Small-divergence-angle laser based on beam shaping technology

Abstract

The utility model belongs to the field of laser application, and relates to beam shaping of a laser, in particular to a small-divergence-angle laser based on a beam shaping technology. The problems that in the prior art for laser diode collimation, astigmatism of the diode cannot be calibrated through single-lens collimation, and cost is increased due to the fact that fast axis collimation and slow axis collimation need to customize a fast axis collimating lens with a proper focal length are solved. The utility model discloses a small-divergence-angle laser based on a beam shaping technology. A first collimating lens, a fast-axis beam shrinking device and a beam expander are sequentially arranged on an emergent light path of a first laser diode; the light emitting point of the first laser diode is located at the focal point of the first collimating lens, the fast axis beam shrinking device comprises a first cylindrical lens and a second cylindrical lens, and the focal points of the first cylindrical lens and the second cylindrical lens coincide. According to the utility model, the divergence angle of the laser diode is reduced to 0.1 mrad, so that the diameter of a light spot at 500m is less than 100mm, and the actual light spot observed in an experiment is 80mm.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of laser application, relates to laser's beam shaping, concretely is a small divergence angle laser based on beam shaping technology. BACKGROUND

[0002] In the field of laser research and application, because of the actual application demand, it is required that the laser emitted by the laser diode is less than a certain value (100mm) at a long distance (500m). Since the laser diode has a large emission angle, the beam needs to be collimated to reduce the beam divergence angle.

[0003] The commonly used diode collimation methods include single lens collimation and fast axis collimation + slow axis collimation. However, the single lens collimation cannot correct the astigmatism of the diode, and the residual divergence angle after collimation is large, which cannot meet the use requirement. The fast axis collimation + slow axis collimation method requires a fast axis collimation mirror with a very small focal length. Due to the isolation of the protective glass of the diode, the light emitting point cannot be placed at the focal point of the fast axis collimation mirror. If the protective glass of the diode is removed, the reliability and service life of the diode will be reduced. Moreover, the cost of customizing a fast axis collimation mirror with a suitable focal length is very high. Therefore, it is necessary to develop a small divergence angle laser that can be used for diode collimation and meets the above requirements and has a low cost. UTILITY MODEL CONTENTS

[0004] The utility model discloses to solve the problem that the single lens collimation cannot correct the astigmatism of the diode in the current technology for diode collimation, and the fast axis collimation + slow axis collimation requires customizing a fast axis collimation mirror with a suitable focal length, which increases the cost. A small divergence angle laser based on beam shaping technology is provided.

[0005] The utility model is adopted as follows technical scheme realization: a small divergence angle laser based on beam shaping technology, first laser diode is equipped with first collimating lens, fast axis beam reducer and beam expander in proper order on the outgoing light path of first laser diode, the light emitting point of first laser diode is located at the focal point of first collimating lens, the fast axis beam reducer includes first cylindrical lens and second cylindrical lens, and the focal points of first cylindrical lens and second cylindrical lens coincide.

[0006] The utility model adopts the scheme of single lens collimation + fast axis beam reduction, which can complete the collimation of the laser diode with existing low-cost lenses.

[0007] Further, the second laser diode is sequentially provided with a second collimating lens, a 1 / 2 wave plate and a polarization beam splitter on an outgoing light path of the second laser diode; a light emitting point of the second laser diode is located at a focal point of the second collimating lens, and an angle between a fast axis direction of the 1 / 2 wave plate and a fast axis direction of the second laser diode is 45°; the polarization beam splitter is located between the first collimating lens and the fast axis beam shrinking device, and a reflection light path of the polarization beam splitter is coincident with the outgoing light path of the first collimating lens.

[0008] Further, in the fast axis beam shrinking device, one side of the first cylindrical lens with a larger curvature is directed to an outgoing direction of the first collimating lens, and one side of the second cylindrical lens with a smaller curvature is directed to the outgoing direction of the first cylindrical lens.

[0009] Further, the first and second collimating lenses are aspherical lenses with a focal length of 8mm.

[0010] The first cylindrical lens in the fast axis beam shrinking device is a plano-convex cylindrical lens with a focal length of 25mm, the second cylindrical lens is a plano-convex cylindrical lens with a focal length of 7.7mm, and the beam expander is 20 times.

[0011] Further, the first and second collimating lenses are aspherical lenses with a focal length of 8mm.

[0012] The first cylindrical lens in the fast axis beam shrinking device is a plano-convex cylindrical lens with a focal length of 25mm, the second cylindrical lens is a plano-convex cylindrical lens with a focal length of 7.7mm, and the beam expander is 20 times.

[0013] Further, the outgoing end of each laser diode is covered with a protective glass sheet.

[0014] Further, each laser diode is installed in a clamp with a central opening at the front end, the clamp is attached to a semiconductor refrigerator at the tail end, and the semiconductor refrigerator is connected with a heat sink; a sleeve is installed at the front end of the clamp, and a collimating lens corresponding to the laser diode is installed in the sleeve, and the sleeve is coaxially arranged with the clamp.

[0015] Further, a thermistor for temperature measurement is installed on the clamp.

[0016] The utility model adopts a set of low-cost optical devices, reduces the divergence angle of the laser diode to 0.1mrad, makes the light spot diameter less than 100mm at 500m, and the actual light spot is 80mm in experimental observation, which is very close to the theoretical value. Each lens is a conventional product that can be purchased on the market, and the cost is low. DRAWINGS

[0017] Figure 1 The structure schematic view of the first embodiment of the utility model.

[0018] Figure 2The second embodiment of the utility model structural schematic diagram.

[0019] Figure 3 The third embodiment of the utility model structural schematic diagram.

[0020] Figure 4 The mounting diagram of laser diode.

[0021] 1-first collimating lens, 2-fast axis beam reducer, 21-first cylindrical lens, 22-second cylindrical lens, 3-beam expander, 4-second collimating lens, 5-1 / 2 wave plate, 6-polarization beam splitter, 7-first / second laser diode, 8-clamp, 9-semiconductor refrigerator, 10-radiator, 11-sleeve, 12-thermistor. DETAILED DESCRIPTION

[0022] The utility model collimation object: day NDB7675 laser diode. Laser diode light emitting area presents strip shape, horizontal direction 15um, vertical direction 1um, horizontal direction light beam divergence angle 7°, vertical direction light beam divergence angle 22°, equal half angle. Because vertical direction light beam diverges fast, it is called vertical direction as fast axis, horizontal direction as slow axis. Diode inner package glass sheet, light emitting point distance diode outer surface 1mm. At present, the focal length of the fast axis collimation mirror is too small, and the light emitting point cannot be placed at the focal point of the fast axis collimation mirror. Special fast axis collimation mirror is needed, which increases the cost.

[0023] In order to make the laser emitted by the laser diode be less than a certain value (about 100mm) at a long distance (about 500m), and not produce astigmatism and not increase additional customization cost, the utility model provides the following three embodiments.

[0024] Embodiment 1 as shown in Figure 1 A small divergence angle laser based on beam shaping technology, comprising a first laser diode; a first collimating lens 1, a fast axis beam reducer 2 and a beam expander 3 are sequentially arranged on the outgoing light path of the first laser diode; the light emitting point of the first laser diode is located at the focal point of the first collimating lens 1, the fast axis beam reducer 2 comprises a first cylindrical lens 21 and a second cylindrical lens 22, and the focal points of the first cylindrical lens 21 and the second cylindrical lens 22 coincide; the first and second collimating lenses adopt aspherical lenses, and the focal length is 8mm;

[0025] The first cylindrical lens 21 in the fast axis beam reducer 2 is a plano-convex cylindrical lens with a focal length of 25mm, and the second cylindrical lens 22 is a plano-convex cylindrical lens with a focal length of 7.7mm; the beam expander 3 is a 20 times beam expander, the maximum input spot is 2.5mm, and the maximum output spot is 50mm.

[0026] Embodiment 2 as shown in Figure 2As shown, the first and second collimating lenses are aspherical lenses with a focal length of 8mm; the first cylindrical lens 21 in the fast-axis beam shrinking device 2 is a plano-convex cylindrical lens with a focal length of 25mm. Unlike embodiment 1, the second cylindrical lens 22 in embodiment 2 is a plano-concave cylindrical lens with a focal length of -6.4mm; the beam expander 3 is a 20x beam expander with a maximum input spot size of 2.5mm and a maximum output spot size of 50mm.

[0027] As a preferred embodiment, in the fast-axis beam-shrinking device of embodiments 1 and 2, the side of the first cylindrical lens with a larger curvature faces the exit direction of the first collimating lens, and the side of the second cylindrical lens with a smaller curvature faces the exit direction of the first cylindrical lens.

[0028] The spot size after collimation by a single lens is 6.144mm (fast axis) × 1.952mm (slow axis), corresponding to a divergence angle of 0.94mrad × 0.06mrad. The fast axis spot size after collimation by a single lens is larger than the input aperture of the beam expander, so it is necessary to reduce the fast axis spot size. On the other hand, a single lens cannot eliminate the astigmatism of the laser diode. Using fast axis beam reduction can also reduce or eliminate the astigmatism of the laser diode.

[0029] Fast-axis beam shrinkage: The shrinkage ratio is 6.4 / 25 = 3.9 times. After beam shrinkage, the fast-axis size becomes 1.58mm, which can pass through a beam expander. The divergence angle of the fast-axis after beam shrinkage is 0.24mrad.

[0030] Beam expander: 20x beam expansion, after beam expander the maximum beam diameter to 39mm, the maximum divergence half angle to 0.05mrad, after beam propagation for 500m, the maximum beam diameter is 39mm + 2 × 0.05 × 500mm = 89mm, which meets the target of less than 100mm.

[0031] Example 3 Figure 3 As shown, it also includes a second laser diode. A second collimating lens 4, a half-wave plate 5, and a polarizing beam splitter 6 are sequentially arranged on the output optical path of the second laser diode. The emission point of the second laser diode is located at the focal point of the second collimating lens 4. The fast axis direction of the half-wave plate 5 and the fast axis direction of the second laser diode form an angle of 45°. The polarizing beam splitter 6 is located between the first collimating lens 1 and the fast-axis beam shortening device 2, and the reflected optical path of the polarizing beam splitter 6 coincides with the output optical path of the first collimating lens 1. In embodiment 3, the fast-axis beam shortening device 2 can adopt the structure of embodiment 1 or the structure of embodiment 2.

[0032] In order to further improve the laser emission power without changing the spot size in Example 3, polarization beam combining is used to combine two laser diodes. The laser diodes are P-polarized light, the angle between the fast axis direction of the 1 / 2 wave plate and the fast axis direction of the second laser diode is 45°, and the light becomes S-polarized light after passing through the wave plate. The polarization beam splitter can reflect S-polarized light and transmit P-polarized light. The beams emitted by the two laser diodes overlap after passing through the polarization beam splitter, and the power is doubled. The spot diameter after the beam propagates 500 meters is the same as that of Examples 1 and 2.

[0033] The utility model further provides the mounting structure of laser diode. As Figure 4 The first / second laser diode 7 is installed in the jig 8 with a central opening at the front end, the jig 8 is attached to the semiconductor refrigerator 9 at the end, the semiconductor refrigerator 9 is connected with the cooling fin 10; the single collimating lens is installed in the sleeve 11 and located at the front end of the jig, the sleeve 11 is coaxially arranged with the jig 8; the thermistor 12 for temperature measurement is installed on the jig 8. The structure is convenient for heat dissipation of the laser diode, and the sleeve and the jig are tightly placed, generally without connection.

Claims

1. A small divergence angle laser based on beam shaping technology, comprising a first laser diode; characterized in that, The first laser diode is sequentially provided with a first collimating lens (1), a fast axis beam-reducing device (2) and a beam expander (3) on an outgoing light path of the first laser diode; a light emitting point of the first laser diode is located at a focal point of the first collimating lens (1), the fast axis beam-reducing device (2) comprises a first cylindrical lens (21) and a second cylindrical lens (22), and focal points of the first cylindrical lens (21) and the second cylindrical lens (22) coincide.

2. A small divergence angle laser based on beam shaping technique as claimed in claim 1, wherein, The second laser diode is sequentially provided with a second collimating lens (4), a 1 / 2 wave plate (5) and a polarization beam splitter (6) on an outgoing light path of the second laser diode; a light emitting point of the second laser diode is located at a focal point of the second collimating lens (4), an angle between a fast axis direction of the 1 / 2 wave plate (5) and a fast axis direction of the second laser diode is 45°; the polarization beam splitter (6) is located between the first collimating lens (1) and the fast axis beam-reducing device (2), and a reflection light path of the polarization beam splitter (6) coincides with the outgoing light path of the first collimating lens (1).

3. A small divergence angle laser based on beam shaping technique as claimed in claim 2, wherein, In the fast axis beam-reducing device (2), a larger curvature side of the first cylindrical lens (21) faces an outgoing direction of the first collimating lens (1), and a smaller curvature side of the second cylindrical lens (22) faces an outgoing direction of the first cylindrical lens (21).

4. A small divergence angle laser based on beam shaping technique as claimed in claim 3 wherein, The first and second collimating lenses are aspherical lenses with a focal length of 8 mm; The first cylindrical lens (21) in the fast axis beam-reducing device (2) is a flat convex cylindrical lens with a focal length of 25 mm, the second cylindrical lens (22) is a flat convex cylindrical lens with a focal length of 7.7 mm, and the beam expander (3) is a 20 times beam expander.

5. A small divergence angle laser based on beam shaping technique as claimed in claim 3 wherein, The first and second collimating lenses are aspherical lenses with a focal length of 8 mm; The first cylindrical lens (21) in the fast axis beam-reducing device (2) is a flat convex cylindrical lens with a focal length of 25 mm, the second cylindrical lens (22) is a flat concave cylindrical lens with a focal length of -6.4 mm, and the beam expander (3) is a 20 times beam expander.

6. A small divergence angle laser based on beam shaping technology according to any one of claims 1-5, characterized in that, The outgoing end of each laser diode is covered with a protective glass sheet.

7. A small divergence angle laser based on beam shaping technology according to any one of claims 1-5, characterized in that, Each laser diode is mounted in a clamp (8) with a central opening at the front end, the clamp (8) is attached to a semiconductor cooler (9) at the end, the semiconductor cooler (9) is connected with a heat sink (10); a sleeve (11) is mounted at the front end of the clamp (8), a collimating lens corresponding to the laser diode is mounted in the sleeve (11), and the sleeve (11) is coaxially arranged with the clamp (8).

8. A small divergence angle laser based on beam shaping technique as claimed in claim 7 wherein, A thermistor (12) for temperature measurement is mounted on the clamp (8).

Images