A nanosecond-picosecond combined laser

Abstract

The present invention relates to the field of lasers, and in particular to a nanosecond-picosecond combination laser, comprising a passive Q-switched resonant cavity, an amplifying module, a second half-wave plate, a first polarization beam splitter prism, an SBS pulse compression module, a time delay module, and a third polarization beam splitter prism. The center points of the passive Q-switched resonant cavity, the amplifying module, the second half-wave plate, the first polarization beam splitter prism, the SBS pulse compression module, and the third polarization beam splitter prism are aligned, and the first polarization beam splitter prism, the time delay module, and the third polarization beam splitter prism are opposite to each other. The passive Q-switched resonant cavity generates nanosecond linearly polarized seed light, which then enters the amplifying module for power amplification. The amplified seed light passes through the second half-wave plate and is divided into a first seed light and a second seed light in the first polarization beam splitter prism. The first seed light is modularized into picosecond light through SBS pulse compression, and the second seed light is combined with the picosecond light in the third polarization beam splitter prism through the time delay module. The present invention has a simple structure and good stability.

Description

Technical Field

[0001] The present invention relates to the field of lasers, and in particular to a nanosecond-picosecond combined laser. Background Art

[0002] With the development of science and technology, CCD plays an irreplaceable role in infrared guidance, high-altitude reconnaissance, precise positioning, etc. due to its advantages of high photon conversion efficiency, wide spectral response, low cost and small size. However, as the core component of the optoelectronic system, CCD is extremely susceptible to interference and destruction by laser weapons, and has therefore become the primary target of attack in optoelectronic confrontation.

[0003] Since the 1990s, researchers have used various radiation sources to conduct damage experiments on photodetectors. Lasers, with their advantages such as narrow pulse width and high power, have gradually become a research hotspot. Later, researchers combined different types of lasers into a new laser source to conduct damage experiments on target materials such as single-crystal silicon and metallic aluminum. The results showed that the combined laser significantly increased the damage rate on the target material, especially the laser composed of a combination of pulsed lasers, which had a more significant destructive effect. Single-crystal silicon and metallic aluminum are precisely the components of CCDs, so the combined laser can produce a stronger induced breakdown effect on CCDs. Therefore, a good combined laser is very necessary.

[0004] Laser combination can combine the outputs of two lasers with different pulse widths, but this requires very high synergy between the lasers, making it difficult to achieve simultaneous output. Another method is to use one laser to output a long pulse width laser, then use pulse compression to narrow its pulse width, and then combine the narrowed laser with the original pump light to produce a combined laser output. Among pulse compression technologies, SBS is the most commonly used pulse compression technology due to its simple structure, phase conjugation, and high load capacity. Summary of the Invention

[0005] To address the difficulty in controlling the optical path of traditional laser combination systems using two lasers, this invention uses a single laser and pulse compression to generate lasers with different pulse widths. The optical path is then controlled using polarization beam combining to couple the two laser beams together, producing a combined laser output. This solves the problem of difficult optical path control and poor coupling between the two laser beams.

[0006] In order to achieve the above-mentioned purpose, the technical solution of the present invention is implemented as follows: a nanosecond-picosecond combination laser, characterized in that it includes a passively Q-switched resonant cavity, an amplification module, a second half-wave plate, a first polarization beam splitter prism, an SBS pulse compression module, a time delay module and a third polarization beam splitter prism, the center points of the passively Q-switched resonant cavity, the amplification module, the second half-wave plate, the first polarization beam splitter prism, the SBS pulse compression module and the third polarization beam splitter prism are arranged on the same horizontal line, and the center points of the first polarization beam splitter prism, the time delay module and the third polarization beam splitter prism are arranged on the same horizontal line; the passively Q-switched resonant cavity generates nanosecond linearly polarized seed light, the seed light enters the amplification module for power amplification, the amplified seed light passes through the second half-wave plate, and is divided into a first seed light and a second seed light in the first polarization beam splitter prism, the first seed light enters the SBS pulse compression module to generate picosecond light, the second seed light enters the time delay module, and the second seed light and the picosecond light are combined in the third polarization beam splitter prism.

[0007] The passive Q-switched resonant cavity includes a first 0° total reflection mirror, a partial reflection mirror, a first polarizer, a first quarter wave plate, a passive Q-switched crystal, a first LD side pump module, a second quarter wave plate and an output mirror, which are arranged in sequence. The center points of the first 0° total reflection mirror, the partial reflection mirror, the first polarizer, the first quarter wave plate, the passive Q-switched crystal, the first LD side pump module, the second quarter wave plate and the output mirror are arranged on the same horizontal line, and the seed light is output by the output mirror and enters the amplification module.

[0008] A first optical isolator is provided between the amplifying module and the second half-wave plate, and the center points of the amplifying module, the first optical isolator and the second half-wave plate are arranged on the same horizontal line.

[0009] The first optical isolator includes a second polarizer, a Faraday rotator, a first half-wave plate and a third polarizer arranged in sequence, and the center points of the second polarizer, the Faraday rotator, the first half-wave plate and the third polarizer are arranged on the same horizontal line.

[0010] A third half-wave plate is provided between the SBS pulse compression module and the third polarization beam splitter prism, and the centers of the SBS pulse compression module, the third half-wave plate and the third polarization beam splitter prism are arranged on the same horizontal line.

[0011] The SBS pulse compression module includes a second polarization beam splitter prism, a third quarter wave plate, a first positive lens and a Brillouin medium cell arranged in sequence, and the center points of the second polarization beam splitter prism, the third quarter wave plate, the first positive lens and the Brillouin medium cell are arranged on the same horizontal line.

[0012] The Brillouin medium cell is provided with a first window mirror, the thickness of the first window mirror is d1, and the first window mirror and the center point of the first positive lens are arranged on the same horizontal line.

[0013] The focal length f of the first positive lens satisfies the constraint condition:

[0014] L+n1d1+D4≤f<L+n1d1+D4+L1

[0015] Where n1 is the refractive index of the lens, D4 is the distance between the center of the first positive lens and the center of the first window mirror, L is the optimal interaction distance of stimulated Brillouin scattering, and L = cτ p / 2n2, c is the speed of light in vacuum, τ p is the pulse width of the first seed light, L1 is the length of the Brillouin medium cell, and L<L1, n2 is the refractive index of the Brillouin medium.

[0016] The delay module includes three 45° reflectors, wherein the optical path of the delay module is L t Satisfy the constraints:

[0017] L t =D1+n1(d2+d5)+2L p +D6+D7-D5

[0018] Wherein, D1 is the distance between the first polarization beam splitter prism and the second polarization beam splitter prism, D5 is the distance between the first polarization beam splitter prism and the time delay module, D6 is the distance between the third polarization beam splitter prism and the third half-wave plate, D7 is the distance between the third half-wave plate and the third polarization beam splitter prism, d2 is the thickness of the second polarization beam splitter prism, d5 is the thickness of the third half-wave plate, L p is the optical path of the first seed light in the SBS pulse compressor, and L p =D2+n1(d1+d3+d4)+D3+D4, where D2 is the distance between the second polarization splitter prism and the third quarter-wave plate, D3 is the distance between the third quarter-wave plate and the first positive lens, D4 is the distance between the first positive lens and the Brillouin medium cell, d3 is the thickness of the third quarter-wave plate, and d4 is the thickness of the first positive lens.

[0019] The present invention, which employs the above-mentioned structure, has a simple structure and good stability and can be used in fields such as optoelectronic countermeasures and material testing. The present invention utilizes the properties of the first polarization beam splitter prism, which projects horizontally polarized light and reflects vertically polarized light, to process the nanosecond laser output by the passively Q-switched resonant cavity, thereby converting one laser beam into two laser beams. This solves the problem of difficulty in coordinating and controlling two lasers and simplifies the device structure. The present invention compresses the nanosecond laser to generate a picosecond laser using an SBS pulse compressor, which has a simple structure and high compression efficiency. At the same time, the present invention utilizes a third polarization beam splitter prism to couple the two laser beams into one laser beam through a polarization beam combining method, which overcomes the difficulty in calculating the optical path length of the two lasers, simplifies the laser structure, and achieves a better combination effect. The generated laser is composed of a combination of pulsed lasers, which has a faster damage rate on the target material and a more significant destructive effect. This solves the problem of low damage rate of laser weapons in optoelectronic countermeasures and greatly promotes in-depth research on the damage mechanism of CCDs, a core component in optoelectronic systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 It is a structural schematic diagram of the present invention.

[0022] Figure 2 Schematic diagram of the structure of the passive Q-switched resonant cavity of the present invention.

[0023] Figure 3 Schematic diagram of the beam splitting of the present invention.

[0024] Figure 4 Schematic diagram of the structure of the SBS pulse compression module.

[0025] Figure 5 Schematic diagram of optical path calculation for the delay module.

[0026] In the figure, 1 is a passive Q-switched resonant cavity, 2 is a power amplifier module, 3 is the first optical isolator, 4 is the second half-wave plate, 5 is the first polarization beam splitter, 6 is an SBS pulse compression module, 7 is the third half-wave plate, 8 is a time delay module, 9 is the third polarization beam splitter, 1-1 is the first 0° total reflection mirror, 1-2 is the first partial reflection mirror, 1-3 is the first polarizer, 1-4 is the first quarter-wave plate, 1-5 is a passive Q-switched crystal, 1-6 is the first LD side pump module, 1-7 is the second quarter-wave plate, 1-8 is the output mirror, 6-1 is the second polarization beam splitter, 6-2 is the third quarter-wave plate, 6-3 is the first positive lens, and 6-4 is the Brillouin medium cell. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0028] like Figure 1 As shown, a nanosecond-picosecond combination laser includes a passively Q-switched resonant cavity 1, an amplifying module 2, a second half-wave plate 4, a first polarization beam splitter prism 5, an SBS pulse compression module 6, a time delay module 8, and a third polarization beam splitter prism 9. The centers of the passively Q-switched resonant cavity 1, the amplifying module 2, the second half-wave plate 4, the first polarization beam splitter prism 5, the SBS pulse compression module 6, and the third polarization beam splitter prism 9 are arranged on the same horizontal line, and the centers of the first polarization beam splitter prism 5, the time delay module 8, and the third polarization beam splitter prism 9 are opposite to each other.

[0029] The main function of the passive Q-switched resonant cavity 1 is to generate single longitudinal mode linearly polarized seed light, such as Figure 2As shown, the passively Q-switched resonant cavity 1 includes a first 0° total reflection mirror 1-1, a partial reflection mirror 1-2, a first polarizer 1-3, a first quarter wave plate 1-4, a passively Q-switched crystal 1-5, a first LD side pump module 1-6, a second quarter wave plate 1-7 and an output mirror 1-8, which are arranged in sequence. The center points of the first 0° total reflection mirror 1-1, the partial reflection mirror 1-2, the first polarizer 1-3, the first quarter wave plate 1-4, the passively Q-switched crystal 1-5, the first LD side pump module 1-6, the second quarter wave plate 1-7 and the output mirror 1-8 are arranged on the same horizontal line. The passively Q-switched resonant cavity 1 utilizes a first 0° total reflection mirror 1-1 and an output mirror 1-8 to form a resonant cavity. The saturable absorption characteristics of the passively Q-switched crystal 1-5 maintain a high-loss state in the dynamic Q-switched resonant cavity 1. This population inversion within the dynamic Q-switched resonant cavity 1 causes continuous energy accumulation. Once this energy accumulates to a certain level, the transmittance of the passively Q-switched crystal 1-5 increases dramatically. The laser within the passively Q-switched resonant cavity 1 continuously oscillates within the cavity, continuously extracting upper-level particles accumulated by the LD side pump module 1-6. During this oscillation process, the laser light is rapidly amplified, forming giant pulses. The laser light within the passively Q-switched resonant cavity 1 oscillates between the first 0° reflection mirror 1-1, the first partial reflection mirror 1-2, and the output mirror 1-8, forming a three-dimensional resonance. The first polarizer 1-3 polarizes the laser light, and the output mirror 1-8 outputs a nanosecond linearly polarized seed beam, which is single longitudinal mode light. After the seed light is output by the output mirror 1-8, it passes through the amplifier module 2 and the first optical isolator 3 in sequence. The main function of the amplifier module 2 is to amplify the power of the seed light. The main function of the first optical isolator 3 is to ensure that the seed light is transmitted in one direction to prevent the reverse transmission light from damaging the amplifier module 2. The first optical isolator 3 includes a second polarizer, a Faraday rotator, a first half-wave plate and a third polarizer. The center points of the second polarizer, the Faraday rotator, the first half-wave plate and the third polarizer are arranged on the same horizontal line.

[0030] like Figure 3As shown, the power-amplified seed light sequentially passes through the second half-wave plate 4 and the first polarization beam splitter prism 5. The second half-wave plate 4 phase-delays the incident nanosecond linearly polarized seed light, changing its polarization direction, converting it into obliquely polarized seed light. The phase delay of the second half-wave plate 4 controls the polarization rotation angle of the nanosecond linearly polarized seed light, adjustable from 0° to 45°. By utilizing the properties of the first polarization beam splitter prism 5 that project horizontally polarized light and reflect vertically polarized light, the obliquely polarized seed light is split into a first seed light and a second seed light, solving the problem of difficult coordinated control of the two lasers and simplifying the device structure. The first seed light is horizontally polarized, and the second seed light is vertically polarized. The energy ratio between the first and second seed lights is determined by the angle of polarization rotation. After passing through the first polarization beam splitter prism 5, the first seed light enters the SBS pulse compression module 6 to generate picosecond light, while the second seed light enters the time delay module 8.

[0031] like Figure 4 As shown, the SBS pulse compression module 6 includes a second polarization beam splitter prism 6-1, a third quarter wave plate 6-2, a first positive lens 6-3 and a Brillouin medium cell 6-4, which are arranged in sequence. The center points of the second polarization beam splitter prism 6-1, the third quarter wave plate 6-2, the first positive lens 6-3 and the Brillouin medium cell 6-4 are arranged on the same horizontal line. Figure 5 As shown, the Brillouin medium cell 6-4 is provided with a first window mirror, the thickness of the first window mirror is d1, and the center point of the first window mirror and the first positive lens 6-3 are arranged on the same horizontal line. The focal length f of the first positive lens 6-3 should meet the following constraints:

[0032] L+n1d1+D4≤f<L+n1d1+D4+L1

[0033] Where n1 is the refractive index of the lens, D4 is the distance between the center of the first positive lens and the center of the first window mirror, L is the optimal interaction distance of stimulated Brillouin scattering, and L = cτ p / 2n2, c is the speed of light in vacuum, τ pis the pulse width of the first seed light, L1 is the length of the Brillouin medium cell 6-4, where L<L1, and n2 is the refractive index of the Brillouin medium. After entering the SBS pulse compression module 6, the first seed light is first separated into circularly polarized picosecond light and circularly polarized seed light by the second polarization beam splitter prism 6-1 and the third quarter-wave plate 6-2. The primary function of the first positive lens 6-3 is to increase the power density of the circularly polarized picosecond light and circularly polarized seed light. This increased power density generates an electrostrictive effect at the focus of the first positive lens 6-3, thereby exciting the phonon field to produce Stokes seed light. The Stokes seed light passes through the first positive lens 6-3 and enters the Brillouin medium cell 6-4, which contains the SBS organic medium. The primary function of this Brillouin medium cell 6-4 is to generate stimulated Brillouin scattering to produce backward Stokes seed light. The backward Stokes seed light is output from the Brillouin medium cell 6-4, passes through the first positive lens 6-3, and enters the third quarter-wave plate 6-2 to be converted into vertically polarized Stokes light. It is then reflected by the second polarization beam splitter prism 6-1. The Stokes light is output from the second polarization beam splitter prism 6-1, passes through the third half-wave plate 7, and enters the third polarization beam splitter prism 9.

[0034] The delay module 8 that the second seed light enters is composed of three 45° reflectors. The main function of the delay module 8 is to compensate for the optical path difference between the second seed light and the first seed light, so that the pulse peaks of the first seed light and the second seed light reach the third polarization beam splitter prism 9 at the same time. The optical path L of the delay module is 1. t The following constraints should be met:

[0035] L t =D1+n1(d2+d5)+2L p +D6+D7-D5

[0036] Wherein D1 is the distance between the first polarization splitter prism 5 and the second polarization splitter prism 6-1, D5 is the distance between the first polarization splitter prism 5 and the time delay module 8, D6 is the distance between the third polarization splitter prism 6-1 and the third half-wave plate 7, D7 is the distance between the third half-wave plate 7 and the third polarization splitter prism 9, d2 is the thickness of the second polarization splitter prism 6-1, d5 is the thickness of the third half-wave plate 7, L p is the optical path of the first seed light in the SBS pulse compressor, and L p=D2+n1(d1+d3+d4)+D3+D4, where D2 is the distance between the second polarization beam splitter 6-1 and the third quarter-wave plate 6-2, D3 is the distance between the third quarter-wave plate 6-2 and the first positive lens 6-3, D4 is the distance between the first positive lens 6-3 and the Brillouin medium cell 6-4, d3 is the thickness of the third quarter-wave plate 6-2, and d4 is the thickness of the first positive lens 6-3. After being processed by the time delay module 8, the second seed light enters the third polarization beam splitter prism 9. Within the third polarization beam splitter prism 9, the first and second seed lights utilize polarization beam combining to couple nanosecond and picosecond light outputs, forming the output laser. This overcomes the difficulty in calculating the optical path lengths of the two lasers and simplifies the laser structure. At the same time, the first seed light and the second seed light are both pulsed lasers. The output laser formed by the combination of pulsed lasers has a faster damage rate on the target material and a more significant destructive effect, which solves the problem of low damage rate of laser weapons in optoelectronic confrontation and greatly promotes in-depth research on the damage mechanism of CCD, the core component in the optoelectronic system.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A nanosecond-picosecond combination laser, characterized in that: The invention comprises a passive Q-switched resonant cavity (1), an amplifying module (2), a second half-wave plate (4), a first polarization beam splitter prism (5), an SBS pulse compression module (6), a time delay module (8) and a third polarization beam splitter prism (9), wherein the centers of the passive Q-switched resonant cavity (1), the amplifying module (2), the second half-wave plate (4), the first polarization beam splitter prism (5), the SBS pulse compression module (6) and the third polarization beam splitter prism (9) are arranged on the same horizontal line, and the centers of the first polarization beam splitter prism (5), the time delay module (8) and the third polarization beam splitter prism (9) are opposite to each other; The passive Q-switched resonant cavity (1) generates nanosecond linearly polarized seed light, the seed light enters the amplification module (2) for power amplification, the amplified seed light passes through the second half-wave plate (4), and is separated into a first seed light and a second seed light in a first polarization beam splitter prism (5), the first seed light enters the SBS pulse compression module (6) to generate picosecond light, the second seed light enters the time delay module (8), and the second seed light and the picosecond light are combined in a third polarization beam splitter prism (9).

2. The nanosecond-picosecond combination laser according to claim 1, characterized in that: The passive Q-switched resonant cavity (1) comprises a first 0° total reflection mirror (1-1), a partial reflection mirror (1-2), a first polarizer (1-3), a first quarter wave plate (1-4), a passive Q-switched crystal (1-5), a first LD side pump module (1-6), a second quarter wave plate (1-7) and an output mirror (1-8) which are arranged in sequence. The center points of the first 0° total reflection mirror (1-1), the partial reflection mirror (1-2), the first polarizer (1-3), the first quarter wave plate (1-4), the passive Q-switched crystal (1-5), the first LD side pump module (1-6), the second quarter wave plate (1-7) and the output mirror (1-8) are arranged on the same horizontal line. The seed light is output by the output mirror (1-8) and enters the amplification module (2).

3. The nanosecond-picosecond combination laser according to claim 1 or 2, characterized in that: A first optical isolator (3) is provided between the amplifying module (2) and the second half-wave plate (4), and the center points of the amplifying module (2), the first optical isolator (3) and the second half-wave plate (4) are arranged on the same horizontal line.

4. The nanosecond-picosecond combination laser according to claim 3, characterized in that: The first optical isolator (3) comprises a second polarizer, a Faraday rotator, a first half-wave plate and a third polarizer which are arranged in sequence, and the center points of the second polarizer, the Faraday rotator, the first half-wave plate and the third polarizer are arranged on the same horizontal line.

5. The nanosecond-picosecond combination laser according to claim 1 or 4, characterized in that: A third half-wave plate (7) is provided between the SBS pulse compression module (6) and the third polarization beam splitter prism (9), and the center points of the SBS pulse compression module (6), the third half-wave plate (7), and the third polarization beam splitter prism (9) are arranged on the same horizontal line.

6. The nanosecond-picosecond combination laser according to claim 5, characterized in that: The SBS pulse compression module (6) comprises a second polarization beam splitter prism (6-1), a third quarter wave plate (6-2), a first positive lens (6-3) and a Brillouin medium pool (6-4) which are arranged in sequence, and the center points of the second polarization beam splitter prism (6-1), the third quarter wave plate (6-2), the first positive lens (6-3) and the Brillouin medium pool (6-4) are arranged on the same horizontal line.

7. The nanosecond-picosecond combination laser according to claim 6, characterized in that: The Brillouin medium pool (6-4) is provided with a first window mirror, the thickness of the first window mirror is d1, and the center point of the first window mirror and the first positive lens (6-3) are arranged on the same horizontal line.

8. The nanosecond-picosecond combination laser according to claim 7, characterized in that: The focal length f of the first positive lens (6-3) satisfies the constraint condition: L+n1d1+D4≤f <L+n1d1+D4+L1 Where, n1 is the refractive index of the lens, D4 is the distance between the center of the first positive lens (6-3) and the center of the first window mirror, L is the optimal interaction distance of stimulated Brillouin scattering, and L = cτ p / 2n2, c is the speed of light in vacuum, τ p is the pulse width of the first seed light, L1 is the length of the Brillouin medium cell (6-4), and L < L1, n2 is the refractive index of the Brillouin medium.

9. The nanosecond-picosecond combination laser according to any one of claims 1, 6-8, characterized in that: The time delay module (8) comprises three 45° reflectors, wherein the optical path L of the time delay module is t Satisfy the constraints: <h2 style=";text-align:left;direction:ltr">L<h2 style=";text-align:left;direction:ltr"> t <h2 style=";text-align:left;direction:ltr"> =D1+n1(d2+d5)+2L<h2 style=";text-align:left;direction:ltr"> p <h2 style=";text-align:left;direction:ltr"> +D6+D7-D5 Wherein, D1 is the distance between the first polarization beam splitter prism (5) and the second polarization beam splitter prism (6-1), D5 is the distance between the first polarization beam splitter prism (5) and the time delay module (8), D6 is the distance between the third polarization beam splitter prism (6-1) and the third half-wave plate (7), D7 is the distance between the third half-wave plate (7) and the third polarization beam splitter prism (9), d2 is the thickness of the second polarization beam splitter prism (6-1), d5 is the thickness of the third half-wave plate (7), L p is the optical path of the first seed light in the SBS pulse compressor, and L p =D2+n1(d1+d3+d4)+D3+D4, D2 is the distance between the second polarization splitter prism (6-1) and the third quarter wave plate (6-2), D3 is the distance between the third quarter wave plate (6-2) and the first positive lens (6-3), D4 is the distance between the first positive lens (6-3) and the Brillouin medium cell (6-4), d3 is the thickness of the third quarter wave plate (6-2), and d4 is the thickness of the first positive lens (6-3).

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