CN104201551A - Laser and polarization compensating direct end pumping device thereof - Google Patents

Abstract

The invention relates to the field of lasers and provides a laser and a polarization compensation end face direct pumping device thereof. The device is used for pumping light and seed light conversion, which includes a pumping source distributed sequentially on the same optical axis, a first short-wave pass lens, a crystal, a second short-wave pass lens, and a four-dimensional lens for polarization rotation of the pump light. One-quarter wave plate and thermal focal length compensating mirror. The pump light is output by the pump source, and achieves secondary polarization compensation pump absorption on the optical axis; the seed light is incident on the first short-wave pass lens in the optical axis, and is reflected and transmitted through the crystal to The second short-wave pass lens reflects the seed light by the second short-wave pass lens. The invention adopts the polarization compensation end face direct pumping device, which can greatly improve the light-to-light conversion efficiency of the laser system.

Description

Laser and its polarization-compensated end-face direct pumping device

technical field

The invention relates to the field of lasers, in particular to a laser and a polarization compensation end face direct pumping device thereof.

Background technique

The effect of controlling the polarization state of the pump light will directly lead to the absorption of the pump light by the laser crystal, thus affecting the stable output of the laser. When using 808nm, 880nm, 888nm and other pumping light to pump Nd:YVO ₄ crystal, the absorption of the pumping light whose polarization direction is parallel to the c-axis direction of the crystal is much larger than that of the pumping light parallel to the a-axis direction, such a large The absorption coefficient will cause the pump light parallel to the c-axis direction to be strongly absorbed by the crystal within a few millimeters, but the light polarized along the a-axis direction needs to go through a long transmission to be absorbed; in addition, due to the pump Pu light is absorbed by the crystal within a short distance, which will cause the temperature of the crystal end face to rise sharply, resulting in serious thermal effects of the crystal, directly affecting whether the crystal is damaged, and the light-to-light conversion efficiency is also low. For example, as shown in Figure 1, the doping concentration is 1at.% Nd: YVO ₄ crystal (a cut) absorption spectrum, as can be seen from the figure, near the wavelength of 880nm, Nd: YVO ₄ crystal in two axial directions The absorption coefficient of pump light is different, α _c = 16cm ^-1 , α _a = 5cm ^-1 ; near the wavelength of 808nm, Nd: YVO ₄ crystal has different absorption coefficient of pump light in two axial directions, α _c = 35 cm ^-1 , α _a = 18 cm ^-1 .

Contents of the invention

The technical problem solved by the present invention is to provide a laser and its polarization compensation end-face direct pumping device, which is used to improve the light-to-light conversion efficiency of the laser system.

In order to solve the above technical problems, the present invention provides a polarization-compensated end-face direct pumping device, which is used for pumping light and seed light conversion, which includes a pumping source distributed sequentially on the same optical axis, a first short-wave pass lens, crystal, a second short-pass lens, a quarter-wave plate for pump light polarization rotation, and a thermal focal length compensation mirror; the pump light is output by the pump source and achieves a secondary Polarization compensation pump absorption; the seed light is incident on the first short-wave pass mirror in the optical axis, and reflected through the crystal to the second short-wave pass mirror, and the second short-wave pass mirror reflects the seed light.

Preferably, both sides of the first and second short-pass mirrors are coated with a pump light-transmitting film, and one side is coated with a seed light-reflecting film, which is used to transmit the pump light and reflect the seed light.

Preferably, both sides of the first short-wave pass lens at the incident place of the seed light are coated with a pump light transmission film, and one side is coated with a 45° reflective film for the seed light; the second short-wave pass lens at the exit of the seed light The pump light transmission film is coated on both sides, and the seed light reflection film is coated on one side. The seed light reflection coating is 45° or 0°. When the coating is a 45° film, the single gain of the seed light is amplified. When the coating is a 0° film, the seed light is double-gained.

Preferably, the pump source is one of fiber-coupled modules, LD stacks, and BAR bars, and the wavelengths of the pump sources are 808nm, 888nm, and 880nm.

Preferably, both sides of the crystal are coated with transmissive films for pump light and seed light, and the crystal has different absorption coefficients for pump light in the two crystal axis directions.

Preferably, both sides of the quarter-wave plate are coated with pump light anti-reflection coatings, which are used to realize the polarization rotation of the pump light, and the pump light passes through the quarter-wave plate twice to realize The phase angle between the π and σ polarizations of the pump light is rotated by 90°.

Preferably, the thermal focal length compensation mirror is a mirror with a convex surface coated with a pump light 0° reflection film.

In order to solve the above technical problems, the present invention provides a laser, which has a polarization compensation end-face direct pumping device.

The invention provides a laser and a polarization-compensated end-face direct pumping device thereof. By adopting the polarization-compensated end-face direct pumping technology, the optical-to-optical conversion efficiency of the laser system can be greatly improved.

Description of drawings

Fig. 1 is the Nd that doping concentration is 1at.% in the prior art: YVO ₄ crystals in a cut absorption spectrum;

Fig. 2 is a single-pass enlarged schematic diagram of the polarization compensation end face direct pumping device of the present invention;

Fig. 3 is a double-pass enlarged schematic diagram of the polarization-compensated end-face direct pumping device of the present invention.

Detailed ways

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

Please refer to Fig. 2 and Fig. 3, the present invention provides a polarization-compensated end-face direct pumping device, which is used for pumping light and seed light conversion, and it includes a pumping source 10 distributed sequentially on the same optical axis, a first short-wave A pass lens 20, a crystal 30, a second short-wave pass lens 40, a quarter-wave plate 50 for pump light polarization rotation, and a thermal focal length compensation mirror 60. The pump light is output by the pump source 10, and achieves secondary polarization compensation pump absorption on the optical axis; the seed light is incident on the first short-wave pass mirror 20 in the optical axis, and is reflected and transmitted From the crystal 30 to the second short-pass mirror 40 , the seed light is reflected by the second short-pass mirror 40 .

In the above device, the pump light optical path and the seed light optical path can be realized.

Wherein, in the optical path of the pumping light, the pumping light passes through the first short-wave pass lens 20, the crystal 30, the second short-wave pass lens 40, the quarter-wave plate 50, and is reflected by the thermal focal length compensation mirror 60, and again Through the quarter-wave plate 50 , the second short-wave pass lens 40 , the crystal 30 , and the first short-wave pass lens 20 , the secondary polarization-compensated pump absorption of the pump light is realized.

Wherein, the optical path of the seed light is that the seed light is reflected by the first short-wave pass lens 20 , transmitted by the crystal 30 , and reflected by the second short-wave pass lens 40 .

In the present invention, an a-cut Nd:YVO ₄ crystal is taken as an example for illustration, and an LD fiber coupling module is used to pump the crystal 30, and the pumping light is circularly polarized light consisting of π polarization and σ polarization. When the pump light enters the crystal 30 from left to right for the first time, since the crystal absorbs π-polarized light much more than σ-polarized light, the π-polarized light is absorbed in large quantities, and the π-polarized light in the remaining pump light is much smaller than the σ-polarized light; the remaining pump light After passing through the thermal focal length compensation mirror 60 and passing through the quarter-wave plate 50 twice, the σ polarization is rotated to π polarization and then passes through the crystal 30 again to realize the second polarization compensation pump light absorption. Pump coupling is the key technology to improve efficiency. Moreover, in this embodiment, both sides of the first and second short-wave pass mirrors 20, 40 are coated with a pump light transmissive film, and one side is coated with a seed light reflective film, which is used to transmit pump light and Reflects seed light. Specifically, the first short-wave pass lens 20 at the incident place of the seed light is coated with a pump light transmissive film on both sides, and one side is coated with a 45° reflective film for the seed light; The two sides of the pass-through mirror 40 are coated with a pump light transmissive film, and its single side is coated with a seed light reflective film, and the seed light reflective coating is 45° or 0°. When the coating is a 45° film, the seed light will Gain amplification, when the coating is a 0° film, the gain of the seed light is doubled.

For the above devices, generally speaking, the pump source 10 is one of the fiber-coupled module, LD stack, and BAR bar, to realize the output of pump light for pumping the pump crystal 30, and its wavelength is preferably 808nm, 888nm, 880nm, but not limited to this wavelength; the crystal 30 is a crystal 30 with different absorption coefficients for the pump light in the two crystal axis directions, and its two sides are coated with a transmissive film for the pump light and the seed light. Absorb the energy of the pump light to realize the energy amplification of the seed light; both sides of the quarter-wave plate 30 are coated with a pump light anti-reflection film, which is used to realize the polarization rotation of the pump light, and the pump light is twice Through the quarter-wave plate 50, the conversion between the pump light π polarization and σ polarization is realized, that is, the phase angle is rotated by 90°; the thermal focal length compensation mirror 60 is a convex surface coated with a pump light 0° reflection film The reflector realizes the thermal focal length for the crystal 30 to absorb the pump light, resulting in the thermal effect.

The invention provides a polarization compensation end face direct pumping device, which can greatly improve the light-to-light conversion efficiency of the system by adopting the polarization compensation end face direct pumping technology. In addition, the polarization-compensated end-face direct pumping device adopted in the present invention can be used in any laser, such as a laser oscillator, a power amplifier, and the like.

It can be understood that those skilled in the art can make various other corresponding changes and deformations according to the technical concept of the present invention, and all these changes and deformations should belong to the protection scope of the claims of the present invention.

Claims (8)

1. A polarization-compensated end-face direct pumping device, used for pumping light and seed light conversion, is characterized in that, comprises the pumping source that is positioned at the same optical axis and distributes successively, the first short-wave pass mirror, crystal, the second short-wave Pass mirror, quarter-wave plate for pump light polarization rotation and thermal focal length compensation mirror; the pump light is output by the pump source, and achieves secondary polarization compensation pump absorption on the optical axis The seed light is incident on the first short-wave pass lens corresponding to the optical axis, and is reflected and transmitted through the crystal to the second short-wave pass lens, and the seed light is reflected by the second short-wave pass lens. 2. The device according to claim 1, characterized in that, both sides of the first and second short-pass mirrors are coated with a pump light transmission film, and a single side is coated with a seed light reflection film, which is used to transmit Pump light and reflected seed light. 3. The device according to claim 2, wherein the first short-wave pass lens at the incident place of the seed light is coated with a pump light transmissive film on both sides, and one side is coated with a 45° reflective film for the seed light; The two sides of the second short-wave pass lens at the exit of the seed light are coated with a pump light transmission film, and its single side is coated with a seed light reflection film. The seed light reflection coating is 45 ° or 0 °, and the coating is When the film is 45°, the seed light is amplified with a single gain, and when the coating is a 0° film, the seed light is amplified with double gain. 4. The device according to claim 1, wherein the pumping source is one of a fiber coupling module, an LD array, and a BAR bar. 5. The device according to claim 1, characterized in that: the two sides of the crystal are coated with transmissive films for pumping light and seed light, and the crystal absorbs pumping light in the direction of two crystal axes. Crystals with different coefficients. 6. The device according to claim 1, characterized in that, both sides of the quarter-wave plate are coated with a pump light anti-reflection film, which is used to realize the polarization rotation of the pump light, and the pump light Pass through the quarter-wave plate twice to achieve a 90° phase angle rotation between the π and σ polarizations of the pump light. 7 . The device according to claim 1 , wherein the thermal focal length compensation mirror is a mirror whose convex surface is coated with a 0° reflection film for pump light. 8. A laser, characterized in that it has the polarization-compensated end-face direct pumping device as claimed in claims 1-7.