An orthogonally polarized dual-wavelength hollow planar laser with balanced output power

Abstract

This invention relates to the field of laser technology, and in particular to an orthogonally polarized dual-wavelength hollow planar laser with balanced output power. The pump beam is collimated by a first plano-convex mirror, converted into a conical beam by a negative conical mirror, focused into a ring beam by a second plano-convex mirror, and coupled into the laser gain medium by a plane mirror. The laser resonator is composed of cylindrical surfaces of a plane mirror and two negative conical mirrors; the laser beam is output through the cylindrical surfaces, forming a hollow planar laser beam. By optimizing the transmittance of the cylindrical surfaces of the two negative conical mirrors to the target dual wavelengths, the oscillation thresholds of the two wavelengths are made equal. By moving the second plano-convex mirror horizontally, the slope efficiency of the input-output power of the dual-wavelength laser intersects, thus obtaining the condition for equal output power of the orthogonally polarized dual-wavelength hollow planar laser. This invention's orthogonally polarized dual-wavelength hollow planar laser with equal output power can meet the application requirements of high-precision gas concentration inversion, low-damage homogeneous material processing, and stable quantum state manipulation.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to an orthogonally polarized dual-wavelength hollow planar laser with balanced output power. Technical Background

[0002] Dual-wavelength laser technology has significant application value in differential absorption detection, nonlinear optical frequency conversion, and dual-wavelength interferometry. Orthogonally polarized dual-wavelength lasers, with their independent polarization states and low crosstalk characteristics, exhibit unique advantages in polarization-sensitive detection and dual-frequency interferometry. However, existing hollow laser technologies (such as patents CN2023107605979 and CN202310760389) primarily produce beams with a cylindrical intensity distribution. While their energy is concentrated in the ring zone and suitable for particle capture, the lack of a uniformly distributed planar wavefront often renders them inadequate for industrial applications such as machining the inner surfaces of cylindrical materials, high-precision planar scanning, and planar polishing, severely limiting their application in precision manufacturing. Meanwhile, existing planar laser sources (such as patent CN2023107645980) remain limited to single-wavelength output modes, failing to achieve high-precision differential absorption detection of specific gases or meet the directional processing requirements of polarization-sensitive materials, severely hindering the development of multidimensional optical sensing and complex micro / nano manufacturing. Developing a planar dual-wavelength hollow laser beam based on this foundation can combine the characteristics of uniform energy distribution and the absence of a central intensity peak in planar beams. This allows for high-precision gas inversion in differential absorption lidar by utilizing the absorption difference between the two wavelengths, and improving detection stability by reducing atmospheric turbulence interference through a ring structure. Furthermore, in the biomedical field, it reduces photobleaching effects through uniform illumination modes and integrates marking and imaging through dual-wavelength orthogonal polarization. In precision machining, it enables uniform cutting of brittle materials through dual-wavelength synergistic heating, avoiding the propagation of microcracks caused by strong central energy. Moreover, this beam, combining power balance and a hollow planar distribution, provides an ideal light source for laser interferometry, quantum optics experiments, and nonlinear frequency conversion, and has broad application prospects in aerospace, environmental monitoring, and high-end manufacturing. Summary of the Invention

[0003] To address the aforementioned technical bottlenecks, this invention proposes a power-balanced output orthogonally polarized dual-wavelength hollow planar laser. This laser organically integrates the physical characteristics of dual-wavelength orthogonal polarization with the energy distribution advantages of a hollow planar beam. By optimizing the output coupling transmittance of the dual wavelengths and controlling the overlap efficiency of the pump beam and the laser beams in the two polarization directions, power-balanced output of the orthogonally polarized dual-wavelength hollow planar laser is achieved. This laser can meet the application requirements of high-precision gas concentration inversion, low-damage homogeneous material processing, and stable quantum state manipulation, providing an ideal light source for aerospace, environmental monitoring, and high-end manufacturing.

[0004] This invention is achieved through the following technical solution:

[0005] A hollow planar laser with balanced output power and orthogonal polarization dual wavelengths includes a pump source, a first plano-convex mirror, a negative conical mirror, a second plano-convex mirror, a plane mirror, a laser gain medium, and two negative conical mirrors arranged sequentially.

[0006] The pump source is a semiconductor laser array coupled with an optical fiber.

[0007] After being collimated by the first plano-convex mirror, the pump beam is converted into a conical beam by the negative conical mirror, focused by the second plano-convex mirror to form a ring beam, and then coupled into the laser gain medium by the plane mirror;

[0008] The laser resonant cavity is composed of a cylindrical surface of a plane mirror and a double negative conical mirror. The laser beam is output through the cylindrical surface to form a hollow planar laser beam.

[0009] By optimizing the transmittance of the cylindrical surface of the double negative conical mirror to the target at both wavelengths, the oscillation thresholds of the two wavelengths are made equal.

[0010] Moving the second plano-convex mirror horizontally can change the spatial position of the pump focusing ring in the laser gain medium, thereby controlling the overlap efficiency of the orthogonally polarized laser beam and the pump beam, so that the slope efficiency of the input-output power of the dual-wavelength laser intersects, and the output power of the orthogonally polarized dual-wavelength hollow plane laser is equal.

[0011] The left vertex angle β and the right vertex angle γ of the double negative conical mirror must satisfy the following equation: , where n is the refractive index of the double negative conical mirror.

[0012] Based on the condition of equal thresholds for orthogonal polarization dual wavelengths, the relationship curve between the transmittance of the cylindrical surface of the double negative conical mirror and the orthogonal polarization dual wavelengths is obtained; the film system of the cylindrical surface of the double negative conical mirror and the target orthogonal polarization dual wavelengths is prepared according to the corresponding value in the curve.

[0013] As the pump power increases, the second plano-convex mirror moves synchronously to control the position of the pump ring in the laser gain medium (6), so as to achieve equal power output of the orthogonally polarized dual-wavelength hollow plane laser under different pump powers.

[0014] The orthogonally polarized dual-wavelength hollow planar laser with equal output power of the present invention can meet the application requirements of high-precision gas concentration inversion, low-damage homogeneous material processing and stable quantum state manipulation, and provide high-performance optical solutions for aerospace, environmental monitoring and high-end manufacturing and other fields. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the laser structure of the present invention;

[0016] Figure 2 This is a schematic diagram of the structure and related parameters of a double negative conical mirror;

[0017] Figure 3 The graph shows the relationship between the transmittance of the cylindrical surface of the double negative conical mirror at 1047nm and 1053nm when the two wavelength thresholds are equal for orthogonal polarization.

[0018] Figure 4 A graph showing the relationship between the overlap integral of the pump beam and the laser beam and the distance the second plano-convex mirror moves.

[0019] Figure 5 The graph shows the relationship between pump power, total output power of the equalized dual-wavelength hollow planar laser, and the distance the second plano-convex mirror moves. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0021] An orthogonally polarized dual-wavelength hollow planar laser with balanced output power, such as Figure 1 As shown, the system includes, from left to right, a pump source 1, a first plano-convex mirror 2, a negative conical mirror 3, a second plano-convex mirror 4, a plane mirror 5, a laser gain medium 6, and a double negative conical mirror 7.

[0022] Assume that the first plano-convex mirror 2, the negative conical mirror 3, the second plano-convex mirror 4, the plane mirror 5, and the double negative conical mirror 7 are all made of the same glass material with a refractive index of n. The left and right cone apex angles of the double negative conical mirror 7 are β and γ, respectively. The incident angle of the laser beam on the left cone surface is θ, the refraction angle is ρ, and the reflection angle of the laser beam on the right cone surface is φ. Figure 2 As shown. From the geometry of the double negative conical mirror 7 and the law of refraction, we can obtain:

[0023] (1),

[0024] (2),

[0025] (3),

[0026] (4);

[0027] Solving equations (1)-(4) simultaneously, we get:

[0028] (5);

[0029] When the cone apex angles β and γ on both sides of the double negative conical mirror 7 satisfy equation (5), the laser beam is perpendicular to the conical surface of the double negative conical mirror 7, forming a set of flat-flat cavities in the cavity, and forming a planar distribution around the horizontal axis at an angle of 2π.

[0030] Assume the laser gain medium 6 is an a-axis cut Nd:LiYF4 crystal. The strongest emission lines of the Nd:LiYF4 crystal in the π and σ polarization directions correspond to transition wavelengths of 1047 nm and 1053 nm, respectively. The emission cross-sections in the π (S-wave) and σ (P-wave) polarization directions are 17.7 × 10⁻⁶ and 10⁻⁶, respectively. -20 cm 2 and 11.5×10 -20 cm 2 The emission cross-sections of the two polarization direction transition wavelengths are significantly different, therefore there must be a strong gain competition effect between the 1047nm (S-wave) and 1053nm (P-wave) transition wavelengths.

[0031] First, by optimizing the transmittance of the cylindrical surface of the double negative conical mirror 7 at wavelengths of 1047nm and 1053nm, the intracavity loss of the 1047nm laser is made higher than that of the 1053nm laser, thus making the oscillation thresholds of the orthogonally polarized dual-wavelength hollow plane lasers equal. For a four-level laser system, the threshold pump power P of the laser is... th,i for:

[0032] (6),

[0033] In equation (6), T oc,i η i σ i τ i、 L 0i hν p , l, and are, respectively, the transmittance, quantum efficiency, stimulated emission cross section, upper level fluorescence lifetime, cavity passive loss, pump photon energy, length of the gain medium, and overlap integral of the pump light and laser beam at the corresponding transition wavelength. th,1053nm =P th,1047nm When, substitute the relevant parameters and τ above. 1047nm ≈τ 1053nm V EFF,1047nm ≈V EFF,1053nm and L 0i =0.01, the relationship curve between the transmittance at 1047 nm and 1053 nm can be calculated, as shown below. Figure 3 As shown. Therefore, when the transmittance of the cylindrical surface of the double negative conical mirror 7 at 1047 nm and 1053 nm satisfies Figure 3 When the corresponding relationship is established, the threshold values ​​of orthogonally polarized dual-wavelength hollow plane lasers can be made equal.

[0034] For the output-input power slew rate η of a four-level laser s,i It can be represented as:

[0035] (7);

[0036] When the threshold P th,1047nm = P th,1053nm ,Depend on Figure 3 It can be seen that T oc,1047nm > T oc,1053nm From equation (7), we can obtain η s,1047nm < η s,1053nm Therefore, the output-input slope efficiencies at 1047nm and 1053nm only intersect at the threshold, and as the pump power increases, the two wavelengths cannot achieve the same output power. Furthermore, as the pump power increases, the thermal lensing of the laser gain medium in the orthogonal polarization direction also produces significant differences, leading to a change in the mode-matching efficiency between the pump beam and the orthogonally polarized laser beam, i.e., V0. EFF,1047nm ≠ V EFF,1053nm At this point, it can be seen from equation (6) that the threshold values ​​of the two orthogonally polarized wavelengths, 1047 nm and 1053 nm, will no longer be equal.

[0037] The overlap integral of the pump beam and the laser beam is:

[0038] (8);

[0039] r in equation (8) p (r j ,z) and s i (r j ,z) represent the normalized pump intensity distribution and normalized laser cavity mode intensity distribution corresponding to the transition wavelength, respectively, and r j z and r represent the radial and lateral coordinates, respectively; j = a and b represent the inner and outer radii of the halo, respectively; r = a and b = b. p (r j ,z) and s i (r j (z) can be represented as:

[0040] (9),

[0041] (10);

[0042] In equation (9), ω pj (z) is the ring size of the pump light in the laser gain medium 6, α abs It is the absorption coefficient of laser gain medium 6.

[0043] Let the radius of the pump beam output from pump source 1 via fiber coupling be ω0, the apex angle of negative conical mirror 3 be α, and the focal length of the second plano-convex mirror 4 be f. Then, according to the law of refraction and the geometry of negative conical mirror 3, the inner and outer radii of the pump ring are respectively:

[0044] (11),

[0045] (12);

[0046] Therefore, the size ω of the pump light ring in the laser gain medium 6 pj (z) can be represented as:

[0047] (13)

[0048] Equation (13) z0 is the beam waist position of the pump beam, and z = 0 is located at the incident surface of the laser gain medium 6. R The Rayleigh length of the pump beam can be expressed as:

[0049] (14)

[0050] n in equation (14) c λ is the refractive index of laser gain medium 6. p It is the pump wavelength, M 2 This is the quality factor of the pump laser. When the focal length f of the thermal lens of the laser gain medium 6... i When (z) changes, the radius ω of the laser beam's ring ij It will also change, and its value can be calculated using the ABCD matrix, f i (z) can be represented as:

[0051] (15)

[0052] In equation (15), ξ i This represents the heat load coefficient, (dn / dT). i It is the thermo-optic coefficient, 𝐾 i It refers to thermal conductivity.

[0053] From equations (9) and (10), it can be seen that when the position of the pump beam waist moves (the distance the pump beam waist moves is equal to the distance the second plano-convex mirror moves), r p (r j ,z) and s i (r j Both z) will change. Therefore, the overlap integral V is controlled by moving the pump spot position. EFF,i The value of .

[0054] The relevant parameters and α=120 o n=1.5, α abs = 1.25 cm -1 M 2 =40, l=20mm, ξ 1047nm =0.23, ξ 1053nm =0.24, (dn / dT) 1047nm = −2.0 × 10 −6 K −1 , (dn / dT) 1053nm = −4.3 × 10 −6 K −1 K 1047nm = 7.2 W / m·K, K 1053nm = 5.8 W / m·K, L 0i Substituting 0.01 into equations (8)-(15), the overlapping integral V under different pump powers can be calculated. EFF,i The relationship between the distance z that the pump spot moves and the following is as follows: Figure 4 As shown. From Figure 4 It can be seen that when the pump power is near the threshold, due to the weak thermal lensing effect of the laser gain medium, the overlap integral V is... EFF,1047nm With V EFF,1053nm Basically the same, but as the pump power increases, V EFF,1047nm With V EFF,1053nm The difference gradually increases. When V EFF,1053nm <V EFF,1047nm At that time, according to equation (6), P can be obtained. th,1053nm >P th,1047nm That is, when the pump power exceeds the laser threshold, the slope efficiency at 1047nm and 1053nm must intersect at a certain point. Therefore, as the pump power increases, the output power at wavelengths of 1047nm and 1053nm can be made equal by moving the position of the pump ring.

[0055] The output power of a laser can be expressed as:

[0056] (16)

[0057] When P out,1047nm = P out,1053nm When, by solving equations (6)-(16) simultaneously, the pump power (P) can be obtained. in The total power (P) of the balanced output orthogonally polarized dual-wavelength hollow plane laser. tot,out The relationship between (z) and the distance (z) the pump aura moves is as follows: Figure 5 As shown. By Figure 5It can be seen that as the pump power continues to increase, simply moving the pump ring can enable the 1047 nm and 1053 nm dual-wavelength lasers to achieve equal power output under different pump powers.

[0058] Pump source 1 is an 808nm fiber-coupled semiconductor laser array (fiber core diameter 400μm, numerical aperture 0.22); the first plano-convex mirror 2, the negative conical mirror 3, and the second plano-convex mirror 4 are coated with antireflection films on the 808nm wavelength; the plane mirror 5 is coated with an antireflection film on the 808nm wavelength and with high-reflection films on the 1047nm and 1053nm wavelengths; the laser gain medium 6 is coated with antireflection films on the 808nm, 1047nm, and 1053nm wavelengths; the left cone of the double negative conical mirror 7 is coated with an antireflection film on the 1047nm and 1053nm wavelengths, and the transmittance of the right cone on the 1047nm and 1053nm wavelengths meets the following requirements. Figure 3 Curve preparation; both pump source 1 and laser gain medium 5 are cooled by water, and the operating temperature is stably controlled at 15±0.1℃. o C.

Claims

1. A hollow planar laser with orthogonal polarization and balanced output power, characterized in that, It includes a pump source (1), a first plano-convex mirror (2), a negative conical mirror (3), a second plano-convex mirror (4), a plane mirror (5), a laser gain medium (6), and a double negative conical mirror (7) arranged in sequence. The pump source (1) is a semiconductor laser array coupled with fiber optic output; The pump beam from the pump source (1) is collimated by the first plano-convex mirror (2), converted into a conical beam by the negative conical mirror (3), focused by the second plano-convex mirror (4) to form a ring beam, and then coupled into the laser gain medium (6) by the plane mirror (5); The laser resonant cavity is composed of a plane mirror (5) and a double negative conical mirror (7) cylindrical surface. The laser beam is output through the cylindrical surface to form a hollow plane laser beam. By optimizing the transmittance of the cylindrical surface of the double negative conical mirror (7) to the target dual wavelengths, the oscillation thresholds of the dual wavelengths are made equal; Moving the second plano-convex mirror (4) horizontally can change the spatial position of the pump focusing ring in the laser gain medium (6), thereby controlling the overlap efficiency of the orthogonally polarized laser beam and the pump beam, so that the slope efficiency of the input-output power of the dual-wavelength laser intersects, and the output power of the orthogonally polarized dual-wavelength hollow plane laser is equal.

2. The orthogonally polarized dual-wavelength hollow planar laser with balanced output power according to claim 1, characterized in that, The left apex angle β and the right apex angle γ of the double negative conical mirror (7) must satisfy the equation , where n is the refractive index of the double negative conical mirror (7).

3. The orthogonally polarized dual-wavelength hollow planar laser with balanced output power according to claim 1, characterized in that, Based on the condition of equal thresholds for orthogonal polarization dual wavelengths, the relationship curve between the transmittance of the cylindrical surface of the double negative conical mirror (7) and the orthogonal polarization dual wavelengths is obtained; the film system of the cylindrical surface of the double negative conical mirror (7) and the target orthogonal polarization dual wavelengths is prepared according to the corresponding value in the curve.

4. The orthogonally polarized dual-wavelength hollow planar laser with balanced output power according to claim 3, characterized in that, As the pump power increases, the second plano-convex mirror moves synchronously to control the position of the pump ring in the laser gain medium (6), so as to achieve equal power output of the orthogonally polarized dual-wavelength hollow plane laser under different pump powers.

Images