A two-dimensional array of pulsed self-synchronized flake laser structures

Abstract

The application discloses a two-dimensional array pulse self-synchronization wafer laser structure, which comprises an inner resonant cavity composed of a first reflecting layer, a saturable absorber, a wafer array gain medium and a second reflecting layer, and an outer resonant cavity composed of a phase grating structure layer and a third reflecting layer, and the inner resonant cavity and the outer resonant cavity form a composite resonant cavity; a pump light source emits pump light which is injected into the composite resonant cavity through a pump module, passes through the wafer array gain medium multiple times, and generates array oscillation laser in the inner resonant cavity; simultaneously, the saturable absorber absorbs and modulates the array oscillation laser, starts and maintains the array pulse operation; the array laser pulse enters the outer resonant cavity through the second reflecting layer, the phase grating structure layer causes the array pulse laser to be coupled, the array pulse laser returns to the inner resonant cavity through the third reflecting layer to be mutually injected, modulated and locked, the array pulse laser is synchronously operated in the composite resonant cavity, the collective mode laser pulse is formed, and the self-synchronized high-energy coherent array pulse output is realized.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and specifically to a two-dimensional array pulse self-synchronizing thin-film laser structure. Background Technology

[0002] Thin-plate lasers have a sheet-like gain medium structure, with heat dissipation and laser transmission occurring along the thickness of the gain medium. This results in a short heat dissipation path and a large aperture, allowing them to withstand very high pump power densities without significant temperature rise within the gain medium. The heat flow generated by the gain medium in the thin-plate structure is along the axial direction of laser oscillation, thus reducing heat penetration and enabling rapid removal of heat deposits on the gain medium. This ensures the stability of the output power and achieves high-power, high-beam-quality, and high-efficiency laser output, making it one of the current research hotspots in laser technology.

[0003] Passive Q-switching and passive mode-locking are the most commonly used techniques for obtaining short-pulse lasers in thin-film solid-state lasers. A saturable absorber is an optical device with a definite loss; when the incident light intensity exceeds the saturable absorber's threshold, the optical loss decreases and the transmittance increases. When a saturable absorber is added into the cavity, after multiple oscillations within the cavity, a passive Q-switching / mode-locking mechanism is introduced, generating a series of optical pulses with nanosecond, picosecond, or femtosecond widths. This offers advantages such as self-starting operation, reliable operation, and simple structure. However, saturable absorbers have a low damage threshold and are easily damaged under high-energy laser pulses. Furthermore, as laser power increases, thermal lensing and thermal stress effects in the thin film become more significant, limiting the pulse energy and beam quality of the thin-film laser output and reducing its lifespan and long-term stability. Therefore, achieving stable output of high-energy, high-beam-quality laser pulses has become a pressing problem for thin-film lasers. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a two-dimensional array pulse self-synchronizing thin-film laser structure. By employing array light-emitting units, the laser energy is distributed in a dispersed manner. An external resonant cavity enables the array laser pulses to oscillate in a self-synchronizing manner, forming a combined mode laser pulse. This solves the problems of thermal lensing, thermal stress, and damage to intracavity devices in lasers, which limit the output pulse energy of the laser and lead to a decrease in output beam quality. Ultimately, this invention achieves high-energy self-synchronizing coherent array pulse laser output.

[0005] This invention discloses a two-dimensional array pulsed self-synchronizing thin-film laser structure, comprising: a heat sink, a pump source, a pump module, an inner resonant cavity, and an outer resonant cavity; wherein,

[0006] The inner resonant cavity includes a first reflective layer, a saturable absorber, a thin-film array gain medium, and a second reflective layer sequentially disposed on the heat sink. The outer resonant cavity includes a phase grating structure layer and a third reflective layer sequentially disposed on the second reflective layer. The inner and outer resonant cavities constitute a composite resonant cavity.

[0007] The pump light emitted by the pump source is injected into the composite resonant cavity through the pump module. After passing through the thin-film array gain medium multiple times, array oscillating laser is generated in the inner resonant cavity. Simultaneously, the saturable absorber absorbs and modulates the array oscillating laser, initiating and maintaining the operation of the array pulse. The array laser pulse enters the outer resonant cavity through the second reflective layer. The phase grating structure layer couples the array pulse laser, and it returns to the inner resonant cavity through the third reflective layer for mutual injection modulation and locking, so that the array pulse laser operates synchronously in the composite resonant cavity, forming a combined mode laser pulse.

[0008] As a further improvement of the present invention, the pump light source is a semiconductor laser or a flash lamp, and the pumping method of the pump light source includes one or more of front-end pumping, rear-end pumping, external cavity pumping and lateral pumping.

[0009] As a further improvement of the present invention, the heat sink includes, but is not limited to, one of copper, diamond, and copper-tungsten alloy.

[0010] As a further improvement of the present invention, the pump light generated by the pump light source enters the composite resonant cavity in a multi-channel pumping manner through the pump module.

[0011] As a further improvement of the present invention, the thin-film array gain medium is a periodic structure formed by a light-transmitting material, which includes, but is not limited to, one of glass, crystal, sapphire and ceramic, and the light-transmitting material is doped with a rare earth ion or doped with different kinds of rare earth ions in a certain proportion as gain ions.

[0012] As a further improvement of the present invention, the thin-film array gain medium is composed of a photonic crystal array. Periodic micropores are prepared on a light-transmitting material doped with rare earth ions to create an effective refractive index difference between the central region and the periodic micropore structure region, forming a photonic crystal structure, i.e., a waveguide is formed by internal total internal reflection. Each photonic crystal constitutes a resonant cavity, and the number of photonic crystals is greater than 2, arranged in a two-dimensional array. The generated array oscillating laser passes through the thin-film array gain medium multiple times through the photonic crystal structure.

[0013] As a further improvement of the present invention, the thin-film array gain medium is composed of a close-packed fiber array. Active glass fibers are obtained by drawing rare-earth ion-doped glass preforms and glass outer tubes. The active glass fibers are arranged in a two-dimensional array with more than two fibers to obtain an active close-packed fiber array. Each active fiber constitutes a resonant cavity. The generated array oscillating laser passes through the thin-film array gain medium multiple times through the active fiber.

[0014] As a further improvement of the present invention, the absorption wavelength of the saturable absorber corresponds to the emission wavelength of gain ions in the gain medium of the thin-film array, thereby initiating and maintaining pulse operation in the inner resonant cavity and the composite resonant cavity.

[0015] As a further improvement of the present invention, the phase grating structure layer is formed using the same or different light-transmitting material as the gain medium of the thin-film array, and the arrangement of the grating structure corresponds to the gain medium of the thin-film array.

[0016] As a further improvement of the present invention, the first reflective layer has high reflectivity for oscillating laser and is the front end face of the inner resonant cavity and the composite resonant cavity;

[0017] The second reflective layer partially reflects and partially transmits the oscillating laser, serving as the rear end face of the inner resonant cavity. The reflectivity it provides satisfies the requirement for the oscillating laser to enter the outer resonant cavity.

[0018] The third reflective layer partially reflects and partially transmits the oscillating laser, serving as the rear end face of the external resonant cavity and the composite resonant cavity, and its reflectivity satisfies the requirements for oscillating laser output.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] This invention enables the pump light to pass through the thin-film array gain medium multiple times via a pump module, which facilitates uniform and sufficient absorption of the pump light by the thin-film array gain medium, thereby improving the pump light utilization efficiency. The periodically arrayed gain medium in the thin-film array gain medium allows the laser to be uniformly distributed in the thin film, overcoming effects such as thermal lensing and thermal stress, and improving beam quality. The saturable absorber can achieve self-starting Q-switching or mode-locking, and the pulse array form can reduce damage to the saturable absorber, enabling the laser pulse to operate stably for a long time. The phase grating layer in the external resonant cavity couples the array pulse laser, injecting it into the inner cavity for mutual modulation and locking. The array pulse laser oscillates synchronously in the composite resonant cavity, forming a combined mode laser pulse, which greatly improves the energy of the output pulse of the thin-film laser and can obtain near-diffraction-limited beam quality. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a two-dimensional array pulse self-synchronizing thin-film laser structure disclosed in one embodiment of the present invention;

[0022] Figure 2a This is a schematic diagram of the structure of the photonic crystal thin-film array gain medium disclosed in one embodiment of the present invention;

[0023] Figure 2b This is a schematic diagram of the structure of a close-packed fiber optic thin-film array gain medium disclosed in one embodiment of the present invention.

[0024] In the picture:

[0025] 1. Pump light source; 2. Heat sink; 3. First reflective layer; 4. Saturable absorber; 5. Thin-film array gain medium; 6. Second reflective layer; 7. Phase grating structure layer; 8. Third reflective layer; 9. Pump module. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings:

[0028] Example 1

[0029] like Figure 1 , Figure 2a As shown, this invention provides a two-dimensional array pulsed self-synchronizing thin-film laser structure for photonic crystals, comprising: a pump source 1, a heat sink 2, a first reflective layer 3, a saturable absorber 4, a thin-film array gain medium 5, a second reflective layer 6, a phase grating structure layer 7, a third reflective layer 8, and a pump module 9; wherein,

[0030] like Figure 2a As shown, the thin-film array gain medium 5 in this embodiment is composed of a photonic crystal array. Periodic micropores are fabricated on light-transmitting materials such as crystals, glass, or sapphire doped with rare-earth ions, creating an effective refractive index difference between the central region and the periodic micropore structure region, forming a photonic crystal structure. This structure forms a waveguide through internal total internal reflection, with each photonic crystal constituting a resonant cavity. The number of photonic crystals is greater than two, arranged in a two-dimensional array. This two-dimensional arrangement can be square, hexagonal, or other forms, used to generate periodically distributed array oscillating lasers. The array oscillating lasers pass through the photonic crystal structure multiple times through the thin-film array gain medium 5, thereby increasing the gain.

[0031] Pump source 1 is a semiconductor laser with fiber-coupled output, used to output pump laser corresponding to the absorption wavelength of rare earth ions.

[0032] Pump module 9 consists of an optical mirror group. The pump laser is focused onto the gain medium of the thin-film array through the pump module. Through the reflection of the optical mirror group, the pump laser passes through the photonic crystal thin-film array multiple times, thereby increasing the uniformity and absorption efficiency of the pump laser.

[0033] The saturable absorber 4 is made of III-V compound semiconductors, Cr:YAG, graphene or other types of materials, and has good optical quality on its surface, which is used to start and stabilize the mode-locked state.

[0034] The front end of the saturable absorber 4 is prepared with a first reflective layer 3, which is highly reflective of the oscillating laser; the rear end of the thin-film array gain medium 5 is coated with a second reflective layer 6, which partially reflects and partially transmits the oscillating laser; the first reflective layer 3 and the second reflective layer 6 are used to make the laser oscillate in the inner resonant cavity and enter the outer resonant cavity.

[0035] A phase grating structure layer 7 is disposed after the second reflective layer 6. The grating structure is etched on a light-transmitting material, and the arrangement period of the grating structure is the same as the arrangement period of the gain medium in the thin-film array. The surface of the phase grating structure layer 7 is polished, and a third reflective layer 8 is deposited on its surface. The oscillating laser is partially reflected and partially transmitted. The reflectivity provided by the third reflective layer 8 enables the laser to oscillate in the composite resonant cavity and be lased out.

[0036] Heat sink 2 is made of copper, diamond, copper-tungsten alloy or other types of materials. The composite resonant cavity is mounted and fixed on the heat sink to avoid the decrease in beam quality and stability of the output laser due to heat accumulation.

[0037] In this embodiment, the pump light output from the pump source 1 enters the composite resonant cavity through the pump module 9, passes through the thin-film array gain medium 5 multiple times, and excites the population inversion of the gain medium particles in the photonic crystal array to generate array oscillating laser. The low-intensity portion of the array oscillating laser is absorbed by the semiconductor saturable absorber 4, while the high-intensity portion passes through with less loss, thereby generating passive modulation to form a pulse. The inner resonant cavity uses the first reflective layer 3 and the second reflective layer 6 as resonant cavity mirrors. The array laser pulse enters the outer resonant cavity through the second reflective layer 6, forms coupling through the phase grating structure layer 7, and then returns to the inner resonant cavity through the third reflective layer 8, injecting into the thin-film array gain medium 5 to form light injection lock, achieving synchronous operation in the composite resonant cavity, forming a combined mode laser pulse, and generating laser lasing. During this process, the heat generated by the pump light, oscillating laser, and lasing laser is dissipated by the heat sink 1.

[0038] Example 2

[0039] like Figure 1 , Figure 2bAs shown, this invention provides a close-packed fiber two-dimensional array pulsed self-synchronizing thin-film laser structure, comprising: a pump source 1, a heat sink 2, a first reflective layer 3, a saturable absorber 4, a thin-film array gain medium 5, a second reflective layer 6, a phase grating structure layer 7, a third reflective layer 8, and a pump module 9; wherein,

[0040] like Figure 2b As shown, the thin-film array gain medium 5 in this embodiment is composed of a close-packed fiber array. Active glass fibers are obtained by drawing rare-earth ion-doped glass preforms and glass outer tubes. The active glass fibers are arranged in a two-dimensional array, with more than two fibers. The two-dimensional arrangement can be square, hexagonal, or other forms. Then, they are fused together to form a close-packed active fiber array, and the upper and lower surfaces are polished to obtain an active close-packed fiber array. Each active fiber constitutes a resonant cavity for generating periodically distributed array oscillating laser. The array oscillating laser passes through the thin-film array gain medium 5 multiple times through the active fiber, thereby improving the gain.

[0041] Pump source 1 is a semiconductor laser with fiber-coupled output, used to output pump laser corresponding to the absorption wavelength of rare earth ions.

[0042] Pump module 9 consists of an optical mirror group. The pump laser is focused onto the gain medium of the thin-film array through the pump module. Through the reflection of the optical mirror group, the pump laser passes through the densely packed fiber thin-film array multiple times, thereby increasing the uniformity and absorption efficiency of the pump laser.

[0043] The saturable absorber 4 is made of III-V compound semiconductors, Cr:YAG, graphene or other types of materials, and has good optical quality on its surface, which is used to start and stabilize the mode-locked state.

[0044] A first reflective layer 3 is fabricated on the front end face of the saturable absorber 4, which is highly reflective of the oscillating laser. A second reflective layer 6 is deposited on the rear end face of the thin-film array gain medium 5, which partially reflects and partially transmits the oscillating laser. The first reflective layer 3 and the second reflective layer 6 are used to make the laser oscillate in the inner resonant cavity and enter the outer resonant cavity.

[0045] A phase grating structure layer 7 is disposed after the second reflective layer 6. The grating structure is etched on quartz glass, and the arrangement period of the grating structure is the same as the arrangement period of the gain medium in the thin-film array. The surface of the phase grating structure layer 7 is polished, and a third reflective layer 8 is deposited on its surface. The oscillating laser is partially reflected and partially transmitted. The reflectivity provided by the third reflective layer 8 enables the laser to oscillate in the composite resonant cavity and be lased out.

[0046] Heat sink 2 is made of copper, diamond, copper-tungsten alloy or other types of materials. The composite resonant cavity is mounted and fixed on the heat sink to avoid the decrease in beam quality and stability of the output laser due to heat accumulation.

[0047] In this embodiment, the pump light output from the pump source 1 enters the composite resonant cavity through the pump module 9, passes through the thin-film array gain medium 5 multiple times, and excites the population inversion of the gain medium particles in the close-packed fiber array to generate array oscillating laser. The low-intensity portion of the array oscillating laser is absorbed by the semiconductor saturable absorber 4, while the high-intensity portion passes through with less loss, thereby generating passive modulation to form a pulse. The inner resonant cavity uses the first reflective layer 3 and the second reflective layer 6 as resonant cavity mirrors. The array laser pulse enters the outer resonant cavity through the second reflective layer 6, forms coupling through the phase grating structure layer 7, and then returns to the inner resonant cavity through the third reflective layer 8, injecting into the thin-film array gain medium 5 to form optical injection lock, achieving synchronous operation in the composite resonant cavity, forming a combined mode laser pulse, and generating laser lasing. During this process, the heat generated by the pump light, oscillating laser, and lasing laser is dissipated by the heat sink 1.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A two-dimensional array of pulsed self-synchronized flake laser structures, characterized in that, include: Heat sink, pump light source, pump module, inner resonant cavity, and outer resonant cavity; among which, The inner resonant cavity includes a first reflective layer, a saturable absorber, a thin-film array gain medium, and a second reflective layer sequentially disposed on the heat sink. The outer resonant cavity includes a phase grating structure layer and a third reflective layer sequentially disposed on the second reflective layer. The inner and outer resonant cavities constitute a composite resonant cavity. The pump light emitted by the pump source is injected into the composite resonant cavity through the pump module. After passing through the thin-film array gain medium multiple times, array oscillating laser is generated in the inner resonant cavity. At the same time, the saturable absorber absorbs and modulates the array oscillating laser, starting and maintaining the array pulse operation. The array laser pulse enters the outer resonant cavity through the second reflective layer. The phase grating structure layer couples the array pulse laser, and it returns to the inner resonant cavity through the third reflective layer for mutual injection modulation and locking, so that the array pulse laser operates synchronously in the composite resonant cavity to form a combined mode laser pulse. The thin-film array gain medium is a periodic structure formed by a light-transmitting material, including but not limited to glass, crystal, sapphire, and ceramic. The light-transmitting material is doped with one rare-earth ion or different types of rare-earth ions in a certain proportion as gain ions. The thin-film array gain medium is composed of a photonic crystal array. Periodic micropores are fabricated on the rare-earth-doped light-transmitting material, creating an effective refractive index difference between the central region and the periodic micropore structure region, forming a photonic crystal structure. This structure forms a waveguide through internal total internal reflection, with each photonic crystal constituting a waveguide. The resonant cavity contains more than two photonic crystals arranged in a two-dimensional array. The generated array oscillating laser passes through the photonic crystal structure multiple times through the thin-film array gain medium. Alternatively, the thin-film array gain medium is composed of a close-packed fiber array. Active glass fibers are obtained by drawing rare-earth-doped glass preforms and glass outer tubes. The active glass fibers are arranged in a two-dimensional array, with more than two fibers, to obtain an active close-packed fiber array. Each active fiber constitutes a resonant cavity. The generated array oscillating laser passes through the active fiber multiple times through the thin-film array gain medium. The absorption wavelength of the saturable absorber corresponds to the emission wavelength of gain ions in the gain medium of the thin-film array, thereby initiating and maintaining pulse operation in the inner resonant cavity and the composite resonant cavity.

2. The two-dimensional array of pulsed self-synchronous flake laser structures of claim 1, wherein, The pump source is a semiconductor laser or a flash lamp, and the pumping method of the pump source includes one or more of the following: front-end pumping, rear-end pumping, external cavity pumping, and lateral pumping.

3. The two-dimensional array of pulsed self-synchronous slab laser structures of claim 1 wherein, The heat sink includes, but is not limited to, one of copper, diamond, and copper-tungsten alloy.

4. The two-dimensional array of pulsed self-synchronous slab laser structures of claim 1 wherein, The pump light generated by the pump light source enters the composite resonant cavity through the pump module in a multi-channel pumping manner.

5. The two-dimensional array of pulsed self-synchronous slab laser structures of claim 1 wherein, The phase grating structure layer is formed using the same or different light-transmitting material as the gain medium of the thin-film array, and the arrangement of the grating structure corresponds to the gain medium of the thin-film array.

6. The two-dimensional array of pulsed self-synchronous slab laser structures of claim 1, wherein, The first reflective layer has high reflectivity for oscillating lasers and serves as the front end face of the inner resonant cavity and the composite resonant cavity; The second reflection layer is partially reflective and partially transmissive to the oscillation laser, is a rear end surface of the inner resonant cavity, and the provided reflectivity satisfies the oscillation laser entering the outer resonant cavity. The third reflection layer is partially reflective and partially transmissive to the oscillation laser, is a rear end surface of the outer resonant cavity and the compound resonant cavity, and the provided reflectivity satisfies the oscillation laser output.

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