Noise optical isolator based on Herriott multi-pass pool

Abstract

The invention relates to the technical field of noise light processing, in particular to a Herriott multi-pass cell-based noise optical isolator, which is used for filtering noise light contained in light rays of a light source and comprises a Herriott multi-pass cell, an absorption cell and a filtering medium, the Herriott multi-pass cell comprises a first concave mirror and a second concave mirror, a light inlet hole and a light outlet hole are formed in the edge positions of the first concave mirror and the second concave mirror respectively, the absorption cell is located between the first concave mirror and the second concave mirror, a filtering medium is contained in the absorption cell, and light of a light source enters the Herriott multi-pass cell through the light inlet hole; the light source light is repeatedly reflected between the first concave mirror and the second concave mirror and then leaves the Herriott multi-pass cell through the light outlet hole, and the light source light passes through the filter medium in the absorption cell during each reflection so as to filter noise light in the light source light. According to the invention, the optical path length of the light of the light source in the absorption cell is multiplied, the saturable absorption of small-signal noise light is realized, and the noise light isolation degree is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of noise light processing, and specifically provides a noise light isolator based on a Heriot multi-pass cell. BACKGROUND

[0002] Extreme ultraviolet (EUV) lithography technology is the core process for realizing mass production of 5 nm and below semiconductor chips, and its light source relies on plasma radiation generated by the interaction of a high-power, high-repetition-rate (>50 kHz) pulsed carbon dioxide laser (wavelength 10.6 μm) and a tin droplet target. To realize stable output of 13.5 nm extreme ultraviolet light, the carbon dioxide laser system needs to adopt a master oscillator power amplifier (MOPA) architecture, that is, a master oscillator generates low-power seed light, which is gradually boosted to megawatt-level peak power through multiple power amplifiers. However, the stray light signals such as amplified spontaneous emission (ASE) noise light and residual light reflected by optical elements generated in the multi-stage amplification process will form a positive feedback loop in the high-gain amplifier, causing power fluctuations, mode competition and even self-oscillation of the system, threatening the stability of the MOPA link. Therefore, a high-isolation optical isolator must be set between adjacent amplification stages to block the noise light transmitted in the reverse direction.

[0003] Traditional laser isolators are mostly based on the Faraday magneto-optical effect principle, but there is no mature magneto-optic crystal material for long-wave carbon dioxide lasers (10.6 μm). The current mainstream solution is to use an optical isolator based on the saturable absorption effect of sulfur hexafluoride gas. Its working principle is as follows: when a high-power laser pulse passes through sulfur hexafluoride gas, the gas molecules are excited to a high-energy state (vibration-rotation energy level) due to stimulated radiation, the absorption coefficient drops sharply (bleaching effect), and the main pulse passes through with low loss; within the pulse interval, sulfur hexafluoride quickly relaxes to the ground state through the vibration-translation (V-T) energy transfer process, and restores the high absorption characteristics (absorption coefficient ) to small signal noise light, thereby realizing the power-selective isolation function of "high-power pulse passing through with low loss, and low-power noise being blocked with high loss".

[0004] However, the sulfur hexafluoride saturable absorption isolator has the following disadvantages: the inherent contradiction between the small signal absorption coefficient and the insertion loss; the noise light absorption depends on the stimulated radiation process, and the recovery depends on the vibration energy transfer and V-T energy transfer process. Increasing the gas pressure and adding buffer gas can improve the small signal noise light absorption rate, but will reduce the pass rate. The problem caused by increasing the length of the absorption cell: increasing the length of the absorption cell can improve the small signal noise laser isolation and the small signal noise light and pulse laser absorption coefficient contrast, but the long multi-pass cell occupies a large space, and the adjustment is difficult, and the longer the straight light path, the higher the probability of beam distortion (especially the circulating flow constant temperature saturable absorption light isolator). The difficulty of focusing to increase the energy density: focusing to increase the energy density in the absorption area of the sulfur hexafluoride absorption cell can increase the isolation without increasing the insertion loss, but due to the diffraction characteristics of long-wave laser, it is difficult to maintain a small beam size for a long distance (the divergence angle of 10.6 μm carbon dioxide laser is ten times that of 1 μm laser).

[0005] The existing sulfur hexafluoride saturable absorption isolator also has the following core contradictions: the isolation (ISO) and the insertion loss (IL) have a negative correlation. Specifically, increasing the optical path length can improve the isolation, but will cause the insertion loss to rise and the volume of the absorption cell to expand; increasing the gas pressure or adding buffer gas (such as He, ) can shorten the relaxation time, but will reduce the main pulse transmittance; focusing the light path can locally enhance the absorption nonlinearity, but due to the diffraction characteristics of long-wave laser, it is difficult to realize the synergistic optimization of long optical path and high energy density, which seriously restricts the application of sulfur hexafluoride saturable absorption isolator in the next generation of EUV laser system.

[0006] In summary, a new type of saturable absorption isolator design scheme is needed, which can realize the synergistic performance breakthrough of high isolation (ISO>30dB), low insertion loss (IL<5%) and high damage threshold ( ) in a compact space. SUMMARY

[0007] The present application is to solve the above problems, and provides a noise light isolator based on a Herriott multi-pass cell, which combines a Herriott multi-pass cell with an absorption cell to filter noise light in the light source light during repeated refraction, realizes saturable absorption of small signal noise light, and effectively improves the noise light isolation.

[0008] The noise light isolator based on the Herriott multi-pass cell provided by the present application is used to filter noise light contained in light source light, and comprises: a Herriott multi-pass cell, an absorption cell and a filtering medium; The light source light can be repeatedly reflected inside the Herriott multi-pass cell; The absorption cell is located inside the Heriot multi-pass cell, and a filter medium is arranged in the absorption cell; The light source light passes through the filter medium in the absorption cell each time the light source light is reflected, and the filter medium is used to filter noise light in the light source light.

[0009] Preferably, the Heriot multi-pass cell comprises a first concave mirror and a second concave mirror, and the first concave mirror and the second concave mirror are coaxial, and the light source light is repeatedly reflected between the first concave mirror and the second concave mirror.

[0010] Preferably, an entrance hole is arranged at an edge position of the first concave mirror, and an exit hole is arranged at an edge position of the second concave mirror, and the light source light enters the Heriot multi-pass cell through the entrance hole and exits the Heriot multi-pass cell through the exit hole after repeated reflection.

[0011] Preferably, the light source light repeatedly reflects to form a plurality of reflection points, and the diameters of the entrance hole and the exit hole are both smaller than the distance between any two adjacent reflection points.

[0012] Preferably, the surfaces of the first concave mirror and the second concave mirror are coated with high-reflection film for enhancing reflection of the light source light.

[0013] Preferably, the absorption cell is located at the geometric center between the first concave mirror and the second concave mirror.

[0014] Preferably, the focal points of the light source light after each reflection are located at the middle position of the absorption cell and form a focal plane.

[0015] Preferably, along the horizontal axis direction of the absorption cell, a first window mirror and a second window mirror are arranged at the two sides of the absorption cell respectively, and the light source light passes through the filter medium in the absorption cell through the first window mirror and the second window mirror.

[0016] Preferably, along the direction perpendicular to the axis of the absorption cell, an air inlet and an air outlet are arranged at the two sides of the absorption cell respectively, the filter medium is injected into the absorption cell through the air inlet, and the filter medium in the absorption cell is discharged through the air outlet.

[0017] Preferably, the air inlet and the air outlet are connected to a gas circulation device through gas pipelines respectively, and the gas circulation device drives the filter medium to circulate through the absorption cell.

[0018] Compared with the prior art, the present application can achieve the following beneficial effects: The application innovatively embeds an absorption cell in the Herriott multi-pass cell, and by the synergistic effect of the first concave mirror and the second concave mirror in the multi-pass cell, the light rays of the light source are repeatedly reflected in the Herriott multi-pass cell, and the optical path is significantly prolonged. In the whole process of light reflection, the light rays of the light source pass through the absorption cell, which is equivalent to doubling the optical path length of the light rays of the light source in the saturable absorption medium. Based on this, the saturable absorption function of the small signal noise light is realized, the isolation is effectively improved, and the absorption rate of the small signal noise light is greatly improved. Moreover, the power loss of the main pulse is small when the light rays of the light source pass through the absorption cell each time, and by accurately and reasonably regulating the light path and the pressure of the filtering medium, the transmittance of the main pulse can be ensured to be not less than 95%.

[0019] According to the light beam reproduction law of the Herriott multi-pass cell, the focal point of the light beam formed by the reflection of the light rays of the light source is stably maintained at the midpoint position of the Z axis (i.e. the normal direction of the concave mirror) of the Herriott cell, so the light beam is highly focused in the central region. The application sets the absorption cell in this central region, so that the light beam always maintains a focused state when passing through the filtering medium. This focused state greatly increases the peak power density, not only effectively reduces the insertion loss of the main pulse laser, but also further enhances the noise light isolation.

[0020] Due to the reflection effect of the Herriott multi-pass cell, the originally linear long-distance single optical path is ingeniously converted into a short-distance multi-optical path structure, which greatly increases the optical path in a limited space, making the noise light isolator structure of the application more compact, greatly reducing the volume and significantly reducing the cost. At the same time, it has stronger applicability and can meet the application requirements in many different scenes.

[0021] The application also provides a gas circulation device to circulate the filtering medium in the absorption cell. The circulation of the filtering medium can further increase the isolation, speed up the upper energy level relaxation, and stabilize the temperature of the filtering medium. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a structure diagram of a noise light isolator based on a Herriott multi-pass cell according to an embodiment of the application; Figure 2 is a schematic diagram of the reflection of the light rays of the light source in the Herriott multi-pass cell according to an embodiment of the application; Figure 3 is a distribution diagram of the reflection points on the first concave mirror (or the second concave mirror) in a simulation experiment according to an embodiment of the application; Figure 4 is a comparison diagram of the incident main pulse and the incident small signal noise light intensity according to an embodiment of the application; Figure 5The outcoming main pulse and outcoming small signal noise light intensity contrast diagram is provided according to the embodiment of the present application.

[0023] The reference signs in the drawings include: Light source 1, light source light 11, incident main pulse 12, incident small signal noise light 13, outcoming main pulse 14, outcoming small signal noise light 15, Herriott multi-pass cell 2, first concave mirror 21, second concave mirror 22, light inlet hole 23, light outlet hole 24, reflection point 25, absorption cell 3, first window mirror 31, second window mirror 32, air inlet 33, air outlet 34, gas pipeline 35, filter medium 4. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and do not constitute a limitation on the present application. Similar elements in different embodiments use associated similar element numbers. In the following embodiments, many details are described in order to make the present application better understood. However, those skilled in the art can easily recognize that some features can be omitted in different cases, or can be replaced by other elements, materials or methods. In some cases, some operations related to the present application are not shown or described in the specification in order to avoid the core part of the present application being overwhelmed by too much description, and it is not necessary to describe these related operations in detail for those skilled in the art according to the description in the specification and general technical knowledge in the art.

[0025] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other to form various embodiments without conflict. Meanwhile, each step or action in the method description can also be sequentially adjusted or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment, and do not mean a necessary sequence, unless otherwise stated that a certain sequence must be followed.

[0026] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0027] In the description of the present application, it should be noted that unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0028] The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0029] As shown in Figure 1 and Figure 2 The present application provides a noise light isolator based on a Heriot multi-pass cell, which is used to filter noise light contained in light source light 11. The noise light isolator comprises a light source 1, a Heriot multi-pass cell 2, an absorption cell 3 and a filter medium 4.

[0030] The light source 1 of the present application is a high-repetition-rate short-pulse carbon dioxide laser light source (for example Laser, which can also be other waveband lasers such as mid-wave lasers, 1um or 2um lasers), which is composed of core modules such as seed laser and main amplifier, wherein the seed laser can adopt types such as acousto-optic modulated carbon dioxide pulse clipping laser, electro-optic cavity emptying carbon dioxide laser or quantum cascade laser, and the main amplifier selects structures such as fast transverse flow carbon dioxide laser, fast axial flow carbon dioxide laser or slab carbon dioxide laser.

[0031] In the embodiment of the present application, the light source 1 is cooperated with a seed laser and a first fast-axis flow carbon dioxide amplifier, and the carbon dioxide laser pulses provided by the light source 1 meet the requirements of the main pump carbon dioxide laser of the LPP-EUV light source except for the power, that is, the high-repetition-rate short-pulse carbon dioxide laser provided by the embodiment of the present application has a repetition frequency of 50 kHz to 100 kHz, a linearly or circularly polarized light, a beam quality M2 factor less than 3, a pulse width of 10 ns to 50 ns, and an average power of hundreds of watts to thousands of watts, and the final output power reaches 1000 W. It is worth noting that the amplified carbon dioxide laser may contain a small-signal noise light component with a power of 10 W or even higher, and the remaining part is the required short-pulse carbon dioxide laser. The small-signal noise light can be generated by a MOPA laser containing all the amplifier stages, or can be generated by a MOPA partial amplifier stage, and the small-signal noise light in the high-repetition-rate short-pulse carbon dioxide laser can be isolated by a noise light isolator.

[0032] The Heriot multi-pass cell 2 includes two focusing mirrors, i.e., a first concave mirror 21 and a second concave mirror 22. The concave surfaces of the first concave mirror 21 and the second concave mirror 22 are oppositely arranged, the optical axis of the first concave mirror 21 is coaxial with the optical axis of the second concave mirror 22, the focal point of the first concave mirror 21 is collinear with the focal point of the second concave mirror 22, and the base of the first concave mirror 21 and the base of the second concave mirror 22 can be silicon, copper, gallium arsenide or the like. The edge position of the first concave mirror 21 is provided with an entrance hole 23, and the edge position of the second concave mirror 22 is provided with an exit hole 24. The light source light 11 (i.e., the carbon dioxide laser in the embodiment of the present application) emitted by the light source 1 enters the Heriot multi-pass cell 2 from the entrance hole 23 on the first concave mirror 21 and repeatedly reflects between the first concave mirror 21 and the second concave mirror 22, and finally exits the Heriot multi-pass cell 2 from the exit hole 24 on the second concave mirror 22. The light source light 11 is greatly increased in optical path by a limited number of reflections, which is equivalent to shortening the long single optical path, thereby reducing the volume of the noise light isolator and making the structure more compact. The long single optical path is greatly reduced to: wherein, represents the light transmission thickness, which is the effective light transmission optical path of the linear noise light isolator, i.e., the length of the single optical path of the linear noise light isolator under the same optical path distance, represents the number of reflections of the light source light 11 in the Heriot multi-pass cell 2, is the single light transmission optical path of the light source light 11 in the Heriot multi-pass cell 2, i.e., the length of the Heriot multi-pass cell 2.

[0033] As Figure 3As shown, the light source light 11 forms multiple reflection points 25 on the first concave mirror 21 and the second concave mirror 22 in the repeated reflection process, and the reflection points 25 are distributed at equal intervals along the circumference. In order to ensure that the light source light 11 stays in the Herriott multi-pass cell 2 for a sufficient amount of time and the optical path is long enough, that is, to ensure that the light source light 11 does not leave the Herriott multi-pass cell 2 too early, the diameters of the light inlet hole 23 and the light outlet hole 24 are both set to be smaller than the distance between any two adjacent reflection points on the first concave mirror 21 or the second concave mirror 22, so as to achieve the purpose that the light source light 11 does not leave the Herriott multi-pass cell 2 too early. Figure 3 Different colors represent different incoherent irradiance.

[0034] In other embodiments of the present application, the Herriott multi-pass cell 2 can also be designed in other structures, for example, a structure containing multiple concave mirrors.

[0035] In order to ensure the reflection effect of the first concave mirror 21 and the second concave mirror 22 on the carbon dioxide laser, the surface of the first concave mirror 21 and the second concave mirror 22 is coated with a carbon dioxide laser high reflection film in the embodiment of the present application, so as to enhance the reflection of the first concave mirror 21 and the second concave mirror 22 on the carbon dioxide laser. If the light source light 11 emitted by the light source 1 is other light, the surface of the first concave mirror 21 and the second concave mirror 22 is correspondingly coated with a high reflection film that enhances the reflection of the light source light 11.

[0036] The absorption cell 3 is a structure similar to a hexahedron, which is made of materials such as stainless steel and aluminum alloy, and the light transmission thickness of the absorption cell 3 is depending on the required isolation of the light source light 11, the light transmission thickness is the effective light transmission path of the linear noise light isolator (the propagation direction of the light source light 11 and the axial angle of the absorption cell 3 are very small). The absorption cell 3 is located between the first concave mirror 21 and the second concave mirror 22, and the optimal position is the geometric center between the first concave mirror 21 and the second concave mirror 22. The absorption cell 3 can be vacuum sealed with a filter medium 4, and the filter medium 4 is used to filter out small signal noise light in the light source light 11.

[0037] Along the horizontal axis direction of the absorption cell 3, the left and right sides of the absorption cell 3 are respectively provided with a first window mirror 31 and a second window mirror 32, the first window mirror 31 and the second window mirror 32 have high transmittance to the light source light 11, and the projections of the first window mirror 31 and the second window mirror 32 along the optical axis direction overlap. Along the direction perpendicular to the axis of the absorption cell 3, the two sides of the absorption cell 3 are respectively provided with an air inlet 33 and an air outlet 34, the filter medium 4 is injected into the absorption cell 3 through the air inlet 33, and the filter medium 4 in the absorption cell 3 is discharged through the air outlet 34.

[0038] As Figure 4As shown, the contrast between the main pulse light intensity and the small signal noise light intensity in the light source light 11 is shown. The time-domain waveform of the main pulse is generally Gaussian, and it can also be triangular or Gaussian waveform containing a pedestal. The small signal noise light is generated by the amplification of spontaneous emission light, or reflected at the uncontrolled reflection point in the MOPA system, and developed from a small signal to form an oscillation after exceeding the threshold. The light source light 11 emitted by the light source 1 enters the Heriot multi-pass cell 2 through the light inlet hole 23, and repeatedly reflects between the first concave mirror 21 and the second concave mirror 22. Since the absorption cell 3 is located between the first concave mirror 21 and the second concave mirror 22, and the first window mirror 31 and the second window mirror 32 are arranged on the left and right sides of the absorption cell 3 respectively, the light source light 11 repeatedly reflects inside the Heriot multi-pass cell 2, and each reflection passes through the absorption cell 3, that is, passes through the filter medium 4 sealed inside the absorption cell 3, through the first window mirror 31 and the second window mirror 32. The focal point of the light source light 11 after each reflection is located at the middle position of the absorption cell 3 and forms a focal plane, and the cross section of the filter medium 4 covers the focal point of each reflection. As shown in Figure 5 As shown, the contrast between the main pulse light intensity and the small signal noise light intensity in the light source light 11 is shown. The time-domain waveform of the main pulse is generally Gaussian, and it can also be triangular or Gaussian waveform containing a pedestal. The small signal noise light is generated by the amplification of spontaneous emission light, or reflected at the uncontrolled reflection point in the MOPA system, and developed from a small signal to form an oscillation after exceeding the threshold. The light source light 11 emitted by the light source 1 enters the Heriot multi-pass cell 2 through the light inlet hole 23, and repeatedly reflects between the first concave mirror 21 and the second concave mirror 22. Since the absorption cell 3 is located between the first concave mirror 21 and the second concave mirror 22, and the first window mirror 31 and the second window mirror 32 are arranged on the left and right sides of the absorption cell 3 respectively, the light source light 11 repeatedly reflects inside the Heriot multi-pass cell 2, and each reflection passes through the absorption cell 3, that is, passes through the filter medium 4 sealed inside the absorption cell 3, through the first window mirror 31 and the second window mirror 32. The focal point of the light source light 11 after each reflection is located at the middle position of the absorption cell 3 and forms a focal plane, and the cross section of the filter medium 4 covers the focal point of each reflection. As shown in

[0039] The focal point of the light source light 11 after each reflection is located at the middle position of the absorption cell 3 and forms a focal plane, and the cross section of the filter medium 4 covers the focal point of each reflection. As shown in The size of the focal point of the light source light 11 after each reflection is about: , wherein, f represents the focal length of the Heriot multi-pass cell 2, and represents the beam divergence angle of the light source light 11 before entering the Heriot multi-pass cell 2.

[0040] The average power density is: .

[0041] After filtering by the absorption cell 3, the main pulse transmittance of the light source light 11 is : , Transmittance of small signal noise light is: , wherein, represents, represents, represents, represents the optical thickness.

[0042] Because the main pulse power in the light source light 11 is obviously higher than the small signal noise light, according to the saturable absorption principle, is obviously smaller than , the main pulse and the small signal noise light have obvious difference in transmittance, and the small signal noise light is obviously suppressed. Specifically, the transmittance of the main pulse of the light source light 11 is 0.9, the transmittance of the small signal noise light is 0.01, the contrast ratio of the two changes from 1000:1 to 900:0.1, and the small signal noise light is obviously suppressed.

[0043] The filtering medium 4 sealed in the absorption cell 3 can be sulfur hexafluoride or a mixed gas of sulfur hexafluoride, such as sulfur hexafluoride mixed with helium or nitrogen. The embodiment of the present application adopts sulfur hexafluoride as the filtering medium 4.

[0044] In order to improve the filtering effect of noise light, the embodiment of the present application also provides a gas circulation device, and the gas inlet 33 and the gas outlet 34 are connected to the gas circulation device through the gas pipeline 35 respectively, and the filtering medium 4 is circulated and flows in the absorption cell 3 by the gas circulation device. In order to promote the circulation effect of the filtering medium 4, the inner wall of the absorption cell 3 at the edge of the first window mirror 31 and the second window mirror 32 is set to be a low-pressure-drop streamline type, and the connection between the gas pipeline 35 and the gas inlet 33 and the gas outlet 34 is set to be a vacuum standard chuck interface of KF, ISO, CF and the like standard, so as to reduce the resistance of the filtering medium 4 during circulation. By setting the gas circulation device, the filtering medium 4 can be circulated in the absorption cell 3, the circulation of the filtering medium 4 can further increase the isolation degree, speed up the upper energy level relaxation, and stabilize the temperature of the filtering medium 4 In order to maintain the temperature of the filtering medium 4, a heat exchanger or a gas flow device can be added to the absorption cell 3, so as to maintain the stability of the isolation degree and the insertion loss of the absorption cell 3.

[0045] The embodiment of the present application carries out simulation experiment on the noise light isolator based on the Herriott multi-pass cell, and obtains the distribution diagram of the reflection points 25 on the first concave mirror (or the second concave mirror) as shown in Figure 3 From Figure 3 It can be seen that the reflection points 25 are distributed on the first concave mirror (or the second concave mirror) according to the circumference and the equal interval.

[0046] ​​The light source light 11 emitted by the light source 1 enters the Herriot multi-pass cell 2, which contains the incident main pulse 12 and the incident small signal noise light 13, as shown in FIG. 1. Figure 4 As shown in FIG. 1, the time-domain waveform of the incident main pulse 12 is generally Gaussian, or possibly triangular or Gaussian waveforms containing pedestals. The intensity of the incident small signal noise light 13 is much lower than that of the incident main pulse 12. After filtering by the noise light isolator, the outgoing light from the Herriot multi-pass cell 2 contains the outgoing main pulse 14 and the outgoing small signal noise light 15, as shown in FIG. 2. Figure 5 As shown in FIG. 2, the intensity of the outgoing main pulse 14 is partially lost, and the intensity of the outgoing small signal noise light 15 is greatly attenuated.

[0047] Although the embodiments of the present application have been shown and described above, it should be understood that the above-described embodiments are exemplary and are not to be construed as limiting the present application. Those ordinarily skilled in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the present application.

[0048] The specific embodiments of the present application described above do not constitute a limitation on the scope of protection of the present application. Any various other corresponding changes and modifications made according to the technical concept of the present application shall be included in the scope of protection of the claims of the present application.

Claims

1. A Heriot multi-pass-cell based noise optical isolator for filtering noise light contained in light from a light source, characterized by, The application relates to a light source and a light source system. The light source comprises: a Heriot multi-pass cell, an absorption cell and a filtering medium; the light rays of the light source repeatedly reflect inside the Heriot multi-pass cell; the absorption cell is located inside the Heriot multi-pass cell, and the filtering medium is arranged in the absorption cell; 2. The Héroniot multi-pass-cell based noise optical isolator of claim 1, A characterized by, the filtering medium is used for filtering noise light in the light rays of the light source during each reflection of the light rays.

3. The Héroniot multi-pass-cell based noise optical isolator of claim 2, wherein, The Heriot multi-pass cell comprises a first concave mirror and a second concave mirror, the first concave mirror and the second concave mirror are coaxial, and the light rays of the light source repeatedly reflect between the first concave mirror and the second concave mirror.

4. The Héroniot multi-pass-cell based noise optical isolator of claim 3, wherein, An entrance hole is arranged at the edge position of the first concave mirror, and an exit hole is arranged at the edge position of the second concave mirror, the light rays of the light source enter the Heriot multi-pass cell through the entrance hole and exit the Heriot multi-pass cell through the exit hole after repeated reflection.

5. The Héroniot multi-pass-cell based noise optical isolator as set forth in claim 2, wherein, The light rays of the light source repeatedly reflect to form a plurality of reflection points, and the diameters of the entrance hole and the exit hole are smaller than the distance between any two adjacent reflection points.

6. The Héroniot multi-pass-cell based noise optical isolator as set forth in claim 1, wherein, The surfaces of the first concave mirror and the second concave mirror are coated with high-reflection film for enhancing the reflection of the light rays of the light source.

7. The Heriot multi-pass-cell based noise optical isolator of claim 1, wherein, The absorption cell is located at the geometric center between the first concave mirror and the second concave mirror.

8. The Heriot multi-pass-cell based noise optical isolator as described in claim 1, wherein, The focal points of the light rays of the light source after each reflection are located at the middle position of the absorption cell and form a focal plane.

9. The Heriot multi-pass-cell based noise optical isolator as described in claim 1, wherein, First window mirrors and second window mirrors are arranged at the two sides of the absorption cell along the horizontal axis direction of the absorption cell, and the light rays of the light source pass through the filtering medium in the absorption cell through the first window mirrors and the second window mirrors.

10. The Heriot multi-pass-cell based noise optical isolator as described in claim 1, wherein, Air inlets and air outlets are arranged at the two sides of the absorption cell along the direction perpendicular to the axis of the absorption cell, the filtering medium is injected into the absorption cell through the air inlets, and the filtering medium in the absorption cell is discharged through the air outlets. The air inlets and the air outlets are connected with a gas circulation device through gas pipelines, and the gas circulation device drives the filtering medium to circulate through the absorption cell.

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