Single-cavity bidirectional synchronous mode-locked laser

Abstract

The invention relates to the technical field of mode-locked lasers, in particular to a single-cavity bidirectional synchronous mode-locked laser. The single-cavity bidirectional synchronous mode-locked laser comprises a 980nm pumping laser source, a section of erbium-doped optical fiber serving as a gain medium and a resonant cavity. The resonant cavity is composed of a wavelength division multiplexer (WDM), a semiconductor saturable absorber (SA), a polarization controller (PC) and an optical fiber coupler (OC). The light in the clockwise direction and the light in the anticlockwise direction are output through the coupler and are respectively transmitted to a test end through the isolator. The laser shows bidirectional synchronous mode locking in the aspect of time domain output and has about 3 times of power difference, while in the aspect of frequency domain output, the mode locking repetition frequency of the laser reaches 45.6 MHz, and the laser shows stable self-starting characteristic and mode locking duration of more than 10 hours. Meanwhile, the central wavelength of the output spectrum of the laser is 1565 nm, the spectrum range is 1560-1570 nm, and various accurate measurement requirements are met.

Description

Technical Field

[0001] The invention relates to the technical field of mode-locked lasers, and in particular to a single-cavity bidirectional synchronous mode-locked laser. Background Art

[0002] An optical frequency comb is a spectrum consisting of a series of frequency components that are evenly spaced and have a coherent and stable phase relationship. It is similar to a light ruler and can achieve precise measurement of optical frequencies. An optical frequency comb generates ultrashort light pulses through a mode-locked laser. The time intervals between adjacent waves of these pulses are exactly the same, making the optical frequency comb appear as an electromagnetic field oscillation envelope with a time width of femtoseconds in the time domain, and as an optical frequency sequence with equal frequency intervals in the frequency domain.

[0003] As a cutting-edge technology in today's laser and time frequency science, the optical frequency comb effectively links the optical frequency and microwave frequency in the electromagnetic spectrum, providing a high-precision frequency source in a simple and ingenious way. Its application in high-precision frequency measurement, spectroscopy, and time reference makes it increasingly important in scientific research and industrial applications. With the continuous advancement of optical comb technology, dual-comb technology has gradually become a research hotspot due to its unique advantages. In particular, dual-comb asynchronous optical sampling technology has shown wide practicality in the fields of spectral measurement, trace gas detection, and ranging.

[0004] However, there are relatively few studies and reports on dual-comb synchronous mode-locked lasers. Such lasers can be effectively applied to Raman spectroscopy measurement and frequency conversion, which is of great significance for scientific research, especially in high-sensitivity detection. Based on the above background, the present invention proposes a single-cavity bidirectional synchronous mode-locked laser. Summary of the invention

[0005] The object of the present invention is to provide a single-cavity bidirectional synchronous mode-locked laser to solve the problem in the prior art mentioned in the above background technology that there is a lack of research on dual-comb synchronous mode-locked lasers for Raman spectroscopy measurement and frequency conversion.

[0006] To achieve the above object, the present invention provides a single-cavity bidirectional synchronous mode-locked laser, comprising: 980nm pump laser source; gain medium; and a resonant cavity; The gain medium is a section of erbium-doped optical fiber, and the resonant cavity is composed of a wavelength division multiplexer (WDM), a semiconductor saturable absorber (SA), a polarization controller (PC) and an optical fiber coupler (OC).

[0007] As a further improvement of the technical solution, the 980nm pump laser source is used to emit a light beam with a wavelength of 980nm and provide excitation energy to drive the erbium ions in the erbium-doped fiber to provide fiber gain, thereby improving the overall output power of the laser.

[0008] As a further improvement of the technical solution, the gain medium is used to amplify the optical signal propagating through the optical fiber, and utilizes the transition characteristics of erbium ions to generate high-energy laser output under the excitation of 980nm pump light to meet the output requirements of the laser.

[0009] As a further improvement of the present technical solution, the resonant cavity is used to form light feedback and enhancement, and the laser signal is propagated multiple times in the cavity through reflection and interference effects, thereby realizing laser mode selection and power amplification, ensuring stable mode-locked output and improving the frequency stability of the laser.

[0010] As a further improvement of the technical solution, the wavelength division multiplexer (WDM) is used to integrate optical signals of different wavelengths, reflect the 980nm pump light, and transmit the 1550nm signal light.

[0011] As a further improvement of the technical solution, the semiconductor saturable absorber (SA) is used as a mode-locking device. Each time the light pulse circulates in the resonant cavity, it passes through the working medium and the saturable absorber. The stimulated radiation amplification effect of the working medium and the nonlinear loss of the saturable absorber will change the intensity value of the pulse at different positions. Since the saturable absorber has a low transmittance and a large absorption coefficient for weak incident light, the weak light suffers a large loss. However, the transmittance for strong incident light is high and the absorption coefficient is small, so that the strong light suffers less loss after passing through the saturable absorber. After the light pulse circulates multiple times in the resonant cavity, the edge part with weaker light intensity is absorbed, and the pulse peak part can pass effectively. The pulse width is reduced and continuously narrowed to form an ultra-short pulse, realizing mode-locked output.

[0012] As a further improvement of the present technical solution, the polarization controller (PC) is used to adjust the polarization state of the laser output light. By precisely controlling the polarization direction, the desired laser characteristics can be achieved in different applications. The fiber coupler (OC) is used to effectively couple the optical signal in the resonant cavity to output. The accurate coupling mechanism ensures that the laser signal can be effectively transmitted to the subsequent measurement application end and achieves a higher system integration.

[0013] As a further improvement of the technical solution, the laser achieves bidirectional synchronous mode locking through optical coupling output in clockwise and counterclockwise directions, and the laser output power in the clockwise and counterclockwise directions has a power difference of 3 times.

[0014] As a further improvement of the technical solution, the mode-locking repetition rate of the laser is 45.6 MHz. The design of this frequency enables the laser to maintain a long-term mode-locking state, truly realizing ultra-long-term laser output stability. The mode-locking duration exceeds 10 hours, showing excellent operating performance.

[0015] As a further improvement of the present technical solution, the central wavelength of the laser output spectrum is 1565nm, and its spectral range is 1560-1570nm, which is suitable for a variety of wavelength selection and application scenarios, ensuring that various spectral analysis and measurement requirements are met.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The single-cavity bidirectional synchronous mode-locked laser has high stability: Due to the mode-locking mechanism, the laser can achieve long-term stable output, and the mode-locking time exceeds 10 hours, thus meeting long-term experimental needs.

[0018] 2. The single-cavity bidirectional synchronous mode-locked laser has high frequency accuracy: through the bidirectional synchronous mode-locking method, the laser power difference can be effectively reduced, thereby improving the accuracy and reliability of the measurement, which is particularly important for high-sensitivity applications such as Raman spectroscopy measurement.

[0019] 3. The single-cavity bidirectional synchronous mode-locked laser has a wide spectrum output: the central wavelength of the laser output spectrum is 1565nm, covering the range of 1560-1570nm, which can meet various spectral measurement needs and expand its potential for use in trace gas detection and other spectral applications.

[0020] 4. The single-cavity bidirectional synchronous mode-locked laser has excellent self-starting capability: the output characteristic of the mode-locked repetition rate of 45.6MHz ensures that the laser has a fast response capability, enabling it to meet the requirements of real-time monitoring and precise measurement.

[0021] 5. This single-cavity bidirectional synchronous mode-locked laser has broad application prospects: the design of this laser can be flexibly applied to scientific research fields such as Raman spectroscopy measurement and frequency conversion, and promote the development of related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the single-cavity bidirectional synchronous mode-locked laser of the present invention.

[0023] Figure 2 This is a time domain schematic diagram of the output of the single-cavity bidirectional synchronous mode-locked laser of the present invention.

[0024] Figure 3 Schematic diagram of the output spectrum of the single-cavity bidirectional synchronous mode-locked laser of the present invention.

[0025] Figure 4 Schematic diagram of the output spectrum of the single-cavity bidirectional synchronous mode-locked laser in the present invention. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In a specific embodiment, the present invention provides a single-cavity bidirectional synchronous mode-locked laser, such as Figure 1 The figure shows the schematic diagram of the structure of the single-cavity bidirectional synchronous mode-locked laser of the present invention, which is composed of a 980nm pump laser source, a gain medium and a resonant cavity. The gain medium is a section of erbium-doped fiber. The resonant cavity is composed of a wavelength division multiplexer (WDM), a semiconductor saturable absorber (SA), a polarization controller (PC) and an optical fiber coupler (OC). The light in the clockwise and counterclockwise directions is output through the coupler and then output to the test end through the isolator.

[0028] The 980nm pump laser source is the core component of this single-cavity bidirectional synchronous mode-locked laser. Its main function is to provide light energy for exciting the gain medium (erbium-doped fiber). The wavelength of 980nm is selected based on the fact that erbium ions have the best absorption characteristics in optical fibers. Through efficient light conversion, the 980nm laser can effectively excite erbium ions into an excited state, thereby providing the necessary conditions for the generation of optical fiber gain.

[0029] At the same time, 980nm pump laser sources usually have high electro-optical conversion efficiency, stable output power and good long-term working stability. The laser is designed to maintain the stability of its output power under different working conditions. This feature is crucial to ensure the subsequent laser gain effect.

[0030] In the design of the pump source, by adjusting the laser spot size and divergence angle, the pump light is effectively coupled into the erbium-doped fiber, thereby improving the transmission efficiency of light energy. Whether in single-mode fiber or multi-mode fiber, the design of the equipment ensures full utilization of light.

[0031] The erbium-doped fiber in the gain medium is made of special materials and doped with a certain concentration of erbium ions. The concentration of erbium ions and doping technology directly affect the gain characteristics of the fiber. Standard erbium-doped fiber has high gain and wide gain bandwidth, allowing the laser to support a variety of signal frequencies.

[0032] The gain mechanism is that under the stimulation of 980nm pump light, the erbium ions in the erbium-doped fiber undergo transitions and enter a high-energy state, and under appropriate conditions, the energy is released, forming a strong amplification effect. This gain characteristic affects the intensity and quality of the laser output and is a key link in laser design.

[0033] When selecting the solute and the structure of the optical fiber, factors such as the required laser wavelength, optical fiber length, and erbium ion concentration must be taken into account. In addition, the waveguide structure of the optical fiber is also optimized to ensure efficient light transmission and low loss.

[0034] In addition, the resonant cavity is an important part to guide and enhance the laser output and has a variety of optical components.

[0035] The wavelength division multiplexer (WDM) is used to integrate optical signals of different wavelengths and separate the 980nm pump light from the laser output light to ensure that they do not interfere with their respective propagation paths, thereby improving overall efficiency.

[0036] Semiconductor saturable absorber (SA) is used as a mode-locking device to adjust the laser output frequency. After reaching a certain intensity, the absorber will quickly saturate, allowing more light signals to pass through, effectively promoting the formation of the mode-locking effect.

[0037] Polarization controller (PC) is used to adjust the polarization state of laser output light to optimize the path and intensity of laser output transmission. By precisely controlling the polarization direction, the desired laser characteristics can be achieved in different applications.

[0038] The fiber coupler (OC) is used to effectively couple the optical signal in the resonant cavity. The accurate coupling mechanism ensures that the laser signal can be effectively transmitted to the subsequent measurement application end and achieves a higher system integration.

[0039] In actual applications, in the resonant cavity, the optical signal can propagate in both clockwise and counterclockwise directions. Through reasonable design, the optical signals in the two directions interfere with each other to form a bidirectional synchronous mode-locked state. The laser output signal in this state shows high-frequency stability and can meet the needs of various precision measurements. Figure 2 The figure shows the time domain output of a single-cavity bidirectional synchronous mode-locked laser. The laser output power in the clockwise and counterclockwise directions has a power difference of 3 times. This feature provides greater flexibility for subsequent applications, allowing better signal processing and signal-to-noise ratio to be achieved under certain conditions.

[0040] The single-cavity bidirectional synchronous mode-locked laser exhibits bidirectional synchronous mode-locking characteristics in the time domain output. Figure 3The figure shows the output spectrum of a single-cavity bidirectional synchronous mode-locked laser. In the frequency domain output, its mode-locked repetition rate reaches 45.6MHz. This high frequency ensures that the laser can continuously and stably provide laser output, which is suitable for dynamic measurement and rapid response application scenarios. Its mode-locked duration exceeds 10 hours, showing excellent operating performance. This is an important consideration in the design of modern lasers. Stable output can effectively avoid performance degradation caused by environmental changes during long-term operation, ensuring the reliability of laser equipment in practical applications.

[0041] In addition, if Figure 4 The figure shows a schematic diagram of the output spectrum of a single-cavity bidirectional synchronous mode-locked laser. The central wavelength of the output spectrum of the single-cavity bidirectional synchronous mode-locked laser is 1565nm, and the Kelly sidebands are symmetrically distributed on the spectrum. By adjusting the polarization controller or increasing the pump power, the output central wavelength can be changed to meet the needs of various applications. This wavelength is particularly important in the field of fiber-optic communications because it is within the low-loss window of standard fiber-optic communications. The spectral range of the laser is 1560-1570nm. The wide output spectral range enables the laser to adapt to a variety of different communication protocols and equipment requirements. In addition, the stable output also makes it suitable for spectral analysis, sensor applications and other occasions. It can adapt to a variety of spectral measurement needs and expand its potential for use in trace gas detection and other spectral applications.

[0042] In summary, compared with the prior art, the single-cavity bidirectional synchronous mode-locked laser has the following outstanding beneficial effects: The single-cavity bidirectional synchronous mode-locked laser has high stability: due to the mode-locking mechanism, the laser can achieve long-term stable output, and the mode-locking time exceeds 10 hours, thus meeting the needs of long-term experiments; The single-cavity bidirectional synchronous mode-locked laser has high frequency accuracy: through bidirectional synchronous mode-locking, the laser power difference can be effectively reduced, thereby improving the accuracy and reliability of the measurement, which is particularly important for high-sensitivity applications such as Raman spectroscopy measurement; The single-cavity bidirectional synchronous mode-locked laser has a wide spectrum output: the central wavelength of the laser output spectrum is 1565nm, covering the range of 1560-1570nm, which can meet the needs of various spectral measurements and expand its potential for use in trace gas detection and other spectral applications; The single-cavity bidirectional synchronous mode-locked laser has excellent self-starting capability: the output characteristic of the mode-locked repetition rate of 45.6MHz ensures that the laser has a fast response capability, enabling it to meet the requirements of real-time monitoring and precise measurement; This single-cavity bidirectional synchronous mode-locked laser has broad application prospects: the design of this laser can be flexibly applied to scientific research fields such as Raman spectroscopy measurement and frequency conversion, and promote the development of related technologies.

[0043] With the growing demand for high-precision optical communication and measurement, this single-cavity bidirectional synchronous mode-locked laser has broad application prospects. It can be used in the fields of optical communication, measurement and sensing, medical applications, and industrial laser systems.

[0044] In fiber-optic communication systems, lasers with high stability and good gain performance can significantly improve the quality and speed of signal transmission, helping to promote the development of next-generation communication technologies.

[0045] Its high frequency and stable mode-locking characteristics are suitable for use in precision measurement equipment and sensors, such as fiber optic sensors, environmental monitoring, etc. This provides strong technical support for real-time monitoring of environmental conditions, structural changes, etc.

[0046] In the medical field, technology based on this laser can be used in laser therapy, imaging and diagnostic equipment, providing higher accuracy and faster treatment effects.

[0047] In industrial applications, lasers can be used in scenarios such as laser cutting, engraving, and material processing. With their high power and stability, they can achieve higher production efficiency at a lower cost.

[0048] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A single-cavity bidirectional synchronous mode-locked laser, characterized in that: include: 980nm pump laser source; gain medium; and a resonant cavity; The gain medium is a section of erbium-doped optical fiber, and the resonant cavity is composed of a wavelength division multiplexer, a semiconductor saturable absorber, a polarization controller and an optical fiber coupler.

2. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The 980nm pump laser source is used to emit a light beam with a wavelength of 980nm and provide excitation energy to excite the erbium ion transition in the erbium-doped optical fiber and provide optical fiber gain.

3. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The gain medium is used to amplify the optical signal propagating through the optical fiber.

4. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The resonant cavity is used to form light feedback and enhancement, and the laser signal is propagated multiple times in the cavity through reflection and interference effects.

5. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The wavelength division multiplexer (WDM) is used to integrate optical signals of different wavelengths, reflect the 980nm pump light, and transmit the 1550nm signal light.

6. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The semiconductor saturable absorber is used as a mode locking device to achieve phase locking between longitudinal modes in the cavity.

7. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The polarization controller is used to adjust the polarization state of the laser output light to achieve synchronous mode locking in two directions, and the optical fiber coupler is used to effectively couple the optical signal in the resonant cavity to output.

8. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The laser achieves bidirectional synchronous mode locking through optical coupling output in clockwise and counterclockwise directions, and the laser output power in the clockwise and counterclockwise directions has a power difference of 3 times.

9. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The mode-locking repetition rate of the laser is 45.6 MHz, and the mode-locking duration is more than 10 hours.

10. The single-cavity bidirectional synchronous mode-locked laser according to claim 1, characterized in that: The central wavelength of the laser output spectrum is 1565nm, and its spectrum range is 1560-1570nm.

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