Water droplet cluster optical channel penetrating method and system for laser focus axial scanning

Abstract

The invention discloses a water droplet cluster optical channel penetrating method and system for laser focus axial scanning, and belongs to the technical field of laser application and optical engineering. The system comprises a high repetition frequency pulse laser light source, a beam expander, a telescope system, a high-frequency vibration module and a scanning control module. The laser enters a telescope system after being subjected to beam expansion and collimation, a light cone with a specific convergence angle is output, and a focus is formed in a working area. The scanning control module drives the high-frequency vibration module to drive the concave lens objective lens to perform axial high-frequency micro-displacement, the light cone convergence angle is changed, and high-speed reciprocating scanning of the focus along the optical axis is achieved. The high-energy laser instantaneously vaporizes water droplets on a scanning path, and dynamic scanning inhibits the backflow of surrounding droplets, thereby forming and maintaining a low-loss temporary optical channel in a droplet cluster. The system is fast in response, high in efficiency, free of real focus, stable in light spot, high in integration level and capable of improving optical communication and detection quality in aerosol environments such as fog and haze.

Description

Technical Field

[0001] This invention relates to the fields of laser application technology and optical engineering, and in particular to a method and system for establishing a temporary optical channel in a water droplet aerosol environment using laser focal axis high-frequency scanning technology. Background Technology

[0002] In aerosol environments such as fog and haze, suspended micro-droplets cause severe scattering and absorption of light signals, leading to a sharp decline in the performance of free-space optical communication and optical detection systems. Existing technologies mainly fall into two categories: passive signal processing and active physical removal, both of which have insurmountable limitations.

[0003] Passive back-end image processing techniques, such as digital filtering and adaptive optics compensation, can only provide limited repair to degraded signals and cannot fundamentally reduce the scattering medium in the optical path. These methods become completely ineffective when the optical signal attenuates to the noise floor level.

[0004] In terms of active physical intervention, existing technologies face a dilemma: low-energy-density continuous or ordinary pulsed lasers lack the energy to instantly vaporize droplets, failing to create effective pathways within droplet clusters; while high-energy single laser pulses, although capable of breaking down droplets to form instantaneous cavities, overlook a crucial characteristic of droplet dynamics—the extremely strong reflow-filling capability of droplets on microsecond to millisecond timescales. Experimental studies show that, under normal temperature and pressure, water droplets with diameters of 10-20 μm can complete more than 50% cavity refilling within 50-200 μs after cavity formation, and completely restore the initial density distribution within 1-2 ms. This rapid reflow phenomenon, driven by surface tension, Brownian motion, and concentration gradients, makes it impossible to sustain optical channels formed by single or low-frequency sweeps (scanning frequency <100 Hz). More seriously, high-energy single-pulse solutions consume enormous amounts of energy, are bulky, and are prone to air breakdown at high energy densities, generating a plasma shielding effect that further deteriorates optical transmission conditions.

[0005] Therefore, the field of optical transmission in aerosol environments urgently needs a new technical solution that can suppress backflow through an efficient dynamic mechanism at a reasonable energy density, thereby achieving efficient connection and stability of the optical channel. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for establishing and maintaining a low-loss optical channel in a water droplet cluster by axial scanning with a laser focus. Through the synergistic mechanism of high repetition rate pulsed laser and axial high-frequency vibration of concave lens, the rapid backflow characteristics of droplets are overcome, and a technological breakthrough is achieved in establishing and maintaining a low-loss optical channel in a water droplet cluster.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A laser-focused axial scanning optical channel system for water droplets includes: a high-repetition-rate pulsed laser source (1), a laser beam expander (2), a telescope system (3), a high-frequency vibration module (4), and a scanning control module (5); the high-repetition-rate pulsed laser source (1) is used to emit a pulsed laser beam with a repetition frequency of 1-100kHz; the laser beam expander (2) is disposed on the output optical path of the laser source (1) and is used to perform spatial filtering and collimation on the laser beam; the telescope system (3) is disposed on the output optical path of the laser beam expander (2) and is used to expand the incident collimated beam and directly form a light cone with a controllable convergence angle at its output end, thereby forming a high-energy-density laser focus in the working area; The high-frequency vibration module (4) is rigidly connected to the telescope system (3). The high-frequency vibration module (4) is used to drive the concave lens to generate axial high-frequency micro-amplitude vibration with a frequency of 300Hz-10kHz and an amplitude of ±5-200μm. The scanning control module (5) is electrically connected to the high-frequency vibration module (4). The scanning control module (5) is used to drive the high-frequency vibration module (4), thereby driving the concave lens to generate precise axial displacement. By dynamically adjusting the convergence angle of the output light cone, the laser focus is realized to perform high-speed reciprocating scanning along the optical axis. The energy density at the laser focus is greater than 10J / cm², which is used to instantly vaporize water droplets on the scanning path and suppress the backflow filling of surrounding droplets on a microsecond to millisecond timescale through continuous dynamic scanning, thereby forming and maintaining a low-loss optical channel in the droplet cluster.

[0009] In the system of this invention: after beam expansion and collimation, the laser beam enters a telescope system consisting of a concave lens as the objective and a convex lens as the eyepiece. This system expands the incident collimated beam and directly outputs a light cone with a specific convergence angle at its image side, converging in the working area to form a laser focus. The scanning control module drives the high-frequency vibration module, directly causing the concave lens objective to generate axial high-frequency micro-displacement. By changing the convergence angle of the system's output light cone, high-speed reciprocating scanning of the laser focus along the optical axis is achieved. The high-energy-density laser at the focus instantly vaporizes water droplets on the scanning path, and through continuous dynamic scanning, effectively suppresses the millisecond-level rapid backflow and filling of surrounding droplets, thereby forming and maintaining a temporary, low-loss optical channel in the droplet cluster. This invention employs a synergistic mechanism of high-repetition-rate pulsed laser and concave lens axial vibration scanning, which has advantages such as fast response speed, high energy efficiency, no internal solid focus, stable spot quality, and high system integration. It can significantly improve the optical communication and detection quality in aerosol environments such as fog and haze.

[0010] Furthermore, the telescope system (3) is composed of a concave lens as an objective lens and a convex lens as an eyepiece in sequence, and the high-frequency vibration module (4) is rigidly connected to the concave lens of the telescope system (3).

[0011] Furthermore, the telescope system (3) has no real focal point inside, and its maximum energy density is lower than the air breakdown threshold.

[0012] Furthermore, the high-frequency vibration module (4) has a response frequency that matches the droplet reflux characteristic frequency. By dynamically adjusting the optical path parameters, it achieves precise control of the laser focus in the axial position, thereby maintaining the focus energy density above the droplet vaporization threshold.

[0013] Furthermore, after the laser beam is emitted from the high-repetition-rate pulsed laser (1), it is initially collimated by the laser beam expander (2) and then enters the telescope system (3). The telescope system used in this invention is composed of a concave lens as the objective and a convex lens as the eyepiece. This structure has no real focal point, which can effectively prevent the laser from breaking through the air due to energy accumulation in the transmission path. The system expands the incident collimated beam and directly outputs a light cone with a specific convergence angle at its image side, which converges in the working area to form a laser focal point; the scanning control module (5) drives the high-frequency vibration module (4) to generate high-frequency micro-amplitude vibration, which directly drives the concave lens objective in the telescope system (3) to produce a precise axial micro-displacement. The axial displacement of the concave lens changes the convergence angle of the system's output light cone, thereby realizing high-speed reciprocating scanning of the laser focal point along the optical axis.

[0014] This invention provides a method for penetrating the optical channel of a water droplet cluster using laser focal axial scanning, comprising the following steps:

[0015] A laser beam with a repetition frequency of 1-100kHz and a single pulse energy of 1-200mJ is emitted from a high repetition rate pulsed laser source (1);

[0016] The laser beam is spatially filtered and collimated by the laser beam expander (2), and the output is a parallel beam with wavefront distortion less than λ / 5;

[0017] The collimated beam enters the telescope system (3) consisting of concave and convex lenses in sequence, is expanded and directly output as a light cone with a specific convergence angle, and converges to form a laser focus in the working area;

[0018] The scanning control module (5) drives the high-frequency vibration module (4) to generate high-frequency micro-amplitude vibration with a frequency of 300Hz-10kHz and an amplitude of ±5-200μm; the high-frequency vibration drives the concave lens to generate axial displacement, and by changing the convergence angle of the output light cone, the laser focus can achieve high-speed reciprocating scanning along the optical axis within a certain range.

[0019] Using a high-energy-density laser (>10 J / cm²) at the focal point, water droplets on the scanning path are instantly vaporized to form micro-explosive cavitation. By maintaining the high-frequency vibration and focal scanning, the repeated irradiation interval at any axial position is made smaller than the time scale of significant droplet backflow, so as to dynamically suppress the rapid backflow and filling of surrounding droplets, thereby forming and maintaining a temporary, low-loss optical channel in the droplet cluster.

[0020] The key innovation of this invention lies in actively overcoming the inherent limitations of static focusing methods, such as limited effective distance and rapid energy divergence, through axial vibration scanning. Although the energy of a single static focal spot rapidly decays outside the focal plane and cannot effectively act on droplets in the depth direction, this invention expands a transient, high-energy "point-like" focal spot into a continuous "columnar" effective region with energy density consistently maintained above the droplet vaporization threshold by causing the focal spot to reciprocate at high frequency along the optical axis. This dynamic focusing mechanism allows laser energy to uniformly and continuously cover an axial path, rather than being concentrated on a single, momentary, and easily defocused point.

[0021] Crucially, due to the rapid backfilling characteristics of atmospheric water droplets on the order of microseconds to milliseconds, this invention maintains the aforementioned high-frequency continuous scanning, enabling the laser focus to create a dynamic "sweeping" effect along the axial path. When a droplet at a certain location is vaporized to form a transient cavitation bubble, the scanning focus will sweep across the area again within a very short time before the droplet has completed its backfilling, further clearing away newly formed droplets. This synergistic mechanism of "compensating for energy dissipation with dynamic scanning and suppressing droplet backflow with continuous intervention" effectively overcomes the dual challenges of short static focusing distance and rapid droplet backfilling.

[0022] The high-energy-density laser at the focal point instantly vaporizes water droplets along the scanning path, forming micro-explosive cavitation. Simultaneously, the continuous dynamic scanning suppresses the backflow and filling of surrounding droplets, ultimately forming and maintaining a temporary, low-loss optical channel within the droplet cluster, thus ensuring the normal operation of the subsequent optical instruments.

[0023] The laser-focused axial scanning method for establishing an optical channel for water droplets, provided by this invention, has the core advantage of combining high-repetition-rate pulsed laser with high-speed axial vibration scanning technology using a concave lens, enabling active and precise physical intervention on the droplet clusters. This method directly vibrates the concave lens objective to generate micro-displacement, and by changing the convergence angle of the system's output light cone, it drives the laser focus to perform high-speed reciprocating scanning along the optical axis. The high-energy-density laser at the focal point instantly vaporizes the water droplets along the scanning path. Simultaneously, the high-frequency continuous dynamic scanning effectively suppresses the rapid backflow and filling of surrounding droplets, thereby establishing and maintaining a temporary, low-loss optical channel.

[0024] This method, by directly driving lightweight optical components and combining them with high-repetition-rate pulsed lasers, avoids the speed bottleneck of traditional mechanical Z-axis motion, resulting in faster response and higher precision. Furthermore, because energy is concentrated on the focal scanning path rather than irradiating a large area, it features relatively low energy consumption and minimal thermal impact. Simultaneously, this optical structure fundamentally ensures that there is no solid focal point within the system, resulting in high safety. The beam quality is stable, the channel connectivity is significant, the system has strong compatibility, and it is easy to integrate into existing optical equipment. Attached Figure Description

[0025] Figure 1 A schematic diagram of a method and system structure for laser-focused axial scanning of optical channels through water droplets;

[0026] Figure 2 This is a schematic diagram of the microscopic mechanism of the dynamic process of establishing and maintaining an optical channel in a droplet cluster using the method described in this invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following examples provide a more detailed description of the invention. It should be noted that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0028] like Figure 1 As shown, a laser focal axial scanning optical channel system for water droplets mainly includes: a high repetition rate pulsed laser source 1, a laser beam expander 2, a telescope system 3, a high frequency vibration module 4, and a scanning control module 5. A laser beam expander 2 is disposed on the output optical path of the laser source (1), and a telescope system 3 is disposed on the output optical path of the laser beam expander 2. The telescope system 3 is composed of a concave lens as an objective lens and a convex lens as an eyepiece in sequence. A high-frequency vibration module 4 is rigidly connected to the concave lens of the telescope system 3, and a scanning control module 5 is electrically connected to the high-frequency vibration module 4. The scanning control module 5 is used to drive the high-frequency vibration module 4, thereby causing the concave lens to generate a precise axial displacement. By dynamically adjusting the convergence angle of the output light cone, the laser focus is realized to perform high-speed reciprocating scanning along the optical axis. The energy density at the laser focus is greater than 10 J / cm², which is used to instantly vaporize water droplets on the scanning path and suppress the backflow and filling of surrounding droplets on a microsecond to millisecond timescale through continuous dynamic scanning, thereby forming and maintaining a low-loss optical channel in the droplet cluster.

[0029] The working process of the device of the present invention is as follows: After the high repetition rate pulsed laser beam is emitted from the laser 1, it is initially collimated by the laser beam expander 2, and then enters the telescope system 3. The telescope system 3 is composed of a concave lens as the objective lens and a convex lens as the eyepiece. This system expands the incident collimated beam and directly outputs a light cone with a specific convergence angle at its end, which converges in the working area to form a laser focus.

[0030] The scanning control module 5 drives the high-frequency vibration module 4, causing it to generate high-frequency micro-amplitude vibrations. This vibration directly drives the concave lens objective in the telescope system 3 to produce precise axial micro-displacements. The displacement of the concave lens changes the convergence angle of the system's output light cone, thereby enabling high-speed reciprocating scanning of the laser focus along the optical axis.

[0031] Crucially, by maintaining high-frequency continuous scanning, a dynamic suppression zone is formed in the droplet cluster: when the water droplets on the scanning path are instantly vaporized by the high-energy-density laser, the laser focus will sweep across the area again in a very short time before the surrounding droplets have had time to complete their backfilling, thus achieving continuous removal of newly formed droplets.

[0032] The high-energy-density laser at the focal point instantly vaporizes water droplets along the scanning path, forming micro-cavitation bubbles. Simultaneously, continuous dynamic scanning suppresses the backflow and filling of surrounding droplets, ultimately forming and maintaining a temporary, low-loss optical path within the droplet cluster, thus ensuring the normal operation of subsequent optical instruments. The clear propagation path of light throughout the telescope system shows no solid focal point; this characteristic effectively avoids the risk of high-energy lasers breaking down the air inside the system, verifying the rationality and safety of the optical design.

[0033] Figure 2 This is a schematic diagram illustrating the microscopic mechanism of the dynamic process of establishing and maintaining an optical channel within a droplet cluster using the method described in this invention. The sequence of figures details the complete physical process by which the laser focus clears backflowing droplets, thereby maintaining a clear channel.

[0034] Figure 2 (a) illustrates the initial state of the system, in which a preliminary, droplet-free optical channel is successfully established within a water droplet cluster using the method of this invention. In this stage, the laser focus creates a temporary, low-loss optical channel by instantaneously vaporizing the droplets along the high-energy-density path.

[0035] like Figure 2 (b) describes the state after the optical channel has formed. At this point, due to factors such as concentration gradient, Brownian motion, and surface tension, surrounding droplets begin to flow back and fill the newly formed optical channel, posing a threat to its stability. To address this issue, when droplets attempt to invade the optical channel, a high-energy-density laser at the focal point immediately acts on these droplets, preventing further intrusion.

[0036] Figure 2 (c) Explains the process by which the high-frequency vibration module drives the concave lens to produce a minute displacement, causing the laser focus to reciprocate at high speed along the optical axis. This process not only clears droplets from the current path but also continuously suppresses the rapid backflow and filling of surrounding droplets, thereby maintaining the openness and stability of the optical channel. This step emphasizes the dynamic "sweeping" effect of the laser focus, ensuring that the optical channel does not close rapidly due to the rapid filling of droplets.

[0037] Figure 2 (d) focuses on the microscopic scale, showing the precise penetration of a single droplet by a laser focal point. This figure illustrates how light undergoes secondary refraction and self-focusing within the droplet, enabling efficient laser energy deposition that instantly penetrates the droplet and creates an initial cavity. This process visually reveals the instantaneous destruction mechanism of high-energy-density lasers on droplets.

[0038] Figure 2 (e) illustrates the evolution of the cavity after the droplet is punctured. The droplet material vaporized by the laser energy generates high pressure, causing the cavity to expand rapidly, forming a so-called micro-explosion. This micro-explosion not only effectively disperses surrounding droplets but also further enhances the stability of the optical channel.

[0039] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A water droplet cluster optical channel penetration system with laser focal point axial scanning, characterized in that, The system comprises a high-repetition-rate pulsed laser light source (1), a laser beam expander (2), a telescope system (3), a high-frequency vibration module (4), and a scanning control module (5). The high-repetition-rate pulsed laser light source (1) is used to emit a pulsed laser beam with a repetition frequency of 1-100 kHz; the laser beam expander (2) is arranged on the light path of the laser light source (1) and is used to spatially filter and collimate the laser beam; the telescope system (3) is arranged on the light path of the laser beam expander (2), and the telescope system (3) is used to expand the incident collimated light beam and directly form a light cone with a controllable convergence angle at the output end thereof, so as to form a high-energy-density laser focal point in a working area; the high-frequency vibration module (4) is rigidly connected with the telescope system (3), and the high-frequency vibration module (4) is used to drive the concave lens to produce an axial high-frequency micro-vibration with a frequency of 300 Hz-10 kHz and an amplitude of ±5-200 μm; the scanning control module (5) is electrically connected with the high-frequency vibration module (4); the scanning control module (5) is used to drive the high-frequency vibration module (4), so as to drive the concave lens to produce an accurate axial displacement, to realize a high-speed reciprocating scanning of the laser focal point along the optical axis direction by dynamically adjusting the convergence angle of the output light cone; the energy density at the laser focal point is greater than 10 J / cm², which is used to instantaneously gasify water droplets on a scanning path and to suppress the backflow filling of surrounding droplets on a microsecond to millisecond time scale through continuous dynamic scanning, so as to form and maintain a low-loss optical channel in the droplet group.

2. The water droplet cluster optical channel penetration system of laser focal point axial scanning according to claim 1, characterized in that, The telescope system (3) is sequentially composed of a concave lens as an objective lens and a convex lens as an ocular lens, and the high-frequency vibration module (4) is rigidly connected with the concave lens of the telescope system (3).

3. The water droplet cluster light channel penetrating system of axial scanning of laser focal point according to claim 1, characterized in that, The telescope system (3) has no real focal point inside, and the maximum energy density is lower than the air breakdown threshold.

4. The water droplet cluster light channel penetrating system of axial scanning of laser focal point according to claim 1, characterized in that, The high-frequency vibration module (4) has a response frequency matched with a droplet backflow characteristic frequency, and the laser focal point is accurately controlled in the axial position by dynamically adjusting the optical path parameters, so that the focal point energy density is always higher than the droplet gasification threshold.

5. The water droplet group light channel penetrating system of any one of claims 1-4, wherein, After the laser beam is emitted from the high-repetition-rate pulsed laser (1), it is primarily collimated by the laser beam expander (2) and then enters the telescope system (3); the telescope system (3) has no real focal point inside, and the system expands the incident collimated light beam and directly outputs a light cone with a specific convergence angle at the image side, so as to converge to form a laser focal point in a working area; The scanning control module (5) drives the high-frequency vibration module (4) to produce a high-frequency micro-vibration, which directly drives the concave lens objective lens in the telescope system (3) to produce an accurate axial micro-displacement. The axial displacement of the concave lens changes the convergence angle of the output light cone of the system, so as to realize a high-speed reciprocating scanning of the laser focal point along the optical axis direction.

6. A method for laser focus axial scanning of water droplet clusters optical channel penetration, characterized by that, The method comprises the following steps: a laser beam with a repetition frequency of 1-100 kHz and a single-pulse energy of 1-200 mJ is emitted by a high-repetition-rate pulsed laser light source (1); The laser beam is filtered and collimated by a laser beam expander (2), and the output parallel beam has a wavefront distortion less than λ / 5; The collimated beam enters a telescope system (3) composed of a concave lens and a convex lens, is expanded and directly output as a light cone with a specific convergence angle, and converges to form a laser focal point at the working area; A scanning control module (5) drives a high-frequency vibration module (4) to generate high-frequency micro-vibration with a frequency of 300 Hz-10 kHz and an amplitude of ±5-200 μm; the high-frequency vibration drives the concave lens to produce axial displacement, changes the convergence angle of the output light cone, and realizes high-speed reciprocating scanning of the laser focal point within a certain range along the optical axis direction; The high-energy density laser (>10 J / cm²) at the focal point makes the water droplets on the scanning path instantaneously vaporize to form a micro-explosion cavity; maintaining the high-frequency vibration and focal point scanning makes the repeated irradiation interval at any axial position less than the time scale of significant backflow of the droplets, dynamically inhibiting the rapid backflow of the surrounding droplets to fill in, thereby forming and maintaining a temporary and low-loss optical channel in the droplet cluster.

Images