CN112421364B - Intermediate infrared dual-wavelength time domain programmable regulation laser based on Nd-MgO-PPLN crystal - Google Patents
Intermediate infrared dual-wavelength time domain programmable regulation laser based on Nd-MgO-PPLN crystal Download PDFInfo
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Abstract
The invention discloses a middle-infrared dual-wavelength time domain programmable control laser based on a Nd-MgO PPLN crystal, which comprises a 813nm semiconductor pumping source, an energy transfer optical fiber, a zoom coupling mirror group, a first 45-degree beam splitter, a middle-infrared parametric light output mirror, a middle-infrared parametric light total reflection mirror, a Nd-MgO PPLN crystal, an acousto-optic Q switch, a second 45-degree beam splitter, an electro-optic crystal and a 1093nm fundamental frequency light total reflection mirror, wherein the 813nm semiconductor pumping source, the energy transfer optical fiber, the zoom coupling mirror group, the first 45-degree beam splitter, the middle-infrared parametric light output mirror and the middle-infrared parametric light total reflection mirror are sequentially arranged on a horizontal light path from left to right, and the 108. Based on the fact that the Nd, MgO, PPLN crystal has the characteristic of dual-wavelength fundamental frequency light, the output of single-wavelength and dual-wavelength mid-infrared laser is realized by utilizing the cooperation of the electro-optical effect of the electro-optical crystal and the zoom coupling lens group, and the time-domain programmable regulation output of the mid-infrared dual-wavelength is realized by utilizing the characteristics of the acousto-optical crystal and the electro-optical crystal.
Description
Technical Field
The invention relates to the field of lasers, in particular to a mid-infrared dual-wavelength time domain programmable control laser based on Nd-MgO-PPLN crystal.
Background
The 3-5 mu m mid-infrared band laser covers the most important transmission window of the atmosphere, and the band has great application prospect in the military and civil fields of spectral detection, environmental monitoring, medical diagnosis, photoelectric countermeasure and the like as an important branch of laser technology research. Based on quasi-phase matching (QPM) technology, an optical parametric oscillator using a periodically polarized crystal as a frequency conversion medium is a main technical means for obtaining tunable laser in a middle infrared spectral region. In recent years, with the continuous development of optical difference frequency THz and differential absorption radar, dual-wavelength mid-infrared optical parametric oscillators are gradually developed, optical parametric oscillators based on frequency conversion of KTP crystal cascade connection, multi-period polarization APLN crystals and the like have become the most widely adopted technical means for obtaining dual-wavelength mid-infrared laser, but because these crystals only have a single frequency conversion function, fundamental frequency pump light needs to be provided through a rare earth ion doped gain crystal. Compared with the prior art, the rare earth ions are doped into the nonlinear frequency conversion medium to form the multifunctional integrated crystal with self-optical parametric oscillation, and particularly, the Nd ion and magnesium oxide doped Nd: MgO: PPLN crystal is taken as a representative crystal, so that the structural advantage of crystal function integration and the quasi-phase matching frequency conversion advantage are both considered, and the method is an important direction for the miniaturization development of the future mid-infrared dual-wavelength laser.
For the intermediate infrared laser output by self-optical parametric oscillation of MgO and PPLN, the same crystal of MgO and PPLN is shared by gain of fundamental frequency light and frequency conversion of the intermediate infrared laser, the fundamental frequency light generated by the crystal directly forms self pumping in a cavity, and for the internal cavity type OPO pumping framework, when a gain crystal pumping source pumps at high power, how to ensure the matching degree of the beam quality of the fundamental frequency light and the focusing parameters in the optical parametric oscillation process is the key point for obtaining the high-efficiency intermediate infrared laser. In the current report about the MgO: PPLN Self-optical parametric oscillation, the pumping power is lower, and the problem faced by the high pumping power is not related, so that the adopted cavity structure is not purposefully designed for improving the quality of the fundamental frequency light beam and guaranteeing the matching of the focusing parameters, see the documents of L.Barraco et al, Self-optical parametric oscillation in periodic polarization-doped lithium-doped nitride, Opt.Lett.2002,27,1540, obviously, the cavity structure can not guarantee the high-efficiency operation of the Self-optical parametric oscillation under the high-power pumping. In the report of the conventional mid-infrared PPLN-OPO in the inner cavity similar to the operating system, in order to deal with the serious thermal effect caused by the high-power pumping, the direct pumping with low quantum loss is usually adopted, the thermal effect influence is reduced, the mode of the oscillating fundamental frequency light spot is improved, meanwhile, a focusing lens is inserted into the resonant cavity, and the structural design of the composite cavity is combined, so that the matching relation between the fundamental frequency light focusing light spot and the parametric light spot at the beam waist is ensured, and the 'stabilizing effect' on the longer fundamental frequency light resonant cavity is also realized, which is referred to in the documents of 'q.sheng et al, Continuous-wave mid-induced intra-resonant single resonator PPLN-OPO under 880nm in-band pumping, opt.2012, 20, 8041'. However, it should be noted that, usually, the direct pumping wavelength is not at the absorption main peak of the gain crystal, and the conversion efficiency of the fundamental frequency light is low compared with the full pumping power, and in addition, for the method of controlling the matching of the light spots by inserting a lens in the cavity, besides increasing the loss and reducing the integration level of the whole machine, because the gain crystal and the frequency conversion crystal in the PPLN-OPO are independent from each other, the method is not suitable for the monocrystal auto-optical parametric oscillation structure of Nd, MgO, PPLN.
Disclosure of Invention
The invention provides a technology for medium-infrared dual-wavelength time domain programmable regulation based on Nd, MgO and PPLN crystals, which can realize the output of single-wavelength medium-infrared laser and the simultaneous output of dual-wavelength medium-infrared laser by regulating a device and a crystal in a resonant cavity, breaks through the technical limitation that the traditional medium-infrared parametric oscillator can not regulate the dual-wavelength time domain through programming, and also solves the problems of larger volume and complex structure of the traditional medium-infrared dual-wavelength laser.
The invention provides a mid-infrared dual-wavelength time domain programmable regulation laser based on Nd: MgO: PPLN crystal, which comprises: 813nm semiconductor pump source, pass can optic fibre, zoom coupling lens cone, first 45 degrees beam splitting mirror, intermediate infrared parametric light output mirror, intermediate infrared parametric light total reflection mirror, MgO PPLN crystal, reputation Q switch, second 45 degrees beam splitting mirror, electro-optic crystal, 1093nm fundamental frequency light total reflection mirror and 1084nm fundamental frequency light total reflection mirror, wherein:
a 813nm semiconductor pump source, an energy transmission optical fiber, a zoom coupling lens group, a first 45-degree beam splitter, a middle infrared parametric light output mirror, a middle infrared parametric light total reflection mirror, Nd, MgO, namely, a PPLN crystal, an acousto-optic Q switch, a second 45-degree beam splitter, an electro-optic crystal and a 1093nm fundamental frequency light total reflection mirror are sequentially arranged on a horizontal optical path of the laser from left to right;
the 813nm semiconductor pump source is used for emitting pump light;
the energy transmission optical fiber is used for transmitting the pump light to the zoom coupling mirror group;
the zoom coupling mirror group is used for adjusting the size of a pumping light spot focused on the end face of the crystal, for example, the pumping light can be adjusted into a pumping light spot with the radius of 400 μm, and the pumping light spot is focused on the end face of the crystal through the first 45-degree beam splitter and the mid-infrared parametric light output mirror;
the first 45-degree beam splitter is used for transmitting pump light and reflecting mid-infrared signal light and idler frequency light;
the intermediate infrared parametric light output mirror is used for transmitting pump light, reflecting 1084nm/1093nm fundamental frequency light and outputting intermediate infrared signal light and idler frequency light;
the mid-infrared parametric light total reflector is used for transmitting 1084nm/1093nm fundamental frequency light and reflecting mid-infrared signal light and idler frequency light;
the Nd is MgO, namely PPLN crystal is used as a gain medium and a frequency conversion medium for generating 1084nm/1093nm fundamental frequency light and mid-infrared parameter light;
the acousto-optic Q switch is used for enabling the fundamental frequency light to realize pulse operation;
the second 45-degree beam splitter is used for reflecting 1084nm fundamental frequency light and transmitting 1093nm fundamental frequency light;
the 1084nm fundamental frequency light total reflection mirror is placed on a reflection light path of the second 45-degree beam splitter;
the electro-optical crystal is placed between the second 45-degree beam splitter and the 1093nm fundamental frequency light total reflection mirror, and is used for improving the stimulated emission cross section of the 1093nm fundamental frequency light and realizing the programmable control of the intermediate infrared dual-wavelength time domain;
the 1093nm fundamental frequency light full-reflecting mirror is used for reflecting 1093nm fundamental frequency light.
Optionally, the 813nm semiconductor pump source has a wavelength of 813nm, a core radius of 200 μm and a numerical aperture of 0.22.
Optionally, the first 45-degree beam splitter is plated with a 813nm fundamental frequency light high-transmittance film, a signal light high-reflectance film and an idler frequency light high-reflectance film.
Optionally, the output mirror of the parametric oscillation cavity is a flat mirror, and is plated with a 1084nm/1093nm fundamental frequency light and signal light high-reflection film and an idler frequency light high-transmission film.
Alternatively, the Nd: MgO: PPLN crystal is cut by adopting an a-axis, and the crystal size is as follows: thickness x width x length 2mm x 6mm x 40mm, MgO doping concentration set at 5%, Nd3+The ion doping concentration is set to 0.4%, the polarization period length is set to 29.8 μm, and plating is performed at both endsThe optical fiber is provided with a pump light high-transmission film, a fundamental frequency light high-transmission film, a signal light high-transmission film and an idler frequency light high-transmission film.
Optionally, the parametric oscillation cavity total reflection mirror is a flat mirror, and is plated with a signal light and idler frequency light high reflection film and a 1084nm/1093nm fundamental frequency light high transmission film.
Optionally, the light-passing surface of the acousto-optic Q-switch is plated with a 1084nm/1093nm fundamental frequency light antireflection film.
Optionally, the second 45-degree beam splitter is plated with a 1084nm fundamental frequency light high-reflection film and a 1093nm fundamental frequency light high-transmission film.
Optionally, the electro-optic crystal is plated with a 1 μm laser antireflection film, and λ/4 voltage can be applied across the electro-optic crystal.
The invention also provides a pump source system which comprises the intermediate infrared dual-wavelength time domain programmable control laser based on the Nd, MgO and PPLN crystal.
The technical scheme provided by the invention has the beneficial effects that: the invention is based on the characteristics that the Nd, MgO, PPLN crystal has the phenomenon of dual-wavelength fundamental frequency light, ensures that the cavity type structural parameter designs of two fundamental frequency light resonant cavities in a straight cavity and a zigzag cavity are not interfered with each other while considering the integration compactness, ingeniously realizes the output of single-wavelength and dual-wavelength mid-infrared laser by utilizing the cooperation of two devices of the electro-optical effect of the electro-optical crystal and a zoom coupling mirror group, and realizes the time domain programmable regulation and control output of the mid-infrared and dual-wavelength by utilizing the characteristics of the acousto-optical crystal and the electro-optical crystal. The problem that the structure of the existing mid-infrared dual-wavelength laser is complex is solved while breaking through the defect that the traditional mid-infrared parametric oscillator cannot regulate and control a dual-wavelength time domain.
Drawings
Fig. 1 is a schematic structural diagram of a mid-infrared dual-wavelength time-domain programmable control laser based on an Nd: MgO: PPLN crystal according to an embodiment of the present invention.
In fig. 1, the structural components denoted by the respective reference numerals are:
1: 813nm semiconductor pump source; 2: an energy transmission optical fiber;
3: a zoom coupling lens barrel; 4: first 45 degree beam splitter
5: a mid-infrared parametric light output mirror; 6: MgO as Nd, PPLN crystal;
7: a mid-infrared parametric light total reflection mirror; 8: an acousto-optic Q switch;
9: a second 45 degree beam splitter; 10: an electro-optic crystal;
11: 1093nm fundamental frequency light total reflection mirror; 12: 1084nm fundamental frequency light total reflection mirror.
FIG. 2 is a diagram showing the distribution of the energy levels of a Nd: MgO: PPLN crystal according to an embodiment of the present invention.
FIG. 3 is a diagram illustrating an output relationship of mid-infrared dual wavelengths (T) according to an embodiment of the present invention1＝T2＝100μs)。
FIG. 4 is a diagram illustrating an output relationship of mid-infrared dual wavelengths (T) according to an embodiment of the present invention1＝T2＝300μs)。
Detailed Description
Hereinafter, exemplary embodiments of the disclosed embodiments will be described in detail with reference to the accompanying drawings so that they can be easily implemented by those skilled in the art. Also, for the sake of clarity, parts not relevant to the description of the exemplary embodiments are omitted in the drawings.
In the disclosed embodiments, it is to be understood that terms such as "including" or "having," etc., are intended to indicate the presence of the disclosed features, numbers, steps, behaviors, components, parts, or combinations thereof, and are not intended to preclude the possibility that one or more other features, numbers, steps, behaviors, components, parts, or combinations thereof may be present or added.
It should be further noted that the embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict. The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
Fig. 1 is a schematic structural diagram of a mid-infrared dual-wavelength time-domain programmable control laser based on an Nd: MgO: PPLN crystal according to an embodiment of the present invention, as shown in fig. 1, the laser includes a 813nm semiconductor pump source 1, an energy transfer fiber 2, a zoom coupling lens barrel 3, a first 45-degree beam splitter 4, a mid-infrared parametric light output mirror 5, a mid-infrared parametric light total reflection mirror 7, an Nd: MgO: PPLN crystal 6, an acousto-optic Q switch 8, a second 45-degree beam splitter 9, an electro-optic crystal 10, a 1093nm fundamental frequency light total reflection mirror 11, and a 1084nm fundamental frequency light total reflection mirror 12, where:
a 813nm semiconductor pump source 1, an energy transfer optical fiber 2, a zoom coupling mirror group 3, a first 45-degree beam splitter 4, a middle infrared parametric light output mirror 5, a middle infrared parametric light total reflection mirror 7, Nd, MgO, a PPLN crystal 6, an acousto-optic Q switch 8, a second 45-degree beam splitter 9, an electro-optic crystal 10 and a 1093nm fundamental frequency light total reflection mirror 11 are sequentially arranged on a horizontal optical path of the laser from left to right;
the 813nm semiconductor pump source 1 is used for emitting pump light;
the energy transmission optical fiber 2 is used for transmitting the pump light to the zoom coupling mirror group 3;
the zoom coupling mirror group 3 is used for adjusting the size of a pumping light spot focused on the crystal end face, for example, the pumping light can be adjusted to a pumping light spot with the radius of 400 μm, and the pumping light spot is focused on the crystal end face through the first 45-degree beam splitter 4 and the mid-infrared parametric light output mirror 5;
the first 45-degree beam splitter 4 is used for transmitting pump light and reflecting mid-infrared signal light and idler frequency light;
the intermediate infrared parametric light output mirror 5 is used for transmitting pump light, reflecting 1084nm/1093nm fundamental frequency light and outputting intermediate infrared signal light and idler frequency light;
the intermediate infrared parametric light total reflection mirror 7 is used for transmitting 1084nm/1093nm fundamental frequency light and reflecting intermediate infrared signal light and idler frequency light;
the MgO PPLN crystal 6 is used as a gain medium and a frequency conversion medium for generating 1084nm/1093nm fundamental frequency light and mid-infrared parametric light;
the acousto-optic Q switch 8 is used for enabling the fundamental frequency light to realize pulse operation;
the second 45-degree beam splitter 9 is used for reflecting 1084nm fundamental frequency light and transmitting 1093nm fundamental frequency light;
the 1084nm fundamental frequency light total reflection mirror 12 is placed on a reflection light path of the second 45-degree beam splitter 9;
the electro-optical crystal 10 is placed between the second 45-degree beam splitter 9 and the 1093nm fundamental frequency light total reflection mirror 11, and is used for improving the stimulated emission cross section of the 1093nm fundamental frequency light and realizing the programmable control of the intermediate infrared dual-wavelength time domain;
the 1093nm fundamental frequency light total reflection mirror 11 is used for reflecting 1093nm fundamental frequency light.
In one embodiment of the present invention, the 813nm semiconductor pump source 1 has a wavelength of 813nm, a core radius of 200 μm, and a numerical aperture of 0.22.
In an embodiment of the present invention, the first 45-degree beam splitter 4 is plated with a 813nm fundamental frequency light high-transmittance film, a signal light high-reflectance film and an idler frequency light high-reflectance film.
In an embodiment of the present invention, the output mirror 5 of the parametric oscillation cavity is a flat mirror, and is plated with a high reflective film for the fundamental frequency light and the signal light of 1084nm/1093nm and a high transparent film for the idler frequency light.
In one embodiment of the invention, the Nd: MgO: PPLN crystal 6 is cut by adopting an a-axis, and the crystal size is as follows: thickness x width x length 2mm x 6mm x 40mm, MgO doping concentration set at 5%, Nd3+The ion doping concentration is set to be 0.4%, the polarization period length is set to be 29.8 μm, and both ends of the Nd, MgO: PPLN crystal 6 are plated with pumping light and fundamental frequency light high-transmittance films and signal light and idler frequency light high-transmittance films, such as antireflection films for 813nm pumping light and 1080-. A parametric light resonant cavity, a 1093nm fundamental frequency light resonant cavity and a 1084nm fundamental frequency light resonant cavity are respectively built in a straight cavity and a zigzag cavity of a Nd: MgO: PPLN crystal 6, a zoom coupling mirror group 3, a first 45-degree beam splitter 4, a middle infrared parametric light output mirror 5, a middle infrared parametric light total reflection mirror 7, an acousto-optic Q-switch 8, a second 45-degree beam splitter 9, an electro-optic crystal 10 and a 1093nm fundamental frequency light total reflection mirror 11 are sequentially built in the straight cavity of the Nd: MgO: PPLN crystal 6, and a 1084nm fundamental frequency light total reflection mirror 12 is built in the zigzag cavity.
In an embodiment of the present invention, the parametric oscillation cavity total reflection mirror 7 is a flat mirror, and is plated with a signal light and idler frequency light high reflection film and a 1084nm/1093nm fundamental frequency light high transmission film.
In an embodiment of the present invention, a light-passing surface of the acousto-optic Q-switch 8 is plated with a 1084nm/1093nm fundamental frequency light antireflection film.
In an embodiment of the present invention, the second 45-degree beam splitter 9 is plated with a 1084nm fundamental frequency light high reflection film and a 1093nm fundamental frequency light high transmission film.
In an embodiment of the invention, the electro-optic crystal 10 is plated with a 1 μm laser antireflection film, and λ/4 voltage can be applied to both ends.
In an embodiment of the invention, the 1093nm resonator holophote 11 and the 1084nm resonator holophote 12 are planoconcave mirrors and are coated with 1084nm/1093nm high-reflectivity films.
In an embodiment of the present invention, the intermediate infrared parametric light output mirror 5, the intermediate infrared parametric light total reflection mirror 7 and the Nd: MgO: PPLN crystal 6 form a parametric light resonator.
In an embodiment of the present invention, the first 45-degree beam splitter 4, the parametric optical resonant cavity, the acousto-optic Q switch 8, the second 45-degree beam splitter 9, and the 1084nm fundamental frequency optical all-mirror 12 constitute a 1084nm fundamental frequency optical resonant cavity.
In an embodiment of the present invention, the first 45-degree beam splitter 4, the parametric optical resonant cavity, the acousto-optic Q switch 8, the second 45-degree beam splitter 9, the electro-optic crystal 10, and the 1093nm fundamental frequency optical total reflection mirror 12 form a 1093nm fundamental frequency optical resonant cavity.
Based on the technical scheme, the 813nm semiconductor pump source 1 emits pump light with a main peak wavelength absorbed by the Nd, MgO and PPLN crystal 6, the pump light penetrates through the energy transmission fiber 2, the zoom coupling mirror group 3 and the first 45-degree beam splitter 4 and then is focused into the Nd, MgO and PPLN crystal 6 from the left end to form a single-ended pump mode, the Nd, MgO and PPLN crystal 6 absorbs the pump light to form a particle number reversal, fundamental frequency light oscillation is formed under the continuous feedback action in the fundamental frequency light resonant cavity, fundamental frequency light with the wavelength of 1084nm is output in the 1084nm fundamental frequency light resonant cavity formed by the first 45-degree beam splitter 4, the parametric light resonant cavity, the acousto-optic Q switch 8, the second 45-degree beam splitter 9, the 1084nm fundamental frequency light all-reflecting mirror 12, and the first 45-degree beam splitter 4, the parametric light resonant cavity, the acousto-optic Q switch 8, the second 45-degree beam splitter 9, the first 45-degree beam splitter 9, the second 45-degree beam splitter 8, the acousto-optic Q switch 8, the second 45, The base frequency light with the wavelength of 1093nm is output from a 1093nm base frequency light resonant cavity formed by the electro-optical crystal 10 and the 1093nm base frequency light full-reflection mirror 11.
The fundamental frequency light simultaneously forms a pump to the Nd: MgO: PPLN crystal 6, and depends on the parametric light oscillation cavity total reflection mirror and the parametric lightThe design of an output mirror of the oscillation cavity and the design of the cavity length of the parametric light oscillation cavity ensure that the beam waist of the light spot of the oscillation parameter is superposed with the beam waist of the light spot of the fundamental frequency light and ensure that the size of the light spot of the oscillation parameter and the size of the light spot of the fundamental mode of the fundamental frequency light meet the matching of a corresponding focusing parameter xi (L/b), wherein L is Nd, MgO, the length of the PPLN crystal 6, and a confocal parameter b (2 pi n omega) is 2 pi n omega2And/lambda, wherein n is the refractive index of the corresponding laser, omega is the waist radius of the corresponding laser beam, and lambda is the wavelength of the corresponding laser, when the pumping power of the fundamental frequency light is higher than the oscillation starting threshold of the parametric light oscillation cavity, signal light which synchronously runs and stably oscillates is formed and mid-infrared band idler frequency light is correspondingly generated, and finally the parametric light is output through the parametric light oscillation cavity output mirror 5 and is refracted and output through the first 45-degree beam splitter 4.
FIG. 2 is a diagram showing an energy level distribution of a Nd: MgO: PPLN crystal according to an embodiment of the present invention, as shown in FIG. 2 (in FIG. 2, the energy value is in cm)-1Express), among the host crystals having a strong crystal field, Nd3+In ions4I11/2Showing a great energy level splitting. R2→4I11/2(Y2) and R2→4I11/2The (Y3) transition produces dual wavelength emissions of 1084nm and 1093nm, respectively. Estimated from the fluorescence intensity, pi polarization (5.1X 10) at room temperature-19cm2) The stimulated emission cross-section of (1.8X 10) is approximately sigma polarized- 19cm2) 2.8 times higher, which makes it difficult to achieve 1093nm laser oscillation. However, for the temperature sensitive ground state (4I11/2) The boltzmann distribution in (b) can cause vibration of population inversion density in these Stark splitting levels, and thus can realize a laser output of 1093 nm.
The ratio of the two fluorescence intensities is:
wherein E isi(i ═ 2,3) is the separation energy between the energy levels, kBIs the Boltzmann constant, T is the absolute temperature, C1Is a constant coefficient and can be estimated. According to the Fuchtbauer-Ladenbury formula, the effective stimulated emission cross section can be calculated as follows:
where I is the fluorescence intensity as a function of wavelength, I (λ) is the fluorescence intensity at wavelength λ, n is the material refractive index, c is the speed of light, τ is the radiative lifetime of the upper laser level, βjIs the branch ratio, for4F3/2→4I11/2The measured branch ratio was 0.44. The above formula shows thatλAnd I(λ)λ5Is in direct proportion. Therefore, the stimulated emission cross-section ratio Re can be expressed as:
wherein R represents a ratio of two fluorescence intensities. Therefore, the stimulated emission interface ratio of two spectral lines of 1093nm and 1084nm is a function of the temperature T, when the stimulated emission section ratio is less than 1, the output wavelength of the fundamental frequency light in the free running state is 1084nm, when the stimulated emission section ratio is more than 1, the output wavelength of the fundamental frequency light is 1093nm, and if the stimulated emission section ratio is not controlled, the output wavelength of the a-cut Nd: MgO: LN crystal is changed from 1084nm to 1093nm under a certain pumping power along with the increase of the crystal temperature.
When the electro-optical crystal is not loaded with voltage, 1084nm/1093nm fundamental frequency light exists at the same time, but only 1084nm fundamental frequency light participates in frequency conversion, and mid-infrared laser light generated by 1084nm fundamental frequency light is output. When the electro-optical crystal is loaded with voltage, the polarization direction of the 1093nm fundamental frequency light is changed, so that the 1093nm fundamental frequency light can also participate in frequency conversion, the gain of the 1093nm fundamental frequency light is higher than that of the 1084nm fundamental frequency light, and the output mid-infrared laser light is obtained by the frequency conversion of the 1093nm fundamental frequency light.
When the high-power pump is injected, the gain of 1093nm fundamental frequency light is larger than that of 1084nm fundamental frequency light, but 1093nm o-laser light cannot participate in optical parametric oscillation because the quasi-phase matching frequency conversion condition of e + e ═ e is not satisfied, and at the moment, although the gain of 1084nm fundamental frequency light is low, the o-laser light also can participate in optical parametric oscillation and outputs mid-infrared laser light generated by 1084nm fundamental frequency light, and under the condition, idle frequency light with the wavelength of 3.845 mu m is output.
When lambda/4 voltage is added to two ends of the electro-optical crystal, 1093nm fundamental frequency light has a larger stimulated emission cross section and higher gain under a high-power pumping mechanism, the 1093nm fundamental frequency light is incident to an Nd: MgO: PPLN crystal through a mid-infrared parametric light total reflection mirror, under the action of the 1093nm fundamental frequency light, mid-infrared idle frequency light with the oscillation wavelength of 3.935 mu m is synchronously generated after a parametric oscillation cavity reaches an oscillation starting threshold value, and the mid-infrared idle frequency light is output by an output mirror of the mid-infrared parametric light resonant cavity. When the lambda/4 voltage is removed and the voltage smaller than the lambda/4 voltage is added to the two ends of the electro-optical crystal, the 1093nm fundamental frequency light gradually disappears because gain cannot be obtained, at the moment, in the process of mode competition of 1084nm and 1093nm dual-wavelength, 1084nm fundamental frequency light obtains high gain, 1084nm fundamental frequency light participates in nonlinear frequency conversion and begins to synchronously generate oscillated mid-infrared dual-wavelength idler light with the wavelength of 3.845 mu m and 3.935 mu m, and the mid-infrared dual-wavelength idler light is output by an output mirror of the mid-infrared parametric optical resonant cavity.
The frequency interval is determined by the set repetition frequency of the acousto-optic Q-switch device, and the intermediate infrared dual-wavelength time domain programmable regulation and control based on Nd: MgO: PPLN crystal can be realized by adjusting the pressurization time of the electro-optic crystal. When the working frequency of the acousto-optic Q switch is set to 10KHz, the pulse interval is 100 mus, if the time of the loading voltage of the electro-optic crystal is T1Time of no voltage application is T2When T is1And T2Meanwhile, when the output is set to 100 μ s, the output rule of the mid-infrared dual-wavelength is as shown in FIG. 3, and the laser beams of 3.8 μm and 3.9 μm are alternately output. By changing the different times T1And T2I.e. the mid-infrared output wavelength can be programmed, e.g. by adjusting T1Set to 300. mu.s, T2The output relationship of the laser beams with the wavelengths of 3.8 μm and 3.9 μm is shown in FIG. 4 when the wavelength is set to 300. mu.s.
In conclusion, the invention aims to solve the problem that the infrared dual-wavelength laser in the infrared dual-wavelength time domain output cannot be freely regulated and controlled in the self-optical parametric oscillation process based on the Nd, MgO and PPLN crystal. The parametric optical resonant cavity and the 1084nm/1093nm fundamental frequency optical resonant cavity are respectively built in a straight cavity and a zigzag cavity of a crystal, single-wavelength mid-infrared and dual-wavelength mid-infrared free regulation and control switching output is carried out by adopting a mode of adjusting an electro-optical crystal and a zooming coupling mirror group, the programmable regulation and control of a mid-infrared dual-wavelength time domain is realized by adjusting the pressurizing time of the electro-optical crystal through the interval of controlling the frequency of an acousto-optical Q switch device, and the mid-infrared dual-wavelength laser with compact structure and function integration is realized while the application indexes are ensured.
Claims (10)
1. A mid-infrared dual-wavelength time domain programmable regulation laser based on Nd: MgO: PPLN crystal is characterized by comprising: a 813nm semiconductor pump source, an energy transmission optical fiber, a zoom coupling lens barrel, a first 45-degree beam splitter, a middle infrared parametric light output mirror, a MgO PPLN crystal, a middle infrared parametric light total reflection mirror, an acousto-optic Q switch, a second 45-degree beam splitter, an electro-optic crystal, a 1093nm fundamental frequency light total reflection mirror and a 1084nm fundamental frequency light total reflection mirror, wherein:
a 813nm semiconductor pump source, an energy transmission optical fiber, a zoom coupling lens group, a first 45-degree beam splitter, a middle infrared parametric light output mirror, a Nd, namely a PPLN crystal, a middle infrared parametric light total reflection mirror, an acousto-optic Q switch, a second 45-degree beam splitter, an electro-optic crystal and a 1093nm fundamental frequency light total reflection mirror are sequentially arranged on a horizontal optical path of the laser from left to right;
the 813nm semiconductor pump source is used for emitting pump light;
the energy transmission optical fiber is used for transmitting the pump light to the zoom coupling mirror group;
the zoom coupling mirror group is used for adjusting the size of a pumping light spot focused on the end face of the crystal, the pumping light can be adjusted into a pumping light spot with the radius of 400 mu m, and the pumping light spot is focused on the end face of the crystal through the first 45-degree beam splitter and the mid-infrared parametric light output mirror;
the first 45-degree beam splitter is used for transmitting pump light and reflecting mid-infrared signal light and idler frequency light;
the intermediate infrared parametric light output mirror is used for transmitting pump light, reflecting 1084nm/1093nm fundamental frequency light and outputting intermediate infrared signal light and idler frequency light;
the mid-infrared parametric light total reflector is used for transmitting 1084nm/1093nm fundamental frequency light and reflecting mid-infrared signal light and idler frequency light;
the Nd is MgO, namely PPLN crystal is used as a gain medium and a frequency conversion medium for generating 1084nm/1093nm fundamental frequency light and mid-infrared parameter light;
the acousto-optic Q switch is used for enabling the fundamental frequency light to realize pulse operation;
the second 45-degree beam splitter is used for reflecting 1084nm fundamental frequency light and transmitting 1093nm fundamental frequency light;
the 1084nm fundamental frequency light total reflection mirror is placed on a reflection light path of the second 45-degree beam splitter;
the electro-optical crystal is placed between the second 45-degree beam splitter and the 1093nm fundamental frequency light total reflection mirror, and is used for improving the stimulated emission cross section of the 1093nm fundamental frequency light and realizing the programmable control of the intermediate infrared dual-wavelength time domain;
the 1093nm fundamental frequency light full-reflecting mirror is used for reflecting 1093nm fundamental frequency light.
2. The laser of claim 1, wherein the 813nm semiconductor pump source has a wavelength of 813nm, a core radius of 200 μm, and a numerical aperture of 0.22.
3. The laser as claimed in claim 1 or 2, wherein the first 45-degree beam splitter is plated with 813nm fundamental frequency optical high-transmittance film, signal and idler frequency optical high-reflectance film.
4. The laser of claim 1, wherein the parametric oscillator cavity output mirror is a flat mirror coated with a 1084nm/1093nm fundamental and signal light high reflection film and an idler light high transmission film.
5. The laser of claim 1, wherein the Nd: MgO: PPLN crystal is cut with an a-axis, and has a crystal size: the thickness multiplied by the width multiplied by the length is 2mm multiplied by 6mm multiplied by 40mm, the polarization period length is set to be 29.8 mu m, and both ends are plated with pumping light and fundamental frequency light high-transmission films and signal light and idler frequency light high-transmission films.
6. The laser of claim 1, wherein the full-mirror of the parametric oscillation cavity is a flat mirror coated with a high-reflectivity film for signal light and idler light and a high-transmissivity film for 1084nm/1093nm fundamental light.
7. The laser as claimed in claim 1, wherein the pass surface of the acousto-optic Q-switch is coated with a 1084nm/1093nm fundamental frequency light anti-reflection film.
8. The laser as claimed in claim 1, wherein the second 45 degree beam splitter is plated with a 1084nm fundamental frequency light high reflection film and a 1093nm fundamental frequency light high transmission film.
9. The laser of claim 1, wherein the electro-optic crystal is coated with a 1 μm laser antireflection film and a λ/4 voltage is applied across it.
10. A pump source system comprising the mid-infrared two-wavelength time-domain programmable tunable laser based on a Nd: MgO: PPLN crystal according to any one of claims 1 to 9.
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| CN113314939B (en) * | 2021-05-27 | 2022-06-03 | 长春理工大学 | Multi-wavelength mid-infrared laser energy ratio regulation and control amplifier based on Nd-MgO-APLN crystal |
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| CN105591275B (en) * | 2016-03-07 | 2018-08-14 | 长春理工大学 | Based on MgO:The controllable electric field tuned optical parametric oscillator of PPLN domain duty ratios |
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