CN201425689Y - Optical structure of cascaded double-pass laser amplifier - Google Patents

Abstract

The utility model relates to a laser amplifier optical path, in particular to an optical path structure for multi-stage amplification of laser main oscillation light. Including an optical isolator and an amplifying part, the optical isolator includes a first polarizer, a 1/2 wave plate, a Faraday rotator and a second polarizer. The amplifying part includes an amplifying branch composed of the first laser medium, the first 1/4 wave plate, and the first reflector, and a third polarizer, the second laser medium, the second 1/4 wave plate, and the second reflector , the third laser medium, the third 1/4 wave plate and the third reflector constitute the magnifying arm. The light from the amplification branch and the amplification arm is coupled through the third polarizer in the center of the structure, and the seed light is reflected by the second polarizer after three-stage double-pass amplification. The utility model ensures that each laser medium is a double-pass amplification, improves the gain efficiency, suppresses the self-excited oscillation, ensures the beam quality of the amplified laser, and can conveniently cascade the amplified arms.

Description

Optical structure of cascaded double-pass laser amplifier

technical field

The utility model relates to a laser amplifier optical path, specifically an optical path structure for multi-stage amplification of laser main oscillation light. The amplifier is easy to perform multi-stage cascading, and can realize multi-stage double-pass amplification for the laser generated by main oscillation.

Background technique

Laser master oscillation amplification is a commonly used technology to achieve high-power, high-energy laser output. First, a laser (called the main oscillator) generates a weak optical signal (seed light) with excellent performance, and then injects it into a one-stage or multi-stage laser amplifier to obtain optical amplification. In order to obtain a higher gain amplification factor, the method of increasing the number of gain media or allowing the seed light to pass through the gain media multiple times is usually adopted. The former is called multi-stage single-pass amplification, and the latter is called multi-pass amplification. At present, the single-pass amplifier only allows the seed light to pass through the gain medium once, and its utilization rate is low; and when multi-stage cascading, due to the inconsistency of the gain medium parameters, it is difficult to get good compensation for thermal depolarization and thermal distortion, so that the seed light is While zooming in, the beam quality is severely degraded. For multi-channel amplification, especially four-channel amplification, it is easy to generate self-excited oscillation, which seriously affects the amplification efficiency. How to suppress self-excited oscillation, compensate thermally induced depolarization and thermal distortion, and ensure beam quality while ensuring high utilization efficiency of the gain medium are issues that need to be considered when designing an optical amplification structure.

Utility model content

The purpose of this utility model is to aim at the technical characteristics of the laser amplifier, using the polarization element and the method of changing the polarization state of the laser, to propose a method that is easy to cascade, satisfies high gain medium utilization efficiency, and can well suppress Self-oscillating and compensating heat-induced depolarization multi-stage double-pass amplifier optical circuit structure.

所有偏振片满足光线布儒斯特角θ入射。In order to achieve the above purpose, the utility model adopts the following technical solutions: the utility model includes an optical isolator for introducing seed light and an amplifying part for amplifying the seed light output from the optical isolator. The optical isolator includes a first polarizer, a 1/2 wave plate, a Faraday rotator and a second polarizer sequentially placed along the propagation direction of the seed light. The amplifying part includes an amplifying branch consisting of the first laser medium, the first 1/4 wave plate, and the first reflector, and a third polarizer, the second laser medium, the second 1/4 wave plate, the first An amplifying arm composed of two reflection mirrors, a third laser medium, a third 1/4 wave plate and a third reflection mirror. The first laser medium, the first 1/4 wave plate and the first reflector in the amplification branch are sequentially arranged along the propagation direction of the output light of the optical isolator, and the third polarizer in the amplification arm is placed between the second polarizer and the amplification Between the first laser medium in the branch, the second laser medium, the second 1/4 wave plate and the second reflector are sequentially placed on the obliquely lower side of the third polarizer, and the second obliquely upper side is sequentially placed Three laser media, the third 1/4 wave plate and the third mirror, and the third polarizer, the second laser medium, the second 1/4 wave plate, the second mirror, the third laser medium, the third 1/ 4 wave plate and the third mirror are on the same optical axis. The angle between the optical axis of the amplifying branch and the optical axis of the amplifying arm is

All polarizers meet the incident light Brewster angle θ.

The number of amplifying arms arranged between the second polarizer and the first laser medium is 1-5. When the number of amplifying arms is 2-5, the optical axes of each amplifying arms are arranged in parallel.

The 1/4 wave plate in the amplification branch and the amplification arm can be replaced by a 45° Faraday rotator.

Compared with the existing structure, the utility model has the following advantages: 1) It ensures that each laser medium is a double-pass amplification, which improves the gain efficiency; 2) Due to the continuous change of the polarization state of the light during the amplification process, reasonable It compensates the thermal depolarization effect of the laser medium and ensures the beam quality of the amplified laser; 3) Due to the continuous change of the polarization state, it is difficult for the laser to go back and forth directly between the mirrors, thereby inhibiting the self-excited oscillation; when the laser is operated by multi-mode Or when the thermal depolarization caused by too high energy, the depolarized light will enter the optical isolator along the main optical axis and be reflected from the polarizer 1 without forming multiple round trips with the reflector. The generation of self-excited oscillation is suppressed; 4) If a higher amplification gain is required, cascading of amplification arms can be conveniently performed (see Figure 2); 5) The structure is compact.

Description of drawings

Fig. 1 is the first structural representation of the utility model

In the figure: 1, the first polarizer, 2, 1/2 wave plate, 3, 45 ° Faraday rotator, 4, the second polarizer, 5, the third polarizer, 6, the first laser medium, 7, the first One 1/4 wave plate, 8, the first reflection mirror, 9, the second laser medium, 10, the second 1/4 wave plate, 11, the second reflection mirror, 12, the third laser medium, 13, the third 1 /4 wave plate, 14, the third mirror

Fig. 2 is the second structural representation of the utility model

In the figure: a is the first enlarged support arm, including elements 5, 9, 10, 11, 12, 13, and 14 in Fig. 1

b is the expanded second enlarged support arm, the structure is the same as a

c is the extended third enlarged support arm, the structure is the same as a

Detailed ways

Below in conjunction with accompanying drawing, the utility model is further described:

所有偏振片满足光线布儒斯特角θ入射。种籽光从图1左端入射，经过三级双通放大后，由第二偏振片4反射而出。As shown in FIG. 1, this embodiment includes an optical isolator for introduction of seed light and an amplification section for amplifying the seed light output from the optical isolator. The optical isolator includes a first polarizer 1 , a 1/2 wave plate 2 , a Faraday rotator 3 and a second polarizer 4 sequentially placed along the propagation direction of the seed light. The amplifying part includes an amplifying branch consisting of the first laser medium 6, the first 1/4 wave plate 7, and the first mirror 8, and the third polarizer 5, the second laser medium 9, and the second 1/4 wave plate 10. An amplifying arm composed of the second reflection mirror 11 , the third laser medium 12 , the third 1/4 wave plate 13 and the third reflection mirror 14 . The first laser medium 6, the first 1/4 wave plate 7 and the first reflector 8 in the amplification branch are arranged in sequence along the output light propagation direction of the optical isolator, and the third polarizer 5 in the amplification arm is placed on the second Between the polarizer 4 and the first laser medium 6 in the amplification branch, and the first polarizer 1, 1/2 wave plate 2, 45° Faraday rotator 3, the second polarizer 4, the third polarizer 5, The first laser medium 6, the first 1/4 wave plate 7, and the first total reflection mirror 8 are on the same optical axis. On the obliquely lower side of the third polarizer 5, the second laser medium 9, the second 1/4 wave plate 10 and the second mirror 11 are placed in sequence in a direction away from the third polarizer 5, and the obliquely upper side is arranged in a direction away from the third polarizer 5. The direction of the third polarizer 5 is placed with the third laser medium 12, the third 1/4 wave plate 13 and the third reflection mirror 14 in sequence, and the third polarizer 5, the second laser medium 9, the second 1/4 wave The plate 10, the second mirror 11, the third laser medium 12, the third 1/4 wave plate 13 and the third mirror 14 are on the same optical axis. The light of the amplification branch and the amplification arm is coupled through the third polarizer 5 in the center of the structure, and the angle between the optical axis of the amplification branch and the optical axis of the amplification arm is

All polarizers meet the Brewster angle θ incidence of light. The seed light is incident from the left end of FIG. 1 , and is reflected by the second polarizer 4 after three-stage double-pass amplification.

The seed light generated by the main oscillator must be horizontally polarized light. As shown in Figure 1, it enters the first polarizer 1 from the left end at the Brewster angle of this wavelength, and passes through the 1/2 wave plate 2 , 45° Faraday rotator 3, and the optical isolator composed of the second polarizer 4 are incident on the third polarizer 5, continue to transmit to the first laser medium 6 for first-stage amplification, and then pass through the first 1/4 wave plate After 7, it becomes circularly polarized light, returns to the first reflector 8 and then passes through the first 1/4 wave plate 7 to become vertically polarized light, passes through the first laser medium 6 for first-stage re-amplification, and reaches the third polarization plate 5, reflected to the second laser medium 9 for second-stage amplification, and becomes circularly polarized light after passing through the second 1/4 wave plate 10, and then incident on the second reflector 11, returning to the second 1/4 wave plate Become horizontally polarized light, pass through the second laser medium 9 for second-stage re-amplification, transmit to the third laser medium 12 after reaching the third polarizer 5 for third-stage amplification, and then enter the third 1/4 wave plate 13 It becomes circularly polarized light, and then enters the third mirror 14. After returning, it passes through the third 1/4 wave plate 13 and becomes vertically polarized light. After passing through the third laser medium 12, the third stage is re-amplified, and then enters the It is reflected on the third polarizer 5, and reflected again on the second polarizer 4, and the amplification process is completed at this point, which is a total of three times of double-pass amplification. If a higher amplification gain is required, the amplifying arms can be expanded. In this embodiment, three amplifying arms are selected, that is, the second and third (optional) amplifying arms are added, as shown in Figure 2, and each The optical axis of the magnifying arm is arranged parallel. Note: When the 1/4 wave plate cannot change the polarization state of all light due to the severe thermal depolarization caused by multi-mode operation or high energy of the laser, the 1/4 wave plate between the laser medium and the mirror (such as 7,10,13) among the accompanying drawing 1 can be changed into 45 ° of Faraday rotators.

Claims (3)

1. Cascaded double-pass laser amplifier optical path structure, including an optical isolator for introducing seed light and an amplifying part for amplifying the seed light output from the optical isolator; the optical isolator includes The first polarizer (1), the 1/2 wave plate (2), the Faraday rotator (3) and the second polarizer (4) placed in sequence in the direction; it is characterized in that: the described amplifying part includes Medium (6), the first 1/4 wave plate (7), the amplification branch composed of the first reflection mirror (8) and the third polarizer (5), the second laser medium (9), the second 1/4 4 wave plate (10), the second reflection mirror (11), the third laser medium (12), the third 1/4 wave plate (13) and the amplification arm composed of the third reflection mirror (14); the amplification branch The first laser medium (6), the first 1/4 wave plate (7) and the first reflection mirror (8) in the optical isolator are arranged in sequence along the output light propagation direction of the optical isolator, and the third polarizer (5) in the amplifying arm ) is placed between the second polarizer (4) and the first laser medium (6) in the amplification branch, and the second laser medium (9), The second 1/4 wave plate (10) and the second reflecting mirror (11), the third laser medium (12), the third 1/4 wave plate (13) and the third reflecting mirror ( 14), and the third polarizer (5), the second laser medium (9), the second 1/4 wave plate (10), the second mirror (11), the third laser medium (12), the third 1 /4 wave plate (13) and the third reflecting mirror (14) are on the same optical axis; the included angle between the optical axis of the amplification branch and the optical axis of the amplification arm is

All polarizers meet the incident light Brewster angle θ. 2. The cascaded double-pass laser amplifier optical path structure according to claim 1, characterized in that: the number of amplifying arms arranged between the second polarizer (4) and the first laser medium (6) is 1 -5; when the number of amplifying arms is 2-5, the optical axes of each amplifying arm are arranged in parallel. 3. The cascaded double-pass laser amplifier optical circuit structure according to claim 1 or claim 2, characterized in that the 1/4 wave plate in the amplifying branch and the amplifying arm can be replaced by a 45° Faraday rotator.

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