CN115390181A - A long-wavelength mid-infrared on-chip integrated optical parameter conversion device - Google Patents

Abstract

The invention discloses a long-wavelength mid-infrared on-chip integrated optical parameter conversion device: it includes a substrate and a beam focusing lens, a non-oxide crystal waveguide, and a beam collecting lens arranged sequentially from left to right on the substrate; A quartz substrate is arranged between the crystal waveguide and the base; the non-oxide crystal waveguide and the quartz substrate are glued and connected by ultraviolet glue. The present invention realizes the generation of low-threshold, high-efficiency long-wavelength mid-infrared laser with the aid of an on-chip mid-infrared optical parameter conversion device based on a nonlinear crystal waveguide. Its simple structure and easy-to-integrate characteristics can further promote the development of mid-infrared lasers. application and development.

Description

A long-wavelength mid-infrared on-chip integrated optical parameter conversion device

technical field

The invention relates to the field of laser technology, in particular to a long-wavelength mid-infrared on-chip integrated optical parameter conversion device.

Background technique

At present, long-wavelength mid-infrared laser on-chip integrated devices with a wavelength of more than 4 μm mainly include laser waveguide structures centered on silicon germanium materials, chalcogenide glass, aluminum nitride, etc. However, due to the characteristics of the materials themselves, the on-chip Most integrated devices are based on the third-order nonlinearity of materials to generate mid-infrared lasers, which are usually inefficient, and require necessary and time-consuming dispersion management and relatively complex waveguide design.

The parametric down-conversion technology based on the second-order nonlinearity of nonlinear crystals is another technical means to generate mid-infrared lasers at this stage. The realization of optical parameter conversion requires the help of nonlinear crystals and some new types of periodically polarized crystals. Usually, it is only necessary to select the appropriate crystal and the frequency of the incident laser to achieve mid-infrared laser output in any band. However, most of these optical parametric conversion devices currently use bulk crystals to generate mid-infrared lasers, and require strict and complex optical path settings, resulting in redundant structures and bulky volumes; at the same time, the pumping threshold is high and the conversion efficiency is low. Therefore, designing and implementing an on-chip integrated device based on the second-order nonlinearity of nonlinear crystals to generate low-threshold and high-efficiency mid-infrared lasers has always been the focus of researchers. Currently, only on-chip integrated devices based on lithium niobate crystals are available. However, limited by the transparent window of lithium niobate crystal, its output wavelength is still limited within 4 μm. The transparent window of non-oxide crystals can reach more than 10 μm. Therefore, it is an urgent problem to realize the on-chip integrated device of this type of crystals to generate high-efficiency long-wavelength mid-infrared lasers.

On the other hand, in order to achieve high-efficiency long-wavelength mid-infrared laser output above 10 μm, the waveguide size based on non-oxide crystals should generally be on the order of μm, and traditional photolithography techniques (wet etching, ion beam etching, plasma It will take a long time to manufacture this type of laser crystal waveguide, and considering the specificity of the material structure of many non-oxide crystals, traditional photolithography technology will not be able to achieve universal application.

Based on the above, it is of great significance to explore and realize the on-chip integrated device based on non-oxide crystals to realize the output of long-wavelength mid-infrared laser.

Contents of the invention

In view of the above problems, the present invention provides a long-wavelength mid-infrared on-chip integrated optical parameter conversion device, based on laser direct writing technology, which overcomes the complex structure, high threshold value and low conversion efficiency of existing long-wavelength mid-infrared optical parameter conversion devices. defect.

The present invention adopts following technical scheme:

A long-wavelength mid-infrared on-chip integrated optical parameter conversion device, including a substrate and a beam focusing lens, a non-oxide crystal waveguide, and a beam collecting lens arranged sequentially from left to right on the substrate; the non-oxide crystal waveguide and the substrate A quartz substrate is arranged between;

The beam focusing lens is used to converge the incident light to form a focused spot; the non-oxide crystal waveguide is used to realize the optical parameter conversion based on the incident light; the beam collecting lens is used to collect the generated long-wavelength mid-infrared signal collecting; the quartz substrate is used to support the non-oxide crystal waveguide; the base is used to support the entire device, thereby forming a highly integrated on-chip mid-infrared optical parameter conversion device.

The beam focusing lens is a CaF ₂ lens with a focal length of 40 mm, without coating, and its transmission range is 0.8-8 μm. The non-oxide crystal waveguide is a phosphorus-germanium-zinc crystal waveguide, and two beams of light with different wavelengths can achieve frequency difference on the basis of time coincidence. The beam collecting lens is a ZnSe lens with a focal length of 15 mm.

Further, the non-oxide crystal waveguide and the quartz substrate are glued and connected by ultraviolet glue.

Further, the non-oxide crystal waveguide is a strip waveguide or a ridge waveguide.

Further, the width of the strip waveguide is 20-40 μm, and the height is 30-60 μm; the width of the upper surface of the ridge waveguide is 20-40 μm, the width of the lower surface is 30-50 μm, and the height is 30-60 μm.

Further, both sides of the light beam collecting lens are coated with 2-13 μm anti-reflection coating.

Further, the preparation method of the non-oxide crystal waveguide:

S1. Coarsely grind and finely grind the fixed non-oxide crystals on a high-speed rotating mechanical grinding disc to form sub-hundred-micron non-oxide crystal flakes;

S2. Form a specific waveguide shape on a non-oxide crystal sheet by direct writing with a femtosecond laser.

The beneficial effects of the present invention are:

In the present invention, a non-oxide crystal waveguide is produced by using the universal laser direct writing technology, and a highly integrated and miniaturized on-chip long-wavelength optical parameter conversion device with a low threshold and high efficiency above 4 μm is realized for the first time. The invention adopts the universal non-linear waveguide preparation technology based on femtosecond laser direct writing, quickly and efficiently prepares sub-hundred-micron waveguide structure, and uses this structure in the long-wavelength mid-infrared light parametric conversion process, thereby realizing long-term Wavelength mid-infrared laser generation. Compared with traditional parameter conversion devices, the device is easy to realize on-chip integration and has a simple structure. Compared with the traditional on-chip devices with silicon germanium materials as the core, this device benefits from the stronger second-order nonlinear characteristics and action principle of the crystal itself, which realizes a simple structure design and can generate mid-infrared lasers with high efficiency.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description only relate to some embodiments of the present invention, rather than limiting the present invention .

Fig. 1 is a schematic diagram of the present invention;

Fig. 2 is the spectrogram of the 2.4 μm laser of the embodiment of the present invention;

Fig. 3 is the spectrogram of the 3.8 μm laser of the embodiment of the present invention;

4 is a schematic cross-sectional view of a non-oxide crystal waveguide according to an embodiment of the present invention;

Fig. 5 is a cross-sectional light field distribution diagram of a phosphorus-germanium-zinc waveguide structure in an embodiment of the present invention;

Fig. 6 is the spectrum of the mid-infrared laser generated through the difference frequency action in the embodiment of the present invention;

Fig. 7 is the input-output curve of the mid-infrared laser produced in the embodiment of the present invention;

FIG. 8 is a schematic diagram of the process of fabricating a non-oxide crystal waveguide in an embodiment of the present invention.

In the picture:

1-beam focusing lens, 2-non-oxide crystal waveguide, 3-beam collecting lens, 4-ultraviolet glue, 5-quartz substrate, 6-substrate.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the following will clearly and completely describe the technical solutions of the embodiments of the present invention in conjunction with the drawings of the embodiments of the present invention. Apparently, the described embodiments are some, not all, embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the usual meanings understood by those skilled in the art to which the present disclosure belongs. The words "comprising" or "comprising" and similar words used in the present disclosure mean that the elements or things appearing before the word include the elements or things listed after the word and their equivalents, without excluding other elements or things. "Up", "Down", "Left", "Right" and so on are only used to indicate the relative positional relationship. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

As shown in Figure 1, a long-wavelength mid-infrared on-chip integrated optical parameter conversion device: including a substrate 6 and a beam focusing lens 1, a non-oxide crystal waveguide 2, and a beam collecting lens 3 arranged in sequence from left to right on the substrate 6 A quartz substrate 5 is provided between the non-oxide crystal waveguide 2 and the base 6; the non-oxide crystal waveguide 2 and the quartz substrate 5 are glued and connected by ultraviolet glue 4 .

The beam focusing lens 1 is used to converge the incident light to form a focused spot; the non-oxide crystal waveguide 2 is used to realize the optical parameter conversion based on the incident light; the beam collecting lens 3 is used to collect the generated long wavelength The mid-infrared signal is collected; the quartz substrate 5 is used to support the non-oxide crystal waveguide 2; the substrate 6 is used to support the entire device, thereby forming a highly integrated on-chip mid-infrared optical parameter conversion device.

The beam focusing lens 1 is a CaF2 lens with a focal length of 40 mm, uncoated, and its transmission range is 0.8-8 μm. The non-oxide crystal waveguide 2 is a phosphorus-germanium-zinc crystal waveguide. Basically, the difference frequency can be realized. The beam collecting lens 3 is a ZnSe lens with a focal length of 15 mm. Both sides of the light beam collecting lens 3 are coated with 2-13 μm anti-reflection coating.

In this embodiment, lasers with wavelengths of 2.4 μm and 3.8 μm are selected as the incident light, the pulse width is 250 fs, and the repetition frequency is 500 kHz, as shown in Figure 2 and Figure 3 respectively: the spectrum diagram of the 2.4 μm laser, and its center wavelength is 2410 nm , the 3dB bandwidth is 100nm; the spectrum of the 3.8μm laser has a central wavelength of 3750nm and a 3dB bandwidth of 476nm.

The non-oxide crystal waveguide 2 is a strip waveguide or a ridge waveguide.

The width of the strip waveguide is 20-40 μm, and the height is 30-60 μm; the width of the upper surface of the ridge waveguide is 20-40 μm, the width of the lower surface is 30-50 μm, and the height is 30-60 μm.

The non-oxide crystal waveguide 2 in this embodiment is a ridge waveguide, the cross section of which is shown in Figure 4, the width of the upper surface of the waveguide is 27 μm, the width of the lower surface is 42 μm, and the height of the waveguide is 37 μm.

The cross-sectional light field distribution diagram of the phosphorus-germanium-zinc crystal waveguide structure is shown in Figure 5. It can be seen that the mid-infrared light with a wavelength of 6.7 μm can be well confined in the waveguide structure.

The spectrum of the mid-infrared laser generated by the difference frequency is shown in Figure 6. It can be seen that 2.4 μm and 3.8 μm are in the phosphorus-germanium-zinc crystal waveguide structure, and after the difference frequency conversion, the long-wavelength mid-infrared of 6-9 μm can be realized. Laser output.

The input-output curve of the mid-infrared laser produced by this embodiment is shown in Figure 7, the abscissa value in the figure does not consider the coupling efficiency, and the coupling efficiency is 6.7%. The waveguide's on-chip mid-infrared laser generation device considers the coupling efficiency threshold to be only 2nJ, corresponding to a peak power of only 8kW.

The preparation method of the non-oxide crystal waveguide 2 is shown in Figure 8:

S1. Roughly grind and finely grind the non-oxide crystals fixed on the quartz substrate 5 through ultraviolet glue 4 on a high-speed rotating mechanical grinding disc to form sub-hundred-micron non-oxide crystal flakes;

S2. Form a specific waveguide shape on a non-oxide crystal sheet by direct writing with a femtosecond laser.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, may use the technical content disclosed above to make some changes or modify them into equivalent embodiments with equivalent changes. Technical Essence of the Invention Any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solutions of the present invention.

Claims (6)

1. A long-wavelength mid-infrared on-chip integrated optical parameter conversion device, characterized in that it comprises a substrate (6) and a beam focusing lens (1) arranged sequentially from left to right on the substrate (6), a non-oxide crystal waveguide (2), beam collecting lens (3); a quartz substrate (5) is arranged between the non-oxide crystal waveguide (2) and the substrate (6); The beam focusing lens (1) is a CaF ₂ lens with a focal length of 40 mm; the non-oxide crystal waveguide (2) is a phosphorous germanium zinc crystal waveguide; the beam collecting lens (3) is a ZnSe lens with a focal length of 15 mm. 2. A long-wavelength mid-infrared on-chip integrated optical parameter conversion device according to claim 1, characterized in that an ultraviolet glue (4) is passed between the non-oxide crystal waveguide (2) and the quartz substrate (5) glued connection. 3. The long-wavelength mid-infrared on-chip integrated optical parameter conversion device according to claim 1, characterized in that the non-oxide crystal waveguide (2) is a strip waveguide or a ridge waveguide. 4. A long-wavelength mid-infrared on-chip integrated optical parameter conversion device according to claim 3, wherein the width of the strip waveguide is 20-40 μm, and the height is 30-60 μm; the upper surface of the ridge waveguide The width is 20-40 μm, the width of the lower surface is 30-50 μm, and the height is 30-60 μm. 5 . The long-wavelength mid-infrared on-chip integrated optical parameter conversion device according to claim 1 , characterized in that, both sides of the beam collecting lens ( 3 ) are coated with 2-13 μm anti-reflection coatings. 5 . 6. A long-wavelength mid-infrared on-chip integrated optical parameter conversion device according to claim 1, characterized in that, the preparation method of the non-oxide crystal waveguide (2): S1. Coarsely grind and finely grind the fixed non-oxide crystals on a high-speed rotating mechanical grinding disc to form sub-hundred-micron non-oxide crystal flakes; S2. Form a specific waveguide shape on a non-oxide crystal sheet by direct writing with a femtosecond laser.

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