Phased array beam steering for materials processing.

Abstract

To provide a beam steering system that can direct a high repetition rate laser pulse at a high positioning bandwidth.SOLUTION: A system includes: a multi-channel beam splitter arranged and configured to split an input optical signal into a plurality of split optical signals; a plurality of phase modulators, each phase modulator of the plurality of phase modulators capable of modifying the phase of a corresponding split optical signal of the plurality of split optical signals in response to a control signal; a waveguide arranged at an optical output of the plurality of phase modulators, the waveguide configured to spatially rearrange the split optical signals output from the plurality of phase modulators into a pattern, thereby producing an optical signal pattern; and an optical amplifier arranged at an optical output of the waveguide, the optical amplifier configured to amplify the optical signal pattern produced by the waveguide.SELECTED DRAWING: Figure 1

Description

Related Applications

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 808,742, filed February 21, 2019, and U.S. Provisional Patent Application No. 62 / 823,454, filed March 25, 2019, which are incorporated by reference in their entireties.

[0002] I.Technical field SUMMARY OF THE INVENTION The embodiments described herein generally relate to systems and methods for phased array beam steering of laser energy.

[0003] II.Technical background Many processes in the field of laser micromachining require pulses that are completely spatially separated from adjacent pulses (at the workpiece). Spatial overlap of these pulses can result in various adverse effects, such as localized heat accumulation. This localized heat accumulation negates the benefits of "athermal ablation" via ultrafast lasers or pulse-plume interactions. Today's state-of-the-art lasers provide high-power pulses at high repetition rates (i.e., 1 MHz to 100 MHz and higher). To efficiently utilize such lasers, it may be desirable to employ a beam steering system with a suitably high positioning bandwidth. For example, acousto-optic deflectors (AODs) offer a positioning bandwidth that is more than three orders of magnitude higher than that of galvos (<2.5 kHz for galvos vs. <1 MHz for AODs). High-speed beam steering enabled by polygon mirrors has received much attention as one solution that allows scaling of laser repetition rates much higher than 1 MHz while still providing perfect spot separation, but its adoption is limited to a set of "high fill factor" problems. As laser-based material processing continues to develop to enable the creation of finer and more precise features, a beam steering system capable of delivering high repetition rate laser pulses with a higher positioning bandwidth than is achievable with AODs and polygon mirrors will ultimately be required.

[0004] One embodiment of the present invention may be broadly characterized as a system comprising: a multi-channel beam splitter arranged and configured to split a first input optical signal into a plurality of first split optical signals; a plurality of phase modulators, each phase modulator capable of modifying the phase of a corresponding one of the plurality of first split optical signals in response to a control signal; waveguides arranged at optical outputs of the plurality of phase modulators, the waveguides configured to generate a first optical signal pattern by spatially reordering the first split optical signals output from the plurality of phase modulators into a pattern; and an optical amplifier arranged at the optical output of the waveguides, the optical amplifier configured to amplify the first optical signal pattern generated by the waveguides.

[0005] Another embodiment of the present invention can be broadly characterized as a system capable of converting the first wavelength of the laser beam to a second wavelength, comprising a beam positioning system capable of deflecting a laser beam having a first wavelength, a lens positioned within a beam path through which the laser beam can propagate after deflection by the beam positioning system, and a harmonic conversion module positioned within the beam path through which the laser beam can propagate after passing through the lens, wherein the harmonic conversion module is capable of converting the first wavelength of the laser beam to a second wavelength. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 shows a schematic diagram of a phased array beam steering system according to one embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating a photonic integrated circuit in the phased array beam steering system shown in FIG. 1 in accordance with one embodiment of the present invention. [Figure 3] FIG. 3 illustrates a schematic diagram of a phased array beam steering system according to another embodiment of the present invention. [Figure 4]FIG. 4 is a schematic diagram illustrating a photonic integrated circuit in the phased array beam steering system shown in FIG. 3 in accordance with one embodiment of the present invention. [Figure 5-6] 5 and 6 show schematic diagrams of different embodiments for achieving post-steered wavelength conversion of laser energy. Detailed Description

[0007] Examples of embodiments will now be described with reference to the accompanying drawings. Unless explicitly stated, in the drawings, the sizes, positions, etc. of components, features, elements, etc., and the distances therebetween, are not necessarily to scale and have been exaggerated for clarity. Like numbers refer to like elements throughout the drawings. Thus, the same or similar numbers may be described with reference to other drawings even if they are not mentioned or described in the corresponding drawings. Also, elements without reference numbers may be described with reference to other drawings.

[0008] The terminology used in the specification is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. As used herein, the singular is intended to include the plural unless the content clearly dictates otherwise. Furthermore, it should be understood that the terms "comprises" and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise indicated, when a range of values ​​is recited, the range includes the upper and lower limits, as well as any subranges between the upper and lower limits of the range. Unless otherwise indicated, terms such as "first" and "second" are used merely to distinguish elements from one another. For example, one node can be referred to as a "first node," and similarly, another node can be referred to as a "second node," or vice versa.

[0009] Unless otherwise indicated, "about," "around," and the like mean that amounts, sizes, compositions, parameters, and other quantities and characteristics are not, and need not be, exact, but may be approximate and / or larger or smaller, as appropriate, or to reflect tolerances, conversion factors, rounding, measurement error, and the like, as well as other factors known to those skilled in the art. Spatially relative terms such as "below," "down," "lower," "upper," and "upper" may be used herein for ease of description when describing the relationship of an element or feature to another element or feature, as shown in the figures. It should be understood that spatially relative terms are intended to encompass different orientations in addition to those depicted in the figures. For example, an element described as being "below" or "below" another element or feature would be oriented "above" that other element or feature if the object in the figure were inverted. Thus, the exemplary term "below" can encompass both an orientation of above and below. If the object is oriented in other ways (e.g., rotated 90 degrees or at other orientations), the spatially relative descriptors used herein may be interpreted accordingly.

[0010] The section headings used herein, unless specifically stated, are for organizational purposes only and should not be construed as limiting the subject matter described. It will be understood that many different forms, embodiments, and combinations are possible without departing from the spirit and teachings of the present disclosure, and that the present disclosure should not be construed as limited to the example embodiments set forth herein. Rather, these examples and embodiments are provided so that this disclosure will be complete and all-inclusive, and will fully convey the scope of the disclosure to those skilled in the art.

[0011] Embodiments generally relating to PIC phased array beam steering Referring to FIG. 1, a phased array beam steering system 100 includes a photonic integrated circuit (PIC) 102, an optical amplifier 104, a feedback system 106, and control electronics 108.

[0012] In the illustrated embodiment, the PIC 102 may be optically coupled to the output of the seed laser 110. In other embodiments, the seed laser 110 may be integrated as part of the PIC 102. In one embodiment, the seed laser 110 is a frequency-stabilized laser diode with a wavelength greater than 0.9 μm (e.g., at or about 1 μm, at or about 1.03 μm, at or about 1.06 μm, at or about 1.1 μm, or any wavelength greater than 1.1 μm). It will be appreciated that other wavelengths in the near infrared may be output by the seed laser 110.

[0013] The seed laser 110 may output laser pulses at a pulse repetition rate ranging from 5 kHz to 50 GHz, although it will be appreciated that the pulse repetition rate may be less than 5 kHz or greater than 50 GHz. In this manner, laser pulses may be output by the seed laser 110 at pulse repetition rates less than, greater than, or equal to 5 kHz, 50 kHz, 100 kHz, 175 kHz, 225 kHz, 250 kHz, 275 kHz, 500 kHz, 800 kHz, 900 kHz, 1 MHz, 1.5 MHz, 1.8 MHz, 1.9 MHz, 2 MHz, 2.5 MHz, 3 MHz, 4 MHz, 5 MHz, 10 MHz, 20 MHz, 50 MHz, 60 MHz, 100 MHz, 150 MHz, 200 MHz, 250 MHz, 300 MHz, 350 MHz, 500 MHz, 550 MHz, 600 MHz, 900 MHz, 2 GHz, 10 GHz, 20 GHz, 50 GHz, 75 GHz, etc., or values ​​between any of these values. The seed laser 110 can output laser pulses having a pulse width or duration (based on the full width at half maximum (FWHM) of the optical power with respect to time) ranging from 20 fs to 900 ms, although it will be understood that the pulse duration can be shorter than 20 fs or longer than 900 ms.In this manner, the at least one laser pulse output by the seed laser 110 may be 10 fs, 15 fs, 30 fs, 50 fs, 100 fs, 150 fs, 200 fs, 300 fs, 500 fs, 600 fs, 750 fs, 800 fs, 850 fs, 900 fs, 950 fs, 1 ps, 2 ps, 3 ps, 4 ps, 5 ps, 7 ps, 10 ps, ​​15 ps, 25 ps, 50 ps, ​​75 ps, 100 ps, ​​200 ps, ​​500 ps, ​​1 ns, 1.5 ns, 2 ns, 5 ns, 10 ns, 20 n The seed laser 110 may have a pulse duration shorter than, longer than, or equal to 1 s, 50 ns, 100 ns, 200 ns, 400 ns, 800 ns, 1000 ns, 2 μs, 5 μs, 10 μs, 15 μs, 20 μs, 25 μs, 30 μs, 40 μs, 50 μs, 100 μs, 300 μs, 500 μs, 900 μs, 1 ms, 2 ms, 5 ms, 10 ms, 20 ms, 50 ms, 100 ms, 300 ms, 500 ms, 900 ms, 1 s, etc., or a value between any of these values. Alternatively, the seed laser 110 may output a continuous wave (CW) or quasi-CW (QCW) laser energy beam.

[0014] 2 , the PIC 102 includes an amplitude modulator 200, a multi-channel beam splitter 202, a phase modulator array 204, and a three-dimensional waveguide 206. That is, the amplitude modulator 200, the multi-channel beam splitter 202, the phase modulator array 204, and the three-dimensional waveguide 206 are integrated into a common photonic integrated circuit 102. However, in other embodiments, only two or three of these components are integrated into the common photonic integrated circuit 102, with the remaining components being formed separately and optically coupled to either the optical input or optical output of the photonic integrated circuit 102. For example, only the phase modulator array 204 and one or both of the multi-channel beam splitter 202 and the three-dimensional waveguide 206 may be integrated into the common photonic integrated circuit 102.

[0015] Referring to the embodiment shown in FIG. 2 , the output of the seed laser 110 (also referred to herein as the “seed signal”) is amplitude modulated through an amplitude modulator 200 (e.g., a Mach-Zehnder modulator) in response to one or more control signals output by the control electronics 108. Amplitude modulation may be performed as needed to flatten the output amplitude depending on the orientation / position after the optical amplifier (see, e.g., FIG. 9 of U.S. Pat. No. 9,776,277, which is incorporated herein by reference in its entirety) or to provide amplitude modulation required by the process or system. The seed signal then passes through a multi-channel beam splitter 202, which is configured to generate multiple “split seed signals” by splitting the seed signal into multiple channels. In one embodiment, multi-channel beam splitter 202 includes a sufficient number of 1x2 optical beam splitters to reach the desired number of channels (e.g., a 256-channel system for a rectangular 16x16 array would require eight splitting cascades containing a total of 255 1x2 splitter elements). In other embodiments, multi-channel beam splitter 202 may be a star splitter or a cascading number of star splitters. In one embodiment, the desired number of channels may be 32, 50, 64, 90, 100, 128, 150, 200, 256, 300, 350, 512, 800, 1024, 1500, 2000, 2500, etc., or any value between these values.

[0016] The split seed signals are then introduced into the phase modulator array 204. In this case, the phase modulator array 204 includes a plurality of phase modulators, each of which is arranged to receive one of the split seed signals generated by the multi-channel beam splitter 202 (i.e., one phase modulator for one split seed signal). Furthermore, each phase modulator can maintain or modify the phase of its respective split seed signal based on one or more control signals output by the control electronics 108. The phase modulators in the phase modulator array 204 may be implemented in any suitable or desired manner. For example, each phase modulator may be a Mach-Zehnder Modulator (MZM). If each phase modulator is implemented suitably (e.g., as an MZM), each phase modulator can be operated to maintain or modify the amplitude of its respective split seed signal input to the phase modulator (e.g., based on one or more control signals output by the control electronics 108).

[0017] The phase-modulated signals are then sorted into a dense pattern (e.g., hexagonal, rectangular, etc.) via a three-dimensional waveguide 206. Thus, the output of each phase modulator in the phase modulator array 204 is optically coupled to the optical input of the three-dimensional waveguide 206, which can be characterized as providing a "tiled" arrangement of multiple individual optical emitters. The three-dimensional waveguide 206 may be part of the PIC as shown, or it may be a separate component from the PIC. A PIC 102 with some of these properties is demonstrated and reported in Poulton, Christopher V. et al., "Large-scale visible and infrared optical phased arrays in silicon nitride," Conference on Lasers and Electro-Optics (CLEO), IEEE, 2017, which is understood to demonstrate the successful integration of a subsequent antenna array into a 10-way cascaded 1024 deep-trench channel chip. However, the beam steering mechanism used in this paper is based on wavelength sweeping, not phase modulation.

[0018] High-reliability PICs 102 with integrated arrays of over 500 phase modulators are currently being developed for automotive LIDAR applications. However, the typical wavelength of these arrays is in the eye-safe 1.5 μm band. Nevertheless, such PICs can be adapted to operate at wavelengths ranging from 0.9 μm (or thereabouts) to 1.1 μm (or thereabouts) by suitably modifying the materials forming the PIC components. See, for example, U.S. Patent Nos. 8,213,751 and 9,612,398; U.S. Patent Application Publication No. 20180180811; Munoz, Pascual et al., "Silicon Nitride Photonic Integration Platforms for Visible, Near-Infrared and Mid-Infrared Applications," Sensors, 17, 2088 (2017); and Rahim, Abdul et al., "Expanding the Silicon Photonics Portfolio with Silicon Nitride Photonic Integrated Circuits," Journal of Lightwave Technology, Vol. 35, No. 4, February 15, 2017, all of which are incorporated by reference in their entirety. In one embodiment, the phase modulator integrated within the PIC102 has a high bandwidth greater than 1 MHz (e.g., greater than 1 GHz).

[0019] In one embodiment, the optical amplifier 104 includes a multimode fiber gain module (e.g., multiple multimode fiber gain modules connected in series to achieve higher average power and peak power), one or more multicore fiber amplifiers, or any combination thereof. If the optical amplifier 104 includes a multimode fiber gain module, the multimode fiber gain module is selected so that the number of supported propagation modes of the fiber gain module approximately matches the number of channels in the pattern generated at the optical output of the three-dimensional waveguide 206. This allows for effective control of the output mode of the multimode fiber gain module. If the optical amplifier 104 includes a multicore fiber amplifier, the multicore fiber amplifier is selected so that the number and arrangement of cores in the multicore fiber amplifier approximately matches the number and arrangement of channels in the pattern generated at the optical output of the three-dimensional waveguide 206. Light from the PIC 102 is either directly coupled into the optical amplifier 104 or imaged to the optical amplifier 104. As shown in Florentin, Raphael et al., "Shaping the light amplified in a multimode fiber," Light: Science & Applications 6.2 (2017): e16208, mode control is possible not only in passive fibers but also in multimode gain fibers. In one embodiment, unlike the Florentin et al. paper, the output mode of a multimode fiber is a supermode that fills much of the multimode fiber core, and its spatial phase can be modulated for steering / shaping in the Fourier plane after a collimating lens (i.e., lens 112 shown in FIG. 1). The optical amplifier output is collimated by lens 112, and a small portion of it is directed (e.g., via beam splitter 114 followed by lens 116) to a photodetector 118 (e.g., a high-speed photodiode). The main power of the amplified output from optical amplifier 104 (i.e., the portion of the beam not directed to photodetector 118) is referred to herein as the "process beam" described above.

[0020] The signal output by the photodetector 118 (in response to detecting light transmitted through the lens 116) may be analyzed (e.g., by the control electronics 108) using the LOCSET technique (although other techniques are possible) to obtain a control signal that is ultimately sent to the phase modulator array 204. Generally, as the control signal acts on the phase modulator array 204, the control signal is adapted to stabilize the phase of the optical signal output from the optical amplifier 104 to obtain a desired mode shape, steering, and position at the output of the optical amplifier 104 (e.g., based on one or more predetermined requirements associated with desired phase drift, processing system geometry, and positioning requirements). In one embodiment, the number of channels controllable using the LOCSET technique is believed to be up to or around 1000 (e.g., slightly less than or slightly more than 1000).

[0021] The primary power output of the optical amplifier 104 (i.e., the "process beam" discussed above) may be relayed to a beam positioning system (not shown) by any method known in the art, if desired. Optionally, the process beam may be directed to a harmonic conversion module 120, and the optical output of the harmonic conversion module 120 may then be relayed to the beam positioning system (not shown) by any method known in the art. The process beam is typically directed from the beam positioning system onto a workpiece (not shown) to process (e.g., crack, damage, melt, vaporize, ablate, foam, mark, etc.) the workpiece by any method known in the art.

[0022] In one embodiment, the control electronics 108 can output control signals to the phase modulators in the phase modulator array 204 to beam steer (e.g., along one or more axes, in any desired direction) or beam shape the process beam ultimately output by the phased array beam steering system 100 in any suitable or desired manner, or to beam shape the process beam, or any combination thereof. As used herein, "beam shaping" refers to changing the size or shape of the process beam generated by the phased array beam steering system 100. The shape of the process beam refers to the spatial distribution or spatial profile of the optical intensity of the process beam measured in a plane orthogonal to the beam axis of the process beam. Thus, the process beam can include a single "beam" or multiple spatially separated "beamlets." As used herein, the size of a "beam" or "beamlet" refers to a size where the optical intensity from the beam axis is at least 1 / e of the optical intensity in the propagation axis of the beam or beamlet. 2 The term "width" refers to the maximum or average width of a beam or beamlet measured as the radial or lateral distance to a point where the beam or beamlet falls below the maximum width. Within the pattern resolution achievable by the three-dimensional waveguide, the phased array beam steering system enables the generation of beams (or beamlets) having any shape (e.g., flat-top, Gaussian, Hermite-Gaussian, Laguerre-Gaussian, Bessel, quasi-Bessel, circular-annular, square-annular, etc., or any combination thereof). As can be appreciated, the process beam can be formed to have any shape or size when steering the process beam, and the phased array beam steering system 100 can be operated to change or maintain the shape and / or size of the process beam when steering the process beam.

[0023] Harmonic conversion module 120 may include a second harmonic generation (SHG) medium, a third harmonic generation (THG) medium, etc., or any combination thereof, as is known in the art. It will be appreciated that the wavelength of the light output by harmonic conversion module 120 will depend on the medium (e.g., SHG medium, THG medium, etc.) forming the harmonic conversion module and the wavelength of the light input to the harmonic conversion module (e.g., output by a multimode fiber gain module). Thus, if the wavelength of the light input to harmonic conversion module 120 is in the near-IR region (as described above), the wavelength of the light output from harmonic conversion module 120 may generally be characterized as being in the visible green region of the electromagnetic spectrum or the ultraviolet region of the electromagnetic spectrum.

[0024] Typically, the beam positioning system is a high bandwidth beam positioning system (i.e., having a bandwidth greater than 1 kHz) such as an AOD, an electro-optic deflector (EOD), a galvanometer mirror scanner, a rotating polygon mirror scanner, or the like, or any combination thereof.

[0025] Further embodiments As mentioned above, embodiments of the present invention can be adapted to combine (coherently or otherwise) the outputs of optical amplifiers so as to steer or shape process beams with bandwidths up to GHz. Thus, unlike conventional coherent beam combining (i.e., beams spatially overlap via dendritic thin film polarizers, diffractive optics, etc.), embodiments described herein can be adapted to "tile" the outputs of individual emitters while still establishing stable and controllable phase relationships among the individual optical signals.

[0026] 1 above is operable in pulsed mode over a very wide range of pulse widths and repetition rates. Accordingly, the seed laser 110 is operable to generate a seed signal comprising a plurality of optical pulses having a wide range of pulse widths (e.g., from tens of nanoseconds to several picoseconds) and repetition rates (e.g., from 100 kHz to 50 GHz). As noted above, the phase of the signal output from the phase modulator array 204 is controlled by the LOCSET method, which is well suited to coherent combining of a large number of channels, even in a "tiled" output configuration.

[0027] Unfortunately, however, the LOCSET method is not easily compatible with optical pulses as input. Therefore, in one embodiment, unlike the embodiment shown in FIG. 1 , where the process beam is represented as a train of pulses, the process beam is not used for phase locking. Rather, the phased array beam steering system 100 can be modified to process a second laser beam (also referred to herein as the “reference beam” or “probe beam”) in addition to the seed signal (also referred to herein as the “main beam”) generated by the seed laser 110. The reference beam has a wavelength that is only slightly amplified or not amplified at all by the optical amplifier 104. Thus, the reference beam itself is not appreciably amplitude modulated, and thus can be used to track phase drift of each channel both between and during optical pulses while providing a stable signal to the LOCSET circuit for analysis. One example of a suitable modified phased array beam steering system is described with reference to FIG. 3 and generally designated by the reference numeral 300.

[0028] 3, both the seed laser 110 (e.g., generating a main beam represented as a series of laser pulses at a desired pulse repetition rate having a desired pulse width) and the reference laser 302 (e.g., generating the reference beam described above) are coupled to a common photonic integrated circuit (PIC) 304. Generally, the photonic integrated circuit (PIC) 304 may be provided as described above with respect to FIGS. 1 and 2, or may be modified as described in more detail with respect to FIG. 4.

[0029] The optical output of the PIC 304 is then amplified by an optical amplifier 104. The optical beam output by the optical amplifier 104 includes a main beam and a reference beam. However, the reference beam is separated from the main beam (e.g., by a simple dichroic mirror 306) and directed onto the aforementioned photodetector 118 of the LOCSET system. Because the main beam amplified by the optical amplifier 104 passes through the mirror 306, it does not reach the photodetector 118 and does not disturb (e.g., saturate) it.

[0030] Referring to FIG. 4 , the PIC 304 is configured to process not only the wavelength of the reference beam (which is different from the wavelength of the main beam) but also the wavelength of the main beam (also referred to herein as the “main wavelength”) (e.g., 1030 nm + / −5 nm). Generally, the reference beam can be characterized as having a relatively narrow linewidth and a long coherence length. In one embodiment, the wavelength of the reference beam (also referred to herein as the “reference wavelength”) ranges from 1070 nm (or thereabouts) to 1150 nm (or thereabouts) (e.g., 1100 nm). The beam splitter in the PIC 304 is a dual-wavelength beam splitter and must be designed to not only equally split the main beam at the main wavelength, but also simultaneously split the reference beam at the reference wavelength. Correspondingly, all subsequent components, such as the phase modulator array 204 and subsequent beam guiding and shaping optics (e.g., the three-dimensional waveguide 206), must be adapted to the wavelengths of both the main beam and the reference beam.

[0031] The above-mentioned modifications to accommodate laser energy beams at dominant and reference wavelengths preclude the use of large-mode photonic crystal fibers, which have only a fairly narrow wavelength range (1100 nm is well outside that range) where the propagated mode is stable and near single mode. However, with the coherent addition of many modes (in separate cores or in multimode fibers (or solid-state amplifiers)), the use of smaller mode field diameters is not an issue.

[0032] Another problem arising from the above correction is that nulling the phase difference between different channels at the reference wavelength does not necessarily mean simultaneously nulling the phase difference between different channels at the dominant wavelength. Therefore, additional phase calibration is required. This is shown in Figure 3, where an additional beam pickoff 308 collects a sample of the amplified main beam, which is then focused (e.g., via lens 310) onto aperture 312, behind which resides a photodetector 314 (e.g., a photodiode). Traditional (slow) SPGD algorithms can be used to process the phase relationship at the dominant wavelength once during calibration. The LOCSET electronics can then detect the corresponding phase relationship at the reference wavelength and stabilize the phase drift during the calibration process. As a result, even a very large number of channels can be optimized. Each "phase wrap" (i.e., a phase drift greater than 2π corresponding to the reference wavelength) can then be counted and tracked so that the overall phase relationship at the dominant wavelength can be controlled, even if the differential path length drift of the individual channels accumulates to many micrometers. For example, a 20 μm differential drift, measured as 18 "wraps" and a 0.36π phase drift at 1100 nm (18 × 2π + 0.36π = 36.36π = 2π * 20 μm / 1100 nm), easily translates to 19 "wraps" and a 0.83π phase drift at 1030 nm. Thus, the control electronics 108 can compensate for the 0.83π phase shift at 1030 nm with the corresponding phase modulator to return the two channels to their nominal phase relationship.

[0033] An advantage of the embodiments described with respect to Figures 3 and 4 is that the phase-locking electronics are decoupled from the repetition rate and pulse width of the main beam, which may vary depending on the seed laser used or various methods of operating the seed laser. As with the embodiments described above with respect to Figures 1 and 2, the process beam transmitted through the beam pickoff 308 shown in Figure 3 may be directed to the harmonic conversion module 120 and relayed to a beam positioning system (not shown) as needed, such as by methods known in the art, or any combination thereof.

[0034] Additional Embodiments Regarding Harmonic Conversion 1 and 3 is configured to ensure that the process beam is a collimated (or at least substantially collimated) optical beam, so that all rays in the process beam can be parallel (or at least substantially parallel) to the harmonic generation module 120, regardless of the angle at which the process beam is steered (by the phased array steering technique described above), consistent with the necessary boundary conditions for efficient harmonic generation.

[0035] Although Figures 1 and 3 illustrate systems in which no lenses are positioned in the beam path through which the process beam (output by the phased array beam steering system) may propagate, it will be appreciated that one or more lenses, mirrors, etc., or any combination thereof, may be provided to reduce the size (e.g., width or diameter) of the process beam that ultimately propagates to the harmonic conversion module.

[0036] In some cases, a beam positioning system such as an AOD or EOD may operate well for light within one wavelength range (e.g., in the infrared region of the electromagnetic spectrum) but not necessarily for light within another wavelength range (e.g., in the visible or ultraviolet region of the electromagnetic spectrum). Therefore, if desired, a harmonic generation module 120 may be disposed between the phased array beam steering system 100 or 300 and the beam positioning system (e.g., to convert the wavelength of the process beam to another wavelength). In the embodiment shown in FIG. 5, a lens (e.g., relay lens 500) is optionally disposed between the harmonic conversion module and the beam positioning system 502 (e.g., an AOD, electro-optic deflector (EOD), galvanometer mirror scanner, rotating polygon mirror scanner, etc., or any combination thereof) to reduce the lateral displacement of the process conversion caused by lens 112.

[0037] While the use of harmonic conversion module 120 has been described in connection with various embodiments of phased array beam steering systems 100 and 300, it should be understood that harmonic conversion module 120 may also be used to convert the wavelength of a process beam output by beam positioning system 502 (e.g., AOD, EOD, galvanometer mirror scanner, rotary polygon mirror scanner, etc.). In this case, a lens (e.g., 600) may be positioned in the beam path between beam positioning system 502 and harmonic conversion module 120, as exemplarily shown in Figure 6. In the embodiment shown in Figure 6, the optical output of beam positioning system 502, as well as the optical input of harmonic conversion module 120, are located at or near the focal point of lens 600.

[0038] By placing the harmonic conversion module 120 "optically downstream" of the phased array beam steering system 100 or 300, or other beam positioning system (e.g., AOD, EOD, galvanometer mirror scanner, rotating polygon mirror scanner, etc.), the advantages associated with utilizing such beam positioning systems can be realized for many wavelengths.

[0039] For example, a shear-wave TeO AOD can have a large number of resolvable spots (typically greater than 100), which makes it a very attractive beam steering device. However, shear-wave TeO AODs cannot be used to deflect relatively high-power (i.e., greater than 10 W or so) process beams having wavelengths in the UV region of the electromagnetic spectrum. By placing lens 600 and harmonic conversion module 120 "optically downstream" of the shear-wave TeO AOD, the wavelength of the process beam output by the shear-wave TeO AOD can be converted to a wavelength in the UV region of the electromagnetic spectrum.

[0040] In another example, materials typically used for EODs operate in the IR and (to some extent) the visible region of the electromagnetic spectrum, but do not operate at all in the UV region of the electromagnetic spectrum. By placing lens 600 and harmonic conversion module 120 "optically downstream" of the EOD, the wavelength of the process beam output by the EOD can be converted to a wavelength in the UV region of the electromagnetic spectrum.

[0041] In another example, a quartz AOD can operate in the UV and IR regions of the electromagnetic spectrum, and the number of resolvable spots that can be produced by the quartz AOD is the same for either wavelength when using the same bandwidth and acoustic aperture. However, it is typically easier to scale the power of a process beam in the IR region of the electromagnetic spectrum than to scale the power of a process beam in the UV region of the electromagnetic spectrum; thus, although a quartz AOD typically has a relatively high diffraction efficiency in the UV region of the electromagnetic spectrum, power loss in the IR region of the electromagnetic spectrum due to the quartz AOD's limited diffraction efficiency can be more easily compensated for than power loss in a process beam having a wavelength in the UV region of the electromagnetic spectrum. Thus, by providing lens 600 and harmonic conversion module 120 "optically downstream" of the quartz AOD, a relatively high-power IR-wavelength process beam input to the quartz AOD can be diffracted (e.g., deflected or not) by the quartz AOD and the diffracted process beam can then be converted to a wavelength in the UV region of the electromagnetic spectrum.

[0042] conclusion The foregoing describes embodiments and examples of the present invention and is not to be construed as limiting thereof. While several specific embodiments and examples have been described with reference to the drawings, those skilled in the art will readily recognize that many modifications to the disclosed embodiments and examples and other embodiments are possible without materially departing from the novel teachings and advantages of the present invention. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the claims. For example, those skilled in the art will understand that the subject matter of any sentence, paragraph, example, or embodiment can be combined with part or all of the subject matter of any other sentence, paragraph, example, or embodiment, except where such combinations are mutually exclusive. Therefore, the scope of the present invention should be determined by the following claims and any equivalents of such claims to be included therein.

Claims

1. a first beam positioning system capable of deflecting a laser beam having a first wavelength, the first beam positioning system including a phased array beam positioning system; a beam splitter configured to transmit a portion of the laser beam deflected by the first beam positioning system and to reflect another portion of the deflected laser beam; a photodetector positioned to receive the other portion of the deflected laser beam and output a corresponding detection signal; a second beam positioning system positioned within a beam path through which the laser beam can propagate after deflection by the first beam positioning system, the second beam positioning system including an acousto-optic deflector; a harmonic conversion module disposed in the beam path between the first beam positioning system and the second beam positioning system; Equipped with the harmonic conversion module is configured to receive the portion of the deflected laser beam and convert the first wavelength of the deflected laser beam to a second wavelength. system.

2. The acousto-optic deflector is a shear wave TeO 2 The system of claim 1 , which is an acousto-optic deflector.

3. The system of claim 1 , wherein the acousto-optic deflector is a quartz acousto-optic deflector.

4. The system of claim 1 , wherein the first wavelength is in the infrared region of the electromagnetic spectrum.

5. The system of claim 1 , wherein the second wavelength is in the visible region of the electromagnetic spectrum.

6. The system of claim 5 , wherein the second wavelength is in the visible green light region of the electromagnetic spectrum.

7. The system of claim 1 , wherein the second wavelength is in the ultraviolet region of the electromagnetic spectrum.

8. The system of claim 1 , further comprising a lens disposed between the harmonic conversion module and the second beam positioning system.

9. 10. The system of claim 1, further comprising: a control circuit communicatively coupled to an output of the photodetector and an input of the first beam positioning system, the control circuit configured to generate a control signal based on the detection signal and output the control signal to the first beam positioning system.

10. 10. The system of claim 1, further comprising a lens disposed between the first beam positioning system and the harmonic conversion module, the lens configured to collimate light in the portion of the deflected laser beam received at the harmonic conversion module.

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