CN100365471C - Optical phase array device - Google Patents
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- CN100365471C CN100365471C CNB2004100096301A CN200410009630A CN100365471C CN 100365471 C CN100365471 C CN 100365471C CN B2004100096301 A CNB2004100096301 A CN B2004100096301A CN 200410009630 A CN200410009630 A CN 200410009630A CN 100365471 C CN100365471 C CN 100365471C
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Abstract
The present invention discloses an optical phase array device which comprises a laser device, optical waveguides and a fixing bracket, wherein the fixing bracket is used for fixing the optical waveguides. Waveguide arrays are formed after the optical waveguides are fixed; a certain ploidy length differential of the inputting center wavelength is arranged between the adjacent optical waveguide in the waveguide arrays; the distance between the adjacent units of the optical waveguide arrays is unequal; the distance di between the adjacent units of the optical waveguide arrays and the ploidy length differential belta satisfy that di=K1*(lambda max-lambda min), belta I i= ki*lambda 0/n, wherein n is the effective refractive index of the optical waveguides; lambda 0 represents the wavelength of central light beams of the laser device; ki is natural number which is unequal in a certain range; lambda max represents the maximum wavelength of lasers, and the maximum wavelength can be continuously tuned; lambda min represents the minimum wavelength of the lasers, and the minimum wavelength can be continuously tuned. Compared with the bygone method, the present invention has the advantages of simple manufacturing method, no demand for a great amount of circuits and complex control, and unidimensional free scanning at any direction.
Description
Technical Field
The invention relates to an optical phased array.
Background
After the microwave phased array technology is released in the 20 th century and the 60 th era, the non-inertial electronic scanning of microwave radar beams is realized, the mechanical scanning era is distinguished, the microwave phased array technology becomes a major breakthrough in a radar system, and the problems of multi-target tracking and simultaneous scanning and tracking in a radar system are solved. In recent years, with the increasing popularity of laser radars, the optical wave phased array technology has become a research hotspot at present. The research significance of the laser radar is that the laser radar can be controlled optically or electrically in the beam direction, and can also be widely applied to the fields of optical communication, optical imaging and the like.
However, the current optical phased array device is still very immature because the wavelength of light in micron order is too short compared with the wavelength of microwave, so that the manufacturing process of the corresponding device is very difficult. The concept of an optical phased array was first verified in 1971 by Meyer using a lithium tantalate phase shifter to make a first one-dimensional optical phased array of 64 array elements (Meyer. R.a, appl.opt.ll, 613 (1972)). In 1973 Ninomiya also demonstrated one-dimensional optical phased arrays made of lithium niobate materials (Ninomiya. Y. Ieee. J. Quantum. Electron.9, 791 (1973)). Scientists made one-dimensional and two-dimensional optical phased array devices consisting of more cells from electro-optic crystalline materials such as liquid crystal (mcmamanon p.f., proc. Ieee84, 268 (1996)) and PLZT piezoelectric ceramics (p.j.talbot et al, opt. Memory Neural net.3, 111 (1994)) in sequence over 20 years later, and performed deflection experiments. The refractive index of the liquid crystal changes in direct proportion to the applied voltage and in inverse proportion to the thickness of the liquid crystal layer, so that the phase of the light wave can be changed by changing the applied voltage. The array phase shift unit made of liquid crystal has the advantages of low applied voltage (5V-10V) and easy operation, but has slow response speed (usually in the order of ms). PLZT is a transparent piezoelectric ceramic, and can produce electric double refraction effect under the action of applied voltage. The phase shift unit made of this material has the advantage of fast response speed (ns magnitude), and the disadvantages of high applied voltage (about 1 KV), difficult control and high cost. Another phased array fabrication technique employs an integrated optics approach (d.r. Bright et al, appl. Phys.lett.59, 899 (1991); f.vasey et al, appl.opt.32, 3220 (1993)), each phased unit consists of a waveguide, and the circuitry controlling this unit is also integrated on the same substrate, again subject to manufacturing limitations and at high cost. Figurel is a two-dimensional optical phased array device manufactured by Raynaud, the caliber size of the device is 4.3 multiplied by 4.1cm, the number of phased units is 43000, the deflection angle of a light beam is 5 degrees, and the pointing control precision reaches micro-rad magnitude.
The basic principle of the optical wave phased array technology is as follows: the light emitting units with equal phase difference can form an array, the light array with equal phase difference of each unit can generate light beam emission in a specified direction in spatial coherence, and the direction of the light beam can be controlled by controlling the phase difference between the light emitting units.
In the conventional theory, a phased array realizes beam forming, the optical waveguide length difference in the phased array is equal, and the pitch of array units is half wavelength. The laser wavelength is 1.55 μm and the half wavelength is 0.775 μm, which has very high requirement for the processing technology. The development steps of the optical wave phased array technology are also greatly limited. When the phased array spacing is greater than half a wavelength, two or more lobe maxima are oriented, i.e., side lobes occur. But only one lobe is required. There is currently no breakthrough in this study.
Disclosure of Invention
In view of the above problems and deficiencies of the conventional optical phased array, it is an object of the present invention to provide an optical phased array capable of adjusting the scanning angle of a light beam for practical use.
The invention is realized by the following steps: an optical phased array device comprises a laser, an optical waveguide and a fixing frame for fixing the optical waveguide, wherein the fixed optical waveguide forms a waveguide array, the length difference of a certain multiple of the wavelength of input central light exists between adjacent optical waveguides in the waveguide array, the adjacent unit intervals of the optical waveguide array are different from each other, and the adjacent unit interval d of the optical waveguide array is different from each other i And difference Δ l between adjacent optical waveguide lengths i It should be satisfied that,
Δl i ＝k i ·λ 0 n; wherein n is the effective refractive index of the optical waveguide, λ 0 Is expressed as the laser center beam wavelength, k i Are natural numbers, λ, unequal to each other within a certain range max Represents the maximum wavelength of light to which the laser can be continuously tuned; lambda [ alpha ] min Representing the minimum wavelength at which the laser can be continuously tuned.
Furthermore, the optical phased array system can also be integrated on one or more substrates by using an integration process, and can also be partially integrated on one or more substrates.
Furthermore, the unit interval d of the integrated optical waveguide array is adopted i Can be distributed between 5 μm and 500 μm.
Furthermore, if the optical waveguide array is made of various optical fibers, common optical waveguides, other optical wave transmission lines, or optical devices made by using the same principle, the unit spacing thereof can be made larger, such as d i At 50And the distribution is between the mu m and 5000 mu m.
Further, the number of the optical waveguide array units may be determined according to actual requirements, and if the required light beam is narrow, the number of the array units may be larger, and conversely, the number may be smaller. The number of array units in a common application is between 2 and 20 ten thousand.
Further, the laser may be a wavelength tunable laser, and the laser wavelength may also be changed by various methods such as externally modulating a common laser or various types of light sources.
Further, the optical waveguide array may be a one-dimensional array, or may be a two-dimensional or multi-dimensional array.
The invention adopts the structure that the space size of the array units is not limited, the spaces of the array units are all larger and are unequal, and the processing difficulty of the invention is greatly reduced. The invention can ensure that the side lobes between the optical waveguides can not be coherently superposed without influencing the use basically, and the main lobes can be coherently superposed, thereby obtaining larger amplitude of the main lobes and restraining the side lobes in a certain range. The invention controls the phase difference by changing the wavelength of light to achieve the purpose of controlling the direction of light beams. Compared with the prior art, the method of the invention is much simpler in manufacturing, does not need a large number of circuits and complex control, and can realize free scanning in any one-dimensional direction.
Drawings
The present invention will be described in detail below with reference to the accompanying drawings.
FIG. 1 is a schematic diagram of an implementation of the present invention;
FIG. 2 is a schematic diagram of the system of the present invention.
Detailed Description
The invention comprises a wavelength-tunable laser system and an optical waveguide array, wherein the wavelength-tunable laser system is connected with the optical waveguide array through an optical waveguide. The optical waveguide array may take the form of an integrated optical waveguide, i.e. the entire optical waveguide arrayThe columns are integrated on one or more substrates. The wavelength tunable laser system may employ any modulation method, for example, a structure of a common laser and an Acoustic Optical Modulator (AOM) may be employed, so that the wavelength of the laser is continuously tunable. As shown in fig. 1, which is a schematic diagram of an implementation of the present invention, a modulation signal enters an optical waveguide array after passing through an adjustable light source module, is compensated by a phase compensation circuit module, and is output by an optical beam expander, so that a coherent light spot on the right side of fig. 1 is obtained, and the non-inertial movement of the coherent light spot can be achieved by adjusting the wavelength of input light. In terms of the prior art, the optical waveguide array can ensure that the distance between optical waveguides is between several micrometers and dozens of even thousands of micrometers, the specific range of the array distance of the optical waveguide array of the invention is 5 micrometers to 5000 micrometers, and the array distance is the array distanceThe distance between the centers of two adjacent waveguides. If the optical waveguide array is integrated on one or several substrates, the integrated optical waveguides can be customized at a typical integrated optical device manufacturer. As shown in fig. 2, the phase forming network of the present invention clearly shows the distribution and length of the optical waveguides, and there is a difference in length between the optical waveguides, and there is a corresponding distance d between them. The right end of the system can form a coherent main lobe, and the wavelength of input light can be adjusted to enable the main light spot to scan up and down along a central line. Here, the pitches between the optical waveguides in the optical waveguide array may be different from each other, and of course, the pitches may also be equal. And the spacing d of adjacent optical waveguides i And its corresponding difference in length Δ l i The following conditions must be satisfied: if the spacing between adjacent optical waveguides
Where k is i Is a natural number within a certain range, λ max Represents the maximum wavelength at which the laser can be tuned; lambda min Represents the minimum wavelength at which the laser can be tuned; the length difference Δ l between the corresponding optical waveguides i ＝k i ·λ 0 N, where n is the effective refractive index of the optical waveguide,
the representation being laserThe center wavelength is also the wavelength at which the beam is not deflected. This is the most fundamental requirement for the fabrication of optical waveguide arrays. In the invention, the optical waveguide can be a common optical fiber or an integrated optical waveguide.
Here, the tunable laser may also be a DFB laser with a narrow line width, or a laser with various types of structures, and the wavelength of the laser is continuously tunable by adjusting the input current.
In microwave phased arrays, sidelobes are not a major problem. In optical phased arrays, where the wavelength of the antenna radiation is short, it is possible that two or more lobe maxima points may occur simultaneously after the spacing between the optical waveguides is not less than λ/2, and of these multiple maxima points only one is desired to be preserved and applied, the others are called side lobes. And, the cell pitch d i The larger the side lobe is, the more side lobes occur. This is a major problem that cannot be avoided. It can be said that for this reason, optical phased arrays have advanced little over the past 30 years. Controlling the spacing between fibers to about 0.775 μm is not only difficult to process, but also causes a number of other problems, such as crosstalk between the elements in the array, optical problems due to diffraction, power problems due to too small array elements, and diffraction angle limitations on the scan range.
The invention allows the existence of the side lobes but does not allow them to be coherently superposed, but allows the required main lobe to be coherently superposed, thus obtaining a larger amplitude of the main lobe and suppressing the side lobes within a certain range. The theoretical basis for the feasibility of the present invention is demonstrated in detail below.
The above problem can be solved more rigorously using fresnel diffraction integration. Let the laser light wave be λ 0 I.e. the corresponding beam is directed at 0 deg., and thus has
n·Δl 1 ＝k 1 ·λ 0 +d 1 sin0°
n·Δl 2 ＝k 2 ·λ 0 +d 2 sin0°
...
n·Δl N-1 ＝k N-1 ·λ 0 +d N-1 sin0°
When the laser light wave becomes λ, the following relationship holds:
n·Δl i ＝k i ·λ 0 +d i sin0°
＝k i ·λ+d i sinθ
＝k i ·λ+k i Δλ
wherein λ + Δ λ = λ 0 ，d i sin theta is space phase difference and satisfies d i sinθ＝k i Δ λ. If all d i And k i When the same proportional relation is satisfied, all array units generate extremely strong radiation in the theta direction when the wavelength is lambda.
k 1 Δλ＝d 1 sinθ
k 2 Δλ＝d 2 sinθ
...
k i Δλ＝d i sinθ
That is, all the array elements form coherent enhancement in the θ direction, and as long as the arrays no longer form coherent enhancement in other directions, it is ensured that the radiation field of the array is concentrated in one direction when the laser wavelength is λ.
Here again the side lobe problem is analyzed. For simplicity of explanation, consider the case of two adjacent array elements and assume that 10 λ ≦ d i < 11 λ, when the scanning laser wavelength is λ, the following is the case:
when k is i When Δ λ is an integral multiple of λ, there are
...
sinθ i11 ＝0
...
This means that if k is i With Δ λ being an integer multiple of λ, each array cell will produce 21 maximum angles. According to the above analysis, only θ = arcsin (k) i ·Δλ/d i ) The direction can be enhanced coherently, and the rest angles are different in the same direction due to different array units, so that the coherent enhancement can not be obtained. By continuously changing the input laser wavelength λ, the scanning angle θ can be changed, and inertia-free scanning can be achieved.
When k is i When Δ λ is not an integer multiple of λ, more specifically, assume 2 λ < k i Δ λ < 3 λ, then
Also at this time there are at least 20 maximum angles per array element. But only at θ = arcsin (k) i ·Δλ/d i ) Directional coherent enhancement can be obtained, and the rest angles are different in the same direction due to different array units, so that the coherent enhancement cannot be obtained.
Thus, when
Beam pointing of the present inventionθ satisfies the relationship:
the basic idea of the invention is to make the side lobes of each array unit not produce coherent superposition, but only each main lobe is coherently superposed. Therefore, the side lobes of each array element will appear as noise.
In addition, the optical waveguide array 2 of the present invention may also be in a non-integrated mode, i.e., the optical waveguides are manually fixed to the optical waveguide holder. Unlike integrated optical waveguides, the spacing between optical waveguides (the distance between optical centers) is relatively large, and is distributed between 50 μm and 5000 μm. Other conditions are unchanged, and the realization effect and the relevant conditions are the same as those of the integrated optical waveguide.
Claims (10)
1. An optical phased array device comprises a laser device, an optical waveguide and a fixing frame for fixing the optical waveguide, wherein the fixed optical waveguide forms a waveguide array, the length difference of multiple input light wavelengths exists between adjacent optical waveguides in the waveguide array, and the adjacent unit intervals of the optical waveguide array are mutually unequal i And difference Δ l between adjacent optical waveguide lengths i It should be satisfied that,
Δl i ＝k i ·λ 0 n; wherein n is the effective refractive index of the optical waveguide,
is the central wavelength, k, of the laser i Are natural numbers, λ, unequal to each other within a certain range max Represents the maximum wavelength at which the laser can be tuned; lambda [ alpha ] min Representing the minimum wavelength at which the laser can be tuned.
2. The optical phased array as claimed in claim 1, wherein the optical phased array is integrated or partially integrated on one or more substrates using integrated optics.
3. The optical phased array of claim 2, wherein said integrated optical waveguide array is used with a cell pitch d i Can be distributed between 5 μm and 500 μm.
4. The optical phased array as claimed in claim 1, wherein said optical waveguide array is made of optical fibers of various types, or other common optical waveguides, or other optical wave transmission lines, and has a unit pitch d i Can be distributed between 50 μm and 5000 μm.
5. The optical phased array as claimed in claim 3 or 4, wherein said distribution is either uniform or random.
6. The optical phased array of claim 1, wherein the number of optical waveguide array elements is between 2 and 20 ten thousand.
7. The optical phased array of claim 1, wherein the laser is a wavelength tunable laser.
8. The optical phased array as claimed in claim 7, wherein said tunable laser is a laser of various configurations or a combination of other types of light sources plus various modulators.
9. The optical phased array of claim 1, wherein the optical waveguide array is a one-dimensional array.
10. The optical phased array of claim 1, wherein the optical waveguide array is also a two-dimensional array, or a multi-dimensional array.
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| CNB2004100096301A CN100365471C (en) | 2004-09-30 | 2004-09-30 | Optical phase array device |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104865769B (en) * | 2015-05-11 | 2017-12-15 | 电子科技大学 | The method that the continuous two-dimensional deflection of optics coherence tomography light beam is realized based on optical phased array array |
| CN105527772A (en) * | 2015-12-29 | 2016-04-27 | 北京大学 | Optical phased array |
| EP3593206A4 (en) * | 2017-03-06 | 2020-11-25 | Shenzhen Genorivision Technology Co., Ltd. | A lidar light source |
| CN108693504A (en) * | 2017-06-09 | 2018-10-23 | 深圳市涵光半导体有限公司 | Phased-array laser transmitter unit and control method, laser radar |
| CN109782299B (en) * | 2019-02-14 | 2021-11-02 | 深圳市迈测科技股份有限公司 | Solid-state laser radar device |
| CN110221386A (en) * | 2019-06-11 | 2019-09-10 | 华东理工大学 | A kind of optical waveguide optical beam deflecting device and light beam deflection method |
| CN110658661B (en) * | 2019-08-30 | 2020-10-09 | 北京大学 | Phase calibration method and system for optical phased array |
| CN113985603B (en) * | 2021-12-22 | 2022-04-22 | 苏州旭创科技有限公司 | Light beam scanning system |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1182220A (en) * | 1997-11-05 | 1998-05-20 | 朱润枢 | Phased array optical equipment and method |
| US5793907A (en) * | 1996-03-28 | 1998-08-11 | The Regents Of The University Of California | Method and apparatus for a wavelength selective true-time delay for an optically controlled device |
| CN1294308A (en) * | 1999-10-28 | 2001-05-09 | 中国科学院长春光学精密机械研究所 | Phased-array light scan method for array of unequivalent microlenses arranged regularly |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5793907A (en) * | 1996-03-28 | 1998-08-11 | The Regents Of The University Of California | Method and apparatus for a wavelength selective true-time delay for an optically controlled device |
| CN1182220A (en) * | 1997-11-05 | 1998-05-20 | 朱润枢 | Phased array optical equipment and method |
| CN1294308A (en) * | 1999-10-28 | 2001-05-09 | 中国科学院长春光学精密机械研究所 | Phased-array light scan method for array of unequivalent microlenses arranged regularly |
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