift so each of the transmitted beams is emitted at different times. This may result in the output optical beam being transmitted at an angle, known as the beam steering angle. The coverage of the beam steering device may be defined by the range of the beam steering angle.

OPAs typically comprise three elements: a beam splitting network to split the input of the OPA into a plurality of channels, a network of phase shifters configured to generate the phase difference between antenna elements, and the antenna elements.

Typically, OPAs utilize a phase shifter on each of the channels, except one, to cause an equal phase difference (e.g. a different phase shift) between adjacent channels. However, to generate a different phase shift between adjacent channels, a different voltage signal must be applied to each of the individual phase shifters. This may require each of the phase shifters to be controlled by individual and connected electronic circuits.

While optical phased arrays (OPAs) allow for non-mechanical beam steering of a LiDAR sensor, limitations still exist. As the quantity of channels increases, the number of individual and connected electronic circuits required to control the phase shift increases. Problematically, this results in an increase in power consumption and makes controlling the phase shift of each of the channels very difficult or even impossible.

Hereinbelow, an optical transmitter such as an optical beam steering device is described, that can steer an output beam with an improved coverage without an increase in the difficulty of controlling the phase shift of the channels. More specifically, a beam steering device is described, that has an increased beam steering angle range and does not require additional circuitry as the quantity of channels in the OPA increases.

<FIG> is a schematic diagram of a beam steering device according to an embodiment of the present application.

Referring to <FIG>, the beam steering device <NUM> includes a laser source <NUM> coupled to an optical phased array (OPA) <NUM>.

The OPA <NUM> may be formed on a silicon based platform such as silicon nitride using silicon photonics technology known in the art. The laser source <NUM> may be coupled to the OPA <NUM> via an optical fiber or may be included in the OPA <NUM>.

The OPA <NUM> comprises a beam splitter network <NUM> configured to split the laser beam generated by the laser source <NUM> into N outputs.

The N outputs may be coupled to an antenna <NUM> configured to couple and emit the each of N outputs into free space forming an optical output beam <NUM>.

The OPA <NUM> will be described in more detail in <FIG> (not belonging to the invention) as well as <FIG> below. As described hereinbelow, the OPA <NUM> may be configured to electronically steer the beam over a wider angle to obtain improved coverage area.

<FIG> are schematic diagrams of embodiments of the optical phase array (OPA) <NUM> configured to steer an output optical beam with improved coverage.

<FIG> illustrate schematic diagrams of an optical phased array of a beam steering device configured to steer a beam around a central beam axis, where <FIG> illustrates a schematic diagram of the optical phased array when it is configured to steer an output optical beam in a first direction, and <FIG> illustrates a schematic diagram of the optical phased array when it is configured to steer the output optical beam in a second direction opposite the first direction.

In <FIG>, the plurality of N outputs of the beam splitter network <NUM> are generated around a central beam axis <NUM>.

In <FIG>, the beam splitter network <NUM> comprises a plurality of stages of optical beam splitters <NUM>. The optical beam splitters <NUM> may comprise <NUM>×<NUM> Y-junction tree or multimode interference (MMI) optical splitters.

The beam splitter network <NUM> comprises i stages of optical beam splitters <NUM>, where i is an integer greater than or equal to <NUM>. The value of i may be determined based on the desired value of N outputs using the formula, N = <NUM>i. For example, as illustrated in <FIG>, an eight output beam splitter network <NUM> may require three stages of optical beam splitters <NUM> (i.e., <NUM> = <NUM><NUM>). Although <FIG> illustrates an OPA <NUM> with eight outputs, the OPA <NUM> may support any suitable quantity of outputs.

The quantity of optical beam splitters <NUM> may increase between each progressive stage. For instance, each stage of the beam splitter network <NUM> may comprise <NUM>i-<NUM> optical beam splitters <NUM>. For example, a first stage of the beam splitter network <NUM> (i.e., i=<NUM>) may include one optical beam splitter <NUM>, a second stage of the beam splitter network <NUM> (i.e. i=<NUM>) may include two optical beam splitters <NUM>, and the third stage of the beam splitter network <NUM> (i.e. i=<NUM>) may include four optical beam splitters <NUM>.

Each of the optical beam splitters <NUM> of <FIG> includes an input <NUM>, a first output waveguide <NUM>, and a second output waveguide <NUM>.

In <FIG>, the first output waveguides <NUM> and the second output waveguides <NUM> of the final stage of the beam splitter network <NUM> are each coupled to an antenna <NUM>. The antenna <NUM> may be an array antenna. In <FIG>, the antenna <NUM> comprises arrays of gratings <NUM>. The arrays of gratings <NUM> may comprise linear gratings. The length of each the linear gratings may be equal. In other words, the N outputs of the beam splitter network <NUM> may each be further coupled to an array of gratings <NUM>.

The optical phased array (OPA) <NUM> includes a first network of first phase shifters <NUM> configured to steer the output optical beam <NUM> in a first direction away from a longitude direction <NUM> and a second network of second phase shifters <NUM> configured to steer the output optical beam <NUM> in a second direction away from the longitude direction <NUM> opposite to the first direction.

In <FIG>, the first network of first phase shifters <NUM> is coupled to a first driver <NUM>. The second network of second phase shifters <NUM> is coupled to a second driver <NUM>. The first phase shifters <NUM> and the second phase shifters <NUM> are here connected to common reference potential such as a ground terminal <NUM>.

Each of the first output waveguides <NUM> of the beam splitter network <NUM> is associated to at least one first phase shifter <NUM>. The first output waveguide <NUM> of each stage may be associated with a different quantity of first phase shifters <NUM>. The quantity of first phase shifters <NUM> associated with the first output waveguides <NUM> on an ith stage of the beam splitter network <NUM> may be equal to <MAT>. For example, as illustrated in <FIG>, the first output waveguide <NUM> of an optical beam splitter <NUM> in a first stage (i.e. i=<NUM>) may be associated to four first phase shifters <NUM>, the first output waveguide <NUM> of each optical beam splitter <NUM> in a second stage (i.e. i=<NUM>) may be associated to two first phase shifters <NUM>, and the first output waveguide <NUM> of each optical beam splitter <NUM> in a third stage (i.e. i=<NUM>) may be associated to one first phase shifter <NUM>.

Similarly, each of the second output waveguides <NUM> of the beam splitter network <NUM> is associated to at least one second phase shifter <NUM>. The quantity of second phase shifters <NUM> may be equal to the quantity of first phase shifters <NUM> in each stage of the beam splitter network <NUM>.

For example, as illustrated in <FIG>, the second output waveguide <NUM> of an optical beam splitter <NUM> in a first stage (i.e. i=<NUM>) may be associated to four second phase shifters <NUM>, the second output waveguide <NUM> of each optical beam splitter <NUM> in a second stage (i.e. i=<NUM>) may be associated to two second phase shifters <NUM>, and a second output waveguide <NUM> of each optical beam splitter <NUM> in a third stage (i.e. i=<NUM>) may be associated to one second phase shifter <NUM>. The first phase shifters <NUM> and the second phase shifters <NUM> may be identical. The first phase shifters <NUM> and the second phase shifters <NUM> may comprise thermal or electro-optical phase shifters.

Advantageously, coupling both of the networks of phase shifters to a single respective driver allows the quantity of N outputs to be increased without requiring additional drivers. However, a driver may be provided for each phase shifter <NUM>, <NUM> or other combinations may be considered, if desired.

As described above, the optical phased array (OPA) <NUM> may be configured to steer the output optical beam <NUM> in opposite directions away from the longitude direction <NUM>. As understood by those with ordinary skill in the art, the output optical beam <NUM> may have a phase front <NUM>. The first direction may be defined as either a positive beam steering angle θ or a negative beam steering angle -θ measured with respect to the central beam axis <NUM>. The second direction may be defined as a beam steering angle with the opposite sign. The central beam axis <NUM> may be located along an axis that may be at an angle to the beam steering device <NUM> (See <FIG>).

In the example of <FIG>, the first network of first phase shifters <NUM> may be configured to steer the output optical beam <NUM> in a first direction -θ away from the longitude direction <NUM>.

The output optical beam <NUM> may be steered in the first direction -θ by activating the first driver <NUM>. When activated, the first driver <NUM> may apply a first potential to each of the first phase shifters <NUM>. The first potential may configure the first phase shifters <NUM> to add a first phase offset to each optical beam passing through the first output waveguides <NUM>. Each of the first phase shifters <NUM> that an optical beam passes through may add a phase shift of δΦ. When the first driver <NUM> is activated, and the second driver <NUM> is idle, the first phase offset added to each beam traveling through the first output waveguides <NUM> may equal <MAT>. Each of the beams traveling through the second output waveguides <NUM> may not undergo a phase shift. This may result in a constant phase difference equal to -δΦ between adjacent N outputs along the longitude direction <NUM> (or vice versa).

For example, in a first stage of the beam splitter network <NUM>, the laser beam generated from the laser source <NUM> may be split by an optical beam splitter <NUM> into a first beam B1 traveling along a first path through the first output waveguide <NUM> and a second beam B2 traveling along a second path through the second output waveguide <NUM>. A first phase offset may not be added to the second beam B2 because it does not pass through any first phase shifters <NUM>. A first phase offset equal to δΦ may be added to the first beam B1 by each of the four first phase shifters <NUM> it passes through so that the total phase offset is equal to <NUM>* δΦ.

In a second stage of the beam splitter network <NUM>, a first further optical beam splitter <NUM> may be configured to split the first beam B1 into a third beam B3 traveling along a third path and a fourth beam B4 traveling along a fourth path, and a second further optical beam splitter <NUM> may be configured to split the second beam B2 into a fifth beam B5 traveling along a fifth path and a sixth beam B6 traveling along a sixth path.

The third beam B3 and the fifth beam B5 may each travel through a first output waveguide <NUM> of the two further optical beam splitters <NUM>, while the second beam B2 and fourth beam B4 may each travel through a second output waveguide <NUM> of the two further optical beam splitters <NUM>.

The third beam B3 and the fifth beam B5 each pass through two first phase shifters <NUM> while the fourth beam B4 and sixth beam B6 do not. An additional first phase offset of <NUM>* δΦ may be added to both the third beam B3 and fifth beam B5 from the two first phase shifters <NUM> they both pass through. An additional first phase offset may not be added to the fourth beam B4 and sixth beam B6 because they do not pass through any first phase shifters <NUM>. Therefore, a first phase offset equal to <NUM>* δΦ may be added to the third beam B3, a first phase offset equal to <NUM>* δΦ may be added to the fourth beam B4, a first phase offset equal to <NUM>* δΦ may be added to the fifth beam B5, and a first phase offset may not be added to the sixth beam B6.

At the final stage of the beam splitter network <NUM> additional optical beam splitters <NUM> may split a respective beam into two outputs. The index of each of the N outputs may be defined as n and range from <NUM> to N along the longitude direction <NUM>. Referring back to <FIG>, the third through sixth beams may each be split into two outputs by each of the four optical beam splitters <NUM>, resulting in eight outputs. The third beam B3 may be split into a first output O1 (e.g. n=<NUM>) and a second output O2, the fourth beam B4 may be split into a third output O3 and a fourth output O4, the fifth beam B5 may be split into a fifth output O5 and a sixth output O6, and the sixth beam B6 may be split into a seventh output O7 and an eighth output O8.

In the same manner discussed above, the beams traveling through each first output waveguide <NUM> of each optical beam splitter <NUM> of the third (and final) stage will pass through one first phase shifter <NUM> while the other beams do not. Thus, an additional first phase offset equal to δΦ may be added to the beams traveling through each of the first output waveguides <NUM>. The N outputs with odd n values (i.e. first, third, fifth, and seventh) may pass through the first output waveguides <NUM> while the N outputs with even n values (i.e. second, fourth, sixth, eighth) may pass through the second output waveguides <NUM>. Therefore, the beam corresponding to the first output O1 may have a first phase offset equal to <NUM>*δΦ, the beam corresponding to the second output O2 may have a first phase offset equal <NUM>* δΦ, the beam corresponding to the third output O3 may have a first phase offset equal to <NUM>* δΦ, the beam corresponding to the fourth output O4 may have a first phase offset equal to <NUM>* δΦ, the beam corresponding to the fifth output O5 may have a first phase offset equal to <NUM>* δΦ, the beam corresponding to the sixth output O6 may have a first phase offset equal to <NUM>* δΦ, the beam corresponding to the seventh output O7 may have a first phase offset equal to δΦ, and a first phase offset may not be added to the beam corresponding to the eighth output.

Therefore, the first phase offset added to each of the N outputs may be equal to (N-n)δΦ. The first phase offset added to each of the N outputs may range from (N-n)δΦ to o with a constant phase difference along the longitude direction <NUM>, regardless of the value of N. This may result in a negative constant phase difference -δΦ between N outputs along longitude direction <NUM>. Therefore, the first phase shifters <NUM> may steer the output optical beam <NUM> in the first direction -θ (or vice versa).

As understood by those with ordinary skill in the art, the first phase shifters <NUM> may configure a phase difference with either a positive sign or a negative sign based on the first potential so as to result in a positive or negative beam direction with respect to the longitude direction <NUM>. In other words, the first network of first phase shifters <NUM> may be configured to only steer the output optical beam <NUM> with only either a positive beam steering angle θ or a negative beam steering angle -θ. Advantageously, the second network of second phase shifters <NUM> may be configured to provide a phase shift with the opposite sign. One advantage of this is that it allows for the output optical beam <NUM> to be steered in both directions of the central beam axis <NUM>. In other words, the range of the beam steering angle may be doubled.

Referring to <FIG>, after steering the beam in the first direction -θ, the first driver <NUM> may be deactivated, and the second driver <NUM> may be activated. The second driver <NUM> may transmit a second potential to each of the second phase shifters <NUM>. The second potential may be the same as the first potential.

The second potential may configure the second phase shifters <NUM> to steer the output optical beam <NUM> in a second direction θ. The second direction may be defined as a positive beam steering angle θ or a negative beam steering angle -θ so long as it is opposite the first direction.

The second potential may configure the second phase shifters <NUM> to add a second phase offset to each optical beam passing through the second output waveguides <NUM>. The second phase offset may be different than the first phase offset. For example, the added second phase offset may be opposite to the first phase offset. In other words, the phase difference between N outputs along the longitude direction <NUM> provided by the first phase shifters <NUM> and the second phase shifters <NUM> may have opposite signs. The second phase difference added to each of the N outputs may be equal to (n-<NUM>)δΦ. This will be discussed in more detail below.

Continuing the example discussed in <FIG> above, in the first stage of the beam splitter network <NUM> a second phase offset equal to <NUM>* δΦ may only be added to the second beam B2 due to each of the four second phase shifters <NUM> it passes through.

In the second stage of the beam splitter network, a second phase offset of <NUM>* δΦ may only be added to the fourth beam B4 and sixth beam B6 due to the two second phase shifters <NUM> they both pass through.

In the final stage of the beam splitter network, a second phase offset of δΦ may only be added to N outputs with even indices (i.e. second, fourth, sixth, and eighth) due to the one second phase shifter <NUM> they pass through.

Therefore, a second phase offset may not be added to the beam corresponding to the first output O1, the beam corresponding to the second output O2 may have a second phase offset equal to δΦ, the beam corresponding to the third output O3 may have a second phase offset equal to <NUM>*δΦ, the beam corresponding to the fourth output O4 may have a second phase offset equal to <NUM>*δΦ, the beam corresponding to the fifth output O5 may have a second phase offset equal to <NUM>*δΦ, the beam corresponding to the sixth output O6 may have a second phase offset equal to <NUM>*δΦ, the beam corresponding to the seventh output O7 may have a second phase offset equal to <NUM>*δΦ, and the beam corresponding to the eighth output O8 may have a second phase offset equal to <NUM>*δΦ.

Advantageously, this may allow the output optical beam <NUM> to be steered in a second direction θ away from the longitude direction <NUM>. One advantage of this is that it doubles the range of the beam steering angle.

In some situations, an optical phased array (OPA) <NUM> may be configured to have a central beam axis <NUM> disposed at a fixed offset angle. Advantageously, this allows for an output beam to be positioned and steered around a central beam axis <NUM> pointing in different directions.

<FIG> illustrates a side view of the beam steering device. <FIG> functions to provide an understanding of how the central beam axis <NUM> is located away from a device axis <NUM> perpendicular to the beam steering device <NUM>. Referring to <FIG>, as understood by those with ordinary skill in the art, the output optical beam <NUM> and the central beam axis <NUM> may be formed in the half-space above the device <NUM>. In other words, the central beam axis <NUM> may be disposed at an emission angle Φ measured with respect to the device axis <NUM>. This is because light emission from the antenna is at an angle to the surface of the device <NUM> referred herein as the emission angle Φ.

<FIG> illustrate schematic diagrams of an optical phased array of a beam steering device, where <FIG> illustrates a schematic diagram of an optical phased configured to have a central beam axis disposed at an offset angle in a first direction, and <FIG> illustrates a schematic diagram of an optical phased configured to have a central beam axis disposed at an offset angle in a second direction.

Unlike the prior embodiments in which the central beam axis was symmetrically located along the main axis, here, the central beam axis is offset at an angle to the main axis. In other words, the beam angle is not symmetric with the main axis. As will be described in <FIG>, these OPAs enable a larger spread in beam angle in the beam steering device.

Referring to <FIG>, a positive offset angle OPA 204A may be further configured to have a central beam axis <NUM> disposed in a first direction away from a main axis <NUM> perpendicular to the antenna <NUM>. The first direction may be defined as an offset angle Ψ between the central beam axis <NUM> and the main axis <NUM> perpendicular to the antenna <NUM>. For example, a central beam axis <NUM> disposed in the first direction may be defined as a central beam axis <NUM> with a positive fixed offset angle Ψ (or vice versa).

Here, the antenna <NUM> further includes N linear waveguides <NUM> and a plurality of N fixed phase shifters <NUM>. The plurality of N fixed phase shifters <NUM> are coupled between the beam splitter network <NUM> and the N linear waveguides <NUM>. In other words, here the inputs of N fixed phase shifters <NUM> are coupled to the N outputs of the beam splitter network <NUM> and the outputs of the N fixed phase shifters <NUM> are coupled to the inputs of each of the N linear waveguides <NUM>.

The N fixed phase shifters <NUM> may have different optical path lengths. The difference of the optical path length between couples of the N fixed phase shifters <NUM> may be equal. For example, the optical path length of the N fixed phase shifters <NUM> may decrease along the longitude direction <NUM> to form a fixed offset angle Ψ in the first direction. As understood by those with ordinary skill in the art, the direction of the fixed offset angle Ψ will be in the direction of increasing optical path lengths. Also, the longer the optical path length of the N fixed phase shifters <NUM>, the greater the magnitude of the fixed offset angle Ψ. Therefore, the magnitude and direction of the fixed offset angle Ψ may be configured based on the optical path lengths of each of the N fixed phase shifters <NUM>.

Referring back to <FIG>, each of the N fixed phase shifters <NUM> may comprise N curved waveguides with different curvatures. As understood by those with ordinary skill in the art, the greater the curvature, the longer the optical path length (or vice versa). Therefore, the decrease in optical path lengths may be realized by decreasing the curvature of the N fixed phase shifters <NUM> along the longitude direction <NUM>.

Referring to <FIG>, a negative offset angle OPA 204B may be further configured to have a central beam axis <NUM> disposed in a second direction away from the main axis <NUM>. The second direction may be opposite the first direction. For example, the second direction may be defined as a negative fixed offset angle -Ψ (or vice versa), so long as it is opposite the first direction.

For the same reasons discussed above, the magnitude and sign of the second direction may depend on the difference in optical path length of the N fixed phase shifters <NUM>. Therefore, the central beam axis <NUM> may be disposed in with a negative fixed offset angle -Ψ by increasing the optical path length (or curvature) of each of the N fixed phase shifters <NUM> along the longitude direction <NUM>.

<FIG> illustrates a process flow of steering an output optical beam with improved coverage.

As illustrated in block <NUM>, and described with reference to <FIG>, a laser source <NUM> is coupled to optical phased array (OPA) <NUM> (or 204A, 204B). The OPA <NUM> (or 204A, 204B) comprises beam splitter network <NUM> comprising the plurality of N outputs around central beam axis <NUM>, the first network of first phase shifters <NUM>, and the second network of second phase shifters <NUM>. The OPA <NUM> (or 204A, 204B) may have any of the configurations disclosed in <FIG> and <FIG>.

As next illustrated in block <NUM>, and described with reference to <FIG>, the output optical beam <NUM> is generated around the central beam axis <NUM> at the output of the beam splitter network <NUM>. The output optical beam <NUM> may be formed around the central beam axis by being steered in a first direction -θ and a second direction θ (or vice versa).

The output optical beam <NUM> may be steered in the first direction by applying a first potential to each of the first phase shifters <NUM> with the first driver <NUM>. The first direction may be a positive beam steering angle θ or a negative beam steering angle -θ. The output optical beam <NUM> may be steered in the first direction in the same manner described in <FIG>.

The output optical beam <NUM> may be steered in a second direction away from the central beam axis <NUM>. The output optical beam <NUM> may be steered in the second direction by deactivating the first driver <NUM> and supplying a second potential to each of the second phase shifters <NUM> using the second driver <NUM>. The second direction may be defined as a beam steering angle with an opposite sign of the first direction. The output optical beam <NUM> may be steered in the first direction in the same manner described in <FIG>.

The beam steering device may comprise a plurality of optical phased arrays (OPAs) to increase the range of coverage of a beam steering device without requiring additional circuitry.

<FIG> illustrate schematic diagrams of a beam steering device comprising a plurality of optical phased arrays (OPAs), where <FIG> illustrates a beam steering device with an even number of optical phased arrays (OPAs), and <FIG> illustrates a beam steering device with an odd number of optical phased arrays (OPAs).

In <FIG>, an optical beam steering device <NUM> comprises laser source <NUM> coupled to the input of a switching matrix <NUM>. The switching matrix <NUM> comprises a plurality of z outputs that are coupled to a plurality of OPAs <NUM>. The switching matrix <NUM> may be configured to sequentially guide a laser beam emitted by the laser source <NUM> around a main axis <NUM> to each of the plurality of OPAs <NUM>.

The central beam axis <NUM> of each of the plurality of OPAs <NUM> may be different. This will be explained in more detail below.

Referring back to <FIG>, where z is an even number, the central beam axis <NUM> of each of the plurality of OPAs <NUM> may be configured to be disposed around the main axis <NUM>. In other words, the central beam axis <NUM> of each of the plurality of OPAs <NUM> may be configured to be disposed with a different fixed offset angle Ψ.

The magnitude of the fixed offset angle Ψ of each central beam axis <NUM> may be configured to increase away from the main axis <NUM>. The plurality of OPAs <NUM> may include a first set of OPAs <NUM> and a second set of OPAs <NUM>. The first set of OPAs <NUM> may include each of the OPAs positioned above the main axis <NUM>. The second set of OPAs <NUM> may comprise each of the OPAs positioned below the main axis <NUM>. The first set of OPAs <NUM> and the second set of OPAs <NUM> may comprise the same quantity of OPAs.

Similar to the positive offset angle OPA 204A in <FIG>, the first set of OPAs <NUM> may each have a central beam axis <NUM> configured to have positive fixed offset angles Ψ increasing in magnitude away from the main axis <NUM> (similar to the OPA described with respect to <FIG>).

Similar to the negative offset angle OPA 204B in <FIG>, the second set of OPAs <NUM> may each have a central beam axis <NUM> configured to have negative fixed offset angles -Ψ increasing in magnitude away from the main axis <NUM> (or vice versa).

As described above, the OPAs in the first set of OPAs <NUM> may include N fixed phase shifters <NUM> with decreasing optical path lengths along the longitude direction <NUM>. The OPAs in the second set of OPAs <NUM> may include N fixed phase shifters <NUM> with increasing optical path lengths along the longitude direction <NUM>. In other words, the longest fixed phase shifter of an OPA in the first set of OPAs <NUM> that is closer to the main axis <NUM> will be shorter than the shortest fixed phase shifter in an OPA in the first set of OPAs <NUM> further away from the main axis <NUM>. The same applies to the second set of OPAs <NUM>. Also, the optical path length of each of the N fixed phase shifters <NUM> of an OPA in the first set of OPAs <NUM> and an OPA in the second set of OPAs <NUM> that are equidistant from the main axis <NUM> may be equal. Therefore, the magnitude of fixed offset angles Ψ of OPAs that are equidistant from the main axis <NUM> may be equal. Advantageously, this allows for the central beam axis <NUM> of each of the plurality of OPA's <NUM> to increase away from the main axis <NUM>. One advantage of this is that it allows for increased beam coverage for the optical beam steering device <NUM> without additional circuitry. In other words, the switching matrix <NUM> may be used to steer the direction of the output of the optical beam steering device <NUM> by sequentially switching between the plurality of OPAs <NUM>.

<FIG> illustrates an alternative beam steering device, which works without having any possible central blindness. While the beam steering device described in <FIG> is optimized to steer the beam over a wider angle, the device may not be effective in analyzing objects that are located in the main axis of the device. To offset any such deficiencies, the beam steering device of <FIG> includes an additional OPA that is centrally located.

Referring to <FIG>, in embodiments where z is an odd integer, the first set of OPAs <NUM> and the second set of OPAs <NUM> may be separated by a central OPA <NUM> and positioned along the main axis <NUM>. The central OPA <NUM> positioned along the main axis <NUM> may be configured to have a central beam axis <NUM> formed along the main axis <NUM>. Therefore, the central beam axis <NUM> of the central OPA <NUM> does not have a fixed offset angle and therefore the central OPA <NUM> is similar to the OPA <NUM> described in <FIG>.

<FIG> illustrates a process flow of controlling a beam steering device including a plurality of optical phased arrays (OPAs).

As illustrated in block <NUM> and described with reference to <FIG>, a plurality of outputs of a switching matrix <NUM> may be coupled between laser source <NUM> and a plurality of optical phased arrays (OPAs) <NUM>. Each of the plurality of OPAs <NUM> may be configured to have an optical output direction around a main axis <NUM>. As described above, each of the plurality of OPAs <NUM> may be configured to generate an output optical beam <NUM> around a different central beam axis <NUM>. The central beam axis <NUM> of each of the plurality OPAs <NUM> may be disposed around the main axis <NUM>. Each central beam axis <NUM> may be disposed around the main axis <NUM> in the same manner discussed in <FIG>.

Claim 1:
An optical beam steering device (<NUM>) comprising:
a laser source (<NUM>) coupled to an optical phased array, OPA, (<NUM>; 204A, 204B), the OPA (<NUM>; 204A, 204B) comprising:
a beam splitter network (<NUM>) optically coupled to the laser source (<NUM>) and configured to split a laser beam generated by the laser source (<NUM>) into N outputs having a central beam axis (<NUM>) to generate an output optical beam (<NUM>);
a first network of first phase shifters (<NUM>) configured to steer the output optical beam (<NUM>) in a first direction at a positive beam steering angle (θ) or a negative beam steering angle (-θ) measured with respect to the central beam axis (<NUM>);
a second network of second phase shifters (<NUM>) configured to steer the output optical beam (<NUM>) in a second direction at the beam steering angle with an opposite sign with respect to the first direction;
an antenna (<NUM>) comprising N linear waveguides (<NUM>), the N linear waveguides (<NUM>) corresponding to the N outputs; and
N fixed phase shifters (<NUM>) coupled to the beam splitter network (<NUM>), each of the N fixed phase shifters (<NUM>) having a different optical path length than another one of the N fixed phase shifters (<NUM>), and each of the N linear waveguides (<NUM>) being coupled to an output of one of the N fixed phase shifters (<NUM>);
characterized by the optical beam steering device further comprising a switching matrix (<NUM>) coupled between the laser source (<NUM>) and the OPA (<NUM>; 204A, 204B), wherein the OPA (<NUM>; 204A, 204B) is part of a plurality of optical phased arrays, OPAs, (<NUM>, <NUM>, <NUM>, <NUM>).