SPECTRAL SPLITTER EQUIPMENT

Abstract

A spectrum splitter for transforming at least one initial light beam (R0) from a light source (F) into more than two light beams, or vice versa, comprising a first polarization beam splitter (P1) that divides the initial light beam (R0) into two orthogonally polarized beams (R1 and R2); two optical elements (O1 and O2) through which the aforementioned two orthogonally polarized beams (R1 and R2) pass; and a second and a third polarization beam splitter (P21 and P22) that, in turn, divide the two orthogonally polarized light beams (R1 and R2) into four respective output beams (R11 and R12) and (R21 and R22). Each of the optical elements (O1 and O2) is birefringent, and the birefringence of both elements depends on the wavelength.

Description

SPECTRAL SPLITTER EQUIPMENT IVIA / a / ZUZZ / UI 430Ί FIELD OF APPLICATION OF THE INVENTION The field of application of the present invention falls within the sector of the industry dedicated to the manufacture of devices and components for light emission equipment, for example laser, led or other technologies. BACKGROUND OF THE INVENTION As is well known, when light passes through a birefringent medium, the beam can be split into two polarization components with respect to the optical axis of the medium. Each component experiences different refractive indices, resulting in a relative phase shift between the two and thus inducing a change in the polarization state of the light. Because all media are dispersive, meaning they have different refractive indices for different wavelengths, birefringence is generally also dispersive. Therefore, the change in polarization state depends on the wavelength. Thus, it is possible to distinguish, filter, separate, or combine different spectral components of light using appropriate configurations of birefringent materials and polarizing beam splitters. In the simplest case, a birefringent crystal is placed between two polarizers. This filter is known as a Lyot filter.Due to the fact that a phase delay between the polarization states of light is periodic by multiples of π, so is the periodic transmission of the filter with respect to wavelength. This effect can be very practical for increasing power in certain equipment. For example, laser technology is widely used in industry, typically for industrial laser processes, primarily for cutting or welding. Most of these are done with fiber optic lasers or disc lasers. In any case, the important thing in these types of applications is to have energy density that can be concentrated in very small spots. Energy density is achieved by scaling up power or decreasing the laser spot size. However, in diode applications, the entire increase in density is based on increased power, because the spot size cannot be made smaller due to the low beam quality on the slow axis. To date, the state of the art in laser technology for increasing power / capacity only allows the summation of beams from two diodes by polarization or from several diodes per wavelength. Therefore, it would be desirable to develop a new technique that allows increasing this power by summing more than two of these diodes. The objective of the present invention is to develop such a new technique, enabling the simple delivery of an energy density two to four times greater. In the current technique, to combine two laser beams from two diodes, the two identical diodes are positioned perpendicularly and focused, with different polarizations of their light (one vertical and the other horizontally polarized using a wave retarder). These beams are then placed in front of a polarization beam splitter, so that they enter and exit the splitter together in the same direction, as one beam passes through and the other is reflected, but retaining their different polarizations. This means that the combined beams cannot be recombined to increase the output laser power, which would be desirable. Each laser consists of an active laser region, also called the gain region, in which the supplied energy is converted into coherent radiation by stimulated emission. A laser resonator is needed to ensure that some of the emerging radiation is returned to the gain region. Therefore, it contains at least one feedback element, typically a semi-transparent mirror. This resonator, through its geometry and physical properties, determines the feedback characteristics of the laser light, specifically its spatial profile, wavelength, bandwidth, and polarization. The estimated achievable characteristics depend on the material gain and resonators and are generally inversely correlated with each other and with the achievable output power. Improvements to one chosen parameter thus tend to degrade others. Of particular practical importance are semiconductor lasers, as they are very small, directly convert electrical energy into light, have high efficiency, and can be manufactured -3 using established semiconductor manufacturing techniques and are therefore inexpensive in large quantities. The resonator is integrated in tandem by reflective layers applied to the end faces and / or epitaxially incorporated refractive index gratings. Currently, the achievable power output or power density is still too low for many interesting applications. This is because the light is generated in volumes significantly smaller than 1 mm³, leading to power densities that would destroy the component if increased further. Increasing the volume is not a solution because modal selectivity decreases and, as a result, beam quality deteriorates, keeping power density approximately constant. A long-practiced approach to at least double the output power involves superimposing two orthogonal laser polarizations using a polarization beam splitter, as explained above, so that the resulting light contains crossed polarizations and can only be boosted to such double the power. The objective of the present invention is, therefore, the development of a spectral splitter to increase the power, and therefore the efficiency of the use of light beams in multiple industrial applications, for example in laser equipment to significantly increase said power by combining pairs of laser beams, allowing to reach an exponential increase of the same, depending on the number of pairs that are combined. Furthermore, and as a reference to the current state of the art, it should be noted that, although there are documents and literature that disclose concepts in this field, at least on the part of the applicant, it is considered that none of them, taken separately or in combination, discloses equipment like the one described here or with technical, structural and constitutive characteristics equal or similar to those presented by the one claimed here. In this regard, it is worth mentioning that (for example, according to document WO 03 / 055018) it is known that very compact external resonators can dramatically improve the beam quality of high-power diode lasers at medium to high powers. However, several of these lasers must be operated simultaneously for even higher beam power. -4 generally significantly reduces beam quality and the ability to generate small spotlights. The achievable power density remains virtually constant. To overcome this problem, Daneu et al. (Opt. Lett., Vol. 25, No. 6, pp. 405-407) and Sánchez-Rubio (US 6,192,062) proposed spectral multiplexing. This approach uses multiple laser sources, each operating at a different wavelength, so that they can be spatially overlapped by a suitably chosen element, usually a diffraction grating. Several other patent applications exist on this basis (e.g., WO 03 / 036766, WO 20 / 02091077). All these patents feature a central dispersive element (prism or grating) that divides the resonator in two. On one side of the element, the various laser emissions are collinear, meaning the beam cross-section and emission direction are nearly identical. On the other side of the element, the different beams are spatially dispersed by medium scattering or diffraction, so that a separate laser of the appropriate wavelength can be operated in each direction. Generally, this includes lasers with a feedback mirror in the common path, as this ensures that each gain region operates at precisely the correct wavelength, determined by the scattering. Common to these patents is the fact that the spectral distance of the wavelengths to be multiplexed is defined by the dispersion and geometry of the resonator. The dispersion in terms of wavelength by angle must be multiplied by the emitter spacing angle divided by the distance to the dispersion element. For dense spectral multiplexing, large configurations are obtained, or for a given resonator footprint and dispersion, a spectral step size typically greater than 1 nm results in neighboring emitters. Furthermore, it is well known that most highly dispersive networks have only low diffraction efficiency and / or spectral acceptance and / or low damage thresholds, making practical implementation quite difficult. OBJECT OF THE INVENTION The invention, as stated in the present descriptive specification, relates to a spectrum splitter that provides advantages and characteristics, which are described in more detail below. -5 ahead, which represent an improvement over the current state of the art within their field of application. More specifically, the object of the invention focuses on a spectrum splitter that, based on the principle of a Lyot filter, allows increasing the power density of a beam from a light source, for example a laser, through the linear superposition of two pairs of beams combined by orthogonal polarization, by using birefringent and / or dispersive optical elements, for example calcite crystal with the necessary thickness to modify the wavelength in a controlled manner, causing both beams to again present the same polarization, allowing their linear superposition, which, in turn, allows the process to be repeated in cascade, recombining the linearly superimposed beams with other beams subjected to the same effect, and where the device comprises an optical assembly plate to carry out said effect by including additional elements,such as an external resonator that provides a larger cavity and a specific resonance condition, depending on each need, on the output beam obtained. DETAILED DESCRIPTION OF THE INVENTION The spectral splitter equipment proposed by the invention is thus configured as the optimal solution to achieve the objectives indicated above, with the characterizing details that distinguish it being included in the final claims that accompany this description. Specifically, the invention proposes, as previously mentioned, a spectrum splitter that, based on the principle of a Lyot filter, allows increasing the power density of a beam from a light source, for example a laser, through the linear superposition of two pairs of beams combined by orthogonal polarization. This is achieved using birefringent and dispersive optical elements, such as calcite crystals with the necessary thickness to modify the wavelength in a controlled manner, causing both beams to exhibit the same linear polarization and allowing their linear superposition. This, in turn, allows the process to be repeated in a cascade, recombining the linearly superimposed beams with other beams subjected to the same effect. The device comprises an optical assembly plate to carry out this effect through the inclusion of additional elements.such as an external resonator that provides greater, -6cavity and a specific resonance condition, depending on each need, on the output beam obtained. To this end, and more specifically, the equipment proposed by the invention is a spectral splitter for an initial light beam into more than two light beams, essentially comprising: - a first polarization beam splitter, which divides said light into two orthogonally polarized beams; - two optical elements, traversed respectively by the aforementioned two polarized beams; and - a second and a third polarization beam splitter, which, in turn, divide the two polarized light beams into respective four output beams, each of said optical elements being birefringent and the birefringence of both elements being wavelength dependent. Furthermore, in the preferred mode, the light from the resulting output light beams have at least one of the orthogonal polarization states or different wavelengths. Likewise, in a preferred embodiment of the equipment of the invention, the initial light beam passes through a birefringent and dispersive optical pre-element before entering the first polarizing beam splitter and, optionally, also passes through a previous polarizing beam splitter before entering the first polarizing beam splitter. Furthermore, in the preferred mode form, the initial light beam passes through a partially reflective mirror before entering, respectively, the pre-polarizing beam splitter or the birefringent pre-optical element. Optionally, at least one of the four output beams also passes through a third optical element that is birefringent and / or dispersive. Furthermore, it should be noted that, optionally, the spectrum splitter equipment can act as a beam combiner when used as described above with a reverse beam path. -7In this case, the equipment comprises more than one individual light source, preferably lasers or laser gain means, as light beams to be combined, these individual light sources being able to obtain feedback from the partially reflective mirror. In any case, the spectral splitter of the invention is configured as a plate comprising means for individual mutual control of the optical delay and / or dispersion of the first and second optical elements and, where applicable, of the previous optical element. In the preferred embodiment, each individual optical element comprises dispersive birefringent crystals of integer multiples of a basic thickness and an additional phase retardation comprising any or a combination of: - a single or a combination of multiple retarder plates - supports for individual tilting of the optical elements to adjust the delay - Babinet-Soleil wedges - a liquid crystal element with a delay controlled by its manufacturing process or an electric field. More specifically, in the preferred modality form, each individual optical element comprises at least two parts with a slight wedge, so that the effective thickness can be adjusted by displacing the two parts relative to each other. Furthermore, preferably, the relative optical delay is achieved using fewer physical elements than conceptually necessary, and where at least one element is traversed more than once. Finally, it should be noted that, in the preferred mode, the light source(s) can be a laser, semiconductor laser with or without low reflectivity, LED, laser bar, or bar stack. In any case, the light sources are an array and some of the polarizers are displacers. DESCRIPTION OF THE DRAWINGS To complement the description being made and in order to help with a better -8 Understanding the characteristics of the invention, this descriptive report is accompanied, as an integral part thereof, by a drawing, in which the following has been represented for illustrative and non-limiting purposes: Figure 1 shows a schematic representation of an example of a spectrum splitter implementation, showing the main parts and elements it comprises, as well as their arrangement. Figure 2 shows a schematic representation of the spectrum splitter equipment, in this case implemented as a beam combiner, showing the arrangement of its parts. Figure 3 shows a plan view of an example of the equipment as a beam combiner on an optical plate, showing the main parts and elements it comprises, as well as their arrangement, with the different light beams represented by dotted lines. Figures 4 and 5 show two perspective views of an example of a laser diode assembly modality, with passive and active cooling respectively, as an example of the light source comprising the spectral divider equipment that is the subject of the invention, showing its general configuration. Figures 6 and 7 show perspective views of the passively and actively cooled laser diodes shown in Figures 1 and 2, in this case represented on a water-cooled base. Figures 8 and 9 show perspective views of the passively and actively cooled laser diodes mounted on their water-cooled base, shown in the preceding figures, in this case including their respective circular lens adjustments. Figure 10 shows a perspective view of an example of the mounting of the optical element on an inclined support. PREFERRED MODALITY OF THE INVENTION -Ta in view of the aforementioned figures, and in accordance with the numbering adopted, one can appreciate in them an example of a non-limiting modality of the spectral dividing equipment of the invention, specifically an example as laser optical equipment, which comprises what is indicated and described in detail below. Thus, as shown in Figure 1, the spectral splitter (1) of the invention, applicable for transforming an initial light beam (R0), coming from a light source (F), into more than two light beams, essentially comprises: - a first polarization beam splitter (P1), which divides said initial light beam (R0) into two orthogonally polarized beams (R1 and R2); - two optical elements (O1 and O2), crossed respectively by the aforementioned two orthogonally polarized beams (R1 and R2); and - a second and a third polarization beam splitter (P21 and P22), which, in turn, divide the two orthogonally polarized light beams (R1 and R2) into four respective output beams (R11 and R12) and (R21 and R22), each of said optical elements (O1 and O2) being birefringent and the birefringence of both elements being wavelength dependent. Preferably, the light from the four output light beams (R11 and R12) and (R21 and R22) obtained have mutually at least one of the orthogonal polarization states or different wavelengths. Preferably, the initial light beam (RO) passes through a birefringent and dispersive optical pre-element (OO) before entering the first polarization beam splitter (P1). Alternatively, the initial light beam (RO) passes through a pre-polarization beam splitter (PO) before entering the first polarization beam splitter (P1). And, optionally, the initial light beam (RO) passes through a partially reflecting mirror (M) before entering the aforementioned pre-polarizing beam splitter (PO) or birefringent pre-optical element (OO). - 10In any case, preferably at least one of the four output beams (R11 and R12) and (R21 and R22) passes through a third optical element (O3) that is birefringent and / or dispersive. It should be noted that, optionally, in a modality form, the described spectral splitter equipment is susceptible to being applied as a beam combiner when used as described above with a reverse path of the beams, i.e., obtaining the sum of the two pairs of beams (R11 and R12) and (R21 and R22) generated by more than one individual light source (F) to combine into a single beam (RO). In such case, for obtaining the beams (R), the equipment comprises more than one individual light source (F), preferably lasers or laser gain means, which generate the light beams to be combined, said individual light sources being able to obtain feedback from the partially reflective mirror (M). In the preferred embodiment, the spectral splitter equipment (1) of the invention is implemented with at least one phase delay plate for individual mutual control of the optical delay and / or dispersion of the first and second optical elements (01, 02) and, where applicable, of the previous optical element (OO). Preferably, such a plate is a special type of phase plate called a quarter-waveplate. In the preferred embodiment, each individual optical element (O1, O2, OO) comprises dispersive birefringent crystals of integer multiples of a basic thickness and an additional phase retardation comprising any or a combination of: - a single or a combination of multiple retarder plates - supports for individual tilting of the optical elements to adjust the delay - Babinet-Soleil wedges - a liquid crystal element with a delay controlled by its manufacturing process or an electric field. More specifically, in the preferred modality form, each individual optical element comprises at least two parts with a slight wedge, so that the effective thickness can be adjusted by displacing the two parts relative to each other. Furthermore, preferably, the relative optical delay is achieved using fewer physical elements than conceptually necessary, and where at least one element is traversed more than once. It should be noted that the light source(s) (F) can be a laser, semiconductor laser with or without low reflectivity, LED, laser bar, or bar stack. In addition, the light sources (F) can be either point or material and some of the polarizers are displacers. Referring to Figure 3, an example of the implementation of the invention's equipment on a plate (3) can be seen, specifically an example in which four beams are combined in an output lens (L), where it can be seen how heat sinks (D) are also included. Referring to figures 3 to 9, an example of the light source (F) can be seen, specifically a semiconductor laser diode that is either passively cooled (figure 4) without water inside the assembly on a base (2) which is the one that has the cooling system, or actively cooled (figure 5) having two water channels that cool the diode. In Figures 6 and 7, both options of the diode as a light source (F) can be seen in its two versions, with passive and active cooling, respectively, once mounted on the water-cooled base (2). This base (2) is used for mounting the diode or light source (F) to the final plate (3), and is equipped with water connections (4) to adjust the tubes and cool the system. The actively cooled mount, shown in Figure 7, has more robust connections to allow for higher currents, although the height of both options is the same. Figures 8 and 9 show the assembly of both light source options (F), with passive and active cooling systems respectively, once the lenses are attached. - 12 circular ones (5), whose adjustment does not vary between one and the other, as it is identical. And finally, looking at figure 10, it can be seen how, preferably, the optical element (O), which is preferably a birefringent and / or dispersing crystal, for example of calcite, is mounted 5 on a support (6) inclined at 45°. Having sufficiently described the nature of the present invention, as well as the manner of putting it into practice, it is not considered necessary to make its explanation more extensive so that any expert in the field can understand its scope and the advantages that derive from it.

Claims

1A spectrum splitter, applicable for transforming at least one initial light beam (R0) from a light source (F) into more than two light beams or vice versa, is characterized by comprising: - a first polarization beam splitter (P1) that divides said initial light beam (R0) into two orthogonally polarized beams (R1 and R2); - two optical elements (O1 and O2) through which the aforementioned two orthogonally polarized beams (R1 and R2) pass respectively; and - a second and a third polarization beam splitter (P21 and P22) that, in turn, divide the two orthogonally polarized light beams (R1 and R2) into four respective output beams (R11 and R12) and (R21 and R22), wherein each of said optical elements (O1 and O2) is birefringent and the birefringence of both elements depends on the wavelength. 2.- The spectral splitter equipment according to claim 1, characterized in that the light from the four output light beams (R11 and R12) and (R21 and R22) obtained have mutually at least one of the orthogonal polarization states or different wavelengths. 3.- The spectral splitter equipment according to claim 2, characterized in that the initial light beam (RO) passes through a birefringent and dispersive optical pre-element (OO) before entering the first polarization beam splitter (P1). 4.- The spectral splitter equipment according to claim 2, characterized in that the initial light beam (RO) passes through a previous polarization beam splitter (PO) before entering the first polarization beam splitter (P1).

5. The spectrum splitter according to claim 2 or 3, characterized in that the initial light beam (RO) passes through a partially reflecting mirror (M) before entering the pre-polarizing beam splitter (PO) or the birefringent pre-optical element (OO). IVIA / a / ZUZZ / UI 430Ί 6. The spectrum splitter according to any of the preceding claims, characterized - 14 in that at least one of the four output beams (R11 and R12) and (R21 and R22) passes through a third optical element (O3) that is birefringent and / or dispersive. 7.- The spectral splitter equipment according to any of the preceding claims, characterized by comprising more than one individual light source (F) that generates beams (R11 and R12) and (R21 and R22) acting as a combiner into a single beam (RO) when a reverse path is applied to said beams. 8.- The spectral splitter equipment according to claim 7, characterized in that said individual light sources obtain feedback from the partially reflective mirror (M). 9.- The spectrum splitter equipment according to any of the preceding claims, characterized in that it comprises means for individual mutual control of the optical delay and / or dispersion of the first and second optical elements (01, 02) and, where applicable, of the previous optical element (OO).

10. The spectrum splitter according to claim 9, characterized in that each individual optical element (01, 02, OO) comprises dispersive birefringent crystals of integer multiples of a basic thickness and an additional phase retardation comprising any or a combination of: - a single or a combination of multiple retardation plates, - supports for individual tilts of the optical elements to adjust the retardation, - Babinet-Soleil wedges, - a liquid crystal element having a retardation controlled by its manufacturing process or an electric field. 11.- The spectral splitter according to claim 9, characterized in that each individual optical element (01, 02, OO) comprises at least two parts with a slight wedge, so that the effective thickness can be adjusted by displacing the two parts relative to each other.

12. The spectrum splitter according to any of the preceding claims, characterized in that the light source(s) are a laser diode, semiconductor laser with or without low reflectivity, LED, laser bar, or laser bar stack. - 1510 13. The spectral splitter equipment according to claim 9, characterized in that the light sources are an array and some of the polarizers are shifters.

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