Efficient laser system

Abstract

The present disclosure includes a laser semiconductor system including an n-side layer, an active region, a p-side waveguide layer, and a cladding layer.SOLUTION: The system also includes a plurality of sections having at least a front section at the front of the semiconductor and a back section at the back of the semiconductor. The thickness of the p-side waveguide layer may monotonically increase in each of the plurality of sections in the direction from the front section to the back section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001]

[0001] The present disclosure relates generally to efficient laser systems. [Background technology]

[0002] Aspects of the present disclosure relate to efficient laser systems. Various problems may exist with conventional solutions for sorting. In this regard, conventional laser systems may be expensive, cumbersome, and / or inefficient.

[0003]

[0003] The limitations and drawbacks of conventional systems and methods will become apparent to those skilled in the art through a comparison of such approaches with certain aspects of the present methods and systems described in the remainder of this disclosure with reference to the drawings. Summary of the Invention

[0004]

[0005] An efficient laser system is shown in and / or described in connection with at least one of the drawings and more fully set forth in the claims.

[0006] These and other advantages, aspects, and novel features of the present disclosure, as well as details of illustrated embodiments thereof, will be more fully understood from the following description and drawings.

[0005]

[0007] The various features and advantages of the present disclosure may be more readily understood by reference to the following detailed description when taken in conjunction with the accompanying drawings, in which like reference numerals designate like structural elements and in which: [Brief explanation of the drawings]

[0006] [Figure 1]

[0008] 1 is a block diagram illustrating a laser semiconductor system according to some embodiments of the present disclosure. [Figure 2]

[0009] 1 is an exemplary cross-sectional view of a laser semiconductor system 100 according to some embodiments of the present disclosure. [Figure 3]

[0010] 3 is an exemplary top view of the laser semiconductor system 100 shown in FIG. 2. [Figure 4A]

[0011] FIG. 4A illustrates an exemplary tapered transition 405 between the front section 152 and the rear section 154 in a top view of the laser semiconductor system 100, according to some embodiments of the present disclosure. [Figure 4B] FIG. 4B illustrates an exemplary tapered transition 410 between the front section 152 and the rear section 154 in a top view of the laser semiconductor system 100, according to some embodiments of the present disclosure. [Figure 4C] FIG. 4C illustrates an exemplary tapered transition 415 between the front section 152 and the rear section 154 in a top view of the laser semiconductor system 100, according to some embodiments of the present disclosure. [Figure 5]

[0012] 1 is a cross-sectional view of an exemplary multi-section of a laser semiconductor system 100 according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0007]

[0013] The following discussion provides various examples of efficient laser systems. Such examples are non-limiting, and the scope of the appended claims should not be limited to the particular examples disclosed. In the following discussion, the terms "example" and "eg" are non-limiting.

[0008]

[0014] The figures show the general style of the structure, and descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the present disclosure. Additionally, elements in the figures are not necessarily drawn to scale. For example, the dimensions of some elements in the figures may be exaggerated relative to other elements to help improve understanding of the examples discussed in this disclosure. The same reference numerals in different figures refer to the same elements.

[0009]

[0015] The term "or" means any one or more of the items in the list joined by "or." As an example, "x or y" means any element of the 3-element set {(x), (y), (x, y)}. As another example, "x, y, or z" means any element of the 7-element set {(x), (y), (z), (x, y), (x, z), (y, z), (x, y, z)}.

[0010]

[0016] The terms "comprises," "comprising," "includes," and / or "including" are "open-ended" terms that specify the presence of stated features but do not exclude the presence or addition of one or more other features.

[0011]

[0017] The terms "first," "second," and the like may be used herein to describe various elements, and these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, for example, a first element discussed in this disclosure could be referred to as a second element without departing from the teachings of the disclosure.

[0012]

[0018] Unless otherwise specified, the term "coupled" may be used to describe two elements that are in direct contact with each other or two elements that are indirectly connected by one or more other elements. For example, if element A is coupled to element B, element A may be in direct contact with element B or indirectly connected to element B by an intervening element C. Similarly, the terms "over" or "on" may be used to describe two elements that are in direct contact with each other or two elements that are indirectly connected by one or more other elements.

[0013]

[0019] In conventional laser systems, longitudinal spatial hole-burning and two-photon absorption can lead to reduced efficiency at high optical power and / or current levels in high-power lasers. These two effects can occur primarily in the front section of the device because the intracavity power level can increase exponentially during the round trip within the laser cavity. It may be desirable to address these shortcomings of conventional laser systems.

[0014]

[0020] Embodiments of the present disclosure may include a laser semiconductor system, where the system may include an n-side layer, an active region, a p-side waveguide layer, and a cladding layer. The embodiment may also include a plurality of sections, including at least a front section at the front of the semiconductor. The embodiment may also include a rear section at the rear of the semiconductor. According to various embodiments, the thickness of the p-side waveguide layer may monotonically increase in each of the plurality of sections in a direction from the front section to the rear section.

[0015]

[0021] According to various embodiments, the system may include an anti-reflective coating on the front and / or rear portion of the semiconductor and a highly reflective coating on the rear and / or front portion of the semiconductor. According to various embodiments, the system may include a tapered transition between two adjacent sections of the plurality of sections.

[0016]

[0022] According to various embodiments, the system may include lateral structuring. Embodiments may also include one or more NAM sections. According to various embodiments, the active region may be one of a bulk active region, a quantum well, or a quantum dot active region.

[0017]

[0023] Embodiments may also include an optical field confinement factor of the active region in the front section such that it differs from an optical field confinement factor of the active region in the rear section by at least 10%.Embodiments may also include a length of each of the plurality of sections such that it monotonically decreases in each of the sections in a direction from the rear section to the front section.

[0018]

[0024] According to various embodiments, the thickness of the p-side waveguide layer in the front section may differ from the thickness of the p-side waveguide layer in the rear section by more than 1 / 30 of the wavelength of the desired laser emission and by less than 1 / 3 of the wavelength. Embodiments may also include the resistivity of each of the plurality of sections such that it monotonically decreases in each of the sections in a direction from the rear section to the front section.

[0019]

[0025] According to various embodiments, the resistivity of the front section may differ from the resistivity of the rear section by more than 1 / 30 and less than 1 / 3 of the resistivity of the front section. Embodiments may also include the active region thickness being unequal for two or more sections of the plurality of sections. Embodiments may also include the active region thickness of each section of the plurality of sections being monotonically decreasing in each of the sections in a direction from the rear section to the front section.

[0020]

[0026] According to various embodiments, the laser semiconductor may be operable with reverse polarity. In some embodiments, an n-side layer may act as a waveguide, and the thickness of the n-side layer may monotonically increase or decrease in each of the sections from the front section to the rear section. According to various embodiments, the thickness of the p-side waveguide layer may be substantially the same across the sections.

[0021]

[0027] Referring now to Figure 1, Figure 1 is a block diagram illustrating a laser semiconductor system 100 according to some embodiments of the present disclosure. Laser semiconductor system 100 may refer to a semiconductor operable to generate coherent laser light through the process of stimulated admission within the semiconductor material. Laser semiconductor system 100 may generate a light beam having a particular wavelength.

[0022]

[0028] In some embodiments, the laser semiconductor system 100 may include an n-side layer 110 , an active region 120 , a p-side waveguide layer 140 , a cladding layer 130 , and a plurality of sections 150 .

[0023]

[0029] The n-side layer 110 may comprise an n-type semiconductor with excess electrons. The p-side layer 140 may comprise a p-type semiconductor with excess holes. The active region 120, sometimes called the gain medium, may be the central component where the process of stimulated emission may occur. Stimulated emission may lead to the amplification of light and the generation of a laser beam. The active region 120 may be a region where energy may be stored and then released in the form of photons. The active region 120 may be formed within a semiconductor material, such as a PN junction, where recombination of electrons and holes may lead to photon emission.

[0024]

[0030] The active region 120 may be designed to have a particular energy level structure that may enable efficient population inversion and stimulated emission at a desired wavelength. The active region 120 may determine the gain characteristics of the laser semiconductor 100 and / or may determine the output power and spectral characteristics of the laser semiconductor system 100.

[0025]

[0031] In some embodiments, the active region 120 may be one of a bulk active region, a quantum well active region, or a quantum dot active region.

[0032] A bulk active region may refer to an active region 120 that comprises a single, relatively thick layer of semiconductor material. This may be contrasted with other types of active regions 120, such as quantum well active regions, which may comprise multiple thin layers of semiconductor material.

[0026]

[0033] Quantum well and quantum dot active regions may be structures that utilize quantum confinement effects to provide certain advantages. Quantum well active regions may comprise multiple thin layers (wells) of semiconductor material with a lower bandgap, typically sandwiched between layers of higher bandgap material. Electrons and holes may be confined in one dimension to the wells, and this confinement may improve the efficiency of light emission and enable a narrower emission spectrum compared to bulk active regions.

[0027]

[0034] A quantum dot active region may comprise an array of small three-dimensional islands (dots) of lower bandgap semiconductor material embedded within a higher bandgap material. Electrons and holes may be confined in all three dimensions within the dots, which may enhance the efficiency of light emission and narrower emission spectra compared to bulk active regions and, in some cases, even quantum well active regions.

[0028]

[0035] In some embodiments, the optical field confinement factor of the active region 120 in the front section 152 may differ from the optical field confinement factor of the active region 120 in the rear section 154 by at least 10%.

[0029]

[0036] The confinement factor of the optical field within the active region of the laser may be a dimensionless parameter that quantifies the fraction of optical power or energy that may be confined within the active region 120. The confinement factor may indicate various laser performance characteristics, such as threshold current, efficiency, or temperature stability. The confinement factor may be tuned, for example, by selecting advantageous physical properties of the waveguide layer 140. The confinement factor may depend on the thickness of the active region 120. The confinement factor may depend on the refractive index difference between the active region 120 and the surrounding layers. The confinement factor may depend on the optical mode profile.

[0030]

[0037] Confinement and optical gain may be modified in the lateral dimensions to suppress higher order modes and / or enhance lower order modes. Lateral structuring may be applied to one or more sections 150. Lateral structuring may be combined with tapered transitions.

[0031]

[0038] The cladding layer 130 may be a layer of semiconductor material that surrounds the active region 120. Generally, there may be two cladding layers, one on top of the laser semiconductor system 100 and one on the bottom (only the cladding layer 130 is shown in the figures). The cladding layer 130 may have a lower refractive index than the active region 120. This difference in refractive index may create an optical waveguide, thus effectively trapping light generated in the active region 120 and directing it along the length of the laser cavity toward the ends of the laser semiconductor system 100. This may ensure efficient amplification of the light and may prevent the light from leaking sideways.

[0032]

[0039] The cladding layers 130 may help confine current to the active region 120. This may be important for ensuring efficient injection of electrons and holes into the active region 120, where they may recombine to generate light. Additionally, the cladding layers 130 may also play a role in heat dissipation by removing excess heat generated during operation of the laser semiconductor system 100. By carefully designing the composition and thickness of the cladding layers 130, such strain compensation may improve the performance of the laser semiconductor system 100. Similarly, the cladding layers 130 may help control the transverse mode of the laser system 100, and therefore aid in the emission of a single, well-defined beam of laser light.

[0033]

[0040] Sections 150 may refer to different parts of laser semiconductor system 100 that include different physical properties. Sections 150 may, for example, comprise different epitaxially grown structures. Layers (e.g., n-side layer 110, p-side waveguide layer 140, active region 120, etc.) may have different thicknesses or other physical dimensions (medial or lateral lengths). In general, any two physically distinct parts of laser semiconductor system 100 may be referred to as different sections.

[0034]

[0041] The multiple sections 150 may include a semiconductor front section 152 and a semiconductor rear section 154. The thickness of the p-side waveguide layer 140 may monotonically increase or decrease in each of the multiple sections 150 in a direction from the front section 152 to the rear section 154. For example, the front section 152 may include a p-side waveguide layer 140 that may be thinner than the p-side waveguide layer 140 in the rear section 154, while the other layers may be the same thickness. In that case, therefore, the front section 152 may be thinner than the rear section 154, as also shown in FIG. 2 .

[0035]

[0042] In some embodiments, anti-reflective coatings on the front and / or rear of the semiconductor and highly reflective coatings on the front and / or rear of the laser semiconductor system 100 may be used, as also shown in FIG.

[0036]

[0043] The highly reflective coating may be operable to maximize light reflection. The highly reflective coating may be applied to a facet of the laser semiconductor system 100 to minimize light output at one end of the semiconductor, the front or rear end of the semiconductor. Typically, the anti-reflective coating may be on the front end of the semiconductor, which may correspond to the light-emitting end. Typically, the highly reflective coating may be on the rear end of the semiconductor, which may correspond to the non-light-emitting end. The highly reflective coating may reflect light back into the semiconductor, so that it can exit at the other end of the laser semiconductor system 100.

[0037]

[0044] An anti-reflective coating may be used at the end of the laser semiconductor system 100 where the generated light is to exit the semiconductor. The anti-reflective coating may be operable to allow transmission of light through the facet of the laser semiconductor system 100.

[0038]

[0045] In some embodiments, the laser semiconductor system 100 may include a tapered transition between two adjacent sections of the plurality of sections 150, for example, between the front section 152 and the rear section 154 when they are adjacent, see also Figures 4A, 4B, and 4C. In some embodiments, the laser semiconductor system 100 may include lateral structuring.

[0039]

[0046] A tapered transition between adjacent sections of the plurality of sections 150 may generally indicate a gradual change / transition in some physical property between the adjacent sections. For example, it may indicate that one section may become gradually smaller or thinner in some dimension toward another section. A tapered transition may also indicate that some physical property may gradually decrease in amount, intensity, or degree between adjacent sections. For example, it may indicate that one section may become gradually less doped toward a neighboring adjacent section. A tapered transition may also indicate a gradual increase or decrease in width, thickness, or tapered shape, form, or figure. Thus, in the context of a semiconductor laser, a tapered transition between adjacent semiconductor sections may refer to a gradual change in a physical property of the semiconductor laser as it transitions from one section to another. A tapered transition may be characterized by a smooth transition over a certain distance rather than an abrupt change.

[0040]

[0047] Tapered transitions may be advantageous for avoiding optical loss from mode mismatches between adjacent sections. In lasers, light emitted from the active region may need to be efficiently coupled into a waveguide. Tapered transitions may help match the mode profile of the light to the waveguide, thus reducing losses and improving overall efficiency of the laser semiconductor system 100. In some cases, it may be desirable to change the size of the laser beam spot. Tapered transitions may be used to gradually expand or contract the beam spot. According to various embodiments, tapered transitions may also be used to match the impedance of different sections, reduce reflections, and improve signal transmission. Additionally, tapered transitions may help reduce stress between adjacent sections that physically vary the semiconductor (e.g., due to changes in layer thickness).

[0041]

[0048] In some embodiments, the length of each of the plurality of sections 150 may monotonically decrease or increase in each of the sections 150 in the direction from the rear section 154 to the front section 152 .

[0042]

[0049] In some embodiments, the thickness of the p-side waveguide layer 140 in the front section 152 may differ from the thickness of the p-side waveguide layer 140 in the rear section 154 by more than 1 / 30 of a wavelength and by less than 1 / 3 of a wavelength. In some embodiments, the resistivity of each of the multiple sections 150 may monotonically decrease in each of the sections 150 in a direction from the rear section 154 to the front section 152.

[0043]

[0050] In some embodiments, the resistivity of the front section 152 may differ from the resistivity of the rear section 154 by more than 1 / 30 and less than 1 / 3 of the resistivity of the front section 154. In some embodiments, the thickness of the active region 120 may be unequal for two or more sections of the plurality of sections 150. In some embodiments, the thickness of the active region 120 in each section of the plurality of sections 150 may monotonically decrease in each of the sections 150 in a direction from the rear section 154 to the front section 152.

[0044]

[0051] FIG. 2 shows an exemplary cross-section of a laser semiconductor system 100. The n-side layers 110, active region 120, cladding layers 130, and p-side waveguide layers 140 are shown, along with the front and rear sections 152 and 154. Also shown are anti-reflection coatings 205 and high-reflection coatings 210 at the end facets of the laser semiconductor system 100, as well as non-absorbing mirror (NAM) regions 220 and 230, i.e., the spaces between the coatings 205, 210 and the ends of the layers 120, 140 at the facets. Numbers similar to previous figures refer to similar features. The NAM sections 220, 230 may act as mirrors at the ends of the laser semiconductor system 100 cavity, enhancing laser gain and efficiency. The NAM sections 220, 230 may be formed by removing active regions at the front and / or rear facets of the laser semiconductor system 100 to enhance facet stability. As known to those skilled in the art, the NAM sections 220, 230 are optional.

[0045]

[0052] According to various embodiments, the front section 152 is characterized by a thinner waveguide layer 140 compared to the rear section 154. The thinner waveguide layer 140 may result in a lower confinement factor and higher injection within the front section 152.

[0046]

[0053] By removing a portion of the p-side waveguide layer 140, the field intensity maximum may be pushed away from the active region 120, resulting in a lower confinement factor. Similarly, higher injection may result from lower resistance in the thinner p-side waveguide layer 140.

[0047]

[0054] Conversely, a thicker p-side waveguide layer 140 in the rear section 154 may lead to the field intensity maximum being closer to the active region 120, resulting in a higher confinement factor. Lower injection may result from higher resistance in the thicker p-side waveguide layer 140.

[0048]

[0055] The cross section in FIG. 2 shows one particular polarity arrangement of the epitaxially grown layers; the opposite polarity is possible as well, ie, with the n-side (and different thicknesses in different sections) acting as a waveguide.

[0049]

[0056] 3 shows an exemplary top view of the laser semiconductor system 100 shown in FIG. 2 without the tapered transition between the front section 152 and the rear section 154. Numbers that are the same as in the previous figures indicate like features.

[0050]

[0057] 4A, 4B, and 4C show exemplary tapered transitions 405, 410, and 415 between the front and rear sections 152, 154 in a top view of the laser semiconductor system 100, according to various embodiments. Like numbers refer to like features.

[0051]

[0058] As described above, the tapered transitions 405, 410, 415 between adjacent sections of the plurality of sections 150 may generally indicate a gradual change / transition of some physical property between the adjacent sections. For example, it may indicate that one section may become gradually smaller or thinner in one dimension toward another section, as shown in FIGS. 4A and 4B. The tapered transitions may also indicate that some physical property may gradually decrease in amount, intensity, or degree between adjacent sections, as shown in FIG. 4C. Thus, in the context of semiconductor lasers, the tapered transitions 405, 410, 415 between adjacent semiconductor sections may refer to a gradual change in a physical property of the semiconductor laser system 100 as the semiconductor laser system 100 transitions from one section to another, e.g., from the front section 152 to the rear section 154, as shown in FIGS. 4A, 4B, and 4C. The tapered transitions 405, 410, 415 may be characterized as smooth transitions over a particular distance rather than abrupt changes.

[0052]

[0059] 5 illustrates an exemplary multi-section cross section of a laser semiconductor system 100, according to various embodiments. Like numbers refer to like features as in previous figures.

[0060] The multiple sections 150 are shown comprising a front section 152, a rear section 154, and middle sections 505, 510. The multiple sections 150 may be characterized, for example, by p-side waveguide layers 140 of different thicknesses. Thus, the confinement factor may be different in the different sections 150. According to various embodiments, the thickness of the p-side waveguide layer 140 may monotonically increase from the front section 152 to the rear section 154. Furthermore, as shown in FIG. 5, the lengths of the multiple sections 150 may vary. For example, an exemplary longer front section 152 and an exemplary shorter middle section 505 are shown.

[0053]

[0061] The use of multiple sections 150 may, for example, allow for fine control of the confinement factor and may provide a form of tapered transition. As will be appreciated by those skilled in the art, any number of sections 150 may be used in the laser semiconductor system 100. The transitions between sections 150 may avoid excessive optical loss at the interfaces of adjacent sections. As shown in Figures 4A, 4B, and 4C, any type of tapered transition between adjacent sections 150 may be envisioned.

[0054]

[0062] According to various embodiments, the present disclosure may be particularly advantageous for controlling slow-axis divergence in broad-area lasers. The semiconductor laser system 100 may be laterally constructed to adjust current injection and / or optical confinement laterally within one or more sections 150 of the laser semiconductor device 100. Through a desired tapered transition design, mode selection in the lateral direction may be improved to reduce the number of gain modes, thereby reducing the slow-axis divergence in broad-area lasers.

[0055]

[0063] This disclosure includes reference to particular examples; however, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the disclosure. Furthermore, modifications may be made to the disclosed examples without departing from the scope of the disclosure. Accordingly, it is intended that the disclosure not be limited to the disclosed examples, but that the disclosure include all examples that fall within the scope of the appended claims.

Claims

1. 1. A laser semiconductor system, comprising: an n-side layer, an active region, a p-side waveguide layer, and a cladding layer; a plurality of sections including at least a front section at a front of the semiconductor and a rear section at a rear of the semiconductor; Equipped with the thickness of the p-side waveguide layer monotonically increases in each of the plurality of sections in a direction from the front section to the rear section; Laser semiconductor system.

2. 10. The system of claim 1, comprising an anti-reflective coating on one or both of the front and rear portions of the semiconductor, and a highly reflective coating on one or both of the rear and front portions of the semiconductor.

3. The system of claim 1 , comprising a tapered transition between two adjacent sections of the plurality of sections.

4. 10. The system of claim 1, comprising lateral structuring.

5. 10. The system of claim 1, comprising one or more NAM sections.

6. 10. The system of claim 1, wherein the active region is one of a bulk active region, a quantum well active region, and a quantum dot active region.

7. 10. The system of claim 1, wherein an optical field confinement factor of the active region in the front section differs from an optical field confinement factor of the active region in the rear section by at least 10%.

8. 2. The system of claim 1, wherein a length of each of the plurality of sections monotonically decreases in each of the sections in a direction from the rear section to the front section.

9. 10. The system of claim 1, wherein the thickness of the p-side waveguide layer in the front section differs from the thickness of the p-side waveguide layer in the rear section by a percentage that is greater than 1 / 30 of a wavelength of a desired laser emission and less than 1 / 3 of the wavelength of a desired laser emission.

10. 2. The system of claim 1, wherein the resistivity of each of the plurality of sections monotonically decreases in each of the sections in a direction from the rear section to the front section.

11. 2. The system of claim 1, wherein the resistivity of the front section differs from the resistivity of the rear section by a percentage that is greater than 1 / 30 and less than 1 / 3 of the resistivity of the front section.

12. The system of claim 1 , wherein the thickness of the active region is unequal for two or more of the plurality of sections.

13. 10. The system of claim 1, wherein a thickness of the active region in each of the plurality of sections monotonically decreases in each of the sections in a direction from the rear section to the front section.

14. 10. The system of claim 1, wherein the laser diode is operable with reverse polarity.

15. 15. The system of claim 14, wherein the n-side layer acts as a waveguide, and the thickness of the n-side layer monotonically increases or decreases in each of the plurality of sections in a direction from the front section to the rear section.

16. 15. The system of claim 14, wherein the thickness of the p-side waveguide layer is substantially the same across the multiple sections.

Images