All-fiber structure monolithic optical parametric oscillator device based on PPLN waveguide
By designing an all-fiber structure based on periodically polarized lithium niobate waveguides, the problem of poor stability of optical parametric oscillators in complex environments is solved, realizing the application of efficient and low-cost optical parametric oscillators suitable for complex environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- JINAN INST OF QUANTUM TECH
- Filing Date
- 2025-05-12
- Publication Date
- 2026-04-21
AI Technical Summary
Existing optical parametric oscillators have poor stability in complex environments, require strong pump light sources, and are easily affected by environmental factors, making it difficult to achieve all-fiber connectivity and efficient frequency conversion.
A monolithic optical parametric oscillator based on a periodically polarized lithium niobate waveguide is adopted. By coupling it with a low-loss optical fiber through double-end coating and combining it with a temperature control module and a filtering module, a monolithic optical parametric oscillator with an all-fiber structure is realized, avoiding transmission loss of optical components and improving stability and frequency conversion efficiency.
An optical parametric oscillator with high stability and low power requirements in complex environments has been realized, reducing costs and improving frequency conversion efficiency.
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Abstract
Description
Technical Field
[0001] This utility model relates to the field of optoelectronics, specifically to a monolithic optical parametric oscillator device with an all-fiber structure based on a periodically polarized lithium niobate (PPLN) waveguide. Background Technology
[0002] Optical parametric oscillators (OPOs), as important nonlinear optical devices, possess immense application potential in scientific research, spectral analysis, laser communication, and materials processing due to their high efficiency, wide tuning range, and compact design. In practice, however, due to environmental factors and cavity length fluctuations, free-space cavity-based OPOs require active length stabilization to operate, limiting their use outside of optical laboratories. Monolithic OPOs can operate stably even without active cavity length stabilization, and their monolithic integration ensures lower power requirements and greater stability.
[0003] In recent years, with the rapid development of materials science and micro / nano fabrication technology, waveguides based on antiproton exchange periodically polarized lithium niobate have shown unique performance advantages and become a research hotspot in the field of optical parametric oscillators (OPOs). The University of Paderborn, Germany, reported the first synchronously pumped dual-resonant IOPO using a 6.8 cm long Ti:PPLN waveguide resonator, pumped by a mode-locked laser (MLL) at a wavelength of approximately 1550 nm, generating MIR pulses in the wavelength range of 2850–3350 nm. Enrico Pomarico of the University of Geneva, Sergey Orlov, proposed a compact source of narrowband energy-time entangled photon pairs based on a Ti diffused periodically polarized lithium niobate waveguide resonator. This waveguide, with its end-face dielectric multilayer mirrors, forms a monolithic dual-resonant optical parametric oscillator with a bandwidth far below the threshold. It generates photon pairs at approximately 1560 nm through spontaneous parametric down-conversion (SPDC) with a bandwidth of 117 MHz (0.91 pm).
[0004] Currently, the original cavity mirror can be replaced by coating at both ends of the waveguide and using grating structures to achieve stable operation of a monolithic optical parametric oscillator based on a periodically polarized lithium niobate waveguide. However, most experimental schemes still adopt spatial coupling, using a series of collimating devices such as lenses to couple the signal source into the waveguide and collect the beam at the waveguide's output end.
[0005] Figure 1This paper illustrates a miniaturized broadband tunable mid-infrared intracavity optical parametric oscillator (OPO) in the prior art, comprising an LD pump source with a pigtail output, a coupling system mounted within a housing, a mirror, a laser gain crystal, a Q-switch, and an OPO resonant cavity. The laser beam emitted from the LD pump source enters the housing, passes sequentially through the pump coupling system, mirror, laser gain crystal, Q-switch, and OPO resonant cavity, and exits the housing. In this design, the crystal itself cannot be readily integrated with fiber optic devices. Because the beam diverges within the crystal, efficient conversion requires stronger pump light or a longer operating distance. Furthermore, beam recovery after conversion is difficult. Additionally, the OPO requires a stable active length to operate, making it susceptible to environmental factors and cavity length fluctuations. Moreover, the use of a nonlinear crystal necessitates a very strong pump light, often requiring watt-level pump light.
[0006] Figure 2 This paper illustrates a femtosecond monolithic integrated OPO (Optical Parametric Oscillator) in the prior art, which consists of three parts: a diffusion waveguide, a periodically polarized nonlinear surface, and a pair of coated end faces. These form a Fabry-Perot cavity to replace the original cavity mirror, enabling the operation of a monolithic optical parametric oscillator based on a periodically polarized lithium niobate waveguide. Spatial coupling is employed, using lenses and other collimating devices to couple the signal source into the waveguide and collect the beam at the waveguide's output end. While this approach allows for some miniaturization of the system, it still relies on spatial light for experiments, making it difficult to apply in complex environments outside the laboratory. Utility Model Content
[0007] To address the aforementioned problems in existing technologies, this invention proposes a monolithic optical parametric oscillator (OPO) device based on a periodically polarized lithium niobate waveguide. Through a unique design of the monolithic OPO (and its temperature control module) and filtering module, it allows coupling with low-loss optical fiber via double-ended coating, achieving an all-fiber structure OPO device. This results in higher stability compared to spatial optical paths, avoids transmission losses between optical components, improves overall frequency conversion efficiency, and features a simple overall structure, low cost, and applicability to complex environments.
[0008] Specifically, this utility model discloses a monolithic optical parametric oscillator device based on a PPLN waveguide with an all-fiber structure, comprising a pump source, a monolithic optical parametric oscillator, and a filtering module, characterized in that:
[0009] It also includes a temperature control module for controlling the temperature of the monolithic optical parametric oscillator; and...
[0010] The monolithic optical parametric oscillator includes an antiproton exchange periodically polarized lithium niobate waveguide with coatings at both ends. The coatings have high reflectivity and low transmittance for signal photons and idler photons, and high transmittance and low reflectivity for pump photons.
[0011] The filtering module is used to output signal photons and idler photons differently;
[0012] The pump light source is connected to the antiproton exchange periodically polarized lithium niobate waveguide via a single-mode optical fiber, and the antiproton exchange periodically polarized lithium niobate waveguide is connected to the filter module via a single-mode optical fiber.
[0013] Furthermore, the antiproton exchange periodically polarized lithium niobate waveguide is configured to generate signal photons and idler photons based on pump photons through spontaneous parametric downconversion.
[0014] Furthermore, the polarization period Λ of the antiproton exchange periodically polarized lithium niobate waveguide is 19.2 μm.
[0015] Preferably, the antiproton exchange periodically polarized lithium niobate waveguide is encapsulated on a copper plate.
[0016] Preferably, the temperature control module includes a semiconductor cooler.
[0017] Preferably, the pump source comprises a continuous diode laser.
[0018] Furthermore, the filtering module includes a first optical transmission unit, a second optical transmission unit, a first filtering unit, and a second filtering unit;
[0019] The optical transmission unit has a first, a second, and a third port, and photons input from the first port are output through the second port, and photons input from the second port are output through the third port;
[0020] The first filtering unit is configured to reflect only one of the signal photon and the idler photon, and the second filtering unit is configured to reflect only the other of the signal photon and the idler photon;
[0021] The first port and the second port of the first optical transmission unit are respectively connected to the antiproton exchange periodically polarized lithium niobate waveguide and the first filter unit.
[0022] The first port and the second port of the second optical transmission unit are respectively connected to the first filter unit and the second filter unit.
[0023] Preferably, the optical transmission unit is a circulator.
[0024] Preferably, the filtering unit includes a fiber Bragg grating.
[0025] Furthermore, the antiproton exchange periodically polarized lithium niobate waveguide is formed based on Z-cut lithium niobate material. Attached Figure Description
[0026] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.
[0027] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0028] Figure 1 An optical parametric oscillator structure in the prior art is schematically illustrated;
[0029] Figure 2 A femtosecond monolithic integrated OPO structure in the prior art is schematically illustrated;
[0030] Figure 3 The basic structure of the monolithic optical parametric oscillator device based on a PPLN waveguide of this invention is schematically shown.
[0031] Figure 4 A preferred example of the monolithic optical parametric oscillator of this invention is illustrated schematically;
[0032] Figure 5 A preferred example of the filtering module of this utility model is illustrated schematically. Detailed Implementation
[0033] In the following description, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments are provided by way of example to fully convey the spirit of the present invention to those skilled in the art. Therefore, the present invention is not limited to the embodiments disclosed herein.
[0034] Figure 3 The basic structure of the all-fiber monolithic optical parametric oscillator device based on PPLN waveguide of this invention is schematically shown. It includes a pump source, a monolithic optical parametric oscillator, a filtering module and a temperature control module (not shown).
[0035] A pump source is used to provide pump light to a monolithic optical parametric oscillator. As an example, the pump source can be implemented using a continuous diode laser, thereby providing continuous laser pumping for the monolithic optical parametric oscillator.
[0036] A monolithic optical parametric oscillator can be composed of an antiproton exchange periodically polarized lithium niobate waveguide and a double-ended coated cavity mirror, such as... Figure 4 As shown.
[0037] In this invention, an antiproton-exchanged lithium niobate waveguide can be fabricated on a Z-cut lithium niobate substrate, exhibiting low propagation loss (≈0.1 dB cm⁻¹). -1 The distribution of single-mode waveguide (e.g., wavelength approximately 1.55 μm) and TM (transverse magnetic) modes, which overlap well with the modes of standard single-mode fiber, allows for low-loss fiber coupling. After waveguide fabrication, the waveguide is periodically polarized (e.g., with a period of Λ = 19.2 μm) to achieve quasi-phase matching (QPM) of the SPDC at the desired pump wavelength (e.g., approximately 780 nm) and signal and idler wavelengths (e.g., approximately 1.55 μm). Subsequently, a stable monolithic waveguide resonator is formed by coating the two end faces of the waveguide, wherein the coating achieves high reflectivity (low transmittance) at the signal and idler wavelengths, and high transmittance (low reflectivity) at the pump wavelength.
[0038] At this point, the input and output ends of the waveguide can be coupled using pigtails made of standard single-mode optical fibers, thereby allowing the pump source to achieve optical connection with the antiproton exchange periodically polarized lithium niobate waveguide through single-mode optical fiber, and the antiproton exchange periodically polarized lithium niobate waveguide to achieve optical connection with the filter module through single-mode optical fiber, thus realizing all-fiber connection.
[0039] When a continuous-wave diode laser inputs a continuous-pump laser (with a wavelength of approximately 780 nm) into a monolithic optical parametric oscillator, the QPM and energy conservation conditions (ω) are satisfied at a certain temperature. p =ω s +ω i ω j When (j = p, s, i) represent the pump, signal, and idler frequencies respectively, photon pairs (with wavelengths of approximately 1560 nm) are generated from the PPLN waveguide resonator via SPDC, including signal photons and idler photons. The signal and idler photons are preferentially output only when their frequencies match the cavity's resonant mode. The key to achieving this is correctly adjusting the resonant mode of the monolithic waveguide resonator.
[0040] Therefore, in this invention, the temperature control module is used to control the temperature of the monolithic optical parametric oscillator, thereby controlling the output of signal photons and idler photons. Figure 4 In one example, the antiproton exchange periodically polarized lithium niobate waveguide can be entirely encapsulated on a copper substrate and its temperature controlled by, for example, a semiconductor cooler.
[0041] Since the signal and idler photons are in different resonant cavity modes, a filtering module is also provided in this invention to ensure that the signal photons and idler photons from the antiproton exchange periodically polarized lithium niobate waveguide are output differently.
[0042] Figure 5 A preferred example of the filtering module of the present invention is illustrated schematically, which includes a first optical transmission unit, a second optical transmission unit, a first filtering unit, and a second filtering unit.
[0043] In this invention, the optical transmission unit may have a first, a second, and a third port, wherein photons input through the first port are output through the second port, and photons input through the second port are output through the third port.
[0044] As an example, an optical transmission unit can be implemented using a circulator.
[0045] In this invention, the first filtering unit can be configured to reflect only one of the signal photon and the idler photon (e.g., the signal photon λs), while the corresponding second filtering unit can be configured to reflect only the other of the signal photon and the idler photon (e.g., the idler photon λi).
[0046] As an example, the filtering unit can be implemented using a standard fiber Bragg grating (FBG). For instance, the first filtering unit may include a first fiber Bragg grating (FBG). s It has a bandwidth of approximately 1 nm and a wavelength λs required for reflection. The second filtering unit may include a second fiber Bragg grating (FBG). i It also has a wavelength λi required for reflection with a bandwidth of about 1 nm.
[0047] like Figure 5 As shown, by connecting the first port and the second port of the first optical transmission unit to the antiproton-exchanged periodically polarized lithium niobate waveguide and the first filter unit respectively (via optical fiber), and connecting the first port and the second port of the second optical transmission unit to the first filter unit and the second filter unit respectively (via optical fiber), the selective output of signal photons and idler photons output from the antiproton-exchanged periodically polarized lithium niobate waveguide can be achieved by means of an all-fiber structure.
[0048] Taking λs = 1559.5nm and λi = 1561.5nm as examples, the first fiber Bragg grating (FBG) S It can reflect the required wavelength λs, transmit the pump light, and transmit the wavelength λi = 1561.5 nm, thereby allowing the signal photons to finally be output through the third port of the first circulator; the second fiber Bragg grating (FBG) i The desired wavelength λi can be reflected, thus allowing the idler photon to eventually be output through the third port of the second circulator.
[0049] As described above, this invention, through the design of the aforementioned special monolithic optical parametric oscillator (and its temperature control module) and filtering module, allows for coupling with low-loss optical fiber via double-end coating, realizing a monolithic optical parametric oscillator device with an all-fiber structure, making it suitable for more complex application scenarios. Specifically, this invention introduces a structural design implemented by a PPLN waveguide and a double-end coated cavity mirror. The former has an extremely wide transmission range and an extremely high nonlinear coefficient, and allows for integration with fiber optic devices. More significantly, this waveguide structure can confine optical energy to a region with a very small cross-sectional area, effectively improving optical power density, and maintaining good beam constraint throughout the entire optical transmission length, avoiding beam diffraction. The latter forms a cavity mirror by selectively coating each end to provide high reflection and low transmission for frequency-doubled and frequency-doubled light, or high transmission and low reflection for pump signal idler light, ensuring lower power requirements and greater stability. Furthermore, this invention proposes a special filter module design that adopts an all-fiber structure. The overall structure is simple and has higher stability compared to spatial optical paths. At the same time, it can avoid transmission loss between optical components and improve the overall frequency conversion efficiency, enabling the realization of an all-fiber monolithic optical parametric oscillator device. This solution has a simple overall structure, low cost, and can be applied to complex environments.
[0050] Although the present invention has been described above with reference to the accompanying drawings and specific embodiments, those skilled in the art will readily recognize that the above embodiments are merely exemplary and used to illustrate the principles of the present invention. They do not limit the scope of the present invention. Those skilled in the art can make various combinations, modifications and equivalent substitutions to the above embodiments without departing from the spirit and scope of the present invention.
Claims
1. A PPLN waveguide based all-fiber structure monolithic optical parametric oscillator device comprising a pump light source, a monolithic optical parametric oscillator and a filtering module, characterized in that: It also includes a temperature control module for controlling the temperature of the monolithic optical parametric oscillator; and... The monolithic optical parametric oscillator includes an antiproton exchange periodically polarized lithium niobate waveguide with coatings at both ends. The coatings have high reflectivity and low transmittance for signal photons and idler photons, and high transmittance and low reflectivity for pump photons. The filtering module is used to output signal photons and idler photons differently; The pump light source is connected to the antiproton exchange periodically polarized lithium niobate waveguide via a single-mode optical fiber, and the antiproton exchange periodically polarized lithium niobate waveguide is connected to the filter module via a single-mode optical fiber.
2. The all-fiber structure monolithic optical parametric oscillator device of claim 1, wherein, The antiproton exchange periodically polarized lithium niobate waveguide is configured to generate signal photons and idler photons based on pump photons through spontaneous parametric downconversion.
3. The all-fiber structure monolithic optical parametric oscillator device according to claim 2, wherein, The polarization period Λ of the antiproton exchange periodically polarized lithium niobate waveguide is 19.2 μm.
4. The all-fiber structure monolithic optical parametric oscillator device of claim 1, wherein, The antiproton exchange periodically polarized lithium niobate waveguide is encapsulated on a copper plate.
5. The all-fiber structure monolithic optical parametric oscillator device according to claim 4, wherein, The temperature control module includes a semiconductor cooler.
6. The all-fiber structure monolithic optical parametric oscillator device of claim 1, wherein, The pump source includes a continuous diode laser.
7. The all-fiber structure monolithic optical parametric oscillator device according to claim 1, wherein, The filtering module includes a first optical transmission unit, a second optical transmission unit, a first filtering unit, and a second filtering unit; The optical transmission unit has a first, a second, and a third port, and photons input from the first port are output through the second port, and photons input from the second port are output through the third port; The first filtering unit is configured to reflect only one of the signal photon and the idler photon, and the second filtering unit is configured to reflect only the other of the signal photon and the idler photon; The first port and the second port of the first optical transmission unit are respectively connected to the antiproton exchange periodically polarized lithium niobate waveguide and the first filter unit. The first port and the second port of the second optical transmission unit are respectively connected to the first filter unit and the second filter unit.
8. The all-fiber structure monolithic optical parametric oscillator device according to claim 7, wherein, The optical transmission unit is a circulator.
9. The all-fiber structure monolithic optical parametric oscillator device according to claim 7, wherein, The filtering unit includes a fiber Bragg grating.
10. The all-fiber structure monolithic optical parametric oscillator device of any of claims 1-9, wherein, The antiproton exchange periodically polarized lithium niobate waveguide is formed based on Z-cut lithium niobate material.