Optical phased array based on emitters distributed around perimeter

An emitter configuration layout for an optical phased array comprises a plurality of emitters arranged around a perimeter, and a plurality of waveguides, with each of the waveguides respectively coupled to one of the emitters. The plurality of emitters are operative to generate a single far-field peak.

BACKGROUND

There are numerous applications for which it is desirable to steer the direction of emission of a beam of light without the use of any moving parts. To this end, efforts have been made to design chip-scale optical phased arrays based on integrated photonics components. While breakthroughs have been made in one-dimensional beam steering and, to a lesser extent, two-dimensional beam steering, improvements in these technologies are still needed.

For example, a major limitation currently faced by two-dimensional beam steering is the inability to space individual emitters of an array (N×N) close enough to one another, which ideally should be at one-half wavelength (lambda/2). This results from the requirement for optically isolated waveguides to propagate among the emitters. This limitation translates to a limited steering range, as well as an increased number of emitted beams and a reduced power level in the beam of interest.

SUMMARY

An emitter configuration layout for an optical phased array comprises a plurality of emitters arranged around a perimeter, and a plurality of waveguides, with each of the waveguides respectively coupled to one of the emitters. The plurality of emitters are operative to generate a single far-field peak.

DETAILED DESCRIPTION

In the following detailed description, embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that other embodiments may be utilized without departing from the scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense.

Various emitter configurations for optical phased arrays are disclosed herein. The emitter configurations include a plurality of emitters arranged around a perimeter, and a plurality of waveguides that are each respectively coupled to one of the emitters. In some embodiments, the emitters can be arranged around the perimeter such that none of the waveguides are located between any of the emitters. The emitter configurations are operative to generate a single far-field peak.

The emitters can be arranged in various geometric patterns or shapes around the perimeter. In principle, the perimeter can encompass a variety of different shapes. In some embodiments, performance is enhanced for perimeter shapes possessing greater levels of radial symmetry. For example, the emitters can form a circular pattern around the perimeter, an elliptical pattern around the perimeter, a semi-circular pattern around the perimeter, or the like.

The present approach solves the problem of prior emitter arrays by rearranging the emitters around a perimeter. For example, instead of positioning the emitters in an N×N array configuration, the present emitters can be spaced equidistant along the perimeter, such as in a circular arrangement with a given radius. In such embodiments, there is no requirement for waveguides to pass among the emitters, and so the emitters can be placed much closer together than in conventional optical phased arrays.

An optical phased array based on the present emitter configurations can be fabricated using integrated optical waveguides through standard fabrication processes. For example, the waveguide design can include a 1×N splitter, N phase modulators (which may operate based on one of a number of effects), and a configuration of grating-assisted emitters. Driving electrodes for phase shifters can be included in the fabrication.

To operate an optical phased array device with the present emitter configuration, laser light is injected into an input waveguide facet. The phases of the N waveguide arms are controlled to control the direction of emission of the emitted beam.

Simulations have verified that various circular emitter configurations result in an improved steering range for the emitted beam, as well as better transfer of optical power into the single beam of interest.

The present emitter configurations can be implemented in various integrated photonics applications, light detection and ranging (LiDAR) systems, free-space optical communication systems, or the like.

Further details of various embodiments are described hereafter with reference to the drawings.

FIG. 1illustrates an emitter configuration layout100for an optical phased array, according to one embodiment. The emitter configuration layout100includes a plurality of emitters110each with a given emitter spot size, and arranged in a circular pattern, with a given radius (R), around a perimeter. The emitters110are each coupled to a respective waveguide120. In this embodiment, there are no waveguides between each of the emitters110, which provides for a reduced pitch.

FIGS. 2A-2Care emission profiles from numerically generated simulations corresponding to emitter configuration layout100.FIG. 2Ais a near-field emission profile200for 36 emitters in a circular configuration having a radius (R) of 13.5 μm.FIG. 2Bis a far-field emission profile210of the light generated by the 36 emitters with no steering of a central lobe, andFIG. 2Cis a far-field emission profile220of the light generated by the 36 emitters with steering of the central lobe. As shown inFIGS. 2B and 2C, a single peak (central lobe) is generated in the far-field by the circular configuration.

FIG. 3illustrates an emitter configuration layout300for an optical phased array, according to another embodiment. The emitter configuration layout300includes a plurality of emitters310arranged in a circular pattern, with a given radius (R), around a perimeter. The emitter configuration layout300has a reduced number of emitters compared to the embodiment ofFIG. 1. The emitters310are each coupled to a respective waveguide320. As shown inFIG. 3, there are no waveguides between each of the emitters310.

FIGS. 4A-4Care emission profiles from numerically generated simulations corresponding to emitter configuration layout300.FIG. 4Ais a near-field emission profile400for 25 emitters in a circular configuration having a radius of 13.5 μm.FIG. 4Bis a far-field emission profile410of the light generated by the 25 emitters with no steering of a central lobe, andFIG. 4Cis a far-field emission profile420of the light generated by the 25 emitters with steering of the central lobe. Note that for this reduced number of emitters, the quality of the far-field emission at emission angles sufficiently different from the central lobe is decreased.

FIG. 5illustrates an emitter configuration layout500for an optical phased array, according to a further embodiment. The emitter configuration layout500includes a plurality of emitters510arranged in a circular pattern, with a given radius (R), around a perimeter. The emitter configuration layout500has a reduced emitter spot size compared to the emitter spot size of the embodiment ofFIG. 1. The emitters510are each coupled to a respective waveguide520. As shown inFIG. 5, there are no waveguides between each of the emitters510. Reducing the emitter spot size gives a wider steering range.

FIGS. 6A-6Care emission profiles from numerically generated simulations corresponding to emitter configuration layout500.FIG. 6Ais a near-field emission profile600for 36 emitters in a circular configuration having a radius of 13.5 μm.FIG. 6Bis a far-field emission profile610of the light generated by the 36 emitters with no steering of a central lobe, andFIG. 6Cis a far-field emission profile620of the light generated by the 36 emitters with steering of the central lobe.

FIG. 7illustrates an emitter configuration layout700for an optical phased array, according to another embodiment. The emitter configuration layout700includes a plurality of emitters710arranged in a circular pattern, with a given radius (R), around a perimeter. The emitter configuration layout700has an increased configuration radius compared to the embodiment ofFIG. 1. The emitters710are each coupled to a respective waveguide720. As shown inFIG. 7, there are no waveguides between each of the emitters710.

FIGS. 8A-8Care emission profiles from numerically generated simulations corresponding to emitter configuration layout700.FIG. 8Ais a near-field emission profile800for 64 emitters in a circular configuration having a radius of 27 μm.FIG. 8Bis a far-field emission profile810of the light generated by the 64 emitters with no steering of a central lobe, andFIG. 8Cis a far-field emission profile820of the light generated by the 64 emitters with steering of the central lobe. As shown inFIGS. 8B and 8C, increasing the configuration radius decreases the central spot size and reduces the spacing of the fringes around the central lobe in the far-field.

FIG. 9illustrates an emitter configuration layout900of an optical phased array, according to a further embodiment. The emitter configuration layout900includes a plurality of emitters in a dual ring configuration, including an outer ring of emitters910aarranged in a circular pattern with first radius (R1), and an inner ring of emitters910barranged in a circular pattern with a second radius (R2) that is less than the first radius. The emitters910aare each coupled to a respective waveguide920a, and the emitters910bare each coupled to a respective waveguide920b. The outer ring of emitters910aare each positioned so as to be offset from the inner ring of emitters910b, such that the waveguides920bcoupled to the inner ring of emitters910brespectively extend between a pair of adjacent outer ring emitters910a.

FIGS. 10A-10Care emission profiles from numerically generated simulations corresponding to emitter configuration layout900.FIG. 10Ais a near-field emission profile1000for 72 emitters in a dual ring configuration, with an inner radius (R2) of 10.8 μm.FIG. 10Bis a far-field emission profile1010of the light generated by the 72 emitters with no steering of a central lobe, andFIG. 10Cis a far-field emission profile1020of the light generated by the 72 emitters with steering of the central lobe. As shown inFIGS. 10B and 10C, the dual ring configuration suppresses the fringes around the central lobe in the far-field.

While two concentric rings of emitters are shown in the embodiment ofFIG. 9, it should be understood that three or more concentric rings of emitters can be used in alternative embodiments, to provide for even greater fringe suppression.

FIG. 11illustrates an emitter configuration layout1100of an optical phased array, according to an alternative embodiment. The emitter configuration layout1100comprises a plurality of emitters arranged to have two independent polarizations, including a first set of emitters1110ahaving a first polarization and a second set of emitters1110bhave a second polarization that is different than the first polarization. In one embodiment, the first set of emitters1110aare arranged in a first semi-circular pattern, and the second set of emitters1110bare arranged in a second semi-circular pattern that faces the first semi-circular pattern. The emitters1110aare each coupled to a respective waveguide1120a, and the emitters1110bare each coupled to a respective waveguide1120b.

FIGS. 12A-12Care emission profiles from numerically generated simulations corresponding to emitter configuration layout1100.FIG. 12Ais a near-field emission profile1210for one half of a 36 emitter configuration having a radius of 13.5 μm, in which the emitters have a first polarization.FIG. 12Bis a near-field emission profile1220for the other half of the 36 emitter configuration, in which the emitters have a second polarization that is different than the first polarization.FIG. 12Cis a far-field emission profile1230of the light generated by the 36 emitter configuration, including a first lobe1240generated by the emitters with the first polarization (FIG. 12A), and a second lobe1250generated by the emitters with the second polarization (FIG. 12B).

While the two beams corresponding to first lobe1240and second lobe1250are separate beams possessing orthogonal polarization states, these two beams can be made to track each other, such that the beams overlap in the far-field. The orthogonal polarization states prevent interference between the two beams. This enables the two beams to contain and transmit separate data streams, such as polarization multiplexed data, while minimizing cross-talk between the data streams.

FIG. 13illustrates an emitter configuration layout1300of an optical phased array, according to a further alternative embodiment. The emitter configuration layout1300comprises a plurality of emitters arranged to have two independent phase gradients in a circular pattern. A first set of emitters1310ahave a first phase gradient and are alternatingly arranged with a second set of emitters1310bhaving a second phase gradient that is different than the first phase gradient. The emitters1310aare each coupled to a respective waveguide1320a, and the emitters1310bare each coupled to a respective waveguide1320b.

FIGS. 14A and 14Bare emission profiles from numerically generated simulations corresponding to emitter configuration layout1300.FIG. 14Ais a near-field emission profile1410for a 36 emitter configuration having a radius of 13.5 μm, in which the emitters have alternating independent phase gradients.FIG. 14Bis a far-field emission profile1420of the light generated by the 36 emitter configuration, including a first lobe1430and a second lobe1440. In this implementation, the beams corresponding to first lobe1430and second lobe1440are two separate beams that can be independently steered and controlled.

EXAMPLE EMBODIMENTS

Example 1 includes an emitter configuration layout for an optical phased array, comprising: a plurality of emitters arranged around a perimeter; and a plurality of waveguides, each of the waveguides respectively coupled to one of the emitters; wherein the plurality of emitters are operative to generate a single far-field peak.

Example 2 includes the emitter configuration layout of Example 1, wherein the plurality of emitters are arranged in a circular pattern around the perimeter.

Example 3 includes the emitter configuration layout of Example 1, wherein the plurality of emitters are arranged in an elliptical pattern around the perimeter.

Example 4 includes the emitter configuration layout of Example 1, wherein the plurality of emitters are arranged in a semi-circular pattern around the perimeter.

Example 5 includes the emitter configuration layout of any of Examples 1-4, wherein the plurality of emitters are arranged around the perimeter such that none of the waveguides are located between any of the emitters.

Example 6 includes the emitter configuration layout of any of Examples 1-2, wherein the plurality of emitters are arranged in at least two concentric rings, including an outer ring of emitters arranged in a circular pattern with a first radius, and at least one inner ring of emitters arranged in a circular pattern with a second radius that is less than the first radius.

Example 7 includes the emitter configuration layout of Example 6, wherein the outer ring of emitters are each positioned so as to be offset from the inner ring of emitters, such that the waveguides coupled to the inner ring of emitters respectively extend between a pair of adjacent outer ring emitters.

Example 8 includes the emitter configuration layout of any of Examples 6-7, wherein the plurality of emitters arranged in at least two concentric rings suppress fringes around a central lobe in the far-field.

Example 9 includes the emitter configuration layout of any of Examples 1-8, wherein the plurality of emitters are implemented in an integrated photonics application, a light detection and ranging (LiDAR) system, or a free-space optical communication system.

Example 10 includes an optical phased array, comprising: a plurality of emitters arranged around a perimeter, wherein the plurality of emitters include a first set of emitters having a first polarization, and a second set of emitters having a second polarization that is different than the first polarization; and a plurality of waveguides, each of the waveguides respectively coupled to one of the emitters.

Example 11 includes the optical phased array of Example 10, wherein the plurality of emitters are arranged in a circular pattern around the perimeter.

Example 12 includes the optical phased array of Example 11, wherein the first set of emitters are arranged in a first semi-circular pattern, and the second set of emitters are arranged in a second semi-circular pattern that faces the first semi-circular pattern.

Example 13 includes the optical phased array of any of Examples 10-12, wherein a far-field emission profile of light generated by the plurality of emitters includes a first lobe generated by the first set of emitters with the first polarization, and a second lobe generated by the second set of emitters with the second polarization.

Example 14 includes the optical phased array of Example 13, wherein each beam corresponding to the first lobe and the second lobe are separate beams possessing orthogonal polarization states, wherein each beam is configurable to track the other beam such that the beams overlap in the far-field.

Example 15 includes the optical phased array of Example 14, wherein the orthogonal polarization states prevent interference between the beams.

Example 16 includes an optical phased array, comprising: a plurality of emitters arranged around a perimeter, wherein the plurality of emitters include a first set of emitters having a first phase gradient and a second set of emitters having a second phase gradient that is different than the first phase gradient, the first set of emitters alternatingly arranged with the second set of emitters around the perimeter; and a plurality of waveguides, each of the waveguides respectively coupled to one of the emitters.

Example 17 includes the optical phased array of Example 16, wherein the plurality of emitters are arranged in a circular pattern around the perimeter.

Example 18 includes the optical phased array of any of Examples 16-17, wherein a far-field emission profile of light generated by the plurality of emitters includes a first lobe generated by the first set of emitters with the first phase gradient, and a second lobe generated by the second set of emitters with the second phase gradient.

Example 19 includes the optical phased array of Example 18, wherein each beam corresponding to the first lobe and the second lobe are separate beams that are independently steerable and controllable.