A continuous-wave infrared laser based on a new ZGP crystal

Abstract

The present invention discloses a continuous wavelength infrared laser based on a novel ZGP crystal, comprising a tunable random Raman fiber laser, an erbium-doped fiber amplifier, a wavelength division multiplexer, a fiber coupler, a ZnSe beam focusing lens, a YS-ZGP crystal, a ZnSe beam collecting lens, and a long-pass filter connected in sequence. The present invention benefits from the novel high-performance YS-ZGP crystal and combines the independently developed high-power random Raman fiber laser to provide a continuous wavelength infrared laser, which overcomes the problems of low output power and limited tuning freedom of the existing continuous wavelength infrared laser based on difference frequency conversion technology.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and particularly to a continuous wavelength wave infrared laser based on a novel ZGP crystal. Background Art

[0002] Continuous wavelength wave infrared lasers (>5μm) play a crucial role in fields such as multi-molecule detection, Fourier transform spectroscopy, and atmospheric communication. In particular, continuous wavelength wave infrared lasers in the 8-12μm band are often used in environmental monitoring, remote sensing, and military confrontation due to their relatively low transmission loss in the atmosphere. It is worth mentioning that frequency conversion technology in nonlinear crystals, especially difference frequency conversion technology, is an effective method for generating continuous wavelength wave infrared lasers. Due to its simple structure and large operation freedom, it has attracted more and more researchers' attention.

[0003] In recent years, the generation of continuous wavelength wave infrared lasers based on difference frequency conversion technology in birefringent crystals such as AgGaS2 / Se2, LiInS2, GaSe, BaGa4Se7, etc. has been achieved. However, the above solutions are either limited by the parameters of the crystal itself, such as relatively small effective nonlinear coefficients and thermal conductivities, or limited by the power of the pump / signal light source. Therefore, the output power of the continuous wavelength wave infrared lasers generated is relatively low (<10μW). In addition to the above birefringent crystals, nonlinear crystals with an orientation-patterned (OP) quasi-phase matching mechanism, including OP-GaAs and OP-GaP, etc., have also been considered for generating continuous wavelength wave infrared lasers. In particular, OP-GaAs crystals can achieve an output power of the generated long-wave infrared laser in the milliwatt range due to their high nonlinear coefficient and good thermal conductivity. However, due to the existence of the orientation-patterned structure in such crystals, on the one hand, it leads to a relatively complex manufacturing process and relatively high cost; on the other hand, it also limits the spectral tuning range of the continuous wavelength wave infrared lasers generated. Therefore, it is of great significance to use birefringent crystals with excellent performance, mature manufacturing processes, and high operation freedom, combined with high-power pump / signal sources (such as high-power fiber lasers in the near-infrared band), to achieve a continuous wavelength wave infrared laser in the milliwatt range. Summary of the Invention

[0004] In view of the above problems, the present invention provides a continuous wavelength wave infrared laser based on a novel ZGP crystal.

[0005] The present invention adopts the following technical solutions:

[0006] A continuous-wavelength mid-infrared laser based on a novel YS-ZGP crystal, comprising: a tunable random Raman fiber laser, an erbium-doped fiber amplifier, a wavelength division multiplexer, an optical fiber coupler, a ZnSe beam focusing lens, a YS-ZGP crystal, a ZnSe beam collection lens, and a long-pass filter, which are connected in sequence;

[0007] The tunable random Raman fiber laser is used to pump the YS-ZGP crystal;

[0008] The erbium-doped fiber amplifier is used to provide a signal source for the mid-infrared laser;

[0009] The wavelength division multiplexer is used to couple the signal light and the pump light into the same optical fiber to form an all-fiber light source structure;

[0010] The optical fiber coupler is used to collimate the light after fiber transmission;

[0011] The ZnSe beam focusing lens is used to focus the signal light and the pump light;

[0012] The YS-ZGP crystal is used to achieve nonlinear frequency conversion and generate mid-infrared output;

[0013] The ZnSe beam collection lens is used to collect the generated mid-infrared light;

[0014] The long-pass filter is used to filter out the residual pump light and the amplified signal light.

[0015] Furthermore, the tunable random Raman fiber laser is a semi-open cavity Raman fiber laser.

[0016] Furthermore, the erbium-doped fiber amplifier is provided with a tunable seed source by a distributed feedback laser, and the output spectral coverage range is 1527 - 1567 nm.

[0017] Furthermore, the transmission range of the YS-ZGP crystal is 0.75 - 12 μm.

[0018] Furthermore, the YS-ZGP crystal adopts a composite annealing process of vacuum-powder wrapping, and the grown ZGP crystal is annealed at high temperature in the ZGP crystal powder, so that the infrared transmittance of the crystal in the range of 0.75 - 2.5 μm is greatly improved, and the optical uniformity is further improved.

[0019] Furthermore, the average output power of the tunable random Raman fiber laser is 5 W.

[0020] Furthermore, the spectral coverage range of the near-infrared laser output by the tunable random Raman fiber laser is 1280 - 1380 nm.

[0021] Furthermore, the focal length of the ZnSe beam focusing lens is 50 mm.

[0022] Furthermore, the focal length of the ZnSe beam collection lens is 50 mm.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. In the present invention, a novel ZGP crystal is adopted, which overcomes the limitation of the pump source wavelength caused by the energy limitation of the forbidden band width of the traditional ZGP crystal (only capable of being pumped at a wavelength of 2 μm), provides the possibility for using an economically mature high-power near-infrared band laser as a pump / signal source, and lays a foundation for realizing the output of a continuous wavelength wave infrared laser in the milliwatt level.

[0025] 2. In the present invention, a birefringent crystal is used as the difference frequency conversion medium. Compared with orientation-patterned OP-GaAs, etc., it has a higher degree of freedom in spectral output tuning.

[0026] 3. In the present invention, a tunable random Raman fiber laser is used as the pump source, and its output power has strong scalability, enabling the output power of the generated continuous wavelength wave infrared laser to reach the milliwatt level. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below only relate to some embodiments of the present invention and do not limit the present invention.

[0028] Figure 1 It is the transmission spectrum of the novel YS-ZGP used in the embodiments of the present invention in the near-infrared region;

[0029] Figure 2 It is the transmission spectrum of the novel YS-ZGP used in the embodiments of the present invention in the infrared region;

[0030] Figure 3 It is the schematic diagram of the tunable continuous wavelength wave infrared laser device based on the novel YS-ZGP of the present invention;

[0031] Figure 4 It is the typical output characteristic of the long-wave infrared laser of the present invention;

[0032] Figure 5 It is the spectral tuning output characteristic diagram of the long-wave infrared laser of the present invention;

[0033] In the figure: 1 - Transmission spectrum of the novel YS-ZGP used in the embodiments of the present invention in the near-infrared region, 2 - Transmission spectrum of the traditional ZGP crystal in the near-infrared region, 3 - Tunable random Raman fiber laser, 4 - Erbium-doped fiber laser, 5 - Wavelength division multiplexer, 6 - Fiber coupler, 7 - ZnSe beam focusing lens, 8 - YS-ZGP crystal, 9 - ZnSe beam collection lens, 10 - Long-pass filter. Detailed implementation manners

[0034] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0035] The present invention will be further described below with reference to the drawings and embodiments.

[0036] As Figure 1 shown are the transmittance curves 1 of the novel YS-ZGP crystal used in the embodiments of the present invention in the near-infrared region and the transmittance curves 2 of the traditional ZGP crystal in the near-infrared region. By comparison, the transmittance of the novel YS-ZGP crystal in the near-infrared region has been greatly improved, and the transmittance in the 1-μm region has increased from 10% to 45%.

[0037] As Figure 2 shown is the transmittance curve of the novel YS-ZGP crystal used in the embodiments of the present invention in the infrared region. The transmission range of this crystal is 0.75 - 12 μm. Specifically, the YS-ZGP crystal adopts a composite annealing process of vacuum-powder wrapping, and the grown ZGP crystal is annealed at high temperature in the ZGP crystal powder, so that the infrared transmittance of the crystal in the range of 0.75 - 2.5 μm is greatly improved, and the optical uniformity is further improved.

[0038] As Figure 3 shown is a schematic diagram of a continuous-wavelength wave infrared laser device based on the novel ZGP crystal in the present invention, including a tunable random Raman fiber laser 3, an erbium-doped fiber amplifier 4, a wavelength division multiplexer 5, a fiber coupler 6, a ZnSe beam focusing lens 7 with a focal length of 50 mm, a YS-ZGP crystal 8, a ZnSe beam collection lens 9 with a focal length of 50 mm, and a long-pass filter 10, which are connected in sequence.

[0039] Among them, the tunable random Raman fiber laser 3 is used to pump the YS-ZGP crystal. In particular, the tunable random Raman fiber laser 3 is a semi-open cavity Raman fiber laser, with an output average power of 5 W, the spectral coverage range of the output near-infrared laser being 1280 - 1380 nm, and having strong power expansion characteristics.

[0040] Among them, the erbium-doped fiber amplifier 4 is used to provide a signal source for the mid-infrared laser. In particular, the erbium-doped fiber amplifier 4 is provided with a tunable seed source by a distributed feedback laser, with the output spectral coverage range being 1527 - 1567 nm and the maximum output power reaching 10 W.

[0041] The wavelength division multiplexer 5 is used to couple the signal light and the pump light into the same fiber to form an all-fiber light source structure.

[0042] The fiber coupler 6 is used to collimate the light after fiber transmission.

[0043] The ZnSe beam focusing lens 7 is used to focus the signal light and the pump light; both sides of the lens are coated with an antireflection film of 2 - 13 μm, and the focal length of the lens is 50 mm.

[0044] The YS-ZGP crystal 8 is used to achieve nonlinear frequency conversion to generate mid-infrared output; for the YS-ZGP crystal, the transmission range is 0.75 - 12 μm.

[0045] The ZnSe beam collection lens 9 is used to collect the generated mid-infrared light.

[0046] The long-pass filter 10 is used to filter out the residual pump light and the amplified signal light.

[0047] Figure 4 (a) is the spectral diagram of the self-made random Raman laser outputting a laser with a central wavelength of 1360 nm used in the embodiment of the present invention, and the 3 dB bandwidth is 3.11 nm.

[0048] Figure 4 (b) is the typical spectral diagram of the output of the erbium-doped fiber laser used in the embodiment of the present invention, and its central wavelength is 1560 nm.

[0049] Figure 4 (c) is the spectrum of the mid-infrared continuous laser generated by the difference frequency effect in the embodiment of the present invention. It can be seen that at 1360 nm and 1560 nm in the new YS-ZGP crystal structure, through difference frequency conversion, mid-infrared continuous light laser output with a central wavelength of 10.66 μm can be achieved.

[0050] Figure 4(d) is the input-output curve of the mid-infrared laser generated in the embodiment of the present invention. In the embodiment of the present invention, the average power of the pump light is fixed at 1.3 W, and the output power of the mid-infrared continuous light has a linear relationship with the signal light power. When the signal light power is 2.25 W, the mid-infrared output power reaches 43 μW.

[0051] Figure 5 (a) is the angular phase-matching curve of the novel YS-ZGP crystal used in the embodiment of the present invention.

[0052] Figure 5 (b) is the tunable pump spectrum used in the embodiment of the present invention, and the tunable spectrum used covers the range of 1330 nm - 1390 nm.

[0053] Figure 5 (c) and Figure 5 (d) are respectively the tunable output spectrum and its power of the continuous-wavelength mid-infrared laser in the embodiment of the present invention. The spectrum covers the range of 9.25 - 12 μm, and in the wavelength range of 9.5 μm - 11 μm, the output power is greater than 40 μW.

[0054] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A continuous wavelength infrared laser based on a new ZGP crystal, characterized in that: It includes a tunable random Raman fiber laser, an erbium-doped fiber amplifier, a wavelength division multiplexer, a fiber coupler, a ZnSe beam focusing lens, a YS-ZGP crystal, a ZnSe beam collecting lens, and a long-pass filter connected in sequence; The tunable random Raman fiber laser is used to pump the YS-ZGP crystal; the tunable random Raman fiber laser is a semi-open cavity Raman fiber laser; the tunable random Raman fiber laser has an average output power of 5W, and the spectrum coverage range of the output near-infrared laser is 1280-1380nm; The erbium-doped fiber amplifier is used to provide a signal source for the mid-infrared laser; The wavelength division multiplexer is used to couple the signal light and the pump light to the same optical fiber to form an all-optical light source structure; The optical fiber coupler is used to collimate the light after optical fiber transmission; The ZnSe beam focusing lens is used to focus the signal light and the pump light; The YS-ZGP crystal is used to achieve nonlinear frequency conversion and generate mid-infrared output; The ZnSe beam collection lens is used to collect the generated mid-infrared; The long-pass filter is used to filter out residual pump light and amplified signal light; The YS-ZGP crystal has a transmission range of 0.75-12 μm, and the YS-ZGP crystal adopts a vacuum-powder encapsulation composite annealing process, and the grown ZGP crystal is annealed at high temperature in ZGP crystal powder.

2. A continuous wavelength infrared laser based on a novel ZGP crystal according to claim 1, characterized in that: The Erbium-doped Fiber Amplifier is provided with a tunable seed source by a distributed feedback laser, and the output spectrum covers the range of 1527-1567nm.

3. A continuous wavelength infrared laser based on a novel ZGP crystal according to claim 1, characterized in that: The focal length of the ZnSe beam focusing lens is 50 mm.

4. A continuous wavelength infrared laser based on a novel ZGP crystal according to claim 1, characterized in that: The focal length of the ZnSe beam collecting lens is 50 mm.

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