CN116380244A - Echelle grating spectrometer based on cross dispersion principle and preparation method thereof - Google Patents
Echelle grating spectrometer based on cross dispersion principle and preparation method thereof Download PDFInfo
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Abstract
The invention discloses an echelle grating spectrometer based on a cross dispersion principle and a preparation method thereof. The spectrometer comprises a main dispersion element, a transverse dispersion element, an area array detector, an optical fiber and a slit, wherein the main dispersion element is an echelle bending grating; the transverse dispersion element is a small-step bending grating, and the combination of the middle-step bending grating and the small-step bending grating realizes light splitting and point-to-point aberration elimination imaging; the area array detector is arranged in the emergent light direction; the optical fiber is used for emitting light to be measured; the slit is located behind the fiber and acts as an aperture stop. The invention uses the echelle bending grating and the small echelle bending grating to mutually cooperate for cross dispersion, does not need a collimation and focusing reflecting mirror in the traditional structure, has compact structure, can realize high-resolution detection, and solves the problems of more elements, high cost and complex assembly in the traditional cross dispersion echelle grating structure.
Description
Technical Field
The invention relates to the technical field of spectrum analysis instruments, in particular to an echelle grating spectrometer based on a cross dispersion principle and a preparation method thereof.
Background
The existing micro-spectrometers are generally designed based on a Cherny-Techner structure or a Roland round concave grating structure, which cannot realize high resolution and broadband detection at the same time.
The echelle grating spectrometer structure can realize high dispersion and can obtain a wide detection range. The method uses an echelle grating as a main dispersion element, uses a prism with low dispersion or a small echelle grating to realize transverse dispersion, uses an area array detector to collect a two-dimensional spectrum image formed on an image plane, and finally obtains complete spectrum information through data processing. The prior art generally requires the use of a large number of components including collimating mirrors, focusing mirrors, primary and transverse dispersive elements, etc. The collimating and focusing mirrors increase the number of components, increase the volume, increase the cost on the one hand, and limit the possibility of integrating echelle grating structures on the chip on the other hand, thus not being mass-producible.
In general, there are two main configurations of existing cross-dispersion spectrometers. The first is a cross dispersion light path using echelle grating as main dispersion element and prism as auxiliary dispersion element. When the prism is used as the transverse dispersion element, the problems of blaze and cascade overlapping do not exist, so that the efficiency is higher. However, the prism has a large volume, which is disadvantageous for miniaturization of the device. The second is a structure using echelle grating as main dispersion element and low line density grating as transverse dispersion element. The grating is used as a transverse dispersion element, so that larger order separation can be obtained, and the operating wavelength range is wider. But requires etching into a small step profile to increase diffraction efficiency. Both of the above methods require collimating and focusing mirrors or lenses to achieve imaging, and therefore the number of components is large, the cost is high, and the assembly is complex.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems in the related art to some extent.
Therefore, the embodiment of the invention provides an echelle grating spectrometer based on the principle of cross dispersion and a preparation method thereof.
The invention provides an echelle grating spectrometer based on a cross dispersion principle, which comprises:
the main dispersion element is an echelle bending grating;
the transverse dispersion element is a echelle bending grating, and the optical splitting and point-to-point aberration elimination imaging are realized through the combination of the echelle bending grating and the echelle bending grating;
the area array detector is arranged in the emergent light direction;
the optical fiber is used for emitting light to be measured;
and a slit positioned behind the optical fiber, the slit functioning as an aperture stop.
In some embodiments, the echelle curved grating and the echelle curved grating are both planar gratings, the echelle curved grating having a lower ruling density than the echelle curved grating, the echelle curved grating operating with a higher diffraction order than the echelle curved grating.
In some embodiments, the reticle distribution of the echelle curved grating and the echelle curved grating is obtained by numerical simulation, the reticle distribution including pitch and curved shape of the reticle.
In some embodiments, the primary dispersive element is placed in the direction of the incident light after passing through the slit, and the primary dispersive element center is aligned with the optical fiber and the slit center height, the lateral dispersive element is placed in the direction of the diffracted light, and the lateral dispersive element center height is aligned with the optical axis height of the diffracted light.
In some embodiments, after the light to be measured sent by the optical fiber passes through the slit, the light to be measured irradiates the main dispersive element, the light is dispersed in the main direction to separate different wavelengths, and then the light is dispersed in the transverse direction to separate different diffraction orders by the transverse dispersive element, and the transverse dispersive element cooperates with the main dispersive element to focus the light in the meridian and sagittal directions onto the area array detector to obtain a two-dimensional dispersion spectrogram of the light source to be measured.
In some embodiments, the lateral dispersive element is placed in the direction of the incident light after passing through the slit, and the lateral dispersive element center is aligned with the optical fiber and the slit center height, and the primary dispersive element is placed in the direction of the diffracted light, and the primary dispersive element center height is aligned with the optical axis height of the diffracted light.
In some embodiments, the light to be measured emitted by the optical fiber passes through the slit and then irradiates onto the transverse dispersion element, the light is dispersed in the transverse direction to separate different diffraction orders, and then the light is diffracted by the main dispersion element to form a two-dimensional cross dispersion light beam, and the main dispersion element cooperates with the transverse dispersion element to focus the light in the meridian and sagittal directions onto the area array detector to obtain a two-dimensional dispersion spectrogram of the light source to be measured.
In some embodiments, the medium of the spectrometer is air or a glass material.
The invention provides a preparation method of an echelle grating spectrometer based on a cross dispersion principle, which comprises the following steps:
uniformly coating, exposing and developing on a substrate to obtain a curved reticle grating mask pattern;
transferring the mask pattern of the curved reticle grating to a substrate through etching, sputtering metal to form a metal reflecting film, and respectively preparing an echelle curved grating and a small echelle curved grating;
when the medium of the spectrometer is air, fixing and fine-adjusting the echelle bending grating, the small echelle bending grating and the area array detector by using corresponding fixtures;
when the medium of the spectrometer is glass, the echelle bending grating and the small echelle bending grating are respectively consistent with the corresponding surfaces of the corresponding glass blocks in size, the echelle bending grating and the glass blocks are fixedly connected through ultraviolet glue, and the small echelle bending grating and the glass blocks are fixedly connected through ultraviolet glue;
when the spectrometer with the glass medium is processed into a chip, firstly, the thickness and the area of the glass chip are determined, then, the echelle bending grating and the echelle bending grating are designed on the same surface, and two grating patterns are formed simultaneously through one-time photoetching.
In some embodiments, the exposure mode is one of electron beam lithography, ultraviolet exposure, laser direct writing or nanoimprint, the etching mode is dry etching or wet etching, and the metal sputtering mode is magnetron sputtering or electron beam evaporation.
Compared with the prior art, the invention has the beneficial effects that:
the invention uses the inter-matching of the echelle curved grating and the echelle curved grating to carry out cross dispersion, has simple structure, does not need a collimation and focusing reflecting mirror in the traditional structure, has compact structure, can realize high resolution detection, and solves the problems of more elements, high cost and complex assembly in the traditional cross dispersion echelle grating structure.
The spectrometer of the invention only needs one main dispersive curved reticle grating and one transverse dispersive curved reticle grating besides the incident optical fiber and the detector. Compared with the traditional structure, the collimating mirror and the focusing mirror are omitted, so that the structure is simple, the cost is low, and the integration level is high.
The light-splitting elements used in the invention are all plane gratings, and can be realized by micro-nano processing means, so that the cost is low and the light-splitting elements can be manufactured in a large scale.
The invention changes the grid line distribution of the two curved line gratings to match with each other, thereby playing the roles of eliminating aberration and improving resolution.
The invention can be expanded into an integrated structure of a glass medium micro spectrometer and a chip spectrometer.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a cross-dispersion high-resolution spectrometer with first lateral dispersion followed by principal direction dispersion;
FIG. 2 is a schematic diagram of a cross-dispersion high-resolution spectrometer with primary direction dispersion followed by lateral dispersion;
FIG. 3 is a schematic diagram of a glass medium micro spectrometer;
FIG. 4 is a schematic diagram of a dual curved reticle grating cross-dispersion high resolution chip spectrometer;
FIG. 5 is a schematic illustration of an echelle curved reticle grating;
FIG. 6 is a simulated structural overall light path diagram;
FIG. 7 is a two-dimensional spot diagram on a simulated image plane;
FIG. 8 is a simulated two wavelengths of the interval 80 pm;
FIG. 9 is an illustration of the echelle grating diffraction efficiency of the Rsoft simulation;
fig. 10 shows the Zemax simulated analog area array CCD imaging effect.
Fig. 11 is a schematic diagram showing a comparison of a normal straight reticle grating and a curved reticle grating.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
An echelle grating spectrometer based on the cross dispersion principle and a method for manufacturing the same according to an embodiment of the present invention are described below with reference to the accompanying drawings.
As shown in fig. 1-11, the echelle grating spectrometer based on the principle of cross dispersion of the present invention comprises a main dispersive element, a transverse dispersive element, an area array detector, an optical fiber and a slit.
The main dispersion element is an echelle bending grating, the transverse dispersion element is a small echelle bending grating, the echelle bending grating and the small echelle bending grating are both plane gratings, and the combination of the echelle bending grating and the small echelle bending grating realizes light splitting and point-to-point aberration elimination imaging. In addition, the main dispersion element is the main dispersion grating, and the transverse dispersion element is the transverse dispersion grating. The curved grating in the present invention refers to a grating in which the shape of the grating lines is curved and is itself planar.
FIG. 5 shows a schematic diagram of an echelle curved reticle grating in which θ is measured from the normal N of the echelle grating in the Y-Z plane B The included angle between the grating normal N and the normal Z of the scribing surface is called the blaze angle of the echelle grating, alpha is the incident angle, beta is the diffraction angle, and d is the grating period.
The main dispersive element and the transverse dispersive element of the invention are both curved reticle gratings. "curved" as used herein refers to the curvature of the grating lines, i.e., curved gratings refer to the fact that the fringes are arcuate and can be considered to be part of a binary higher order curve, the coefficients of which are determined by calculation and simulation. Compared with a curved grating, the common grating has no collimation and focusing capabilities, and when divergent light is incident, the diffracted light is still divergent. The echelle bending grating and the small echelle bending grating have the capabilities of collimation and focusing, and when divergent light is incident, the diffracted light can be directly focused. Therefore, a normal grating requires a collimator lens and a focusing lens to achieve imaging and focusing to spot, whereas a curved grating is not. A schematic diagram of a comparison of a conventional straight reticle grating and a curved reticle grating is shown in fig. 11.
In principle, lens collimation and focusing are specifically to change the optical path of incident light by refraction of the light, so that the wavefront phase of the incident surface meets the distribution requirement of focusing or collimation. The common equidistant straight grating can not change the phase distribution of the incident light at will, but can achieve specific phase distribution by changing the grating pitch and curvature of each part of the grating, thereby collimating or focusing the light. Therefore, by calculating the grating line distribution of different positions of the grating, the modulation of the wavefront of the light can be realized, so that the phase distribution of the light is changed.
In addition, in the same optical path, the bending degree of the echelle grating and the small echelle grating is different, and it is considered that the more the grating is bent, the stronger the converging effect on the light is, and therefore, the bending degree of the two gratings is determined by focusing in the meridian and sagittal directions.
The invention uses the echelle bending grating, the working order of the echelle bending grating is high, so the dispersion rate is high, and the light splitting effect is good.
The term "imaging" in "point-to-point aberration-eliminating imaging" refers to a "focusing" function, i.e., focusing an incident point light source into an outgoing spot.
Explanation and principle analysis of "aberrations" in "point-to-point aberration imaging":
the aberrations of a spectrometer are typically defocus, astigmatism, spherical aberration, coma and other higher order aberrations. The so-called aberrations are eliminated as much as possible, so that the light spot on the image plane reaches the diffraction limit. The principle of aberration elimination is to manipulate the wavefront by changing the pitch and curvature of the grating around to achieve a specific phase distribution.
The aberration elimination method is to use an optical path function method, and comprises the following steps: selecting positions of an object point, an image point and a curved reticle grating, and writing a grating reticle equation as a function of two direction variables of horizontal x and meridian y; the optical path length from the object point to the grating surface and from the grating surface to the image point is represented by variables x and y. Carrying out Taylor expansion on the lens to obtain expressions of various aberration coefficients such as meridian focusing, sagittal focusing, coma, spherical aberration, astigmatism and the like; selecting an optimization function in which a plurality of aberrations are given different weights to be combined; obtaining a result of minimizing an optimization function value by using an optimization algorithm such as a genetic algorithm; finally, the optimized bending grating structure parameters are obtained.
The reticle distribution of the echelle curved grating and the echelle curved grating is obtained through numerical simulation, and the reticle distribution comprises the spacing and the curved shape of the reticles.
The curved reticle grating is specially designed to split and eliminate aberrations, and its grating lines are curved and arc-shaped, unlike conventional gratings which are straight and parallel. The reticle distribution of the curved grating can be calculated through numerical simulation, the reticle distribution comprises the reticle spacing and the curved shape, the reticle spacing and the curved shape are calculated, the reticle spacing and the curved shape change along with the change of the position, and the reticle spacing is changed slowly.
The spectrometer of the invention uses two gratings, and the main dispersion direction grating works in higher order, so that the common rectangular grating or sinusoidal grating can not obtain enough light intensity signals, and therefore, the main dispersion curved reticle grating used needs to be made into an echelle grating with a large blaze angle to achieve higher diffraction efficiency.
The reticle density of the echelle curved grating is lower than that of the echelle curved grating, and the diffraction order of the echelle curved grating is higher than that of the echelle curved grating.
The echelle curved grating has the characteristics of low line density (tens of line pairs), large blaze angle (tens of degrees), high diffraction order (tens to hundreds of orders), and narrow Free Spectral Range (FSR). Echelle curved gratings, also known as "blazed gratings", are characterized by a relatively high reticle density (typically greater than 400 line pairs), a relatively low diffraction order, and a large Free Spectral Range (FSR). The difference between the two is mainly the difference between the reticle density and the blaze angle.
Compared with the common echelle grating, the echelle curved grating has the same characteristics of low line density, generally less than 100gr/mm, large blaze angle, high working order, generally tens to hundreds of orders, high dispersion, high resolution and full wave blaze. The difference is that the common echelle grating lines are straight lines and are parallel to each other, and the echelle curved grating lines are arc lines and curved.
The area array detector is placed in the emergent light direction, the optical fiber is used for emitting light to be detected, the slit is positioned behind the optical fiber, and the slit plays a role of an aperture diaphragm.
The cross dispersion element is placed in a pre-dispersion manner and a post-dispersion manner, wherein the pre-dispersion manner is that the transverse dispersion element is placed before the main dispersion element, and the post-dispersion manner is that the transverse dispersion element is placed after the main dispersion element.
When the transverse dispersion element is arranged in front of the main dispersion element, the transverse dispersion is carried out before the main direction dispersion. At this time, the transverse dispersion element is placed in the direction of the incident light after passing through the slit, and the center of the transverse dispersion element is aligned with the center of the optical fiber and the slit, and the main dispersion element is placed in the direction of the diffracted light, and the center of the main dispersion element is aligned with the optical axis of the diffracted light. After passing through the slit, the light to be measured emitted by the optical fiber irradiates the transverse dispersion element, disperses in the transverse direction to separate different diffraction orders, diffracts through the main dispersion element to form a two-dimensional cross dispersion light beam, and the main dispersion element cooperates with the transverse dispersion element to focus the light in meridian and sagittal directions onto the area array detector together to obtain a two-dimensional dispersion spectrogram of the light source to be measured.
Specifically, the spectrometer only comprises a slit, a main dispersive element, a transverse dispersive element and an area array detector. The slit is positioned behind the optical fiber and acts as an aperture stop, and the transverse dispersion element is arranged in the direction of the incident light after passing through the slit, and the center of the transverse dispersion element is in height with the center of the optical fiber and the slit; placing a main dispersion element in the direction of the diffracted light, and having a center height of the optical axis height of the diffracted light; and finally, placing an area array detector in the emergent light direction. Wherein the optical axis height of the diffracted light is the optical axis height of the principal ray. The principal ray refers to the central ray emitted by the light source, for example, for the incidence of the optical fiber, the principal ray is the ray exiting from the center of the optical fiber and parallel to the optical fiber.
After passing through the shading slit, the light to be measured emitted by the optical fiber irradiates the transverse dispersion element to disperse in the transverse direction, so that different diffraction orders are separated. And then diffracts through the main dispersive curved reticle grating. Because the diffraction angles of different wavelengths are different, the two-dimensional cross dispersion light beams are emitted towards different directions, the main dispersion element is matched with the transverse dispersion element to focus the light in the meridian and sagittal directions onto the area array detector together, and the two-dimensional dispersion spectrogram of the light source to be measured is obtained. The main dispersion direction in the spectrogram is the dispersion direction of the echelle curved grating, the diffraction order separation direction of the transverse dispersion direction is perpendicular to the main dispersion direction, a single-wavelength light spot can be focused on one point on the array detector, and the spectrum information of the light to be detected can be obtained through the two-dimensional spectrum image received by the area array detector.
The transverse dispersion element is arranged after the main dispersion element, and the main direction dispersion is carried out before the transverse dispersion. At this time, the main dispersion element is placed in the direction of the incident light after passing through the slit, and the center of the main dispersion element is aligned with the center of the optical fiber and the slit, and the lateral dispersion element is placed in the direction of the diffracted light, and the center of the lateral dispersion element is aligned with the optical axis of the diffracted light. After passing through the slit, the light to be measured emitted by the optical fiber irradiates the main dispersion element, different wavelengths are separated by dispersion in the main direction, different diffraction orders are separated by dispersion in the transverse direction by the transverse dispersion element, and the transverse dispersion element is matched with the main dispersion element to focus the light in the meridian and sagittal directions onto the area array detector together so as to obtain a two-dimensional dispersion spectrogram of the light source to be measured.
Specifically, the spectrometer only comprises a slit, a main dispersive element, a transverse dispersive element and an area array detector. The slit is positioned behind the light and acts as an aperture stop, the main dispersion element is arranged in the direction of the incident light passing through the slit, and the center of the main dispersion element is in height with the center of the optical fiber and the slit; placing a lateral dispersion element in the direction of the diffracted light, and having a center height that is the height of the optical axis of the diffracted light; and finally, placing an area array detector in the emergent light direction. Wherein the optical axis height of the diffracted light is the optical axis height of the principal ray. The principal ray refers to the central ray emitted by the light source, for example, for the incidence of the optical fiber, the principal ray is the ray exiting from the center of the optical fiber and parallel to the optical fiber.
After passing through the slit, the light to be measured emitted by the optical fiber irradiates onto the main dispersion element, the light is dispersed in the main direction to separate different wavelengths, and then the light is diffracted by the transverse dispersion element, so that the different wavelengths are emitted towards different directions due to different diffraction angles of the different wavelengths, a two-dimensional cross dispersion light beam is formed, and the transverse dispersion element is matched with the main dispersion element to focus the light in the meridian and sagittal directions onto the area array detector together to obtain a two-dimensional dispersion spectrogram of the light source to be measured. The main dispersion direction in the spectrogram is the dispersion direction of the echelle curved grating, the diffraction order separation direction of the transverse dispersion direction is perpendicular to the main dispersion direction, a single-wavelength light spot can be focused on one point on the array detector, and the spectrum information of the light to be detected can be obtained through the two-dimensional spectrum image received by the area array detector.
The preparation method of the echelle grating spectrometer based on the cross dispersion principle comprises the steps of spin coating, exposure and development on a substrate to obtain a curved reticle grating mask pattern; and transferring the mask pattern of the curved reticle grating to a substrate through etching, sputtering metal to form a metal reflecting film, and respectively preparing the echelle curved grating and the echelle curved grating.
The exposure mode is one of electron beam lithography, ultraviolet exposure, laser direct writing or nanometer embossing, the etching mode is dry etching or wet etching, and the metal sputtering mode is magnetron sputtering or electron beam evaporation.
The medium of the spectrometer is air or glass material. When the medium of the spectrometer is air, the elements are only required to be fixed at the designed positions, namely, the echelle bending grating, the small echelle bending grating and the area array detector are fixed and finely adjusted by using corresponding clamps. Specifically, the spectrometer shell is designed, an interface convenient to connect with an optical fiber is arranged on the shell, a corresponding clamp is used for fixing and fine-adjusting two curved reticle gratings and an area array detector, and after the fixed debugging is finished, each element is firmly fixed in a dispensing mode and cannot be displaced.
When the medium of the spectrometer is glass, a polygonal glass block can be processed first, each surface of the side edge of the glass block is smooth, and the processed elements such as gratings and the like are fixed on the side surface of the glass block in an ultraviolet adhesive mode. The middle step bending grating and the small step bending grating are respectively consistent with the corresponding surfaces of the corresponding glass blocks in size, the middle step bending grating is fixedly connected with the glass blocks through ultraviolet glue, and the small step bending grating is fixedly connected with the glass blocks through ultraviolet glue.
Specifically, as shown in fig. 3, the main dispersive curved reticle grating and the transverse dispersive curved reticle grating are respectively consistent with the corresponding surfaces of the corresponding glass blocks, and the patterns are formed in the center of the substrate. The substrate and the corresponding surface of the glass block are completely aligned, so that assembly can be easily carried out, assembly errors are reduced, connection between the substrate and the glass block is realized through ultraviolet glue curing, curing can be completed through ultraviolet lamp irradiation, and optical performance can be stable. It can be understood that when the first dispersive grating in fig. 3 is the main dispersive curved reticle grating, the second dispersive grating is the transverse dispersive curved reticle grating; when the first dispersive grating is a transverse dispersive curved reticle grating, the second dispersive grating is a main dispersive curved reticle grating.
When the spectrometer with the glass medium is processed into a chip, firstly, the thickness and the area of the glass chip are determined, then, the echelle bending grating and the echelle bending grating are designed on the same surface, and two grating patterns are formed simultaneously through one-time photoetching. Specifically, as shown in fig. 4, two curved reticle gratings are fabricated on the lower surface of the glass chip by photolithography, and light is reflected multiple times on the upper and lower surfaces of the chip, so as to achieve the effects of increasing the optical path, improving the resolution and reducing the volume. The two curved reticle gratings in the structure can be designed on the same surface, and two grating patterns can be formed simultaneously by one-time photoetching, so that the alignment difficulty in the processing steps and the processing is greatly reduced. The chip spectrometer has the potential of being applied to portable equipment to realize high spectrum resolution. It can be understood that when the first dispersive grating in fig. 4 is the main dispersive curved reticle grating, the second dispersive grating is the transverse dispersive curved reticle grating; when the first dispersive grating is a transverse dispersive curved reticle grating, the second dispersive grating is a main dispersive curved reticle grating.
Taking the micro spectrometer shown in fig. 2 as an example, a Zemax simulation example was performed. The spectrometer comprises a slit, a main dispersion element, a transverse dispersion element and an area array detector. The slit is positioned behind the optical fiber and acts as an aperture stop; the main dispersion element is arranged in the direction of the incident light after passing through the slit, and the center of the main dispersion element is in high consistency with the center of the optical fiber and the slit; placing a transverse dispersion element in the direction of the diffracted light, wherein the central height of the transverse dispersion element is the height of an optical axis of the diffracted light; and finally, placing an area array detector in the emergent light direction.
Fig. 6 is a simulated overall optical path diagram for a structure with a spectral range of 0.3014-0.3925 microns and corresponding order of 70-90. The input light aperture na=0.11, the apodization type was gaussian, and the apodization factor was set to 1 to simulate a fiber light source. The slit width was 25 microns and the length was 2 millimeters, simulated with a rectangular aperture in software. The center line density of the echelle grating in the main dispersion direction bending line is 54.49gv/mm, and the blaze angle is 48.0085 degrees. The transverse dispersive element is a low-density curved grating with a central pitch of 1.8 microns and an angle of incidence of 46.87 degrees. Both are modeled with binary facets in Zemax.
After passing through the slit, the light emitted by the optical fiber is firstly incident on the transverse dispersion curved grating at 46.87 degrees, then the-1-order diffraction light is incident on the main dispersion direction curved reticle echelle grating at 48.3565 degrees, and finally the diffraction light is focused on the area array detector.
From the grating equation: mλ=d (sinα+sinβ),so that the center wavelength corresponding to each level
Maximum wavelength in this order +.>
Is->
The minimum wavelength is +.>
The wavelength ranges corresponding to different orders can be calculated through the formula:
| grade number | 70 | …… | 79 | 80 | 81 | …… | 90 |
| Center wavelength of | 0.3897 | …… | 0.3453 | 0.3410 | 0.3368 | …… | 0.3031 |
| Maximum wavelength | 0.3925 | …… | 0.3475 | 0.3431 | 0.3389 | …… | 0.3048 |
| Minimum wavelength | 0.3869 | …… | 0.3431 | 0.3389 | 0.3347 | …… | 0.3014 |
The result can be obtained from Zemax's trace map, with the light density set at 45, all structures selected, and the color display set as waves, to obtain a two-dimensional spot on the image plane, as shown in fig. 7. The two-dimensional spectrum image is clearly visible, light spots with different wavelengths can be separated from each other at different levels, and fig. 8 shows that the two wavelengths separated by 80pm are basically distinguishable. Diffraction efficiencies corresponding to each band of wavelengths were simulated using the Rsoft software, as can be seen from fig. 9 to between 40% -80%.
Finally, the signals received by the actual area array CCD are simulated by using a non-sequence mode in Zemax. Fig. 10 shows a simulation image in the range of 26-30 steps, 0.2906-0.3476 microns, with columns of points seen in the figure arranged in steps, with adjacent steps staggered in sequence in a stepwise fashion, and with two wavelengths substantially distinguishable at 80pm intervals.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms may be directed to different embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
Claims (10)
1. An echelle grating spectrometer based on the principle of cross dispersion, comprising:
the main dispersion element is an echelle bending grating;
the transverse dispersion element is a echelle bending grating, and the optical splitting and point-to-point aberration elimination imaging are realized through the combination of the echelle bending grating and the echelle bending grating;
the area array detector is arranged in the emergent light direction;
the optical fiber is used for emitting light to be measured;
and a slit positioned behind the optical fiber, the slit functioning as an aperture stop.
2. The spectrometer of claim 1, wherein the echelle curved grating and the echelle curved grating are both planar gratings, the echelle curved grating having a lower ruling density than the echelle curved grating, the echelle curved grating operating with a higher diffraction order than the echelle curved grating.
3. The spectrometer of claim 1, wherein the reticle distributions of the echelle curved grating and the echelle curved grating are obtained by numerical simulation, the reticle distributions including pitch and curved shape of the reticle.
4. The spectrometer of claim 1, wherein the primary dispersive element is positioned in the direction of the incident light after passing through the slit, and wherein the primary dispersive element center is aligned with the optical fiber and the slit center height, and wherein the lateral dispersive element is positioned in the direction of the diffracted light, and wherein the lateral dispersive element center height is aligned with the optical axis height of the diffracted light.
5. The spectrometer of claim 4, wherein the light to be measured emitted from the optical fiber passes through the slit and irradiates onto the main dispersive element, the light is dispersed in the main direction to separate different wavelengths, and then the light is dispersed in the transverse direction to separate different diffraction orders by the transverse dispersive element, and the transverse dispersive element cooperates with the main dispersive element to focus the light in meridian and sagittal directions onto the area array detector to obtain the two-dimensional dispersion spectrogram of the light source to be measured.
6. The spectrometer of claim 1, wherein the transverse dispersive element is positioned in the direction of the incident light after passing through the slit, and wherein the transverse dispersive element center is aligned with the optical fiber and the slit center height, and wherein the primary dispersive element is positioned in the direction of the diffracted light, and wherein the primary dispersive element center height is aligned with the optical axis height of the diffracted light.
7. The spectrometer of claim 6, wherein the light to be measured emitted from the optical fiber passes through the slit and irradiates onto the transverse dispersion element, the light is dispersed in the transverse direction to separate different diffraction orders, and then the light is diffracted by the main dispersion element to form a two-dimensional cross dispersion light beam, and the main dispersion element cooperates with the transverse dispersion element to focus the light in meridian and sagittal directions onto the area array detector to obtain a two-dimensional dispersion spectrogram of the light source to be measured.
8. The spectrometer of claim 1, wherein the medium of the spectrometer is air or a glass material.
9. A method for preparing an echelle grating spectrometer based on the principle of cross dispersion, which is used for preparing the spectrometer as claimed in any one of claims 1 to 8, comprising the steps of:
uniformly coating, exposing and developing on a substrate to obtain a curved reticle grating mask pattern;
transferring the mask pattern of the curved reticle grating to a substrate through etching, sputtering metal to form a metal reflecting film, and respectively preparing an echelle curved grating and a small echelle curved grating;
when the medium of the spectrometer is air, fixing and fine-adjusting the echelle bending grating, the small echelle bending grating and the area array detector by using corresponding fixtures;
when the medium of the spectrometer is glass, the echelle bending grating and the small echelle bending grating are respectively consistent with the corresponding surfaces of the corresponding glass blocks in size, the echelle bending grating and the glass blocks are fixedly connected through ultraviolet glue, and the small echelle bending grating and the glass blocks are fixedly connected through ultraviolet glue;
when the spectrometer with the glass medium is processed into a chip, firstly, the thickness and the area of the glass chip are determined, then, the echelle bending grating and the echelle bending grating are designed on the same surface, and two grating patterns are formed simultaneously through one-time photoetching.
10. The method of claim 9, wherein the exposure is one of electron beam lithography, ultraviolet exposure, laser direct writing or nanoimprint, the etching is dry etching or wet etching, and the sputtering of metal is magnetron sputtering or electron beam evaporation.
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