Wavelength-tunable 2 [mu] m single-longitudinal-mode all-solid-state pulse laser
By constructing a laser resonator that includes a pump source, an optical coupling system, a Tm:YAP crystal, an acousto-optic modulator, and a birefringent filter, the challenges of wavelength tuning range and spectral width of an all-solid-state 2μm single-longitudinal-mode laser were solved, achieving stable laser output and wide tuning capability.
Patent Information
- Application Number
- CN202520671787.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2026-02-27
- Estimated Expiration
- 2035-04-10
AI Technical Summary
In the existing technology, developing a compact, economical, and widely tunable all-solid-state 2μm single-longitudinal-mode laser remains a major challenge, as it is difficult to achieve a laser with a wide wavelength tuning range and narrow spectral width.
A laser resonant cavity is constructed using a combination of a pump source, a 1:2 optical coupling system, a Tm:YAP crystal, an acousto-optic modulator, a standard etalon, and a birefringent filter. The laser pulse is generated by modulating the laser through the acousto-optic modulator, and the laser wavelength and spectral width are tuned by the birefringent filter.
Stable generation of 2μm lasers has been achieved, providing a wider wavelength tuning range and more direct tuning, while also achieving a narrower spectral width. The laser structure is simple and the performance is stable.
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Figure CN223957069U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to the technical field of laser, especially to a wavelength tunable 2 mu m single longitudinal mode all solid state pulse laser. BACKGROUND
[0002] In the prior art, 2 mu m eye safety solid state laser is widely used in laser radar, atmospheric monitoring, laser medicine, spectral analysis and other applications due to its high atmospheric transmittance, water absorption characteristics and significant carbon dioxide absorption peak. Specifically, in the field of high coherence detection, single longitudinal mode (SLM) laser with narrow spectral linewidth and high beam quality is crucial to ensure the detection accuracy when identifying target gas. As shown in the figure, the 2 mu m wavelength region has several important absorption lines, including water vapor, carbon dioxide and ammonia absorption lines. Therefore, developing a tunable SLM laser in the 2 mu m range has considerable scientific and practical significance for laser radar systems used for atmospheric detection. Such a laser facilitates the use of a single light source to simultaneously detect various gases. Figure 1
[0003] Generally speaking, implementing a 2 mu m SLM laser requires integrating a specific mode selection element into a laser resonator using a Tm 3 + or Ho3+ doped gain medium with direct pumping. Techniques for obtaining SLM lasers include a short cavity method, an intra-cavity Fabry-Perot (F-P) metal plate method, a twisted mode technique, a unidirectional ring laser, a volume Bragg grating (VBG) method, an injection seeding technique, etc. In 2018, Dai et al. reported a tunable SLM seed laser containing two F-P metal towers and a piezoelectric transducer (PZT). By adjusting the PZT voltage, the wavelength can be tuned from 2050.962 nm to 2051.000 nm. In 2020, Dai et al. proposed a twisted mode SLM Ho:YAG laser with a wavelength tuning range from 2096.94 nm to 2098.48 nm, implemented using a metal plate. The pulse repetition frequency of the laser is 2 kHz, the single pulse energy is 0.2 mJ, and the pulse duration is 116.5 ns. In the same year, Berthome et al. reported a pulsed SLM tunable Tm:YAP laser with a single pulse energy of 230 mu J, a pulse duration of 50 ns, and a repetition frequency of 1 kHz. The output wavelength was adjusted from 1940 to 1960 nm using a volume Bragg grating. Despite numerous reports, developing a compact, economical, and widely tunable all-solid-state 2 mu m SLM laser remains a significant challenge. SUMMARY
[0004] The utility model discloses a wavelength tunable 2mu m single longitudinal mode all solid state pulse laser, simple structure can stably produce 2mu m laser, provide wider wavelength tuning range and more direct tuning, also realize narrower spectral width simultaneously.
[0005] In order to realize the above-mentioned purpose, the utility model provides a wavelength tunable 2mu m single longitudinal mode all solid state pulse laser, including pump source for producing pump light, the output of pump source is provided with 1:2 light coupling system for coupling to pump light, the output of 1:2 light coupling system is provided with input mirror, the output of input mirror is provided with Tm:YAP crystal, for producing 2mu m laser, the output of Tm:YAP crystal is provided with acoustooptic modulator for modulating laser pulse, the output of acoustooptic modulator is provided with etalon for the selection of single longitudinal mode in laser and the compression of line width, the output of etalon is provided with birefringent filter piece for tuning laser wavelength and the compression of laser line width, the output of birefringent filter piece is provided with output mirror, and input mirror and output mirror jointly constitute laser resonant cavity.
[0006] Preferably, the pump source is a 793nm fiber-coupled laser diode with a maximum output power of 30W, and the iron core diameter of the pump source is 200mu m.
[0007] Preferably, the input mirror is a plano-concave mirror with a radius of curvature of 500mm, the high reflection coating of the input mirror is 1850-2150nm, and the anti-reflection coating is 770-810nm.
[0008] Preferably, the Tm:YAP crystal is wrapped with an indium foil and fixed on a copper heat sink, and is kept at 16 DEG C through water cooling.
[0009] Preferably, the geometric size of the Tm:YAP crystal is 3*3*7mm3, and the doping concentration is 3.0.
[0010] Preferably, the output mirror is a plane mirror coated with a 15% transmittance coating at 1850-2150nm.
[0011] Therefore, the utility model adopts the above-mentioned wavelength tunable 2mu m single longitudinal mode all solid state pulse laser, simple structure can stably produce 2mu m laser, provided wider wavelength tuning range and more direct tuning, also realized narrower spectral width simultaneously.
[0012] The technical scheme of the utility model will be described in further detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF DRAWINGS
[0013] Figure 1is a characteristic absorption spectrum of some common gases;
[0014] Figure 2 is a structure diagram of a 2 mu m single longitudinal mode all-solid-state pulse laser with tunable wavelength according to an embodiment of the utility model;
[0015] Figure 3 is a cavity frequency comb (blue) and the transmission curve (red) diagram of etalon;
[0016] Figure 4 is the output power and output spectrum diagram of laser; wherein (a) indicates output power, (b) indicates output spectrum;
[0017] Figure 5 is the output energy and pulse duration diagram of laser under different incident pump power at different pulse repetition frequency; wherein, (a) indicates output energy, (b) indicates pulse duration;
[0018] Figure 6 is the time waveform curve diagram of laser under 1kHz repetition frequency; wherein, (a) indicates pulse trajectory, (b) indicates pulse sequence;
[0019] Figure 7 is the time distribution and corresponding FFT: fast Fourier transform curve diagram; wherein, (a) indicates multi-longitudinal mode pulse, (b) indicates single longitudinal mode pulse;
[0020] Figure 8 is the tuning spectrum and output power diagram of central wavelength range 1887nm to 2003nm; wherein, (a) indicates tuning spectrum, (b) indicates output power.
[0021] Reference signs
[0022] 1, pump source; 2, 1:2 optical coupling system; 3, input mirror; 4, Tm:YAP crystal; 5, acoustooptic modulator; 6, etalon; 7, birefringent filter; 8, output mirror. DETAILED DESCRIPTION
[0023] The technical scheme of the utility model is further described below through the drawings and embodiments.
[0024] Unless otherwise defined, the technical or scientific terms used in this utility model shall have the ordinary meaning understood by one of ordinary skill in the art to which this utility model pertains. The terms "first," "second," and similar terms used in this utility model do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.
[0025] Example 1
[0026] like Figure 2 As shown, this invention provides a wavelength-tunable 2μm single-longitudinal-mode all-solid-state pulsed laser, including a pump source 1 for generating pump light. The pump source 1 is a 793nm fiber-coupled laser diode with a maximum output power of 30W, and the core diameter of the pump source 1 is 200μm.
[0027] The output end of pump source 1 is equipped with a 1:2 optical coupling system 2 for coupling the pump light. The output end of the 1:2 optical coupling system 2 is equipped with an input mirror 3, which is a plano-concave mirror with a radius of curvature of 500 mm. The high-reflectivity coating of the input mirror 3 is 1850-2150 nm, and the anti-reflection coating is 770-810 nm.
[0028] The output terminal of input mirror 3 is equipped with a Tm:YAP crystal 4 for generating 2μm laser light. The Tm:YAP crystal 4 has geometric dimensions of 3×3×7mm. 3 The doping concentration is 3.0. In this embodiment, the Tm:YAP crystal 4 is wrapped with indium foil and fixed on a copper heat sink, and maintained at 16°C by water cooling. This crystal parameter and temperature control ensures that Tm 3+ The low influence of the reabsorption and upconversion effects of the quasi-three-level system on the crystal thermal effect means that approximately 55% of the incident pump power is absorbed by the Tm:YAP crystal 4.
[0029] In order to obtain higher and easily controlled laser pulse repetition rate, an acousto-optic modulator 5 is arranged at the output end of the Tm:YAP crystal 4 for modulating the laser generated pulses. The output end of the acousto-optic modulator 5 is arranged with an etalon 6 for selection of single longitudinal mode in the laser and compression of the linewidth. The output end of the etalon 6 is arranged with a birefringent filter 7 for tuning the laser wavelength and compressing the laser linewidth. The output end of the birefringent filter 7 is arranged with an output mirror 8, which is a flat mirror coated with a 15% transmittance coating at 1850-2150 nm. Among them, the etalon 6 and the birefringent filter 7 are the key parts to realize the laser linewidth compression and wavelength tuning, which determines whether the 2 μm laser can be stably output.
[0030] The input mirror 3 and the output mirror 8 together constitute a laser resonator, and the polarized beam passing through the birefringent filter 7 is split into ordinary light o rays and extraordinary light e rays with different phase delays. By rotating the birefringent filter 7, the phase difference between the o rays and the e rays changes, thereby changing the wavelength of maximum transmission.
[0031] In this embodiment, the length of the laser resonator composed of the input mirror 3 and the output mirror 8 is 120 mm during the experiment, in order to accommodate the switching of the acousto-optic modulator 5. As shown in Figure 3 , the blue curve is the cavity theoretical frequency comb, and the red curve is the theoretical transmission data of the uncoated 5 mm thick YAG etched plate, the parameters of the metal plate are determined, only one longitudinal mode of the laser resonator is selected, and single longitudinal mode operation is realized.
[0032] When the acousto-optic modulator 5 is removed from the resonator, the laser works in continuous wave (CW) mode. The continuous wave and pulse output power of the laser is measured as a function of pump power using a power meter (PM100D, Thorlabs), and plotted in Figure 4 (a). At a pump power of 14.24 W, the maximum output power reaches 1.85 W, corresponding to a slope efficiency of 27.16%. This pump power not only maintains high laser optical efficiency, but also prevents damage to various optical elements. When the acousto-optic modulator 5 is inserted into the laser resonator, the laser works in pulse mode. At a pump power of 14.24 W, the maximum average output power of the SLM pulse laser at a repetition frequency of 1 kHz is 1.37 W, and the corresponding slope efficiency is 26.93%. The spectrum of the laser is measured by a laser spectrum analyzer (Wavescan S08869, A.P.E), as shown in Figure 4 (b), the center wavelength is 1986.78 nm, and the spectral width is less than 1 nm, limited by the resolution of the spectrometer analyzer.
[0033] By precisely adjusting the tilt angle of the etalon 6, the laser cavity is optimized and the laser can be operated stably. The single pulse energy and pulse duration of the laser at different pulse repetition frequencies are shown in Figure 5 . As can be seen from Figure 5 (a), at the same pulse repetition frequency, the single pulse energy increases with the increase of the incident pump power. When the incident pump power increases from 0.06 mJ to 1.37 mJ, the single pulse power increases from 9.22 W to 14.24 W. When the pulse repetition frequency increases from 1 kHz to 10 kHz, the output energy at the maximum pump power decreases from 1.37 mJ to 0.14 mJ. The pulse duration at the pulse repetition frequencies of 1 kHz, 5 kHz and 10 kHz is measured, as shown in Figure 5 (b). At the same pulse repetition frequency, the pulse duration narrows with the increase of the pump power. The pulse duration is 139 ns at the pulse repetition frequency of 1 kHz and the pump power of 14.24 W. Since the laser produces a narrow pulse duration and higher single pulse energy at the pulse repetition frequency of 1 kHz, the time domain and frequency domain characteristics of the 1 kHz pulse need to be checked next.
[0034] The SLM pulse is recorded by an InGaAs detector and a digital oscilloscope, RIGOL MSO8204 (2 GHz), to record the output characteristics of the laser. The time waveform of a single pulse and the pulse sequence of the laser are shown in Figure 6 . At the pulse repetition frequency of 1 kHz and the pump power of 14.24 W, the corresponding output pulse duration of the laser is 139 ns.
[0035] In addition, the time distribution of the laser and the corresponding fast Fourier transform (FFT) curve are shown in Figure 7 . When the birefringent filter 7 and the etalon 6 are not inserted into the resonator (free running mode), Figure 7 (a) clearly observes a multi-mode beating peak, indicating that the laser is working in a multi-longitudinal mode at this time. As shown in Figure 7 (b), the Fourier transform curve has no mode beating peak, and the time pulse profile is smoother than that of Figure 7 (a), which is the reason why the laser works in a single longitudinal mode. By checking the output waveform and looking for the existence of any beating frequency component (using an oscilloscope), the SLM ratio of the laser is determined in real time. The measured SLM ratio is about 99.5% in 10000 pulses.
[0036] By rotating the birefringent filter 7, the laser can be tuned at different wavelengths. In addition, since the Tm:YAP crystal 4 is a natural birefringent crystal, the output beam is polarized, and the insertion of the birefringent filter 7 allows the laser to pass through the acousto-optic modulator 5 at a pump power of 14.24W, a repetition rate of 1kHz, a single pulse energy of 1.37mJ, and a pulse duration of 139ns. At this repetition rate, the output SLM ratio is 99.5%. By using the birefringent filter 7, the output wavelength of the laser is from 1887nm to 2003nm, generating a total adjustable range of 116nm, and the output power is tuned in a wide spectral range from 0.02W to 1.35W, as shown in Figure 8 (a) measured at different wavelengths SLM output power, plotted in Figure 8 (b).
[0037] Therefore, the utility model discloses a kind of wavelength tunable 2 μm single longitudinal mode all-solid-state pulsed laser, simple structure can stably produce 2 μm laser, provide wider wavelength tuning range and more direct tuning, also realize narrower spectral width simultaneously.
[0038] Finally, it should be noted that: the above examples are only used to illustrate the technical scheme of the utility model and not to limit it, although the utility model is described in detail with reference to the preferred embodiment, those skilled in the art should understand: it can still modify or equivalent replace the technical scheme of the utility model, and these modifications or equivalent replacements cannot make the modified technical scheme deviate from the spirit and scope of the technical scheme of the utility model.
Claims
1. A wavelength-tunable 2 pm single-longitudinal-mode all-solid-state pulsed laser, characterized by: The application relates to a 2-micron laser device, which comprises a pump source for generating pump light; the output end of the pump source is provided with a 1:2 light coupling system for coupling the pump light; the output end of the 1:2 light coupling system is provided with an input mirror, the output end of the input mirror is provided with a Tm:YAP crystal for generating 2-micron laser; the output end of the Tm:YAP crystal is provided with an acousto-optic modulator for modulating laser to generate pulses; the output end of the acousto-optic modulator is provided with an etalon for selecting a single longitudinal mode in the laser and compressing the laser line width; the output end of the etalon is provided with a birefringent filter for tuning the laser wavelength and compressing the laser line width; the output end of the birefringent filter is provided with an output mirror, and the input mirror and the output mirror jointly constitute a laser resonant cavity.
2. The wavelength-tunable 2 pm single-longitudinal-mode all-solid-state pulsed laser according to claim 1, characterized in that: The pump source is a 793nm fiber-coupled laser diode with a maximum output power of 30W, and the iron core diameter of the pump source is 200mu m.
3. The wavelength-tunable 2 pm single-longitudinal-mode all-solid-state pulsed laser of claim 1, wherein: The input mirror is a plano-concave mirror with a curvature radius of 500mm; the high reflection coating of the input mirror is 1850-2150nm, and the anti-reflection coating is 770-810nm.
4. The wavelength-tunable 2 pm single-longitudinal-mode all-solid-state pulsed laser of claim 1, wherein: The Tm:YAP crystal is wrapped by an indium foil and fixed on a copper heat sink, and is kept at 16 DEG C through water cooling.
5. The wavelength-tunable 2 pm single-longitudinal-mode all-solid-state pulsed laser according to claim 1, characterized in that: The Tm:YAP crystal has a geometric size of 3x3x7 mm 3 with a doping concentration of 3.
0.
6. The wavelength-tunable 2 pm single-longitudinal-mode all-solid-state pulsed laser according to claim 1, characterized in that: The output mirror is a plane mirror coated with a 15% transmittance coating at 1850-2150nm.