Split handpiece with passive Q-switch laser assembly field

Abstract

A split handpiece and system for skin treatment includes a passively Q-switched laser assembly operatively connected to an excitation laser source to receive an excitation laser beam having a first wavelength, and a beam splitting assembly operable to split the solid beam emitted by the passively Q-switched laser assembly to form an array of microbeams across a segment of skin, wherein the passively Q-switched laser assembly produces a high-power sub-nanosecond pulsed laser beam having a second wavelength.

Description

Technical Field

[0001] This system relates to a passive Q-switch laser packaged within a handpiece, and more particularly to a laser system having a split handpiece with a passive Q-switch laser assembly and a beam splitting assembly.

Background Art

[0002] Typically, a system for non-invasive treatment of skin diseases includes a cabinet in which a laser is disposed and a beam delivery system (typically an optical fiber or an articulated arm) connected to a handpiece that transmits laser radiation from the laser to a segment of the skin to be treated. The functionality of such a system is limited by the capabilities of the selected laser. Treatment of skin defects typically requires multiple types of lasers, and multiple types of lasers are often installed within the cabinet. This increases the size, cost, and complexity of the system.

[0003] Treatment of some skin defects requires a large laser power (tens of MW, and even hundreds of MW) supplied in ultrashort pulses (most commonly in the picosecond range) to prevent damage to the skin. Such laser power is difficult to transmit via a fiber, and using an articulated arm significantly restricts the freedom of the caregiver.

[0004] A typical Q - switched micro - cavity laser is composed of a laser medium and a saturable absorber as a passive Q - switch arranged very close to each other. The cavity length is managed to be as short as possible. The Q - switched micro - cavity laser is a small solid - state laser with a linear short cavity. A typical cavity length is on the order of millimeters. When the cavity length is short, the cavity lifetime becomes extremely short, and the possibility of obtaining very short Q - switched pulses is obtained. It has been demonstrated that a Q - switched micro - cavity laser can generate output pulses in the sub - nanosecond region. In some special cases (i.e., monolithic cavities), the pulse duration can be made as short as that generated by a large mode - locked laser with a peak power of about 10 kW, which is the same as that generated by commercially available large Q - switched systems.

[0005] Over the decades, much effort has been devoted to the generation of high - energy picosecond lasers. Also, many techniques have been developed. These techniques generally include a multi - stage configuration, i.e., a low - energy picosecond seed laser, for example, nJ or μJ, is supplied to an amplification stage (including a regenerative amplifier or / and multipass amplification). Such a multi - stage configuration requires a complex optical configuration and sophisticated electronic synchronization, further increasing the complexity and cost of the system.

Brief Description of the Drawings

[0006] The patent or application file includes at least one drawing drawn in color. A copy of this patent or patent application with the color drawing is provided by the Patent and Trademark Office upon payment of the claims and the required fees.

[0007] To more fully understand the present disclosure and its features, reference is made to the following description together with the accompanying drawings. In the accompanying drawings, the same reference numerals indicate the same elements.

[0008]

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DETAILED DESCRIPTION OF THE INVENTION

[0009] To simplify and clarify the description, it will be understood that, where appropriate, reference numerals are repeated between different figures to indicate corresponding or similar elements. Further, many specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, as will be understood by those of ordinary skill in the art, the embodiments described herein may be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the relevant features described. Also, this description should not be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale, and the ratios of certain portions may be exaggerated to better illustrate details and features of the present disclosure.

[0010] A plurality of definitions applicable to the entire above disclosure are presented here. The term "coupled" is defined as being directly or indirectly connected through intervening components and is not necessarily limited to physical connections. The connection can be made such that the objects are permanently connected or releasably connected. The term "substantially" is defined as conforming essentially to a particular dimension, shape, or other term that changes substantially, and the component does not need to be exact. The terms "comprising", "including", and "having" are used interchangeably in the present disclosure. The terms "comprising", "including", and "having" mean including what is described, but are not necessarily limited thereto.

[0011] Disclosed herein are a system having a sub-nanosecond split handpiece with a passive Q-switch laser assembly, and a method of implementing the split handpiece. As shown in FIG. 1, the system 10 may include an excitation laser source 12, an excitation laser delivery unit 14, and a split handpiece 16.

[0012] In one example, the excitation laser source 12 may be located within the cabinet. The excitation laser source 12 can be any excitation laser and is operable to provide energy to activate a passive Q-switch laser within the handpiece to generate short pulses of high energy (>1 mJ) in the sub-nanosecond region. For example, when the excitation laser is used in combination with a split handpiece, it may be operable to generate picosecond laser pulses having a high peak power of about 100 MW or more. The excitation laser source can be a laser emission wavelength at which the laser rod has sufficient absorption. For example, in the case of a Nd:YAG laser, the excitation laser wavelength may be one of three wavelength bands, namely, 735 - 760 nm, 795 - 820 nm, or 865 - 885 nm. The excitation laser can be a solid-state laser or a diode laser. Non-limiting examples of the excitation laser include an alexandrite laser (755 nm), a Ti:sapphire laser, a diode laser, a dye laser, an optical parametric oscillator (OPO), and an optical parametric amplifier (OPA). Using Ti:sapphire, a laser beam in the wavelength range of 700 - 900 nm can be generated by direct emission pumped in the visible wavelength region. In one example, an alexandrite laser can provide an excitation power exceeding 1 kW for higher pulse energy generation. The high excitation power promotes energy storage, which is further promoted by the use of a saturable absorber with a low initial transmittance.

[0013] The pump laser delivery unit 14 may be operable to deliver a pump laser to a split handpiece to pump a passive Q-switch laser. In some examples, the pump laser delivery unit may be an articulated arm, which is an assembly of a number of mirrors and mechanical levers or arms connected between them by rotational joints. In one example, the articulated arm may have a plurality of arms (elbows) and a plurality of mirrors operable to direct a laser beam to a desired point on the split handpiece by rotating around at least one rotational joint connecting the plurality of arms. In one example, the plurality of mirrors may be operable to preserve the polarization of the incident laser beam, which may be useful for efficient pumping of anisotropic laser materials (i.e., Nd:YAP and Nd:YLF). In additional examples, the pump laser delivery unit may include an optical fiber and be delivered by the optical fiber. The optical fiber may be a single-mode fiber, a multi-mode fiber, or a hollow-core fiber.

[0014] As seen in FIG. 2A, the split handpiece 16 may include a passive Q-switch laser assembly 18 and a beam splitting assembly 20. The split handpiece is operable to generate high-energy (>10 mJ) sub-nanosecond laser pulses and subsequently deliver these pulses to a treatment site (i.e., skin) in a split pattern. The split handpiece receives the pump laser delivered by the pump laser delivery unit, pumps the passive Q-switch laser, and generates high-energy (>10 mJ) sub-nanosecond pulses. The generated sub-nanosecond laser is then split into a microdot array by the beam splitting assembly, and the microdot array is delivered to the skin for partial treatment.

[0015] The passive Q-switch laser assembly is sized to be accommodated and attached within the split handpiece body, thereby reducing the size and complexity of the overall system and improving power utilization efficiency. Next, the split handpiece can be used for various applications, particularly for the treatment of skin diseases. The split handpiece body may be of a suitable size and weight that easily fits in the user's hand and can be carried by hand. The split handpiece may be 35 cm or less in length. In at least one example, the handpiece body may be shaped such that it is easy to hold like a pencil. In other examples, the handpiece body may include a pistol grip that is easy for the handpiece body to hold like a pistol.

[0016] In some examples, as shown in FIG. 2B, the excitation laser source 12 and / or the excitation laser delivery unit may be sized to be accommodated within the split handpiece body 16. In at least one example, the excitation laser source 12 may be a diode laser that can be located within the split handpiece body and is operable to directly irradiate the passive Q-switch laser assembly.

[0017] FIG. 2C shows an exemplary 1064 nm handpiece, and FIG. 2D shows a 532 nm handpiece of an embodiment, each using an optical fiber excitation laser delivery unit. The split handpiece 16 of FIG. 2C includes an excitation lens 101, a seed cavity having a passive Q-switch laser assembly 18, a collimating lens 24, a homogenizer 134, an attenuator 138, and a 1D beam splitting assembly 20. The split handpiece 16 of FIG. 2D includes an excitation lens 101, a seed cavity having a passive Q-switch laser assembly 18, a collimating lens 24, a second harmonic generation assembly 300, a homogenizer 134, an attenuator 138, and a 1D beam splitting assembly 20.

[0018] The passive Q-switch laser assembly emits sub-nanosecond pulses with laser powers in the tens and hundreds of megawatts. Since the passive Q-switch laser assembly does not require switching electronics, the overall size and complexity of the system are reduced, and the power efficiency is improved. In addition, it does not require interference control of the cavity dimensions, simplifies the device manufacturing, and significantly relaxes the temperature control tolerances during use. As a result, a potentially less expensive, smaller, more robust, and more reliable Q-switch laser system with performance equivalent to that of a coupled cavity Q-switch laser is obtained. The compact short-cavity passive Q-switch laser assembly can be used in a wide range of applications, including high-precision ranging, robot vision, automated production, efficient nonlinear frequency interaction including harmonic generation (second harmonic, third harmonic, fourth harmonic, sum frequency generation, OPO, etc.), environmental monitoring, micromachining, spectroscopy, cosmetics and microsurgery, skin treatment, ionization spectroscopy, automotive engine ignition, and supercontinuum generation where high peak power is required.

[0019] The split handpiece can be applied to the patient's skin and adapted to slide over the skin. In some examples, the split handpiece can hover over the patient's skin and move at a generally equidistant distance from the skin surface. The beam splitting assembly is operable to generate an array of laser beams across segments of the skin and / or scan the laser beams emitted by the passive Q-switch laser assembly across segments of the skin. The beam splitting assembly can cover a skin area treated in one dimension (1D) or two dimensions (2D). For example, the beam splitting assembly may generate a split microdot line beam pattern. In some examples, the passive Q-switch laser handpiece may include a second or higher harmonic generator to generate additional laser wavelengths.

[0020] Passive Q-switch laser assembly Passive Q-switch microcavity lasers with a cavity length of about 10 mm or less have been widely studied for decades. However, most studies have reported the generation of pulse energies of less than a few millijoules and peak powers of less than 10 MW. In particular, some lasers were only able to generate nanosecond laser pulse durations. Recently, the generation of 12 mJ has been demonstrated from a Yb:YAG / Cr:YAG microchip laser. However, due to the longer pulse duration (1.8 ns), only a peak power of about 3.7 MW could be achieved. Furthermore, the laser had to be operated under cryogenic conditions (i.e., 77°K), which was a problem for practical applications.

[0021] Single-pass excited passive Q-switch lasers have several limitations. To ensure sufficient absorption of the excitation energy in the laser material, the laser medium must be long enough, but as the laser medium gets longer, the duration of the emitted pulse gets longer. Furthermore, excitation lasers that are not absorbed at some specific excitation wavelengths can cause unwanted bleaching of the saturable absorber and potentially cause failure of the Q-switching operation. To overcome these aforementioned problems, the present disclosure introduces a passive Q-switch laser assembly having double-pass excitation. Double-pass excitation also facilitates the use of a laser medium generated from a crystal that is difficult to dope (i.e., Nd:YAG) or a crystal with weak absorption of the laser medium at available excitation laser wavelengths. Double-pass excitation can be achieved by applying a high-reflection dielectric coating to either the output end or the input end passive Q-switch of the laser material for a cavity configuration in which two materials (i.e., the laser material and the saturable absorber) are separated by a small gap. In the case of a monolithic configuration, the high-reflection coating is sandwiched between the laser material and the saturable absorber, while the two materials are joined together. The double-pass excited short cavity laser supports efficient excitation laser absorption and a short medium length, resulting in shorter pulse durations and a compact laser layout.

[0022] The present disclosure describes a short cavity passive Q - switched laser assembly for generating sub - nanosecond laser pulses having a high peak power exceeding 100 MW. The operation of the laser is based on a passive Q - switch, and the passive components function as a Q - switcher for a compact and low - cost design.

[0023] A passive Q - switched laser assembly with double - pass excitation offers advantages over those with single - pass excitation by generating very short pulses due to the shorter laser material used. This is because the Q - switched pulse duration is approximately proportional to the cavity length. Also, for crystals with low doping concentration or low absorption at the excitation laser wavelength, sufficient excitation laser absorption can be obtained while shortening the double - pass crystal length, enabling a more compact laser design. Since a passive Q - switched laser assembly does not require the introduction of bulky active components, the cavity length can be reduced. In some examples, the passive Q - switched laser assembly may use a highly doped laser material and / or a saturable absorber, resulting in a shorter material length.

[0024] The passive Q - switched laser assembly may include two functional groups: an excitation lens and a laser cavity. The excitation lens is operable to direct an excitation laser into the laser crystal of the laser cavity having a specific spot size. The excitation spot is selected under a trade - off between the available excitation energy and a large spot size. A larger spot size results in higher energy, while higher excitation energy is required to enable Q - switching. The laser cavity enables passive Q - switching and generates sub - nanosecond laser pulses. The laser cavity can be a monolithic cavity or a cavity with external cavity mirrors.

[0025] Monolithic cavity In a monolithic cavity, a laser medium and a saturable absorber were sandwiched at the excitation wavelength by a high-reflectivity dielectric coating and joined by optical contact through intermolecular forces. The high-reflectivity dielectric coating supports the achievement of double-pass excitation and avoids unwanted bleaching of the passive Q-switch by the unabsorbed excitation laser.

[0026] A passive Q-switch laser assembly having a monolithic cavity 100 and an excitation lens 101 is shown in FIG. 3A. FIG. 3B shows that the monolithic cavity 100 can include a laser medium 104 and a high-reflectivity dielectric coating 108 for exciting the laser wavelength sandwiched between the laser medium 104 and the saturable absorber 112. FIGS. 3A and 3B also show an excitation laser beam 116 and an output beam 120. The excitation laser beam 116 may be, for example, a beam having a wavelength of about 755 nm for exciting a monolithic microchip laser including Nd:YAG as the laser medium and Cr 4+: YAG as the saturable absorber. The high-reflectivity dielectric coating 108 (highly reflective at the excitation laser wavelength of about 755 nm and highly transmissive at the Q-switch laser wavelength of 1064 nm) supports the achievement of double-pass excitation and avoids unwanted bleaching of the passive Q-switch 112 due to leakage of the unabsorbed excitation laser through it. Other excitation wavelengths can be used, including but not limited to diode lasers operating at 800 - 820 nm, or other types of solid-state light-emitting lasers (i.e., Ti:sapphire) operating at about 800 - 820 nm.

[0027] At the input end 124 of the monolithic cavity 100, the surface of the laser material 104 can be coated to be highly reflective at the laser wavelength (e.g., 1064 nm dielectric coating) and highly transmissive at the excitation wavelength. At the output end 128 of the monolithic cavity 100, the surface of the passive Q-switch 112 can be deposited with a dielectric coating that is partially reflective at the output beam wavelength of the monolithic cavity 100. The coating 108 takes into account the refractive indices of the laser medium and the saturable absorber so that the coating required for forming the monolithic material functions. These two ends (124 and 128) are arranged in parallel and coated with a dielectric coating to enable laser oscillation. The two ends may be flat surfaces or may be curved surfaces having an operable curvature to achieve better mode selectivity.

[0028] Diffusion bonding is generally used to bond a laser material and a passive Q-switch element (e.g., a saturable absorber) to form a passive Q-switch microchip laser. This method is typically achieved at a pressure and temperature that are about 50 to 70% of the absolute melting temperature when placed in a contact material. Such a manufacturing process requires high temperatures and makes it difficult to deposit any form of dielectric coating, particularly a high-reflection coating at the excitation laser wavelength, between the two elements (e.g., the laser medium and the passive Q-switcher). Therefore, only single-pass excitation can be applied.

[0029] In the present disclosure, the bonding between the laser medium 104 and the saturable absorber 112 can be implemented as shown by arrow 103 through optical contact by intermolecular forces such as van der Waals forces, hydrogen bonds, and dipole-dipole interactions as shown in FIG. 4. Since high temperatures and pressures are not required, the integrity of the reflective dielectric coating 108 is protected.

[0030] The two surfaces that are in contact, namely 105 of the laser medium 104 and 113 of the saturable absorber 112, are processed with optical quality to achieve stable optical contact. A high-reflection dielectric coating at the interface between the laser medium 104 and the saturable absorber 112 at the excitation wavelength supports the achievement of double-pass excitation and avoids unwanted bleaching of the passive Q-switch by the unabsorbed excitation laser. Generally, the surface quality can be better than 20-10 scratch-dig. The flatness and roughness can be at least λ / 4 and 10 Arms or more, respectively.

[0031] The laser medium 104 can be a Nd-doped crystal. The host material can be a YAG, YAP, YLF crystal or a ceramic. Non-limiting examples of the laser medium include crystals (i.e., Nd:YAG, Nd:YAP, Nd:YLF) or Nd:YAG ceramic. The saturable absorber 112 can be a chromium (Cr 4+ )-doped crystal (i.e., YAG) or ceramic YAG. The materials of the laser medium and the saturable absorber may be the same host material or different materials. In some examples, the laser medium and the saturable absorber may be separate ceramic crystals Nd:YAG and Cr:YAG or monolithic composite ceramic crystals Nd:YAG and Cr:YAG. This is completely different from existing microchip lasers joined by a diffusion method in which the material physical properties (i.e., melting point, thermal expansion coefficient, etc.) of the two components are similar.

[0032] High-energy / high-peak-power ultrashort-pulse microchip lasers facilitate efficient non-linear frequency interaction, including harmonic generation (second harmonic, third harmonic, fourth harmonic, sum frequency generation, OPO, etc.) and supercontinuum generation that requires high peak power. In contrast to existing low-energy microchip lasers, high-energy microchip lasers can provide higher energy / power at the frequency-converted wavelength, thus significantly improving measurement accuracy by improving the signal-to-noise ratio. Most importantly, the optical configuration is very compact and simple, supporting the installation of the microchip laser into a limited space, such as within a handpiece.

[0033] External-mirror cavity In an external-mirror cavity, the laser cavity is configured as a linear cavity with a cavity length shorter than 10 mm to achieve compactness and short-pulse generation. In some examples, the cavity length may be less than 10 mm, less than 8 mm, or less than 5 mm. The laser cavity is for generating a pulse laser beam below nanoseconds. The laser pulse below nanoseconds may be less than 1000 picoseconds. In various examples, the laser pulse below nanoseconds may be in the range of 150 picoseconds to less than 1000 picoseconds, about 200 picoseconds to about 400 picoseconds, about 300 picoseconds to about 500 picoseconds, about 400 picoseconds to about 600 picoseconds, or about 500 picoseconds to about 1000 picoseconds. The sub-nanosecond laser may have a wavelength of about 1 μm (i.e., 1064 nm for Nd:YAG, 1080 nm for Nd:YAP, 1047 / 1053 nm for Nd:YLF).

[0034] A passive Q-switch laser assembly 18 having at least one external-mirror laser cavity 200 and an excitation lens 101 is shown in FIGS. 5A-5F. The external-mirror laser cavity may include one or more external cavity mirrors. In at least one example, the laser cavity may include two external cavity mirrors.

[0035] In particular, FIG. 5A shows that the external mirror cavity 200 can include a pair of cavity mirrors forming a resonator (i.e., a high reflector (HR) 202 and an output coupler (OC) 204), a gain medium 206, and a saturable absorber 208 that functions as a passive Q-switch. Also shown in FIGS. 5A-5F are an excitation laser beam 116 and an output beam 120. The excitation laser beam 116 can be, for example, a beam having a wavelength of about 755 nm. Other excitation wavelengths can be used, including but not limited to diode lasers operating at 800-820 nm, or other solid-state light-emitting lasers (e.g., Ti:sapphire) operating at 800-820 nm.

[0036] In some other examples, one of the cavity mirrors (i.e., the high reflector 202 or the output coupler 204) can be replaced by depositing an appropriate optical coating on one of the end faces of the laser gain medium 206 or the saturable absorber 208 (see FIGS. 5B-5C and 5E-5F). Using only one external cavity mirror can help shorten the cavity length and can result in shorter pulse generation. In one example, a high-reflection coating 203 can be deposited on the input end of the laser gain medium 206 to function as a high reflector, and the output coupler 204 can be left as one of the external mirrors (FIG. 5B). In another example, only the external high reflector 202 can be included, while a partial-reflection coating 205 can be deposited on the output end of the saturable absorber to function as an output coupler (FIG. 5C).

[0037] In one example, as seen in FIGS. 5D - 5F, the laser gain medium 206 can be bonded to a saturable absorber 208 as one physical element for shortening the cavity length, thereby obtaining a short pulse duration. Unlike a typical monolithic cavity, both ends of this monolithic element are coated with an AR coating for the laser wavelength. Further, the coating on the input end of this monolithic crystal can be highly transmissive at the excitation laser wavelength. Similar to a typical monolithic cavity, the laser medium and the saturable absorber are sandwiched between coatings that are highly reflective at the excitation wavelength (i.e., the first wavelength) and highly transmissive at the laser wavelength (i.e., the second wavelength). In various examples, the high - reflection coating 203 is deposited on the input end of the laser gain medium 206 that functions as a high - reflector, while a separate mirror with a partial - reflection coating functions as the output coupler 204 (FIG. 5E). In other examples, the output end of the saturable absorber 208 may be coated with a partial - reflection coating that functions as the output coupler 205, while a separate HR mirror 202 may be present to optimize the alignment of the cavity (FIG. 5F). All of these configurations can support shorter pulse generation and can help reduce the cavity length that can simplify the design.

[0038] Instead of using a wavelength - tuning element within the cavity, wavelength selectivity may be implemented using a high - damage - threshold optical surface coating directly deposited on the end faces of cavity mirrors having specific spectral requirements. The high - reflector (HR) cavity mirror 202 may be coated to be highly transmissive at the excitation laser wavelength and highly reflective at the laser wavelength (R≥99%) (e.g., 1064 nm for Nd:YAG). The output - coupler (OC) cavity mirror may be coated with a coating that is partially reflective at the laser wavelength.

[0039] The laser gain medium 206 may include one or more crystals. In some examples, the laser gain medium may be a laser crystal or a ceramic material. Non-limiting examples of crystals are Nd:YAG (neodymium-doped yttrium aluminum garnet), Nd:YAP (neodymium-doped yttrium aluminum perovskite), or Nd:YLF (neodymium-doped yttrium lithium fluoride). In at least one example, the laser gain medium 206 may be a rare earth ion-doped ceramic material such as ceramic Nd:YAG. The front surface of the laser gain medium 206 can be coated with an anti-reflection coating. The back surface of the laser gain medium 206 can be coated with a high-reflection dielectric coating at the excitation laser wavelength to support the achievement of double-pass excitation and avoid unwanted bleaching of the passive Q-switch by the unabsorbed excitation laser. The double-pass excitation structure supports sufficient excitation laser absorption and a shorter medium length, resulting in a more compact laser layout and a shorter pulse duration.

[0040] The saturable absorber 208 functions as a passive Q-switch to implement Q-switching and can generate laser pulses shorter than nanoseconds near 1 μm. Non-limiting examples of saturable absorbers are Cr 4+ :YAG crystal, ceramic Cr 4 :YAG, GaAs, or a semiconductor saturable absorber.

[0041] Second harmonic generation assembly FIG. 6 is an example of a split handpiece 16 having a second harmonic generation assembly 300 between the passive Q-switch laser assembly 18 and the beam splitting assembly 20. The laser wavelength from the passive Q-switch cavity can be converted to other wavelengths by non-linear frequency generation. In some examples, the second harmonic generation assembly 300 may include a frequency doubling crystal 304, a dichroic mirror 306, and a beam dump 308. In one example, the frequency doubling crystal can generate a second harmonic wavelength within the visible wavelength range to enhance melanin absorption.

[0042] In some examples, the frequency doubling crystal 304 may be a second harmonic generation (SHG) crystal. Non-limiting examples of frequency doubling crystals include lithium niobate (LiNbO3), potassium titanyl phosphate (KTP = KTiOPO4), lithium triborate (LBO = LiB3O5), or any other SHG crystal. To produce a stable linearly polarized Q-switched laser, specially cut Nd:YAG (i.e.,

[0100] ), or / and Cr 4+ :YAG (i.e.,

[0110] cut) can be used.

[0043] The dichroic mirror may be operable to transmit the second harmonic laser and reject the remaining fundamental wavelength. For example, the frequency doubling crystal 304 receives the output beam 120 from the passive Q-switched laser assembly and converts it into two beams. One beam 320 maintains the original wavelength (frequency) of the output beam 120, and the other beam 312 has a frequency twice as high as that of the output beam 120. In at least one example, the output beam 120 has a wavelength of 1064 nm, and the beam with twice the frequency has a wavelength of 532 nm. The dichroic mirror 306 can be a beam splitter that diverts and directs the beams 320 and 312 in different directions. The beam that maintains the original wavelength 320 can be directed to the beam dump 308. In one example, a beam dump is used to block the rejected fundamental wavelength laser. Next, the output beam of the second harmonic generation assembly 312 can be passed through the beam splitting assembly 20.

[0044] Handpiece One potentially promising use of a passive Q-switch laser assembly that generates sub-nanosecond laser pulses can be in cosmetic and medical laser systems. A high-energy short-pulse passive Q-switch laser assembly can support performing significant aesthetic treatments, particularly partial skin rejuvenation, by packaging the passive Q-switch laser assembly into a handpiece. Clinically proven, laser pulses of mJ at hundreds of picoseconds per laser beam are sufficient to cause microdamage to tissue or skin via laser-induced optical breakdown (LIOB) or melanin-assisted optical breakdown. Subsequent collagen remodeling stimulated by such microdamage results in skin rejuvenation. A current passive Q-switch laser assembly can generate laser pulses of 40 mJ to 300 ps or more with a wavelength of 1064 nm. Thus, the output energy from the passive Q-switch laser assembly can be branched into multiple microbeams using a beam splitting assembly 20. For example, the beam from the passive Q-switch laser assembly can be branched into at least 2 microbeams, at least 5 microbeams, at least 10 microbeams, at least 15 microbeams, or at least 30 microbeams. Other numbers of microbeams are also contemplated. Each microbeam can have laser energy up to 4 mJ sufficient for effective skin treatment in the case of 10 microbeams. Each microbeam can be focused by a lens within the beam splitting assembly to generate a plurality of microdots.

[0045] Skin treatment typically requires irradiation of radiation to a two-dimensional area of the skin. Partial skin treatment can use a microbeam or split beam having a scanning mirror or other scanning means. There are many approaches for implementing a two-dimensional microbeam pattern. For example, the laser beam can be branched into a one-dimensional array of microbeams, and the one-dimensional array of microbeams can be manually slid on the skin. In another approach, a scanning system can be used to scan the array of microbeams in one or two directions / axes.

[0046] FIG. 7A shows an example of a 1D beam splitting assembly 20 having a 1D beam splitter 126 and a focusing lens 130. The beam splitting assembly 20 is designed to split an incident single solid beam 120 into an array of multiple microbeams 122 by a combination of the 1D beam splitter 126 and the focusing lens 130. In some examples, the 1D beam splitter may be a 1D diffractive optical beam splitter or a scanner.

[0047] The size of the microbeam at the focal plane may range from about 10 μm to about 300 μm in diameter. In various examples, the microbeam size may be up to 10 μm, up to 20 μm, up to 50 μm, up to 100 μm, up to 150 μm, up to 200 μm, up to 250 μm, or up to 300 μm in diameter. In some examples, the microbeam may have a diameter in the range of about 10 μm to about 50 μm, about 25 μm to about 75 μm, about 50 μm to about 100 μm, about 75 μm to about 125 μm, about 100 μm to about 150 μm, about 125 μm to about 175 μm, about 150 μm to about 200 μm, about 200 μm to about 250 μm, or about 250 μm to about 300 μm at the focal plane.

[0048] The branched beam can be a solid microdot or a donut shape (i.e., a dot surrounded by a ring). For example, the 1D beam splitting assembly can include an axicon diffractive optical element, a 1D beam splitter, and a focusing lens that form a ring or donut-shaped beam. FIG. 7B shows an output example of a 1D solid beam splitter and a scanning result of a microdot array. FIG. 7C shows an output example of a 1D donut beam splitter and a scanning result of a microdot array. The donut-shaped beam array helps to increase the surface coverage rate and reduce the number of passes for treatment.

[0049] In other examples, the sub-nanosecond laser generated from the passive Q-switch laser assembly can be directed to a lens array to form split microbeams by a pair of scanning mirrors. FIG. 7D shows an exemplary beam splitting assembly 20 having a pair of scanning mirrors, such as galvanometer-driven mirrors (galvo mirrors) 904 and 908, that project or scan the laser beam 120 onto the lens array 912. In some examples, the first scanning mirror 904 can provide in-plane rotation, the second scanning mirror 908 can provide out-of-plane rotation, and the lens array 912 branches the laser beam 120 into a plurality of split microbeams. The combination of the pair of scanning mirrors and the lens array optics can produce a microdot array with a large surface coverage. By moving the two scanning mirrors, the incident beam can be directed two-dimensionally across the surface of the lens array to increase the surface coverage. To avoid overlapping of the scanning spots or to leave untreated areas, the scanning can be appropriately programmed such that the spots projected onto the lens array after one scanning cycle are adjacent to each other. In at least one example, the passive Q-switch laser energy is high enough such that each laser beam from the sub-nanosecond laser covers a plurality of small lenses and can generate a plurality of microdots with sufficient energy per microdot for significant treatment. The pair of scanning mirrors can scan the laser beam to form a 2D pattern and cover a larger area of the small lenses, as shown in FIG. 7E. After the scanning system completes one cycle, a 2D microdot array can be generated within the skin with a larger surface coverage, as seen in FIG. 7F. The scanning of the incident sub-nanosecond laser beam can be in a continuous or random order.

[0050] In the case of 1D beam splitting, the scanning speed can affect the density or coverage of the microdot array across the treatment area. The lines of the plurality of generated microbeams can be extended to a two-dimensional microbeam array by manually sliding the handpiece along a direction perpendicular to the line of microdots guided by one or two rollers, or by scanning the line of microdots with a scanner. For example, as seen in FIG. 8A, a 2D split beam pattern 712 can be generated by manually moving the split handpiece in a direction perpendicular to the 1D split microdot line 704 as indicated by arrow 708. The coverage of the partially treated skin area can be varied by changing the number of split microdots 704 within the 1D line and / or the moving speed of the split handpiece. The moving speed of the split handpiece can determine the spacing between the plurality of microdot arrays. FIG. 8A is an example of a relatively sparsely split microdot 704 array in a 1D line moved at speed 708 (e.g., 7 microdots). FIG. 8B is an example of a split microdot 704 array of the same density within a 1D line moved at speed 808. For example, the moving speed 708 in FIG. 8A is faster than the same handpiece having the moving speed 808 in FIG. 8B. Thus, a denser 2D pattern 812 of split microdots 704 is generated. Thus, slower sliding can result in a higher coverage of the split beam, and faster sliding can result in a lower coverage of the split beam on the treatment area. In some examples, the number of split microdots within the 1D line can be adjusted by changing the beam splitter. For example, the beam splitter may be a snap-on disposable optical chip operable to connect to the handpiece. The snap-on chip allows for easy daily cleaning of the beam splitter optics and can provide the user with different chip designs including different attenuation levels and different microdot arrangements (increase or decrease in the number of microdots per column and different microdot densities).The user can select, for each column, based on the desired number of microdots, or the number of microdots can be the same and different chips with higher or lower density microdots can be selected.

[0051] Figures 9 and 10 show an example of a split handpiece having a 1D beam splitter within a beam splitting assembly 20 operable to manually move the handpiece. For skin treatment, a caregiver or user can manually slide a split handpiece having a 1D beam splitter over the treated skin area. The split handpiece may physically contact the skin or may be positioned away from the skin surface when the user slides the handpiece over the patient's skin. During the sliding motion, the passive Q-switch laser assembly can generate sub-nanosecond laser pulses that form a 1D split microdot line.

[0052] In some examples, the split handpiece may include one or more position rollers for manually moving the handpiece along a direction perpendicular to the 1D split microspot line to form a 2D microspot pattern. The rollers can be used to determine when to fire the excitation laser again. For example, when a 1D array moves across the skin, the rollers can track the distance the handpiece has moved and send a signal to the excitation laser source to fire again after the handpiece has moved a set distance. This set distance can range from about 400 μm to about 800 μm. For example, the set distance can be about 400 μm, about 500 μm, about 600 μm, about 700 μm, about 800 μm. The rollers can also be used as a safety feature so that the excitation laser source stops when the rollers stop. This can prevent tissue damage if the movement of the handpiece stops or pauses. Alternatively, the laser can be set to fire at a constant rate, and the rollers are used to measure the movement speed of the handpiece across the skin surface. If the speed is too fast or too slow, the user can receive feedback from the rollers. For example, the feedback may include light that starts when an inappropriate scanning speed is triggered, light of a different color, or a tactile vibration.

[0053] Figure 9A is an example of a system having a split handpiece with one or two rollers 118 for guiding the movement of the handpiece and synchronizing it with the laser pulses. The one or two rollers can be operable to manually slide the split handpiece over the target area. By manually sliding the split handpiece, a 2D split beam pattern guided by the one or two rollers can be generated. The partial coverage rate can be varied by changing the sliding speed. Slower movement results in a higher surface coverage rate.

[0054] System 10 may include an excitation laser source 12, an excitation laser delivery unit 14, a split handpiece 16, and a controller 22. As described above, the split handpiece 16 may include a passive Q-switch laser assembly 18 and a beam splitting assembly 20 including a 1D beam splitter 126 and a focusing lens 130.

[0055] The split handpiece 16 may further include a high-speed photodetector 132 or some other means for sensing sub-nanosecond laser pulses. In one example, the photodetector can communicate with a controller to stop the excitation laser and avoid double or multiple pulses. In one example, the laser pulses can be synchronized with the roller rotation. In some examples, a homogenizer 134 (either diffraction-based or refraction-based) can be added to the split handpiece in front of the beam splitting array to correct for changes in beam characteristics at different repetition rates. Also, the split handpiece can include a vibrator 136, buzzer, mechanical oscillator, or acoustic system to warn the operator in case of a malfunction of the laser, such as a laser misfire. Further, the vibrator can be used to provide tactile feedback to assist the user in controlling the scanning speed by providing feedback to the user when the sliding speed is too slow or too fast. For example, the handpiece may shake or oscillate if it is moving too fast. In an additional example, the split handpiece 16 may further include an attenuator 138 to achieve the appropriate energy for treating different skin types or LIOB depths. The attenuator can be a neutral density filter or a polarization-based element (such as a polarizer cube). The photodetector 132, vibrator 136, roller 118, and / or excitation source laser 12 may be operably connected to a controller 22. The controller 22 is functional electronics that receives electrical signals from the roller 118, vibrator 136, and photosensor 132, processes them, and is used to supply a feedback signal to the excitation laser source to control the on and off of the excitation laser. The components of the split handpiece may be small enough to be packed within the handpiece 16. Such a handpiece 16 is operable to generate picosecond laser beams and enables partial treatment for skin rejuvenation.

[0056] An optional second or higher harmonic generator 300 can be located within the handpiece body 16. FIG. 9B shows an example of a handpiece having a second harmonic generator 300. The passive Q-switch laser assembly 18 can emit a beam having a wavelength of 1064 nm. If an additional laser light wavelength is required, the second harmonic generator 300 may be introduced into the laser beam path to generate the additional laser light wavelength. Generally, other wavelength frequency doubling devices can be arranged on a turret and used as needed. The temperature of the second harmonic crystal 304 can be controlled by the controller 22 to achieve stable and optimized frequency conversion.

[0057] FIG. 10 is an exemplary system having a split handpiece with a scanning mirror. In some examples, the scanning mirror can be synchronized with the laser pulse. The system 10 can include an excitation laser source 12, an excitation laser delivery unit 14, a split handpiece 16, and a controller 22. As described above, the split handpiece 16 can include a passive Q-switch laser assembly 18 and a beam splitting assembly 20 including a 1D beam splitter 126 and a focusing lens 130.

[0058] The beam splitting assembly can further include a fixed mirror 144 and a rotating mirror 142 that scans the line of the microbeam 122 to form a 2D microspot pattern. The partial coverage rate can be changed by varying the scanning speed of the rotating mirror 142. In one example, the rotating mirror may be a galvanometer mirror operable for out-of-plane rotation.

[0059] The split handpiece 16 may further include a fast photodetector 132, or some other means of sensing sub-nanosecond laser pulses that block the excitation laser and avoid double or multiple pulses. In one example, the laser pulses can be synchronized with the rotation of a rotating mirror. In some examples, a homogenizer 134 (either diffraction-based or refraction-based) can be added to the split handpiece in front of the beam splitting assembly to correct for changes in beam characteristics at different repetition rates. The split handpiece may also include a vibrator 136, a buzzer, a mechanical oscillator, or an acoustic system to warn the operator in the event of a malfunction of the laser, such as a laser misfire. In an additional example, the split handpiece 16 may further include an attenuator 138 to achieve the appropriate energy for treating different skin types or LIOB depths. The attenuator can be a neutral density filter or a polarization-based element (such as a polarizer cube). The photodetector 132, the vibrator 136, the roller 118, and / or the excitation source laser 12 may be operably connected to the controller 22 as described above. The components of the split handpiece may be small enough to be packed within the handpiece 16. Such a handpiece 16 is operable to generate picosecond laser beams and enables partial treatment for skin rejuvenation.

[0060] In a further example shown in FIG. 11, a handpiece for partial skin treatment is shown, and the passive Q-switch laser assembly includes a monolithic cavity 610. Generation of the split beam pattern is produced by a combination of a pair of galvo mirrors 904 and 908 that project or scan the laser beam 120 onto a lens array 912. The lens array 912 branches the laser beam 120 into a plurality of microbeams 916, which can be the split microbeams. A mirror 920 can be used to separate additional wavelengths generated by the second or higher harmonic generator 304. The coating of the mirror 920 is formed according to the desired wavelength separation. The unconverted infrared light 120 can be directed to and absorbed by the laser beam dump 924, while the harmonics can be delivered to the treated skin segment including a combination of skin diseases. The laser beam dump 924 can be operable to effectively dissipate the unconverted infrared energy without being damaged or raising the temperature of other components of the handpiece 900. Passive and active cooling mechanisms can be used as needed to remove heat from the laser beam dump 924.

[0061] The following example provides some operating parameters of a typical handpiece used for skin disease treatment. The energy for the output laser 120 of the passive Q-switch laser assembly can be 40 mJ or more. The energy of each microbeam 122 can be up to 4 mJ at 1064 nm and up to 2 mJ at 532 nm.

[0062] Such laser energy is high enough that each laser beam from the passive Q-switch laser assembly covers at least nine small lenses to produce nine microdots. The pair of galvo mirrors 904 and 908 scan the laser beam nine times to form a 2D pattern, covering at least 81 small lenses. Assuming the microchip laser operates at a frequency of 20 Hz, each scan takes 0.45 seconds (9 / 20), or the treatment can be operated up to 2.2 Hz.

[0063] Furthermore, the present specification provides a method of skin treatment. The method may include delivering a pulsed laser beam of less than nanoseconds using a laser system having a split handpiece to a patient in need thereof.

[0064] Referring to FIG. 12, a flowchart according to an exemplary embodiment is shown. Method 1000 is provided as an example since there are various ways to implement the method. Method 1000 described below can be implemented, for example, using the configurations shown in FIGS. 1-11, and various elements of these figures are referenced when explaining examples of method 1000. Each block shown in FIG. 12 represents one or more processes, methods, or subroutines executed in exemplary method 1000. Further, the order of the illustrated blocks is merely exemplary, and the order of the blocks can be changed in accordance with the present disclosure. Without departing from the present disclosure, additional blocks may be added or fewer blocks may be utilized.

[0065] Exemplary method 1000 is a method for skin treatment in a patient in need thereof. Exemplary method 1000 can begin at block 1002. At block 1002, an excitation laser source generates an excitation laser beam at a first wavelength. For example, in the case of a Nd:YAG laser, the excitation laser wavelength may be one of three wavelength bands, namely, 735-760 nm, 795-820 nm, or 865-885 nm. The excitation laser can be a solid-state laser or a diode laser. Non-limiting examples of excitation lasers include an Alexandrite laser (755 nm), a Ti:Sapphire laser, a diode laser, a dye laser, an optical parametric oscillator (OPO), and an optical parametric amplifier (OPA). Using Ti:Sapphire, a laser beam in the wavelength range of 700-900 nm can be generated by direct emission pumped in the visible wavelength region.

[0066] In a non-limiting example, an excitation laser beam with a wavelength of 755 nm can be generated from an alexandrite laser. In another example, an excitation laser beam with a wavelength of 1.053 μm or 1.047 μm can be generated from a passively Q-switched Nd:YLF laser.

[0067] In block 1004, the excitation laser beam is delivered to a passively Q-switched laser assembly within the split handpiece. In other examples, the excitation laser source may be located within the body of the split handpiece, and the excitation laser beam can directly irradiate the passively Q-switched laser assembly.

[0068] In block 1006, the passively Q-switched laser assembly within the split handpiece generates a high-power sub-nanosecond pulsed laser beam from the excitation laser beam. In one example, the generated sub-nanosecond pulsed laser beam has a second wavelength. The second wavelength can be a visible wavelength at which melanin has substantial absorption. Some non-limiting examples include 532 nm, 524 nm, or 528 nm. The sub-nanosecond pulsed laser beam can optionally be delivered to the split handpiece via a laser delivery unit.

[0069] In block 1008, the sub-nanosecond pulsed laser beam having the second wavelength is split by a beam splitting assembly to form a 1D array of microbeams.

[0070] In block 1010, the split handpiece moves across the skin to generate a 2D split beam pattern on the patient's skin. The delivered laser beam can be applied to a target area of the patient's skin. The target area can be any area of the patient's skin including, but not limited to, the face, arm, leg, back, chest, hand, or foot.

[0071] Those skilled in the art will understand that the present disclosure is not limited to what has been particularly shown and described above. Rather, the scope of the passive Q-switch laser and the handpiece includes both the various combinations and sub-combinations of the features described above, as well as those modifications and variations thereof that will occur to those skilled in the art upon reading the foregoing description and that are not found in the prior art.

[0072] The above-described disclosure is merely an example. Although many features and advantages of the technology are described in the foregoing description together with details of the structure and function of the present disclosure, the present disclosure is merely illustrative and can be modified in details, particularly in matters of the shape, size, and arrangement of parts within the principles of the present disclosure, up to the scope indicated by the broad general meaning of the terms used in the appended claims. Accordingly, it will be understood that the above-described embodiments are subject to change within the scope of the appended claims.

[0073] To facilitate understanding of the present disclosure, numerous examples are provided herein. A specific set of statements is as follows.

[0074] Statement 1: A split handpiece for skin treatment, comprising a handpiece body, the handpiece body including a passive Q-switch laser assembly within the handpiece body that is operably connected to an excitation laser source to receive an excitation laser beam having a first wavelength, the passive Q-switch laser assembly including one or more excitation lenses and a laser cavity including one or more external mirrors, a beam splitting assembly operable to split the solid beam emitted by the passive Q-switch laser assembly to form an array of microbeams across segments of the skin, the passive Q-switch laser assembly generating a high-power sub-nanosecond pulsed laser beam having a second wavelength, the split handpiece.

[0075] Statement 2: The split handpiece according to Statement 1, wherein the handpiece body is operable to slide across the skin of a patient.

[0076] Statement 3: The excitation laser beam of the first wavelength is delivered by the articulated arm including an optical fiber or a plurality of arms and mirrors, to the split handpiece described in Statement 1.

[0077] Statement 4: The laser cavity includes a high reflector cavity mirror, an output coupler cavity mirror, a gain medium, and a saturable absorber, in the split handpiece described in Statement 1.

[0078] Statement 5: The laser cavity includes a high reflector cavity mirror, an output coupler cavity mirror, a gain medium sandwiched by a coating that is highly reflective at the first wavelength and an antireflective coating at the second wavelength and joined to a saturable absorber, in the split handpiece described in Statement 1.

[0079] Statement 6: The input end of the joined gain medium is coated with an antireflective coating at both the first wavelength and the second wavelength, and the output end of the joined saturable absorber has an antireflective coating at the second wavelength, in the split handpiece described in Statement 5.

[0080] Statement 7: The high reflector cavity mirror includes a coating that is highly transmissive at the first wavelength and highly reflective at the second wavelength, in the split handpiece described in Statement 4 or 5.

[0081] Statement 8: The output coupler cavity mirror includes a coating that is partially reflective at the second wavelength, in the split handpiece described in Statement 4 or 5.

[0082] Statement 9: The laser cavity includes a high reflector cavity mirror, a gain medium, and a saturable absorber, and the output end of the saturable absorber includes a coating that is partially reflective at the second wavelength so as to function as an output coupler, in the split handpiece described in Statement 1.

[0083] Statement 10: The laser cavity includes a gain medium with an input end coated with a coating that is highly transmissive at a first wavelength and highly reflective at a second wavelength so as to function as a high reflector, a saturable absorber, and an output coupler, and is the split handpiece according to claim 1.

[0084] Statement 11: The gain medium includes a laser crystal or a ceramic material, and is the split handpiece according to any one of statements 4 to 10.

[0085] Statement 12: The gain medium includes Nd:YAG (neodymium-doped yttrium aluminum garnet), Nd:YAP (neodymium-doped yttrium aluminum perovskite), or Nd:YLF (neodymium-doped yttrium lithium fluoride), and is the split handpiece according to any one of statements 4 to 10.

[0086] Statement 13: The gain medium has an antireflection coating on the front surface and includes a high-reflection dielectric coating of a first wavelength on the back surface, and is the split handpiece according to statement 4.

[0087] Statement 14: The saturable absorber includes a Cr4+:YAG crystal or a ceramic Cr4:YAG, and is the split handpiece according to any one of statements 4 to 10.

[0088] Statement 15: The laser cavity includes a high reflector cavity mirror and a gain medium joined to the saturable absorber, and is the split handpiece according to statement 1.

[0089] Statement 16: The high reflector cavity mirror includes a coating that is highly transmissive at a first wavelength and highly reflective at a second wavelength, and is the split handpiece according to statement 15.

[0090] Statement 17: The gain medium is bonded to the saturable absorber and is sandwiched between a coating that is highly reflective at a first wavelength and an antireflective coating at a second wavelength, the split handpiece described in Statement 15.

[0091] Statement 18: The input end of the bonded gain medium is coated with an antireflective coating at both the first and second wavelengths, and the output end of the bonded saturable absorber has a partially reflective coating at the second wavelength so as to function as an output coupler, the split handpiece described in Statement 15.

[0092] Statement 19: The laser cavity includes an output coupler cavity mirror and a gain medium bonded to the saturable absorber, the split handpiece described in Statement 1.

[0093] Statement 20: The output coupler cavity mirror includes a partially reflective coating at the second wavelength, the split handpiece described in Statement 19.

[0094] Statement 21: The gain medium is bonded to the saturable absorber and is sandwiched between a coating that is highly reflective at a first wavelength and an antireflective coating at a second wavelength, the split handpiece described in Statement 19.

[0095] Statement 22: The input end of the bonded gain medium is coated with a highly reflective coating at the second wavelength and a highly transmissive coating at the first wavelength so as to function as a high reflector, and the output end of the bonded saturable absorber has an antireflective coating at the second wavelength, the split handpiece according to Claim 19.

[0096] Statement 23: The sub-nanosecond laser pulse is less than 1000 picoseconds, the split handpiece described in Statement 1.

[0097] Statement 24: The split handpiece according to statement 1, further comprising a scanning system including a pair of scanning mirrors for generating a two-dimensional microbeam pattern.

[0098] Statement 25: The split handpiece according to statement 24, wherein the scanning beam is incident on a lens array to form a microbeam array.

[0099] Statement 26: The split handpiece according to statement 1, wherein the beam splitting assembly includes a 1D beam splitter and a focusing lens.

[0100] Statement 27: The split handpiece according to claim 26, wherein the beam splitting assembly further includes an axicon diffractive optical element for generating a donut beam pattern.

[0101] Statement 28: The split handpiece according to statement 26, wherein the 1D beam splitter is operable to generate a 1D split microdot line.

[0102] Statement 29: The split handpiece according to statement 28, further comprising one or more rollers operable to enable manual movement of the handpiece along a direction perpendicular to the 1D split microdot line to form a 2D microspot pattern.

[0103] Statement 30: The split handpiece according to statement 28, wherein the beam splitting assembly further includes a fixed mirror and a rotating mirror operable to scan the 1D split microdot line to form a 2D microspot pattern.

[0104] Statement 31: The split handpiece according to statement 26, wherein the beam splitting assembly is operable to snap onto the split handpiece.

[0105] Statement 32: The beam splitting assembly is disposable, the split handpiece according to claim 31.

[0106] Statement 33: The handpiece body further includes a second harmonic generator for generating an additional laser light wavelength, the split handpiece according to claim 1.

[0107] Statement 34: The handpiece body further includes a high-speed photodetector operable to sense a sub-nanosecond pulsed laser beam and stop the excitation laser to avoid double or multiple pulses, the split handpiece according to claim 1.

[0108] Statement 35: The handpiece body further includes a homogenizer in front of the beam splitting assembly to mitigate changes in beam characteristics at different repetition rates, the split handpiece according to statement 1.

[0109] Statement 36: The handpiece body further includes a vibrator operable to vibrate to provide a warning or feedback to the user if there is any malfunction in the laser or if the sliding speed is too slow or too fast, the split handpiece according to statement 1.

[0110] Statement 37: The handpiece body further includes an attenuator operable to achieve appropriate energy for treating different skin types or LIOB depths, the split handpiece according to statement 1.

[0111] Statement 38: The handpiece body further includes one or two rollers for guiding the movement of the split handpiece and synchronizing it with the laser pulses, the split handpiece according to claim 1.

[0112] Statement 39: The split handpiece according to statement 1, further including a controller.

[0113] Statement 40: A laser system comprising an excitation laser source operable to provide an excitation laser beam and a split handpiece as described in any one of Statements 1 to 39.

[0114] Statement 41: The excitation laser source is within the split handpiece, the laser system as described in Statement 40.

[0115] Statement 42: The excitation laser source is a diode laser or an alexandrite laser, the laser system as described in Statement 40.

[0116] Statement 43: A method of skin treatment, the method comprising generating an excitation laser beam having a first wavelength via a pump beam source, delivering the excitation laser beam to a passive Q-switch laser assembly within a split handpiece comprising one or more excitation lenses and one or more external mirrors, generating a high-power sub-nanosecond pulsed laser beam having a second wavelength via the passive Q-switch laser assembly, splitting the high-power sub-nanosecond pulsed laser beam into a 1D array of microbeams via a beam splitting assembly, and moving the split handpiece across the skin of a patient to generate a 2D split beam pattern on the skin of the patient in need thereof.

Claims

1. A split handpiece for skin treatment, comprising: a handpiece body, wherein the handpiece body is operably connected to an excitation laser source to receive an excitation laser beam having a first wavelength, and the passive Q-switch laser assembly in the handpiece body, the passive Q-switch laser assembly comprising one or more excitation lenses and a laser cavity comprising one or more external mirrors; a beam splitting assembly operable to split the solid beam emitted by the passive Q-switch laser assembly to form an array of microbeams across segments of the skin; the beam splitting assembly comprising a 1D beam splitter, a focusing lens, and one or more rollers operable to manually move the handpiece along a direction perpendicular to the 1D split microdot line to form a 2D microspot pattern; the passive Q-switch laser assembly generating a high-power sub-nanosecond pulsed laser beam having a second wavelength, the split handpiece.

2. The split handpiece according to claim 1, wherein the laser cavity comprises a high reflector cavity mirror, an output coupler cavity mirror, a gain medium, and a saturable absorber.

3. The split handpiece according to claim 1, wherein the laser cavity comprises a high reflector cavity mirror, an output coupler cavity mirror, and a gain medium joined to the saturable absorber and sandwiched between a coating highly reflective at the first wavelength and an antireflective coating at the second wavelength.

4. The split handpiece according to claim 3, wherein the high reflector cavity mirror comprises a coating that is highly transmissive at the first wavelength and highly reflective at the second wavelength.

5. The split handpiece according to claim 3, wherein the output coupler cavity mirror comprises a coating that is partially reflective at the second wavelength.

6. The split handpiece according to claim 3, wherein the gain medium comprises Nd:YAG (neodymium-doped yttrium aluminum garnet), Nd:YAP (neodymium-doped yttrium aluminum perovskite), or Nd:YLF (neodymium-doped yttrium lithium fluoride).

7.

8. The saturable absorber is Cr ４＋ :YAG crystal or ceramic Cr ４ :YAG, the divided handpiece according to claim 3. ​ The laser cavity includes a high reflector cavity mirror, a gain medium, and a saturable absorber, and an output end of the saturable absorber includes a coating that is partially reflective at the second wavelength so as to function as an output coupler, for the split handpiece according to claim 1.

9. The laser cavity includes a gain medium having an input end coated with a coating that is highly transmissive at the first wavelength and a coating that is highly reflective at the second wavelength so as to function as a high reflector, a saturable absorber, and an output coupler, for the split handpiece according to claim 1.

10. The laser cavity includes a high reflector cavity mirror, a gain medium joined to the saturable absorber and sandwiched between a coating that is highly reflective at the first wavelength and an antireflective coating at the second wavelength, for the split handpiece according to claim 1.

11. The high reflector cavity mirror includes a coating that is highly transmissive at the first wavelength and highly reflective at the second wavelength, for the split handpiece according to claim 10.

12. An input end of the joined gain medium is coated with an antireflective coating at both the first wavelength and the second wavelength, and an output end of the joined saturable absorber has a coating that is partially reflective at the second wavelength so as to function as an output coupler, for the split handpiece according to claim 10.

13. The laser cavity includes an output coupler cavity mirror, a gain medium joined to the saturable absorber and sandwiched between a coating that is highly reflective at the first wavelength and an antireflective coating at the second wavelength, for the split handpiece according to claim 1.

14. The output coupler cavity mirror includes a coating that is partially reflective at the second wavelength, for the split handpiece according to claim 13.

15. An input end of the joined gain medium is coated with a coating that is highly reflective at the second wavelength and highly transmissive at the first wavelength so as to function as a high reflector, and an output end of the joined saturable absorber has an antireflective coating at the second wavelength, for the split handpiece according to claim 13.

16. The beam splitting assembly further includes a fixed mirror and a rotating mirror operable to scan the 1D split microdot line to form the 2D microspot pattern, the split handpiece according to claim 1.

17. The beam splitting assembly further includes an axicon diffractive optical element for generating a doughnut beam pattern, the split handpiece according to claim 1.

18. The handpiece body further includes a second harmonic generator for generating an additional laser light wavelength, the split handpiece according to claim 1.

19. A split handpiece for skin treatment, including a handpiece body, wherein the handpiece body is a passive Q-switch laser assembly within the handpiece body operably connected to an excitation laser source to receive an excitation laser beam having a first wavelength, the passive Q-switch laser assembly including one or more excitation lenses and a laser cavity including one or more external mirrors, and generating a high-power sub-nanosecond pulse laser beam having a second wavelength; a beam splitting assembly operable to split the solid beam emitted by the passive Q-switch laser assembly and form an array of microbeams across segments of the skin; wherein the handpiece body is a high-speed photodetector operable to sense the sub-nanosecond pulse laser beam and stop the excitation laser source to avoid double or multiple pulses; a homogenizer in front of the beam splitting assembly for mitigating beam characteristic changes at different repetition rates; a vibrator operable to vibrate and provide a warning or feedback to the user when there is any malfunction in the laser or when the sliding speed is too slow or too fast; an attenuator operable to achieve appropriate energy for treating different skin types or LIOB depths; and the split handpiece further includes one or two rollers for guiding the movement of the split handpiece and synchronizing it with the laser pulses.

20. The one or more rollers are further operable to synchronize with the laser pulses, the split handpiece according to claim 1.

21. The handpiece body further includes a homogenizer in front of the beam splitting assembly, the split handpiece according to claim 1.

Images