Bonding of nonlinear optical materials

Abstract

In one embodiment, the disclosure includes a method for forming an optical element. Planes of optical materials are diffusion-bonded to form a single, larger nonlinear optical element. The bonding surface may be configured at an angle to an input wave passing through the diffusion-bonded structure. In one embodiment, the optical material is lithium triborate (LBO). In some embodiments, multiple optical materials are diffusion-bonded in one or more dimensions to create a larger optical element. In some embodiments, the larger optical element is used in a laser system. In one embodiment, the disclosure includes a fusion reactor comprising a laser system with diffusion-bonded nonlinear optical materials.

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority to U.S. Provisional Patent Application No. 63 / 486,464, filed on 22 February 2023, the entire contents of which are incorporated herein by reference.

[0002] This disclosure relates to optical materials, and more particularly to techniques for joining and using nonlinear optical materials such as LBO crystals. [Background technology]

[0003] Nonlinear crystals are widely used to generate optical frequencies that cannot be easily obtained directly from lasers. For example, a volume of 1 cm³ 3 Much smaller nonlinear crystals are commercially used to convert an input infrared (IR) beam of light into an output visible or ultraviolet (UV) beam. The IR beam is not continuous and can often be pulsed, having an average power of, for example, tens to hundreds of watts, and a peak power that can be kilowatts, megawatts, or even more. Optical parametric oscillators (OPOs) or optical parametric amplifiers (OPAs) can similarly be constructed using nonlinear crystals.

[0004] Lithium triborate (LiB3O5) crystal (LBO) is an example of a nonlinear optical crystal. This crystal possesses a wide transmission range, moderate nonlinear coupling, a high damage threshold, and various desirable chemical and mechanical properties. It is often used, for example, for second harmonic generation in lasers. LBO also exhibits excellent power handling capabilities.

[0005] LBO crystals, like all nonlinear optics, are oriented to efficiently generate harmonics or for other nonlinear processes. The geometries for LBO and type I (i.e., twice the frequency at the same polarization) second harmonic generation are shown in Figure 1. In the case of type I second harmonic generation (SHG), input light enters the nonlinear crystal, and in this example, the LBO crystal is cut. The crystal axes are shown as x, y, and z. The wave vector of the input light is k ω The polarization is horizontal (in or out of the plane of the drawing). The output is the second harmonic of the input, and its wave vector is k 2ω The output light is polarized perpendicularly within the plane of the drawing. The crystal axes can be oriented for phase matching (for example, if the x-axis of the crystal is θ). PM The angle of k ω (Displaced from the direction of)

[0006] Nonlinear crystals, including LBOs, are formed by first growing a single-crystal material piece. This raw crystal is then oriented and cut into several pieces of the desired shape. Surface fabrication is then completed by grinding and polishing. Optical coatings may then be applied.

[0007] The optical aperture can be defined by the surface area through which light enters the optical crystal material. However, scaling some optical materials, such as LBOs, to produce large apertures is extremely difficult. Several problems that limit the production of LBOs with dimensions exceeding approximately 50 mm may include: (1) the time required to grow the crystal can range from several months to over a year; (2) optical homogeneity and quality are worse in very large crystals; and (3) the crucibles made from precious metals to grow large LBOs are extremely expensive.

[0008] Increasing the aperture of high-performance nonlinear optical crystals such as LBOs will enable their use in a wide range of emerging applications, including laser systems, controlled laser fusion, and other uses. [Overview of the Initiative]

[0009] With regard to the following description, and in particular with respect to the drawings, it should be emphasized that the details shown are illustrative examples for illustrative purposes and are provided to explain the principles and conceptual aspects of the disclosure. In this regard, no attempt has been made to provide any implementation details beyond those necessary for a basic understanding of the disclosure. The following description, together with the drawings, will make it clear to those skilled in the art how embodiments of the disclosure may be carried out. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows an exemplary light beam passing through an optical crystal material. [Figure 2] This figure shows how LBO crystals are joined together in the y-plane according to one embodiment. [Figure 3] This figure shows how LBO crystals are joined together in the z-plane according to one embodiment. [Figure 4] This figure shows an inclined joint line according to one embodiment. [Figure 5] This figure shows how to create an inclined joint line according to another embodiment. [Figure 6] This figure shows a method, according to another embodiment, in which three or more nonlinear optical components are diffusely bonded to form a single diffusely bonded optical component. [Figure 7] This figure shows joining along multiple dimensions according to another embodiment. [Figure 8A] This figure shows an optical crystal material used to form a composite optical crystal material according to one embodiment. [Figure 8B] This figure shows a composite optical crystal material according to one embodiment. [Figure 8C]A diagram showing a technique for creating a plurality of optical crystal materials according to one embodiment. [Figure 9A] A diagram showing an optical crystal material used to form a composite optical crystal material according to another embodiment. [Figure 9B] A diagram showing an optical crystal material used to form a composite optical crystal material according to another embodiment. [Figure 9C] A diagram showing a composite optical crystal material according to one embodiment. [Figure 10] A diagram showing an exemplary technique for fabricating an optical crystal material used to form a composite optical crystal material according to another embodiment. [Figure 11] A diagram showing an optical crystal material used to form a composite optical crystal material according to another embodiment. [Figure 12] A diagram showing an exemplary composite optical crystal material according to one embodiment. [Figure 13] A diagram showing an exemplary composite optical crystal material according to another embodiment. [Figure 14] A diagram showing another exemplary technique for making an optical crystal material used to form a composite optical crystal material according to one embodiment. [Figure 15] A diagram showing yet another exemplary technique for making an optical crystal material used to form a composite optical crystal material according to one embodiment. [Figure 16] A diagram showing an exemplary use of one of the techniques described herein according to various embodiments. [Figure 17] A diagram showing another exemplary use of the techniques described herein according to various embodiments. [Figure 18] A diagram showing an exemplary process for making diffusion-bonded crystals according to one embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0011] In the following description, for the sake of explanation, many examples and specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be apparent to those skilled in the art that the present disclosure as described in the claims may include some or all of the features in these examples, either alone or in combination with other features described below, and may further include modifications and equivalents of the features and concepts described herein.

[0012] In the following figures, it should be noted that the direction of the wavevector of the optical beam is indicated by the symbol k. Light passing through an optical crystal material experiences different refractive indices in various directions. These differences in refractive index are often used to determine the crystal orientation and can be specified as the x-axis, y-axis, and z-axis. For example, in an LBO crystal, the direction inside the crystal where the electric field of the light wave experiences the highest refractive index can be called the z-axis, the direction inside the crystal where the electric field experiences the lowest refractive index can be called the x-axis, and the other directions inside the crystal can be called the y-axis. As another example, in the case of a BBO crystal, one axis (z) has a specific refractive index, and the other two axes have the same refractive index as each other. Thus, in the case of BBO, the crystal orientation is often specified such that the x-axis and y-axis are two directions inside the crystal that have the same refractive index, and the z-axis is the direction inside the BBO crystal that has a different refractive index (e.g., higher or lower than the x-axis and y-axis, and in the case of BBO, the refractive index in the z-axis is lower). Those skilled in the art will understand that other optical crystal materials can be similarly associated with the crystal orientation for a particular crystal type in order to apply the techniques described herein. Therefore, the embodiments described below are merely illustrative.

[0013] (Exemplary Applications and Background) The light propagation, phase matching, and other phenomena in optical crystals according to the various embodiments shown below are explained as examples in the following paragraphs. The following materials exhibit optical properties that are useful in understanding the various aspects, features, and advantages of the innovative techniques described herein.

[0014] Figure 1 shows a light beam passing through an optical crystal material. In this example, the light is traveling along the x-axis at a phase-matching angle (θpm) along a path specified by the k-vector (kω), with the z-axis off-page. Such a system can be used to increase the frequency of light and decrease the wavelength by generating harmonics of the fundamental light frequency. For example, in type I second harmonic generation (SHG), two photons with the same polarization with respect to the crystal combine to form a single photon with twice the frequency. In type II SHG, two photons with orthogonal polarizations combine to form a single photon with twice the frequency. As a more specific example, a beam passing through an LBO crystal oriented for type I second harmonic generation can have an input wavelength of approximately 1064 nm, where k is perpendicular to the LBO z-axis. The crystal axes are denoted x, y, and z, following the standard convention described above, and the x-plane, y-plane, and z-plane are planes perpendicular to their respective axes. In the following diagrams, the direction of the arrows denoted by k indicates the wave direction just inside the nonlinear crystal, whereas the sign k is drawn outside the crystal in diagrams where there is more space for illustrative purposes. In some diagrams, k is drawn perpendicular to the surface of the LBO crystal, which is a rough drawing for illustrative purposes. The direction of light can be tilted slightly (typically about 0.5 degrees) with respect to the crystal's plane normal to avoid back reflection or etalon effects. Nevertheless, the beam inside the crystal is oriented at a phase alignment angle within tight tolerances so that the beam direction is phase-aligned with the appropriate crystal axis.

[0015] For LBO crystals used at approximately room temperature, around 300K (approximately 27C), the phase matching angle can be determined as theta = 90 degrees and phi = 11.4 degrees for a type I SHG. These two angles determine the direction in radial coordinates. Theta is 90 degrees, and as a result, the k-vector is shifted 90 degrees from the z-axis. Thus, in this example, the k-vector lies in the xy-plane. In some cases, the phase matching angle is simply called the phi value, since theta is 90 degrees and phi does not change over the wavelength and temperature range. Thus, phi is shifted 11.4 degrees from the x-axis. For example, the polarization of 1064 nm light is oriented along the z-axis. The 1064 nm input beam propagates in the xy-plane, and the polarization is perpendicular to the beam direction (k-vector). Light polarized along the z-axis receives the largest refractive index. In this example of 1064 nm light polarized along the z-axis, the refractive index is 1.6053. The speed of light in this case is c divided by 1.6053, where c is the speed of light in a vacuum. If 532nm green light is polarized in the same direction as 1064nm light, the 532nm green light will have a higher refractive index because the shorter wavelength interacts more with the material. A laser SHG system can be configured so that the 532nm and 1064nm beams have the same refractive index of 1.6053. Thus, the polarization of the generated 532nm light is directed in a different direction than the polarization of the 1064nm light. For 532nm light polarized along various axes (x, y, or z), the refractive index n is as follows: when polarized along x: n = 1.5785 (too small), when polarized along y: n = 1.6064 (just a little too large), when polarized along z: n = 1.6215 (much too large). Based on these refractive indices, within the crystal, the polarization of 532 nm light can be almost aligned with y but slightly towards x to achieve a target factor of 1.6053. However, the polarization of 532 nm light is essentially perpendicular to beam propagation (i.e., perpendicular to the k-vector). Therefore, the beam propagation (i.e., the k-vector) for green light can be configured to be almost aligned with the x-axis but tilted towards the y-axis. This phase matching is performed at an inclination angle of 11.4 degrees in this example.This results in the refractive index of the 532nm light being equal to 1.6053. Note that if phase matching is performed, phi can be +11.5 or -11.5. In some exemplary cases, the crystal is oriented at approximately 11.4 degrees, and therefore the beam enters with normal incidence. Thus, the beam within the crystal is nearly perpendicular to the input and output planes. However, inside the crystal, the beam passes along an angle of 11.4 degrees with respect to the x-axis in this example.

[0016] In the example above, the k-vector of the 1064 nm (and / or 532 nm) beam is not parallel to any of the crystal axes. The k-vector is perpendicular to the z-axis, which is one of the axes. Both the fundamental beam at 1064 nm and the second harmonic beam at 532 nm have their respective k-vectors in the same direction. The value of k depends on the wavelength, and the k-vectors for both 1064 nm and 532 nm are in the same direction. In some embodiments, the optical crystal material can be cut such that both the input and output planes of the crystal are perpendicular to the axes. However, using the example above, the k-vector is still offset by 11.4 degrees from the x-axis in the xy-plane inside the crystal. However, because light refracts (bends) as it enters the material, the angle at which the beam enters the crystal is not 11.4 degrees. If the refractive index of air is approximately 1, and in this case the refractive index of LBO is approximately 1.6053, then according to Snell's law, the sine of the angle in air is equal to 1.6053 times the sine of the angle in the material, and the angle in the material is 11.4 degrees in the case of phase matching. Solving this, we find that the angle in air is approximately 18.4 degrees, which is a deviation from the normal to the surface. However, this is just one example. In the case of third harmonic generation (THG), the angle is different. For example, 354.7 nm is the third harmonic of 1064 nm. To obtain the third harmonic in LBO, the fundamental wave (1064 nm) is mixed with the second harmonic, i.e., 1 + 2 = 3. In the case of an LBO at 300 K with inputs of 1064 nm and 532 nm, an output of approximately 354.7 nm, and commonly used type II phase matching, the phase matching angles are, for example, theta = 42.6 degrees and phi = 90 degrees.

[0017] For second harmonic generation (SHG) or third harmonic generation (THG), the phase matching angle is temperature-dependent. LBOs are typically more sensitive to temperature changes than BBOs. Consider the cases of LBO, SHG, and type I. For example, starting at room temperature, as the crystal gets hotter, the refractive index changes and the phase matching angle phi decreases until it becomes zero. For LBO and type I SHG, there is one specific temperature at which there is a unique phase matching solution where phi is zero and theta is 90 degrees. This is commonly called "noncritical phase matching." This occurs when a 1064 nm input enters an LBO crystal at a temperature of approximately 150 C (equivalent to approximately 422 K). Thus, in this special case, the beam (k-vector) is aligned with the crystal axis (e.g., the x-axis). In some applications, noncritical phase matching is used, for example, to achieve favorable angle insensitivity. Noncritical phase matching temperatures and other parameters also exist for some other applications and optical crystals, but the values ​​generally differ.

[0018] (Example embodiment) Features and advantages of this disclosure include using diffusion bonding to fuse two or more smaller optical crystalline materials into one larger composite optical crystalline material structure. The resulting structure can have a bonding line that is substantially invisible in the optical beam path. This disclosure includes a scalable multi-stage bonding process in which many optical crystalline material sub-pieces can be bonded. In some embodiments, the bonding line can be such that it does not need to be avoided or shadowed for protection. Furthermore, some embodiments of the disclosed process can be applied to other optical crystalline materials (including other nonlinear materials), such as (but not limited to) barium betaborate (BBO). One advantage of the techniques disclosed herein is that they can meet the growing need for, for example, large aperture optical crystals (e.g., LBO) or longer crystals (e.g., BBO).

[0019] Figure 2 shows the joining of LBO crystals in the y-plane according to an exemplary embodiment. In this exemplary example, two separate LBO pieces 201a and 201b are shown. In this exemplary example, LBO pieces 201a and 201b can have the same shape and the same crystal orientation. The LBO pieces 201a and 201b are joined along the plane of each LBO piece to form a single LBO piece. In this example, the crystals are oriented along a total of three axes perpendicular to the crystal surface, and when the input beam enters the crystal, it is at an angle θ from the perpendicular. PM The surface is tilted by a certain amount (here, it is offset from the x-axis). The dotted line 210 indicates the joining where the outer surfaces of each piece meet. After joining, the surfaces are coplanar. Furthermore, the cross-sectional areas (e.g., along the y-axis) of the diffusion-joined first optical crystal material 201a and second optical crystal material 201b are larger than the cross-sectional areas of the first optical crystal material and the cross-sectional areas of the second optical crystal material. Excellent joining will be substantially invisible in the actual piece. For example, diffusion joining can be achieved by optically contacting two finely polished surfaces (e.g., bringing together smooth, flat, optically good surfaces), and then heating them in a furnace below the melting temperature of the crystal. At this high temperature, the molecules of the substrate become mobile and intertwine with each other. Diffusion joining can be performed with superpolished surfaces that are cleaned to leave no contamination, have a very low defect level (ideally none), and have been optically contacted cleanly before heating. The polished surface can be made defect-free (no scratches or digs) when inspected under strong light, such as from a fiber optic beam light source or similar microscope illumination device, both with the naked eye and under a microscope with a magnification of 50x or more. In addition, the angle of incidence of the light beam can be varied to yield the highest visual sensitivity. This atomic-level "welding" of two or more pieces produces a single piece with monolithic crystalline properties. After the pieces are joined together to form a larger piece, further grinding and polishing steps (not shown) can be performed to produce a finished piece that can, for example, be subjected to optical coating.

[0020] Diffusion bonding can occur within a temperature range determined, for example, by the type of optical crystal material, the volume of the crystal, and the surface area. Generally, the temperature for the bonding (or "penetration") portion of the crystal in that cycle is between 60% and 90% of the melting point of a particular type of optical crystal material. The length of the penetration time depends in part on the volume and surface area of ​​the crystal. In one embodiment, there is a stepwise heating or ramp-up, the length of which depends on the volume of the crystal, its thermal conductivity, and its coefficient of thermal expansion. After bonding is complete, slow cooling is performed, which also depends on the size and properties of the crystal. This portion of the cycle can also be slow enough to eliminate internal stresses, which may have been done during the previous treatment.

[0021] Certain embodiments of this disclosure involve diffusion bonding two identical crystalline materials having the same crystal orientation. Thus, the optical crystalline materials to be diffusion bonded can be aligned, for example, before heating. In some exemplary embodiments, the axial crystal alignment must be within a specific tolerance of approximately 40 arc seconds for a Type I SHG. However, this requirement may vary for different applications and may be inversely proportional to the thickness of the material. The following are exemplary alignment specifications based on acceptable tolerances for phase alignment in a particular application (e.g., harmonic generation for powerful beams used in laser fusion). However, tolerances may also be limited by the constraint of obtaining a good bond across the surface, and some mismatch in thermal expansion coefficients occurs due to angular mismatches between the bonded pieces. This may also limit tolerances, particularly for larger bond lengths.

[0022] (1) Type I SHG, a sample approximately 10 mm thick, with a matching tolerance of 40 arc seconds.

[0023] (2) Type II SHG, with twice the matching tolerance of (1) above, and therefore a looser tolerance than (1).

[0024] (3) NCPM SHG, a matching tolerance approximately 100 times that of (1) above, and an even looser tolerance than (1).

[0025] (4) Type II THG, with a matching tolerance approximately 2 / 3 times that of (1) above, and a tighter tolerance than (1).

[0026] (5) Type I THG, with a matching tolerance approximately 1 / 4 that of (1) above, and a tighter tolerance than (1).

[0027] (6) For ultra-high-speed applications requiring crystals that can be approximately 0.1 mm thick, with a matching tolerance approximately 100 times that of (1) above, and a looser tolerance than (1).

[0028] In some embodiments, the junction plane may be advantageously angled with respect to the optical path, as will be discussed further below (for example, so that there will be no localized strain or shadow in terms of defects in the junction). In various embodiments, the angle of the k-vector with respect to the diffusion junction plane between two diffusion-joined crystals can be, for example, 0.25 to 45 degrees.

[0029] The wavefront distortion of the beam passing through the junction surface must be limited to one-tenth of the wavelength (lambda / 10) or even lower, for example, half the wavelength (lambda / 2). This is a measurement of the distortion of light as it passes through the medium, and the optimization of this parameter may vary depending on the application. The absorption across the junction surface should be as low as possible, comparable to that of a monolithic crystal in the case of high-energy lasers. In some exemplary embodiments, the absorption across the junction surface is, for example, less than 20 ppm / cm for a crystal.

[0030] The laser-induced damage threshold (LiDT) generally refers to the maximum intensity that a laser optical system can withstand before being damaged. The LiDT of the junction surface can be made as close as possible to the LiDT of the bulk crystal. In some exemplary embodiments, a superpolishing process can result in a LiDT greater than 95 J / cm² at 355 nm for ns pulses at, for example, 20 Hz. In some embodiments, a diffusion junction surface has a LiDT similar to that of the rest of the bulk crystalline material on both sides of the junction, for example.

[0031] In some cases, the two pieces 201a-b of a diffusion-bonded pair may have slight misalignments in their crystal axes, which may be detected during the phase matching process (e.g., in a nonlinear process to achieve various wavelengths of light). In some embodiments, processes may be taken to ideally minimize this misalignment. However, the misalignment will not be zero, as in a monolithic crystal. This technique achieves acceptable performance with bonded crystals that have, for example, non-zero misalignments. Bonded surfaces, such as face 210, may be visually detectable, for example, due to defects left after a polishing process. Processes may be taken to minimize such defects to an acceptable level of performance. Bond lines may be visible at the edges of the bonded crystals. For example, the outer edge may not be completely bonded. If such bond lines are only visible outside the effective aperture (where light does not pass through, e.g., the outer edge), such bond lines may have a minimal impact on performance.

[0032] The surface quality of an optical component is a specification that measures surface defects of the component, such as scratches or digs (indentations on the surface). Typically, surface quality is evaluated according to standards defined by U.S. military standards or the International Organization for Standardization. According to U.S. military standards, surface quality measurements are expressed by two numbers: scratches and digs. The scratch number evaluates the brightness of scratches on the surface, while the dig number measures the size of the maximum dig present in the component. In both cases, a lower number indicates a higher quality surface. Reflected wavefront distortion (RWD), sometimes called reflected wavefront error (RWE), identifies the deviation of the reflected component of incident light from a perfectly flat plane wave. With regard to certain exemplary bonding processes described herein, including Figure 2, a first exemplary step may include polishing the bonding surface in preparation for a bonding that typically has a scratch-dig surface quality of 0-0 (e.g., MIL-PRF-13830 ReV.B) and reflected wavefront distortion in lambda / 10 (at 633 nm) as measured by, for example, a laser interferometer.

[0033] Figure 3 shows the joining of LBO crystals in the z-plane according to one embodiment. In this example, the joining is performed along the z-plane. In Figure (a), two pieces of LBO, 301a and 301b, are joined to form a larger piece at the bottom of the figure. In Figure (b), the same process is shown as viewed from the top of Figure (a). In this example, the k-vector is parallel to the plane of the joining, and therefore the beam propagates directly below the joining. As the beam propagates, it extends to two transverse dimensions, and a very narrow linear sector of the two-dimensional range of the beam traverses the thin joining line. As shown in Figure (b) of Figure 3, phase matching is achieved when the crystals are joined at a phase matching angle θ PM Note that this is appropriate because it is tilted only relative to the surface of the crystal fragment (and composite fragment).

[0034] Figure 4 shows an inclined junction line according to one embodiment. In this example, two LBO pieces are joined at an angle along the z-axis, so that the beam does not propagate directly below the junction line plane as the beam propagates in Figure 3, which can be advantageous, for example, by reducing beam distortion from the junction. In this exemplary embodiment, one of the LBO pieces may have a trapezoidal cross-section. In other embodiments described below, the crystal axes are rotated with respect to the junction line, so that the beam crosses the junction line at an angle as it propagates along one or more of the crystal axes, thereby reducing distortion. The arrangement in this example is shown in three dimensions in Figure (a), the same process is shown in two dimensions in Figure (b), and a two-dimensional diagram along the z-axis is shown in Figure (c). Here, it can be seen that the LBO piece in Figure (a) is cut at a junction angle α that is offset from the plane parallel to the z-plane, so that instead of a wave vector k that is parallel to the junction plane, the light propagates in a different direction from the junction line, for example, the junction line and the propagation direction differ by an angle α. As the beam propagates, it extends to both the left and right surfaces. The broad two-dimensional sector of the beam crosses the junction line, but the beam is less affected by the inclined junction than a beam passing through parallel junction surfaces (for example, if the junction angle is zero or nearly zero) as shown in Figure 3.

[0035] Figure 5 shows the creation of an inclined junction line by another exemplary embodiment. The junction method shown in Figure 5 yields similar results to the junction method in Figure 4, but starts with optical crystal pieces 501a and 501b, all of which have rectangular cross-sections, which can, for example, not be trapezoidal. This makes it easier to hold these pieces, for example, during junction, and ultimately can be less expensive. Figures (i) to (iii) at the top of Figure 5 show pairs of LBO pieces before junction, shown in both 3D and 2D renderings as well as in side view (iii). The following Figures (iv) to (vi) below show the state of the LBO pieces after junction. In all of Figures (i) to (vi), the input wave vector k enters the piece, and then the phase matching angle θ PMIt is tilted. In many cases, it is desirable, but in order to allow light to enter with approximately normal incidence, the piece may be cut along the dashed line shown in Figure (vii), thereby yielding the final shape shown in Figures (viii) and (ix). For example, here a rotated rectangular subcube 501c is cut from diffusion-bonded optical crystal materials 501a and 501b such that the diffusion junction is tilted between opposing parallel surfaces of the diffusion-bonded composite optical crystal material. Some material is lost, but the opening can remain wider than the opening of either of the original pieces.

[0036] Figure 6 shows a diffusion bonding of three or more nonlinear optical components to form a single diffusion-bonded optical component according to another embodiment. This is carried out in a single diffusion bonding step, which is otherwise similar to the bonding process that starts with the two parts shown above, for example in Figure 2. Alternatively, three or more parts may be bonded in series (e.g., linearly) using a series of single bonding steps between two LBO pieces, for example, as shown in Figure 2.

[0037] Figure 7 shows bonding along multiple dimensions according to another embodiment. In various embodiments, diffusion bonding of optical crystalline materials may be performed to increase the aperture or length of the optical crystal or both. For example, in some embodiments, bonding along further dimensions may result in an aperture that can be scaled in two dimensions by bonding parts bonded along one dimension to form a larger part bonded along another dimension. While the examples shown herein show specific shapes and arrangements, many shapes may be used for individual parts, and in some cases, it is possible to form a mosaic of optical crystalline materials with contact surfaces (various repeatable shape patterns, e.g., a potentially seamless rectangular mosaic). The bonding in this step begins, for example, with long LBO pieces 701a-c, each formed by bonding smaller parts to itself, as described above. The bonding lines in the long pieces 701a-c are not shown here. The long pieces 701a-c may be shaped according to the methodology shown in Figure 4, for example, so that the cross-section of the middle piece 701b is a parallelogram, and the other pieces 701a and 701c have trapezoidal cross-sections with surfaces that can be made coplanar with the surface of piece 701b, for example. The three pieces 701a-c are then joined together to form one large LBO piece. In general, this method may alternatively be started with two or more pieces. Alternatively, this joining step may also be performed on all rectangular pieces, as shown in Figure 5 (for example, the composite piece may be cut after joining). Alternatively, three or more pieces may be simply joined linearly between two pieces using a series of single joining steps, as shown in Figure 2.

[0038] After each bonding step, the surface, which has been strained by the high temperature of the diffusion bonding cycle, can be ground and polished. The technique described herein provides an optimized bonding process in which the bonding line does not need to be avoided by or blocked from the transmitted laser beam in order to prevent localized strain. Thus, the final piece is obtained from a multi-stage bonding process in which many LBO pieces can be bonded. Furthermore, this process can be used for other nonlinear optical crystalline materials such as (but not limited to) barium beta-borate (BBO).

[0039] With regard to the various bonding processes described herein, the first step is that the surfaces to be bonded can be polished in preparation for a bond having a surface quality of 0-0 scratch-dig and a wavelength flatness of lambda / 10 (at 633 nm).

[0040] Figures 8A and 8B show optical crystal materials used to form a composite optical crystal material according to one embodiment. First, the optical crystal materials 801a to d in Figure 8A are aligned. For example, the crystal orientation (e.g., the x, y, and z axis directions) of each piece (before or after cutting) can be analyzed using X-ray orientation (e.g., by detecting the deflection angle of X-rays shifted from the crystal piece). One exemplary technique is to orient the crystal and fabricate it as a rectangular solid, such that, for example, the x, y, and z axes of the crystal are perpendicular to the plane of the fabrication piece from which they begin. In the subsequent processes described herein, larger crystal pieces may be cut to obtain, for example, two or more optical crystal materials 801a to d.

[0041] In this example, the optical crystal materials 801a-d in Figure 8A are heated and joined together to form the composite optical crystal material 800 in Figure 8B. In some embodiments, the optical crystal materials 801a-d are cut from the same crystal boule. For example, the crystal boule is a single-crystal ingot manufactured synthetically, for example, by generally starting with a seed crystal, where further crystalline material is deposited by immersing the seed crystal in a molten material. In other embodiments, the optical crystal materials 801a-d are cut from, for example, several different crystal boules. In this example, each optical crystal material 801a-d has the same material type (e.g., LBO or BBO), multiple planar surfaces, and the same crystal orientation relative to the planar surfaces. For example, the optical pieces 801a-d can be rectangles having, for example, opposing parallel surfaces 810a-b, 811a-b, and 812a-b. The crystal orientations of the optical crystal materials 801a-d are aligned (e.g., within tolerance). Optical crystalline materials according to various embodiments may include surfaces formed along various dimensions, which may be orthogonal or non-orthogonal. As shown in Figure 8A, each of the plurality of optical crystalline materials 801a-d includes three orthogonal dimensions, namely height (h), width (w), and thickness (t). In various embodiments, the height and / or width are greater than the thickness. Thus, the surface area of ​​the composite optical crystalline material can be greater than, for example, the surface area of ​​the constituent optical crystalline materials, where both h and w are greater than t.

[0042] Pieces 801a to 801d can be aligned and diffusion bonded to create a composite piece 800. For example, a planar surface of one optical crystal material (e.g., 812a of 801c) can be aligned with a planar surface of another optical crystal material (e.g., 812a of 801c), so that the flat planes of those optical crystal materials form a composite surface larger than any one of the multiple planar surfaces of the individual component pieces. In Figure 8B, four surfaces are aligned to form a composite surface 813a larger than the component surfaces. During diffusion bonding, for example, two or more pieces to be bonded can be pressed together so that their polished, normally oriented surfaces are in optical contact (e.g., by van der Waals forces), and thus they "stick together" when joined. The polished surfaces are cleaned and complementaryly shaped, so there is virtually no gap between the polished surfaces of the crystals. Thus, matching occurs when the polished surfaces naturally stick together. In this case, the contacted pair undergoes thermal annealing, where atomic diffusion occurs across the contact plane. In some embodiments, a simple L-bracket may be used to help guide the two pieces together. Once the two pieces are in contact, alignment is established. Thus, one or more planar surfaces of each optical crystal material (e.g., 810a / b and / or 811a / b) along one or more of the thickness and height or width are diffusely bonded to another planar surface of another optical crystal material among the multiple optical crystal materials (e.g., 810a / b and / or 811a / b) along one or more of the thickness and height or width. This is shown in Figure 8B, where the diffusion bonding is formed between surfaces along, for example, thickness and width and thickness and height. As a result, a composite optical crystal material 800 is obtained which includes opposing parallel planar surfaces having a larger surface area (e.g., four times that of 812a / b) than the surface area of ​​each of the multiple planar surfaces of the multiple optical crystal materials 801a-d. As a result, an increase in the aperture size through which light enters may be obtained. In this example, the k-vector of light lies in the xy-plane, where theta is equal to 90 degrees and phi is equal to 11 degrees (inside the crystal), and the crystal is oriented perpendicular to the aperture surface.Advantageously, in this example, the height of the composite piece 800 is 2h, the width is 2w, and the total surface area is four times the surface area of ​​the constituent pieces 801-d (e.g., four times the opening size). In some exemplary embodiments, pieces 801a and 801b are diffusion bonded, pieces 801c and 801d are diffusion bonded, and then the bonded pieces 801a / b are diffusion bonded to the bonded pieces 801c / d. However, the bonding may be carried out in different orders and combinations.

[0043] Figure 8C shows a technique for manufacturing optical crystalline materials 801a-d according to one embodiment. In this example, the optical crystalline material (e.g., the initial block or bulk material) includes multiple parallel surfaces, forming a rectangular or square cube. Manufacturing precisely parallel surfaces can be advantageously simpler than creating other specified angles between surfaces, for example, optical interferometry may be used to precisely measure the parallelism between parts, and this measurement can be a limiting factor in precision optical manufacturing. However, the flat planar surface configuration shown here is merely one example. It should be understood that other surfaces may be used. The planar surface 860a of the part on the left side of the drawing is the exit or inlet surface for the optical beam. The opposing side 860b on the right side of the drawing is parallel to the left side 860a and is similarly the optical inlet or exit surface.

[0044] Some embodiments of the present disclosure involve making multiple cuts of an optical crystalline material (e.g., a block or bulk material 800 as shown in Figure 8C) having a certain height and width in order to divide the optical material into multiple optical crystalline materials to be diffusion-bonded. The material 800 can be formed and cut and then, for example, heated and diffusion-bonded. In this example, the optical crystalline material 800 can be cut into four segments (constituent pieces) 850a to d, which are then diffusion-bonded, so that the opening of the bonded final piece is increased by about four times in this example (as shown in Figure 8B). First, the fabricated starting piece is cut into a plane along the dashed line shown. If this starting piece has dimensions of height (h) x width (w) x length (L), then the constituent pieces 850a to d have a thickness t equal to about L / 4 x w x h. The thickness of each piece is slightly less than L / 4 because some material is lost, for example, during surface cutting, grinding, and polishing. If the manufactured starting piece 800 shown herein is larger than, for example, a given target opening, then fewer joining and cutting steps may be required. In some exemplary embodiments, grinding and polishing operations may follow each time the piece is cut, so it would be advantageous to proceed without an excessively large number of joining steps.

[0045] In the examples shown in Figures 8A to 8C, the constituent optical crystal material pieces 801a to d can be made from a starting piece 800 by cutting the starting piece 800 into four constituent pieces (for example, pieces 850a to d in Figure 8C). It should be understood that the number of pieces is not limited to four. For example, six, eight, ten, or other numbers of constituent optical crystal material pieces can be used. Furthermore, each piece does not need to have a square cross-section (opening). In the case of an even number of pieces, the resulting joined composite piece can be, for example, rectangular, although a rectangular opening is not essential for this technique. For example, a rectangular or non-rectangular joined piece can be cut into other shapes such as rectangles of different sizes, circles, or ellipses.

[0046] Figures 9A to 9C illustrate diffusion bonding of an optical crystal material to increase its length. For example, BBO can be used as an optical switch. In the case of optical switch applications, it would be advantageous to increase the length of a single optical crystal. Figure 9A shows an optical crystal material 900 used to form a composite optical crystal material according to another embodiment. In this example, the optical crystal 900 is cut along the x-axis (cutting portion 911) and the y-axis (cutting portion 912) to create, for example, individual optical crystal materials 901a - d. The z-axis of the crystal is perpendicular to the left and right surfaces in the figure. The initial crystal material 900 has a height of 2h, a width of 2w, and a thickness of t. Figure 9B shows the optical crystal materials 901a - d used to form a composite optical crystal material according to another embodiment. In this example, the optical crystal materials 901a - d are created by cutting the optical material 900. However, it should be understood that the pieces 901a - d can be created from various starting pieces 900, for example, from the same or different boules. Figure 9C shows a composite optical crystal material according to one embodiment. Here, the optical crystal materials 901a - d are diffusion bonded such that the length of the diffusion bonded composite optical crystal material is greater than the height, width, and thickness (for example, of each piece 901a - d and / or the uncut material 900). The diffusion bonding lines are shown using the dashed lines 920, 921, and 922. In this example, the length L is equal to n * t, where n is the number of pieces being bonded (here, n = 4), and t is the thickness of both the uncut material 900 and the individual pieces 901a - d. In one embodiment, the diffusion bonded composite optical crystal material is used as an electro-optic modulator. A beam of light travels along the z-axis (for example, the k-vector is parallel to the z-axis). For example, electrodes can be formed on two opposite surfaces perpendicular to the x-axis and connected to a voltage. When the voltage is in one state, the optical beam passes through the composite material 950 with its polarization unchanged, and when the voltage is in another state, the optical beam passes through the composite material 950 with its polarization changed (modulated). When a polarizer (polarizing analyzer) is added, this element becomes, for example, an intensity modulator.

[0047] With respect to the composite piece in Figure 8B, the k-vector, at a phase matching angle phi of 11° in this case, traverses both the junction between the constituent pieces 801a / b and the junction between the constituent pieces 801c / d. Therefore, the k-vector can be directly aligned with the junction between the constituent pieces 801b / d and 801a / c in some crystal orientations. These two planes (between 801b / d and 801a / c), when fabricated as shown, can be extensions of each other that are as coplanar as possible. However, in some embodiments, the junction planes are advantageously almost invisible to light waves. To do this, the junction planes can be configured so that the beam does not directly propagate through either of the junction planes. To form a two-dimensional mosaic, the junction planes can be in crossing dimensions. The junction planes do not have to be exactly perpendicular to each other. A feature and advantage of some embodiments is that the beam is directed so that it is not parallel to either of the junction planes, while the beam is still directed for phase matching, for example.

[0048] Figure 10 shows an exemplary technique for fabricating optical crystal materials used to form a composite optical crystal material according to another embodiment. Figure 10 shows a technique for producing a diffusion-bonded optical crystal material such that the beam's k-vector does not pass through any of the bonding surfaces in any dimension. In some embodiments, the diffusion bonding between a planar surface of one optical crystal material and a planar surface of another optical crystal material is inclined with respect to the opposing parallel planar surfaces of the composite optical crystal material. Thus, when the optical crystal materials are diffusion-bonded, the optical crystal material pieces form bonding lines that are inclined with respect to the input and / or output surfaces. For example, in some exemplary embodiments, Figure 10 can be a fabricated starting piece similar to Figure 8C, where each side is initially a planar surface parallel to the opposing side. In this example, an angle α may be cut, ground, and / or polished on surface 1050 (here, the top surface) of the starting piece 1000. Therefore, surfaces 1050 and 1051 are inclined with respect to one or more other opposing parallel surfaces (e.g., surfaces 1052 / 1053 and / or 1010a / 1010b). A larger angle (α) is advantageous in that it results in a larger beam area over which the joint extends. However, a larger angle also means that more material is lost when cutting the piece at that angle, which is generally more expensive. Therefore, in various embodiments, the angle can be, for example, between 0.25 and 45 degrees. After forming angle α on side surface 1050, angle α can be cut, ground, and / or polished on the opposing side surface 1050 (here, the bottom surface) that is parallel to the side surface 1050 where angle α is formed. Thus, the side view of the optical crystal material 1000 along one dimension can form, for example, a parallelogram.

[0049] The constituent parts are shown in Figure 11. For example, the optical crystal material 1000 in Figure 10 can be cut, ground, and polished from the first part (solid line in Figure 10) to form the fabricated parts 1101a-d (dashed line in Figure 10). These optical crystal materials 1101a-d, which are constituents produced from the same or different starting parts, are diffusion-bonded, so that none of the bonding surfaces are parallel to the k-vector, for example, along any crystal axis. Figure 11 shows the optical crystal material used to form a composite optical crystal material according to another embodiment. In Figure 11, each constituent optical crystal part has an inclined top and bottom surface. These can then be bonded to form groups (pairs in this example), and then these groups can be further bonded to form a two-dimensional mosaic, as shown in Figure 12. Referring to Figure 12, the k-vector of beam propagation is angled with respect to the bonding surface between parts 1101b / d and 1101a / c (shown as a vertical dashed line). However, the polarization of light along the z-axis is in the same direction as one of the junction surfaces. Due to the introduction angle α, none of the junction surfaces are parallel to the beam. In this example, light can pass through the material at the phase matching angle and cannot directly pass through any of the junction surfaces. While junction surfaces between optical crystalline materials can be made virtually invisible to light, the above example shows that in some cases, junction surfaces can be found by adjusting the angle of light until a measurable change in the output light is produced, for example, by light traveling parallel to the junction surface.

[0050] In some embodiments, it may be desirable to change the direction of the k-vector in the crystal relative to the plane normal. In this case, the crystal orientation may be changed so that the x-axis is not perpendicular to the input / output plane, as shown in Figure 13 where the crystal orientation is rotated so that the x-axis is not perpendicular to the input plane. However, the phase matching angle must still be the same. Thus, the junction surface may be cut at an angle not perpendicular to the x-axis so as the beam passes through the phase-matched crystal, the direction of the k-vector in the crystal relative to the plane normal is changed. The motivation for this is that when the beam is far from the normal, there may be other considerations such as a substantially reduced aperture, making it more difficult to perform coating. Thus, it may be desirable to change the orientation of the crystal axis relative to the input / output plane normal so that the k-vector is at various angles relative to the input / output plane in order to maximize the aperture and / or other system parameters. Referring to Figure 14, an additional angle β may be added to the surfaces 1052 (front) and 1053 (back) of the fabricated component piece 1000, which are initially perpendicular to the y-axis. For example, further portions of the optical crystal material can be removed to form a third inclined surface 1452 and a fourth inclined surface 1453. In this example, the third inclined surface 1452 is parallel to the fourth inclined surface 1453. Considering the angle applied to the piece as "β", so both surfaces, which were initially perpendicular to the y-axis, can be cut, ground, and / or polished to create an angle β with respect to the y-axis. When these surfaces are later joined, they change the angle of the beam inside the material with respect to the joining surface from the phase-matching angle (θpm) to (θpm-β), or to the other direction (θpm+β) if inclined. For example, if it is desired that the angle between the k-vector of the phase-matched beam and the joining surface be 4 degrees, then β should be equal to 7 degrees and θpm should be 11 degrees.

[0051] In some embodiments, the constituent parts are optimized to be substantially identical, including substantially identical crystal orientations, even if they are not all cut from a common fabricated starting part. For example, in some embodiments, the removal of a portion of the optical material is performed individually in multiple optical crystal materials (after cutting, e.g., as shown in Figure 8C). This flexibility can be advantageous when many constituent parts are formed. One approach to this is shown in Figure 15, where three optical crystal parts 1501-1503 are shown as an example. Parts 1501-1503 may be from the same Boolean or different Boolean materials, for example. As before, in this figure, the material is cut, ground, and polished from the first part (solid line) to become the fabricated parts (dashed line). The three parts are all fabricated to have similar shapes and the same crystal orientation. In this example, the x, y, and z axes are perpendicular to the surface of their parts. The shown parts can then be, for example, ground and polished and diffusion-bonded using the method described above. If an angle α is provided in the parts as shown, the opposing surfaces are polished parallel to the surface at angle α at that time, and then the parts can be bonded without passing the k vector through the bonding surface. When four such component parts are formed, a bonded 2×2 mosaic shown in Figure 12 can be fabricated. For more component parts, this method can be extended to larger mosaics to fabricate, for example, larger composite optical crystal material structures.

[0052] Therefore, in various embodiments (for example, shown in Figures 10, 11, 12, 13, and 15), a portion of the optical crystalline material can be removed from the optical crystalline material (in bulk, as in Figure 10, or individually, as in Figure 15) to form a first and second inclined surface, the first and second inclined surfaces being aligned with one dimension (e.g., thickness) of the first optical crystalline material. Using this technique, the input light can be made to be, for example, not parallel to the diffusion junction surface in any direction. In some embodiments, as shown in Figures 13 and 14, further portions of the optical crystalline material can be removed from multiple optical crystalline materials to form a third and fourth inclined surface, the third inclined surface being parallel to the fourth inclined surface.

[0053] Figure 16 shows one exemplary application of the technique described herein, according to various embodiments. In one embodiment, the technique may be used in an apparatus including a laser 1601 configured to produce a beam of light 1650 having a first frequency. The apparatus may include a composite optical crystal material 1602 comprising a plurality of diffusion-bonded optical crystal materials, as described herein. The composite optical crystal material 1602 receives a beam of light at a phase-matching angle (e.g., into the interior of the diffusion-bonded crystal) to produce light 1651 having a second frequency. To achieve phase matching, light 1650 can be incident on aperture A at an angle θext, but as described above, the phase-matching angle is relative to the internal orientation of the crystal axis. Advantageously, aperture A can be increased using the technique described herein. Thus, A is highlighted for illustrative purposes in Figure 16. The laser 1601 produces a beam of light 1650 having a first frequency. The beam of light 1650 is coupled to the input planar surface of a composite optical crystal material containing multiple diffusion-bonded optical crystal materials to increase the aperture size. The composite optical crystal material receives the beam of light at a phase-matching angle (e.g., inside the crystal) to generate light 1651 having a second frequency. The beam of light 1651 having the second frequency is output from the second planar surface of the composite optical crystal material. The beam of light 1651 can be coupled to the target system 1603. One exemplary target system is, for example, a nuclear fusion system.

[0054] Figure 17 shows another exemplary application of the technique described herein by various embodiments. This example shows an optical switch (also known as an electro-optic switch or light bulb) 1700. The optical switch 1700 includes a diffusion-bonded optical crystal as described herein to increase the length of the optical switch 1700. The optical switch 1700 further includes conductors 1710-1711 (e.g., anode and cathode). Conductor 1710 is connected to a first voltage (V1), and conductor 1711 is connected to a second voltage (V2). In some embodiments, the diffusion-bonded optical crystal is a BBO crystal. In this example, the refractive index of the crystal depends on the voltage applied across the conductor. When polarized light (e.g., polarized 45 degrees from the perpendicular) enters the optical switch, the polarization of the light may be altered, and therefore the beam intensity may be hindered when it passes through a polarizer (not shown) after the crystal based on the voltage between V1 and V2, for example. Advantageously, diffusion-junctioned optical crystals can increase the length L of the optical switch, which improves the performance of the switch by increasing the sensitivity of the element to voltage (for example, by reducing the voltage required for modulation).

[0055] Figure 18 shows another exemplary embodiment. In this example, a heating system 1800 (e.g., an oven) houses a plurality of optical crystalline materials 1801a-n and 1802a-n, including at least a first optical crystalline material 1801a and a second optical crystalline material 1802a having the same material type. Each of the optical crystalline materials 1801a-n and 1802a-n has a crystal orientation and a plurality of planar surfaces (e.g., flat planar surfaces). The optical crystalline materials 1801a-n and 1802a-n are arranged so that their planar surfaces are in contact, including the first planar surface of at least the first optical crystalline material being in contact with the first planar surface of the second optical crystalline material. Furthermore, the crystal orientations of the optical crystalline materials 1801a-n and 1802a-n are aligned. Furthermore, the heating system 1800 heats the optical crystalline materials 1801a-n and 1802a-n to diffuse bond the contacting planar surfaces. For example, the first planar surface of the first optical crystal material is heated and diffusely bonded to the first planar surface of the second optical crystal material.

[0056] (Further exemplary embodiments) Each of the non-limiting features in the following examples may be independent or combined with one or more of the other features in the examples below in various substitutions or combinations. In various embodiments, the disclosure may be implemented as an apparatus or method.

[0057] In one embodiment, the present disclosure includes a diffusion-bonded nonlinear optical element.

[0058] In one embodiment, the disclosure includes a laser system comprising a laser and a plurality of diffusion-bonded nonlinear optical materials.

[0059] In one embodiment, the present disclosure includes a fusion reactor comprising a laser system comprising a laser and a plurality of diffusion-bonded nonlinear optical materials.

[0060] In one embodiment, the diffusion-bonded nonlinear optical element or material is a diffusion-bonded LBO crystal.

[0061] In one embodiment, diffusion-bonded nonlinear optical elements or materials are bonded along a plane that forms an angle with the optical beam axis.

[0062] In one embodiment, light is coupled at an angle to the plane of one or more diffusion junctions between nonlinear optical materials, passing through diffusely bonded nonlinear optical elements or materials.

[0063] In another embodiment, the disclosure includes diffusion bonding of LBO or other optical materials, particularly nonlinear materials, to increase the length, for example, to obtain a piece with ends joined together.

[0064] In another embodiment, the disclosure includes diffusion bonding of LBOs or other optical materials, particularly nonlinear materials, having a bonding angle that is intentionally distorted or tilted from the direction of the desired optical beam axis so as not to pass the beam directly through the bonding line, and which can be tilted by more than 1 degree and less than 45 degrees. Advantageously, this bonding angle can be between 0.25 and 25 degrees when the objects of interest are bonded to increase the aperture. For angles much smaller than the minimum in this range, the projection of the bonding surface onto the beam plane spreads by less than 1 millimeter when bonding pieces that are millimeters to tens of millimeters thick. Angles of tens of degrees mean that a considerable amount of material is lost when tilting the surface. In some cases, the angle is about 10 degrees, which is the angle to light propagation that avoids passing along the seam of the bonding line, and which generally appears as a streak in the beam. In some cases, a bonding angle of 10 degrees may be a natural angle to bonding without consideration of the problem of the beam passing directly through the bonding, but rather a natural direction for the phase matching angle.

[0065] In one embodiment, the diffusion junction is inclined with respect to the plane into which the input wave is incident (for example, Figure 4).

[0066] In another embodiment, a rectangular nonlinear optical material (e.g., LBO) is joined and then cut again at an angle (e.g., Figure 5).

[0067] In one embodiment, nonlinear optical materials (e.g., LBO) are joined in series (e.g., linear column) in a single joining step to predominantly increase the aperture in a direction perpendicular to the direction of light intended to pass through the joined pieces.

[0068] In one embodiment, a nonlinear optical material (e.g., LBO) is joined in two dimensions to increase the aperture.

[0069] In one embodiment, a series (e.g., a linear sequence) of diffusion-bonded nonlinear optical materials is bonded in two dimensions to three or more diffusion-bonded nonlinear optical materials in one or both dimensions.

[0070] Diffusion bonding of LBO as shown in Figure 6, or diffusion bonding of other optical materials, particularly nonlinear materials as described above in two directions, is achieved by constructing a block of three or more parts.

[0071] The combination of the method in Figure 5 or Figure 6 and the method in Figure 2 demonstrates how diffusion bonding can create integrated parts with a larger area and volume than any single piece.

[0072] In one embodiment, the present disclosure includes a method comprising: housing at least a first optical crystalline material and a second optical crystalline material having the same material type, wherein each of the first optical crystalline material and the second optical crystalline material has a crystal orientation and a plurality of planar surfaces; arranging the first optical crystalline material and the second optical crystalline material such that a first planar surface of the first optical crystalline material is in contact with a first planar surface of the second optical crystalline material and the crystal orientation of the first optical crystalline material is aligned with the crystal orientation of the second optical crystalline material; and heating the first optical crystalline material and the second optical crystalline material to diffuse bond the first planar surface of the first optical crystalline material with the first planar surface of the second optical crystalline material.

[0073] In one embodiment, the present disclosure includes a method of arranging a plurality of optical crystalline materials having the same material type, wherein each of the plurality of optical crystalline materials has a crystal orientation and a plurality of planar surfaces, and one or more planar surfaces of each optical crystalline material are in contact with another planar surface of an adjacent optical crystalline material, and the crystal orientations of the plurality of optical crystalline materials are aligned; and heating the plurality of optical crystalline materials to diffuse bond the contacting planar surfaces of the plurality of optical crystalline materials.

[0074] In one embodiment, the present disclosure includes a method comprising heating a plurality of optical crystal materials to form a composite optical crystal material, wherein each optical crystal material of the plurality of optical crystal materials has the same material type, a plurality of planar surfaces, and the same crystal orientation relative to the planar surfaces, the crystal orientations of the plurality of optical crystal materials are aligned, each of the plurality of optical crystal materials has a height and width greater than its thickness, and one or more planar surfaces of each optical crystal material along one or more of the thickness and height or width are diffusion-bonded to another planar surface of another optical crystal material of the plurality of optical crystal materials along one or more of the thickness and height or width, and the composite optical crystal material has opposing parallel planar surfaces having a surface area greater than the surface area of ​​each of the plurality of planar surfaces of the plurality of optical crystal materials.

[0075] In one embodiment, the present disclosure includes an apparatus comprising a laser configured to generate a beam of light having at least a first frequency, and a composite optical crystal material comprising a plurality of diffusion-bonded optical crystal materials, the composite optical crystal material receiving the beam of light at a phase-matching angle to generate light having at least a second frequency.

[0076] In one embodiment, the present disclosure includes a method in which a laser generates a beam of light having a first frequency, and couples the beam of light to a first planar surface of a composite optical crystal material, wherein the composite optical crystal material comprises a plurality of diffusion-bonded optical crystal materials, the composite optical crystal material receives the beam of light at a phase-matching angle to generate light having a second frequency, and outputs a beam of light having a second frequency from a second planar surface of the composite optical crystal material.

[0077] In one embodiment, the present disclosure includes an apparatus comprising a laser and diffusion-bonded optical crystalline material means for receiving light and generating output light.

[0078] The embodiments in paragraphs

[0072] to

[0077] are described in the following paragraphs, respectively.

[0079] ~Can be combined with any one or more of the items in

[0128] .

[0079] In one embodiment, multiple optical crystal materials have the same material type.

[0080] In one embodiment, each of the multiple optical crystal materials has multiple planar surfaces, and one or more planar surfaces of each optical crystal material are in contact with another planar surface of an adjacent optical crystal material.

[0081] In one embodiment, each of the multiple optical crystal materials has a crystal orientation, and the crystal orientations of the multiple optical crystal materials are aligned.

[0082] In one embodiment, the first optical crystal material further has a second planar surface of a plurality of surfaces, the second optical crystal material further has a second planar surface of a plurality of surfaces, the first planar surface of the first optical crystal material is aligned with the first planar surface of the second optical crystal material, and the second planar surface of the first optical crystal material and the second planar surface of the second optical crystal material form a composite surface that is larger than any one of the plurality of planar surfaces.

[0083] In one embodiment, the cross-sectional areas of the diffusion-bonded first optical crystal material and the second optical crystal material are greater than the cross-sectional areas of the first optical crystal material and the cross-sectional areas of the second optical crystal material.

[0084] In one embodiment, the first optical crystal material and the second optical crystal material each have a plurality of opposing parallel surfaces, and the crystal orientation is perpendicular to two or more of the parallel surfaces.

[0085] In one embodiment, the first optical crystal material and the second optical crystal material each have a plurality of parallel surfaces, and the crystal orientation is angled with respect to at least two opposing parallel surfaces.

[0086] In one embodiment, the diffusion junction between the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material is configured at an angle with respect to at least one axis of light propagation between the crystal orientation of the first optical crystal material and the aligned crystal orientation of the second optical crystal material. In one embodiment, the angle is between 0.25 degrees and 45 degrees.

[0087] In one embodiment, the crystal orientation of the first optical crystal material is aligned with the crystal orientation of the second optical crystal material within 80 arc seconds.

[0088] In one embodiment, the crystal orientation of the first optical crystal material is aligned with the crystal orientation of the second optical crystal material within 40 arc seconds.

[0089] In one embodiment, the first optical crystal material has a first crystal axis orientation, and the second optical crystal material has a second crystal axis orientation that is aligned with the first crystal axis orientation during the heating process.

[0090] In one embodiment, the method further includes determining a first crystal axis orientation for a first optical crystal material and a second crystal axis orientation for a second optical crystal material.

[0091] In one embodiment, the first optical crystal material and the second optical crystal material are cut from the same crystal boule.

[0092] In one embodiment, the first optical crystal material and the second optical crystal material are cut from various different crystal boules.

[0093] In one embodiment, the heating raises the temperatures of the first and second optical crystal materials to below the melting temperature of the crystals, so that the molecules of the first and second optical crystal materials become mobile and intermesh the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material.

[0094] In one embodiment, the heating raises the temperature of the first optical crystal material and the second optical crystal material to a temperature between 60% and 90% of the melting point of the first optical crystal material and the second optical crystal material.

[0095] In one embodiment, the method further includes polishing the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material before forming the diffusion junction.

[0096] In one embodiment, the polishing produces a 0-0 scratch-dig surface quality and a reflected wavefront distortion in lambda divided by 10 at 633 nm.

[0097] In one embodiment, the diffusion junction between the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material is offset at an angle from one or more crystal axes.

[0098] In one embodiment, the diffusion junction between the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material is offset at an angle with respect to light propagation in the first optical crystal material and the second optical crystal material.

[0099] In one embodiment, the angle is between 0.25 degrees and 25 degrees.

[0100] In one embodiment, the first optical crystal material has height, width, and thickness, and the second optical crystal material has the same thickness as the first optical crystal material and one or more of the same height or the same width.

[0101] In one embodiment, the first optical crystal material and the second optical crystal material are rectangular cubes.

[0102] In one embodiment, one or more of the height and width of the first optical crystal material are greater than the thickness, and the first surface of the first optical crystal material is formed by the height or width and the thickness of the first optical crystal material.

[0103] In one embodiment, the method further includes cutting a rotated substructure from a diffusion-bonded first optical crystal material and a second optical crystal material such that the diffusion bond is inclined with respect to at least one surface of the diffusion-bonded first optical crystal material and second optical crystal material.

[0104] In one embodiment, the first optical crystal material is diffusion-bonded to the second optical crystal material such that at least one combined surface of the diffusion-bonded first optical crystal material and the second optical crystal material is larger than the height, width, and thickness of the first optical crystal material and the second optical crystal material.

[0105] In one embodiment, the first optical crystal material is diffusion-bonded to the second optical crystal material such that the length of the diffusion-bonded first optical crystal material and second optical crystal material is greater than the height, width, and thickness of the first optical crystal material and second optical crystal material.

[0106] In one embodiment, at least one of the first optical crystal material and the second optical crystal material is trapezoidal.

[0107] In one embodiment, the first optical crystal material and the second optical crystal material are nonlinear optical crystal materials.

[0108] In one embodiment, the first optical crystal material and the second optical crystal material are lithium triborate (LBO).

[0109] In one embodiment, the first optical crystal material and the second optical crystal material are barium beta-borate (BBO).

[0110] In one embodiment, the first optical crystal material and the second optical crystal material are combined in such a way as to increase the aperture area.

[0111] In one embodiment, the first optical crystal material and the second optical crystal material are combined in such a way that their length increases.

[0112] In one embodiment, the multiple optical crystal materials are rectangular in shape.

[0113] In one embodiment, the multiple optical crystal materials are trapezoidal in shape.

[0114] In one embodiment, multiple optical crystal materials are cut from the same crystal boolean.

[0115] In one embodiment, multiple optical crystal materials are cut from various different crystal boules.

[0116] In one embodiment, the method further includes making a first plurality of cuts of a first optical crystal material having height and width in order to separate the plurality of optical crystal materials before heating.

[0117] In one embodiment, the method further includes removing portions of optical crystalline material from a plurality of optical crystalline materials to form a first inclined surface and a second inclined surface.

[0118] In one embodiment, the second inclined surface is parallel to the first inclined surface.

[0119] In one embodiment, removing a portion of the optical material involves making multiple cuts.

[0120] In one embodiment, the method further comprises removing a second portion of an optical crystalline material from a plurality of optical crystalline materials to form a third inclined surface and a fourth inclined surface, wherein the third inclined surface is parallel to the fourth inclined surface.

[0121] In one embodiment, removing a portion of the optical material includes grinding the first optical crystal material.

[0122] In one embodiment, removing a portion of the optical material includes polishing the first optical crystal material.

[0123] In one embodiment, the removal of a portion of the optical material is performed in a single optical crystal material, and then a first plurality of cuts are made in the single optical crystal material to create a plurality of optical crystal materials.

[0124] In one embodiment, the second inclined surface is parallel to the first inclined surface.

[0125] In one embodiment, the removal of a portion of the optical material is performed individually for multiple optical crystal materials.

[0126] In one embodiment, one or more diffusion junctions between one or more planar surfaces of each optical crystal material and another planar surface of another optical crystal material are inclined with respect to opposing parallel planar surfaces of the composite optical crystal material.

[0127] In one embodiment, the diffusion-bonded optical crystal material means receives light having at least a first frequency and outputs light having at least a second frequency different from the first frequency.

[0128] In one embodiment, the diffusion-bonded optical crystal material means is part of an optical switch.

[0129] It should be noted that the specific features, advantages, and concepts described above are presented in relation to LBO and second harmonic generation. However, it will be obvious to those skilled in the art that the same concepts apply to other linear optical crystalline materials or nonlinear optical crystalline materials such as BBO, and to wavelengths other than those mentioned in the examples. The same concepts also apply to other linear applications of these materials or to other sum-frequency generation processes such as third harmonic generation or fourth harmonic generation, but not limited to these. The same concepts also apply to parametric processes and / or electro-optic applications, such as downconversion.

[0130] The above description illustrates various embodiments of the Disclosure, along with examples of how aspects of a particular embodiment may be carried out. These examples should not be considered sole embodiments, but are presented to demonstrate the flexibility and advantages of a particular embodiment as defined by the following claims. Based on the above disclosure and the following claims, other arrangements, embodiments, forms, and equivalents may be used without departing from the scope of the Disclosure as defined by the claims.

Claims

1. The heating system contains at least a first optical crystal material and a second optical crystal material having the same material type, wherein each of the first and second optical crystal materials has a crystal orientation and a plurality of planar surfaces. The first optical crystal material and the second optical crystal material are arranged such that the first planar surface of the first optical crystal material is in contact with the first planar surface of the second optical crystal material, and the crystal orientation of the first optical crystal material is aligned with the crystal orientation of the second optical crystal material. The first optical crystal material and the second optical crystal material are heated in order to diffuse bond the first planar surface of the first optical crystal material to the first planar surface of the second optical crystal material. Methods that include...

2. The method according to claim 1, wherein the first optical crystal material further has a second planar surface of the plurality of surfaces, the second optical crystal material further has a second planar surface of the plurality of surfaces, the first planar surface of the first optical crystal material is aligned with the first planar surface of the second optical crystal material, and the second planar surface of the first optical crystal material and the second planar surface of the second optical crystal material form a composite surface that is larger than any one of the plurality of planar surfaces.

3. The method according to claim 1, wherein the cross-sectional areas of the diffusion-bonded first optical crystal material and the second optical crystal material are greater than the cross-sectional areas of the first optical crystal material and the cross-sectional areas of the second optical crystal material.

4. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material each have a plurality of opposing parallel surfaces, and the crystal orientation is perpendicular to two or more of the parallel surfaces.

5. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material each have a plurality of parallel surfaces, and the crystal orientation is angled with respect to at least two opposing parallel surfaces.

6. The method according to claim 1, wherein the diffusion junction between the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material is configured at an angle with respect to at least one axis of light propagation with respect to the crystal orientation of the first optical crystal material and the aligned crystal orientation of the second optical crystal material.

7. The method according to claim 6, wherein the angle is between 0.25 degrees and 45 degrees.

8. The method according to claim 1, wherein the crystal orientation of the first optical crystal material is aligned with the crystal orientation of the second optical crystal material within 80 arc seconds.

9. The method according to claim 1, wherein the crystal orientation of the first optical crystal material is aligned with the crystal orientation of the second optical crystal material within 40 arc seconds.

10. The method according to claim 1, wherein the first optical crystal material has a first crystal axis orientation, and the second optical crystal material has a second crystal axis orientation that is aligned with the first crystal axis orientation during heating.

11. The method according to claim 10, further comprising determining the first crystal axis orientation for the first optical crystal material and the second crystal axis orientation for the second optical crystal material.

12. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material are cut from the same crystal boule.

13. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material are cut from various different crystal boules.

14. The method according to claim 1, wherein the heating raises the temperatures of the first optical crystal material and the second optical crystal material to a temperature below the melting temperature of the crystals, such that the molecules of the first optical crystal material and the second optical crystal material become mobile and the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material become intertwined.

15. The method according to claim 1, wherein the heating is performed to raise the temperature of the first optical crystal material and the second optical crystal material to a temperature between 60% and 90% of the melting points of the first optical crystal material and the second optical crystal material.

16. The method according to claim 1, further comprising polishing the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material before forming the diffusion junction.

17. The method according to claim 16, wherein the polishing produces a 0-0 scratch-dig surface quality and a reflected wavefront distortion in lambda divided by 10 at 633 nm.

18. The method according to claim 1, wherein the diffusion junction between the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material is offset at an angle from one or more crystal axes.

19. The method according to claim 1, wherein the diffusion junction between the first planar surface of the first optical crystal material and the first planar surface of the second optical crystal material is offset at an angle with respect to light propagation in the first optical crystal material and the second optical crystal material.

20. The method according to claim 1, wherein the angle is between 0.25 degrees and 25 degrees.

21. The method according to claim 1, wherein the first optical crystal material has a height, width, and thickness, and the second optical crystal material has the same thickness as the first optical crystal material and one or more of the same height or the same width.

22. The method according to claim 21, wherein the first optical crystal material and the second optical crystal material are rectangular cubes.

23. The method according to claim 21, wherein one or more of the height and width of the first optical crystal material are greater than the thickness, and the first surface of the first optical crystal material is formed by the height or width and the thickness of the first optical crystal material.

24. The method according to claim 22, further comprising cutting a rotated substructure from the diffusion-bonded first optical crystal material and the second optical crystal material such that the diffusion bond is inclined with respect to at least one surface of the diffusion-bonded first optical crystal material and the second optical crystal material.

25. The method according to claim 21, wherein the first optical crystal material is diffusion-bonded to the second optical crystal material such that at least one combined surface of the diffusion-bonded first optical crystal material and the second optical crystal material is larger than the height, width, and thickness of the first optical crystal material and the second optical crystal material.

26. The method according to claim 21, wherein the first optical crystal material is diffusion-bonded to the second optical crystal material such that the length of the diffusion-bonded first optical crystal material and second optical crystal material is greater than the height, width, and thickness of the first optical crystal material and second optical crystal material.

27. The method according to claim 1, wherein at least one of the first optical crystal material and the second optical crystal material is trapezoidal.

28. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material are nonlinear optical crystal materials.

29. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material are lithium triborate (LBO).

30. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material are barium beta-borate (BBO).

31. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material are combined to increase the aperture area.

32. The method according to claim 1, wherein the first optical crystal material and the second optical crystal material are combined to increase the length.

33. The arrangement involves arranging multiple optical crystal materials of the same material type, each of which has a crystal orientation and multiple planar surfaces, with one or more planar surfaces of each optical crystal material in contact with another planar surface of an adjacent optical crystal material, and the crystal orientations of the multiple optical crystal materials being aligned. Heating the plurality of optical crystal materials so that the contacting planar surfaces of the plurality of optical crystal materials are diffusely bonded. Methods that include...

34. This includes heating multiple optical crystal materials to form a composite optical crystal material. Each of the aforementioned plurality of optical crystal materials has the same material type, a plurality of planar surfaces, and the same crystal orientation with respect to the planar surfaces. The crystal orientations of the plurality of optical crystal materials are aligned. Each of the aforementioned plurality of optical crystal materials has a height and width greater than its thickness. One or more planar surfaces of each optical crystal material along the thickness and / or height or width are diffusion bonded to another planar surface of another optical crystal material of the plurality of optical crystal materials along the thickness and / or height or width. The composite optical crystal material has opposing parallel planar surfaces having a surface area larger than the surface area of ​​each of the plurality of planar surfaces of the plurality of optical crystal materials. method.

35. The method according to claim 34, wherein the plurality of optical crystal materials are rectangular.

36. The method according to claim 34, wherein the plurality of optical crystal materials are trapezoidal.

37. The method according to claim 34, wherein the plurality of optical crystal materials are cut from the same crystal boule.

38. The method according to claim 34, wherein the plurality of optical crystal materials are cut from various different crystal boules.

39. The method according to claim 34, further comprising, before heating, performing a first plurality of cuts of the first optical crystal material having the height and the width in order to separate the plurality of optical crystal materials.

40. The method according to claim 34, further comprising removing portions of optical crystalline material from the plurality of optical crystalline materials to form a first inclined surface and a second inclined surface.

41. The method according to claim 40, wherein the second inclined surface is parallel to the first inclined surface.

42. The method according to claim 40, wherein removing a portion of the optical material includes performing a plurality of cuts.

43. The method according to claim 40, further comprising removing a second portion of optical crystalline material from the plurality of optical crystalline materials to form a third inclined surface and a fourth inclined surface, wherein the third inclined surface is parallel to the fourth inclined surface.

44. The method according to claim 40, wherein removing a portion of the optical material includes grinding the first optical crystal material.

45. The method according to claim 40, wherein removing a portion of the optical material includes polishing the first optical crystal material.

46. The method according to claim 40, wherein the removal of a portion of the optical material is performed in a single optical crystal material, and thereafter, a first plurality of cuts are made in the single optical crystal material to produce the plurality of optical crystal materials.

47. The method according to claim 46, wherein the second inclined surface is parallel to the first inclined surface.

48. The method according to claim 40, wherein the removal of a portion of the optical material is performed individually in the plurality of optical crystal materials.

49. The method according to claim 34, wherein one or more diffusion junctions between the one or more planar surfaces of each optical crystal material and the other planar surface of the other optical crystal material are inclined with respect to the opposing parallel planar surfaces of the composite optical crystal material.

50. A laser configured to generate a beam of light having at least a first frequency, A composite optical crystal material comprising a plurality of diffusion-bonded optical crystal materials, wherein the composite optical crystal material receives a beam of light at a phase-matching angle and generates light having at least a second frequency. A device equipped with the following features.

51. The apparatus according to claim 50, wherein the plurality of optical crystal materials have the same material type.

52. The apparatus according to claim 50, wherein each of the plurality of optical crystal materials has a plurality of planar surfaces, and one or more planar surfaces of each optical crystal material are in contact with another planar surface of an adjacent optical crystal material.

53. The apparatus according to claim 50, wherein each of the plurality of optical crystal materials has a crystal orientation, and the crystal orientations of the plurality of optical crystal materials are aligned.

54. In a laser, generating a beam of light having at least a first frequency, The coupling involves coupling the beam of light to a first planar surface of a composite optical crystal material, wherein the composite optical crystal material comprises a plurality of diffusion-bonded optical crystal materials, and the composite optical crystal material receives the beam of light at a phase-matching angle and generates light having at least a second frequency. A beam of light having the second frequency is output from the second planar surface of the composite optical crystal material. Methods that include...

55. Lasers and, A diffusion-bonded optical crystal material means for receiving light and generating output light, A device equipped with the following features.

56. The apparatus according to claim 55, wherein the diffusion-bonded optical crystal material means receives light having at least a first frequency and outputs light having at least a second frequency different from the first frequency.

57. The apparatus according to claim 55, wherein the diffusion-bonded optical crystal material means is part of an optical switch.

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