Systems and methods for maintaining laser beam divergence stability at varying pulse repetition rates

Abstract

Systems and methods presented herein are operable to control operating parameters within a laser system. In some embodiments, a laser system includes a reflector, a gain medium optically coupled to the reflector and operable to emit laser pulses, and a plurality of laser diodes operable to pump the gain medium with laser diode pulses to stimulate laser pulse emission. The laser system also includes a Q-switch device operable with the reflector to resonate laser light through the gain medium, and an output coupler optically coupled to the Q-switch device and operable to output the laser pulses based on a polarization of the laser light. One or more of the plurality of laser diodes is further operable to control operating parameters of the laser system by inserting one or more diode ghost pulses between laser diode pulses that result in the emitted laser pulses.

Description

Attorney Docket No. 10880.024WO1 SYSTEMS AND METHODS FOR MAINTAINING LASER BEAM DIVERGENCE STABILITY AT VARYING PULSE REPETITION RATES IN PULSED DIODE PUMPED SOLID-STATE RING LASERS Cross Reference to Related Applications

[0001] This patent application claims priority to, and thus the benefit of an earlier filing date from, U.S. Provisional Patent Application No. 63 / 657,803 (filed June 8, 2024), the contents of which are hereby incorporated by reference. Technical Field:

[0002] The present disclosure relates to laser systems, and more particularly to compact laser resonators capable of generating high-intensity output pulses. Background

[0003] Compact laser resonators capable of generating high-intensity output pulses have various applications in industrial and scientific fields. These resonators can incorporate multiple functional elements that need to work in concert within a confined space to generate and amplify laser light. Some approaches utilize geometric output coupling in unstable ring resonators for achieving high power output.

[0004] However, creating high-power laser output in compact packages presents significant challenges. For example, the functional elements of compact laser resonators, including image rotation mechanisms, various optical components, and ring resonator configurations, can produce conflicting effects when operating in close proximity. Conventional unstable resonator designs operating beyond plane-parallel magnifications of 1.0 demonstrate reduced effectiveness in efficiently delivering high pulse energy, good beam quality and requisite pulse width. Additional complications arise from managing net magnification effects over multiple round trips, coupled image and polarization rotation in non-planar configurations, and rotational mode control through reverse wave suppression. These various aspects typically create adverse effects that can impact overall system performance in compact configurations. SummaryAttorney Docket No. 10880.024WO1

[0005] Systems and methods described herein can enable laser operation in a laser resonator under critically unstable magnification conditions. Critically unstable magnification generally refers to a situation in a laser resonator where the optical magnification per round trip within the resonator is at or exceeds a specific threshold, resulting in a resonator that is on the verge of being stable. In such a system, the magnification of the resonator is tuned to a value close to or slightly exceeding 1.0, meaning that the beam expands slightly with each round trip inside the resonator. The critically unstable magnification conditions can, however, be configured with certain effects to produce robust and optimized laser output.

[0006] In some embodiments, the laser resonator can tune round trip magnification conditions into critically unstable magnification. The laser resonator can include adjustments performed near the final assembly stage and / or at the tuning stage for the resonator. Components of the laser resonator can adjust magnification conditions and / or other resonator conditions, including adjusting the optical power of one or more optical components. The adjustment of optical power can include a single direction adjustment. The single direction adjustment can include inserting a cylindrical mirror. The cylindrical mirror can include a large radius of curvature. These embodiments also allow for adjustments to other resonator conditions. The adjustments can help create an optimized laser output. This approach simplifies the process of achieving the critically unstable magnification condition, allowing for robust and optimized laser performance while minimizing complexity during the tuning process. In some embodiments, the laser resonator may include a polarization output-coupling. The laser resonator can alternatively operate with a geometric output-coupling under certain conditions and in continuous modes.

[0007] Producing a resonator capable of achieving a balance of elements for optimal performance can be simplified using embodiments herein that tune the round trip magnification into a critically unstable operational condition. The round trip magnification can be adjusted to achieve this condition by fine-tuning certain components of the laser resonator.

[0008] In one embodiment, a laser system includes a reflector, a gain medium optically coupled to the reflector and operable to emit laser pulses, and a plurality of laser diodes operable to pump the gain medium with laser diode pulses to stimulate laser pulse emission. The laser system also includes a Q-switch device operable with the reflector to resonate laser light throughAttorney Docket No. 10880.024WO1 the gain medium, and an output coupler optically coupled to the Q-switch device and operable to output the laser pulses based on a polarization of the laser light. One or more of the plurality of laser diodes is further operable to control operating parameters of the laser system (e.g., laser divergence of the emitted laser pulses, temperatures of one or more optical components within the laser system, etc.) by inserting one or more diode ghost pulses between laser diode pulses that result in the emitted laser pulses. The Q-switch device may be operable to average out aberrations in laser light via a plurality of round trips of the laser light through the laser system.

[0009] In some embodiments, the laser system includes a reverse wave suppression reflector configured outside of a primary optical path of the laser system. The reverse wave suppression reflector may propagate the laser light through the primary optical path in a clockwise manner, and suppress any laser light propagating in a counterclockwise manner. The laser system may also include a saturable absorber configured in the primary optical path of the laser system and operable to provide passive Q-switching to the laser system. At least one of the plurality of the laser diodes may be operable to heat the saturable absorber to change the operating parameters of the laser system. Alternatively or additionally, another device may be used to heat the saturable absorber to change the operating parameters of the laser system. The saturable absorber may be configured in a housing with a wave plate. In some embodiments, the primary optical path is configured to exhibit a critical instability near plane-parallel operating conditions based on a magnification of greater than 0.85.

[0010] In some embodiments, the laser system includes a controller operable to control diode ghost pulse repetition rates to change the operating parameters of the laser system, to control diode ghost pulse temporal sequences based on a temperature of the gain medium to change laser divergence, to detect environmental conditions of the laser system before laser pulse emission to direct at least one of the plurality of laser diodes to generate diode ghost pulses to change the operating parameters of the laser system based on the environmental condition of the laser system, to monitor the operating parameters of the laser system to adaptively control the plurality of the laser diodes, and / or to monitor the operating parameters of the laser system to predict future operating parameters of the laser system to control the plurality of the laser diodes based on the predicted future operating parameters.Attorney Docket No. 10880.024WO1

[0011] The various embodiments disclosed herein may be implemented in a variety of ways as a matter of design choice. For example, some embodiments herein are implemented in hardware whereas other embodiments may include processes that are operable to implement and / or operate the hardware. Other exemplary embodiments, including software and firmware, are described below. Still, other exemplary embodiments may include methods of operating the laser resonator. Brief Description of the Figures

[0012] Some embodiments of the present invention are now described, by way of example only, and with reference to the accompanying drawings. The same reference number represents the same element or the same type of element on all drawings.

[0013] FIG. 1A is a block diagram of a laser system, in one exemplary embodiment.

[0014] FIG. 1B is a block diagram of a laser resonator with an out-of-plane reflector, in one exemplary embodiment.

[0015] FIG. 2 is a diagram illustrating a coupling for s-pol and p-pol field components of clockwise and counterclockwise propagating radiation, in one exemplary embodiment.

[0016] FIG. 3 is a diagram illustrating a single round-trip coupling between clockwise and counter-clockwise s-pol and p-pol light evaluated, in one exemplary embodiment.

[0017] FIG. 4 illustrates a heating effect on the focus of a beam traversing through a heated optical component, in one exemplary embodiment.

[0018] FIG. 5 is a block diagram of a laser resonator with a Q-Switch device being implemented as a combination of a saturable absorber and a waveplate, in one exemplary embodiment.

[0019] FIGS. 6A-6C illustrate output pulses from a passive Q-switched laser for successively longer diode pump pulse durations, in one exemplary embodiment.

[0020] FIGS. 7A-7C illustrate various timing diagrams associated with “ghost pulse” generation, in one exemplary embodiment.Attorney Docket No. 10880.024WO1

[0021] FIGS. 8A and 8B illustrate heating with and without the use of ghost pulses, in one exemplary embodiment.

[0022] FIG. 9 is a block diagram of a laser gain medium, in one exemplary embodiment.

[0023] FIG. 10 illustrates the effects of rotations that average on each other upon successive round trips, in one exemplary embodiment.

[0024] FIG. 11 is a diagram illustrating laser resonator stability, in one exemplary embodiment.

[0025] FIG. 12 is a diagram illustrating misalignments being compensated for in later roundtrips of the radiation, in one exemplary embodiment.

[0026] FIG. 13 is a block diagram of a laser resonator with three of six reflectors being functionally contained along with the associated optical path inside a solid prism, in one exemplary embodiment.

[0027] FIG. 14 is a block diagram of a laser resonator with five of eight reflectors being functionally contained along with the associated optical path inside a solid prism, in one exemplary embodiment.

[0028] FIG. 15 illustrates the laser resonator of FIG. 14 as viewed normal to the plane of the portion of the optical path contained within the prism, in one exemplary embodiment.

[0029] FIG. 16 is a flowchart of a process for assembling a laser and adjusting placement of optical components to tune the resonator, in one exemplary embodiment.

[0030] FIGS. 17-20 are block diagrams illustrating different views of a laser resonator with a periscope output for beam modification, in one exemplary embodiment.

[0031] FIG. 21 is a block diagram of an exemplary computing system in which a computer readable medium provides instructions for performing methods herein. Detailed Description of the FiguresAttorney Docket No. 10880.024WO1

[0032] The figures and the following description illustrate specific exemplary embodiments. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody certain principles and are included within the scope of the embodiments. Furthermore, any examples described herein are intended to aid in understanding the embodiments and are to be construed as being without limitation to such specifically recited examples and conditions. As a result, the embodiments are not limited to any of the examples described below.

[0033] FIG. 1A is a block diagram of a laser system 10, in one exemplary embodiment. In this embodiment, the laser system 10 includes a gain medium 18, a reflector 26, a Q-switch device 22, and an output coupler 20. The laser system 10 also includes a plurality of laser diodes 24-1 - 24-N that are operable to pump laser light into the gain medium 18 and / or various other optical elements within the laser system 10. For example, one or more of the laser diodes 24 may be operable to pump the gain medium 18 with diode laser pulses 12-1 – 12-N. These diode laser pulses 12 stimulate the gain medium 18, and the laser light thereof resonates between the Q-switch device 22 and the reflector 26, ultimately resulting in laser pulses 14-1 – 14-N. The laser pulses 14, when generated, are emitted from the laser system 10 by the Q switch device 22 changing a polarization of the laser pulses 14 such that they propagate through the output coupler 20 (e.g., a polarization based output coupler).

[0034] The laser system 10 may also include a controller 30 that is operable to control the laser diodes 24. For example, the controller 30 may direct one or more of the laser diodes 24 to pump the gain medium 18 with diode laser pulses to stimulate the gain medium 18. The controller 30 may also direct one or more of the laser diodes 24 to provide one or more diode “ghost pulses” 16-1 – 16-N to various optical elements within the laser system 10 to control certain operating parameters of the laser system 10. In some embodiments, these ghost pulses 16 can heat the various optical elements within the laser system 10, including the gain medium 18, to change the operating parameters of the laser system 10.

[0035] These operating parameters may include a laser divergence of the laser pulses 14 emitted by the laser system 10. For example, when the laser system 10 is operating and emitting laser pulses 14, the environmental conditions of the laser system 10 may change due to heatingAttorney Docket No. 10880.024WO1 of the gain element 18, among other things. This change in the environmental conditions may cause the laser pulses 14 to diverge as they are emitted from the laser system 10. To control this laser divergence, the controller 30 may direct one or more of the laser diodes 24 to introduce the ghost pulses 16 into the laser system 10. This may include pumping one or more of the ghost pulses 16 into the gain medium 18 to change the temperature of the gain medium 18, thereby tuning the operating parameters of the laser system 10. Alternatively or additionally, one or more the ghost pulses 16 may be used to heat other components within the laser system. For example, the laser system 10 may include a saturable absorber that can be tuned by heating the saturable absorber with one or more of the ghost pulses 16. Alternatively or additionally, the saturable absorber may be controllably heated with an external heating element (e.g., as controlled by the controller 30).

[0036] In some embodiments, the controller 30 is operable to control repetition rates of the ghost pulses 16, intensities of the ghost pulses 16, pulse widths of the ghost pulses 16, and the like. And, in some embodiments, the controller 30 is operable to monitor the operating parameters of the laser system 10 to adjust these various attributes of the ghost pulses 16. In some embodiments, the controller 30 can detect and monitor environmental conditions that the laser system is operating in (e.g., before and after lasing) to adaptively control the attributes of the ghost pulses 16. And, in some embodiments, the controller 30 may be configured with an artificial intelligence module and / or a machine learning module that can be trained based on previous operations of the laser system 10 and / or other similar laser systems to control the ghost pulses 16. For example, the controller 30, after being trained, may be able to monitor the operations of the laser system 10 and predict future operating parameters of the laser system 10 such that the controller 30 can direct the laser diodes 24 to change the attributes of the ghost pulses 16.

[0037] The insertion of ghost pulses 16 may be applied to any of a variety of Q- switched resonant laser systems. Some examples of Q-switched resonant laser systems include, but not limited to, ring cavity laser resonators. FIGS. 1B and 5 illustrate ring cavity laser resonators in which the controller 30 and the laser diodes 24 may be implemented. More specifically, FIG. 1B illustrates a ring cavity laser resonator and its operating features to explain to the reader how one particular ring cavity laser resonator operates. FIG. 5 illustrates a similarAttorney Docket No. 10880.024WO1 configuration in which the controller 30 can tune various components within the ring cavity laser resonator. However, the invention is not intended be limited to any ring cavity laser resonator. Rather, these embodiments are merely intended to illustrate how the concepts herein can be used to tune operating parameters of various laser resonator systems.

[0038] FIG. 1B is a block diagram of a laser resonator 120 with out-of-plane reflectors (e.g., elements 110 and 116), in one exemplary embodiment. In this embodiment, the laser resonator 120 includes various optical components arranged to form a closed-loop resonator. The dotted line 100 represents the primary plane of the laser resonator 120. The laser resonator 120 includes optical elements 104, 106, 108, 110, and 112 (e.g., reflectors) used to steer and direct the laser beam to manage its propagation within the resonator 120. These may also be operable to influence the beam’s polarization and / or phase. These optical elements guide the beam around the resonator 120’s path (i.e., being paths 130, 132, and 134 ) to complete the round-trip. They manage beam direction and stability within the cavity. The laser resonator 120 also includes a gain medium 122 for laser beam amplification. The gain medium 122 provides the necessary stimulated emission for light amplification, driven by external energy (such as optical pumping or electrical excitation).

[0039] The laser resonator 120 also includes a Pockels cell 124. The Pockels cell 124 is an electro-optic device that is used to control the polarization state of the light passing through it. By applying an external voltage to the Pockels cell, the polarization of the laser beam (e.g., along directions ê1and ê2) can be dynamically modified. This is used to control resonator modes, polarization output-coupling, and / or beam shaping. The circular arrows labeled CW (clockwise) and CCW (counterclockwise) indicate the two counter-propagating modes of the laser beam traveling in the laser resonator 120. The output coupling 114 is the optical element where at least a portion of the laser beam exits the laser resonator 120. Examples of the output coupling 114 may include an optical filter, polarizer, and / or some other selective optical element.

[0040] The laser resonator 120 may include a reverse wave suppression reflector 116 positioned outside the primary plane 100 of the laser resonator 120. Examples of the reverse wave suppression reflector 116 include mirrors, corner cubes, or other functional reflectors. In some embodiments, the laser resonator 120 may include feedback means such as a seed sourceAttorney Docket No. 10880.024WO1 radiation for determining a preferred direction of rotation in the laser resonator 120. Other embodiments of the laser resonator 120 may include a spectral filtering component such as a volume Bragg grating. The laser resonator 120 may also include a polarizing cube 126 that is operable to direct light to the reverse wave suppression reflector 116, as explained below.

[0041] Like the reverse wave suppression reflector 116, the optical element 110 is positioned outside the primary plane 100 of the laser resonator 120. Thus, the optical element 108 may reflect the beam outside of the primary plane 100 during the clockwise rotation of the beam to the optical element 110, which in turn reflects the beam back to the primary plane 100 for reflection by the optical element 112. In the counterclockwise operation, the optical element 112 reflects the beam outside of the primary plane 100 to the optical element 110, which in turn reflects the beam into the primary plane 100 to the optical element 108.

[0042] The laser resonator 120 thus has multiple reflectors structured along an optical path to create a closed-loop resonator configuration. At least one of the reflectors, such as reflector 104 and / or 106, can allow for tuning of the round-trip magnification of the resonator 120 to achieve an operational condition. Specifically, the operational condition can be a critically unstable operational state that is configured or set near the end of the assembly process of the resonator 120. This tuning process is described further below with respect to an assembly method associated with the resonator 120.

[0043] In some configurations, the round-trip magnification of the resonator 120 can be controlled by selecting a curvature of one of the reflectors and / or introducing a differential heat flux on a gain medium coupled with the optical path. By enabling adjustment of the magnification through these methods during assembly, the assembly technique eliminates a magnification tuning step during intermediate stages of assembly. This approach allows the operational parameters of the laser system to be evaluated and fine-tuned while the critically unstable condition is established, which facilitates high-polarization output-coupled laser light. For instance, adjusting one optical component of the resonator 120, such as replacing and / or modifying a reflector 104 and / or 106, may alter the round-trip magnification and support a desired operational condition. This ability to tune the magnification may simplify the assembly process and enhances the quality of the output beam.Attorney Docket No. 10880.024WO1

[0044] The embodiment shown in FIG. 1B also includes a non-planar resonator configuration featuring six reflectors, with one of the reflectors being structured to lie out of the primary resonator plane 100. This design affords structural benefits, including maintaining the majority of the optical cavity within a single plane, which can simplify alignment procedures and potentially reduce manufacturing costs. Furthermore, the non-planar configuration produces a compact resonator 120 that enables a smaller overall system package. This compactness can also permit integration of external components, such as an output periscope, in close proximity to the resonator 120 in applications requiring compact optical systems. Additionally, the resonator 120, while compact, facilitates enhanced manufacturing and operational efficiency. Advantages include assembly efficiencies, tolerance to optical aberrations, and improved output performance relative to its size.

[0045] In the embodiment shown in FIG. 1B, the resonator 120 is structured to provide a preferential rotational mode for laser radiation rotating within the optical cavity. This preferential rotational mode is achieved by feeding back a portion of early-developed light within the cavity, thereby allowing a dominant rotational mode to be selected. The rotational modes are represented as CW (clockwise) and CCW (counterclockwise), where CW designates light rotating from location 130 to location 132 and subsequently to location 134, whereas CCW designates light rotating from location 130 to location 134 and subsequently to location 132. These designations are used in mathematical equations and formalizations to evaluate specific aspects of the rotational modes.

[0046] The resonator 120 includes a gain element, such as Gain Element 122, to couple energy into the cavity. For instance, the Gain Element 122 can be a crystal gain medium that is optically pumped by an external source, such as a pump light diode 140, such as laser diodes 24 of FIG. 1A. The Gain Element 122 can be placed in various positions along the optical path in different configurations of the resonator 120 to suit particular operational parameters.

[0047] In some embodiments,, the laser resonator 120 may be configured with a plurality of pump light diodes 140-1 – 140-N to provide lasing to the laser resonator 120 as well as control operational features of the laser resonator 120. For example, one or more of the pump light diodes 140 may be operable to introduce ghost pulses that can heat various componentsAttorney Docket No. 10880.024WO1 within the laser resonator 122 control laser divergence and / or other operational characteristics of the laser resonator 120. The ghost pulsing is described in greater detail below. While described specifically for the ring resonator embodiment, it should be noted that the ghost pulsing methods described herein are not restricted to non-planar ring resonators or even ring resonators. Ghost pulsing methods can be applied to any Q-Switched laser embodiments in general to manage thermal lensing over various ranges of operating and environmental conditions.

[0048] The laser resonator 120 also includes a Polarizing Output Coupler 114, which can be implemented as a thin-film polarizer or a similar component. In one embodiment, the Polarizing Output Coupler 114 is structured to transmit light polarized parallel to the Primary Resonator Plane 100 while reflecting light polarized perpendicular to the Primary Resonator Plane 100. This polarization control enables selective polarization output from the cavity. Additionally, one or more Q-switch devices 124 are included in the resonator 120. In the present embodiment, the Q-switch device 124 can include one and / or more Pockels cells to facilitate active polarization rotation. The Q-switch device 124 may further include a wave plate to assist in tuning the output coupling. Other embodiments may employ alternative polarization rotators to achieve similar results.

[0049] The rotation of light intensity patterns within the laser cavity plays a significant role in compensating for thermal effects, pumping aberrations, and / or other aberrations. As light undergoes successive round trips within the cavity, rotation of the light intensity patterns effectively averages these aberrations, resulting in improved beam quality. For the illustrated embodiment with a non-planar configuration utilizing six reflectors, each round trip passively induces a 90-degree rotation of the light intensity pattern. This systematic pattern rotation serves to distribute any aberrations evenly across the beam, thereby elevating overall beam quality.

[0050] The resonator 120 also incorporates a reverse wave suppression reflector 116 to further refine the cavity’s operation. In one configuration, the resonator 120 is structured to permit light to traverse the cavity in a clockwise (CW) direction, as indicated by arrows associated with the optical paths in FIG. 1. For light traversing the cavity in the counterclockwise direction, the reverse wave suppression reflector 116 suppresses that light. In some embodiments, the resonator 120 can be structured to create light that is predominately polarizedAttorney Docket No. 10880.024WO1 either parallel to the primary resonator plane 100 (p-̂pol) or perpendicular to the primary resonator plane 100 (ŝ-pol) at location 134. Through active polarization control or the use of elements such as the Q-switch device 124, the system can further adjust polarization rotation to influence operational modes. For example, the active polarization rotation elements may be configured to achieve a near-zero polarization rotation per round trip, depending on the desired performance characteristics. Generally, the polarization state is different at different locations in the cavity and at different times in the Q-switch process. During pumping before Q-switching, the Pockels cell 124 is configured to dump all the light out of the cavity, thereby spoiling the cavity and permitting gain to build up. The Q-Switch then selects a polarization state that increases the cavity Q which permits cavity feedback and gain for giant pulse build up and emission.

[0051] The behavior and performance of the resonator 120 can be analyzed using matrix formalism to describe the electric field polarization states of light propagating between designated locations within the cavity. For convenience and to simplify subscripts used in such equations, the resonator location 130 is referred to as “location A,” the resonator location 132 is referred to as “location B,” and the resonator location 134 is referred to as “location C.”

[0052] Matrix representations of electric field polarization states are further utilized to illustrate the polarization output coupling mechanism associated with the resonator 120. This coupling enforces specific polarization states for the laser light output and impacts the cavity design by discouraging the use of plane-parallel configurations in most scenarios. For a CWpropagation, ^^⃗ ℰ= ^ is the complex vectoral representation of the clockwisepropagating light(B), where ℰ^is the complex amplitude of the electrical fieldenvelope in the ^̂ − ^^^^^^^^^, and ℰ^ is the complex amplitude of the electrical field envelopein the ^̂ − ^^^^^^^^^.

[0053] The active polarization rotation component may be one or more Pockels cells 124, in which the light propagating with polarization along axis ^^̂ is delayed by a phase ^ relative to the light propagating along the axis ^^̂. The relative phase delay is controlled by anAttorney Docket No. 10880.024WO1 externally controlled voltage. The crystal axis of the Pockels cell is rotated with respect to the primary resonator plane 100 by an angle ^^.

[0054] In the configuration shown, the electric field polarization state at location 132 (B) is transformed to the electric field polarization state at location 134 (C) for clockwise propagation as follows:

[0055] ^^⃗ ^,^^ = ^→^^^⃗ ^,^^cos &'( − ^ co ) + ' ) + '56] ^ s 2^^ sin &^( −^ sin 2^^ sin & ([00 ^^→^ = " / (results in a 90 degree rotation of the polarization and can be represented by

[0058] ^^⃗0,^^ = ^→0^^⃗ ,^^

[0059] With the rotation matrix

[0060] 0 −1^→0 = 11 0 4light that is polarized in the ^̂ − ^^^^^^^^^ at location130 (A) is transmitted through the polarizing output coupler, whereas light that is polarized in^̂ − ^^^^^^^^^ at location 130 (A) is reflected to location 132 (B). Consequently, the followingtransfer matrix from A to B (130 to 132) is defined as follows:

[0062] 1 00→5 = 1

[0063] An output coupler transfer matrix from location 130 (A) to the output can be defined as

[0064] = 10 0Attorney Docket No. 10880.024WO1

[0065] Therefore, for an embodiment as shown with an active polarization element (e.g., a Pockels Cell), the sequential application of these transfer matrices can be used to form a round trip polarization evolution matrix from location 132 (B) back to location 132 (B) as follows: ^^ ^^→^,9:,^^ = 0→5 ^→0 ^→^ = <^ sin)2^^+ sin =2> − ^cos =2> + ^ cos)2^^+ sin =2>^ ?as: 00^→678,^^ = < ^ ^ ^− ^ −^ >?using propagationclockwise(CCW) directed light polarized in the ^̂ − ^^^^^^^^^ at location 132 (B) is transmitted throughthe polarizing cube 126 so that =11 0^→0 0 04

[0068] Counter-clockwiselocation 130 (A) to 132 (C) is rotated by the transfer matrix:

[0069] 0 10→^ = 1propagating light traversing the Pockels cell undergoes polarization rotation described by the transfer matrix: ^^ ^cos = + ^ cos 2^^+ sin = ^ sin 2^^+ sin =Alight is given by:Attorney Docket No. 10880.024WO1 −^ sin)2^ + s '^ in & ( 0

[0072] ^^→^,9:,^^^ = ^→^ 0→^ ^→0 = " ' / ^ '0direction at location 132 (B) and that is polarized in the ^̂ − ^^^^^^^^^ is reflected by thepolarizing cube 126 to the reverse wave suppression reflector 116. In this embodiment, the light in the CCW direction is a non-preferred rotational mode, and using the Reverse Wave Suppression mirror as shown provides initial support for the preferred rotational mode of CW. This results in direct coupling to the clockwise rotating ^-̂polarized light at location 132 (B).

[0074] The transfer matrix for this process is simply: 00^,^^^→^^ = 10 14

[0075] With these transfer field at location 132 (B) in the clockwise and counterclockwisethrough round trips using the following relations:

[0076] ^^⃗ ^,^^^,BC^ = D ^→^9:,^^^^^⃗ ^,^^^,BE78,B = ^,^^^,Bwhere g is the net gain minus loss for the roundtrip, and g’ is similar but for only the part of the cavity traversed from location 132 (B) through the output coupler.

[0079] The resulting resonance and output performance can be evaluated for conditionswhere ^ = 0 and where ^ ≠ 0. The results of these two conditions, including the effects of thereverse wave suppression reflector 116 that are further described below with respect to FIGS. 2 and 3, create particular radiation evolution pathways inside the cavity, allowing for effective high-power pulsed operation while using a single rotational mode within the cavity.

[0080] When ^ = 0, the matrix elements are simplified, so that:Attorney Docket No. 10880.024WO1 0−^→^,9:,^^ = 1 10 0 4; ^→678,^^ = 10 01 04; ^→^,9:,^^^ = 1 0 0−1 04

[0081] Primary Resonator Plane 100) and p-̂pol (parallel to the Primary Resonator Plane 100) field components for clockwise (CW) and counterclockwise (CCW) propagating radiation under the condition where δ=0. Under this condition, the resonator is characterized as being “spoiled,” meaning that the cavity feedback is temporarily disrupted to prevent lasing action. As a result, any spontaneous emissions originating within the Gain Element 122 of the resonator 120 are transmitted out of the Polarizing Output Coupler 114 within two round trips of the optical path.

[0082] When the resonator 120 is in this spoiled condition, external energy can be introduced and coupled into the Gain Element 122, typically through optical pumping. This process prepares the gain medium by storing energy, which can subsequently amplify laser radiation when the spoiled condition is removed, and the resonator cavity feedback is restored. By allowing spontaneous emissions to escape from the cavity while simultaneously pumping energy into the Gain Element 122, this technique efficiently prepares the system for generating a high-energy pulse during subsequent operation.

[0083] The interaction between ŝ-pol and p-̂pol field components under this condition demonstrates the selective transmission and suppression of specific polarization states. This property is advantageous for controlling and preparing the output characteristics of the resonator 120 and optimizing the energy stored within the gain medium during the pumping phase. Upon restoring the cavity feedback, the resonator 120 transitions from the spoiled state, supporting the generation of a high-quality laser pulse with desired polarization and rotational modes. This operational sequence further allows precision control of the radiation emitted under these carefully managed conditions.

[0084] FIG. 3 is a diagram depicting the round-trip coupling of ŝ-pol and p-̂pol light in a resonator 120, specifically evaluated at location 132 (B), when δ is tuned to a non-zero value (δ≠0). The Pockels cell, configured as the Q-switch device 124, is operated to introduce a rotation angle θ such that 0°<θ<90°. This induces changes in the resonator’s optical behavior as compared to when δ=0. The dashed lines in FIG. 3 represent the new resonant and outputAttorney Docket No. 10880.024WO1 coupling pathways introduced by this tuning of δ, while the original coupling pathways, represented by solid lines, remain operational but are modified by the non-zero δ value.

[0085] In the embodiment shown, two new resonances are established for ŝ-polarized light propagating in the counterclockwise (CCW) or clockwise (CW) direction, as observed at location 132 (B). These resonances result from the cavity’s altered dynamics when δ is not zero, creating additional complexity in the resonator’s operation. Specifically, the CCW ŝ-pol resonance couples into the CW ŝ-pol resonance through intermediate coupling involving the CCW p-̂pol state and the CW p-̂pol state. The CW ŝ-pol resonance then couples to the output via its interaction with the Polarizing Output Coupler 114.

[0086] Importantly, the coupling dynamics favor the build-up of higher power in the CW resonance before significant energy can contribute to the CCW resonance. This is because the CCW resonance channels energy into the CW resonance prior to energy being output. This dynamic behavior, illustrated within the boxed region of FIG. 3, sets the CW resonance as dominant in power build-up, which improves overall efficiency and output energy characteristics.

[0087] Q-switching functionality in this embodiment leverages the ability to tune δ. By tuning δ to zero, the cavity is spoiled, preventing lasing and ensuring that energy from optical pumping accumulates in the Gain Element 122. Subsequently, δ is tuned to a non-zero value that supports a high-Q resonance, allowing the establishment of resonant cavity feedback. This feedback leads to the generation of giant energy pulses released from the resonator 120. These dynamically controlled pulses are important feature of the active Q-switching operation enabled by the Pockels cell as Q-switch device 124.

[0088] Alternative embodiments may operate differently from the pulsed operation illustrated. For instance, continuous wave (CW) emission can be achieved by replacing and / or supplementing the Pockels cell with a static polarization rotation element, such as a waveplate. In another embodiment, a saturable absorber may be added to the resonant cavity to enable passive Q-switching operation, eliminating the need for active polarization rotation devices.Attorney Docket No. 10880.024WO1

[0089] The configuration shown in FIG. 1 further reduces optical element counts by eliminating the need for intracavity waveplates in certain instances. This is made possible because the polarization rotation induced by the Pockels cell matches the image rotation achieved during the round trip of light within the non-planar resonator. In contrast, other resonator configurations, such as the four-mirror twisted rectangle cavity, typically require a waveplate to maintain proper polarization rotation during round trips. However, waveplates may optionally be included in some embodiments to optimize Pockels cell performance. For example, a waveplate may be included to adjust the voltage required to spoil the cavity or to modify the operational requirements of the Pockels cell.

[0090] The Polarizing Output Coupler 114 in the embodiment shown (e.g., implemented as a thin-film polarizer) is configured to control output coupling based on polarization rotation. Other polarizing elements may optionally be used to fulfill this function. For active Q-switching, the dynamically controlled polarization rotation device, such as the Pockels cell, determines the output coupling. A high-voltage signal applied to the Pockels cell can be shaped to influence the characteristics of the Q-switched laser pulse, such as its pulse length and shape. By dynamically controlling polarization rotation in this way, precise control over the laser output parameters is achieved, enhancing the versatility and applicability of the laser system.

[0091] In certain embodiments, the laser gain medium, such as a Nd:YAG crystal, is optically pumped using laser diode bars. Each laser pulse emitted from the resonator 120 corresponds to a single pulse of diode pumping, which is generated by supplying an electrical current pulse to the diode bars. The diode drivers, which supply power to these laser diode bars, are typically equipped with capacitors that charge between pulses. These capacitors enable higher electrical currents to be delivered during each diode pulse, which is required to achieve sufficient optical pumping of the gain medium.

[0092] The duration of each diode pulse, prior to the generation of a laser pulse, directly correlates with the optical energy delivered by the diode and the energy stored within the gain medium. This stored energy accumulates within the gain medium during the pumping phase, sets the stage for the cavity Q-switch to activate, and initiates stimulated emission. Once the Q-switch is engaged, lasing action begins, resulting in the generation of a laser pulse within the resonator.Attorney Docket No. 10880.024WO1

[0093] Several operating parameters influence the performance of the system, including the pulse repetition rate of the diode pump, the optical pulse energy delivered by the diodes, and the optical-to-optical conversion efficiency of the system. The conversion efficiency refers to the proportion of energy at the diode pump wavelength that is converted to emitted energy at the lasing wavelength of the gain medium. Together, these factors determine the total power deposited as energy into the gain medium.

[0094] As optical pumping generates both useful energy for lasing and heat, the laser gain medium, such as Nd:YAG, can experience thermal effects. In particular, the physical properties of the gain medium, such as its refractive index, are temperature-dependent, introducing a thermal lensing effect. Thermal lensing modifies the optical path of the light traveling through the gain medium and may influence the divergence of the emitted laser beam. The extent of thermal lensing is directly related to the amount of heat deposited in the gain medium, which depends on factors such as the diode pulse repetition rate, diode and crystal temperatures, and the optical pulse energy.

[0095] Variations in operating conditions can lead to correspondingly variable thermal lensing effects, resulting in changes to the divergence of the laser beam. Laser divergence can vary over a range of operating conditions due to changes in the thermal distribution within the gain medium. To mitigate these issues, the design and fabrication of the laser cavity focus on bounding the variations in laser divergence within desired tolerances. Laser cavity designs are optimized so that, under a range of operating conditions, the divergence of the emitted laser beam remains stable and consistent. Such design considerations ensure reliable performance and maintain high beam quality over the intended operating range.

[0096] In some configurations, precision control over the cavity geometry and / or component alignment addresses thermal lensing effects. For instance, the resonator is structured to maintain operational consistency even when thermal conditions in the gain medium vary. Careful selection of operating parameters, such as optimal pulse repetition rates and crystal cooling conditions, can work in tandem with the cavity design to mitigate divergence variations due to thermal lensing. This ensures the laser system operates efficiently and produces high- quality beam output across its operational range.Attorney Docket No. 10880.024WO1

[0097] In some embodiments, the Q-switch device 124 of FIG. 1 is implemented using a saturable absorber and / or a tunable wavelength approach instead of a dynamic polarization rotation device, such as a Pockels cell, to facilitate passive Q-switching. A saturable absorber, such as Cr:YAG, is incorporated into the cavity to dynamically control intracavity losses. When the intensity of emissions from the gain medium is low, the saturable absorber introduces sufficient intracavity loss to prevent lasing by exceeding the available gain. However, as energy is stored in the gain medium and the generated emission intensity increases, the saturable absorption decreases, reducing intracavity losses. This initiates lasing action within the cavity, resulting in the emission of a short, high-energy laser pulse.

[0098] Passive Q-switched lasers often exhibit high sensitivity to optomechanical fluctuations, leading to substantial jitter in pulse timing relative to the diode pumping pulses. However, embodiments using a combination of the image rotation, the ring cavity configuration, and the critically unstable cavity design associated with the laser system described herein exhibit significantly reduced pulse jitter. This arrangement is also less sensitive to environmental mechanical vibrations and fluctuations. Additionally, the interplay between the response of the saturable absorber, the image rotation, and the ring laser cavity can produce longer pulse durations in certain embodiments, with some pulses lasting longer than 10 nanoseconds.

[0099] For passive Q-switching operation, a saturable absorber, such as Cr:YAG, can be selected and designed for specific transmission properties. For example, the Cr:YAG crystal can have a thickness and doping level chosen to achieve a transmission rate of approximately 45% to 65% under low-intensity light conditions. As the intracavity intensity increases, the saturable absorber transitions to a higher transmission state, allowing the transmission of higher intensities and enabling energy release as a laser pulse.

[0100] In some configurations, the saturable absorber accumulates heat due to intracavity energy from gain medium emissions at the lasing wavelength. In other embodiments, heat accumulation can also result from the absorption of light from the pump diodes, depending on the pumping geometry of the gain medium. Additionally, certain embodiments incorporate an auxiliary optical illumination device to specifically illuminate the saturable absorber, which isAttorney Docket No. 10880.024WO1 separate from the pump diodes and gain medium emissions. This auxiliary illumination allows precise control over the saturable absorber’s heating and operational behavior.

[0101] Thermal management is an important consideration for stable operation of the saturable absorber and / or the gain medium. Heating within a transmissive optic, such as the saturable absorber, is balanced by thermal transport and cooling mechanisms. Typically, cooling is achieved through conduction via mounts located on the perimeter of the transmissive optic. This creates a thermal gradient extending from the center of the optic toward its perimeter. Because the refractive index of the saturable absorber and / or gain medium is temperature- dependent, this thermal gradient introduces a lensing effect that modifies the optical properties of the system.

[0102] FIG. 4 depicts the thermal lensing effect experienced by a beam passing through a transmissive optic subjected to two different temperature conditions. When the optic is moderately heated, the induced optical power resulting from the thermal lensing is lower. However, at higher temperatures, the thermal lensing effect intensifies, increasing the optical power introduced. To address this phenomenon, the laser cavity can be configured to accommodate a range of thermal lensing magnitudes. Additional powered optics within the cavity, such as lenses and mirrors, can be employed to balance and compensate for these thermally induced effects, ensuring consistent performance over varying thermal conditions.

[0103] In some embodiments, active heating mechanisms may be utilized to further control the thermal characteristics of transmissive optics within the resonator. Under certain operating conditions, active heating devices may be employed to intentionally add heat to transmissive components, ensuring that the thermal lensing effect remains equivalent to predetermined operating conditions with uniform performance characteristics. This capability allows broader operational flexibility and ensures that the laser system can maintain high-quality beam output across a wide range of environmental and operational parameters.

[0104] FIG. 5 illustrates an embodiment of a laser resonator 700 that is similar to the configuration shown in FIG. 1, but with modifications to the Q-switch device 124. In this embodiment, the Q-switch device 724 is implemented as a housing that contains both a saturable absorber and a waveplate. An external illuminator 702 may be incorporated to project an optical distribution onto the saturable absorber 724, which in turn absorbs the illumination energy and is heated as a result due to the absorbed energy. This external illumination assists in controlling theAttorney Docket No. 10880.024WO1 thermal characteristics of the saturable absorber 724, optimizing its performance during operation. For example, the heating of the saturable absorber 724 influences its absorption and transmission characteristics, enabling precise control over its performance and contributing to effective Q-switching operation.

[0105] In some embodiments, the external illuminator 702 provides illumination at a wavelength that is different from the laser’s operational wavelength. A dichroic mirror 706 may be used in such cases to direct the external illumination onto the saturable absorber 724 while simultaneously transmitting light at the laser wavelength along the laser cavity’s optical path. This configuration enables precise control over the saturable absorber’s heating without interfering with the primary laser beam. Alternatively, in other embodiments, the external illumination may be projected onto the saturable absorber 724 from the side, eliminating the need for a dichroic mirror 706. This side-illumination approach may provide a simpler design while still achieving effective heating of the saturable absorber 724.

[0106] In addition to, or as an alternative to the external heating provided by an illuminator 702, the energy from the laser pump diodes can also be utilized to heat the saturable absorber 724. For instance, the optical energy emitted by the pump diodes can be partially absorbed by the saturable absorber 724, raising its temperature and contributing to its operational behavior. This method leverages existing laser system components to achieve thermal management without requiring a dedicated external illumination source, such as illuminator 702.

[0107] By controlling the heating of the saturable absorber—whether through external illumination, pump diode energy, or a combination of both—this embodiment ensures precise tuning of the saturable absorber’s absorption and transmission properties. Proper thermal management of the saturable absorber 724 enables consistent Q-switching performance and stable laser pulse generation. Furthermore, active control of the saturable absorber’s temperature impacts the timing and energy dynamics of laser pulse emissions, enhancing the performance and reliability of the overall laser system.

[0108] In one implementation, the external illuminator 702 operates at a wavelength different from the laser’s lasing wavelength. To direct the illumination onto the saturable absorber 724 without interfering with the laser beam traveling through the optical cavity, the dichroic mirror 706 is configured to reflect the illumination from the external illuminator 702 onto the saturable absorber 724 while allowing light at the laser’s operating wavelength toAttorney Docket No. 10880.024WO1 transmit through. This approach ensures that the optical path of the laser is undisturbed while still achieving effective illumination of the saturable absorber 724.

[0109] Alternatively, or in addition to the external illumination method, heat may be applied to the saturable absorber using optical energy from the laser pump diodes. In this approach, the pump diodes, which provide energy to the laser gain medium, also emit some optical energy that can be absorbed by the saturable absorber 724, contributing to its heating. This method takes advantage of existing system components and provides a means to heat the saturable absorber 724 without requiring additional external equipment.

[0110] By employing one or more of these heating techniques, the Q-switch functionality and performance of the laser system are enhanced. Controlling the heat applied to the saturable absorber 724 allows for fine-tuning of its operational characteristics, including its transition from high absorption to high transmission as the intracavity light intensity increases. Effective thermal management of the saturable absorber 724 improves the stability and reliability of Q-switching operations and enables precise control over the timing and dynamics of laser pulse emissions, resulting in consistent and high-quality laser output.

[0111] For passively Q-switched laser embodiments employing saturable absorbers, the pump energy delivered to the system is controlled by adjusting the duration of the pump diode pulses. FIGS. 6A-6C illustrate the behavior of the laser output for different diode pump pulse durations and illustrates a technique referred to herein as “ghost pulsing”. Ghost pulsing maintain consistent heating and thermal lensing in the system for multiple operating conditions. In these embodiments, when the diode pulse duration is shorter than the time required to sufficiently reduce the absorption of the saturable absorber 724, as shown in FIG. 6A, no laser pulse is emitted. In such cases, the gain medium 122 and saturable absorber 724 are heated by the pump diode energy but insufficient emission intensity is generated to initiate Q-switching.

[0112] In FIG. 6B, the diode pulse duration is sufficiently long to provide the energy required to reduce the saturable absorber’s absorption and initiate stimulated emission from the gain medium 122. This results in a single laser output pulse. Importantly, it is necessary to ensure the diode pulse duration is long enough to guarantee that laser emission occurs despite any jitter present in system dynamics. However, it is preferable to avoid excessively long diode pulses, as shown in FIG. 6C, because this can lead to the buildup of energy in the gain medium following the initial laser pulse, resulting in unwanted after pulses.Attorney Docket No. 10880.024WO1

[0113] FIGS. 7A-7C illustrate how ghost pulsing involves the insertion of short diode pump pulses (e.g., “ghost pulses”) between the main diode pulses used for laser pulse emissions. For example, FIG. 7A is a timing diagram of diode pulses, laser pulses, and diode “ghost pulses”, FIG. 7B is a timing diagram of capacitive charge of a diode driver, and FIG. 7C is a timing diagram of accumulated heat between laser pulses, in one exemplary embodiment.

[0114] The ghost pulses are intentionally kept short enough to avoid initiating laser Q- switching, thereby preventing undesired laser emission. However, these ghost pulses still deposit heat into the gain medium 122 and / or saturable absorber 724, helping maintain thermal lensing effects when operating at reduced repetition rates or with varying laser pulse periods.

[0115] This method of ghost pulsing is particularly impactful for passively Q-switched lasers because, in addition to its effect on the gain medium’s thermal lensing, it interacts with the saturable absorber 724. The saturable absorber 724 is highly sensitive to thermal lensing effects caused by accumulated heat. Ghost pulses contribute to heating the saturable absorber not only through residual pump diode light absorption but also by absorbing spontaneous emission from the laser gain medium. In this way, ghost pulses serve both to maintain the thermal state of the saturable absorber and to ensure consistent laser divergence across varying operating conditions.

[0116] Even in some active Q-Switching embodiments, a saturable absorber can be added as a mechanism to provide a pulse energy dependent thermal lensing effect that can be controlled through ghost pulsing. In these embodiments, the saturable absorbers may not be needed for Q-switching but are used to permit adjusted thermal lensing with ghost pulses to compensate for variations in laser PRF, or environmental temperatures, or operating conditions while providing stable operating performance (e.g., beam quality, beam divergence, pulse lengths, or pulse energy). In other active Q-switching embodiments without a saturable absorber, sufficient thermal lensing can be controlled with ghost pulsing in the gain medium.

[0117] As shown in FIG. 7C, when the heat deposited into the system, including the saturable absorber 724 and gain medium 122, is proportional to the total diode pump energy, the total heating power can be approximated as proportional to the sum of all diode pulse durations within a laser pulse period and inversely proportional to the laser pulse period. Given this relationship, ghost pulse durations can be calculated to maintain a consistent heating power equivalent to that at a maximum pulse repetition rate (or shortest laser pulse period, H^IJKEL,MKN).Attorney Docket No. 10880.024WO1 The total accumulated duration of the ghost pulses ∑HLBapplied during a laser pulse period τperiodcan be calculated using the

[0118] ∑HLB = =PQRSTUV,WTXPQRSTUV − 1> HLYwhere τd0 is the diode pulse duration for producinglaser output

[0119] ghost pulses may be equally spaced between laser pulses, and their individual durations selected to maintain the desired heating power. For instance, five evenly spaced ghost pulses may be employed, where each pulse’s duration satisfies the above relationship. Other considerations are factored into the timing of ghost pulses, such as allowing sufficient time between ghost pulses for the gain medium to dissipate its accumulated energy, avoiding unintended laser emissions. Additionally, ghost pulses should be timed such that the diode driver capacitors have adequate time to recharge between pulses—particularly the first ghost pulse and the subsequent main laser pulse, as shown in FIG. 7B.

[0120] Ghost pulsing can take different temporal shapes and amplitudes to meet system requirements. For example, a higher amplitude may be preferred for efficient electrical-to- optical conversion. However, lower current diode ghost pulses can still serve an auxiliary purpose, such as maintaining diode temperatures, though this approach may yield less optical emission and address different objectives.

[0121] In some embodiments, the heating power from ghost pulses may be adjusted dynamically to account for variations in ambient conditions, pulse energy requirements, or desired repetition rates. These adjustments may be determined using pre-calculated lookup tables or based on factory measurements and calibrations. Lookup parameters may include dependencies on ambient temperature, gain medium temperature, diode temperature, and saturable absorber temperature. This allows for precise tuning of ghost pulse sequences to accommodate different operating scenarios.

[0122] Additionally, ghost pulsing may be employed to maintain stable laser divergence across rapid changes in pulse repetition frequency (PRF) or even between coded laser pulses with varying separations. By maintaining consistent thermal lensing through appropriately selected ghost pulses, divergence can be maintained or dynamically varied for specific applications. For example, a laser may be engineered to achieve high divergence for broad illumination applications before transitioning to operating conditions with reduced divergence.Attorney Docket No. 10880.024WO1

[0123] FIGS. 8A and 8B illustrate heating with and without the use of ghost pulses, in one exemplary embodiment. FIG. 8A illustrates the impact of no ghost pulsing on the stability of laser divergence as a function of ambient temperature for a laser operating at different repetition rates. Specifically, the measurements demonstrate divergence performance for one laser embodiment at repetition rates of 8.3 Hz (plots 802) and 20 Hz (plots 804) under different heating and operational conditions.

[0124] In FIG. 8A, the divergence curves for the laser operating without ghost pulsing show that the divergence characteristics as a function of ambient temperature differ significantly between the two repetition rates. This variability arises due to disparate thermal states within the laser cavity at different repetition rates, leading to inconsistent thermal lensing effects in the gain medium and / or other transmissive optical components. These inconsistencies are particularly detrimental in applications requiring stable beam characteristics across varying operating rates and environmental temperatures.

[0125] In contrast, FIG. 8B demonstrates the use of ghost pulsing to stabilize the thermal state of the laser system and thereby reduce divergence variability. With ghost pulsing applied, the divergence curves for repetition rates of 10 Hz (plot 806) and 20 Hz (plot 808) become nearly identical across the same range of ambient temperatures. By providing additional heating to balance thermal effects, ghost pulses ensure that the thermal lensing within the cavity components, such as the gain medium 122 and / or saturable absorber 702, remains consistent regardless of the laser pulse repetition rate. This consistent thermal management results in more stable laser divergence across different operating rates.

[0126] The reduction of divergence variability via ghost pulsing enables stable operation of the laser system, which is critical for many applications. For example, applications requiring precision targeting or consistent beam quality benefit greatly from the ability to maintain stable divergence across varying repetition rates. Additionally, adjustments to ghost pulsing parameters can be made to further counter the effects of ambient temperature fluctuations on divergence. This can help flatten the divergence curves shown in FIG. 8B, resulting in even greater consistency across a wide temperature range.

[0127] It is noted that while ghost pulsing minimizes divergence variability, any residual divergence variation can often be corrected with additional static external optics. These optics, if applied, can provide further adjustments to the output beam to meet specific applicationAttorney Docket No. 10880.024WO1 requirements. The combination of ghost pulsing for thermal management and external optics for fine adjustments ensures that the laser system can maintain high beam quality and operational precision in diverse conditions. These experimental results underscore the effectiveness of ghost pulsing as a technique for stabilizing laser divergence and managing thermal effects in passively Q-switched laser systems.

[0128] With this in mind, we return to the discussion of FIG. 1 to illustrate to the operational characteristics of the laser resonator embodiments disclosed herein, including the laser resonator 700 of FIG. 5. Again, FIG. 1 illustrates a 6-mirror non-planar configuration that rotates the spatial intensity pattern of the laser beam by 90 degrees on every round trip through the cavity. This embodiment provides a significant advantage in that the spatial rotation of the intensity pattern is achieved passively, without relying on any active polarization rotation mechanisms, such as Pockels cells or waveplates.

[0129] In this 6-mirror setup, the placement and orientation of the mirrors create an intensity map rotation during each round trip of light within the resonator 120. Specifically, the inclusion of an out-of-plane reflector ensures that each round trip achieves a precise 90-degree image rotation. This rotation enables the system to average over aberrations and imperfections in the beam profile across consecutive round trips, leading to improved beam quality and uniformity.

[0130] However, as shown in this embodiment, the specific 90-degree image rotation is not a limiting feature. Alternative geometries and configurations may be employed to achieve different image rotation angles per round trip. For example, by modifying the placement of Cavity Mirror 4 (110) or by replacing this mirror with an optical element such as a dove prism, the round trip rotation can be tuned to other selected angles. These variations enable customization of the beam rotation to suit different operational needs and performance objectives.

[0131] The use of an even number of reflectors within a ring cavity, as in the described configuration, supports the generation of an intensity pattern rotation without additional spatial inversion of the beam profile during round trip radiation propagation. Each reflection introduces an inversion that can be mathematically described as a transform matrix with a determinant of -1. After an even number of reflections—which is the case in embodiments like the 6-mirror configuration—the cumulative product of the determinants from each transformation equals +1.Attorney Docket No. 10880.024WO1 This equivalence results in a net image rotation rather than an inversion. The degree of rotation achieved (e.g., 90 degrees, 180 degrees, or zero degrees) depends on the arrangement of the cavity reflectors and associated optical paths.

[0132] For embodiments where the net image rotation is zero degrees, additional optical features or modifications to the reflector positioning may be introduced to achieve a desired non- zero rotation. Specifically, the placement of at least one reflector out of the resonator’s primary plane introduces a controlled angular rotation to the beam. This out-of-plane reflector, along with the associated optical path, can be configured to create a specific amount of spatial rotation, such as 90 degrees, as described herein.

[0133] FIG. 9 illustrates an exemplary embodiment of a laser gain medium 400 that may be used to implement the gain medium 122 of FIG. 1. In this embodiment, the gain medium 400 is designed in the shape of a rectangular cuboid. In this example, the gain medium 400 features a square-shaped, physically symmetrical cross-section. While the square configuration is discussed here as an illustrative example, it is not limiting and is used primarily to demonstrate an integrated, axially symmetrical phase distortion accumulated over multiple round trips. Alternative embodiments may produce differing phase distortions or image rotations per round trip, resulting in varied averaged phase combinations.

[0134] In this embodiment, intra-cavity laser radiation 402 enters the gain medium 400 through one face 404 and exits through an opposite face 406. The remaining faces of the gain medium (e.g., 408, 410, 412, and 414) are subject to thermal fluxes that either heat or cool the gain medium. These heat fluxes are shown as orthogonally applied on the square cross-section but are merely examples, as other cross-section geometries may be employed. Additionally, in some embodiments, the gain medium may be interfaced with another material, such as a pump light conduit, which may partially or completely cover one or more faces.

[0135] In the exemplary setup, thermal fluxes serve to regulate the temperature of the gain medium:

[0136] Heated faces (414 and 410) are exposed to thermal fluxes Q1 and Q2.

[0137] Cooled faces (412 and 408) are subjected to thermal fluxes Q3 and Q4, which have negative values, as represented by outward-directed arrows.

[0138] The heating fluxes (Q1 and Q2) can result from input heat generated by external optical pumping of the crystal rod, such as light introduced from a pump diode or pump cavity.Attorney Docket No. 10880.024WO1 These fluxes may also include contributions from direct conduction (e.g., physical connections to heat sources or heaters / coolers) or convection-based heat. Conversely, the cooling fluxes (Q3 and Q4) may originate from either active cooling elements like electrical or solid-state coolers or from passive cooling sources such as heat sinks, liquid baths, or solid bodies.

[0139] In some embodiments, Q1 and Q2 can be configured to have approximately equal magnitudes; a similar balance can apply to Q3 and Q4. Alternatively, thermal fluxes can be adjustable for individual customization. For example, fluxes Q3 and Q4 may be electronically controlled through a system that adjusts temperature or heat fluxes on surfaces 408 and 412. Likewise, thermal adjustments on faces 414 and 410 may involve increasing pump diode output or altering coupling of pump light into the gain medium.

[0140] The optical phase shift accumulated as light propagates through the gain medium can be functionally described by the relation:

[0141] Z)[, \+ = ]^)[+ − _D)\+. Here, α and β represent scaling coefficients, while f(x)and g(y) are distortion functions in two perpendicular directions.

[0142] In some scenarios, the radiation pattern rotates by 90 degrees after each round trip, without inversions. After four such rotations, the accumulated optical phase shift approximates:

[0143] Za,b)c [, \+ = ]d^)[+ + ^)−[+e − _dD)−[+ + D)[+e + ]d^)\+ + ^)−\+e −_dD)andunder 90-degree rotations.

[0144] In one example, the phase shift cancels out entirely after four round trips under specific conditions. For instance, phase distortion cancels when horizontal and vertical phase distortions balance (e.g., ]^)f+ ≈ _D)f+, or ]^)f+ ≈ _D)−f+ ). This cancellation occurs if theconfiguration adheres to general

[0145] h^ + h^ + hi + ha ≈ 0,

[0146] and when the differences between the heating and cooling fluxes satisfy:

[0147] |h^ − h^| ≈ |hi − ha|.

[0148] Moreover, phase distortion cancellation is also possible if the functional sums satisfy:

[0149] D)−[+ + D)[+ = k and ^)[+ + ^)−[+ = l even if ]^)f+ ≠ _D)f+, or ]^)f+ ≠_D)−f+.Attorney Docket No. 10880.024WO1

[0150] In a more generalized case, near the center of the gain medium, the phase distortion may be approximated using polynomial functions:

[0151] Z)[, \+ = ]^)[+ − _D)\+, where ]^)[+ = ] i ^i[ + ]^[ + ]^[ + ]Y and_D)\+ = _i\i + _^\^ + _^\ + _Y.

[0152] When integrated over four 90-degree rotations, the dominant distortion terms reduce to:

[0153] Za,b) ^ ^c [, \+ = 2)]^ − _^+)[ + \ + + 4)]Y − _Y+.+)[^ + \^+ represents asymmetric focus effect if ]^ ≈ _^, ensuring distortions are neutralized. For configurations wherethese adjustments are not sufficient, additional intra-cavity focusing elements may be used to compensate for residual optical power deviations.

[0155] Finally, the accumulated phase distortion can be actively controlled by manipulating the heating fluxes (Q1 and Q2) or cooling fluxes (Q3 and Q4) along the length or specific regions of the gain medium. Local control of thermal fluxes allows for dynamic adjustments, producing desired magnification and compensating for phase distortions across multiple round trips. Individual sections of the gain medium may also be independently controlled, providing further granularity for performance optimization.

[0156] FIG. 10 illustrates the effects of successive image rotations that occur over multiple round trips within the laser resonator. These rotations are composed of inversions that, when combined during a round trip, result either in a net rotation or a simple inversion. By carefully incorporating specific inversions into the optical path of the cavity—such as in the embodiments described herein—the image rotation of the laser light helps to average out aberrations present in the resonator or those induced, controlled, or tuned as outlined elsewhere. These aberrations may include factors such as magnifications, hot spots, or regions of undesired stability or instability.

[0157] For illustrative purposes, the described embodiments utilize 90-degree image rotations (500) to demonstrate the impact of such rotations on the particular cavities featured herein. Choosing 90-degree rotations allows complete averaging of the laser beam’s image distortion after just four round trips through the resonator. This example shows how careful selection and design of cavity configurations can effectively average out both uncontrolledAttorney Docket No. 10880.024WO1 aberrations and those induced or tuned intentionally. For instance, the optical power or magnification of a cavity element may include axial components or distortions that are diminished through these successive image rotations (500).

[0158] To visualize this process, the figure shows a radiation image pattern, marked as R. Starting in the upright position (502), the image undergoes sequential 90-degree rotations through successive round trips, moving to positions 504, 506, and 508, before returning to the upright position (502) after four round trips.

[0159] Although this explanation focuses on the simplified case of four rotations at 90 degrees, alternative rotation schemes are possible. These alternatives may involve other rotational angles per round trip, requiring a larger number of round trips to effectively average or cancel phase or amplitude aberrations introduced during individual round trips. However, for cases where short laser pulse durations are critical, constraints on the number and degree of rotations per round trip must be considered to ensure practical operation with effective cancellation of aberrations.

[0160] The figure demonstrates that the 90-degree image rotations (500) transition the upright image R in position 502 into position 504 (rotated 90° clockwise), then to an upside- down R in position 506 (rotated another 90°), and subsequently to position 508 (rotated 270° from the starting position). After completing four rotations, the pattern returns to position 502, completing a full cycle. Importantly, the process involves controlled rotations that do not add additional inversions beyond inherent rotational effects. For example:

[0161] The transition from position 502 to 504 is a simple 90-degree rotation, not an inversion across a horizontal axis.

[0162] Similarly, the transition from 504 to 506 yields an upside-down R without any additional inversion. The orientation of the upside-down R at 506 naturally cancels the distortion of the initial upright R at 502, effectively balancing the patterns after just two round trips.

[0163] The subsequent rotation to 508 and back to 502 continues this cancellation process, showcasing complete aberration averaging after four total round trips.

[0164] By ensuring precise construction of the resonator, such as incorporating one or more out-of-plane reflectors, the design achieves the proper rotations required to effectively average radiation patterns across multiple round trips. While the example provided illustrates the simplified case of four 90-degree rotations, the principles extend to a broad range ofAttorney Docket No. 10880.024WO1 configurations, including those requiring different rotation angles per round trip and / or different numbers of round trips to complete the desired averaging of aberrations.

[0165] FIG. 11 is a diagram 600 that illustrates the stability of laser resonators, particularly focusing on a class of resonators operating with a roundtrip magnification of 1.0, such as plane-parallel or equivalent cavities. The graph includes a dotted line representing unity slope that passes through the origin, indicating the critical plane-parallel magnification condition. While the diagram depicts the stability parameters for example linear cavities with two end reflectors, the concept extends to ring resonators described herein, which may incorporate multiple reflectors—for instance, six or eight reflectors.

[0166] When magnification or other aberrations are present in the cavity, the laser beam may deviate from its intended optical path, potentially “walking off” at specific points within the cavity. For example, excessive magnification can enlarge the beam beyond the aperture limits of the system, resulting in apodization, diffraction, reflection, or other forms of light loss.

[0167] The term aperture refers not only to physical apertures but also to functional apertures. For instance, if part of a gain medium cannot provide amplification for transmitted light due to lack of excitation, this inactive area functions as an aperture. Although light can physically pass through the entire gain medium, the beam itself would not survive in regions without gain over multiple round trips.

[0168] Similarly, resonator components with optical powers that are not symmetric may introduce phase distortions that accumulate over multiple round trips, leading to a net magnification effect. Certain embodiments described herein specifically leverage these functional dynamics to counteract undesirable resonance effects, such as operating near or beyond the critical plane-parallel magnification condition.

[0169] Plane-parallel cavities are recognized as particularly challenging to align, as even slight misalignments of the reflective elements can cause the light to “walk off” the optical path after just a few round trips. This misalignment renders such cavities ineffective for lasing operations. Stability is achieved when the net magnification conditions fall below the asymptotes of the graph, within the shaded stability region. However, near plane-parallel conditions, aberrations, heating gradients, and thermal effects can result in regions of net magnification instability, causing the radiation to diverge and reduce beam quality. As a result, conventionalAttorney Docket No. 10880.024WO1 resonator designs typically avoid operating near the plane-parallel dotted line, where net magnification equals 1.0.

[0170] Neighboring regions close to this critical magnification condition, as shown by the dotted circle (602) in FIG. 11. For most systems, tolerances limit operational magnification closer to values like 0.9, 0.95, or 0.99, ensuring that instabilities caused by aberrations or perturbations are minimized.

[0171] In traditional designs, resonators with multiple optical components or larger resonators (beyond microscales) are carefully constructed to avoid such critical magnification conditions. For conventional resonators with polarization output coupling, areas near magnification = 1.0 are typically unstable due to perturbation instabilities, which amplify aberrations and result in beam divergence and power loss.

[0172] However, the embodiments described herein employ techniques that enable stable operation near or even beyond magnifications of 1.0. Using specialized resonator designs and assembly methods, these systems can achieve reliably stable laser performance even under conditions traditionally considered unstable. This approach is referred to as operating under a “critically unstable” mode, where unstable conditions are deliberately managed and utilized to enable desired performance.

[0173] For example, stability management in these resonators may: identify and controls magnification instabilities through techniques such as apodization or precise optical component alignment; incorporate methods to balance aberrations caused by inherent optical power or non- symmetric phase distortions over successive round trips; and leverage advanced design features that accommodate instability while maintaining the resonator’s capacity to output pulsed laser light with consistent quality.

[0174] In graph 600, the dotted area 602 around the unity slope highlights the operational boundary for these systems. Unlike conventional resonators that avoid such conditions, the described embodiments actively control and utilize these regions, which often fall outside traditional stability zones. For instance:

[0175] Techniques described here can stabilize resonator operation even with net operational magnifications near or above 1.0 by accounting for perturbations and heat-related effects.Attorney Docket No. 10880.024WO1

[0176] Adjusting magnification and optimizing assembly enables designs that support stable pulsed laser output, even under conditions previously deemed unsuitable for consistent laser operation.

[0177] Lastly, those skilled in the art may directly correlate descriptions of magnification control herein with those of perturbation instability management—as stability parameters and perturbation mitigation represent closely linked aspects of resonator optimization. The described methodologies simplify this process, ensuring both functional robustness and high laser performance, even when operating in these critically unstable regions.

[0178] Resonators are typically designed to avoid plane-parallel conditions in order to maintain stability, but the embodiments described herein intentionally introduce a slight and carefully tuned deviation into unstable magnification conditions for specific advantages. Traditionally, resonators operating at or near plane-parallel conditions are avoided because phase distortions or other aberrations within the resonant optical path can create regions of stability that concentrate lasing action in certain areas, potentially causing overheating or damage to portions of the optical path. Additionally, plane-parallel or nearly plane-parallel configurations complicate laser design due to increased sensitivity to misalignment. When resonators operate at or near the plane-parallel condition, they are critically stable, meaning even minor misalignments, aberrations, or uncontrolled lensing can compromise functionality. Reflectors in resonators operating near plane-parallel conditions require significant alignment efforts to ensure proper operation. However, the embodiments described herein allow resonators to operate very close to the plane-parallel condition, while finely tuning the magnification condition to prevent misalignments from causing failure.

[0179] In the described embodiments, the resonator is designed to function very close to the plane-parallel condition or in an inherently unstable state that necessitates additional balancing for proper operation. This balanced unstable condition, referred to as “critically unstable” (or “critical instability”), represents the controlled and fine-tuned instability of the resonator’s operation. By precisely balancing the resonator in this critically unstable condition, these embodiments effectively extract significant energy from the gain medium, such as a crystal.

[0180] In some embodiments, elements defining the resonant optical path introduce optical powers or aberrations that act along one axis and / or in a specific rotational direction ofAttorney Docket No. 10880.024WO1 the resonator. Such aberrations may affect astigmatism or differential focusing on one axis of the beam during a single round trip. Over multiple round trips, and by utilizing polarization- preserving image rotation modes, these aberrations may combine and average out, resulting in a net round-trip magnification.

[0181] The described elements and methods enable tuning of the overall magnification to reach this critically unstable condition while balancing the described instabilities, aberrations, and magnifications of the resonant optical path during operation. Additionally, methods are described for tuning resonators to achieve critically unstable operational conditions that simplify assembly. These methods streamline an already efficient assembly process and reduce the impact of misalignments, which is especially critical when producing compact resonators.

[0182] As demonstrated in FIG. 12, misalignments in the described resonators are corrected over multiple round trips using image rotation. For instance, with a 90-degree rotation per round trip, a misalignment that shifts the beam to the left will be offset after two round trips (180 degrees of total rotation), such that every alternate round trip serves to correct the misalignment.

[0183] In the illustrated example, light initially travels along path P1 and encounters a flat reflector with an angular misalignment. This misalignment causes the reflected light to follow a misaligned path P2 at a deviated angle relative to the ideal optical path. As the light continues through the resonator’s cavity for one or more round trips, it returns to the misaligned reflector at an angle altered by the first deviation. On subsequent reflection, a second deviated angle is introduced to the beam trajectory; however, it is offset by the 180-degree rotational correction from the previous deviation. As a result, the beam is redirected along the ideal self- corrected path P4.

[0184] Thus, as shown in FIG. 12, image rotation within the described non-planar resonator significantly improves the tolerance for misalignment, simplifying fabrication and reducing costs. This configuration also supports plane-parallel equivalent cavity modes, enabling large mode areas for compact and efficient energy extraction. Furthermore, by requiring fewer components and reducing the need for focus-critical alignments, the overall system becomes more robust and cost-effective.Attorney Docket No. 10880.024WO1

[0185] In various embodiments of the laser resonator’s 100 and 700, a prism may replace certain portions of the resonator to reduce the number of components, increase the round-trip optical path length, and simplify assembly processes.

[0186] The depicted prism and resonator configuration includes three reflections within the prism (e.g., a three-bounce prism), which consist of two in-plane total internal reflections and one out-of-plane total internal reflection. As a result, the prism introduces three inversions—one from each reflection—along with an image rotation caused by the out-of-plane reflection.

[0187] In some embodiments, the prism is designed to substitute specific sections of the resonator, with its functionality replacing or augmenting that of the substituted components. Alternatively, additional optical components may replace the functions of the substituted sections. For instance, to facilitate image rotation in the optical path, the prism can be configured such that at least one of the total internal reflections occurs out of the plane of the resonator. In one embodiment, the prism incorporates at least some of the out-of-plane elements. In another embodiment, the prism contains all out-of-plane elements of the optical cavity.

[0188] In one embodiment, the prism is configured to receive and return light along the same optical plane as the rest of the resonator. In another embodiment, the prism receives light on one plane and returns it on another. For example, an external in-plane reflector may be added outside the prism to redirect the optical path back to a different plane of the resonator. The number of reflections within the prism may vary depending on the design, such that in one embodiment the prism contains an odd number of reflections, while in another embodiment it contains an even number of reflections.

[0189] The prism serves more purposes than merely combining multiple reflections into a single component. For example, a corner cube alone would not achieve the same optical effects in the resonator without additional changes or elements being introduced into the optical path. Rather, the prism’s reflections and internal optical path offer several additional effects beyond basic reflections and inversions. Replacing components with a prism requires careful coordination of the optical effects, such as image rotation and beam aperture control, to ensure the proper functioning of the resonator.

[0190] Furthermore, prisms may provide additional functionalities within a single optical element, such as producing optical gain, magnification, aperture control, or other beamAttorney Docket No. 10880.024WO1 transformations. In one embodiment, multiple prisms are utilized, each incorporating different portions of the optical path or generating distinct optical transformations within the resonator.

[0191] FIG. 13 depicts an embodiment of a 6-reflection non-planar resonator, which incorporates a three-bounce prism that houses the entirety of the optical path within one of the planes. This configuration utilizes a prism with one out-of-plane reflection and two in-plane reflections, ensuring it maintains functional equivalence to the individual optical elements it replaces within the resonator. Additionally, prism-based designs can serve to extend the optical path length, thereby increasing the cavity’s fundamental pulse length. In the example shown, the plane containing less than half of the resonator’s round-trip optical path is fully enclosed within the prism.

[0192] In this embodiment, light traveling along the optical path both enters and exits the prism on the same plane as the rest of the optical path. While inside the prism, the light undergoes three total inversions, one of which is caused by the out-of-plane reflection, resulting in an associated image rotation.

[0193] The internal reflections within the prism are specifically designed to perform the functional role of other components in the resonator. For instance, an internal reflection within the prism can function equivalently to a mirror by redirecting the beam (e.g., in-plane or out-of- plane) and contributing to the image rotation required by the cavity, as described in further detail herein.

[0194] In one embodiment, parts of the prism itself, or one or more of its facets, may also act as a functional aperture to shape the laser beam profile, either within or outside the prism. In another embodiment, a separate cavity element or a combination of elements may be used to provide a physical aperture, implemented to achieve the desired beam characteristics as further detailed herein.

[0195] FIG. 14 illustrates an embodiment that incorporates a five-bounce prism, which substitutes for and contains a longer segment of the resonator’s optical path. In this configuration, the five reflections within the prism replace a portion of the optical path in an 8- reflection resonator. As described herein, the prism is designed or installed to maintain functional equivalency with the portion of the resonator that it replaces. Moreover, the larger prism extends the optical path length within the cavity, thereby increasing the round-trip time and the fundamental pulse length of the laser pulses produced. In this example, the prismAttorney Docket No. 10880.024WO1 includes two in-plane reflections that direct the optical path to and from a different plane of the resonator, while the entire optical path along that plane is enclosed within the prism. Additionally, the prism contains three out-of-plane reflections, resulting in associated image rotation due to light travelling into and out of the alternate plane.

[0196] The use of a five-bounce prism can also increase the resonator’s volume, offering design trade-offs between increased pulse length and compact physical size. In some embodiments, additional volume may be created outside the resonator for output optics, such as periscopes or other external optical configurations. These variations in design allow for flexibility in adjusting features such as resonator size, pulse length, and energy output based on the requirements of a particular application.

[0197] FIG. 15 presents an alternative view of the five-bounce prism, showing the primary resonator plane oriented perpendicular to the image and the alternate plane of the resonator contained within the prism lying parallel to the image. This view highlights the prism’s relative “L” shape, which extends along two orthogonal axes. In certain embodiments, when space constraints are less critical, the expanded optical path length provided by this design may outweigh the additional volume in the orthogonal direction. Using a compact prism with total internal reflections along the orthogonal plane allows for an elongated optical path without significantly sacrificing the overall compactness of the resonator.

[0198] Alternative configurations may also adjust the optical path to meet specific output requirements. This includes integrating the resonator with external optics, such as output periscopes, to modify and condition the laser output as needed for an application. The flexible design of the resonator enables seamless integration of internal and external optical components, providing a highly adaptable platform for various uses.

[0199] FIG. 16 is a flowchart of a process 1100 of a laser system, such as laser system 10 of FIG. 1A, in one exemplary embodiment. In this embodiment, one or more of a plurality of laser diodes, such as laser diodes 24 of FIG. 1A, are operable to pump a gain medium, such as gain medium 18 of FIG. 1A, with laser diode pulses to stimulate the gain medium and resonate laser light through the gain medium between a reflector and a Q-switch device, such as Q- switched device 22 of FIG. 1A, in the process element 1102. These diode pulses (e.g., pulses 12 of FIG. 1) cause the gain medium to emit laser pulses through an output coupler (e.g., output coupler 20 of FIG. 1A) that is optically coupled to the Q-switch device, in the process elementAttorney Docket No. 10880.024WO1 1104. During this operation, a controller, such as the controller 30 of FIG. 1A, is operable to direct one or more of the laser diodes to insert one or more diode ghost pulses, such as ghost pulses 16 of FIG. 1A, into the laser system between the laser diode pulses that result in the emitted laser pulses, in the process element 1106.

[0200] These ghost pulses may be used to control the operating parameters of the laser system. For example, the controller may direct one or more of the laser diodes to pump the gain medium with diode ghost pulses in between emitted laser pulses to change a temperature of the gain medium. In this regard, the controller may change the operating parameters of the laser system to ensure a desired laser pulse emission (e.g., by controlling divergence of the laser light emitted from the laser system). As mentioned, the controller may be used to predict laser pulse emissions to control the operating parameters of the laser system, monitor lasing operations of the laser system to control the operating parameters of the laser system, monitor environmental conditions of the laser system to control the operating parameters of the laser system during operation and / or before operation, and the like.

[0201] FIGS. 17-20 illustrate an embodiment of a resonator with an output periscope designed to modify or condition the laser output. The output periscope may include reflectors, lenses, or other intermediate optics to modify the beam’s magnification or direction. As shown in FIG. 17, the periscope 1202 is coupled to the resonator output and acts as an external optical structure. It includes a set of optical components—such as an intermediate lens and an output lens—to alter the beam profile, magnify the output, or change its direction. The gain medium 1220 used in this configuration incorporates pump light chambers on two sides and functions similarly to the general symmetrical gain medium described previously. Pockels cells 1208 are also included for controlling the laser output delay, and the resonator reflectors 1204 and other components (e.g., polarizing beam splitter 1216) perform similar functions to those described in earlier embodiments.

[0202] FIGS. 18 and 19 present additional views of the configuration, illustrating the compact nature of the resonator and its periscope from top and side perspectives. These views highlight how the periscope fits neatly along the resonator’s primary plane while extending across an orthogonal axis to accommodate additional output optics. While the configuration introduces additional volume, this may be advantageous for applications requiring large or customizable output optics.Attorney Docket No. 10880.024WO1

[0203] FIG. 20 provides another perspective, with the primary resonator plane aligned with the image plane while the out-of-plane reflector projects beneath this plane. This view demonstrates how the resonator design balances compactness with flexibility, enabling integration with external optical elements to adapt the laser system to various applications. Different configurations of the resonator and external optics can be readily implemented to meet the requirements of specific use cases.

[0204] Any of the above embodiments herein may be rearranged and / or combined with other embodiments. Accordingly, the concepts herein are not to be limited to any particular embodiment disclosed herein. Additionally, the embodiments can take the form of entirely hardware or comprising both hardware and software elements. Portions of the embodiments may be implemented in software, which includes but is not limited to firmware, resident software, microcode, etc. FIG. 21 illustrates a computing system 2100 in which a computer readable medium 2106 may provide instructions for performing any of the methods disclosed herein.

[0205] Any of the various computing and / or control elements shown in the figures or described herein may be implemented as hardware, as a processor implementing software or firmware, or some combination of these. For example, an element may be implemented as dedicated hardware. Dedicated hardware elements may be referred to as “processors,” “controllers,” or some similar terminology. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” or “controller” should not be construed to refer exclusively to hardware capable of executing software, and may implicitly include, without limitation, digital signal processor (DSP) hardware, a network processor, application specific integrated circuit (ASIC) or other circuitry, field programmable gate array (FPGA), read only memory (ROM) for storing software, random access memory (RAM), non-volatile storage, logic, or some other physical hardware component or module.

[0206] In one embodiment, instructions stored on a computer readable medium direct a computing system of any of the devices and / or servers discussed herein to perform the various operations disclosed herein. In some embodiments, all or portions of these operations may be implemented in a networked computing environment, such as a cloud computing system. Cloud computing often includes on-demand availability of computer system resources, such as dataAttorney Docket No. 10880.024WO1 storage (cloud storage) and computing power, without direct active management by a user. Cloud computing relies on the sharing of resources, and generally includes on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service.

[0207] FIG. 21 depicts one illustrative cloud computing system 2100 operable to perform the above operations by executing programmed instructions tangibly embodied on one or more computer readable storage mediums. The cloud computing system 2100 generally includes the use of a network of remote servers hosted on the internet to store, manage, and process data, rather than a local server or a personal computer (e.g., in the computing systems 2102-1 - 2102- N). Cloud computing enables users to use infrastructure and applications via the internet, without installing and maintaining them on-premises. In this regard, the cloud computing network 2120 may include virtualized information technology (IT) infrastructure (e.g., servers 2124-1 - 2124-N, the data storage module 2122, operating system software, networking, and other infrastructure) that is abstracted so that the infrastructure can be pooled and / or divided irrespective of physical hardware boundaries. In some embodiments, the cloud computing network 2120 can provide users with services in the form of building blocks that can be used to create and deploy various types of applications in the cloud on a metered basis.

[0208] Various components of the cloud computing system 2100 may be operable to implement the above operations in their entirety or contribute to the operations in part. For example, a computing system 2102-1 may be used to perform analysis of data, and then store that analysis in a data storage module 2122 (e.g., a database) of a cloud computing network 2120. Various computer servers 2124-1 - 2124-N of the cloud computing network 2120 may be used to operate on the data and / or transfer the analysis and / or the data to another computing system 2102-N.

[0209] Some embodiments disclosed herein may utilize instructions (e.g., code / software) accessible via a computer-readable storage medium for use by various components in the cloud computing system 2100 to implement all or parts of the various operations disclosed hereinabove. Examples of such components include the computing systems 2102-1 - 2102-N.

[0210] Exemplary components of the computing systems 2102-1 - 2102-N may include at least one processor 2104, a computer readable storage medium 2114, program and data memory 2106, input / output (I / O) devices 2108, a display device interface 2112, and a network interface 2121. For the purposes of this description, the computer readable storage medium 2114Attorney Docket No. 10880.024WO1 comprises any physical media that is capable of storing a program for use by the computing system 2102. For example, the computer-readable storage medium 2114 may be an electronic, magnetic, optical, electromagnetic, infrared, semiconductor device, or other non-transitory medium. Examples of the computer-readable storage medium 2114 include a solid-state memory, a magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and an optical disk. Some examples of optical disks include Compact Disk - Read Only Memory (CD-ROM), Compact Disk - Read / Write (CD- R / W), Digital Versatile Disc (DVD), and Blu-Ray Disc.

[0211] The processor 2104 is coupled to the program and data memory 2106 through a system bus 2116. The program and data memory 2106 include local memory employed during actual execution of the program code, bulk storage, and / or cache memories that provide temporary storage of at least some program code and / or data in order to reduce the number of times the code and / or data are retrieved from bulk storage (e.g., a hard disk drive, a solid state drive, or the like) during execution.

[0212] Input / output or I / O devices 2108 (including but not limited to keyboards, displays, touchscreens, microphones, pointing devices, etc.) may be coupled either directly or through intervening I / O controllers. Network adapter interfaces 2110 may also be integrated with the system to enable the computing system 2102 to become coupled to other computing systems or storage devices through intervening private or public networks. The network adapter interfaces 2110 may be implemented as modems, cable modems, Small Computer System Interface (SCSI) devices, Fibre Channel devices, Ethernet cards, wireless adapters, etc. Display device interface 2112 may be integrated with the system to interface to one or more display devices, such as screens for presentation of data generated by the processor 2104.

Claims

Attorney Docket No. 10880.024WO1 Claims What is claimed is:

1. A laser system, comprising: a reflector; a gain medium optically coupled to the reflector and operable to emit laser pulses; a plurality of laser diodes operable to pump the gain medium with laser diode pulses to stimulate laser pulse emission; a Q-switch device operable with the reflector to resonate laser light through the gain medium; and an output coupler optically coupled to the Q-switch device and operable to output the laser pulses based on a polarization of the laser light, wherein one or more of the plurality of laser diodes is further operable to control operating parameters of the laser system by inserting one or more diode ghost pulses between laser diode pulses that result in the emitted laser pulses.

2. The laser system of claim 1, wherein: the operating parameters of the laser system include laser divergence of the emitted laser pulses.

3. The laser system of claim 1, wherein: the operating parameters of the laser system include temperatures of one or more optical components within the laser system.

4. The laser system of claim 1, further comprising: a reverse wave suppression reflector configured outside of a primary optical path of the laser system.Attorney Docket No. 10880.024WO1 5. The laser system of claim 4, wherein: the reverse wave suppression reflector is operable to propagate the laser light through the primary optical path in a clockwise manner and to suppress any laser light propagating in a counterclockwise manner.

6. The laser system of claim 1, further comprising: a saturable absorber configured in a primary optical path of the laser system and operable to provide passive Q-switching to the laser system.

7. The laser system of claim 6, wherein: at least one of the plurality of laser diodes is operable to heat the saturable absorber to change the operating parameters of the laser system.

8. The laser system of claim 6, further comprising: a device operable to heat the saturable absorber to change the operating parameters of the laser system.

9. The laser system of claim 6, wherein: the saturable absorber is configured in a housing with a wave plate.

10. The laser system of claim 1, further comprising: a controller operable to control diode ghost pulse repetition rates to change the operating parameters of the laser system.

11. The laser system of claim 1, further comprising: a controller operable to control diode ghost pulse temporal sequences based on a temperature of the gain medium to change laser divergence.Attorney Docket No. 10880.024WO1 12. The laser system of claim 1, further comprising: a controller operable to detect an environmental condition of the laser system before laser pulse emission, and to direct at least one of the plurality of laser diodes to generate diode ghost pulses to change the operating parameters of the laser system based on the environmental condition of the laser system.

13. The laser system of claim 1, wherein: the Q-switch device is operable to average out aberrations in laser light via a plurality of round trips of the laser light through the laser system.

14. The laser system of claim 1, wherein: the primary optical path is configured to exhibit a critical instability near plane-parallel operating conditions based on a magnification of greater than 0.

85.

15. The laser system of claim 1, further comprising: a controller operable to monitor the operating parameters of the laser system to adaptively control the plurality of laser diodes.

16. The laser system of claim 1, further comprising: a controller operable to monitor the operating parameters of the laser system to predict future operating parameters of the laser system, and to control the plurality of laser diodes based on the predicted future operating parameters.

17. A method operable in a laser system, comprising: pumping a gain medium with laser diode pulses to stimulate the gain medium and resonate laser light through the gain medium between a reflector and a Q-switch device; emitting laser pulses from the gain medium through an output coupler optically coupled to the Q-switch device; and inserting one or more diode ghost pulses into the laser system between laser diode pulses that result in the emitted laser pulses to control operating parameters of the laser system.Attorney Docket No. 10880.024WO1 18. The method of claim 17, wherein: the operating parameters of the laser system include laser divergence of the emitted laser pulses.

19. The method of claim 17, wherein: the operating parameters of the laser system include temperatures of one or more optical components within the laser system.

20. The method of claim 17, further comprising: heating a saturable absorber with a laser diode to change the operating parameters of the laser system.

21. The method of claim 17, further comprising: a controller operable to control diode ghost pulse repetition rates to change the operating parameters of the laser system.

22. The method of claim 17, further comprising: a controller operable to control diode ghost pulse temporal sequences based on a temperature of the gain medium to change laser divergence.

23. The method of claim 17, further comprising: a controller operable to detect an environmental condition of the laser system before laser pulse emission, and to direct a laser diode to generate diode ghost pulses to change the operating parameters of the laser system based on the environmental condition of the laser system.

24. The method of claim 17, wherein: the Q-switch device is operable to average out aberrations in laser light via a plurality of round trips of the laser light.Attorney Docket No. 10880.024WO1 25. The method of claim 17, further comprising: monitoring the operating parameters of the laser system to adaptively control a plurality of laser diodes.

26. The method of claim 17, further comprising: monitor the operating parameters of the laser system to predict future operating parameters of the laser system, and to control a plurality of laser diodes based on the predicted future operating parameters.

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