A solid-state ultrafast laser pulse generator

Abstract

The present invention belongs to the field of laser technology, and specifically relates to a solid-state ultrafast laser pulse generator. The laser pulse generator provided by the present invention includes: a pump source for providing optical pumping energy; an energy distribution unit, which contains a plurality of acousto-optic modulators, and the plurality of acousto-optic modulators form a beam distribution structure with an input end and a plurality of output ends through a connection method selected from series, parallel, and a combination of series and parallel; a plurality of resonant units, each of which receives energy from an output end of the energy distribution unit, and each resonant unit includes a reflector, a cavity mirror, a first optical path adjustment unit, a gain medium, a second optical path adjustment unit, and a semiconductor saturable absorption mirror arranged in sequence on the optical path, and a resonant cavity is formed between the cavity mirror and the semiconductor saturable absorption mirror to generate laser pulses. The laser pulse generator of the present invention has significant advantages in multi-task processing, dynamic control of power and frequency, and wavelength diversity.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and in particular relates to a solid-state ultrafast laser pulse generator. Background Art

[0002] Ultrafast lasers generally refer to lasers with pulse widths of picoseconds or smaller. Currently, commercial ultrafast lasers are mainly achieved through the use of commercial semiconductor saturable absorbers (SESAM) for passive mode locking.

[0003] In the prior art, patent CN113178768B uses the method of cutting the optical fiber in the cavity and re-melting it to achieve the change of cavity length, thereby achieving the purpose of accurate frequency adjustment. This solution solves the frequency adjustment problem of fiber ultrafast laser. Patent CN111490439B adjusts the amplified and broadened laser pulse through a pulse modulation module to achieve the purpose of frequency adjustment, but the scheme of frequency selection outside the cavity can only be adjusted to 1 / N of the original frequency. Patent CN106911060B uses an acousto-optic modulator (AOM) in the fiber resonant cavity to obtain a nanosecond pulse laser, and then uses an optical parametric oscillator (OPO) to achieve wavelength adjustment. This adjustment uses frequency conversion technology. The nanosecond pulse laser enters the OPO crystal to obtain two beams of light that meet phase matching, but this scheme cannot adjust the pulse frequency of the laser. Patent CN115498505B proposes a solution to achieve wavelength adjustment using temperature adjustment. This solution cannot adjust the wavelength over a large range, nor can it adjust the pulse frequency. Patent CN116960720A proposes a method for adjusting the pulse width and repetition frequency of a picosecond pulse laser. The method uses an all-fiber structure and uses a coupler to divide the signal light into two paths. The two paths of light achieve the change of repetition frequency by changing the length of the passive optical fiber, and the change of the pulse width by changing the grating of the two paths. The two paths cannot be output at the same time, and the output laser wavelength cannot be adjusted. Patent CN108631147A proposes a method for synchronously adjusting wavelength and frequency in a passive mode-locked laser. The method achieves synchronous tuning of the laser wavelength by changing the coupling angle of the optical fiber and the semiconductor saturable absorber. The essence of this method is to change the optical path in the laser resonant cavity to achieve frequency adjustment and wavelength tuning near the center wavelength, and its frequency and wavelength range is limited. This method is more effective in the short cavity or ultra-short cavity of the passive mode-locked fiber laser. However, since the solid-state lasers commonly used in industry generally have a longer cavity length, this method is usually not applicable to solid-state lasers commonly used in industry. Patent CN102820612A proposes a method for adjusting the repetition frequency of an ultrashort pulse solid-state laser by adjusting the angle of a parallel lens group in a resonant cavity. This method uses a resonant cavity and essentially changes the optical path in the resonant cavity. It has a single-path output and cannot adjust the wavelength. Patent CN101388521B and Patent CN102013622A use a split pump light method to coat the surface of the crystal to achieve dual-path single longitudinal mode output, and the dual-path single longitudinal mode has different wavelengths. This method achieves the adjustment of the wavelength of a continuous single-mode laser. Patent CN111987576A uses a method of inserting a triangular prism in a resonant cavity to achieve the purpose of changing the optical path and thus achieving frequency adjustment. This method can only achieve frequency adjustment at a fixed frequency point, and the adjustment range is not large.Patent CN108306167A addresses the problem of short service life of ultrashort pulse laser SESAM and proposes a method of adding an optical fiber online AOM in the cavity, which realizes the switching of the optical path in the laser resonant cavity and prolongs the service life of the ultrashort pulse laser resonant cavity by replacing the SESAM. The laser completed by this method is essentially a resonant cavity, which can only output a single-channel laser with a fixed frequency and a fixed wavelength at the same time, and cannot output multiple lasers with different frequencies and wavelengths at the same time.

[0004] In summary, existing technologies have their own limitations in wavelength and frequency regulation and control. If a more comprehensive solution can be provided to achieve a wider range of frequency and wavelength regulation capabilities, it will have important practical significance. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides a solid-state ultrafast laser pulse generator, which improves the laser pulse generator in terms of multi-task processing, dynamic control of power and frequency, and wavelength diversity.

[0006] The solid-state ultrafast laser pulse generator provided by the present invention comprises a pump source, an energy distribution unit and a plurality of resonance units. The energy distribution unit receives energy from the pump source and distributes it to different resonance units to generate a plurality of independent laser pulses.

[0007] Furthermore, the above-mentioned solid-state ultrafast laser pulse generator comprises:

[0008] A pump source, which is used to provide optical pumping energy;

[0009] An energy distribution unit, the energy distribution unit comprises a plurality of acousto-optic modulators, the plurality of acousto-optic modulators are connected in series, in parallel, or in combination of series and parallel to form a beam distribution structure having one input end and a plurality of output ends; the energy distribution unit adjusts the output power of each output end by adjusting the energy distribution ratio of the acousto-optic modulator;

[0010] A plurality of resonance units, each of which receives energy from an output end of an energy distribution unit, each of which comprises a reflector, a cavity mirror, a first optical path adjustment unit, a gain medium, a second optical path adjustment unit, and a semiconductor saturable absorber mirror, which are sequentially arranged on an optical path, and a resonance cavity is formed between the cavity mirror and the semiconductor saturable absorber mirror to generate laser pulses; the resonance unit adjusts the laser pulse frequency by changing the optical paths of the first optical path adjustment unit and the second optical path adjustment unit.

[0011] Furthermore, as a further optimization solution for the solid-state ultrafast laser pulse generator, the pump source is a strong light optical pump, preferably selected from solid-state lasers, fiber lasers, and fiber-coupled semiconductor lasers.

[0012] Furthermore, as a further optimization scheme for the solid-state ultrafast laser pulse generator, the acousto-optic modulator used in the energy distribution unit includes: an acousto-optic crystal, a piezoelectric ceramic element connected to one side of the acousto-optic crystal, and a driving circuit for powering the piezoelectric ceramic element; the acousto-optic crystal is a crystal material with an acousto-optic effect, selected from lead molybdate, dilead molybdate, tellurium dioxide, quartz, etc.; the driving circuit is connected to the piezoelectric ceramic element to drive the piezoelectric ceramic element with a radio frequency signal with a preset frequency and amplitude; the piezoelectric ceramic element receives an electrical signal and converts it into an ultrasonic wave, which is then applied to the acousto-optic crystal; after receiving the signal, the acousto-optic crystal forms a refractive index change inside, thereby changing the propagation direction of the light to produce diffraction, thereby achieving light splitting.

[0013] Furthermore, as a further optimization solution for the solid-state ultrafast laser pulse generator, the energy distribution unit is configured with a host computer control system, which is electrically connected to each acousto-optic modulator in the energy distribution unit and sends an electrical control signal to each acousto-optic modulator to adjust the energy distribution ratio of the current acousto-optic modulator.

[0014] Furthermore, as a further optimization scheme for the solid-state ultrafast laser pulse generator, the energy distribution unit is composed of three acousto-optic modulators, namely the first acousto-optic modulator, the second acousto-optic modulator, and the third acousto-optic modulator; the two output ends of the first acousto-optic modulator are respectively connected to the input end of the second acousto-optic modulator and the input end of the third acousto-optic modulator, forming an energy distribution unit with one input end and four output ends; the beam power of the input end is I1, the beam powers of the four output ends are O1, O2, O3, and O4 respectively, and the energy distribution ratios of the first acousto-optic modulator, the second acousto-optic modulator, and the third acousto-optic modulator are K1, K2, and K3 respectively; the host computer control system controls K1, K2, and K3 respectively as follows:

[0015] K1=((O1+O2) / (O1+O2+O3+O4)) : ((O3+O4) / (O1+O2+O3+O4));

[0016] K2= (O1 / (O1+O2+O3+O4)) : (O2 / (O1+O2+O3+O4));

[0017] K3= (O3 / (O1+O2+O3+O4)) : (O4 / (O1+O2+O3+O4)).

[0018] Furthermore, as another optimization scheme for the solid-state ultrafast laser pulse generator, the energy distribution unit is composed of seven AOMs, namely, a first AOM, a second AOM, a third AOM, a fourth AOM, a fifth AOM, a sixth AOM, and a seventh AOM; the two output ends of the first AOM are respectively connected to the input end of the second AOM and the input end of the third AOM, the two output ends of the second AOM are respectively connected to the input end of the fourth AOM and the input end of the fifth AOM, the two output ends of the third AOM are respectively connected to the input end of the sixth AOM, and the second output ends of the second AOM are respectively connected to the input end of the fourth AOM and the input end of the fifth AOM, and the two output ends of the third AOM are respectively connected to the input end of the sixth AOM. The input end of the first acousto-optic modulator and the input end of the seventh acousto-optic modulator form an energy distribution unit with one input end and eight output ends; the beam power of the input end is I1, the beam powers of the eight output ends are O1, O2, O3, O4, O5, O6, O7, O8 in sequence, and the energy distribution ratios of the first acousto-optic modulator, the second acousto-optic modulator, the third acousto-optic modulator, the fourth acousto-optic modulator, the fifth acousto-optic modulator, the sixth acousto-optic modulator, and the seventh acousto-optic modulator are K1, K2, K3, K4, K5, K6, and K7 respectively; the host computer control system controls K1, K2, K3, K4, K5, K6, and K7 respectively as follows:

[0019] K1=((O1+O2+O3+O4) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O5+O6+O7+O8) / (O1+O2+O3+O4+O5+O6+O7+O8));

[0020] K2=((O1+O2) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O3+O4) / (O1+O2+O3+O4+O5+O6+O7+O8));

[0021] K3=((O5+O6) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O7+O8) / (O1+O2+O3+O4+O5+O6+O7+O8));

[0022] K4=(O1 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O2 / (O1+O2+O3+O4+O5+O6+O7+O8));

[0023] K5=(O3 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O4 / (O1+O2+O3+O4+O5+O6+O7+O8));

[0024] K6=(O5 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O6 / (O1+O2+O3+O4+O5+O6+O7+O8));

[0025] K7=(O7 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O8 / (O1+O2+O3+O4+O5+O6+O7+O8)).

[0026] Further, as another optimization scheme for the solid-state ultrafast laser pulse generator, the energy distribution unit is composed of four acousto-optic modulators, namely the first acousto-optic modulator, the second acousto-optic modulator, the third acousto-optic modulator, and the fourth acousto-optic modulator; one output end of the first acousto-optic modulator is directly used as an output end of the energy distribution unit, the other output end of the first acousto-optic modulator is connected to the input end of the second acousto-optic modulator, and the two output ends of the second acousto-optic modulator are respectively connected to the input end of the third acousto-optic modulator and the input end of the fourth acousto-optic modulator, so as to form an energy distribution unit with one input end and five output ends; the beam power of the input end is I1, and the beam powers of the five output ends are O1, O2, O3, O4, and O5 respectively. The energy distribution ratios of the first acousto-optic modulator, the second acousto-optic modulator, the third acousto-optic modulator, and the fourth acousto-optic modulator are K1, K2, K3, and K4 respectively, and the host computer control system controls K1, K2, K3, and K4 respectively as follows:

[0027] K1=(O1 / (O1+O2+O3+O4+O5)):((O2+O3+O4+O5) / (O1+O2+O3+O4+O5))

[0028] K2=((O2+O3) / (O1+O2+O3+O4+O5)):((O4+O5) / (O1+O2+O3+O4+O5))

[0029] K3=(O2 / (O1+O2+O3+O4+O5)):(O3 / (O1+O2+O3+O4+O5))

[0030] K4=(O4 / (O1+O2+O3+O4+O5)):(O5 / (O1+O2+O3+O4+O5)).

[0031] Furthermore, as a further optimization scheme for the solid-state ultrafast laser pulse generator, the first optical path adjustment unit and the second optical path adjustment unit each have at least one pair of lenses with adjustable distance, and the optical path size is changed by changing the distance between the lenses; the first optical path adjustment unit and the second optical path adjustment unit synchronously increase or decrease the optical path to adjust the pulse frequency of the laser output by the resonance unit.

[0032] Furthermore, as a further optimization scheme for the solid-state ultrafast laser pulse generator, in each resonant unit, the surface of the cavity mirror and the surface of the reflector layer of the semiconductor saturable absorber mirror are coated with a coating; according to the required wavelength of the laser pulse, the coating is formulated as a coating material that allows a light beam of the required wavelength to pass through, so that only the light beam of the required wavelength is effectively reflected in the resonant cavity.

[0033] Furthermore, as a further optimization scheme for the solid-state ultrafast laser pulse generator, a spot shaping unit is connected between the output end of the pump source and the input end of the energy distribution unit. The spot shaping unit has a lens group that shapes the light beam of the pump source into a spot of a preset shape and size and transmits it to the energy distribution unit.

[0034] Beneficial Effects

[0035] The laser pulse generator of the present invention has significant advantages in multi-task processing, dynamic control of power and frequency, and wavelength diversity, specifically including the following aspects.

[0036] Capable of multi-channel laser pulse output: The above-mentioned laser pulse generator can simultaneously generate multiple independent laser pulses as output. Each laser can also be used as a seed source and further amplified by a solid-state laser amplifier, which greatly expands the application range of the laser pulse generator. It is particularly suitable for complex experiments or industrial applications that require multiple laser beams to operate simultaneously or switch quickly.

[0037] Flexible power adjustment function: the power of each laser can be adjusted independently according to the needs of the actual application scenario, achieving high flexibility in power distribution. The host computer can also accurately control each acousto-optic modulator in the energy distribution unit to adjust the power of each output laser in real time and efficiently.

[0038] With instant adjustment function of pulse frequency: the above laser pulse generator allows the user to dynamically adjust the optical path of the resonant cavity, thereby instantly changing the pulse frequency of the output laser, and each output laser pulse can be adjusted independently.

[0039] Customization capability with different wavelengths: Each resonant unit can not only independently adjust the power and frequency, but also customize the wavelength of the output laser pulse by selecting different types of gain media and coatings on cavity mirrors and semiconductor saturable absorber mirrors to meet users' diverse and personalized configuration needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the structure of a laser pulse generator with three acousto-optic modulators.

[0041] Figure 2 Schematic diagram of the structure of a laser pulse generator with seven acousto-optic modulators.

[0042] Figure 3 Schematic diagram of the structure of a laser pulse generator with four acousto-optic modulators.

[0043] Figure 4 It is a structural schematic diagram of a laser pulse generator with a host computer.

[0044] Figure 5 Schematic diagram of the structure of the resonance unit.

[0045] Figures 6 to 9 This is the measured wavelength diagram of the four-way output laser.

[0046] Figures 10 to 13 This is the measured frequency diagram of the four-channel output laser.

[0047] Figures 14 to 17 This is the measured pulse width of the four-channel output laser. DETAILED DESCRIPTION

[0048] The present invention is further illustrated by specific examples below. These examples are exemplary and are intended to illustrate the problem and explain the present invention, but are not intended to be limiting.

[0049] like Figure 1 The solid-state ultrafast laser pulse generator shown includes a pump source 1, a spot shaping unit 2, an energy distribution unit 3, and a resonance unit 4. The pump source 1 adopts optical pumping, and the emitted light is shaped by the spot shaping unit 2 and then distributed by the energy distribution unit 3 to different resonance units 4 to generate different laser pulses.

[0050] The pump source 1 is used as an energy source to excite particles in the laser medium to a high energy level, thereby achieving a population inversion and providing the basic conditions for generating lasers. The pump source 1 uses optical pumping, such as a strong light source such as a solid-state laser, a fiber laser, or a fiber-coupled semiconductor laser.

[0051] The light spot shaping unit 2 is used to optimize the beam quality so that the light beam of the pump source 1 enters the energy distribution unit 3 uniformly. The light spot shaping unit 2 includes a group of lenses, such as a plano-convex lens group, a doublet lens group, etc., and by adjusting the distribution of the lenses, the focusing or diverging state of the light beam is changed, and the size and shape of the light beam are adjusted at the same time, and the light spot is shaped into a uniformly distributed circle of a preset size before entering the energy distribution unit 3.

[0052] In addition, a stop or light shield may be placed in the lens group of the light spot shaping unit 2 as needed to cut and remove the uneven part of the edge of the light beam, and at the same time limit the size of the light spot and improve the uniformity of the light intensity in the central area. A beam homogenizer, such as a micro-optical element array, may also be placed in the lens group of the light spot shaping unit 2 as needed to convert the uneven light spot into a uniformly distributed light field.

[0053] The energy distribution unit 3 includes a plurality of acousto-optic modulators, which are connected in series, in parallel or in combination to form a beam structure having an input end and multiple output ends. The input end receives the light beam from the light spot shaping unit 2, and distributes the light beam to different resonance units 4 according to the required energy ratio through multiple output ends.

[0054] An acousto-optic modulator (AOM) is a device that uses the interaction between sound waves and light waves to control the characteristics of a light beam. It is mainly composed of crystal materials, transducers, and drive circuits. Among them, the crystal material is an acousto-optic crystal, which is the core component of the acousto-optic modulator. For example, lead molybdate, dilead molybdate, tellurium dioxide, quartz, etc. are used. These crystals have good acousto-optic effects, that is, they can effectively convert sound waves into changes in the phase or direction of light waves. The transducer is installed on one side of the crystal material and can be a piezoelectric ceramic element. It converts electrical signals into mechanical vibrations, thereby generating ultrasonic waves that propagate in the crystal. The drive circuit provides a radio frequency (RF) signal source to the transducer. Its frequency determines the frequency of the sound wave, and the amplitude of the signal controls the intensity of the sound wave, which in turn affects the modulation depth of the light beam.

[0055] When working, the driving circuit of the acousto-optic modulator applies a radio frequency voltage of a preset frequency to the transducer, and the transducer generates a corresponding ultrasonic wave and propagates in the acousto-optic crystal. When the incident laser and the sound wave meet inside the crystal, if the two meet the Bragg condition (that is, the wavelength of the sound wave matches the wavelength of the light wave, and the angle between the two meets the relationship required for diffraction), the laser will be diffracted to produce a diffracted beam. That is, the acousto-optic modulator uses the sound waves in the crystal to create a diffraction grating, and as the power of the applied radio frequency signal changes, the diffracted light also changes proportionally. As a result, the modulator can be used like a shutter cycle, or as a variable attenuator (dynamically controlling the intensity of the transmitted light), splitting the light beam, and adjusting a beam of light to be divided into two beams of light with different power ratios according to demand.

[0056] like Figure 1 As shown, in some embodiments, the energy distribution unit 3 is composed of three AOMs, namely, a first AOM 31, a second AOM 32, and a third AOM 33. The two output ends of the first AOM 31 are respectively connected to the input end of the second AOM 32 and the input end of the third AOM 33, forming an energy distribution unit 3 with one input end and four output ends.

[0057] Assume that the beam power at the input end is I1, the beam powers at the four output ends are O1, O2, O3, and O4 respectively, and the energy distribution ratios of the first AOM 31, the second AOM 32, and the third AOM 33 are K1, K2, and K3 respectively, then:

[0058] K1=((O1+O2) / (O1+O2+O3+O4)) : ((O3+O4) / (O1+O2+O3+O4))

[0059] K2= (O1 / (O1+O2+O3+O4)) : (O2 / (O1+O2+O3+O4))

[0060] K3= (O3 / (O1+O2+O3+O4)) : (O4 / (O1+O2+O3+O4))

[0061] I1=O1+O2+O3+O4

[0062] Therefore, the demand for no more than four light beams output in any energy distribution state can be achieved by adjusting the energy distribution ratios K1, K2, K3 of the first AOM 31, the second AOM 32, and the third AOM 33 and the input beam power I1.

[0063] like Figure 2 As shown, in some other embodiments, the energy distribution unit 3 may be composed of seven AOMs, namely, the first AOM 31, the second AOM 32, the third AOM 33, the fourth AOM 34, the fifth AOM 35, the sixth AOM 36, and the seventh AOM 37. The two output ends of the first AOM 31 are respectively connected to the input end of the second AOM 32 and the input end of the third AOM 33, the two output ends of the second AOM 32 are respectively connected to the input end of the fourth AOM 34 and the input end of the fifth AOM 35, and the two output ends of the third AOM 33 are respectively connected to the input end of the sixth AOM 36 and the input end of the seventh AOM 37, forming an energy distribution unit 3 with one input end and eight output ends.

[0064] Assume that the beam power at the input end is I1, the beam powers at the eight output ends are O1, O2, O3, O4, O5, O6, O7, and O8 respectively, and the energy distribution ratios of the first AOM 31, the second AOM 32, the third AOM 33, the fourth AOM 34, the fifth AOM 35, the sixth AOM 36, and the seventh AOM 37 are K1, K2, K3, K4, K5, K6, and K7 respectively, then:

[0065] K1=((O1+O2+O3+O4) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O5+O6+O7+O8) / (O1+O2+O3+O4+O5+O6+O7+O8))

[0066] K2=((O1+O2) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O3+O4) / (O1+O2+O3+O4+O5+O6+O7+O8))

[0067] K3=((O5+O6) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O7+O8) / (O1+O2+O3+O4+O5+O6+O7+O8))

[0068] K4=(O1 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O2 / (O1+O2+O3+O4+O5+O6+O7+O8))

[0069] K5=(O3 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O4 / (O1+O2+O3+O4+O5+O6+O7+O8))

[0070] K6=(O5 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O6 / (O1+O2+O3+O4+O5+O6+O7+O8))

[0071] K7=(O7 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O8 / (O1+O2+O3+O4+O5+O6+O7+O8))

[0072] I1=O1+O2+O3+O4+O5+O6+O7+O8

[0073] Therefore, the demand for no more than eight light beams output in any energy distribution state can be achieved by adjusting the energy distribution ratios K1, K2, K3, K4, K5, K6, K7 of the first AOM 31, the second AOM 32, the third AOM 33, the fourth AOM 34, the fifth AOM 35, the sixth AOM 36, and the seventh AOM 37 and the input beam power I1.

[0074] In some other embodiments, different output ends of the energy distribution unit 3 may pass through different levels of acousto-optic modulators. Figure 3As shown, the energy distribution unit 3 may be composed of four AOMs, namely, a first AOM 31, a second AOM 32, a third AOM 33, and a fourth AOM 34. Among them, one output end of the first AOM 31 is directly used as an output end of the energy distribution unit 3, the other output end of the first AOM 31 is connected to the input end of the second AOM 32, and the two output ends of the second AOM 32 are respectively connected to the input end of the third AOM 33 and the input end of the fourth AOM 34, forming an energy distribution unit 3 with one input end and five output ends.

[0075] Assume that the beam power at the input end is I1, the beam powers at the five output ends are O1, O2, O3, O4, and O5 respectively, and the energy distribution ratios of the first AOM 31, the second AOM 32, the third AOM 33, and the fourth AOM 34 are K1, K2, K3, and K4 respectively, then:

[0076] K1=(O1 / (O1+O2+O3+O4+O5)):((O2+O3+O4+O5) / (O1+O2+O3+O4+O5))

[0077] K2=((O2+O3) / (O1+O2+O3+O4+O5)):((O4+O5) / (O1+O2+O3+O4+O5))

[0078] K3=(O2 / (O1+O2+O3+O4+O5)):(O3 / (O1+O2+O3+O4+O5))

[0079] K4=(O4 / (O1+O2+O3+O4+O5)):(O5 / (O1+O2+O3+O4+O5))

[0080] I1=O1+O2+O3+O4+O5

[0081] Therefore, the demand for no more than five light beams output in any energy distribution state can be achieved by adjusting the energy distribution ratios K1, K2, K3, K4 of the first AOM 31, the second AOM 32, the third AOM 33, and the fourth AOM 34 and the input beam power I1.

[0082] Among them, since the power of the beam at the first output end is O1, and it is directly output after only one-stage AOM distribution, compared with other beams that have undergone multi-stage modulation, it has experienced the least optical path intervention, resulting in lower optical energy loss and less optical distortion, and is easy to maintain high optical power and good beam quality. The power of the beams at the other four output ends is O2, O3, O4, and O5. After being distributed by a multi-stage AOM, it is more suitable for use with low power requirements than the former. At the same time, the distribution of the multi-stage AOM also allows for more sophisticated energy distribution control. Therefore, according to the number of adjustment levels experienced by the output beam, a reasonable balance and selection can be flexibly made between the number of beams, power distribution, and beam quality to meet more diverse usage needs.

[0083] In some other embodiments, a host computer 5 may be set to control the energy distribution unit 3, and send corresponding adjustment signals to the acousto-optic modulators according to the energy distribution ratio required by each acousto-optic modulator, so as to achieve unified regulation of all acousto-optic modulators in the distribution unit 3, thereby adjusting the power of each output end and improving the accuracy and execution efficiency of regulation. In particular, when a large number of acousto-optic modulators are involved in the energy distribution unit 3, setting the host computer 5 for automatic control will significantly improve the execution efficiency and accuracy.

[0084] Each output end of the energy distribution unit 3 is connected to a corresponding resonance unit 4. Figure 5 As shown, the resonance unit 4 includes a reflector 41, a cavity mirror 42, a first optical path adjustment unit 43, a gain medium 44, a second optical path adjustment unit 45, and a semiconductor saturable absorption mirror 46 which are sequentially arranged on the optical path.

[0085] Among them, a resonant cavity is formed between the cavity mirror 42 and the semiconductor saturable absorber mirror 46 for light to oscillate and reflect inside; the gain medium 44 receives the energy of the pump source 1 to form excitation and photon release, and repeatedly oscillates and amplifies in the resonant cavity; the first optical path adjustment unit 43 and the second optical path adjustment unit 45 are used to adjust the optical path of the resonant cavity to adjust the frequency of the generated laser pulse, and the reflector 41 introduces the light energy of the pump source 1 into the resonant cavity and then also guides the laser pulse generated by the resonant cavity out.

[0086] The semiconductor saturable absorber mirror 46, SESAM, is located at the end of the resonator unit 4 and consists of a saturable absorber (SA) layer and a reflector layer. The reflector layer is used to reflect light passing through the saturable absorber layer, which is a thin layer of semiconductor material located on the reflector. The absorption capacity of the saturable absorber layer decreases with the increase of the incident light intensity until it reaches the saturation point. When the laser circulates in the cavity and passes through the SA layer, the initial weak light is strongly absorbed, causing the carriers (electrons or holes) in the SA layer to be excited to a higher energy level, and this process accumulates energy. As the light intensity increases, more and more carriers reach saturation and the absorption capacity decreases. At this time, the SA layer almost no longer absorbs additional light, but allows the remaining strong light to pass through and return to the resonant cavity. Only when the light intensity is high enough to exceed the saturation threshold of the SA can the light pass through effectively and form a pulse, so this rapid transition from high absorption to low absorption forms a "switching effect" that can induce a stable ultrashort pulse output in the cavity. That is to say, the saturable absorber absorbs and accumulates energy in weak light conditions, while in strong light conditions, the optical loss decreases, the transmittance increases, and reaches a "saturated" state, and the semiconductor saturable absorber instantly releases the absorbed energy. This saturated absorption characteristic can be used to generate ultra-short pulse outputs of picoseconds or even femtoseconds.

[0087] The gain medium 44 is a key component for converting the energy provided by the pump source 1 into laser radiation, and can be a doped crystal, glass or optical fiber, such as ytterbium-doped yttrium aluminum garnet (Nd:YAG), neodymium-doped yttrium aluminum garnet (Nd:YAG), erbium-doped yttrium vanadate (Er:YVO4), titanium sapphire (Cr:Ti:Sapphire), thulium-doped yttrium aluminate (Tm:YAP), ytterbium-doped, erbium-doped or thulium-doped optical fiber, single crystal optical fiber or photonic crystal optical fiber, etc. The gain medium 44 is excited by the energy of the pump source 1, and the internal atoms transition from the low-energy ground state to the high-energy excited state, and the atoms in the excited state release photons when returning to the lower energy level through spontaneous emission or stimulated emission. The photons in the resonant cavity collide with the excited atoms, causing the atoms to release new photons with the same frequency, phase, and direction as the original photons. After repeated oscillations of the resonant cavity, the number of photons increases exponentially, forming laser pulses.

[0088] The first optical path adjustment unit 43 and the second optical path adjustment unit 45 are respectively arranged at both ends of the gain medium 44 to synchronously adjust the optical path. Each optical path adjustment unit includes a pair of lenses with adjustable distance, and the distance between the lenses is adjusted to increase or decrease the optical path, thereby adjusting the pulse frequency of the output laser.

[0089] Since the light repeatedly oscillates in the resonant cavity between the cavity mirror 42 and the semiconductor saturable absorber mirror 46, a specific wavelength of light is allowed to be reflected by coating the surface of the cavity mirror 42 and the surface of the reflector layer of the semiconductor saturable absorber mirror 46, thereby changing the wavelength of the output laser pulse. The laser pulse generator has a plurality of resonant units 4, and different resonant units 4 can be conveniently selected or customized to output different laser wavelengths according to the needs of the user, which greatly broadens the application flexibility of laser technology and meets the use requirements of increasingly diversified laser sources in scientific research and industry.

[0090] The above-mentioned laser pulse generator has significant advantages in multi-tasking, dynamic control of power and frequency, and wavelength diversity, specifically including the following aspects.

[0091] Capable of multi-channel laser pulse output: The above-mentioned laser pulse generator can simultaneously generate multiple independent laser pulses as output. Each laser can also be used as a seed source and further amplified by a solid-state laser amplifier, which greatly expands the application range of the laser pulse generator. It is particularly suitable for complex experiments or industrial applications that require multiple laser beams to operate simultaneously or switch quickly.

[0092] It has a flexible power adjustment function: the power of each laser can be independently adjusted according to the needs of the actual application scenario, achieving high flexibility in power distribution; the upper computer 5 can also accurately control each acousto-optic modulator in the energy distribution unit 3 to adjust the power of each output laser in real time and efficiently.

[0093] With instant adjustment function of pulse frequency: the above laser pulse generator allows the user to dynamically adjust the optical path of the resonant cavity, thereby instantly changing the pulse frequency of the output laser, and each output laser pulse can be adjusted independently.

[0094] Customization capability with different wavelengths: Each resonant unit 4 can not only independently adjust the power and frequency, but also customize the wavelength of the output laser pulse by selecting different types of gain media 44 and coatings on the cavity mirror 42 and the semiconductor saturable absorber mirror 46 to meet the user's diverse and personalized configuration needs.

[0095] according to Figure 1 The optical path shown uses ytterbium-doped single crystal fiber to achieve four outputs of different frequencies and wavelengths, where the central wavelengths are 1028.9nm, 1047.1nm, 1053.0nm, and 1064.1nm, respectively. The corresponding frequencies are 39.8MHz, 80MHz, 82MHz, and 120MHz, respectively. The corresponding pulse widths are 10.7ps, 23.6ps, 12.0ps, and 11.2ps under Gaussian fitting. The wavelengths are as follows: Figures 6 to 9 As shown, the frequency Figures 10 to 13As shown, the pulse width is Figures 14 to 17 shown.

[0096] The above embodiments are exemplary, and their purpose is to illustrate the technical concept and features of the present invention so that people familiar with the technology in this field can understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser pulse generator, characterized in that: include: A pump source, the pump source is used to provide optical pumping energy; An energy distribution unit, wherein the energy distribution unit comprises a plurality of acousto-optic modulators, wherein the plurality of acousto-optic modulators are connected in series, in parallel, or in combination of series and parallel to form a beam distribution structure having an input end and a plurality of output ends; the energy distribution unit adjusts the output power of each output end by adjusting the energy distribution ratio of the acousto-optic modulator; A plurality of resonant units, each of which receives energy from an output end of an energy distribution unit to generate an independent laser pulse; each resonant unit comprises a reflector, a cavity mirror, a first optical path adjustment unit, a gain medium, a second optical path adjustment unit, and a semiconductor saturable absorption mirror arranged in sequence on an optical path, and a resonant cavity is formed between the cavity mirror and the semiconductor saturable absorption mirror to generate a laser pulse; The resonance unit adjusts the laser pulse frequency by changing the optical path of the first optical path adjustment unit and the second optical path adjustment unit; The acousto-optic modulator used in the energy distribution unit includes: an acousto-optic crystal, a piezoelectric ceramic element connected to one side of the acousto-optic crystal, and a driving circuit for supplying power to the piezoelectric ceramic element; The acousto-optic crystal is a crystal material with acousto-optic effect, selected from lead molybdate, dilead molybdate, tellurium dioxide, and quartz; the driving circuit is connected to the piezoelectric ceramic element, and drives the piezoelectric ceramic element with a radio frequency signal with a preset frequency and amplitude; the piezoelectric ceramic element receives an electrical signal and converts it into an ultrasonic wave, which is then applied to the acousto-optic crystal; after receiving the signal, the acousto-optic crystal forms a refractive index change inside, thereby changing the propagation direction of light to produce diffraction and realize light splitting.

2. The laser pulse generator according to claim 1, characterized in that: The pump source is a strong light optical pump selected from a solid laser, a fiber laser, and a fiber-coupled semiconductor laser.

3. The laser pulse generator according to claim 1, characterized in that: The energy distribution unit is equipped with a host computer control system, which is electrically connected to each acousto-optic modulator in the energy distribution unit and sends an electrical control signal to each acousto-optic modulator to adjust the energy distribution ratio of the current acousto-optic modulator.

4. The laser pulse generator according to claim 3, characterized in that: The energy distribution unit is composed of three acousto-optic modulators, namely a first acousto-optic modulator, a second acousto-optic modulator, and a third acousto-optic modulator; two output ends of the first acousto-optic modulator are respectively connected to the input end of the second acousto-optic modulator and the input end of the third acousto-optic modulator, forming an energy distribution unit with one input end and four output ends; The beam power at the input end is I1, the beam powers at the four output ends are O1, O2, O3, and O4 respectively, and the energy distribution ratios of the first acousto-optic modulator, the second acousto-optic modulator, and the third acousto-optic modulator are K1, K2, and K3 respectively; the host computer control system controls K1, K2, and K3 respectively as follows: K1=((O1+O2) / (O1+O2+O3+O4)) : ((O3+O4) / (O1+O2+O3+O4)); K2= (O1 / (O1+O2+O3+O4)) : (O2 / (O1+O2+O3+O4)); K3= (O3 / (O1+O2+O3+O4)) : (O4 / (O1+O2+O3+O4)).

5. The laser pulse generator according to claim 3, characterized in that: The energy distribution unit is composed of seven acousto-optic modulators, namely a first acousto-optic modulator, a second acousto-optic modulator, a third acousto-optic modulator, a fourth acousto-optic modulator, a fifth acousto-optic modulator, a sixth acousto-optic modulator, and a seventh acousto-optic modulator; The two output ends of the first AOM are connected to the input end of the second AOM and the input end of the third AOM respectively, the two output ends of the second AOM are connected to the input end of the fourth AOM and the input end of the fifth AOM respectively, and the two output ends of the third AOM are connected to the input end of the sixth AOM and the input end of the seventh AOM respectively, so as to form an energy distribution unit with one input end and eight output ends; the beam power of the input end is I1, and the beam powers of the eight output ends are O1, O2, O3, O4, O5, O6, O7, O8 respectively, and the energy distribution ratios of the first AOM, the second AOM, the third AOM, the fourth AOM, the fifth AOM, the sixth AOM, and the seventh AOM are K1, K2, K3, K4, K5, K6, and K7 respectively; the host computer control system controls K1, K2, K3, K4, K5, K6, and K7 respectively as follows: K1=((O1+O2+O3+O4) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O5+O6+O7+O8) / (O1+O2+O3+O4+O5+O6+O7+O8)); K2=((O1+O2) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O3+O4) / (O1+O2+O3+O4+O5+O6+O7+O8)); K3=((O5+O6) / (O1+O2+O3+O4+O5+O6+O7+O8)):((O7+O8) / (O1+O2+O3+O4+O5+O6+O7+O8)); K4=(O1 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O2 / (O1+O2+O3+O4+O5+O6+O7+O8)); K5=(O3 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O4 / (O1+O2+O3+O4+O5+O6+O7+O8)); K6=(O5 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O6 / (O1+O2+O3+O4+O5+O6+O7+O8)); K7=(O7 / (O1+O2+O3+O4+O5+O6+O7+O8)):(O8 / (O1+O2+O3+O4+O5+O6+O7+O8)).

6. The laser pulse generator according to claim 3, characterized in that: The energy distribution unit is composed of four acousto-optic modulators, namely a first acousto-optic modulator, a second acousto-optic modulator, a third acousto-optic modulator, and a fourth acousto-optic modulator; One output end of the first acousto-optic modulator is directly used as an output end of the energy distribution unit, the other output end of the first acousto-optic modulator is connected to the input end of the second acousto-optic modulator, and the two output ends of the second acousto-optic modulator are respectively connected to the input end of the third acousto-optic modulator and the input end of the fourth acousto-optic modulator, so as to form an energy distribution unit with one input end and five output ends; the beam power of the input end is I1, and the beam powers of the five output ends are O1, O2, O3, O4, and O5 respectively. The energy distribution ratios of the first acousto-optic modulator, the second acousto-optic modulator, the third acousto-optic modulator, and the fourth acousto-optic modulator are K1, K2, K3, and K4 respectively, and the host computer control system controls K1, K2, K3, and K4 respectively as follows: K1=(O1 / (O1+O2+O3+O4+O5)):((O2+O3+O4+O5) / (O1+O2+O3+O4+O5)) K2=((O2+O3) / (O1+O2+O3+O4+O5)):((O4+O5) / (O1+O2+O3+O4+O5)) K3=(O2 / (O1+O2+O3+O4+O5)):(O3 / (O1+O2+O3+O4+O5)) K4=(O4 / (O1+O2+O3+O4+O5)):(O5 / (O1+O2+O3+O4+O5)).

7. The laser pulse generator according to claim 1, characterized in that: The first optical path adjustment unit and the second optical path adjustment unit each have at least one pair of lenses with adjustable distance, and the optical path size is changed by changing the distance between the lenses; the first optical path adjustment unit and the second optical path adjustment unit synchronously increase or decrease the optical path to adjust the pulse frequency of the laser output by the resonance unit.

8. The laser pulse generator according to claim 1, characterized in that: In each of the resonant units, the surface of the cavity mirror and the surface of the reflector layer of the semiconductor saturable absorber mirror are coated with a coating; according to the wavelength of the required laser pulse, the coating is formulated as a coating material that allows a light beam of the required wavelength to pass through, so that only the light beam of the required wavelength is effectively reflected in the resonant cavity.

9. The laser pulse generator according to claim 1, characterized in that: A spot shaping unit is also connected between the output end of the pump source and the input end of the energy distribution unit. The spot shaping unit has a lens group to shape the light beam of the pump source into a spot of preset shape and size and transmit it to the energy distribution unit.

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