Optical parametric oscillator
阅读说明:本技术 光参量振荡器 (Optical parametric oscillator ) 是由 约翰·乔治·德什·奥努瓦 本杰明·希曼斯基 于 2019-02-27 设计创作,主要内容包括:本发明涉及双谐振光参量振荡器(1),包括具有二阶光学非线性并置于能反射泵浦波(2)的光腔(6)中的扇出晶体(5,55,105),晶体(5,55,105)包括光轴穿过的入射面(59)和出射面(60)、上面(57)和下面(58)。根据本发明的光参量振荡器(1)的主要特征为晶体(105)具有极性反转线(106)的网,极性反转线(106)分开且靠近地始于与晶体(105)上面(57)平行的上虚拟直线(61)并分开且彼此远离地结束于与晶体(105)下面(58)平行的下虚拟直线(63)或晶体入射面(59),且两相继线(106)彼此形成恒定角度,网从起始于晶体(105)出射面(60)并通过从出射面(60)发散而朝下虚拟直线(63)延伸的第一线(108)开始,所有其它线从第一线(108)向晶体(105)入射面(59)逐渐且单调倾斜。(The invention relates to a dual-resonant optical parametric oscillator (1) comprising a fan-out crystal (5, 55, 105) having a second order optical nonlinearity and arranged in an optical cavity (6) capable of reflecting a pump wave (2), the crystal (5, 55, 105) comprising an entrance face (59) and an exit face (60) through which an optical axis passes, an upper face (57) and a lower face (58). The main feature of the optical parametric oscillator (1) according to the invention is that the crystal (105) has a network of lines of polarity inversion (106), the lines of polarity inversion (106) starting separately and closely from an upper virtual straight line (61) parallel to the upper face (57) of the crystal (105) and ending separately and far away from each other at a lower virtual straight line (63) or at the crystal entrance face (59) parallel to the lower face (58) of the crystal (105), and the two successive lines (106) forming a constant angle with each other, the network starting from a first line (108) starting at the crystal (105) exit face (60) and extending towards the lower virtual straight line (63) by diverging from the exit face (60), all other lines being gradually and monotonically inclined from the first line (108) towards the crystal (105) entrance face (59).)
1. An optical parametric oscillator (1) of the double resonance type, comprising a crystal (5, 55, 105) of the fan-out type, said crystal (5, 55, 105) having a second order optical nonlinearity and being placed in an optical cavity (6) capable of reflecting a pump wave (2), said crystal (5, 55, 105) comprising an entrance face (59) and an exit face (60), an upper face (57) and a lower face (58), with an optical axis passing through said entrance face (59) and said exit face (60), characterized in that said crystal (105) comprises a grid of lines of polarity inversion (106), said lines of polarity inversion (106) starting separately and with a narrow spacing from an upper virtual straight line (61) parallel to said upper face (57) of said crystal (105) and ending separately and with a wide spacing from a lower virtual straight line (63) parallel to said lower face (58) of said crystal (105) or ending at said entrance face (59) of said crystal (105), and two successive lines (106) forming a constant angle between each other, the grid starting from a first line (108), the first line (108) starting from the exit face (60) of the crystal (105) and extending towards the lower virtual straight line (63) while diverging from the exit face (60), all the other lines being progressively and monotonically inclined from the first line (108) towards the entrance face (59) of the crystal (105).
2. An optical parametric oscillator according to claim 1, characterized in that the four faces (57, 58, 59, 60) of the crystal (105) are planar.
3. An optical parametric oscillator according to any of claims 1 and 2, characterized in that the upper face (57) and the lower face (58) are parallel and the entrance face (59) and the exit face (60) are parallel.
4. An optical parametric oscillator according to any one of claims 1 to 3, characterized in that the polarity-reversal line (106) is located immediately after the first line (108) and the first line (108) also ends at the lower virtual straight line (63), and the following lines (106) all end at the entrance face (59).
5. An optical parametric oscillator according to any of claims 1 to 4, characterized in that the constant angle of tilt between two consecutive lines (106) is about 0.1 mrad.
6. An optical parametric oscillator according to any of claims 1 to 5, characterized in that the crystal (105) is made of lithium niobate.
7. The optical parametric oscillator according to any one of claims 1 to 6, wherein the grating comprises an original line (109) placed before the first line (108), and the original line (109) starts at the exit face (60) and ends at the lower virtual straight line (63) below the upper virtual straight line (61).
8. An optical parametric oscillator according to any one of claims 1 to 7, wherein the first line (108) is inclined at an angle greater than or equal to the constant angle with respect to the exit face (60) so as to separate two successive lines (106).
9. A crystal for manufacturing an optical parametric oscillator according to any one of claims 1 to 8, the crystal (5, 55, 105) comprising an entrance face (59) and an exit face (60), an upper face (57) and a lower face (58), an optical axis passing through the entrance face (59) and the exit face (60), characterized in that the crystal (105) comprises a grid of polarity-reversing lines (106), the polarity-reversing lines (106) starting separately and in a narrowly spaced manner from an upper virtual straight line (61) parallel to the upper face (57) of the crystal (105) and ending separately and in a widely spaced manner from a lower virtual straight line (63) parallel to the lower face (58) of the crystal (105) or ending at the entrance face (59), and two successive lines (106) forming a constant angle between each other, the grid starting from a first line (108), the first line (108) starts at the exit face (60) of the crystal (105) and extends towards the lower virtual straight line (63) while diverging from the exit face (60), all other lines being gradually and monotonically inclined from the first line (108) towards the entrance face (59) of the crystal (105).
Technical Field
The present invention relates to an optical parametric oscillator.
Background
An Optical Parametric Oscillator (OPO) is a frequency converter that operates from an angular frequency ofThe laser wave (pump wave) generates angular frequencies of
Andtwo new waves called "signal wave" and "idler wave", so thatParametric frequency conversion is obtained by propagating a pump wave through a second-order optically nonlinear component, typically a crystal. If a physical parameter of the crystal is modified, such as the temperature, the angle with respect to the pump radiation or even the periodicity of the ferroelectric domains (e.g. periodic domain inversion in the case of crystals such as lithium niobate) the values can be adjusted within a very wide rangeAnd
thus, OPO is a coherent light source that can be tuned over a very wide and much wider spectral range than lasers. This important feature opens up many fields of application for OPO, such as spectroscopic analysis of gases.
Disclosure of Invention
The optical parametric oscillator according to the present invention is a cavity-in-line optical parametric oscillator (NesCOPO), i.e. based on the OPO of two separate resonant cavities, each of which exhibits resonance at one of the wavelengths generated by second order parametric conversion. This OPO is a double resonance type with double pass of the pump wave.
European patent application EP2503387 describes a NesCOPO parametric oscillator that employs a continuously variable pitch lithium niobate fan-out crystal. The disadvantages of such an oscillator are: including crystals whose ferromagnetic domains are not optimally oriented, which results in a wave number that the source cannot emit without changing parameters (e.g., the temperature of the crystal).
The optical parametric oscillator according to the invention comprises a crystal whose ferromagnetic pattern has been optimized to provide for the adoption of the entire desired wavelength range without having to modify certain crystal-related parameters, such as temperature.
The terms "upper", "lower", "front" and "rear" must be interpreted as if the crystal were placed in an operational position in the optical cavity of the optical parametric oscillator.
An object of the present invention is an optical parametric oscillator of a double resonance type, which includes a fan-out type crystal having second-order optical nonlinearity and disposed in an optical cavity capable of reflecting a pump wave, the crystal including an incident surface and an exit surface, an upper surface and a lower surface, and an optical axis passing through the incident surface and the exit surface.
The optical parametric oscillator according to the present invention is mainly characterized in that the crystal comprises a grid of polarity-inverted lines, the polarity-inverted lines starting separately and at narrow intervals from an upper virtual straight line parallel to the upper face of the crystal and ending separately and at wide intervals from a lower virtual straight line parallel to the lower face of the crystal or from the entrance face of the crystal, two successive lines forming a constant angle between each other, the grid starting from a first line, the first line starting from the exit face of the crystal and extending towards a lower virtual straight line while diverging from the exit face, all other lines being gradually and monotonically inclined from the first line towards the entrance face of the crystal.
In other words, a first line of the grid starts at and diverges from the exit face of the crystal, and all other lines are inclined from this first line towards the entrance face of the crystal in a manner that increasingly diverges from the exit face. The first line is the only one starting from the exit face, all other lines of the grid being away from the exit face. In other words, the grid of lines gives the impression that it rotates from the exit face of the crystal towards the entrance face of the crystal, starting with the first line having only one point of contact with the exit face of the crystal. It is noted that all lines of the grid start from the upper virtual straight line, including the first polarity-reversing line.
Advantageously, the four faces of the crystal are planar.
Preferably, the upper and lower faces are parallel, and the entrance face and the exit face are parallel. In this way, the crystal is parallelepiped-shaped with a small thickness.
Preferably, the polarity-reversing line is located immediately after the first line and the first line also ends at the lower virtual straight line, and the subsequent lines all end at the incident surface. The expression "end at the entrance face" must be understood to mean "present at the entrance face".
Advantageously, the constant angle of inclination between two successive wires is about 0.1 mrad. The expression "about 0.1 mrad" means equal to 0.1mrad +/-0.05 mrad.
Preferably, the crystal is made of lithium niobate. This material is particularly, but not exclusively, suitable for an optical parametric oscillator according to the invention.
Preferably, the grid comprises an original line placed before the first line, said original line starting from the exit face below the upper virtual straight line and ending at the lower virtual straight line.
Advantageously, the first line is inclined at an angle greater than or equal to a constant angle with respect to the exit face, so as to separate two successive lines. The angle of inclination is preferably between 1 and 2 times the constant angle of inclination between two successive lines of the grid.
Another object of the present invention is a crystal for manufacturing an optical parametric oscillator according to the present invention, the crystal comprising an entrance face and an exit face, an upper face and a lower face, an optical axis passing through the entrance face and the exit face.
The crystal according to the invention is primarily characterized in that it comprises a grid of lines of polarity inversion starting at narrowly spaced intervals from an upper virtual straight line parallel to the upper face of the crystal and ending at widely spaced intervals at a lower virtual straight line parallel to the lower face of the crystal or at the entrance face of the crystal, two successive lines forming a constant angle between each other, the grid starting from a first line starting at the exit face of the crystal and extending towards the lower virtual straight line, all other lines being gradually and monotonically inclined from the first line towards the entrance face of the crystal.
The optical parametric oscillator according to the present invention has the following advantages: each wavenumber in a given wavelength range can be obtained, eliminating the unusable area observed with the existing optical parametric vibrators. This achievement is obtained with a specific design of the polarity inversion line of the grid, thus allowing to avoid the need to set the crystal temperature.
Drawings
A detailed description of an optical parametric oscillator according to the present invention is given below with reference to the following drawings:
figure 1 is a schematic diagram of a prior art optical parametric oscillator,
figure 2 is a front view of a fan-out crystal used in a prior art optical parametric oscillator,
FIG. 3 is a graph showing an example of the achievable wavenumber as a function of the position of the crystal of FIG. 2 in the optical cavity in a prior art OPO,
FIG. 4 is a front view of a fan-out crystal according to the invention,
fig. 5 is a graph showing an example of the achievable wavenumber as a function of the position of the crystal of fig. 4 in the optical cavity.
Detailed Description
In the remainder of the description, the terms "OPO" and "optical parametric oscillator" are equivalent.
Referring to fig. 1, an optical parametric oscillator 1 is a system that allows a pump wave 2 generated by a laser beam to be converted into two waves, a "signal" wave 3 and an "idler" wave 4, by a nonlinear crystal 5 (which may be made of lithium niobate, for example). The crystal 5 is placed in an
The architecture of the OPO 1 according to the invention is also referred to by the abbreviation NesCOPO (nested cavity) optical parametric oscillator). The pump wave 2 has an incident component 8 originating from the first mirror M1 and a reflected component 9 obtained after reflection of said incident wave 8 from the second mirror M3 of the
The OPO 1 according to the present invention utilizes a non-linear frequency conversion within a crystal 5 placed in an
Referring to fig. 2, a conventional fan-out
-an
a planar
a
a
two rectangular and
Such a
The
In summary, the grid of
The pump wave 2 (the beam size of which may be, for example, about 100 μm) reaches the
Now, referring to fig. 3, with such a fan-out
There are currently methods of avoiding these
The OPO according to the invention comprises a
Referring to fig. 4, the
In other words, the grid of lines of
The grid further comprises an
In summary, in the
A typical period of the pattern in the
Referring to fig. 5, the OPO according to the invention allows to obtain all wavelengths within a given range by translating the
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