A wide-band fast wavelength tuning light source device and method

Abstract

The application provides a wide-band fast wavelength tuning light source device and method, belongs to the field of laser technology and precise spectrum, and comprises a first laser source and a second laser source, the first laser source generates first coherent light, the first coherent light is coupled into a ring resonant cavity, optical parametric conversion is realized at a first nonlinear crystal, and idler light and signal light are output, the second laser source generates second coherent light, the second coherent light is coupled into the ring resonant cavity from another port, the first coherent light remaining after optical parametric conversion at the first nonlinear crystal is coaxially injected into a second nonlinear medium with the second coherent light, stimulated Raman intensity amplification and phase change of the first coherent light are realized, the intensity of the second coherent light injected into the second nonlinear medium can be fast and expressively adjusted, the three-wave phase matching condition in the resonant cavity is adjusted, fast and wide-band wavelength tuning of the signal light and the idler light is realized, and the technical blank of wide-band fast wavelength tuning is filled.

Description

Technical Field

[0001] This invention belongs to the fields of laser technology and precision spectroscopy technology, and specifically relates to a broadband fast wavelength tuning light source device and method. Background Technology

[0002] This invention relates to laser technology, particularly tunable laser technology applied in fields such as spectral analysis and atomic cooling. In these applications, the tunability of the laser is crucial. Taking spectral imaging as an example, the laser must simultaneously possess a large wavelength tuning bandwidth and a high tuning speed to meet the demands of high-resolution and real-time fingerprint spectral imaging.

[0003] Currently, various types of broadband tunable lasers are available on the market, mainly including Ti:sapphire lasers, temperature-tuned, and pump-tuned optical parametric oscillators (OPOs). Ti:sapphire lasers have a relatively fixed maximum tuning range of 700 nm to 930 nm. Wavelength tuning primarily relies on a rotatable birefringent filter or etalon built into the resonant cavity. The main problem with this type of mechanical tuning is its limited tuning speed, approximately 10 nm / min. Furthermore, because the gain curve of the gain medium is not uniformly or symmetrically distributed, mode hopping and non-uniform changes in the wavelength tuning step size are prone to occur during tuning. OPOs can simultaneously generate two coherent beams (signal light and idle light) through a nonlinear parametric process. The wavelength of the output beam and its tuning characteristics are mainly determined by the pump light wavelength and the parametric gain curve determined by the phase-matching condition, thus allowing for free selection or adjustment. The advantage of temperature-tuned OPOs is that the output signal light and idle light can be tuned simultaneously (with equal absolute values ​​of frequency changes but opposite signs), and the tuning range is relatively wide. Taking a single-resonance optical parametric oscillator (OPO) based on periodically polarized lithium niobate with a polarization period of 30.2 μm, pumped by a 1064 nm laser, as an example, when the crystal temperature changes from 120 °C to 190 °C, the tuning ranges of the signal light and idler light are 1604.2349 nm to 1653.3256 nm and 3159.5625 nm to 2985.0026 nm, respectively. The main problem with temperature-tuned OPOs is the limited tuning range achievable with a single polarization period. When used for spectral measurements, it is usually necessary to move the crystal and change the polarization period to extend the wavelength tuning range. More importantly, temperature tuning is also slow, typically only 6–120 nm / min. Pump-tuned OPOs are generally single-resonance, meaning the signal light wavelength remains constant, while the output idler light wavelength changes accordingly with the pump light wavelength. The main advantages of this type of light source are that the tuning system is simple and easy to operate, and the tuning speed is relatively fast (consistent with the pump light tuning speed). The main problem is that only the idle light is tunable, and the tuning range depends entirely on the tuning performance of the pump light, which is generally relatively narrow.

[0004] Existing tunable lasers either have a wide tuning bandwidth or a high tuning speed, but no light source that combines both of these characteristics has been reported or commercialized. Summary of the Invention

[0005] The purpose of this invention is to provide a broadband fast wavelength tuning light source device and method to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a broadband fast wavelength tuning light source device, comprising a first laser source and a second laser source, wherein the first laser source generates a first coherent light, the first coherent light is coupled into a ring resonant cavity, optical parametric conversion is realized at a first nonlinear crystal and idle light and signal light are output, the second laser source generates a second coherent light, the second coherent light is coupled into the ring resonant cavity from another port and coaxially injected into a second nonlinear medium with the first coherent light.

[0007] Preferably, the second laser source is a continuously tunable laser, and the difference between the operating frequency of the second coherent light and the operating frequency of the first coherent light is equal to the intrinsic Raman frequency shift corresponding to the strongest Raman mode of the second nonlinear medium.

[0008] Preferably, the annular resonant cavity includes a first cavity mirror, a first nonlinear crystal, a second cavity mirror, a third cavity mirror, a second nonlinear medium, and a fourth cavity mirror. The first cavity mirror is arranged to the right of the first laser source, the first nonlinear crystal is arranged to the right of the first cavity mirror, and the second cavity mirror is arranged to the right of the first nonlinear crystal. The first coherent light is coupled into the first nonlinear crystal through the first cavity mirror to achieve optical parametric conversion. Idle light is output through the second cavity mirror, and signal light is output through the fourth cavity mirror. The third cavity mirror is arranged to the right of the second laser source, the second nonlinear medium is arranged to the right of the third cavity mirror, and the fourth cavity mirror is arranged to the right of the second nonlinear medium. The second coherent light is coupled into the second nonlinear medium through the third cavity mirror and coaxially injected into the second nonlinear medium with the first coherent light circulating in the resonant cavity. The phase of the first coherent light after passing through the second nonlinear medium changes with the intensity of the injected second coherent light.

[0009] Preferably, the first nonlinear crystal is a nonlinear crystal, such as lithium triborate, periodically polarized lithium niobate, or periodically polarized potassium titanium phosphate with angle / temperature phase matching. The second nonlinear medium is a nonlinear medium with strong Raman activity, specifically methane or sulfur hexafluoride gas placed in a sealed gas pool, or organic liquids such as benzene, carbon disulfide, carbon tetrachloride, acetone, or dimethyl sulfoxide placed in a sealed liquid pool, or inorganic crystal materials such as diamond or yttrium vanadate.

[0010] A method for broadband fast wavelength tuning includes the following steps:

[0011] S1: First, build a ring resonant cavity optical parametric oscillator that includes a first cavity mirror, a second cavity mirror, a third cavity mirror, and a fourth cavity mirror. The first nonlinear crystal is placed between the first cavity mirror and the second cavity mirror, and the second nonlinear medium is placed between the third cavity mirror and the fourth cavity mirror.

[0012] S2: Simultaneously turn on the first laser source to generate the first coherent light and the second laser source to generate the second coherent light, which enter the resonant cavity from the first cavity mirror and the third cavity mirror respectively. The first coherent light generates idle light and signal light after passing through the first nonlinear crystal.

[0013] S3: By controlling the temperature of the first nonlinear crystal, coarse tuning of the wavelengths of the idle light and signal light is achieved. Within each coarse tuning range, the intensity of the second coherent light injected into the second nonlinear medium is changed, and the wavelengths of the idle light and signal light will change rapidly and continuously within a small range, thus achieving fine tuning.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. This invention adds a second nonlinear medium with Raman activity to the ring resonant cavity and utilizes the phase change caused by stimulated Raman scattering to achieve phase manipulation of a coherent beam in the three-wave interaction, thereby realizing fast and broadband wavelength tuning of the signal light and idle light.

[0016] 2. This invention proposes a stimulated Raman phase-shift modulated optical parametric oscillator containing two nonlinear media. Through a pump intensity-dependent stimulated Raman scattering process, it achieves rapid manipulation of the wavelengths of signal light and idle light, filling the technical gap of broadband rapid matching wavelength tuning. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the broadband fast wavelength tuning device of the present invention;

[0018] Figure 2 This is a schematic diagram of the ring resonator of the present invention;

[0019] Figure 3 The curves showing the change of the wavelengths of the signal light and idle light as a function of tuning time are shown in this invention.

[0020] In the figure: 1. First laser source; 2. Second laser source; 3. First coherent light; 4. Second coherent light; 5. Ring resonator; 501. First cavity mirror; 502. First nonlinear crystal; 503. Second cavity mirror; 504. Third cavity mirror; 505. Second nonlinear medium; 506. Fourth cavity mirror; 6. Idle light; 7. Signal light. Detailed Implementation

[0021] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0022] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figure 1-3 One embodiment of the present invention provides a broadband fast wavelength tuning light source device, comprising a first laser source 1 and a second laser source 2. The first laser source 1 generates a first coherent light 3, which is coupled into a ring resonant cavity 5 to achieve optical parametric conversion and output idle light 6 and signal light 7. The second laser source 2 generates a second coherent light 4, which is coupled into the ring resonant cavity 5 from another port.

[0026] Furthermore, the first laser source 1 adopts an all-solid-state continuous single-frequency laser with a center wavelength of 1064nm.

[0027] Furthermore, the second laser source 2 is a fully solid-state continuously tunable Ti:sapphire laser with a tuning range of 700nm to 930nm.

[0028] Furthermore, the first nonlinear crystal 502 is a periodically polarized lithium niobate crystal with a polarization period of 29.8 μm, and the second nonlinear medium 505 is a diamond crystal.

[0029] Furthermore, the ring resonant cavity 5 includes a first cavity mirror 501, a first nonlinear crystal 502, a second cavity mirror 503, a third cavity mirror 504, a second nonlinear medium 505, and a fourth cavity mirror 506. Specifically, the first cavity mirror 501 is the input cavity mirror, with a coating of HT@1064nm and HR@1.54~1.75μm (HT means high transmittance, HR means high reflectance); the second cavity mirror 503 is the output cavity mirror, with a coating of HT@2.7~3.4μm and HR@1064nm and 1.54~1.75μm; the third cavity mirror 504 is the input cavity mirror, with a coating of HT@932nm and HR@1064nm and 1.54~1.75μm; and the fourth cavity mirror 506 is the output cavity mirror, with a coating of T=2%@1.54~1.75μm and HR@1064nm (T is transmittance). Inside the resonant cavity, the first coherent light 3 can be reflected to the second nonlinear medium 505 through the second cavity mirror 503 and the third cavity mirror 504, and the second coherent light 4 can be transmitted to the second nonlinear medium 505 through the third cavity mirror 504.

[0030] Simultaneously, the first laser source 1 and the second laser source 2 are activated to generate 1064nm and 932nm single-frequency lasers, respectively. When the temperature of the periodically polarized lithium niobate is controlled at 120℃, the power of the 932nm single-frequency laser is increased from 0W to 5W, and the tuning ranges of the signal light 7 and the idle light 6 are 1558.8687~1558.9023nm and 3351.6694~3351.5142nm, respectively. Based on this, by rapidly step-changing the temperature of the periodically polarized lithium niobate, wavelength scanning of the signal light 7 and the idle light 6 can be achieved within 1 minute in the ranges of 1558.8687~1584.8878nm and 3237.397~3351.6694nm.

[0031] The above descriptions are merely embodiments of the present invention, and the specific structures and characteristics mentioned in the solutions are not described in detail here. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A broad spectrum fast wavelength tunable light source device comprising a first laser source (1) and a second laser source (2), characterized in that, The first laser source (1) generates a first coherent light (3), which is coupled into a ring resonant cavity (5). Optical parametric conversion is achieved at the first nonlinear crystal (502), and idle light (6) and signal light (7) are output. The second laser source (2) generates a second coherent light (4), which is coupled into the ring resonant cavity (5) from another port and coaxially injected with the first coherent light (3) into a second nonlinear medium (505). The first nonlinear crystal (502) is a nonlinear crystal, and the second nonlinear medium (505) is a nonlinear medium with strong Raman activity. The second laser source (2) adopts a continuously tunable laser. The difference between the operating frequency of the second coherent light (4) and the operating frequency of the first coherent light (3) is equal to the intrinsic Raman frequency shift corresponding to the strongest Raman mode of the second nonlinear medium (505). By controlling the temperature of the first nonlinear crystal (502), the wavelength of the idle light (6) and the signal light (7) is coarsely tuned. In each coarse tuning interval, the intensity of the second coherent light (4) injected into the second nonlinear medium (505) is changed, and the wavelength of the idle light (6) and the signal light (7) will change rapidly and continuously within a small range, thus achieving fine tuning.

2. The broadband fast wavelength tuning light source device according to claim 1, characterized in that, The annular resonant cavity (5) includes a first cavity mirror (501), a first nonlinear crystal (502), a second cavity mirror (503), a third cavity mirror (504), a second nonlinear medium (505), and a fourth cavity mirror (506). The first cavity mirror (501) is arranged to the right of the first laser source (1), the first nonlinear crystal (502) is arranged to the right of the first cavity mirror (501), and the second cavity mirror (503) is arranged to the right of the first nonlinear crystal (502). The first coherent light (3) is coupled into the first nonlinear crystal (502) through the first cavity mirror (501) to achieve optical parametric conversion, and then transmitted through the second cavity mirror (503). The idle light (6) is output and the signal light (7) is output through the fourth cavity mirror (506). The third cavity mirror (504) is arranged on the right side of the second laser source (2). The second nonlinear medium (505) is arranged on the right side of the third cavity mirror (504). The fourth cavity mirror (506) is arranged on the right side of the second nonlinear medium (505). The second coherent light (4) is coupled through the third cavity mirror (504) and coaxially injected into the second nonlinear medium (505) with the first coherent light (3) circulating in the resonant cavity. The phase of the first coherent light (3) after passing through the second nonlinear medium (505) changes with the intensity of the injected second coherent light (4).

3. The broadband fast wavelength tuning light source device according to claim 2, characterized in that, The first nonlinear crystal (502) is lithium triborate, periodically polarized lithium niobate, or periodically polarized potassium titanium phosphate with angle / temperature phase matching. The second nonlinear medium (505) is a nonlinear medium with strong Raman activity, specifically diamond or yttrium vanadate, or methane or sulfur hexafluoride gas placed in a sealed gas pool, or benzene, carbon disulfide, carbon tetrachloride, acetone, or dimethyl sulfoxide placed in a sealed liquid pool.

4. A method for broadband fast wavelength tuning, characterized in that, The light source device according to claim 3 includes the following method: S1: First, a ring resonant cavity (5) optical parametric oscillator is constructed, which includes a first cavity mirror (501), a second cavity mirror (503), a third cavity mirror (504) and a fourth cavity mirror (506), a first nonlinear crystal (502) is disposed between the first cavity mirror (501) and the second cavity mirror (503), and a second nonlinear medium (505) is disposed between the third cavity mirror (504) and the fourth cavity mirror (506); S2: Simultaneously turn on the first laser source (1) to generate the first coherent light (3) and the second laser source (2) to generate the second coherent light (4), which enter the resonant cavity from the first cavity mirror (501) and the third cavity mirror (504) respectively. The first coherent light (3) generates idle light (6) and signal light (7) after passing through the first nonlinear crystal (502). S3: By controlling the temperature of the first nonlinear crystal (502), the wavelengths of the idle light (6) and the signal light (7) are coarsely tuned. Within each coarse tuning interval, the intensity of the second coherent light (4) injected into the second nonlinear medium (505) is changed, and the wavelengths of the idle light (6) and the signal light (7) will change rapidly and continuously within a small range, thus achieving fine tuning.

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