CN105811231B - A kind of big energy picosecond laser of volume Bragg grating - Google Patents

Abstract

The invention relates to the field of laser technology, in particular to a volume Bragg grating high-energy picosecond laser. The laser device disclosed by the present invention includes: a box body, two parallel volume Bragg grating end mirrors VBG are respectively arranged at the two ends inside the box body to form an optical resonant cavity, in which an electro-optic switch, a polarizer, a saturation Absorber and gain pump modules, concave lens. The gain pump module strongly pumps the laser crystal to generate oscillating light, and the oscillating light is gradually compressed into short pulses under the action of the saturable absorber. At the same time, under the action of the volume Bragg grating end mirror VBG, the pulse width is further compressed. At the moment when the pulse energy is the largest, the electro-optical switch is added with high voltage, that is, through the cavity emptying technology, the high-energy picosecond pulse is output through the polarizer and the full mirror, and a high-energy picosecond pulse laser is obtained, thus solving the current large-scale problem. Energy picosecond pulsed lasers have the problems of large volume, complex devices and low stability.

Description

A Volume Bragg Grating High Energy Picosecond Laser

technical field

The invention relates to the field of laser technology, in particular to a volume Bragg grating high-energy picosecond laser.

Background technique

Picosecond lasers are more and more widely used in industrial processing, surface modification, satellite ranging, life science and other fields. The various metabolic times of living organisms are about 10 ^-12 s, and the use of picosecond pulsed light can affect the metabolism of this time period. Therefore, picosecond lasers have been widely used in various researches in life sciences. The study of mammalian cell DNA has beneficially promoted human beings' understanding of themselves. The picosecond laser pulse is narrow, the light intensity is high, the distance measurement accuracy is high, and the measurement distance is long. In satellite ranging, its accuracy can reach 3mm. During picosecond processing, it generates less heat, has high processing precision, has no selectivity for materials, and has high impact strength. It is widely used in micro-nano processing and surface modification of materials. At the same time, the picosecond laser is also an effective pump source for laser frequency conversion.

Usually, the picosecond pulse with high energy is first generated by mode-locking with a repetition rate of 100 MHz, and the single pulse is a nanojoule-level picosecond pulse seed light, and then regenerated and amplified to obtain a single-pulse energy of millijoule level. Picosecond pulses are amplified by traveling waves to obtain higher energy picosecond pulses. The longer the mode-locking cavity, the more the number of modes, and the easier it is to achieve mode-locking. Considering the loss of the cavity, the general stable mode-locking cavity length is about 1.5m, and in the regenerative amplifier cavity, the switching time of the electro-optic switch (approx. 5ns) effect, the general cavity length is about 1.2m. As a result, high-energy picosecond pulses are obtained by mode-locking plus regenerative amplification. The laser is bulky, the device is complex, and the stability is also reduced.

Contents of the invention

The object of the present invention is a volume Bragg grating high-energy picosecond laser, to solve the problems of large volume, complex devices and low stability of lasers for obtaining high-energy picosecond pulses at the present stage.

The invention provides a volume Bragg grating high-energy picosecond laser, which includes:

A box body, two parallel volume Bragg grating end mirrors VBG are respectively arranged at both ends inside the box body to form an optical resonant cavity, in which an electro-optic switch, a polarizer, a saturable absorber and Gain pumping module; a total reflection mirror is arranged on the reflection optical path of the polarizer, and the total reflection mirror is used to output the laser light generated by the laser through the laser output port, and the laser output port is arranged in the box superior;

The box body is also provided with more than one electrical terminal interface, and the electro-optic switch and gain pump module are respectively connected to a power supply device through the terminal interface.

In some embodiments, preferably, the volume Bragg grating end mirror VBG, the saturable absorber and the gain pump module are placed in a heat sink. The heat sink is a miniature heat sink, which is a device cooled by cooling water or cooling gas, and a cooling circulation interface is provided on the box.

The gain pumping module is continuous pumping or quasi-continuous pumping. When the gain pumping module is quasi-continuous pumping, the frequency of the voltage applied by the electro-optical switch is consistent with the quasi-continuous pumping frequency.

In addition, a quarter-wave plate is further arranged in the optical resonant cavity, and the gain pump module, the concave lens and the quarter-wave plate are arranged in sequence. The volume Bragg grating end mirror VBG, polarizer, saturable absorber, concave lens, quarter-wave plate, total reflection mirror and laser crystal in the gain pump module are all coated with an anti-reflection coating consistent with the wave band of the oscillating light or high reflective film.

A small hole diaphragm is also arranged in the optical resonant cavity, and the small hole diaphragm is arranged between the voltage device and the polarizer; the aperture of the small hole diaphragm is smaller than that of the laser light in the gain pump module The size of the crystal is used to suppress high-order mode oscillations and improve beam quality.

The total reflection mirror is a 45° total reflection mirror.

The volume Bragg grating high-energy picosecond laser provided by the embodiment of the present invention, compared with the prior art, the volume Bragg grating end mirror VBG arranged in parallel at both ends of the box forms an optical resonant cavity, and the optical resonant cavity is sequentially arranged with electro-optic Switches, polarizers, saturable absorbers, and gain pump blocks. The laser crystal is strongly pumped by the gain pump module to generate oscillating light, and the oscillating light is gradually compressed into short pulses under the action of the saturable absorber. Moreover, the laser is also equipped with a concave lens, which compensates the thermal lens used by the thermal effect of the gain pump module to ensure the size of the oscillation spot in the resonator and avoid device damage when the spot is too small and the energy is high. At the same time, under the action of the volume Bragg grating end mirror VBG arranged in parallel at both ends, the pulse width is further compressed. At the moment of maximum pulse energy, the electro-optic switch is applied with high voltage, that is, through the cavity emptying technology, the high-energy picosecond pulse is output through the polarizer and the total reflection mirror. Therefore, it effectively solves the problems of large volume, complex devices and low stability of lasers for obtaining high-energy picosecond pulses at the present stage.

Description of drawings

Fig. 1 is a schematic structural diagram of a volume Bragg grating high-energy picosecond laser in an embodiment of the present invention;

Fig. 2 is a side view of a box of a volume Bragg grating high-energy picosecond laser in an embodiment of the present invention;

Fig. 3 is a side view of a box of a volume Bragg grating high-energy picosecond laser in an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Aiming at the problems of large volume, complex devices and low stability of lasers for obtaining high-energy picosecond pulses at the present stage, the present invention proposes a volume Bragg grating high-energy picosecond laser. As shown in Figure 1, Figure 2, and Figure 3, it specifically includes:

In the box, two parallel volume Bragg grating end mirrors VBG are respectively arranged at both ends inside the box to form an optical resonant cavity, in which an electro-optic switch 2, a polarizer 4, a saturable absorber 5 and a gain Pump module 6, concave lens 7. The concave lens 7 is used to compensate the thermal lens used by the thermal effect of the gain pump module, to ensure the size of the oscillation spot in the resonator, and to avoid damage to the device when the spot is too small and the energy is large. A total reflection mirror 10 is arranged on the reflection optical path of the polarizer 4, and the total reflection mirror 10 is used for outputting the laser light generated by the laser through the laser output port 14, which is arranged on the box body. The box body is also provided with more than one electrical terminal interface 12 through which the electro-optical switch and the gain pump module are connected to a power supply device.

For lasers, the higher the Q value, the smaller the loss and the higher the efficiency. When the gain pump module starts to pump the laser, the resonant cavity is always in a state of high loss, and the laser cannot establish oscillation in the resonant cavity. When the number of upper energy level inversion particles reaches the maximum, the switch is closed and high voltage is applied. The intracavity loss quickly changes from high loss to low loss, and the laser starts to oscillate in the cavity. Although Q-switching to obtain short pulse devices is simple and small in size, generally only nanosecond or sub-nanosecond short pulses can be obtained, which often limits the application of short-cavity Q-switching processes in picosecond pulse generation. Volume Bragg grating (VBG) has been widely used in stretching and compressing pulse width, especially in picosecond pulses. The invention patent cleverly combines active and passive Q-switching cavity emptying with volume Bragg grating (VBG), uses VBG as the two-end mirror of the resonant cavity, compresses the pulse generated by the saturated absorber multiple times in the cavity, and finally passes through chamber empty output.

When the electro-optical switch 2 is not applied with high voltage, the gain pump module 6 is pumped with current, and the intracavity laser oscillates to generate oscillating light, which is gradually compressed into short pulses under the action of the saturable absorber 5, and the short pulses oscillate and amplify in the cavity , the pulse width gradually shortens with the Q-switching process of the saturable absorber 5 . During the oscillation process, the pulse width is further narrowed by the compression of the volume Bragg grating end mirror 1 and the volume Bragg grating end mirror 9 . Then, it is emptied and output through the electro-optic cavity, that is, at the moment of maximum pulse energy, the electro-optic switch 2 applies high voltage, and the high-energy picosecond laser pulse is output from the polarizer 4, reflected by the total reflection mirror 10, and then from the right side of the box. Output port 14 outputs. In this embodiment, the total reflection mirror is a 45° total reflection mirror, and the pulse first passes through the electro-optic switch 2 once to become circularly polarized light, generating a phase difference of π/2. After reflection by the end mirror 1 of the volume Bragg grating, the circularly polarized light passes through the electro-optic switch 2 again to become linearly polarized light, and a phase difference of π/2 is generated. The polarized light passes through the electro-optic switch 2 twice, and a phase difference of π is generated in total, and its polarization direction is totally deflected by 90°, which is just perpendicular to the polarization direction of the deflector. In this application, while emptying the cavity, a saturable absorber 5 and a volume Bragg grating end mirror are used to compress the pulse multiple times to obtain a pulse width that can be less than 2L/C (L is the length of the laser cavity), breaking through the cavity The limitation of the pulse width is eliminated, so that after the reflection of the polarizer and the 45° total reflection mirror, a high-energy picosecond laser of tens to hundreds of picoseconds is output from the laser output port.

Wherein, the gain pumping module may be continuous pumping or quasi-continuous pumping. When the gain pumping module 6 is continuous pumping, the electro-optic switch 2 determines the frequency of the applied voltage according to the requirement. When the 6 gain pumping modules are quasi-continuous pumping, the frequency of the voltage applied by the electro-optic switch 2 is consistent with the quasi-continuous pumping frequency.

When the laser crystal is strongly pumped by the gain pump module 6, the depolarization caused by the thermally induced birefringence in the laser crystal is stronger than that of the thermal lens, so a quarter-wave plate 8 is also arranged in the optical resonant cavity, and the gain pump The pump module, the concave lens and the quarter-wave plate are arranged in sequence, and the quarter-wave plate is used to compensate the thermal depolarization caused by the thermal effect of the gain pump module. At the same time, a small hole diaphragm is also arranged in the optical resonant cavity, and the small hole diaphragm is arranged between the electro-optic switch and the polarizer; the aperture of the small hole diaphragm is smaller than the size of the laser crystal in the gain pump module, and is used to suppress high-order mode oscillations. Improve beam quality.

The volume Bragg grating end mirror VBG, saturable absorber and gain pump module are placed in the heat sink. The heat sink is a miniature heat sink, which is a device cooled by cooling water or cooling gas. Due to the high energy and high power of the output picosecond laser, the heat dissipation requirements of the laser device are relatively high. Especially the saturated absorber 5 absorbs a lot of laser light and accumulates a lot of heat. If the heat is not dissipated in time, the absorber absorbs heat, and the temperature rises too high and it is easy to break. Volume Bragg grating VBG is greatly affected by temperature, if the absorbed heat cannot be dissipated in time, the effect of pulse width compression will be affected. Therefore, it is necessary to perform cooling and heat dissipation treatment on the above-mentioned devices.

The volume Bragg grating end mirror VBG, polarizer, saturable absorber, concave lens, quarter wave plate, total reflection mirror and laser crystal in the gain pump module are all coated with anti-reflection coating or high Reflective film to enhance the penetration or reflection effect.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (9)

1. a kind of big energy picosecond laser of volume Bragg grating, which is characterized in that including：

Babinet, two parallel volume Bragg grating end mirror VBG are separately positioned on the both ends of the box house, and it is humorous to form optics Shake chamber, and electrooptical switching, polarizer, saturated absorbing body and gain pump module, recessed are disposed in the optical resonance intracavitary Lens；

Total reflective mirror is provided on the reflected light path of the polarizer, the total reflective mirror is used to lead to the laser that the laser generates Laser output output is crossed, the laser output is arranged on the babinet；

More than one electric connection terminal interface is additionally provided on the babinet, the electrooptical switching and gain pump module pass through respectively The connection of wiring end interface is for electric installation.

2. the big energy picosecond laser of volume Bragg grating as described in claim 1, which is characterized in that described body Prague light Grid end mirror VBG, saturated absorbing body and gain pump module be placed on it is heat sink in.

3. the big energy picosecond laser of volume Bragg grating as claimed in claim 2, which is characterized in that described heat sink to be miniature Cooling fin is provided with cooling water circulation pipeline or gas cooling circulating line in miniature cooling fin, is provided on the babinet cold But circulation interface.

4. the big energy picosecond laser of volume Bragg grating as described in claim 1, which is characterized in that the gain pump mould Block is continuous pumping or quasi-cw pumping.

5. the big energy picosecond laser of volume Bragg grating as claimed in claim 4, which is characterized in that the gain pump mould Block is quasi-cw pumping, and the alive frequency of the electrooptical switching institute is consistent with quasi-cw pumping frequency.

6. the big energy picosecond laser of volume Bragg grating as described in claim 1, which is characterized in that the optical resonator Quarter-wave plate is inside additionally provided with, the gain pump module, concavees lens and the quarter-wave plate are set gradually.

7. the big energy picosecond laser of volume Bragg grating as claimed in claim 6, which is characterized in that described body Prague light Laser in grid end mirror VBG, polarizer, saturated absorbing body, concavees lens, quarter-wave plate, total reflective mirror and gain pump module Crystal is plated with the anti-reflection film or highly reflecting films consistent with the wave band of oscillation light.

8. the big energy picosecond laser of volume Bragg grating as described in claim 1, which is characterized in that the optical resonator Aperture is inside additionally provided with, the aperture is arranged between the electrooptical switching and the polarizer；The aperture light Late aperture is less than the size of laser crystal in the gain pump module.

9. the big energy picosecond laser of volume Bragg grating as described in claim 1, which is characterized in that the total reflective mirror is 45 ° of total reflective mirrors.