MEMS-based modulation and beam control system, and method thereof.

Abstract

A MEMs-based variable blazed grating is provided for passive or active phase modulation and beam control, particularly in LIDAR. A system and method for modulating light employs a microelectromechanical structure having deformable diffractive elements. Light is directed at the diffractive elements, which act as plane mirrors to reflect the light. Each diffractive element is bent independently of the other diffractive elements by applying a predetermined electrostatic force corresponding to each diffractive element. Each diffractive element is bent continuously over a range of deflection positions or held stable at a single deflection position, and interferes with the light with a phase change imparted according to the laws of diffraction.

Description

Technical Field

[0001] (Cross-Reference to Related Application) This application claims priority and benefit from U.S. Provisional Patent Application No. 63 / 189,325, filed on May 17, 2021, entitled "MEMS-Based Variable Blazed Gratings for Passive or Active Phase Modulation and Beam Steering", the disclosure of which is hereby incorporated by reference herein in its entirety.

[0002] One or more embodiments generally relate to various optical-based microelectromechanical structure applications, and in particular, for example, to modulation and beam control systems based on microelectromechanical structures, and methods therefor.

Background Art

[0003] Light detection and ranging ("LIDAR") is a method of detecting an object in a field of view and calculating the distance to the object by emitting pulsed optical laser light and recording the exact time at which the pulses return. Reflections of each pulse are detected by a photodetector, and the exact time is recorded. The amount of delay between the emitted light and the returning light is used to calculate the distance from the object, which is called time-of-flight ("TOF") measurement. With sufficient information obtained by scanning one or more beams, it is possible to determine the movement and shape of an object. As such, LIDAR is widely used in atmospheric research, meteorology, geomorphology, surveying, cartography, space flight, military operations, autonomous vehicles, agriculture, forestry, archaeology, and other applications.

[0004] Conventional LiDAR systems typically include, as an architecture, one or more fixed or movable lasers, a scanner and optics including scanning or rotating mirrors, a photodetector, receiving electronics, and a navigation and positioning system. However, the need for so many components makes LiDAR systems large, resulting in high manufacturing and maintenance costs. To reduce the size and cost of conventional LiDAR systems, the use of microscopic electromechanical systems ("MEMS") for optical beam steering is considered a promising technology. MEMS refers to process technologies for creating integrated devices and systems that combine mechanical and electrical components. These are usually manufactured using integrated circuit processing technology and range in size from a few micrometers to millimeters.

[0005] First-generation MEMS devices consist of silicon-based scanning mirrors instead of laser-driving structures, but they operate at relatively low resonant frequencies and are therefore unable to accurately point to objects. Thus, they are considered "passive" systems. A more desirable system for monitoring rapidly changing situations is considered "active." That is, an active system can scan the angle of an object, similar to scanning with a scanning mirror, but it can also maintain the angle to investigate the object, evaluate distance and motion using time-of-flight information, and then restart scanning the entire field of view. Radar follows a similar pattern, initially replacing rotating antennas with passive phased array radars, and later with active phased array radars.

[0006] Small, robust, and high-speed MEMS devices are also effectively utilized in conventional structured optics applications. Structured optics processes project various known light patterns onto a landscape and capture light from the landscape by synchronizing the optical system with a camera system. This system uses information about how the patterns appear after being bent by the landscape to understand the three-dimensional shape. For simplicity, since the generation of structured optics using a diffractive modulator requires multiple moving light beams, beam steering may henceforth be referred to as a subsection of a single light beam that has been steering for structured optics applications.

[0007] Considerable effort has been made in the development of diffractive MEMS structures, particularly light bulbs, but many limitations remain regarding MEMS structures. The type of deformable ribbon device described in Bloom's U.S. Patent No. 8,970,827 has a ribbon with fixtures attached to both ends on a substrate. When a voltage is applied between the ribbon and the substrate, the voltage pulls the ribbon from its resting position into a downward U-shaped curve toward the substrate. By using multiple such ribbons and operating them with a variable operating depth, a linear phase gradient can be applied to the incident beam, and the beam angle can be swept from zeroth order to positive and negative first order. In this way, it is possible to create a passive scanning system that is more robust than geometric scanning mirrors and can achieve much higher scanning speeds than large MEMS scanning mirror systems.

[0008] The resonant velocity of a ribbon's vibration depends on the reciprocal of its length. For example, when using low-luminance light sources such as LEDs for cost reasons, a longer ribbon is desirable to increase optical throughput, but a shorter ribbon can achieve a faster oscillation velocity. This complexity also makes it difficult to design a system that provides the symmetry necessary to balance the spring restoring force that pulls the ribbon from the operating position to the resting position with the force required to operate the ribbon from the resting position. While the natural frequency of the ribbon may be improved by shortening the ribbon, this makes the device more sensitive to the alignment of incident light, reduces overall optical throughput, and increases the voltage required for operation. Alternatively, as described in U.S. Patent No. 8,947,509 by Bloom et al., the ribbon may consist of many short ribbons arranged in a line, but this comes at the expense of optical efficiency for speed. The ability to balance the operating speed and mechanical restoring speed is more important in periodic mode analog operations than in switching operations, because an imbalance in ribbon position control between electrostatic operation and its restoration can introduce optical aberrations.

[0009] In Bloom's devices and other devices that form binary diffraction gratings using ribbon structures, the ribbon is pulled down according to the classic 1 / 3 travel rule. After the ribbon has been pulled down by 1 / 3 of its travel distance, it snaps down when the attractive force of the electric field overcomes the restoring force. Therefore, analog control of the entire quarter wavelength requires a gap three times that of the same wavelength's digital on / off application. This necessitates a higher voltage requirement, and if the deflection stress at full operation is too high, an even longer span may be required. Designing highly deflected ribbons requires addressing design unforeseen circumstances by using devices such as Polychromix's Polychromato, which is designed as a switch or spectrometer and is also capable of beam steering. The required ribbon length for highly deflected ribbons, coupled with the relationship between ribbon length and speed, makes it difficult to fabricate beam steering ribbon gratings with complete analog control without sacrificing operating speed.

[0010] Ribbon-based binary diffraction gratings provide both positive and negative orders during diffraction, but exclude other orders, which is not a problem when used as a switch to turn the zero order on or off. On the other hand, blazed diffraction gratings are more efficient as a method of manipulating the beam. Fabricating blazed diffraction gratings based on ribbon-based architectures requires some compromises. Using mechanical stoppers, the ribbon can be tilted during touchdown operation to blaze the first row in a single-first order, but in the analog range, the blaze changes according to the twist of the ribbon. Some designs approximate the blaze angle by forming the ribbon in a stepped manner, but this is inefficient and difficult to implement in dynamic beam steering applications. [Overview of the project] [Means for solving the problem]

[0011] One or more embodiments relate in general to applications of micro-electromechanical structures for various light-based applications, and in particular to variable blazed diffraction gratings based on micro-electromechanical structures for passive or active phase modulation and beam control in photodetection, ranging, and other applications (e.g., tilt mirror arrays and / or elements that act to reflect light as planar mirrors).

[0012] According to one or more embodiments, a method for modulating one or more light beams using a minute electromechanical structure, The miniature electromechanical structure comprises a plurality of electrostatically deformable diffraction elements, each having a base and an elongated shape with long and short dimensions, and including a flexible reflective member that includes a supported portion and at least one unsupported portion. It comprises a substrate that supports one or more lower electrodes or functions as a lower electrode, The method includes the steps of directing light towards the diffracting element so that it functions as a planar mirror to reflect light, The process includes the step of applying a predetermined electrostatic force corresponding to a diffracting element so that the diffracting element bends independently of other diffracting elements, The diffracting element is configured to be continuously bent over a range of deflection positions or to be stably held at a single deflection position in order to form a desired lattice configuration.

[0013] In some embodiments, each diffraction element is bent about an axis parallel to the length of the reflective member, thereby changing the curvature of the reflective member and forming a desired diffraction grating configuration.

[0014] In some embodiments, the diffraction element is configured to be an asymmetric element having an inverted L-shaped cross-section. In other embodiments, the diffraction element is configured to be a symmetric element having a T-shaped cross-section.

[0015] In some embodiments, the reflective member is in electrical contact with the control voltage source. In some embodiments, when the control voltage is 0V, the reflective member is held in a stationary position.

[0016] In some embodiments, when a control voltage is applied such that it is greater than 0V (either positive or negative between electrodes) and increases in steps, the reflective member is able to move continuously across a range of bending positions in a predetermined pattern such that each step corresponds to each bending position within the range.

[0017] In some embodiments, when the control voltage is greater than 0V (either positive or negative between electrodes) and the reflective member corresponds to a single position, the reflective member is movable from a stationary position so as to be stably held at that single position.

[0018] According to one or more embodiments, a system for modulating one or more light beams using a miniature electromechanical structure, the system is Each comprises a base and a plurality of electrostatically deformable diffraction elements, each having an elongated shape with a long side and a short side, and including a flexible reflective member with a supported portion and at least one unsupported portion. A system for modulating one or more light beams using a minute electromechanical structure comprising a substrate that supports one or more lower electrodes or functions as a lower electrode, The diffracting elements are configured to reflect light as planar mirrors, and when a predetermined electrostatic force corresponding to each diffracting element is applied, they bend independently of the other diffracting elements. The system is characterized by being configured such that the diffractive element is continuously bent over a predetermined range of deflection positions or is stably held at a single deflection position so as to form a desired lattice configuration.

[0019] In some embodiments, the reflective member includes one or more layers of conductive material and one or more additional layers of material disposed on the conductive material to impart one or more optical or structural functions.

[0020] In some embodiments, the one or more layers comprise aluminum, gold, a refractory metal having a reflection-enhancing coating, a material for increasing light reflectance, or a combination thereof.

[0021] In some embodiments, the one or more lower electrodes comprise one or more layers of conductive material, and one or more layers of additional material disposed on the conductive material to impart one or more of an optical function, a structural function, or an electrical function.

[0022] In some embodiments, the one or more layers comprise aluminum, reflection-enhancing aluminum, silver, gold, a refractory metal, a doped semiconductor having a reflectivity-modifying coating, a dielectric barrier, or a combination thereof.

[0023] Additional aspects and advantages of the present disclosure will become apparent upon consideration of the following description. However, it should be understood that the detailed description and specific examples, while indicating various embodiments of the invention, are provided for illustrative purposes only, as various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

[0024] Embodiments of the present disclosure will now be described with reference to the accompanying schematic simplified drawings, which are not to scale. In the drawings: BRIEF DESCRIPTION OF THE DRAWINGS

[0025] [Figure 1A] Figure of a prior art L-shaped diffraction element comprising an elongated ribbon having a supported portion and an unsupported portion on a pedestal, in a non-energized (inactive) state. [Figure 1B] Figure of a prior art system comprising a plurality of the L-shaped diffraction elements of Figure 1A. The left side is set to an energized (diffraction) state, and the right side is set to a non-energized (inactive) state. [Figure 2] Scanning electron microscope (SEM) image of an L-shaped diffraction element in a non-energized (inactive) state. [Figure 3A]This figure shows a partial cross-sectional view of an embodiment of a system comprising multiple L-shaped diffractometers in a non-energized (non-operating) state. The total movable distance of the ribbon wings is indicated as "h," and the variable travel range of the analog that does not experience full operation or "snap-down" is represented as "a." [Figure 3B] This figure shows a cross-sectional view of the L-shaped diffraction element shown in Figure 3A when it is energized (operating). The ribbon wings are partially bent toward the electrodes or substrate. [Figure 3C] Figure 3B shows a cross-sectional view of the L-shaped diffraction element in an energized (operating) state. The ribbon wings are further bent toward the electrodes or substrate. [Figure 3D] Figure 3C shows a cross-sectional view of the L-shaped diffraction element in the energized (operating) state. The ribbon wings are fully bent toward the electrodes or substrate. [Figure 4] This figure shows a cross-sectional view of one embodiment of a system comprising a pair of adjacent L-shaped diffractometers whose deflection changes. [Figure 5] This diagram shows a T-shaped ribbon, intentionally curled by applying force, with its placement controlled by gradually increasing the force by a single bolt at a time, each half representing the deflection of an inverted L-shaped ribbon. The transition between the upper analog control range "a" and the snap-down state is clearly visible, as is the ability to hold any single deflection position. [Figure 6] This graph shows the response times for snap-down and snap-up, demonstrating a balanced electrical operation and mechanical restoring force that makes the optical performance of the strobe signal more symmetrical. [Figure 7] This is a cross-sectional view of a conventional system equipped with multiple T-shaped diffraction elements in both an unpowered (non-operating) state and an energized (operating) state. [Modes for carrying out the invention]

[0026] Before describing the present invention in further detail, it should be understood that the present invention is not limited to the specific embodiments described and can, of course, be modified. It should also be understood that the terms used herein are intended solely to describe specific embodiments and are not intended to limit the scope of the embodiments, as they are limited only by the appended claims.

[0027] Where a range of values ​​is provided, unless the context clearly indicates otherwise, each intervening value up to one-tenth of the lower limit unit between the upper and lower limits of that range, and any other stated or intervening values ​​within that stated range, should be understood to be included in this disclosure. The upper and lower limits of these smaller ranges may independently be included in smaller ranges and are also included in this disclosure, subject to any particularly excluded restrictions within the stated range. If a stated range includes one or both of the limit values, the range excluding one or both of those limit values ​​is also included in this disclosure.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this disclosure belongs. Any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of this disclosure, but only a limited number of exemplary methods and materials are described herein.

[0029] Note that, as used herein and in the appended claims, unless the context clearly indicates otherwise, the singular forms "a," "an," and "the" refer to multiple objects.

[0030] This disclosure relates in general to the use of microscopic electromechanical structures ("MEMs") for various optical-based applications, and in particular to the use of MEMs-based variable blazed diffraction gratings for passive or active phase modulation and beam control in light detection and ranging ("LIDAR") and other applications. Improved MEMs-based variable blazed diffraction gratings for use in LIDAR systems and structured optical applications are needed in the art to provide not only high-speed passive scanning, active scanning control, and robust construction, but also a large effective reflective area that significantly improves signal intensity. Brazing allows for more efficient use of the optical beam and reduces the diffraction order.

[0031] According to one or more embodiments, a method is provided for modulating one or more light beams using a miniature electromechanical structure, the method is Each comprises a base and a plurality of electrostatically deformable diffraction elements, each having an elongated shape with a long side and a short side, and including a flexible reflective member with a supported portion and at least one unsupported portion. A method for modulating one or more light beams using a minute electromechanical structure comprising a substrate that supports one or more lower electrodes or functions as a lower electrode, The steps include directing light towards the diffractive element so that it functions as a planar mirror to reflect light, The step includes applying a predetermined electrostatic force to each diffraction element so that each diffraction element bends independently of the other diffraction elements, The method is characterized by the fact that the diffractive element is continuously bent over a predetermined range of deflection positions or is stably held at a single deflection position so as to form a desired lattice configuration.

[0032] According to one or more embodiments, a system is provided for modulating one or more light beams using a miniature electromechanical structure, the system is Each comprises a base and a plurality of electrostatically deformable diffraction elements, each having an elongated shape with a long side and a short side, and including a flexible reflective member with a supported portion and at least one unsupported portion. A system for modulating one or more light beams using a minute electromechanical structure comprising a substrate that supports one or more lower electrodes or functions as a lower electrode, The diffracting elements are configured to reflect light as planar mirrors, and to bend independently of other diffracting elements when a predetermined electrostatic force corresponding to each diffracting element is applied, and further, The system is characterized in that the diffracting element is configured to be continuously bent over a predetermined range of deflection positions, or to be stably held at a single deflection position, so as to form a desired lattice configuration.

[0033] In developing this disclosure, it was found that MEMs-based structures including L-shaped or T-shaped diffraction elements may be suitable for use according to one or more embodiments. Details of manufacturing MEMs-based structures are well known to those skilled in the art and are described in detail, for example, in U.S. Patent No. 5,311,360 by Bloom et al. and U.S. Patent No. 5,661,592 by Bornstein et al. Such methods can be employed in manufacturing the MEMs-based structures of this disclosure.

[0034] Typical L-shaped diffractometers are described, for example, in U.S. Patent No. 8,848,278 by Pilossof, the entirety of which is incorporated herein by reference. Figure 1A shows a single L-shaped diffractometer 10 for clarity and simplicity. On the other hand, as shown in Figure 1B, the device 12 may include multiple L-shaped diffractometers 10 arranged to provide a linear array containing, for example, several hundred to several thousand diffractometers 10.

[0035] The L-shaped diffractometer 10 has an inverted L-shaped asymmetrical cross-section and is fabricated on a silicon or similar substrate 14. The L-shaped diffractometer 10 comprises a base 16 that vertically supports an elongated ribbon 18 along one side of the longitudinal axis. The ribbon 18 includes a fixed support portion 20 fixed to the base 16, a reflective mirror surface 22, and a movable, unsupported elongated portion that extends laterally along the base 16 and forms a single wing 24 that extends voluntarily. The wing 24 functions by a material that provides structural strength, dielectric properties to separate it from the lower electrode 26 located below the wing 24, and optical properties that allow several structural components to be present on its upper surface to contribute to the reflectivity of the mirror surface 22, but is shown in a simplified structure in the figure. The wing 24 has a length parallel to the base 16 and is formed to be significantly larger than its width in the direction across the base. The wing 24 is elastically deformable in the direction of the arrows forming an F(x) shape, based on the balance between the mechanical restoring force and electrostatic force applied during operation. F(x) may depend, for example, on the dimensions of the ribbon 18, the mechanical properties of the material forming the ribbon 18 (e.g., thickness and strength), and the applied voltage.

[0036] The reflective mirror surface 22 is provided on the upper surface of the ribbon 18 and may include one or more layers of conductive material, including, but not limited to, aluminum, gold, a heat-resistant metal with a reflection-enhancing coating, or other suitable materials for increasing optical reflectivity. For clarity, the reflective mirror surface 22 is shown as a single layer. In some embodiments, one or more layers of conductive material provide a function as an upper electrode. In some embodiments, but not limited to, one or more additional layers of such material may be added on the upper electrode to provide desired optical and structural functions, including changes in reflectivity.

[0037] In some embodiments, the substrate 14 may support one or more lower electrodes 26 on its surface, or it may function as a single lower electrode. In a configuration such as a single lower electrode, the substrate 14 may include, for example, a doped silicon wafer.

[0038] In some embodiments, one or more lower electrodes 26 are provided on the surface of a substrate 14 adjacent to the lower wing 24 and may include (but are not limited to) metal pads containing aluminum (or aluminum with increased reflectivity), silver, gold, a heat-resistant metal, or a doped semiconductor with a coating and / or dielectric barrier that alters reflectivity. In some embodiments, one or more additional layers of such material may be added to the lower electrodes to provide desired optical, structural, or electrical functions, such as a functional mirror contact layer or a dielectric insulating material that alters reflectivity, but is not limited to these.

[0039] Figure 1A shows the L-shaped diffraction element 10 in an unpowered (non-operating) state. In the unpowered (non-operating) state, no voltage is applied between the upper electrode 22 and the lower electrode 26, so the diffraction element 10 is in a "stationary" position. Depending on the embodiment, when in the stationary position it is relatively flat, and the wings 24 of the ribbon 18 are oriented substantially horizontally with respect to the substrate 14.

[0040] The base 16 functions like a hinge, requiring that the fixed support portion 20 of the ribbon 18 be flat and that the wings 24 of the ribbon 18 bendable. The base 16 extends in the longitudinal direction of the ribbon 18, thereby fixing the ribbon 18 in its longitudinal direction and at both ends, making it easier for the ribbon 18 to bend downward toward the lower electrode 26 when voltage is applied. The high speed of the device 12 may also be achieved by pinning the ends of the ribbon 18 to keep it taut and provide a high restoring force, and the fixing of the ribbon 18 along the longitudinal direction to the base 16 acts as a mechanical support that gives the ribbon 18 the ability to remain flat in the de-energized (non-operating) state. As used herein, the term “restoring force” refers to the force applied to transition the ribbon 18 from its energized (operating) state to its de-energized (non-operating) state.

[0041] In the energized (operating) state, a voltage is applied between the upper electrode 22 and the lower electrode 26 so that the diffraction element 10 takes on a "bent" position. When a voltage is applied between the upper electrode 22 and the lower electrode 26, an electrostatic field is established between them, resulting in an attractive force between them. This force pulls the wing 24 of the ribbon 18 toward the lower electrode 26 located below the wing 24, causing the wing 24 to bend toward the lower electrode 26 along its short axis, resulting in the position indicated by reference numeral 28.

[0042] Figure 1B shows a device 12 containing an L-shaped diffraction element 10 in an unenergized (non-operating) state and an L-shaped diffraction element 10 in an energized (operating) state. Device 12 consists of multiple L-shaped diffraction elements 10 arranged in parallel as shown in Figure 1A. The distance "d" between ribbons 118 and 218 (same as Λ in equation I) is the diffraction grating constant and determines the diffraction force of device 12. The gap "g" is the distance between adjacent ribbons 118 and 218. The ratio "d / g" is the fill factor and affects the overall efficiency of device 12. A higher fill factor may result in higher efficiency for device 12. The first pixel element 30 containing ribbon 118 is shown to be in an energized (operating) state with a voltage "V" applied, while the second pixel 32 containing ribbon 218 is in an unenergized (non-operating) state with no voltage applied ("V" = 0). Light 34a incident in the non-energized (non-operating) state is reflected in one direction 36 as a plane mirror, but light 34b incident in the energized (operating) state is directed in a different direction 38 according to the law of diffraction.

[0043] In Figure 1B, the unbent ribbon 118 has a voltage of 0V between the ribbon 118 and the electrode 26, while the bent ribbon 218 has a voltage applied to it, causing a snap-down and forming a diffraction grating that appears to spread in different directions 38. In this configuration, ribbons 118 and 218 are all switched by the same voltage to achieve the same F(x) for digital on and off. However, this method may not be suitable for applications where it is desirable to vary the deflection of a selected diffraction element 10 over a range of positions, or to stably maintain the deflection of a selected diffraction element 10 at a desired position other than a stationary position or a fully bent position.

[0044] This disclosure relates to the use of MEMS-based variable blazed diffraction gratings for passive or active phase modulation and beam control in LIDAR and other applications. In some embodiments, a method is provided for varying or vibrating the deflection of selected electrostatically deformable diffraction elements 10 over a range of positions. In this configuration, the deflection of each diffraction element 10 is varied over a range of positions to generate a phase shift of each diffraction element 10. In some embodiments, the phase shift of the diffraction elements 10 is used to steer a light beam. As used herein, the term “optical beam” refers to a light beam, and the light source is preferably from a laser or other suitable device such as an LED. In some embodiments, the light includes electromagnetic radiation of any frequency selected from ultraviolet, visible, or infrared light. In some embodiments, the light beam is continuously modulated by moving the diffraction elements 10 in a predetermined pattern in a “passive” scanning manner. In some embodiments, the predetermined pattern is a repeating pattern.

[0045] According to the embodiment, a method is provided for stably holding the deflection of a selected diffracting element 10 at a desired position. In some embodiments, the desired position is a position other than the stationary position or the fully deflected position. In some embodiments, the desired position includes one or more positions between the stationary position and the fully deflected position. In this configuration, the deflection of the diffracting element 10 is stably held at the desired position or a partial range of those positions in order to actively scan angles in a range smaller than the entire scannable range.

[0046] In the development of this disclosure, it was found that any desired deflection of the diffractive element 10 may be varied or vibrated throughout the range of positions, or held in a stable manner, at a desired position or a partial range of positions within the operating range of deflection by the corresponding voltage, as will be further described.

[0047] As shown in Figures 2 and 3A, the diffracting element 10 is in a de-energized (non-operating) state. In some embodiments, the stationary position is relatively flat, and the wings 24 of the ribbon 18 are oriented substantially horizontally with respect to the lower electrode 26. In some embodiments, the stationary position is curved, and the wings 24 of the ribbon 18 are facing upward. The stationary position may be modified according to the stress determined in the process of forming the diffracting element 10 to suit the desired operation. The total distance or total height over which the wings 24 of the ribbon 18 are movable is indicated as "h". The analog variable movement range that does not result in full operation or "snap-down" is indicated as "a". This is determined by the electrostatic laws governing the mechanical restoring force of the spring return force of the ribbon 18 and the balancing attractive force.

[0048] Figure 3B shows the diffracting element 10 in a "partially" energized state when the corresponding voltage is applied. The diffracting element 10 bends to an intermediate state between the unenergized (non-operating) state and the fully operated "snap-down" state. Thus, the wings 24 of the ribbon 18 bend to a position between the stationary position and the lower electrode 26, and the bend position (i.e., the plane of motion) is indicated as "Δz" or the distance from the stationary position (Figure 3C).

[0049] Figure 3C shows the L-shaped diffractometer of Figure 3B in an energized (operated) state when the corresponding voltage is applied, with the wings 24 of the ribbon 18 further bending toward the lower electrode 26.

[0050] Figure 3D shows the diffracting element 10 in a fully operational state, which has a “sloping” architecture in which the wings 24 of the ribbon 18 are positioned at the most extreme distance possible, with “Δz” equal to “h”. Under the conditions of applying the corresponding voltage, the wings 24 of the ribbon 18 bend further toward the lower electrode 26. As the voltage increases further, the electrostatic force due to the applied voltage reaches a point where it exceeds the restorative force due to the elasticity of the ribbon 18. This causes a snap-down, and the wings 24 of the ribbon 18 deform until they contact the lower electrode 26 or the substrate 14. When the voltage is released, the wings 24 of the ribbon 18 snap back to their original shape (i.e., the resting position shown in Figure 3A).

[0051] For clarity and simplification, a single L-shaped diffracting element 10 has been described above, but systems according to one or more embodiments are configured to include multiple L-shaped diffracting elements 10 arranged to provide a linear array containing, for example, several hundred to several thousand L-shaped diffracting elements 10. In this configuration, the ribbon 18 provides a reasonably large active optical region. In some embodiments, ribbons 18 having lengths up to approximately 2 mm have been tested and (although data are not shown) have been proven to provide such a large active optical region.

[0052] In some embodiments, the system comprises a plurality of adjacent L-shaped diffractometers 10. Figure 4 shows a pair of adjacent L-shaped diffractometers 10 with varying deflections. Each L-shaped diffractometer 10 is individually addressed by a corresponding different voltage applied to each L-shaped diffractometer 10. Each diffractometer 10 has its own F(x) based on the corresponding applied voltage, thereby exhibiting its own unique deflection. This configuration emulates a variable-pitch blazed diffraction grating and provides a desirable phase alignment pattern between zero-order reflections and orders diffracted by a fully operated array.

[0053] Ribbon 18 is mechanically resistant to deformation around its longitudinal axis. Without being constrained by theory, this can result in a higher natural frequency (i.e., resonant frequency). In some embodiments, the high natural frequency is greater than approximately 500 kHz. In some embodiments, the high natural frequency is greater than approximately 1.0 MHz. In some embodiments, the high natural frequency is greater than approximately 10.0 MHz. A higher natural frequency results in a faster response time.

[0054] Figure 5 shows various positions of a ribbon that has been intentionally stress-curled, controlled in 1-volt increments. A 1.4 MHz device was tuned for a wavelength of 830 nm, and the slope of operation from a flat time (i.e., the ribbon in a stationary position) and the slope of recovery from the operated state to the non-operated state were made the same. This device was fabricated using a mask layout that provides various lengths with the same width, "h" parameter, and fabrication material. The results are shown in Table 1 below.

[0055] Table 1 Relationship between resonant frequency and ribbon length

[0056] [Table 1]

[0057] While not bound by any particular theory, the provision of a consistent speed independent of ribbon length allows for more variations, including, but not limited to, wedge-shaped arrays for two-dimensional layouts diffracting in multiple directions. Figure 6 shows the snap-down and snap-up response times, demonstrating a balanced electrical operation and mechanical restoring force that allows for more symmetrical optical performance of the stroboscopic signal. In other experiments, the "h" value range for successful devices was approximately 200 nm to approximately 5.6 micrometers.

[0058] As used herein, the term “optical beam steering” refers to the passive or active steering of an optical beam over an angle θ, the maximum value of which is determined by the wavelength λ of the light used and the minimum diffraction grating subdivision pitch Λ, which is expressed by equation (I) below.

[0059]

number

[0060] Therefore, those skilled in the art may prefer to use only the range "a", the analog range, or the full range "h" for the total "Λz" value. Similarly, to fully utilize the phase shift of 2π, the total "Δz" range may be 1 / 4λ to 1λ or greater.

[0061] In some embodiments, passive steering is performed by vibrating the diffracting element 10 at a frequency below resonance in a path that changes within a deflection range, the pitch of which varies depending on the number of individual diffracting elements 10 that approximate a diffraction grating. The pattern can be predetermined and implemented by MEMS chips up to the limits of the driving electronics. In this configuration, one beam may be manipulated for LIDAR, or multiple beam movement sweeps may be fabricated for structured optical applications.

[0062] In some embodiments, active steering is performed by bending the ribbon 18 to different points between a non-operating state and a fully operating state. As used herein, the term “active” means that the light beam is intentionally directed to one or more target objects that may be present in the field of view, or that the light beam is intentionally directed by beamforming due to interference at a certain beam angle. The high restoring force of the ribbon 18 allows for rapid recovery from a fully operating state to a desired position, and the stability of the diffracting element 10 allows each ribbon 18 to maintain a desired phase or bend position for a relatively long time. In some embodiments, it took approximately 100 seconds to acquire the position of each ribbon at each 1-volt increment in Figure 5. The ability to maintain the diffraction state in each ribbon 18 and form a desired beam structure is useful in applications including active scanning applications and laser tuning, but is not limited to these.

[0063] Therefore, this disclosure can be used in a variety of applications, but is not limited to, beam steering and modulation (active or passive), structured photoforming, spectroscopy, optical tweezers, quantum communications, diffraction approximation of Fresnel lens / mirror segments, and laser tuning.

[0064] The above description merely refers to one embodiment of an L-shaped diffractometer for the sake of clarity and is not intended to limit it. Those skilled in the art will understand that modified L-shaped and T-shaped diffractometers are also suitable for use in this disclosure.

[0065] Typical modified L-shaped diffraction elements are described, for example, in U.S. Patent Application No. 16 / 985,110 by Fitzpatrick and Harley, the disclosure of which is incorporated herein by reference. In some embodiments, the modified L-shaped diffraction element does not require the entire base, and consequently the immovable and flat supported portion of the ribbon. The unsupported portion of the ribbon is the "hingeless" portion, which bends freely toward the substrate by electrostatic action, and thus can maintain a relatively flat state compared to the curve of the portion constrained to the base. Thus, the ribbon has a base-supported portion that acts as a functional hinge and a base-supported portion that has no base support and therefore functions as a mechanical influence on the unsupported portion that is not constrained by the base. The ribbon has sufficient thickness to obtain velocity by restoring force, but is also thin enough to bend downward toward the substrate by a complete hinge system. Thus, this configuration makes it possible to separate the thinness required for downward bending (i.e., making F(x) as straight as possible) from the sufficient thickness required for restoring force.

[0066] Typical T-shaped diffractometers are described, for example, in U.S. Patents 6,661,561, 6,836,352, and 6,856,448 by Fitzpatrick and Gelbart, the disclosures of which are incorporated herein by reference. Depending on the embodiment, the cross-section of each diffractometer may be symmetrical in a T-shape. As shown in Figure 7, the T-shaped diffractometer 40 has a symmetrical cross-sectional shape. The elongated reflective ribbon 318 is mounted on a base 316 along its central long axis and bends along its long axis, transitioning from a T-shaped non-energized (non-operating) state to an inverted V-shaped energized (operating) state. In the energized state, a sufficiently large voltage is applied between the electrodes 326, resulting in the ribbon 318 being deformed convexly with respect to a light beam (not shown), and the light from the light beam diverges as it is reflected by the reflective mirror surface 322 of the ribbon 318.

[0067] However, it will be apparent to those skilled in the art that many modifications are possible beyond those already described without departing from the inventive concept as set forth herein. Thus, the inventive subject matter is not limited beyond the scope of the disclosure. Furthermore, in interpreting this disclosure, all terms should be interpreted as broadly as possible in accordance with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to components, elements, or steps in a non-exclusive manner, indicating that the mentioned components, elements, or steps may exist, be utilized, or be combined with other components, elements, or steps not expressly mentioned. The reference that the working structure is a diffractive element does not preclude the geometric contribution of the working element shape to the resulting effect on the light incident on the element surface, but is made so due to the size scale of the element, which necessitates taking the laws of diffraction into account.

Claims

1. Each comprises a base and a plurality of electrostatically deformable diffraction elements, each having an elongated shape with a long side and a short side, and including a flexible reflective member with a supported portion and at least one unsupported portion. A method for modulating one or more light beams using a minute electromechanical structure comprising a substrate that supports one or more lower electrodes or functions as a lower electrode, Each reflective member is electrically in contact with the power supply of the corresponding control voltage, which is the voltage between the reflective member and the corresponding lower electrode. The aforementioned method, The steps include directing light towards the diffracting element so that it functions as a planar mirror to reflect light, The step includes applying a predetermined electrostatic force to each diffraction element so that each diffraction element bends independently of the other diffraction elements, Each reflective member is continuously bent in a predetermined pattern over a predetermined range of the deflection position, such that when the control voltage is applied in steps, each step corresponds to each deflection position within the predetermined range. A method in which at least one of the following is true: (a) at least one pair of adjacent diffraction elements has a varying deflection so as to provide a phase adjustment pattern that emulates a variable-pitch blazed diffraction grating; and (b) a plurality of individual diffraction elements that collectively approximate a single diffraction grating period vary so as to change the effective diffraction grating pitch Λ, thereby changing the beam steering angle θ of the modulated light.

2. The method according to claim 1, wherein each diffracting element bends about an axis parallel to the long side of the reflecting member, thereby changing the curvature of the reflecting member, to form a desired diffraction grating configuration, and in active steering, one or more light beams are directed towards one or more target objects.

3. The method according to claim 2, wherein the diffraction element is configured to be asymmetrical with an inverted L-shaped cross-section, and the applying step includes applying a predetermined electrostatic force to each diffraction element such that each diffraction element is held in its respective deflected position at each time.

4. The method according to claim 2, wherein (a) is true, the diffracting element is configured to be symmetrical and have a T-shaped cross-section, and the applying step includes applying a predetermined identical electrostatic force to each diffracting element.

5. The method according to claim 2, wherein (b) is true and each reflecting member has a resonant frequency greater than 500 kHz.

6. The method according to claim 5, wherein (b) is true in passive steering, and the reflecting member is operable to bend continuously in passive steering at frequencies below the resonant frequency.

7. The method according to claim 2, wherein (a) and (b) are true, and the light is ultraviolet light, visible light, or infrared light.

8. The method according to claim 6, wherein when the control voltage is greater than 0V and the reflecting member corresponds to a single position, the reflecting member is movable from a stationary position so as to be stably held at the single position.

9. A system for modulating one or more light beams, including a miniature electromechanical structure, The aforementioned miniature electromechanical structure is Each comprises a base and a plurality of electrostatically deformable diffraction elements, each having an elongated shape with a long side and a short side, and including a flexible reflective member with a supported portion and at least one unsupported portion. It comprises a substrate that supports one or more lower electrodes or functions as a lower electrode, Each reflective member is electrically in contact with the power supply of the corresponding control voltage, which is the voltage between the reflective member and the corresponding lower electrode. The diffracting elements are configured to reflect light as planar mirrors, and to bend independently of other diffracting elements when a predetermined electrostatic force corresponding to each diffracting element is applied, and further, Each diffracting element is selectively operable to form a desired grid configuration, either by being continuously bent in a predetermined pattern over a predetermined range of the deflection positions, or by being stably held at a single deflection position, when the control voltage is applied in a stepwise increasing manner, such that each step corresponds to each deflection position within the predetermined range. A system in which at least one of the following is true: (a) at least one pair of adjacent diffraction elements has a varying deflection so as to provide a phase adjustment pattern that emulates a variable-pitch blazed diffraction grating; and (b) a plurality of individual diffraction elements that collectively approximate a single diffraction grating period vary so as to change the effective diffraction grating pitch Λ, thereby changing the beam steering angle θ of the modulated light.

10. The system according to claim 9, wherein the diffraction element is configured to be asymmetrical with an inverted L-shaped cross-section, and in a configuration of the minute electromechanical structure, each of the diffraction elements is configured to be subjected to a predetermined identical electrostatic force and thereby bend when the predetermined identical electrostatic force is applied.

11. The system according to claim 9, wherein the diffraction element is configured to be symmetrical and have a T-shaped cross-section.

12. Each diffraction element bends about an axis parallel to the long side of the reflecting member, thereby changing the curvature of the reflecting member and forming a desired diffraction grating configuration. The system according to claim 9, wherein the system is operable to perform active steering to direct the one or more light beams toward one or more target objects.

13. The system according to claim 9, wherein (a) is true and each reflecting member has a resonant frequency greater than 500 kHz.

14. The system according to claim 13, wherein (b) is true in passive steering, and the reflecting member is operable to bend continuously in passive steering at frequencies below the resonant frequency.

15. The system according to claim 9, wherein (a) and (b) are true, and the light is ultraviolet light, visible light, or infrared light.

16. The system according to claim 14, wherein when the control voltage is greater than 0V and the reflecting member corresponds to a single position, the reflecting member is movable from a stationary position so as to be stably held at the single position.

17. The reflective member comprises one or more layers of conductive material, The system according to claim 9, further comprising one or more layers of additional material disposed on the conductive material to impart one or more optical or structural functions.

18. The one or more layers of the conductive material include aluminum, gold, a heat-resistant metal having a reflective-enhancing coating, a material for increasing light reflectivity, or a combination thereof. The system according to claim 17, wherein each reflecting member has a co-occurring frequency greater than 1 MHz.

19. The one or more lower electrodes comprises one or more layers of conductive material, The system according to claim 9, further comprising one or more layers of additional material disposed on the conductive material to impart one or more of the optical, structural, or electrical functions.

20. The system according to claim 19, wherein the one or more layers of the conductive material include aluminum, reflective-enhanced aluminum, silver, gold, a heat-resistant metal, a doped semiconductor having a reflectivity-changing coating, a dielectric barrier, or a combination thereof.

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