On-chip optical phased array scanner with flat output intensity
Technical Field
The utility model belongs to the optoelectronic device field, concretely relates to optics phased array scanner on piece with flat output intensity.
Background
The optical phased array can be used in the laser radar, realizes large-angle and high-speed beam scanning, can also select the free space optical transmission angle, realizes data multiplexing in space, and increases the flexibility of an optical communication link.
The optical waveguide on the silicon substrate compatible with the CMOS process can be integrated with a laser to form an integrated chip from a light source to light beam deflection, and meanwhile, the scale integration is supported, so that the miniaturization development of a system is promoted. The optical phased array based on the optical waveguide on the silicon substrate has the characteristics of easiness in large-scale integration, low power consumption, low cost and the like, and has a great application prospect. The optical phased array based light beam deflection structure has the characteristics of small size, light weight, low power consumption and the like, meanwhile, optical communication and optical detection have requirements on light intensity, and the on-chip waveguide optical phased array scanner with flat output intensity has very important significance and practical value.
Disclosure of Invention
An object of the utility model is to provide an on-chip optical phased array scanner with flat output intensity. The utility model discloses optical phased array antenna design based on symmetry bending waveguide combines the advantages such as piece glazing waveguide easily integration, low, with low costs of energy consumption, realizes having flat, unanimous output peak intensity in the different light beam deflection range in far field.
The utility model provides an on-chip optical phased array scanner with flat output intensity comprises following part: the power divider comprises an input port (1), a multi-stage 3dB power divider (2), a phase modulator (3), a curved waveguide (4) and an output port (5).
The utility model discloses connect as follows: the input port (1) is connected with the multistage 3dB power divider (2), and each output path of the multistage 3dB power divider (2) is connected with one end of the phase modulator (3); the other end of the phase modulator (3) enters the region of the curved waveguide (4) through the waveguide; the tail end of the bent waveguide (4) is emitted out through the output port (5).
The basic principle of the utility model is as follows: laser input light source signal I0The input light source signal I can be input through the input port (1) and split through the multi-stage 3dB power splitter (2)0Is equally divided into 2nEach output path of the multistage 3dB power divider (2) is connected with the waveguide; each waveguide is provided with a phase modulator (3) for controlling phase difference among the waveguides, then the optical field of each waveguide path enters a bent waveguide (4) region, an included angle exists between the waveguide direction at the tail end of the bent waveguide (4) and a symmetric axis, after the optical field is emitted through an output port (5), the angle of the far field energy maximum value deviates from the symmetric axis, the angles of the waveguide far field energy maximum values in the upper half region and the lower half region are symmetric about the symmetric axis, and the square of the amplitude sum of the optical field of each waveguide far field hardly changes along with the change of the angle within the range of the far field deflection angle (-31 ℃). By controlling the phase difference of each path, emission peaks which are relatively flat in output intensity can be obtained at different beam deflection angles of a far field.
The input port (1) is connected with a laser and can have the characteristic of on-chip integration.
The multistage 3dB power divider (2) can equally divide input optical power into 2nA path.
The phase modulator (3) can modulate the phase of an optical field on a path and dynamically control the far field deflection angle of an output light beam.
The bent waveguide (4) can enable the maximum value of the output far-field energy to move towards a large-angle direction, and the distribution of the optical field energy in the far field is adjusted.
And the waveguide output end surfaces of the output ports (5) are not perpendicular to the waveguide direction and are in the same output plane, wherein the centers of the adjacent waveguide output end surfaces are equally spaced.
And a detector is arranged behind the output port (5) and is used for detecting the light field distribution of a far field.
The utility model discloses the profitable effect that has is:
the utility model discloses a method of introducing crooked waveguide and arranging in optical phased array antenna for on-chip optical phased array has far field emission peak intensity and does not change along with beam deflection angle, has effectively solved optical phased array far field emission peak intensity along with deflection angle increase and the quick decay problem. The wide-field-angle scanning laser radar and free space optical communication system can meet application requirements of wide-field-angle scanning laser radar, free space optical communication and the like.
The utility model discloses light beam deflection structure based on optics phased array on the piece, compatible with CMOS technology, have device compact structure, characteristics such as easy monolithic integration.
Drawings
Fig. 1 is a schematic diagram of the present invention.
Fig. 2(a) shows the upper half of the relative intensity vs. angle curve of the exit light from the curved waveguide in the far field.
Fig. 2(b) shows the lower half of the curve of the relative intensity vs. angle variation of the exit light from the curved waveguide in the far field.
Fig. 3 is a simulation result of the intensity distribution of the far-field emitted optical field as a function of the deflection angle of the beam.
In the figure: the power divider comprises an input port (1), a multi-stage 3dB power divider (2), a phase modulator (3), a curved waveguide (4) and an output port (5).
Detailed Description
The present invention will be further explained with reference to the accompanying drawings.
As shown in fig. 1, an on-chip optical phased array scanner with flat output intensity comprises, in order from left to right: the power divider comprises an input port (1), a multi-stage 3dB power divider (2), a phase modulator (3), a curved waveguide (4) and an output port (5). LaserThe input light source signal of the optical device is input through the input port (1), and power is equally divided into 2 parts through the multi-stage 3dB power divider (2)nEach waveguide path is provided with a phase modulator (3) which can control the far field deflection angle of the light beam by controlling the phase difference among the paths. The bent waveguide (4) adjusts the distribution of the light field energy in a far field by controlling the angle of the maximum value of the wave-guide-emitted light far field energy, so that the square of the amplitude sum of the light field of each waveguide far field does not change along with the angle, and the flat emission peak of the intensity is output at different deflection angles of the far field.
The relationship between the beam deflection angle of the optical phased array and the phase difference between adjacent waveguides is as follows:
d·sinθ=ΔΦ·λ/2π (1)
in the formula (1), d is the central interval of adjacent waveguides at the output port (5), theta is the included angle between the deflection direction of the light beam and the symmetry axis, delta phi is the phase difference between the adjacent waveguides at the output port (5), and lambda is the working wavelength.
The multistage 3dB power divider (2) can equally divide and output incident light power to 2 of the optical phased arraynA transmission waveguide path.
In order to dynamically control the beam deflection direction, a phase modulator (3) is placed on each transmission waveguide path of the optical phased array, and as shown in fig. 1, the phase modulator (3) is placed between the multi-stage 3dB power divider (2) and the curved waveguide (4). The expression for the phase change on the path is as follows:
in the formula (2), λ is the operating wavelength, Δ neffiI-th and i-1 th waveguide refractive index difference, L, caused by the phase modulator (3)iThe modulation length of the phase modulator of the ith waveguide.
The far field deflection angle of the light beam is determined by the phase difference delta phi between adjacent waveguides, and the maximum intensity value of a far field emission peak at a certain deflection angle is determined by the square curve of the sum of the far field optical field amplitudes of all the waveguides.
According to the principle of multi-beam interference, the far-field light intensity distribution is expressed as follows:
the angles theta of the far field light intensity maximum values corresponding to different phase differences delta phi are different and are determined by the formula (1); the light intensity at the deflection angle θ is expressed as follows:
in the formula (3), the reaction mixture is,
for complex amplitude of the ith waveguide at the output port (5), A in equations (3) and (4)
iAnd (alpha) is a function of the amplitude of the far field of the light emitted by the ith waveguide along with the change of the angle alpha, and delta phi is the phase difference between adjacent waveguides at the output port (5).
In order to prevent the far field intensity peak value of the on-chip optical phased array from changing along with the angle change, a bent waveguide (4) is arranged in a waveguide path, and the far field amplitude distribution A of an optical field is adjusted through the bent waveguide (4)i(θ), the angle at which the diffraction intensity peak is located is deviated from the symmetry axis.
Example (b):
taking 8 array elements as an example, adjusting the change curve A of the far field intensity of the emergent light of the single bent waveguide in the upper half area and the lower half area along with the anglei 2(α) is shown in FIGS. 2(a) and (b). The phase difference between array elements is changed, when the light beams have different deflection angles, the far-field emission peak changes along with the change of the light beam deflection angle as shown in fig. 3, and different curves from left to right sequentially correspond to the emission peaks when the phase difference is different. It can be seen from the figure that in the range of-31 deg., no grating lobes occur, and the difference of the maximum values of the emission peaks at different deflection angles is less than 0.05, realizing a waveguide beam deflector with flat output peak intensity.