CN114759424A - Compact high-gain ultrafast laser amplifier - Google Patents

Compact high-gain ultrafast laser amplifier Download PDF

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Publication number
CN114759424A
CN114759424A CN202210659725.6A CN202210659725A CN114759424A CN 114759424 A CN114759424 A CN 114759424A CN 202210659725 A CN202210659725 A CN 202210659725A CN 114759424 A CN114759424 A CN 114759424A
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dichroic mirror
pump
light
laser
laser source
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CN202210659725.6A
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王春华
虞华康
赵裕兴
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Dongguan University of Technology
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Dongguan University of Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094038—End pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094096—Multi-wavelength pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/0941—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode
    • H01S3/09415—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light of a laser diode the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
    • H01S3/10023—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by functional association of additional optical elements, e.g. filters, gratings, reflectors

Abstract

The invention relates to the technical field of laser amplifiers, and discloses a compact high-gain ultrafast laser amplifier, which comprises a seed laser source, a polarization splitting prism, a dual-wavelength double-end pumping structure and a reflecting structure, wherein the seed laser source is connected with the polarization splitting prism; a first pump laser source and a second pump laser source in the dual-wavelength double-end pump structure are oppositely arranged; the seed laser is reflected by the polarization beam splitter prism and the first trichroid mirror, then enters the first end of the main amplification module, exits from the second end of the main amplification module, and is reflected out of the pumping light path by the second trichroid mirror; and the second three-color mirror is reflected back to the second three-color mirror by the reflecting structure, enters the polarization beam splitter prism after sequentially passing through the main amplification module and the first three-color mirror, and is emergent in a direction perpendicular to the initial incidence direction. And a double-end pumping structure is adopted to avoid Yb: the amplification loss caused by insufficient density of reversed particles at the rear end of the YAG crystal bar improves the gain of the laser amplifier; the seed laser is amplified again through the reflection structure, so that the light path folding is realized, and the whole structure is more compact.

Description

Compact high-gain ultrafast laser amplifier
Technical Field
The present invention relates to the field of devices for amplifying or generating light using a light amplification process using stimulated emission of radiation (laser) in a new generation of information technology, and more particularly, to a compact high-gain ultrafast laser amplifier.
Background
The high-power ultrafast laser plays a plurality of roles in various fields such as industry, scientific research, national defense and the like. The kilowatt-level high-power ultrafast laser at present is mainly based on optical fiber, slab and thin-chip laser doped with Yb material. The ultra-fast laser based on the Yb/YAG end-pumped rod-shaped structure has a huge application prospect in the industrial field due to simple structure and convenient maintenance.
The high-power amplification module of the existing Yb-YAG end-pumped rod-shaped structure-based industrial laser mostly adopts a single-ended pump structure. Because of the high power high brightness fiber coupled diode double-end pumping, the remaining unabsorbed pump light may hit the opposite pump laser diode, damage the pump laser diode or reduce its lifetime. The Yb/YAG single-end pump rod-shaped structure has two disadvantages: on one hand, due to the exponential absorption of the crystal to the pump light during single-ended pumping, the pumping power density of the rear half section of the Yb, namely the YAG rod is reduced, and the density of reversed particles of the rear half section is insufficient, so that the amplification loss is caused, and the amplification gain effect is influenced; on the other hand, the pumping power provided by the fiber-coupled pumping module is limited, and the total pumping power of the single-ended pump and the double-ended pump is only half of the total pumping power, which is not beneficial to high-power amplification. The existing single-ended pumping structure has difficulty in obtaining high gain for small signal amplification.
Disclosure of Invention
The invention aims to provide a compact high-gain ultrafast laser amplifier, and aims to solve the problem that in the prior art, the amplification gain is influenced by large amplification loss of a rear half section in a single-ended pumping structure.
The invention is realized in this way, a compact high-gain ultrafast laser amplifier, including seed laser source, polarization beam splitter prism, dual-wavelength double-end pumping structure and reflecting structure; the dual-wavelength double-end pump structure comprises a first pump laser source, a first pump coupling system, a first dichroic mirror, a main amplification module, a second dichroic mirror, a second pump coupling system and a second pump laser source which are sequentially arranged; the first pump laser source and the second pump laser source are oppositely arranged; the first pump light output by the first pump laser source is incident to the first dichroic mirror after being adjusted by the first pump coupling system, is incident to the first dichroic mirror after being transmitted by the first dichroic mirror, and is incident to the first dichroic mirror after being transmitted by the first dichroic mirror; second pump light output by the second pump laser source is incident to the second dichroic mirror after being adjusted by the second pump coupling system, is incident to the second dichroic mirror after being transmitted by the second dichroic mirror, and is incident to the second dichroic mirror after being transmitted by the second dichroic mirror; the second pump light emitted from the first end of the main amplification module is transmitted by the first dichroic mirror and then reflected out of the pump light path by the first dichroic mirror; the first pump light emitted from the second end of the main amplification module is transmitted by the second dichroic mirror and then reflected out of a pump light path by the second dichroic mirror; after passing through the polarization beam splitter prism, the seed laser output by the seed laser source enters the first dichroic mirror, is reflected by the first dichroic mirror, then enters the first end of the main amplification module, is amplified by the main amplification module, then exits from the second end of the main amplification module, and then is reflected out of the pumping light path by the second dichroic mirror; and the second three-color mirror is reflected back to the second three-color mirror by the reflecting structure, sequentially passes through the main amplification module and the first three-color mirror, enters the polarization beam splitter prism, and emits out of the light path from the emergent direction, wherein the emergent direction is perpendicular to the initial incident direction of the seed laser.
Optionally, the reflection structure includes a polarization rotation plate and a mirror, the polarization rotation plate is configured to change a polarization state of the seed laser, and the mirror reflects the seed laser emitted from the pump optical path back to the pump optical path.
Optionally, the reflection structure further includes a collimating lens, and the seed laser emitted from the pumping optical path sequentially passes through the polarization rotation plate and the collimating lens and then enters the reflecting mirror; after being reflected by the reflector, the seed laser sequentially passes through the collimating lens and the polarization rotating sheet and then is incident to the second dichroic mirror, and the seed laser returning to the second dichroic mirror rotates by 90 degrees in polarization state compared with the seed laser emitted from the pumping light path before.
Optionally, the laser device further comprises a preamplifier, wherein the preamplifier comprises a pulse stretcher and a pulse selector, and the pulse stretcher and the pulse selector are respectively used for stretching pulses and reducing the frequency of the seed laser.
Optionally, the polarization beam splitter further comprises an optical isolator and a half-wave plate, and the seed laser amplified by the preamplifier sequentially passes through the optical isolator and the half-wave plate and then enters the polarization beam splitter prism.
Optionally, the dual-wavelength double-ended pump structure further includes an absorption well for absorbing the first pump light or the second pump light which is emitted from the opposite side and is not absorbed completely.
Optionally, the main amplification module comprises a Yb: YAG crystal bar, the first pump laser source is a 969nm laser source, and the second pump laser source is a 940nm laser source; the central wavelength of the seed laser output by the seed laser source is 1030 nm.
Optionally, one side of the first dichroic mirror facing the first pump laser source is highly transparent to light with a wavelength of 969 nm; one side of the first dichroic mirror facing the main amplification module is highly transparent to light with a wavelength of 969nm and highly reflective to light with a wavelength of 940 nm; one side of the second dichroic mirror facing the second pump laser source is highly transparent to light with the wavelength of 940 nm; the side of the second dichroic mirror facing the main amplification module is highly transparent to light with a wavelength of 940nm and highly reflective to light with a wavelength of 969 nm.
Optionally, the double face of the first dichroic mirror is highly transparent to light with wavelengths of 940nm and 969nm, and the side of the first dichroic mirror facing the main amplification module is highly reflective to light with a wavelength of 1030 nm; the double face of the second dichroic mirror is highly transparent to light with wavelengths of 940nm and 969nm, and the side, facing the main amplification module, of the second dichroic mirror is highly reflective to light with a wavelength of 1030 nm.
Optionally, the seed laser output by the seed laser source is any one of a continuous laser, a quasi-continuous laser, or an ultrashort pulse laser.
Compared with the prior art, the compact high-gain ultrafast laser amplifier provided by the invention adopts a double-end pumping structure, so that the amplification loss caused by insufficient density of reversed particles at the rear end of a Yb/YAG crystal bar during single-end pumping can be avoided, the loss is reduced, and the gain of a main amplification module is improved; the double-end pumping power of the first-level dual-wavelength double-end pumping structure can be doubled relative to that of single-end pumping, so that the main amplification module obtains higher power amplification capability.
And because the first dichroic mirror and the second dichroic mirror reflect the first pump light or the second pump light which is emitted from the opposite side and is not absorbed out of the pump light path, the residual pump light passing through the main amplification module cannot be emitted into the opposite optical fiber coupling pump module, the service life of the optical fiber coupling pump module is protected, and the long-term use reliability of the high-power industrial ultrafast laser amplifier is met.
The amplified seed laser is reflected back to the dual-wavelength double-end pumping structure through the reflection structure to be amplified again, the folding of the light path is realized, and the seed laser is emitted from the polarization splitting prism in the direction perpendicular to the initial incident direction, so that the whole structure is more compact, and the miniaturization of the whole high-power ultrafast laser amplifier is facilitated.
Drawings
Fig. 1 is a schematic diagram of an optical path of a compact high-gain ultrafast laser amplifier provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The following detailed description of implementations of the invention refers to specific embodiments.
The same or similar reference numerals in the drawings of the present embodiment correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of the description, but it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed in a specific orientation and operate, and therefore the terms describing the positional relationship in the drawings are only used for illustrative purposes and are not to be construed as limiting the present patent, and it is possible for one of ordinary skill in the art to understand the specific meaning of the above terms according to the specific situation.
Referring to fig. 1, a preferred embodiment of the present invention is shown.
A compact high-gain ultrafast laser amplifier comprises a seed laser source 1, a polarization beam splitter 19 (PBS), a dual-wavelength double-end pump structure and a reflection structure;
the dual-wavelength double-end pump structure comprises a first pump laser source 20, a first pump coupling system 4, a first dichroic mirror 5, a first dichroic mirror 7, a main amplification module 21, a second dichroic mirror 9, a second dichroic mirror 10, a second pump coupling system 12 and a second pump laser source 22 which are sequentially arranged; the first pump laser source 20 and the second pump laser source 22 are arranged oppositely;
the first pump light output by the first pump laser source 20 is adjusted by the first pump coupling system 4, then enters the first dichroic mirror 5, is transmitted by the first dichroic mirror 5, enters the first dichroic mirror 7, is transmitted by the first dichroic mirror 7, and then enters the first end of the main amplification module 21;
second pump light output by the second pump laser source 22 is adjusted by the second pump coupling system 12, then enters the second dichroic mirror 10, is transmitted by the second dichroic mirror 10, enters the second dichroic mirror 9, is transmitted by the second dichroic mirror 9, and then enters the second end of the main amplification module 21;
the second pump light emitted from the first end of the main amplification module 21 is transmitted by the first dichroic mirror 7 and then reflected out of the pump light path by the first dichroic mirror 5;
the first pump light emitted from the second end of the main amplification module 21 is transmitted by the second dichroic mirror 9 and then reflected by the second dichroic mirror 10 to form a pump light path;
the seed laser output by the seed laser source 1 is incident to the first dichroic mirror 7 after passing through the polarization splitting prism 19, is reflected by the first dichroic mirror 7, then is incident to the first end of the main amplification module 21, is amplified by the main amplification module 21, then is emitted from the second end of the main amplification module 21, and then is reflected out of the pumping light path through the second dichroic mirror 9; and is reflected back to the second dichroic mirror 9 by the reflection structure, and then enters the polarization splitting prism 19 after sequentially passing through the main amplification module 21 and the first dichroic mirror 7, and is emitted out of the light path from the emitting direction, wherein the emitting direction is perpendicular to the initial incident direction of the seed laser.
The compact high-gain ultrafast laser amplifier provided by the embodiment adopts a double-end pumping structure, and can avoid amplification loss caused by insufficient density of reversed particles at the rear end of a Yb/YAG crystal bar during single-end pumping, thereby reducing loss and improving gain of a main amplification module; the double-end pumping structure with the first-level dual-wavelength can realize double pumping power relative to single-end pumping, so that the main amplification module obtains higher power amplification capability.
In addition, because the first dichroic mirror 5 and the second dichroic mirror 10 reflect the first pump light or the second pump light which is irradiated from the opposite side and is not absorbed out of the pump light path, the residual pump light which passes through the main amplification module 21 cannot be irradiated into the opposite optical fiber coupling pump module, the service life of the optical fiber coupling pump module is protected, and the long-term use reliability of the high-power industrial ultrafast laser amplifier is met.
The amplified seed laser is reflected back to the dual-wavelength double-end pumping structure through the reflection structure to be amplified again, the folding of the light path is realized, and the seed laser is emitted from the polarization beam splitter prism 19 in the direction perpendicular to the initial incidence direction, so that the whole structure is more compact, and the miniaturization of the whole high-power ultrafast laser amplifier is facilitated.
The seed laser light output from the seed laser light source 1 is any one of continuous laser light, quasi-continuous laser light, and ultrashort pulse laser light.
Specifically, the reflection structure includes a polarization rotation plate 23 and a reflection mirror 25, the polarization rotation plate 23 is used for changing the polarization state of the seed laser, and the reflection mirror 25 reflects the seed laser emitted from the pumping optical path back to the pumping optical path.
The reflecting structure further comprises a collimating lens 24, and the seed laser emitted from the pumping light path sequentially passes through the polarization rotating sheet 23 and the collimating lens 24 and then is incident to a reflecting mirror 25; after being reflected by the reflecting mirror 25, the seed laser sequentially passes through the collimating lens 24 and the polarization rotating plate 23 and then enters the second dichroic mirror 9, and the polarization state of the seed laser returning to the second dichroic mirror 9 is rotated by 90 degrees compared with the seed laser emitted from the pumping light path before.
The polarization rotator 23 may be a 45 ° Quartz rotator (Quartz Rotators) made of Quartz crystal. The quartz crystal has natural optical activity, so that it can be used to rotate the polarization direction of linearly polarized light without changing the characteristics of the linearly polarized light. The rotation angle is related to the thickness of the crystal, and the rotation direction can be selected from left rotation and right rotation at present. The default is right-hand.
A compact high gain ultrafast laser amplifier further comprises a preamplifier 17, the preamplifier 17 comprising a pulse stretcher and a pulse selector for stretching pulses and down-converting the seed laser, respectively. The power of the seed laser can be improved by pulse stretching through the pulse stretcher, seed laser frequency reduction and multistage pre-amplification through the pulse selector, and the better two-way small signal extraction of the follow-up main amplification module 21 is facilitated.
The compact type high-gain ultrafast laser amplifier also comprises an optical isolator 14 and a half-wave plate 18, and seed laser amplified by a preamplifier 17 sequentially passes through the optical isolator 14 and the half-wave plate 18 and then enters a polarization beam splitter prism 19.
The optical isolator 14 is a passive optical device that allows only one-way light to pass through, and light reflected by the optical fiber echo can be well isolated by the optical isolator 14, and the optical isolator 14 mainly uses the faraday effect of the magneto-optical crystal. The optical isolator 14 is a passive device which allows light to pass through in one direction and prevents the light from passing through in the opposite direction, and has the function of limiting the direction of the light, so that the light can be transmitted only in one direction, and the light reflected by the optical fiber echo can be well isolated by the optical isolator 14, so that the light wave transmission efficiency is improved.
The half-wave plate 18 is a birefringent crystal of a thickness such that when normally incident light is transmitted, the phase difference between ordinary light (o-light) and extraordinary light (e-light) is equal to pi or an odd multiple thereof. The half-wave plate 18 can rotate polarized light, because linearly polarized light is perpendicularly incident to the half-wave plate, transmitted light is still linearly polarized light, and if the included angle between the vibration plane and the main cross section of the crystal during incidence is theta, the vibration plane of the transmitted linearly polarized light is rotated by 2 theta degrees from the original direction.
The polarization splitting prism 19 is an optical element that a multilayer film structure is plated on an inclined surface of a right-angle prism, then the polarization splitting prism is bonded with another right-angle prism to form a cubic structure, and the P-polarization transmittance and the S-polarization transmittance of light incident at the brewster angle are respectively 1 and less than 1, so that the P-polarization component is completely transmitted and most of the S-polarization component is reflected (at least more than 90%) after the light passes through the multilayer film structure for multiple times at the brewster angle.
The polarization state of the seed laser reflected back to the dual-wavelength dual-end pump structure by the reflection structure is rotated by 90 °, so that when the seed laser again enters the polarization splitting prism 19, the polarization state thereof is rotated by 90 ° compared with that at the time of initial incidence, and the direction in which the seed laser exits from the polarization splitting prism 19 is perpendicular to the exit-entrance direction. For example, the seed laser light is initially incident on the polarization splitting prism 19 as S-polarized light, and is reflected by it to the first dichroic mirror 7; when the amplified seed laser is incident on the polarization splitting prism 19 from the first dichroic mirror 7, the seed laser is incident as P-polarized light and directly transmits out of the polarization splitting prism 19, and the emergent direction of the seed laser is perpendicular to the initial incident direction, so that the subsequent optical elements can be conveniently arranged and the output light can be effectively utilized.
The dual-wavelength double-ended pump structure further comprises an absorption trap for absorbing the first pump light or the second pump light which is not absorbed and is emitted from the opposite side. The residual pump light can not be emitted into the opposite optical fiber coupling pump module, the service life of the optical fiber coupling pump module is protected, and the reliability of long-term use is met; so that the remaining pump light does not adversely affect or interfere with the devices in the pump optical path.
Specifically, the main amplification module 21 comprises a Yb/YAG crystal bar, the first pump laser source 20 is a 969nm laser source, and the second pump laser source 22 is a 940nm laser source; the seed laser light output from the seed laser light source 1 has a center wavelength of 1030 nm.
The gain medium in the main amplification module 21 is a quasi-three-level Yb: YAG crystal rod, and the Yb: YAG crystal mainly has two spectral absorption peaks, one is near 940nm, and the other is near 969 nm. The dual-wavelength absorption characteristic of the Yb: YAG crystal is fully utilized in the embodiment, so that double pumping power is provided under the same laser brightness.
Specifically, the side of the first dichroic mirror 5 facing the first pump laser source 20 is highly transparent (transmittance is greater than 98%) to light with a wavelength of 969 nm; the first dichroic mirror 5 has a high transmittance (transmittance greater than 98%) for light having a wavelength of 969nm and a high reflectance (reflectance greater than 99%) for light having a wavelength of 940nm on the side facing the main amplification block 21. The 969nm first pump light emitted by the first pump laser source 20 passes through the first dichroic mirror 5, and the 940nm second pump light emitted by the second pump laser source 22 passes through the first dichroic mirror 5 after being emitted from the opposite side through the main amplification module 21, and is reflected out of the pump light path by the first dichroic mirror 5, so that the first pump laser source 20 is prevented from being damaged by the residual light.
The side of the second dichroic mirror 10 facing the second pump laser source 22 is highly transmissive to light of 940nm wavelength (transmittance greater than 98%); the second dichroic mirror 10 has a high transmittance (transmittance greater than 98%) for light having a wavelength of 940nm and a high reflectance (reflectance greater than 99%) for light having a wavelength of 969nm on the side facing the main amplification block 21. 940nm second pump light emitted by the second pump laser source 22 passes through the second dichroic mirror 10, and 969nm first pump light emitted by the first pump laser source 20 is emitted to the second dichroic mirror 10 from the opposite side through residual light after passing through the main amplification module 21, and is reflected out of a pump light path by the second dichroic mirror 10, so that the second pump laser source 22 is prevented from being damaged by the residual light.
The first dichroic mirror 5 and the second dichroic mirror 10 are arranged at an angle of 45 ° with respect to the pumping optical path.
Specifically, the pair of surfaces of the first dichroic mirror 7 is highly transmissive to light with wavelengths of 940nm and 969nm (transmittance is greater than 98%), and the side of the first dichroic mirror 7 facing the main amplification block 21 is highly reflective to light with a wavelength of 1030nm (reflectance is greater than 99.5%). The first dichroic mirror 7 is highly transparent to light with wavelengths of 940nm and 969nm, and the loss of the first dichroic mirror in a pumping light path is reduced as much as possible; and the first dichroic mirror 7 is highly reflective to light with a wavelength of 1030nm, so that the seed laser is well coupled into a pumping light path, and the loss of the seed laser during coupling is reduced.
The double face of the second dichroic mirror 9 is highly transmissive for light with wavelengths of 940nm and 969nm (transmittance greater than 98%), and the side of the second dichroic mirror 9 facing the main amplification module 21 is highly reflective for light with a wavelength of 1030nm (reflectance greater than 99.5%). The second dichroic mirror 9 is highly transparent to light with wavelengths of 940nm and 969nm, so that the loss of the second dichroic mirror in a pumping light path is reduced as much as possible; and the second dichroic mirror 9 is highly reflective to light with a wavelength of 1030nm, so that the amplified seed laser is well coupled out of the pumping light path, and the loss of the amplified seed laser during coupling out is reduced.
The Yb: YAG crystal rod is a thin rod structure, the diameter of the crystal rod is 1-10 mm, the length of the crystal rod is 20-50 mm, the Yb3+ ion doping concentration is 0.5-2.0 at.%, and preferably, the Yb: YAG crystal rod is 30mm in length, and the Yb3+ ion doping concentration is 2.0 at.%.
The first pump coupling system 4 and the second pump coupling system 12 are both double-lens pump coupling systems, and the beam transformation is used for controlling the spot size of the beam waist of the pump in the Yb: YAG rod.
In the above two-lens pump coupling system, two aspheric lenses arranged oppositely can be used for implementation.
A compact high-gain ultrafast laser amplifier also includes a pulse compression device, and light emitted from the polarization beam splitter prism 19 is compressed by the pulse compression device and then emitted. The pulse compression device may employ a compression grating, for example: the Watatch Photonics' EVPG laser pulse compression grating is suitable for pulse compression and expansion of high-power ultrafast laser.
In one embodiment, a compact high gain ultrafast laser amplifier includes the following components:
the seed laser source 1 is a seed femtosecond laser source, the central wavelength is 1030nm, and the pulse repetition frequency is 100 kHz-1 MHz.
The preamplifier 17 is a low-power preamplifier stage, and is used for broadening (typical value: 100 kHz-1 MHz) and reducing (typical value: 1 mW-5W) the seed laser pulse and pre-amplifying (typical value: 1 kHz-5W).
An optical isolator 14.
The half-wave plate 18 is a 1030nm half-wave plate.
A polarization beam splitter 19, a 1030nm polarization beam splitter.
The pulse compression device 16 is a compressed grating pair.
The first pump laser source 20 is a wavelength-locked high brightness 969nm fiber coupled laser diode module, and typical parameters are as follows: the output optical fiber core diameter is 105um, NA0.22, and the output power is 120W.
The first pump coupling system 4 injects the pump light output by the 969nm fiber coupled laser diode module into the Yb: YAG rod in a set size.
The first dichroic mirror 5 has high transmittance at 969nm and 45 degrees, transmittance greater than 98%, and high reflectance at 940nm and 45 degrees, and reflectance greater than 99%. And the high transmittance is 45 degrees, namely when the included angle between the incident light and the normal line of the dichroic mirror is 45 degrees, the high transmittance is realized on the incident light. 45 degree high reflection, namely, when the angle between the incident light and the normal of the dichroic mirror (or reflector) is 45 degree, the incident light has high reflectivity.
The first absorption trap 6 absorbs 940nm pump light which is not absorbed by the opposite side.
The first dichroic mirror 7 has high transmittance of 45 degrees at 940nm and 969nm wavelengths, the transmittance is greater than 98 percent, and the reflectance is greater than 99.5 percent at 45 degrees at 1030 nm.
The main amplification module 21 consists of a Yb: YAG bar with a typical length of 30mm and a doping concentration of 2at.% and a cooler.
The second dichroic mirror 9 has high transmittance at 45 degrees of 940nm and 969nm, transmittance greater than 98 percent, and high reflectance at 45 degrees of 1030nm, and reflectivity greater than 99.5 percent.
The second dichroic mirror 10 has high transmittance at 940nm wavelength of 45 degrees and high reflectance at 969nm wavelength of 45 degrees, wherein the transmittance is larger than 98 percent, and the reflectance is larger than 99 percent.
And a second absorption well 11 for absorbing the opposite side-knocked unabsorbed 969nm pump light.
And the second pump coupling system 12 is used for emitting the pump light output by the 940nm fiber coupling laser diode module into the Yb: YAG rod in a set size.
The second pump laser source 22 is a wavelength-locked high-brightness 940nm fiber-coupled laser diode module, and typical parameters are as follows: the output optical fiber core diameter is 105um, NA0.22, and the output power is 120W.
The polarization rotator 23 was a 1030nm45 ° quartz polarist.
The collimator lens 24 corresponds to a collimator lens of 1030nm wavelength.
The reflecting mirror 25 is a total reflection mirror and totally reflects 1030nm light.
The working principle of the compact high-gain ultrafast laser amplifier is as follows:
the laser light output by the 1030nm femtosecond seed laser source 1 is pre-amplified by the low-power pre-amplifier 17. The preamplifier 17 comprises a pulse stretcher to stretch pulses, a pulse selector to reduce the frequency of the seed laser, and a preamplifier stage to increase the power of the seed laser (1 mW-5W), so as to better realize double-pass amplification. The method is suitable for small signal extraction and subsequent high-gain amplification.
The pre-amplified laser enters a main amplification module 21 for double-pass amplification after passing through a half-wave plate 18, a PBS 19 and an optical isolator 14. A high-brightness 969nm and 940nm fiber-coupled diodes are adopted to pump Yb and YAG rods from two ends in opposite directions. The 1030nm laser passing through the main amplification module 21 passes through the 45-degree quartz rotating piece in a single pass, is collimated by the collimating lens 24, is reflected by the 1030nm total reflector to playback a large optical path, and passes through the collimating lens 24, the 45-degree quartz rotating piece and the main amplification module 21 again. The polarization state of the 1030nm laser after passing through the 45-degree quartz rotating plate in a double-pass mode (twice), is rotated by 90 degrees, and when the light beam returns to pass through the PBS 19 again, the light beam is emitted out of the light path from the direction perpendicular to the initial incident direction. The emitted amplified laser is subjected to pulse width compression by a compression grating pair.
The light path is folded through the reflection structure, and the seed laser is amplified twice through the main amplification module, so that high gain is obtained. The small signal can be amplified from 1mw to more than 20w and from 5w to more than 100 w.
In the main amplification module 21, the pumping light output by the 969nm fiber-coupled diode with high power and high brightness at the left side is subjected to beam conversion by the first pumping coupling system 4 consisting of double lenses to control the spot size of the pumping beam waist in the Yb: YAG rod. The pump light beam transformed by the first pump coupling system 4 sequentially passes through the first dichroic mirror 5 and the first dichroic mirror 7 to enter the main amplification module 21. The left side surface of the first dichroic mirror 5 is high-transmittance at 45 degrees for 969nm pump light, the right side surface is high-transmittance at 45 degrees for 969nm pump light and high-reflectance at 45 degrees for 940nm pump light, so that 940nm pump light which is not absorbed by the Yb/YAG rod on the right side is reflected out of a pump light path while the left side pump light passes as far as possible, and the 969nm pump optical fiber coupling diode on the left side is protected. The 940nm pump light reflected by the first dichroic mirror 5 is absorbed by the first absorption trap. The first dichroic mirror 7 is double-sided 969nm and 940nm pump light which is highly transparent at 45 degrees, and the right side is 1030nm laser light which is highly reflective at 45 degrees and reflects the laser light out of a pump light path. The gain medium in the main amplification module 21 is a quasi-three-level Yb: YAG crystal bar, the Yb: YAG crystal bar is welded on a gold-plated red copper micro-channel heat sink to efficiently dissipate heat, and the gold-plated red copper micro-channel heat sink is used as a cooler of the Yb: YAG crystal bar, so that the heat dissipation effect is good.
The right side of the main amplification module 21 is a pumping structure symmetrical to the left side. The pumping light output by the 940nm fiber-coupled diode with high power and high brightness at the right side is subjected to beam conversion by a second pumping coupling system 12 consisting of double lenses to control the spot size of the pumping beam waist in the Yb: YAG rod, and the pumping spot size is consistent with the size of the pumping spot at the left side. The pump beam transformed by the second pump coupling system 12 enters the main amplification module 21 through the second dichroic mirror 10 and the second dichroic mirror 9. The right side surface of the second dichroic mirror 10 is 940nm pump light with 45-degree high transmittance, the left side surface is 940nm pump light with 45-degree high transmittance and 969nm pump light with 45-degree high reflectance, so that the right 940nm pump light can pass through as far as possible, and meanwhile 969nm pump light which is not absorbed by a Yb/YAG rod on the left side is reflected out of a pump light path, and the 940nm pump optical fiber coupling diode on the right side is protected. The 969nm pump light reflected out of the optical path by the second dichroic mirror 10 is absorbed by the second absorption trap. The second dichroic mirror 9 is double-sided 969nm and 940nm pump light which is highly transparent at 45 degrees, and the left side is 1030nm laser 45-degree high reflection which reflects the laser out of a pump light path.
In the embodiment, the high-power high-brightness 940nm and 969nm fiber coupled diodes pump Yb and YAG crystal bars oppositely from two ends, not only a 1030nm femtosecond laser is adopted as seed laser, but also high-gain or high-power amplification of 1030nm seed laser in different forms such as continuous, ns and ps can be realized, and the compactness and high reliability of the laser can be still maintained.
The above description is intended to be illustrative of the preferred embodiment of the present invention and should not be taken as limiting the invention, but rather, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Claims (10)

1. A compact high-gain ultrafast laser amplifier, characterized by, including seed laser source, polarization beam splitter prism, dual wavelength double-ended pump structure and reflecting structure;
the dual-wavelength double-end pump structure comprises a first pump laser source, a first pump coupling system, a first dichroic mirror, a main amplification module, a second dichroic mirror, a second pump coupling system and a second pump laser source which are sequentially arranged; the first pump laser source and the second pump laser source are oppositely arranged;
the first pump light output by the first pump laser source is incident to the first dichroic mirror after being adjusted by the first pump coupling system, is incident to the first dichroic mirror after being transmitted by the first dichroic mirror, and is incident to the first dichroic mirror after being transmitted by the first dichroic mirror;
a second pump light output by the second pump laser source is incident to the second dichroic mirror after being adjusted by the second pump coupling system, is incident to the second dichroic mirror after being transmitted by the second dichroic mirror, and is incident to the second dichroic mirror after being transmitted by the second dichroic mirror;
the second pump light emitted from the first end of the main amplification module is transmitted by the first dichroic mirror and then reflected out of the pump light path by the first dichroic mirror;
the first pump light emitted from the second end of the main amplification module is transmitted by the second dichroic mirror and then reflected out of a pump light path by the second dichroic mirror;
after passing through the polarization beam splitter prism, the seed laser output by the seed laser source enters the first dichroic mirror, is reflected by the first dichroic mirror, then enters the first end of the main amplification module, is amplified by the main amplification module, then exits from the second end of the main amplification module, and then is reflected out of the pumping light path by the second dichroic mirror; and the second three-color mirror is reflected back by the reflecting structure, sequentially passes through the main amplifying module and the first three-color mirror, then is incident to the polarization beam splitter prism, and is emitted out of the light path from the emergent direction, wherein the emergent direction is vertical to the initial incident direction of the seed laser.
2. The compact high-gain ultrafast laser amplifier of claim 1, wherein said reflecting structure comprises a polarization rotator for changing a polarization state of the seed laser and a mirror for reflecting the seed laser exiting from the pumping optical path back to the pumping optical path.
3. The compact high-gain ultrafast laser amplifier of claim 2, wherein said reflection structure further comprises a collimating lens, and the seed laser emitted from the pumping optical path sequentially passes through said polarization rotator and said collimating lens and then enters said reflector; after being reflected by the reflector, the seed laser sequentially passes through the collimating lens and the polarization rotating sheet and then enters the second dichroic mirror, and compared with the seed laser which is emitted from the pumping light path before, the seed laser which returns to the second dichroic mirror rotates by 90 degrees in polarization state.
4. A compact high gain ultrafast laser amplifier as recited in claim 3, further comprising a preamplifier, said preamplifier including pulse stretchers and pulse selectors for pulse stretching and seed laser downconversion, respectively.
5. The compact high-gain ultrafast laser amplifier of claim 4, further comprising an optical isolator and a half-wave plate, wherein the seed laser amplified by the preamplifier is incident to the polarization splitting prism after passing through the optical isolator and the half-wave plate in sequence.
6. A compact high-gain ultrafast laser amplifier as set out in any of claims 1 to 5, wherein said dual-wavelength double-ended pump structure further comprises an absorption well for absorbing the first pump light or the second pump light which is not absorbed and which is emitted from the opposite side.
7. The compact high-gain ultrafast laser amplifier of any one of claims 1 to 5, wherein said main amplification module comprises a Yb: YAG crystal bar, said first pump laser source is a 969nm laser source, said second pump laser source is a 940nm laser source; the central wavelength of the seed laser output by the seed laser source is 1030 nm.
8. The compact high-gain ultrafast laser amplifier of claim 7, wherein a side of said first dichroic mirror facing said first pump laser source is highly transparent to light of 969nm wavelength; one side of the first dichroic mirror facing the main amplification module is highly transparent to light with a wavelength of 969nm and highly reflective to light with a wavelength of 940 nm;
one side of the second dichroic mirror facing the second pump laser source is highly transparent to light with a wavelength of 940 nm; the side of the second dichroic mirror facing the main amplification module is highly transparent to light with a wavelength of 940nm and highly reflective to light with a wavelength of 969 nm.
9. A compact high gain ultrafast laser amplifier as set out in claim 8, wherein said first dichroic mirror is highly transparent to light of 940nm and 969nm wavelengths, and a side of said first dichroic mirror facing said main amplification block is highly reflective to light of 1030nm wavelength;
the double faces of the second dichroic mirror are highly transparent to light with wavelengths of 940nm and 969nm, and the side of the second dichroic mirror facing the main amplification module is highly reflective to light with a wavelength of 1030 nm.
10. A compact high-gain ultrafast laser amplifier as set forth in any one of claims 1-5, wherein said seed laser source outputs seed laser light of any one of continuous laser, quasi-continuous laser or ultrashort pulse laser.
CN202210659725.6A 2022-06-13 2022-06-13 Compact high-gain ultrafast laser amplifier Pending CN114759424A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0517863D0 (en) * 2005-09-02 2005-10-12 Laser Quantum Ltd Laser cavity pumping configuration
CN102208742A (en) * 2011-05-06 2011-10-05 中国科学院上海光学精密机械研究所 Conductively cooled high-repetition single frequency Nd: YAG Laser
CN108039639A (en) * 2017-12-05 2018-05-15 中国科学院西安光学精密机械研究所 The how logical ultra-short pulse laser amplifier of based single crystal optical fiber polarisation control
CN113131323A (en) * 2021-03-30 2021-07-16 山东大学 Yb-YAG laser amplifier based on dual-wavelength double-end pumping structure
CN113328329A (en) * 2021-05-31 2021-08-31 山东大学 Yb-YAG laser amplifier based on dual-wavelength beam-combination single-end pumping

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0517863D0 (en) * 2005-09-02 2005-10-12 Laser Quantum Ltd Laser cavity pumping configuration
CN102208742A (en) * 2011-05-06 2011-10-05 中国科学院上海光学精密机械研究所 Conductively cooled high-repetition single frequency Nd: YAG Laser
CN108039639A (en) * 2017-12-05 2018-05-15 中国科学院西安光学精密机械研究所 The how logical ultra-short pulse laser amplifier of based single crystal optical fiber polarisation control
CN113131323A (en) * 2021-03-30 2021-07-16 山东大学 Yb-YAG laser amplifier based on dual-wavelength double-end pumping structure
CN113328329A (en) * 2021-05-31 2021-08-31 山东大学 Yb-YAG laser amplifier based on dual-wavelength beam-combination single-end pumping

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