CN102570262A - Hollow ring-shaped light beam output solid laser and using method therefor - Google Patents

Abstract

A solid-state laser with hollow annular beam output and its use method. The laser includes a pump source, and the direction of the pump light output by the pump source is a coupling collimator lens with the same optical axis, a coupling focusing lens, a laser gain medium, and an output laser. Mirror, the output end of the pump source is placed at the focal point of the coupling collimator lens, the front surface of the laser gain medium is coated with a laser high reflection film and a pump light anti-reflection film as a front cavity mirror, the laser gain medium The rear surface is coated with a laser anti-reflection film, the output mirror and the front surface of the laser gain medium form a laser resonant cavity, and the coupling focusing lens and the laser gain medium each have a movement adjustment mechanism along the optical axis direction. Through adjustment, the pump light can pass through The focal point of the pump light coupled to the focusing lens is located inside or outside the laser gain medium. The invention outputs a hollow ring laser beam, and has the characteristics of simple and compact structure, good beam quality, stable system operation and strong realizability.

Description

Solid-state laser with hollow ring beam output and method of use thereof

technical field

The invention relates to a solid-state laser, in particular to a solid-state laser with a hollow ring beam output and a method for using the same.

Background technique

Due to the continuous development of laser technology and its applications, more and more people pay attention to hollow ring laser beams. Its output beam has a special mode intensity distribution, which has been used in super-resolution microscopy by virtue of its annular space distribution characteristics, and is also widely used in materials processing and optical particle manipulation because of its special orbital angular momentum characteristics. .

Currently, there are several methods for generating hollow ring beams. The most common of these is to use the fundamental mode (TEM ₀₀ ) laser beam to get it through a hologram or spatial light modulator; this method will cause a large power loss, and the fundamental mode beam output is obtained first (the output efficiency is generally 40%) , and then only 30% of the input fundamental mode beam can be converted into a hollow beam, and its total efficiency is about 10%; and because the hologram and the modulator have a relatively low damage threshold, their output power is also limited. Its output power is generally less than 100mW. It is also possible to obtain ring light output by placing a phase plate or a special lens in the laser resonator; but this method produces a large loss due to the introduction of additional components in the cavity, so its output power and efficiency are limited. limit. Another method is to pump the crystal with hollow distributed pump light through special pumping conditions, move the crystal at a certain position, and use a flat concave cavity structure to obtain a hollow ring beam output; the shortcomings of this method require A hollow pump beam is obtained, and the crystal position accuracy is required to be high (in the range of 0.2 mm), so its output conditions are difficult to control and the output is unstable, and its output power has not been reported. A recently reported method is to pump a neodymium-doped yttrium vanadate slab crystal bounce (bounce) laser at the laser diode end, which can obtain a high-power hollow beam output, and its optical path is a folded distribution in the cavity. Two axicons; the disadvantage is that the threshold is high (10W), and it must work under the condition of high pump power (greater than 40W). The system is complex, and it is difficult to obtain a hollow beam output in the case of low-power pumping.

Therefore, the current hollow ring beam laser has disadvantages such as complex structure, low efficiency, low output power, and poor stability.

Contents of the invention

In order to overcome the deficiencies of the above-mentioned technologies, the present invention proposes a solid-state laser with hollow annular beam output and its use method. The laser has the advantages of simple structure, compact structure, low threshold, high efficiency, high output power, good beam quality, and stable system operation. Features.

Technical solution of the present invention is as follows:

A solid-state laser with a hollow ring laser beam output, including a pump source, characterized in that its composition is: the direction of the pump light output by the pump source is a coupling collimator lens with the same optical axis, a coupling focusing lens, and a laser gain medium. and an output mirror, the output end of the pump source is placed at the focal point of the coupling collimator lens, and the front surface of the laser gain medium is coated with a laser high reflection film and a pump light anti-reflection film as the front surface A cavity mirror, the rear surface of the laser gain medium is coated with a laser anti-reflection film, the output mirror and the front surface of the laser gain medium form a laser resonator, and the coupling focusing lens and the laser gain medium each have The direction movement adjustment mechanism can make the focus of the pump light passing through the coupling focusing lens be located inside or outside the laser gain medium through adjustment.

The laser gain medium is isotropic laser crystal or laser glass doped with rare earth, and the laser crystal includes yttrium vanadate crystal doped with neodymium or ytterbium, gadolinium vanadate crystal doped with neodymium or ytterbium, Neodymium-doped or ytterbium-doped yttrium aluminum garnet crystals or neodymium-doped or ytterbium-doped titanium sapphire crystals.

The output mirror can be a plane mirror or a concave mirror.

The pumping source is a laser, a laser diode array, or a laser diode output from a pigtail.

The method for using the solid-state laser output by the hollow ring laser beam is characterized in that the method uses the end-pumped laser gain medium to realize defocus pumping by adjusting the position of the pump light coupling focusing lens or the position of the gain medium, or adjusting The position of the output mirror is used to control the length of the resonant cavity and the appropriate control of the pump power, including the following three methods:

In the first method, when the positions of the laser gain medium and the output mirror are fixed, by adjusting the position of the coupling focusing lens, the focal point of the pump light is at a certain position outside or inside the crystal to achieve defocus pumping, and at the same time adjust the pump power appropriately , so as to obtain the hollow ring beam output;

In the second method, when the focus of the pump light is located near the front surface of the laser gain medium and the position relative to the front surface of the laser gain medium is fixed, the position of the output mirror is adjusted horizontally (the length of the resonator changes), and the pump is adjusted appropriately. Pu power, so as to obtain a hollow ring beam output;

The third method, when the position of the coupling focusing lens and the position of the output mirror is fixed, adjust the position of the laser gain medium horizontally so that the focus of the pump light is at a certain position outside or inside the medium, and at the same time adjust the pump power appropriately to achieve a hollow ring beam output.

The present invention has the following advantages:

1. Realize out-of-focus pumping by adjusting the pump light coupling system or the position of the laser gain medium (the focus of the pump light is not on the front surface of the laser gain medium), or adjust the position of the output mirror to control the length of the resonant cavity and properly control the pump power, Thus, the output of the hollow ring laser beam is obtained, and no other additional components are introduced inside or outside the cavity. This kind of laser has the advantages of simple and compact structure, low threshold value, high working efficiency, high output power, good beam quality, stable operation of the laser system, and strong realizability.

2. The laser gain medium works at room temperature without adding any cooling device, so that the laser structure is simpler and more compact, and the cost is lower.

3. In this laser, the solid pump light is used for pumping, and a higher power hollow ring beam output can be obtained under the condition of low pump power.

4. Due to the end-pump coupling system, the cavity mirror film is plated on the front surface of the laser gain medium as the front cavity reflector, which together with the output mirror forms a flat cavity or flat concave cavity structure, which can obtain high beam quality laser output.

Description of drawings

Figure 1 is a general block diagram (front view in section) of a preferred embodiment of the laser system of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Please refer to Fig. 1 first, Fig. 1 is the overall block diagram (front view section) of the preferred embodiment of the laser system of the present invention As can be seen from the figure, the solid-state laser output by the hollow ring laser beam of the present invention includes a pumping source 1, and its composition is : The direction of the pump light output by the pump source 1 is sequentially the coupling collimator lens 2, the coupling focus lens 3, the laser gain medium 4 and the output mirror 5 on the same optical axis, and the output end of the pump source 1 is placed At the focal point of the object space of the coupling collimating lens 2, the front surface of the laser gain medium 4 is plated with a laser high reflection film and a pump light anti-reflection film as a front cavity mirror, and the rear surface of the laser gain medium 4 is plated with a laser Anti-reflection coating, the output mirror 5 and the front surface of the laser gain medium 4 form a laser resonator, and the coupling focusing lens 3, laser gain medium 4 and output mirror 5 all have movement adjustment along the optical axis direction mechanism, through adjustment, the focus of the pump light passing through the coupling focusing lens 3 can be located at a certain position inside or outside the laser gain medium 4 .

By adjusting the pump light coupling system or the position of the laser gain medium to achieve defocus pumping (the focus of the pump light is not on the front surface of the laser gain medium), or adjusting the position of the output mirror to control the length of the resonant cavity and control the pump power, thus directly The solid-state laser that obtains the hollow ring laser beam output is composed of the following parts: pump source 1, coupling collimating lens 2, coupling focusing lens 3, laser gain medium 4, and output mirror 5. The laser gain medium 4 can work at room temperature without adding any cooling device. By moving the position of the coupling focusing lens 3 in the horizontal direction so that the focus of the pump light is at a certain position outside or inside the laser gain medium 4, defocus pumping is realized, and the front part of the pump light or the rear part of the pump light is used to pump the focus of the focused pump light. The light is used to pump the laser gain medium 4 . The output mirror 5 and the front surface of the laser gain medium 4 constitute a laser cavity.

Below are the concrete parameters of the embodiment of the present invention:

1. The laser gain medium is C-cut neodymium-doped yttrium vanadate crystal, the doping concentration of neodymium ions is 1.5 at.%, the specific dimensions are length l = 5mm, width w = 5mm, height d = 5mm, and the front surface is plated with 808nm Anti-reflection, 1064nm high-reflection coating (as a front cavity mirror), and 1064nm anti-reflection coating on the rear end. Crystals work at room temperature.

，数值孔径为0.22，发射波长为808nm，为连续泵浦，额定功率4W。 2. The pump source is a laser diode output from a fiber-coupled pigtail. Pigtail core diameter is 200

, the numerical aperture is 0.22, the emission wavelength is 808nm, it is continuously pumped, and the rated power is 4W.

3. The end face coupling system includes a collimating coupling lens 2 and a coupling focusing lens 3, and the focal lengths of the lenses are 8mm and 40mm respectively. The output end of the pump source is placed at the object focus of the collimating coupling lens 2, and the focus of the pump light is positioned at a certain position outside or inside the crystal by moving the coupling focusing lens 3 in the horizontal direction to achieve defocus pumping.

4. The output mirror 5 is a flat mirror with a transmittance of 10% at a wavelength of 1064nm.

5. The distance between the coupling focusing lens 3 and the Nd-doped yttrium vanadate crystal 4 is between 42 mm and 46 mm, the length of the laser cavity is between 12 mm and 30 mm, and the pumping power of the laser diode is between 2.4 W and 3.0 W.

In this embodiment, there are three adjustment methods to obtain the hollow ring beam output:

The first method: the position of the crystal and the output mirror is fixed. At this time, the length of the resonant cavity is 16mm. Then adjust the position of the coupling focusing lens. When the distance between it and the front surface of the crystal is between 42mm and 46mm, adjust the pump power to 2.4~3.0 In the W range, a hollow ring beam output can be obtained.

The second method: the coupling focusing lens is fixed at a position 43mm away from the front surface of the crystal, and only the position of the output mirror is adjusted. When the length of the resonant cavity is between 12mm and 30mm, the pump power can be adjusted within the range of 2.2W~3.5W. A hollow ring beam output is obtained.

The third method: the position of the coupling focusing lens and the output mirror is fixed, the distance between the two is 60mm, and then the position of the laser crystal is adjusted. When the distance from the front surface of the crystal to the lens is between 30mm and 36mm, the pump power is adjusted at 2.5 In the range of W~3.2W, hollow ring beam output can be obtained.

The following is the output result of the embodiment:

Its threshold power is 2.0W, and the slope efficiency is 30%. When the distance from the front surface of the crystal to the lens is 45mm, the resonant cavity length is 20mm, and the pump power is 3.0W, the output power of 202mW can be obtained, and the beam quality factor (M2) Hollow ring beam output of approximately 2 in horizontal and vertical directions.

In summary, the present invention has the characteristics of simple design, compact structure, low threshold, high efficiency, high output power, easy implementation, long-term stable operation at room temperature, etc., and can realize hollow ring laser output of solid-state lasers.

Claims (5)

1. the solid state laser of a hollow annular laser beam output; Comprise pumping source (1); Be characterised in that its formation is: the pump direction in pumping source (1) output is coupling collimating lens (2), coupling focusing lens (3), gain medium (4) and outgoing mirror (5) with optical axis successively; The output of described pumping source (1) places described coupling collimating lens (2) object focus place; The front surface plating laser high-reflecting film of described gain medium (4) and pump light anti-reflection film are as front cavity mirror; The back surface plating laser anti-reflection film of this gain medium (4); Described outgoing mirror (5) and gain medium (4) front surface constitute laserresonator, and described coupling focusing lens (3) and gain medium (4) respectively have the mobile governor motion along described optical axis direction, through regulating the inside or the outside that can make pump light be positioned at described gain medium (4) through the focus of the pump light of described coupling focusing lens (3).

2. solid state laser according to claim 1; It is characterized in that described gain medium (4) is rear-earth-doped isotropic laser crystal or laser glass, described laser crystal comprises neodymium-doped or mixes the yttrium vanadate crystal of ytterbium, neodymium-doped or mix vanadic acid gadolinium crystal, the neodymium-doped of ytterbium or mix the yag crystal or the neodymium-doped of ytterbium or mix the titanium gem crystal of ytterbium.

3. solid state laser according to claim 1 is characterized in that described outgoing mirror (5) can be level crossing or concave mirror.

4. according to each described solid state laser of claim 1 to 3, it is characterized in that the laser diode of described pumping source (1) for laser, diode laser matrix or tail optical fiber output.

5. the method for using of the solid state laser of the described hollow annular laser beam output of claim 1; Be characterised in that this method is to utilize the end pumped laser gain media; The out of focus pumping is realized in position through regulating pump light coupling focusing lens position or gain media; Perhaps regulate the outgoing mirror position and control cavity length and suitably control the pumping watt level, specifically comprise following three kinds of methods:

First method; Under the situation of gain medium and outgoing mirror fixed-site; Make the outside or inner certain position place realization out of focus pumping of pump light focal spot through regulating the coupling focusing lens position, suitably regulate pump power simultaneously, thereby obtain the output of cavity ring shaped light beam in crystal;

Second method; Be positioned under near the position gain medium front surface and the situation in the pump light focus with respect to the fixed-site of gain medium front surface; Through horizontal adjustment outgoing mirror position (cavity length change); Suitably regulate pump power simultaneously, thereby obtain the output of cavity ring shaped light beam;

The third method; Under coupling focusing lens position and outgoing mirror fixed-site situation; Make the pump light focus at medium outside or inner certain position place through horizontal adjustment gain medium position, suitably regulate pump power simultaneously, thus the output of realization cavity ring shaped light beam.