An optical parametric oscillator based on a whispering gallery microcavity and its design method

Abstract

The present application provides a whispering gallery mode optical parametric oscillator and a design method thereof, which can improve the efficiency of converting pump light into idler light by the whispering gallery mode optical parametric oscillator. The whispering gallery mode optical parametric oscillator includes a first optical parametric oscillator and a second optical parametric oscillator; the first optical parametric oscillator and the second optical parametric oscillator share the same whispering gallery mode microcavity, and a first pump light is coupled into the whispering gallery mode microcavity. The first optical parametric oscillator converts the first pump light into a first signal light and a first idler light through a second-order nonlinear process; the first signal light serves as the second pump light of the second optical parametric oscillator, and the second optical parametric oscillator converts the second pump light into a second signal light and a second idler light through a second-order nonlinear process, wherein the wavelength of the first signal light is the same as the wavelength of the second pump light, and the wavelength of the first idler light is the same as the wavelength of the second idler light.

Description

Technical Field

[0001] The present application relates to the technical field of optical parametric oscillators, and particularly to a whispering gallery mode optical parametric oscillator and its design method. Background Art

[0002] An optical parametric oscillator (OPO) is a parametric oscillator that oscillates at optical frequencies. It converts the input pump light into two output lights with lower frequencies, namely signal light and idler light, through second-order nonlinear optical interaction. The whispering gallery optical microcavity (which can be called a whispering gallery microcavity) has a small mode volume and a high quality factor, which can greatly enhance the interaction between light and matter; and the whispering gallery optical microcavity has good integration and is considered to have great application prospects in the field of integrated optical devices.

[0003] The whispering gallery microcavity is generally made of materials with a high refractive index, such as polydimethylsiloxane, glass, etc. It mainly confines light in the cavity by means of total internal reflection that continuously occurs at the inner interface of the microcavity. When the light propagates along the inner surface of the whispering gallery microcavity for one week, if the wavelength satisfies the constructive interference condition, a stable traveling wave transmission mode will be formed in the cavity, and finally a strong confinement of the light field is realized. The whispering gallery microcavity made of nonlinear crystals such as lithium niobate has a second-order nonlinear effect and will generate nonlinear gain under the action of pump light, thereby forming a whispering gallery mode optical parametric oscillator.

[0004] However, the current whispering gallery mode optical parametric oscillator has a low efficiency in converting the input pump light into idler light. Theoretically, the highest conversion efficiency is only 50%. How to improve the efficiency of the whispering gallery mode optical parametric oscillator in converting pump light into idler light has become an urgent problem to be solved. Summary of the Invention

[0005] The present application provides a whispering gallery mode optical parametric oscillator and its design method, which can improve the efficiency of the whispering gallery mode optical parametric oscillator in converting pump light into idler light.

[0006] In a first aspect, a whispering gallery mode optical parametric oscillator is provided, including a first optical parametric oscillator and a second optical parametric oscillator;

[0007] The first optical parametric oscillator and the second optical parametric oscillator share the same whispering gallery microcavity,

[0008] The first pump light is coupled into the whispering gallery microcavity, and the first optical parametric oscillator converts the first pump light into a first signal light and a first idler light through a second-order nonlinear process;

[0009] The first signal light serves as the second pump light of the second optical parametric oscillator. The second optical parametric oscillator converts the second pump light into a second signal light and a second idler light through a second-order nonlinear process.

[0010] Among them, the wavelength of the first signal light is the same as that of the second pump light, and the wavelength of the first idler light is the same as that of the second idler light.

[0011] In one example, the whispering gallery microcavity is of a disk-shaped structure, and both the first optical parametric oscillator and the second optical parametric oscillator are fan-shaped regions; the first optical parametric oscillator and the second optical parametric oscillator do not overlap; the light wave travels along the circular cavity wall of the whispering gallery microcavity.

[0012] In one example, the first optical parametric oscillator includes at least one first fan-shaped sub-region, and the first fan-shaped sub-region is composed of a first fan-shaped domain structure and a second fan-shaped domain structure with opposite polarization directions;

[0013] The structural dimensions of each first fan-shaped sub-region are the same, and the light wave travels along the arc-shaped wall of each first fan-shaped sub-region; the arc length of the arc-shaped wall of each first fan-shaped sub-region is the period length of the first optical parametric oscillator:

[0014] Λ 1 = θ 1 r,

[0015] Among them, θ 1 represents the central angle of each first fan-shaped sub-region, and r is the radius of the whispering gallery microcavity;

[0016] Moreover, the period length of the first optical parametric oscillator satisfies the following formula:

[0017]

[0018] Among them, represents the wavelength of the first pump light, represents the wavelength of the first signal light, represents the wavelength of the first idler light, represents the effective refractive index of the first pump light transmitted in the whispering gallery microcavity, represents the effective refractive index of the first signal light transmitted in the whispering gallery microcavity, represents the effective refractive index of the first idler light transmitted in the whispering gallery microcavity.

[0019] In one example, the perimeter of the whispering gallery microcavity is an integer multiple of Λ 1 of.

[0020] In one example, the second optical parametric oscillator includes at least one second fan-shaped sub-region, and the second fan-shaped sub-region is composed of a third fan-shaped domain structure and a fourth fan-shaped domain structure with opposite polarization directions;

[0021] The structural dimensions of each second sector sub-region are the same, and light waves are transmitted along the arc-shaped walls of each second sector sub-region; the arc length of the arc-shaped wall of each second sector sub-region is the period length of the second optical parametric oscillator:

[0022] Λ 2 = θ 2 r,

[0023] where θ 2 represents the central angle of each first sector sub-region, and r is the radius of the whispering gallery microcavity;

[0024] Moreover, the period length of the second optical parametric oscillator satisfies the following formula:

[0025]

[0026] where represents the wavelength of the second pump light, represents the wavelength of the second signal light, represents the wavelength of the second idler light, represents the effective refractive index of the second pump light transmitted in the whispering gallery microcavity, represents the effective refractive index of the second signal light transmitted in the whispering gallery microcavity, represents the effective refractive index of the second idler light transmitted in the whispering gallery microcavity.

[0027] In one example, the perimeter of the whispering gallery microcavity is an integer multiple of Λ 2 .

[0028] As can be seen from the above embodiments, in the present application, by arranging two optical parametric oscillators in a whispering gallery microcavity, the first pump light coupled into the first optical parametric oscillator is converted into a first signal light and a first idler light. Then, the first signal light is used as the second pump light of the second optical parametric oscillator, so that the second optical parametric oscillator converts the second pump light into a second signal light and a second idler light. Since the wavelength of the second idler light is the same as that of the first idler light and they can be coupled to each other, the second idler light can be coupled with the first idler light into the same idler light, achieving enhancement on the basis of the first idler light. Compared with the current whispering gallery microcavity scheme where the theoretical maximum efficiency of converting pump light into idler light is only 50% (i.e., the efficiency of converting pump light into idler light is 50%, and the efficiency of converting into signal light is 50%), for the whispering gallery microcavity provided in the present application with two optical parametric oscillators, the theoretical efficiency of converting pump light into idler light can reach 75% (i.e., the efficiency of converting the first pump light into the first idler light is 50%, and the efficiency of converting into the first signal light is 50%. Then, the efficiency of converting the first signal light as the pump light into the second idler light is 50% (relative to the efficiency of the first pump light is 50%×50% = 25%). Therefore, the total efficiency of converting the first pump light into idler light is 50% + 25% = 75%). Therefore, the whispering gallery microcavity optical parametric oscillator provided in the present application greatly improves the efficiency of converting pump light into idler light.

[0029] In a second aspect, a design method of a whispering gallery microcavity optical parametric oscillator is provided, including:

[0030] (1) Select the material of the whispering gallery microcavity, the radius r of the whispering gallery microcavity, and the operating temperature T of the whispering gallery microcavity;

[0031] (2) The wavelength of the first idler light is the same as that of the second idler light; determine the wavelength of the first pump light The wavelength of the first signal light The wavelength of the first idler light The wavelength of the second pump light The wavelength of the second signal light And the wavelength of the second idler light Wherein

[0032] (3) According to the wavelength of the first pump light The wavelength of the first signal light And the wavelength of the first idler light Determine the period length Λ of the first optical parametric oscillator 1 , according to the wavelength of the second pump light The wavelength of the second signal light And the wavelength of the second idler light Determine the period length Λ of the second optical parametric oscillator 2,

[0033] (4) Determine the number Q of the first sector regions in the first optical parametric oscillator according to the period length Λ of the first optical parametric oscillator 1 and the period length Λ of the second optical parametric oscillator 2 , and determine the number Q of the second sector regions in the second optical parametric oscillator 1 ; 2 ;

[0034] (5) Prepare the whispering gallery mode optical parametric oscillator by the electric field room temperature polarization process and the mechanical polishing process according to the above parameters.

[0035] In one example, step (2) includes:

[0036] Determine the refractive index n(T,λ) of the light wave with different wavelengths in the material of the whispering gallery mode at the working temperature T according to the material of the whispering gallery mode, the corresponding Sellmeier equation and the mode of the whispering gallery mode;

[0037] Moreover, the optical path for the light wave to transmit one week along the circular cavity wall of the whispering gallery mode is: L c = 2πn(T,λ)·r, and the light wave in the whispering gallery mode satisfies the resonance wavelength formula: Nλ = L c , where N represents a positive integer;

[0038] And the light wave in the second-order nonlinear process in the first optical parametric oscillator satisfies the energy conservation equation: The light wave in the second-order nonlinear process in the second optical parametric oscillator satisfies the energy conservation equation:

[0039] Determine the wavelength of the first pump light The wavelength of the first signal light The wavelength of the first idler light The wavelength of the second pump light The wavelength of the second signal light And the wavelength of the second idler light

[0040] In one example, step (3) includes:

[0041] According to the light wave in the second-order nonlinear process in the first optical parametric oscillator satisfying the momentum conservation equation: Determine the period length Λ of the first optical parametric oscillator 1 ;

[0042] The light wave in the second-order nonlinear process in the second optical parametric oscillator satisfies the momentum conservation equation: Determine the period length Λ of the second optical parametric oscillator 2 .

[0043] In one example, according to the perimeter of the whispering gallery microcavity being an integer multiple of the period length Λ of the first optical parametric oscillator, i.e., M 1 A 1 A 1 = 2πr, where Λ 1 = θ 1 r, M 1 is a positive integer, and θ 1 is the central angle of the first sector sub-region;

[0044] According to the perimeter of the whispering gallery microcavity being an integer multiple of the period length Λ of the second optical parametric oscillator, i.e., M 2 A 2 A 2 = 2πr, where Λ 2 = θ 2 r, M 2 is a positive integer, and θ 2 is the central angle of the second sector sub-region;

[0045] Moreover, since the whispering gallery microcavity includes the first optical parametric oscillator and the second optical parametric oscillator, the number Q of the first sector regions in the first optical parametric oscillator 1 is the integer part of M 1 / 2, and the number Q of the second sector regions in the second optical parametric oscillator 2 is the integer part of M 2 / 2.

[0046] As can be seen from the above embodiments, in the present application, by setting the first signal light output by the first optical parametric oscillator as the second pump light output by the second optical parametric oscillator, and the wavelengths of the first idler light and the second idler light being the same, the efficiency of converting the pump light into the idler light by the optical parametric oscillator is improved. When designing the above whispering gallery optical parametric oscillator, it is necessary to obtain the material of the whispering gallery microcavity, the radius r of the whispering gallery microcavity, the operating temperature T of the whispering gallery microcavity, the number Q of the first sector regions in the first optical parametric oscillator determined according to the period length Λ 1 of the first optical parametric oscillator, 1 and the number Q of the second sector regions in the second optical parametric oscillator determined according to the period length Λ 2 of the second optical parametric oscillator 2 These parameters, and then prepare the whispering gallery microcavity optical parametric oscillator according to these parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] To more clearly illustrate the technical solution of the present application, the accompanying drawings required for use in the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0048] Figure 1 is a schematic diagram of a whispering gallery mode optical parametric oscillator provided by an exemplary embodiment of the present application;

[0049] Figure 2 is another schematic diagram of a whispering gallery mode optical parametric oscillator provided by an exemplary embodiment of the present application;

[0050] Figure 3 is yet another schematic diagram of a whispering gallery mode optical parametric oscillator provided by an exemplary embodiment of the present application. Detailed implementation manners

[0051] The embodiments of the present application will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application. It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0052] Those skilled in the art of the present technology can understand that, unless specifically stated otherwise, the singular forms "a", "an", "the" and "said" used herein may also include the plural forms. It should be further understood that the term "including" used in the specification of the present application means the presence of the described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups. It should be understood that when we say that an element is "connected" or "coupled" to another element, it can be directly connected or coupled to other elements, or there may also be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The phrase "and / or" used herein includes all or any unit and all combinations of one or more related listed items.

[0053] To improve the efficiency of converting pump light into idler light by a whispering gallery mode optical parametric oscillator, as Figure 1As shown, the present application provides a whispering gallery mode optical parametric oscillator, which includes a first optical parametric oscillator and a second optical parametric oscillator. The first optical parametric oscillator and the second optical parametric oscillator share the same whispering gallery mode microcavity. The first pump light is coupled into the whispering gallery mode microcavity. The first optical parametric oscillator converts the first pump light into a first signal light and a first idler light through a second-order nonlinear process. The first signal light serves as the second pump light of the second optical parametric oscillator. The second optical parametric oscillator converts the second pump light into a second signal light and a second idler light through a second-order nonlinear process. Wherein, the wavelength of the first signal light is the same as the wavelength of the second pump light, and the wavelength of the first idler light is the same as the wavelength of the second idler light.

[0054] It should be noted that the present application does not limit the size of the whispering gallery mode microcavity occupied by the first optical parametric oscillator. Similarly, the size of the whispering gallery mode microcavity occupied by the second optical parametric oscillator is not limited either. For example Figure 1 As shown, the area where the first optical parametric oscillator is located is area A formed by two dotted lines, and the area where the second optical parametric oscillator is located is area B formed by two dotted lines.

[0055] Wherein, the first optical parametric oscillator and the second optical parametric oscillator are two reciprocal lattice vectors, and the intensities of these two reciprocal lattice vectors are related to the angles of the respective fan-shaped areas they occupy. The ratio of the intensity of the first optical parametric oscillator to the intensity of the second optical parametric oscillator is φ1 / φ2. When φ1 = φ2, the intensities of the two reciprocal lattice vectors are equal.

[0056] In the above embodiments, the present application sets two optical parametric oscillators in a whispering gallery microcavity, so that the first pump light coupled into the first optical parametric oscillator is converted into a first signal light and a first idler light. Then, the first signal light is used as the second pump light of the second optical parametric oscillator, so that the second optical parametric oscillator converts the second pump light into a second signal light and a second idler light. Since the wavelength of the second idler light is the same as that of the first idler light and they can be coupled to each other, the second idler light can be coupled with the first idler light into the same idler light, which is enhanced on the basis of the first idler light. Compared with the current whispering gallery microcavity scheme, the theoretical maximum efficiency of converting pump light into idler light is only 50% (that is, the efficiency of converting pump light into idler light is 50%, and the efficiency of converting into signal light is 50%). For the whispering gallery microcavity provided by the present application with two optical parametric oscillators, the theoretical efficiency of converting pump light into idler light can reach 75% (that is, the efficiency of converting the first pump light into the first idler light is 50%, and the efficiency of converting into the first signal light is 50%. Then, the efficiency of converting the first signal light into the second idler light as pump light is 50% (relative to the efficiency of the first pump light is 50%×50% = 25%). Therefore, the total efficiency of converting the first pump light into idler light is 50% + 25% = 75%). Therefore, the whispering gallery microcavity optical parametric oscillator provided by the present application greatly improves the efficiency of converting pump light into idler light.

[0057] In one example, as Figure 1 shown, the whispering gallery microcavity is a disc-shaped structure, and both the first optical parametric oscillator and the second optical parametric oscillator are fan-shaped regions; the first optical parametric oscillator and the second optical parametric oscillator do not overlap; the light wave travels along the circular cavity wall of the whispering gallery microcavity.

[0058] Exemplarily, the first optical parametric oscillator is a semi-circular region, and the second optical parametric oscillator is a semi-circular region, that is, each of them occupies 50% of the whispering gallery microcavity region, and φ1 = φ2 = π.

[0059] In one example, as Figure 2 shown, the first optical parametric oscillator includes at least one first fan-shaped sub-region, which is composed of a first fan-shaped domain structure and a second fan-shaped domain structure with opposite polarization directions. The structural dimensions of each first fan-shaped sub-region are the same, and the light wave travels along the arc-shaped wall of each first fan-shaped sub-region; the arc length of the arc-shaped wall of each first fan-shaped sub-region is the period length Λ of the first optical parametric oscillator 1 As shown in formula (1):

[0060] Λ 1 = θ 1 r, formula (1)

[0061] where, θ 1represents the central angle of each first-sector sub-region, and r is the radius of the whispering-gallery microcavity;

[0062] And, the period length of the first optical parametric oscillator satisfies the following formula (2):

[0063]

[0064] Wherein, represents the wavelength of the first pump light, represents the wavelength of the first signal light, represents the wavelength of the first idler light, represents the effective refractive index of the first pump light transmitted in the whispering-gallery microcavity, represents the effective refractive index of the first signal light transmitted in the whispering-gallery microcavity, represents the effective refractive index of the first idler light transmitted in the whispering-gallery microcavity.

[0065] Wherein, the positive and negative of the nonlinear coefficients of the first-sector domain structure and the second-sector domain structure are opposite.

[0066] In the above example, the period length Λ of the first optical parametric oscillator is set 1 to satisfy formula (2), so that the first optical parametric oscillator can perform phase matching, thereby compensating for the phase mismatch generated during the optical transmission process.

[0067] In one example, the perimeter of the whispering-gallery microcavity is an integer multiple of Λ 1 .

[0068] It should be understood that since the period length Λ of the first optical parametric oscillator 1 = θ 1 r, the perimeter of the whispering-gallery microcavity is 2πr, and the perimeter of the whispering-gallery microcavity is an integer multiple of Λ 1 , that is, "2πr" is an integer multiple of "θ 1 r", which means "2π" is an integer multiple of "θ 1 ", which can be denoted as "M 1 θ 1 = 2π", and M 1 is a positive integer.

[0069] In the above example, by setting the perimeter of the whispering-gallery microcavity to be an integer multiple of Λ 1 , the absolute value of the nonlinear coefficient of the entire superlattice structure of the whispering-gallery microcavity will not decrease. It also avoids the problem that when (M 1 + 0.5)θ 1 = 2π, the absolute value of the nonlinear coefficient of the entire superlattice structure of the whispering-gallery microcavity drops to 0.

[0070] In one example, such as Figure 3As shown, the second optical parametric oscillator includes at least one second sector sub-region, which is composed of a third sector domain structure and a fourth sector domain structure with opposite polarization directions;

[0071] The structural dimensions of each second sector sub-region are the same, and the light wave is transmitted along the arc-shaped wall of each second sector sub-region; the arc length of the arc-shaped wall of each second sector sub-region is the period length of the second optical parametric oscillator:

[0072] Λ 2 = θ 2 r, formula (3)

[0073] where, θ 2 represents the central angle of each first sector sub-region, and r is the radius of the whispering gallery microcavity;

[0074] Moreover, the period length of the second optical parametric oscillator satisfies the following formula:

[0075]

[0076] where, represents the wavelength of the second pump light, represents the wavelength of the second signal light, represents the wavelength of the second idler light, represents the effective refractive index of the second pump light transmitted in the whispering gallery microcavity, represents the effective refractive index of the second signal light transmitted in the whispering gallery microcavity, represents the effective refractive index of the second idler light transmitted in the whispering gallery microcavity.

[0077] Among them, the nonlinear coefficients of the third sector domain structure and the fourth sector domain structure are opposite in sign.

[0078] In the above example, the period length Λ 2 of the second optical parametric oscillator is set to satisfy formula (4), so that the second optical parametric oscillator can perform phase matching, thereby compensating for the phase mismatch generated during the optical transmission process.

[0079] In one example, the perimeter of the whispering gallery microcavity is an integer multiple of Λ 2 .

[0080] It should be understood that since the period length Λ 2 of the second optical parametric oscillator = θ 2 r, the perimeter of the whispering gallery microcavity is 2πr, and the perimeter of the whispering gallery microcavity is an integer multiple of Λ 2 , that is, "2πr" is an integer multiple of "θ 2 r", which means "2π" is an integer multiple of "θ 2 ", which can be denoted as "M 2 θ2 = 2π”, M 2 is a positive integer.

[0081] In the above example, by setting the perimeter of the whispering gallery microcavity to be an integer multiple of Λ 2 , the absolute value of the nonlinear coefficient of the entire superlattice structure of the whispering gallery microcavity will not decrease. It also avoids the problem that when (M 2 + 0.5)θ 2 = 2π, the absolute value of the nonlinear coefficient of the entire superlattice structure of the whispering gallery microcavity drops to 0.

[0082] Combined with the whispering gallery microcavity optical parametric oscillator in the above embodiments, the present application also provides a design method for a whispering gallery microcavity optical parametric oscillator, including:

[0083] (1) Select the material of the whispering gallery microcavity, the radius r of the whispering gallery microcavity, and the operating temperature T of the whispering gallery microcavity;

[0084] (2) The wavelength of the first idler light is the same as the wavelength of the second idler light; determine the wavelength of the first pump light The wavelength of the first signal light The wavelength of the first idler light The wavelength of the second pump light The wavelength of the second signal light and the wavelength of the second idler light where

[0085] (3) According to the wavelength of the first pump light The wavelength of the first signal light and the wavelength of the first idler light determine the period length Λ of the first optical parametric oscillator 1 , according to the wavelength of the second pump light The wavelength of the second signal light and the wavelength of the second idler light determine the period length Λ of the second optical parametric oscillator 2 ,

[0086] (4) According to the period length Λ of the first optical parametric oscillator 1 and the period length Λ of the second optical parametric oscillator 2 , determine the number Q of the first sector regions in the first optical parametric oscillator 1 and the number Q of the second sector regions in the second optical parametric oscillator 2 ;

[0087] (5) According to the above parameters, prepare the whispering gallery microcavity optical parametric oscillator through the electric field room temperature polarization process and the mechanical polishing process.

[0088] In the above embodiments, the present application sets the first signal light output by the first optical parametric oscillator as the second pump light output by the second optical parametric oscillator, and the wavelengths of the first idler light and the second idler light are the same, so as to improve the efficiency of the optical parametric oscillator in converting the pump light into the idler light. When designing the above whispering gallery mode optical parametric oscillator, it is necessary to obtain the material of the whispering gallery microcavity, the radius r of the whispering gallery microcavity, the operating temperature T of the whispering gallery microcavity, and the number Q of the first sector regions in the first optical parametric oscillator determined according to the period length Λ of the first optical parametric oscillator 1 and the number Q of the second sector regions in the second optical parametric oscillator determined according to the period length Λ of the second optical parametric oscillator 1 2 2 These parameters, and then prepare the whispering gallery microcavity optical parametric oscillator according to these parameters.

[0089] Exemplarily, the material of the whispering gallery microcavity is selected as a ferroelectric crystal, such as lithium niobate (LiNbO3), lithium tantalate (LiTiO3), potassium titanyl phosphate (KTiOPO4), magnesium-doped lithium niobate crystal (MgO:LiNbO3), etc.

[0090] In one example, step (2) includes:

[0091] According to the material of the whispering gallery microcavity, the corresponding Sellmeier equation, and the mode of the whispering gallery microcavity, determine the refractive index n(T,λ) of light waves with different wavelengths in the material of the whispering gallery microcavity at the operating temperature T;

[0092] Moreover, the optical path of the light wave propagating along the circular cavity wall of the whispering gallery microcavity for one week is shown in the following formula (5):

[0093]

[0094] The light wave in the whispering gallery microcavity satisfies the resonance wavelength formula (6):

[0095] Nλ = L c , formula (6)

[0096] where N represents a positive integer;

[0097] And the light wave in the second-order nonlinear process of the first optical parametric oscillator satisfies the energy conservation equation as shown in the following formula (7):

[0098]

[0099] The light wave in the second-order nonlinear process of the second optical parametric oscillator satisfies the energy conservation equation as shown in the following formula (8):

[0100]

[0101] Determine the wavelength of the first pump light The wavelength of the first signal light The wavelength of the first idler light The wavelength of the second pump light The wavelength of the second signal light and the wavelength of the second idler light

[0102] In the above manner, the wavelengths of the above-mentioned various light waves can be accurately determined, so as to subsequently determine the period length Λ of the first optical parametric oscillator 1 , and determine the period length Λ of the second optical parametric oscillator 2 .

[0103] In one example, according to the optical waves in the second-order nonlinear process in the first optical parametric oscillator, the momentum conservation equation is satisfied as the following formula (9):

[0104]

[0105] Determine the period length Λ of the first optical parametric oscillator 1 ;

[0106] The optical waves in the second-order nonlinear process in the second optical parametric oscillator satisfy the momentum conservation equation as the following formula (10):

[0107]

[0108] Determine the period length Λ of the second optical parametric oscillator 2 .

[0109] The above manner can accurately determine the period length Λ of the first optical parametric oscillator 1 , and the period length Λ of the second optical parametric oscillator 2 , so as to subsequently determine the number Q of the first sector regions in the first optical parametric oscillator 1 、and the number Q of the second sector regions in the second optical parametric oscillator 2 .

[0110] In one example, according to the perimeter of the whispering gallery microcavity being an integer multiple of the period length Λ of the first optical parametric oscillator 1 i.e., M 1 Λ 1 = 2πr, where Λ 1 = θ 1 r, M 1 is a positive integer, θ 1 is the central angle of the first sector sub-region;

[0111] According to the circumference of the whispering gallery microcavity, the period length of the second optical parametric oscillator is Λ 2 An integer multiple of M 2 Λ 2 =2πr, where Λ 2 =θ 2 r,M 2 is a positive integer, θ 2 is the central angle of the second sector sub-area;

[0112] The whispering gallery microcavity includes a first optical parametric oscillator and a second optical parametric oscillator. The number Q of the first fan-shaped regions in the first optical parametric oscillator is 1 M 1 / 2, and the number Q of the second sector area in the second optical parametric oscillator 2 M 2 / 2 rounded up.

[0113] In the above method, the perimeter of the whispering gallery microcavity is the period length Λ of the first optical parametric oscillator. 1 The angle corresponding to the first fan-shaped area is determined by an integer multiple of 2 The angle corresponding to the second fan-shaped area is determined by an integer multiple of , so that the absolute value of the nonlinear coefficient of the entire superlattice structure of the whispering gallery microcavity will not be reduced.

[0114] The following example illustrates the design steps of a whispering gallery microcavity optical parametric oscillator:

[0115] (1) Magnesium-doped lithium niobate crystal is selected as the material of the whispering gallery microcavity. The radius of the whispering gallery microcavity is r = 2.5 mm, and the operating temperature of the whispering gallery microcavity is T = 24°C.

[0116] (2) Based on the Sellmeier equation of magnesium-doped lithium niobate crystal and the mode of the whispering gallery microcavity, the refractive index n(T,λ) of light waves of different wavelengths in the material of the whispering gallery microcavity is determined at an operating temperature of T = 24°C.

[0117] According to the above formula (5), formula (6), formula (7), formula (8), and Four matching wavelengths can be calculated:

[0118] (3) Further, according to formula (9), the period length Λ of the first optical parametric oscillator is determined 1 =31.416 μm, according to formula (10), determine the period length Λ of the second optical parametric oscillator 2 =34.222μm.

[0119] (4) According to that the perimeter of the whispering gallery microcavity is an integer multiple of the period length Λ of the first optical parametric oscillator, i.e., M 1 Λ 1 Λ 1 = 2πr, where M 1 is a positive integer, calculate M 1 = 500,

[0120] According to that the perimeter of the whispering gallery microcavity is an integer multiple of the period length Λ of the second optical parametric oscillator, i.e., M 2 Λ 2 Λ 2 = 2πr, where Λ 2 = θ 2 r, and M 2 is a positive integer, calculate M 2 = 459, The finally obtained polarization pattern of the whispering gallery microcavity is as shown in Figure 2 or Figure 3 : on the left is the small period, with 250 periods arranged; on the right is the large period, with 229 periods arranged.

[0121] (5) Adopt a Z-cut LiNbO3 crystal with a thickness of 200 μm, and fabricate a domain inversion structure through the electric field room temperature polarization process, that is, the periodic structure with opposite positive and negative nonlinear coefficients in Figure 2 or Figure 3 . Through the mechanical polishing method, with the polarization center as the center of the circle, polish the edge into a disk with a diameter of 5 mm.

[0122] Adopt the prism coupling method to couple the linearly polarized light with a wavelength of into the whispering gallery microdisk, and control the temperature of the microdisk at 24 °C. At this time, through the second-order nonlinear process and the polarization period on the left side of the microdisk for matching, generate and two-wavelength lasers. The power gradually increases in the microdisk. When reaching the threshold, generate and two-wavelength lasers, and and happen to have the same wavelength, so that the idler light output from the whispering gallery microcavity is enhanced, and the output efficiency of the idler light is improved.

[0123] The basic principles of the present application have been described above in connection with specific embodiments. However, it should be noted that the advantages, benefits, effects, etc. mentioned in the present application are only examples and not limitations, and it cannot be considered that these advantages, benefits, effects, etc. are essential for each embodiment of the present application. Additionally, the specific details disclosed above are only for illustrative and facilitative understanding purposes and not limitations, and these details do not limit the present application to necessarily implementing with the above specific details.

[0124] It should be understood that although the steps in the flowchart of the accompanying drawings are shown sequentially in the direction of the arrows, these steps are not necessarily executed sequentially in the direction of the arrows. Unless there is a clear indication in this document, the execution of these steps is not strictly limited in order and can be executed in other orders. Moreover, at least some of the steps in the flowchart of the accompanying drawings may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time but can be executed at different times, and their execution order is not necessarily sequential but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps.

[0125] The block diagrams of the devices, apparatuses, equipment, and systems involved in the present application are only illustrative examples and do not intend to require or imply that they must be connected, arranged, and configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, equipment, and systems can be connected, arranged, and configured in any manner. Words such as "including", "comprising", "having", etc. are open-ended terms meaning "including but not limited to" and can be used interchangeably with each other. The word "or" and "and" used herein refer to the word "and / or" and can be used interchangeably with it, unless the context clearly indicates otherwise. The word "such as" used herein refers to the phrase "such as but not limited to" and can be used interchangeably with it.

[0126] It should also be noted that in the devices, equipment, and methods of the present application, each component or each step can be decomposed and / or recombined. These decompositions and / or recombinations should be regarded as equivalent solutions of the present application.

[0127] The above description of the disclosed aspects enables any person skilled in the art to make or use the present application. Various modifications to these aspects are very obvious to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of the present application. Therefore, the present application is not intended to be limited to the aspects shown herein, but rather to the broadest scope consistent with the principles and novel features disclosed herein.

[0128] The foregoing description has been presented for purposes of illustration and description. In addition, this description is not intended to limit embodiments of the present application to the forms disclosed herein. Although several example aspects and embodiments have been discussed above, those skilled in the art will recognize some variations, modifications, alterations, additions, and subcombinations thereof.

Claims

1. An optical parametric oscillator based on a whispering gallery microcavity, characterized in that, it includes a first optical parametric oscillator and a second optical parametric oscillator; the first optical parametric oscillator and the second optical parametric oscillator share the same whispering gallery microcavity, the whispering gallery microcavity is a disc-shaped structure, and the first optical parametric oscillator and the second optical parametric oscillator are both fan-shaped regions; the first optical parametric oscillator and the second optical parametric oscillator do not overlap; light waves propagate along the circular cavity wall of the whispering gallery microcavity; couple the first pump light into the whispering gallery microcavity, and the first optical parametric oscillator converts the first pump light into a first signal light and a first idler light through a second-order nonlinear process; the first signal light serves as the second pump light of the second optical parametric oscillator, and the second optical parametric oscillator converts the second pump light into a second signal light and a second idler light through a second-order nonlinear process, wherein, the wavelength of the first signal light is the same as the wavelength of the second pump light, and the wavelength of the first idler light is the same as the wavelength of the second idler light; the first optical parametric oscillator includes at least one first fan-shaped sub-region, and the first fan-shaped sub-region is composed of a first fan-shaped domain structure and a second fan-shaped domain structure with opposite polarization directions; the structural dimensions of each of the first fan-shaped sub-regions are the same, and light waves propagate along the arc-shaped walls of each of the first fan-shaped sub-regions; the arc length of the arc-shaped wall of each of the first fan-shaped sub-regions is the period length of the first optical parametric oscillator: ， Among them, represents the period length of the first optical parametric oscillator, represents the central angle of each of the first sector sub-regions, and the is the radius of the whispering gallery microcavity; and, the period length of the first optical parametric oscillator satisfies the following formula: ， Wherein, represents the wavelength of the first pump light, represents the wavelength of the first signal light, represents the wavelength of the first idler light, represents the effective refractive index of the first pump light transmitted in the whispering gallery microcavity, represents the effective refractive index of the first signal light transmitted in the whispering gallery microcavity, represents the effective refractive index of the first idler light transmitted in the whispering gallery microcavity; The perimeter of the whispering gallery microcavity is an integer multiple of the ; the second optical parametric oscillator includes at least one second fan-shaped sub-region, and the second fan-shaped sub-region is composed of a third fan-shaped domain structure and a fourth fan-shaped domain structure with opposite polarization directions; the structural dimensions of each of the second fan-shaped sub-regions are the same, and light waves propagate along the arc-shaped walls of each of the second fan-shaped sub-regions; the arc length of the arc-shaped wall of each of the second fan-shaped sub-regions is the period length of the second optical parametric oscillator: ， Among them, represents the period length of the second optical parametric oscillator, represents the central angle of each of the second sector sub-regions, and the is the radius of the whispering gallery microcavity; and, the period length of the second optical parametric oscillator satisfies the following formula: ， Among them, represents the wavelength of the second pump light, represents the wavelength of the second signal light, represents the wavelength of the second idler light, represents the effective refractive index of the second pump light transmitted in the whispering gallery microcavity, represents the effective refractive index of the second signal light transmitted in the whispering gallery microcavity, represents the effective refractive index of the second idler light transmitted in the whispering gallery microcavity; The perimeter of the whispering gallery microcavity is an integer multiple of the .

2. A design method for an optical parametric oscillator based on a whispering gallery microcavity, which is used to design the optical parametric oscillator based on a whispering gallery microcavity as described in claim 1, characterized in that, it includes: (1) Select the material of the whispering gallery microcavity, the radius of the whispering gallery microcavity and the operating temperature of the whispering gallery microcavity ; (2) The wavelength of the first idler light is the same as that of the second idler light; determine the wavelength of the first pump light , the wavelength of the first signal light , the wavelength of the first idler light , the wavelength of the second pump light , the wavelength of the second signal light and the wavelength of the second idler light , where , ; (3) According to the wavelength of the first pump light , the wavelength of the first signal light and the wavelength of the first idler light , determine the period length of the first optical parametric oscillator , according to the wavelength of the second pump light , the wavelength of the second signal light and the wavelength of the second idler light , determine the period length of the second optical parametric oscillator , (4) According to the period length of the first optical parametric oscillator and the period length of the second optical parametric oscillator , determine the number of the first sector sub-regions in the first optical parametric oscillator and the number of the second sector sub-regions in the second optical parametric oscillator ; (5) According to the parameter , a whispering gallery mode optical parametric oscillator is prepared by an electric field room temperature polarization process and a mechanical polishing process.

3. According to the design method for an optical parametric oscillator based on a whispering gallery microcavity as described in claim 2, characterized in that, step (2) includes: Determine the operating temperature according to the material of the whispering gallery microcavity, the corresponding Sellmeier equation, and the mode of the whispering gallery microcavity At [temperature], the refractive indices of light waves with different wavelengths in the material of the whispering gallery microcavity ; The optical path for the light wave to travel one round along the circular cavity wall of the whispering gallery microcavity is as follows: The light wave in the whispering gallery microcavity satisfies the resonance wavelength formula: where N represents a positive integer; And the light wave in the second-order nonlinear process of the first optical parametric oscillator satisfies the energy conservation equation: and the light wave in the second-order nonlinear process of the second optical parametric oscillator satisfies the energy conservation equation: , Determine the wavelength of the first pump light , the wavelength of the first signal light , the wavelength of the first idler light , the wavelength of the second pump light , the wavelength of the second signal light and the wavelength of the second idler light .

4. According to the design method for an optical parametric oscillator based on a whispering gallery microcavity as described in claim 3, characterized in that, step (3) includes: According to the optical wave in the second-order nonlinear process in the first optical parametric oscillator satisfying the momentum conservation equation: , determine the period length of the first optical parametric oscillator ; The light waves in the second optical parametric oscillator during the second-order nonlinear process satisfy the momentum conservation equation: , to determine the period length of the second optical parametric oscillator .

5. According to the design method for an optical parametric oscillator based on a whispering gallery microcavity as described in claim 4, characterized in that, The perimeter of the whispering gallery microcavity is an integer multiple of the period length of the first optical parametric oscillator, that is wherein , where is a positive integer is the central angle of the first sector sub-region The perimeter of the whispering gallery microcavity is an integer multiple of the period length of the second optical parametric oscillator, i.e., where is a positive integer, and is the central angle of the second sector sub-region. The whispering gallery microcavity further includes the first optical parametric oscillator and the second optical parametric oscillator, then the number of the first sector sub-regions in the first optical parametric oscillator is rounded, and the number of the second sector sub-regions in the second optical parametric oscillator is rounded.

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