Novel narrow linewidth laser device

Abstract

The invention provides a novel narrow-linewidth laser device which comprises a laser diode (1) serving as a light source of the narrow-linewidth laser device; the collimating lens (2) is used for converting a light source output by the laser diode into parallel light; the convergent lens (3) and parallel light formed by the laser diode through the collimating lens are converged to a focal point and are coupled to enter the optical fiber (4); the optical fiber (4) is a special structure optical fiber which is formed through special treatment and has relatively low reflectivity, and is used for reflecting the output laser beam back to the laser diode (1); and the two-stage optical isolator (5) isolates the structures such as the laser diode, the collimating lens, the convergent lens and the optical fiber with high isolation so as to prevent the reflected light beams from influencing the structures.

Description

Technical Field

[0001] The present invention relates to the technical field of lasers, and in particular to a narrow line width laser. Background Art

[0002] Narrow linewidth lasers are lasers with narrow spectral linewidth, which means that the wavelength of light they emit is very stable, with high coherence and low noise characteristics. They are often used in high-precision spectroscopy, laser interferometry, quantum communication and quantum computing, medical imaging and treatment. In addition, narrow linewidth lasers in the hundreds of hertz range are widely used in optical fiber communications.

[0003] Traditional all-solid-state narrow-linewidth lasers require optical pumping, are large in size, heavy in weight, and difficult to integrate. Semiconductor lasers with on-chip heterogeneous integration or monolithic integration are usually more expensive, and external cavity lasers have complex structures and poor stability. In addition, although some structures can produce narrow-linewidth lasers, due to the complex structure of the external cavity, there are large losses, resulting in low output power. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In order to balance the complexity and stability of narrow linewidth laser structures, as well as the production, manufacturing, and packaging costs of lasers, a certain output power can be guaranteed while narrowing the laser linewidth, while reducing the complexity of the structure and the noise of the laser, thereby meeting the growing demand for narrow linewidth lasers in coherent communications.

[0006] (II) Technical solution

[0007] In view of the above technical problems, the embodiments of the present disclosure provide a novel narrow linewidth laser device.

[0008] A novel narrow linewidth laser device, which includes: a laser diode, which serves as the light source of the narrow linewidth laser device; a collimating lens, which converts the light source output by the laser diode into parallel light; a converging lens, which converges the parallel light formed by the laser diode through the collimating lens to a focus and couples it into an optical fiber; an optical fiber, which is a special structure optical fiber with low reflectivity formed by special treatment, which reflects the output laser beam back to the laser diode; a double-stage optical isolator, which isolates the laser diode, the collimating lens, the converging lens, the optical fiber and other structures with high isolation to prevent the reflected light beam from affecting the aforementioned structures.

[0009] In some exemplary embodiments, the laser diode operates under a specified current and voltage environment, and emits laser light with a wavelength of 1550 nm.

[0010] In some exemplary embodiments, under the action of a collimating lens, the light source output by a laser diode is converted into parallel light.

[0011] In some exemplary embodiments, under the action of a converging lens, parallel light from a laser diode formed by a collimating lens converges to a focal point and is coupled into an optical fiber or other structures described below.

[0012] In some exemplary embodiments, a collimating lens is used in combination with a converging lens to efficiently couple the laser light source generated by a laser diode into an optical fiber.

[0013] In some exemplary embodiments, an optical fiber or other structure described below having a lower reflectivity formed by special processing reflects the output laser beam back to the laser diode; In some exemplary embodiments, the optical fiber uses polarization-maintaining optical fiber. Optionally, an optical fiber with a small bending radius is used to reduce the impact of environmental factors such as bending and vibration on the transmission characteristics of the optical fiber.

[0014] In some exemplary embodiments, the optical fiber uses Rayleigh scattering enhanced optical fiber, so that the output light passes through a longer section of Rayleigh scattering enhanced optical fiber and is slightly reflected, and the output laser beam is reflected back to the laser diode.

[0015] In some exemplary embodiments, the optical fiber is replaced with a very low reflectivity grating to reflect the output laser beam back to the laser diode.

[0016] In some exemplary embodiments, ultraviolet light irradiation, arc discharge, etc. may be used to prepare Rayleigh scattering enhanced optical fiber.

[0017] In some exemplary embodiments, an ultra-weak Bragg grating is introduced into the optical fiber to achieve a small amount of reflection of the input light and reflect the output laser beam back to the laser diode.

[0018] In some exemplary embodiments, a double-stage optical isolator is used, which has a greater isolation. The isolation of the double-stage optical isolator should be greater than 55dB. The double-stage optical isolator isolates structures such as laser diodes, collimating lenses, converging lenses, and optical fibers to prevent reflected light beams from affecting the above structures.

[0019] (III) Beneficial effects

[0020] (1) A narrow linewidth laser with a linewidth of hundreds of Hz, specifically 542.2 Hz, and a suitable narrow linewidth laser output power of 12.059 mW.

[0021] (2) Frequency noise is less than 15Hz / Hz in the frequency range of 3kHz to 100kHz 1 / 2 .

[0022] (3) Simple structure, easy to manufacture and package, low cost, and high stability and reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a disclosed embodiment of a novel narrow linewidth laser device.

[0024] Figure 2 Schematic diagram of the principle of scattering-enhanced fiber.

[0025] Figure 3 Other options for scattering-enhanced fibers.

[0026] Figure 4 Power test data of the new narrow linewidth laser device.

[0027] Figure 5 Spectral plot of the new narrow-linewidth laser device.

[0028] Figure 6 Phase noise test results of three replicates of the novel narrow-linewidth laser setup.

[0029] Figure 7 The linewidth of a new narrow-linewidth laser device measured using the phase noise method.

[0030] Reference numerals: 1-Laser diode; 2-Collimating lens; 3-Converging lens; 4-Optical fiber; 5-Dual-stage optical isolator; 6-Rayleigh scattering point; 7-Discrete scattering enhancement point; 8-Ultraweak fiber Bragg grating; 9-Particle doping DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present disclosure.

[0032] The present disclosure provides a schematic diagram of a novel narrow linewidth laser device. Figure 1 As shown, a novel narrow linewidth laser device includes: a laser diode 1; a collimating lens 2; a converging lens 3; an optical fiber 4 and a double-stage optical isolator 5; the double-stage optical isolator 5 isolates structures such as the laser diode 1, the collimating lens 2, the converging lens 3, the optical fiber or the grating 4 with a high degree of isolation to prevent the reflected light beam from affecting the aforementioned structures.

[0033] The laser diode 1 operates under a specified current and voltage environment, and emits laser light with a wavelength of 1550 nm.

[0034] Under the action of the collimating lens 2, the light source output by the laser diode 1 is converted into parallel light.

[0035] Under the action of the converging lens 3, the parallel light formed by the laser diode 1 through the collimating lens 2 converges to the focus and is coupled into the optical fiber or other structures described below.

[0036] The collimating lens 2 and the converging lens 3 are used in combination to efficiently couple the laser light source generated by the laser diode 1 into the optical fiber, thereby increasing the output power of the narrow linewidth laser and improving the comprehensive performance of the narrow linewidth laser.

[0037] The optical fiber or other structure 4 described below, which has a lower reflectivity after special processing, reflects the output laser beam back to the laser diode 1.

[0038] The optical fiber 4 with lower reflectivity formed by special treatment uses polarization-maintaining optical fiber. In the laser system, polarization-maintaining optical fiber is used to maintain the polarization state of the laser output and improve the quality and consistency of the laser beam. Optionally, an optical fiber that can be bent with a small bending radius is used to reduce the influence of external factors such as bending and vibration on the transmission characteristics of the optical fiber.

[0039] The optical fiber 4 with lower reflectivity formed by special treatment is subjected to Rayleigh scattering enhancement, so that the output light is reflected slightly through a longer section of Rayleigh scattering enhancement optical fiber, and the output laser beam is reflected back to the laser diode 1.

[0040] The principle of scattering enhanced fiber is as follows Figure 2 As shown, there are Rayleigh scattering points in the scattering enhanced optical fiber, which generate scattered light beams with random scattering intensity and scattering positions. The scattered light beams are fed back into the system composed of the laser diode 1, the collimating lens 2, and the converging lens 3, thereby narrowing the line width of the laser emitted by the narrow line width laser device.

[0041] In some exemplary embodiments, ultraviolet light irradiation, arc discharge, particle doping, etc. can be used to prepare Rayleigh scattering enhanced optical fiber.

[0042] Optionally, a scattering-enhanced microstructure is provided in the optical fiber, thereby periodically increasing discrete scattering-enhanced points, the scattering intensity of the scattering-enhanced points being much greater than the scattering intensity of the Rayleigh scattering points.

[0043] Other options for scattering-enhanced optical fibers include Figure 3 As shown, 8 is ultra-weak fiber Bragg grating; 9 is particle doping.

[0044] Optionally, scattering enhancement is achieved by ultraviolet light irradiation. Rayleigh scattering enhancement achieved by ultraviolet light irradiation is based on the photosensitivity of the optical fiber material to ultraviolet light. The refractive index of the optical fiber material changes during ultraviolet exposure.

[0045] In some exemplary embodiments, the ultraviolet light irradiation method described above is used to introduce an ultra-weak Bragg grating or a colorless weak reflection point array into the optical fiber to achieve a small amount of reflection of the input light, and reflect the output laser beam back to the laser diode.

[0046] Optionally, femtosecond laser etching technology is used for microstructure processing. Femtosecond laser has a large power, and when high power is used to irradiate the optical fiber, nonlinear absorption is generated, and then the refractive index of the optical fiber changes. This method can be used to design and manufacture microstructures.

[0047] Optionally, Rayleigh scattering enhancement can be achieved by using particle doping technology during the preparation of optical fibers. Rayleigh scattering is the phenomenon of light scattering on molecules or small particles (usually smaller than the wavelength of light), and the intensity of the scattering is inversely proportional to the fourth power of the wavelength of light. In addition, Rayleigh scattering usually occurs around small particles or molecules. By introducing specific nanoparticles into the optical fiber, the size and material properties of these particles can change the scattering characteristics of light. Through particle doping, the number and surface area of ​​scattering interfaces are increased, thereby enhancing the intensity of Rayleigh scattering. Especially in high concentrations, the interaction between particles can further enhance the scattering effect. The backscattered light signal can be significantly improved by doping the optical fiber with oxides such as boron and germanium.

[0048] Optionally, the optical fiber 4 is replaced by a grating with extremely low reflectivity to reflect the output laser beam back to the laser diode 1 .

[0049] In some exemplary embodiments, a double-stage optical isolator is used, which has a greater isolation degree, and its isolation degree is doubled relative to a single-stage optical isolator. The isolation degree of the double-stage optical isolator should be greater than 55 dB, and the double-stage optical isolator isolates structures such as laser diodes, collimating lenses, converging lenses, and optical fibers to prevent the reflected light beam from affecting the above structures.

[0050] When the laser diode 1 is placed under a suitable current and voltage, the laser diode emits light with a wavelength of 1550nm, which is coupled into the optical fiber 4 or other structures mentioned above after passing through the collimating lens 2 and the converging lens 3. The optical fiber 4 and other structures reflect a small amount of laser light generated by the laser diode 1 and return it to the converging lens 3 and the collimating lens 2, and finally feed back to the laser diode 1, thereby affecting the working state of the laser diode 1.

[0051] In some exemplary embodiments, the structure of the narrow linewidth laser device is simplified, and the device is easy to manufacture and package, thereby reducing the cost of the narrow linewidth laser device and having higher stability and reliability.

[0052] The laser obtained by the narrow linewidth laser of the above system has a linewidth of the order of hundreds of hertz, and the frequency noise of the narrow linewidth laser device in the frequency range of 3kHz to 100kHz is relatively small.

[0053] Figure 4 This is a power test data chart of the new narrow linewidth laser device. The output power of the new narrow linewidth laser device is 12.059mW. Figure 5 Spectrum diagram of the new narrow-linewidth laser device. The laser wavelength of the new narrow-linewidth laser device is around 1550nm. Figure 6 Phase noise test results of three replicates of the new narrow linewidth laser device. Frequency noise is less than 15 Hz / Hz in the frequency range of 3 kHz to 100 kHz, which is of particular concern. 1 / 2 . Figure 7 φ is the linewidth of the novel narrow linewidth laser device measured by using the phase noise method. The linewidth of the novel narrow linewidth laser device is specifically 542.2 Hz.

[0054] So far, the embodiments of the present disclosure have been described in detail with reference to the accompanying drawings.

[0055] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A novel narrow linewidth laser device, wherein: include: Laser diode (1); collimating lens (2); converging lens (3); optical fiber (4); double-stage optical isolator (5); the double-stage optical isolator (5) isolates structures such as the laser diode, collimating lens, converging lens, optical fiber or grating with high isolation to prevent the reflected light beam from affecting the aforementioned structures; Using the laser diode (1) to generate a laser light source; Under the action of the collimating lens (2), the light source output by the laser diode is converted into parallel light; Under the action of the converging lens (3), the parallel light formed by the laser diode through the collimating lens (2) converges to a focal point and is coupled into the optical fiber; The optical fiber (4) with a low reflectivity formed by special treatment reflects the output laser beam back to the laser diode; The double-stage optical isolator (5) isolates structures such as the laser diode (1), the collimating lens (2), the converging lens (3), and the optical fiber (4) with a high isolation degree of more than 55 dB, so as to prevent the reflected light beam from affecting the above structures.

2. A novel narrow linewidth laser device according to claim 1, wherein: The laser diode (1) operates under a specified current and voltage environment, and emits laser light with a wavelength of 1550 nm.

3. A novel narrow linewidth laser device according to claim 1, wherein: The collimating lens (2) converts the laser light emitted by the laser diode (1) into parallel light.

4. A novel narrow linewidth laser device according to claim 1, wherein: The converging lens (3) converges the parallel light after the collimating lens (2) to a focal point and couples it into the optical fiber.

5. A novel narrow linewidth laser device according to claims 1, 2 and 3, wherein: The collimating lens (2) and the converging lens (3) are used in combination to efficiently couple the laser light source generated by the laser diode (1) into the optical fiber.

6. A novel narrow linewidth laser device according to claim 1, wherein: The optical fiber (4) with a lower reflectivity formed by special processing reflects the output laser beam back to the laser diode (1).

7. The optical fiber (4) according to claim 6, wherein: The optical fiber uses polarization-maintaining optical fiber, and optical fiber with a small bending radius can be used optionally to reduce the impact of bending and vibration on the transmission characteristics of the optical fiber.

8. The optical fiber (4) according to claim 6, optionally, uses a Rayleigh scattering enhanced optical fiber, so that the output light is reflected a little by a longer section of the Rayleigh scattering enhanced optical fiber, and the output laser beam is reflected back to the laser diode (1).

9. The Rayleigh scattering enhanced optical fiber according to claim 8 can be prepared by ultraviolet light irradiation, arc discharge and the like.

10. The optical fiber (4) according to claim 6, optionally, an ultra-weak Bragg grating is introduced into the optical fiber to achieve a small amount of reflection of the input light and reflect the output laser beam back to the laser diode (1).

11. A novel narrow linewidth laser device according to claim 1, wherein: The double-stage optical isolator (5) has a greater degree of isolation. The degree of isolation of the double-stage optical isolator should be greater than 55 dB. The double-stage optical isolator (5) isolates structures such as the laser diode (1), the collimating lens (2), the converging lens (3), and the optical fiber (4) to prevent the reflected light beam from affecting the above structures.

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