CN108445641A - A kind of tunable semiconductor laser optical optical tweezers system - Google Patents

Abstract

The invention discloses a tunable semiconductor laser optical tweezers system, which includes an edge-emitting semiconductor laser, a plano-convex cylindrical lens, a gradient refractive index lens, an axicon and a focusing lens, and a plano-convex cylindrical lens arranged in sequence according to the laser light path of the laser. It should be placed at the position where the light emission and propagation of edge-emitting semiconductor lasers presents a circular distribution. The distance between the focusing lens and the apex of the axicon should be greater than the focal length of the focusing lens, and less than the distance between the outgoing light of the edge-emitting semiconductor laser passing through the beam shaping system. The post-transmission axicon produces the maximum diffraction-free distance for Bessel-like beams. In the optical tweezers system of the present invention, as long as the distance between the gradient refractive index lens (GRIN) and the plano-convex cylindrical lens is moved, local hollow beams of different sizes can be obtained to capture and manipulate particles. The optical tweezers system is convenient for the micro-integration of the optical tweezers system, without worrying about the optical damage of the particles, and provides a new effective way for the semiconductor laser optical tweezers system.

Description

A Tunable Semiconductor Laser Optical Tweezers System

technical field

The invention relates to the field of laser beam shaping, in particular to an adjustable semiconductor laser optical tweezers system.

Background technique

Optical tweezers are also called single-beam gradient optical traps. Simply put, it uses a three-dimensional potential well formed by a highly concentrated laser to capture and manipulate tiny particles. Optical tweezers is a three-dimensional gradient optical trap formed by the mechanical effect of momentum transfer between light and matter to manipulate particles. The local hollow beam (Bottle beam) is a beam with a local three-dimensional closed dark hollow area along the direction of light transmission. Due to the three-dimensional closed dark hollow region and extremely high intensity gradient, the local hollow beam can be used as a powerful tool such as laser catheter, optical tweezers and optical wrench. Local hollow beam optical tweezers have been successfully applied to the manipulation of living cells and subcellular particles due to their advantages of non-contact and low damage. Therefore, optical tweezers technology is widely used in the field of biology.

At present, there have been many reports on the acquisition methods of local hollow beams, such as optical holography, Bessel optical coherence method, Bessel optical focusing method, etc. However, most of them are based on He-Ne lasers as light sources. In terms of semiconductor lasers (LD), there are few reports on the direct application of Bessel beams and local hollow beams. They are mostly used as partially coherent light sources for comparison with He-Ne lasers. In terms of semiconductors used as light sources to generate local hollow beams, the number of research reports and the level of in-depth research are far behind those of He-Ne laser light source systems, and there is a lack of systematic research on the regulation of semiconductor laser far-field light fields.

Semiconductor lasers have high conversion efficiency, small size, light weight, and diversification, which facilitate the miniaturization of the system and make the system more compact. The non-diffraction beam generated by the semiconductor laser through the axicon focusing system will be larger than the size of the central lobe compared to solids and gases. The small size of the laser has obvious advantages if the semiconductor laser is directly applied to generate a local hollow beam, whether it is in the application field of biology or atom cooling. However, due to the influence of the asymmetric optical waveguide, the output beam of the semiconductor laser is asymmetrical in the direction perpendicular to the junction plane and parallel to the junction plane, the output beam is an astigmatic elliptical Gaussian beam, and the beam quality is not balanced. Therefore, beam shaping methods must be used in practical applications to solve the problems of poor beam quality and low power density. It has proven practical to reduce the central lobe size of Bessel beams produced by high-power semiconductor lasers to levels not achievable by conventional focusing. If the miniaturization of the system is considered, the light source should be more compact, and it is necessary to consider replacing the solid-state or gas laser with a semiconductor laser.

Contents of the invention

In order to solve the above problems, the present invention proposes a tunable semiconductor laser optical tweezers system, which adopts the following technical scheme:

A tunable semiconductor laser optical tweezers system is characterized in that: it comprises a side semiconductor laser and a plano-convex cylindrical lens, a gradient refractive index lens (GRIN), an axicon and a focusing lens placed in sequence according to the laser light path of the laser, and the above-mentioned plano-convex The cylindrical lens is placed at the position where the light emission of the edge-emitting semiconductor laser is distributed in a circular manner. The distance between the above-mentioned focusing lens and the apex of the axicon should be greater than the focal length of the focusing lens and less than that of the semiconductor laser after the output beam passes through the shaping system. Maximum non-diffraction distance through an axicon to produce a Bessel-like beam.

As a preference, the above-mentioned semiconductor laser is an edge-emitting semiconductor laser.

As a preference, f _x = f _y of the gradient index lens (GRIN), where f _x is the focal length of the gradient index lens (GRIN) in the x direction, and f _y is the focal length of the gradient index lens (GRIN) in the y direction.

As a preference, the variable divergence angle α emitted by the semiconductor laser after being shaped by the beam system is 0°-1.5°.

As a preference, the above-mentioned optical tweezers system uses a local hollow beam to capture and manipulate particles

Compared with the prior art, the beneficial technical effect of the present invention is that the laser beam emitted by the edge type semiconductor laser passes through the beam shaping system in sequence, and is incident on the axicon, forming a Bessel-like beam within a certain distance behind the axicon. The maximum non-diffraction distance of the beam is to form a local hollow beam after the focusing lens, and use the generated local hollow beam to perform optical tweezers operation. The edge-type semiconductor laser adopts a beam shaping system with controllable divergence angle, which can control the radius of the incident beam on the incident axicon and the distance without diffraction. Therefore, as long as the distance between the plano-convex cylindrical lens and the GRIN is controlled, laser beams with different divergence angles and local hollow beams with different sizes can be obtained. Therefore, the present invention provides an effective way for a tunable semiconductor laser optical tweezers system. In the tunable semiconductor laser optical tweezers system of the present invention, the optical tweezers model structure is simple, and the optical tweezers operation is carried out by using the local hollow beam, and the "black hole" of the light field of the local hollow beam is not easy to cause damage to living material cells. It is suitable for the capture and manipulation of most cells and particles, and has a simple structure. Different particle manipulations can be performed indirectly through the size-changing local hollow beam without worrying about the damage of light to the particles. It proposes a new method for the application of the optical tweezers system. The tuning idea solves the limitations of the existing system optical tweezers.

Description of drawings

FIG. 1 is a schematic diagram of the optical path of the optical system of the present invention.

Fig. 2 is a schematic diagram of the beam shaping of the semiconductor laser in the system of the present invention.

Detailed ways

In order to further explain the system solution of the present invention, the present invention will be described in detail below through specific implementation.

The optical path schematic diagram shown in Figure 1, the present invention is a kind of tunable semiconductor laser optical tweezers system, and it comprises that it comprises edge-emitting semiconductor laser 1 and the plano-convex cylindrical lens 2 that places in turn according to the laser optical path of laser device, gradient refraction Ratio lens (GRIN) 3, axicon 4 and focusing lens 5.

Due to the influence of the asymmetric optical waveguide, the output beam of the edge-emitting semiconductor laser 1 has a large difference between the fast axis and the slow axis: there are large and asymmetric divergence angles in the two directions; the beam waist in the two directions is not in the At the same position, there is inherent astigmatism; the source size in the fast axis direction is about 1 μm, and the source size in the slow axis direction is about 75 μm.

Figure 2 is a schematic diagram of semiconductor laser beam shaping. First, the edge-type semiconductor laser 1 is turned on, and a plano-convex cylindrical lens 2 is placed at an appropriate position. After the laser beam passes through the plano-convex cylindrical lens 2, the divergence angle of the laser beam in the fast axis direction passes through Compress to achieve the divergence angle consistent with the slow axis direction. A gradient refractive index lens (GRIN) 3 is placed at the m position thereafter, and the divergence angle α of the laser beam output is controlled by controlling the plano-convex cylindrical lens 2 and the gradient refractive index lens (GRIN) 3 .

In Fig. 1, beams with different divergence angles α emerge after passing through the beam shaping system, and after entering the axicon 4, a Bessel-like beam is formed within a certain distance behind the axicon 4 and an approximately non-diffraction region. In this non-diffraction region, the maximum non-diffraction distance can be calculated by the formula Z _max =a/[(n-1)γ-α], where a is the radius of the laser beam incident on the axicon 4, and n is the axicon 4 The refractive index, γ is the cone angle of the axicon 4. A focusing lens 5 is placed at the position z ₀ behind the axicon 4, and a local hollow beam is formed behind it. When controlling the laser beams with different divergence angles α after passing through the beam shaping system, local hollow beams of different sizes can be formed.

When in use, the local hollow beam is used to form a three-dimensional gradient light field of optical tweezers for particle capture and manipulation.

In this example, under the condition that the plano-convex cylindrical lens can satisfy the fast axis compression, the thickness of the plano-convex cylindrical lens should be as small as possible to facilitate the miniaturization and integration of the optical system.

The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process conversion made by using the description of the present invention and the contents of the accompanying drawings, or directly or indirectly used in other related systems fields, all of which are equally included in the scope of patent protection of the present invention.

Claims (5)

1. a kind of tunable semiconductor laser optical optical tweezers system, it is characterised in that：Including side semiconductor laser (1) and press laser Plano-convex cylindrical lens (2), gradient-index lens (GRIN) (3), axicon (4) and the focusing that the laser optical path of device is sequentially placed are saturating Mirror (5), above-mentioned flat column convex lens (2) are placed on the position that semiconductor laser (1) light goes out in communication process to present circular distribution Place, above-mentioned condenser lens (5) with axicon (4) vertex between at a distance from should be greater than the focal lengths of condenser lens (5), and less than semiconductor Laser (1) outgoing beam generates the maximum the non diffracting distance of class bessel beam after orthopedic systems through axicon (4).

2. a kind of tunable semiconductor laser optical optical tweezers system as described in claim 1, it is characterised in that：Above-mentioned semiconductor swashs Light device (1) is edge emitting formula semiconductor laser.

3. a kind of tunable semiconductor laser optical optical tweezers system as described in claim 1, it is characterised in that：Graded index is saturating The f of mirror (GRIN) (3)_x=f_y, f_xFor the focal length of x direction gradients index lens (GRIN) (3), f_yFor y direction gradient refractive index The focal length of lens (GRIN) (3).

4. a kind of tunable semiconductor laser optical optical tweezers system as described in claim 1, it is characterised in that：Semiconductor laser (1) the change angle of divergence alpha being emitted after beam system shaping is 0 °~1.5 °.

5. a kind of tunable semiconductor laser optical optical tweezers system as described in claim 1, it is characterised in that：Above-mentioned optical optical tweezers system Particle is captured and operated with bottle beams.