Triple frequency laser generation system

Abstract

The invention discloses a triple frequency laser generation system, which comprises a laser emission module, a spatial isolator, a frequency multiplication module and a sum frequency module, and is characterized in that the laser emission module comprises a single-frequency laser, a phase modulator and a laser amplification module which are connected in sequence, and the laser emission module further comprises a signal generator; the signal generator generates a radio frequency signal to drive the phase modulator to perform phase modulation on single-frequency laser output by the single-frequency laser, the phase modulation amplitude is 2N pi / 3 + / -pi / 10, and N is an integer. Phase modulation is applied to the single-frequency seed laser, the phase modulation depth is controlled, high-power fundamental frequency light output and frequency up-conversion are achieved by suppressing the nonlinear effect in the amplifier, finally single-frequency or narrow-linewidth high-power frequency tripling laser output is achieved, and the problem that high power and narrow linewidth are difficult to consider at the same time is solved.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and particularly to a third-harmonic generation laser generating system. Background Art

[0002] Single-frequency or narrow-linewidth visible and ultraviolet lasers have wide applications in fields such as precision machining, atomic cooling, and biomedicine. Nonlinear optical frequency up-conversion of near-infrared lasers is an important means to obtain high-power lasers in this wavelength band. In the process of obtaining visible and ultraviolet lasers through nonlinear optical frequency conversion, increasing the fundamental frequency optical power is an important way to achieve efficient frequency conversion. However, with the increase in the fundamental frequency optical power, various nonlinear effects will occur in amplifiers, especially in fiber amplifiers. In particular, stimulated Brillouin scattering greatly limits the output power of laser amplifiers. To suppress the nonlinear effects in the amplifier, spectral broadening is usually used to reduce the power spectral density to achieve high-power fundamental frequency optical output. However, this will result in the fundamental frequency optical used for frequency up-conversion no longer being a single-frequency or narrow-linewidth laser, and the linewidth will be further broadened after frequency up-conversion, and single-frequency or narrow-linewidth visible and ultraviolet lasers cannot be obtained. Summary of the Invention

[0003] Aiming at the deficiencies in the prior art, the present invention proposes a third-harmonic generation laser generating system. By applying phase modulation to the fundamental frequency optical before amplification, the single-frequency laser obtains a phase modulation with a modulation depth of 2 N π / 3 ± π / 10 (where N is an integer) to generate a few-frequency laser, reduce its power spectral density in the laser amplifier, and thus suppress the nonlinear effects in the laser amplification process. The amplified laser undergoes first harmonic generation and first sum frequency to obtain a high-power single-frequency or narrow-linewidth third-harmonic generation laser with a phase modulation depth near 0 and integer multiples of 2π.

[0004] The specific technical solution of the present invention is as follows: A third-harmonic generation laser generating system includes a laser emission module, an optical isolator, a harmonic generation module, and a sum frequency module arranged in sequence. The laser emission module includes a single-frequency laser, a phase modulator, and a laser amplification module connected in sequence. The laser emission module also includes a signal generator. The signal generator generates a radio frequency signal to drive the phase modulator to perform phase modulation on the single-frequency laser output by the single-frequency laser, and the phase modulation amplitude is 2 N π / 3 ± π / 10, where N is an integer; after the single-frequency laser passes through the phase modulator, it enters the laser amplifier for amplification, and then passes through the optical isolator, the harmonic generation module, and the sum frequency module in sequence to obtain a single-frequency or narrow-linewidth third-harmonic generation laser with a phase modulation amplitude near 0 and integer multiples of 2π.

[0005] Further, the single-frequency laser is one of a rare-earth doped solid laser, a solid Raman laser, a distributed feedback semiconductor laser, an external cavity semiconductor laser, a distributed feedback fiber laser, and a distributed Bragg reflection fiber laser, and the line width of the generated single-frequency laser is less than 200 MHz.

[0006] Further, the phase modulator is an electro-optic phase modulator with a fiber tail or a spatial electro-optic phase modulator.

[0007] Further, the drive signal phase-modulated by the signal generator is one of a pulse signal, a square wave signal, a pseudo-random code signal, and any signal with an amplitude step-changing over time.

[0008] Further, the laser amplifier used in the laser amplification module is one of a rare-earth doped fiber amplifier, a fiber Raman amplifier, a rare-earth doped solid amplifier, and a solid Raman amplifier.

[0009] Further, the frequency doubling module adopts one of the methods of single-pass frequency doubling, double-pass frequency doubling, single-pass cascaded frequency doubling, and external cavity resonant frequency doubling; the frequency doubling crystal used in this frequency doubling module is: periodically poled lithium niobate, periodically poled stoichiometric lithium tantalate, periodically poled potassium titanyl phosphate crystal, β - barium metaborate crystal, lithium triborate crystal, bismuth borate crystal, cesium lithium borate crystal, potassium titanyl phosphate crystal, potassium dihydrogen phosphate crystal, potassium dideuterium phosphate crystal, ammonium dihydrogen phosphate, ammonium dideuterium phosphate crystal, guanidine tetrafluoroborate crystal, yttrium calcium borate oxide crystal.

[0010] Further, the sum frequency module adopts one of the methods of single-pass sum frequency, double-pass sum frequency, cascaded single-pass sum frequency, and external cavity resonant sum frequency; the sum frequency crystal used in this sum frequency module is: periodically poled lithium niobate, periodically poled stoichiometric lithium tantalate, periodically poled potassium titanyl phosphate crystal, β - barium metaborate crystal, lithium triborate crystal, bismuth borate crystal, cesium lithium borate crystal, potassium titanyl phosphate crystal, potassium dihydrogen phosphate crystal, potassium dideuterium phosphate crystal, potassium dihydrogen phosphate crystal, guanidine tetrafluoroborate crystal, potassium fluoroborate, quartz crystal with additional periodic phase, potassium dihydrogen phosphate crystal with additional periodic phase, potassium dideuterium phosphate crystal with additional periodic phase, phosphoric acid dihydrogen crystal with additional periodic phase, ammonium dideuterium phosphate crystal with additional periodic phase.

[0011] Further, for temperature control of the frequency doubling module and the sum frequency module, a heating sheet or a semiconductor refrigeration sheet is used, and the temperature control accuracy is less than or equal to 0.02 degrees Celsius.

[0012] Compared with the prior art, the beneficial effects of the present invention are: The present invention realizes high-power fundamental frequency light output and frequency up-conversion by applying phase modulation to a single-frequency seed laser and controlling the phase modulation depth, suppressing the nonlinear effects in the amplifier, and finally realizes single-frequency or narrow-linewidth high-power third-harmonic laser output, solving the problem that it is difficult to achieve both high power and narrow linewidth simultaneously. In addition, the frequency up-conversion process is used to realize passive demodulation of the applied phase modulation, without the need for a complex active demodulation system, thus simplifying the device. The invention provides a new technical route for stable high-power single-frequency or narrow-linewidth frequency up-conversion technology, with important practical value and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0014] Figure 1 FIG. is a schematic diagram of a third-harmonic laser generation system provided by the present invention; Figure 2 FIG. is a schematic diagram of the structure of the frequency doubling module provided by the present invention; Figure 3 FIG. is a schematic diagram of the structure of the sum frequency module provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] The following will further describe the present invention in detail with reference to the drawings.

[0016] It should be noted that the following detailed description is illustrative and aims to provide further description of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0017] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0018] The present invention proposes a third-harmonic laser generation system to further improve the output power and stability of single-frequency or narrow-linewidth visible and ultraviolet lasers in the prior art. Method principle: Use a phase modulator to perform a depth of 2 N π / 3 ± π / 10 (where Nis an integer) to suppress nonlinear effects such as stimulated Brillouin scattering during the amplification process and obtain high-power fundamental frequency light. After that, the frequency is up-converted through a single frequency doubling and a single frequency sum process, while passive demodulation of the applied phase modulation is achieved, ultimately generating a high-power tripled frequency single-frequency or narrow-linewidth laser with a phase modulation depth of 0 and an integer multiple of 2π.

[0019] An embodiment for implementing the above method is given below.

[0020] Example 1: Please refer to Figures 1 - 3 A triple frequency laser generation system includes a laser emission module, a spatial isolator 5, a frequency doubling module 6, and a sum frequency module 7, which are arranged in sequence. The laser emission module includes a single-frequency laser 1, a phase modulator 2, and a laser amplification module 4, which are connected in sequence through optical fibers. The laser emission module also includes a signal generator 3, which is connected to the phase modulator 2 through a radio frequency line. The signal generator 3 generates a radio frequency signal to drive the phase modulator 2 to phase modulate the single-frequency laser output by the single-frequency laser 1, and the phase modulation amplitude is 2 N π / 3±π / 10, where N After passing through the phase modulator 2, the single-frequency laser enters the laser amplifier 4 for amplification, and then passes through the spatial isolator 5, the frequency doubling module 6 and the sum frequency module 7 in sequence to obtain a single-frequency or narrow-linewidth tripled frequency laser with a phase modulation amplitude of 0 and an integer multiple of 2π.

[0021] The single-frequency laser 1 is a single-frequency distributed feedback semiconductor laser with a line width of 1 MHz and a central wavelength of 1064 nm. The phase modulator 2 is a lithium niobate electro-optic modulator with a pigtail. The signal generator 3 generates a periodic square wave signal to drive the phase modulator 2. The driving signal frequency is 3.5 GHz and the amplitude is 10 V; the laser amplification module 4 uses ytterbium-doped fiber as the gain fiber of the laser amplifier, the frequency doubling module 6 is a single-pass frequency doubling device, the frequency doubling module 6 includes a first optical lens 6.1, a frequency doubling crystal 6.2, and a second optical lens 6.3 arranged in sequence, the frequency doubling crystal 6.2 uses a periodically poled lithium niobate crystal (PPLN), the frequency doubling module 6 uses a semiconductor refrigeration sheet for temperature control, and the accuracy is 0.002 degrees Celsius, the sum frequency module 7 uses a single-pass sum frequency method, which includes a third optical lens 7.1, a sum frequency crystal 7.2, and a fourth optical lens 7.3 arranged in sequence, the sum frequency crystal 7.2 uses a lithium triborate crystal (LBO), and the sum frequency module 7 uses TEC for temperature control, and the accuracy is 0.002 degrees Celsius.

[0022] Example 2: Please refer to Figures 1 - 3, A triple-frequency laser generation system, comprising a laser emission module, a spatial isolator 5, a frequency doubling module 6, and a sum frequency module 7 arranged in sequence. The laser emission module includes a single-frequency laser 1, a phase modulator 2, and a laser amplification module 4 connected in sequence through an optical fiber. The laser emission module further includes a signal generator 3. The signal generator 3 is connected to the phase modulator 2 through a radio frequency line. The signal generator 3 generates a radio frequency signal to drive the phase modulator 2 to perform phase modulation on the single-frequency laser output by the single-frequency laser 1, and the phase modulation amplitude is 2 N π / 3 ± π / 10, where N is an integer. After the single-frequency laser passes through the phase modulator 2, it enters the laser amplifier 4 for amplification, and then passes through the spatial isolator 5, the frequency doubling module 6, and the sum frequency module 7 in sequence to obtain a single-frequency or narrow linewidth triple-frequency laser with a phase modulation amplitude near 0 and integer multiples of 2π.

[0023] The single-frequency laser 1 is a single-frequency external cavity semiconductor laser with a linewidth of 120 MHz and a central wavelength of 1178 nm. The phase modulator 2 is an electro-optic modulator with a pigtail. The signal generator 3 generates a pseudo-random code signal to drive the phase modulator 2, and the driving signal code rate is 2 Gbps and the amplitude is 12V. The laser amplification module 4 is a fiber Raman laser amplifier, and a phosphorus-doped fiber is used as the gain fiber. The frequency doubling module 6 is a single-pass frequency doubling device. The frequency doubling module 6 includes a first optical lens 6.1, a frequency doubling crystal 6.2, and a second optical lens 6.3 arranged in sequence. The frequency doubling crystal 6.2 is selected as a lithium triborate crystal (LBO), and a heating sheet is used for temperature control with an accuracy of 0.02 degrees Celsius. The sum frequency module 7 adopts the method of external cavity resonance sum frequency of frequency-doubled light resonance. The sum frequency module 7 includes an input / output coupling cavity mirror 7.1, a sum frequency crystal 7.2, and a digital lock cavity servo system 7.3 arranged in sequence. The sum frequency crystal 7.2 is selected as a cesium lithium borate crystal (CLBO), and a heating sheet is used for temperature control with an accuracy of 0.02 degrees Celsius.

[0024] The above is only the preferred embodiment of the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of the protection of the technical solution of the present invention.

Claims

1. A triple-frequency laser generation system, comprising a laser emission module, a spatial isolator (5), a frequency doubling module (6), and a sum frequency module (7) arranged in sequence. The laser emission module includes a single-frequency laser (1), a phase modulator (2), and a laser amplification module (4) connected in sequence. It is characterized in that, The laser emission module further includes a signal generator (3). The signal generator (3) generates a radio frequency signal to drive a phase modulator (2) to perform phase modulation on the single-frequency laser output by the single-frequency laser (1), and the phase modulation amplitude is 2 N π / 3±π / 10, where N is an integer; after the single-frequency laser passes through the phase modulator (2), it enters the laser amplifier (4) for amplification, and then sequentially passes through an optical isolator (5), a frequency doubling module (6), and a sum frequency module (7) to obtain single-frequency or narrow linewidth triple-frequency laser with a phase modulation amplitude near 0 and integer multiples of 2π.

2. A triple-frequency laser generation system as described in claim 1, wherein, The single-frequency laser (1) is one of a rare-earth doped solid laser, a solid Raman laser, a distributed feedback semiconductor laser, an external cavity semiconductor laser, a distributed feedback fiber laser, and a distributed Bragg reflector fiber laser, and the linewidth of the generated single-frequency laser is less than 200 MHz.

3. The triple-frequency laser generating system according to claim 1, wherein The phase modulator (2) is an electro-optic phase modulator with a fiber tail or a spatial electro-optic phase modulator.

4. The triple-frequency laser generation system according to claim 1, wherein The drive signal for phase modulation of the signal generator (3) is one of a pulse signal, a square wave signal, a pseudo-random code signal, and any signal with an amplitude that changes stepwise over time.

5. A third-harmonic generation laser generating system according to claim 1, wherein The laser amplifier used in the laser amplification module (4) is one of a rare-earth doped fiber amplifier, a fiber Raman amplifier, a rare-earth doped solid amplifier, and a solid Raman amplifier.

6. A triple-frequency laser generation system according to claim 1, characterized in that, The frequency doubling module (6) adopts one of the methods of single-pass frequency doubling, double-pass frequency doubling, single-pass cascaded frequency doubling, and external cavity resonance frequency doubling; the frequency doubling crystal used in the frequency doubling module (6) is: periodically poled lithium niobate, periodically poled stoichiometric lithium tantalate, periodically poled potassium titanyl phosphate crystal, β - barium metaborate crystal, lithium triborate crystal, bismuth borate crystal, cesium lithium borate crystal, potassium titanyl phosphate crystal, potassium dihydrogen phosphate crystal, potassium di-deuterium phosphate crystal, ammonium dihydrogen phosphate, ammonium di-deuterium phosphate crystal, guanidine tetrafluoroborate crystal, yttrium calcium borate oxide crystal.

7. A triple-frequency laser generation system as described in claim 1, wherein, The sum-frequency module (7) adopts one of the following methods: single-pass sum-frequency, double-pass sum-frequency, cascaded single-pass sum-frequency, and external cavity resonant sum-frequency; the sum-frequency crystal used in the sum-frequency module (7) is: periodically poled lithium niobate, periodically poled stoichiometric lithium tantalate, periodically poled potassium titanyl phosphate crystal, β - barium metaborate crystal, lithium triborate crystal, bismuth borate crystal, cesium lithium borate crystal, potassium titanyl phosphate crystal, potassium dihydrogen phosphate crystal, potassium di-deuterium phosphate crystal, potassium dihydrogen phosphate crystal, guanidine tetrafluoroborate crystal, potassium fluoroborate, quartz crystal with additional periodic phase, potassium dihydrogen phosphate crystal with additional periodic phase, potassium di-deuterium phosphate crystal with additional periodic phase, potassium dihydrogen phosphate crystal with additional periodic phase, ammonium di-deuterium phosphate crystal with additional periodic phase.

8. A third-harmonic generation laser generating system according to claim 1, characterized in that, For temperature control of the frequency doubling module (6) and the sum frequency module (7), a heating sheet or a thermoelectric cooler is used, and the temperature control accuracy is less than or equal to 0.02 degrees Celsius.

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