CN210779491U - An electro-optical Q-switched intracavity frequency-doubling sub-nanosecond pulsed green laser - Google Patents

Abstract

The utility model discloses a sub-nanosecond pulse green laser of frequency multiplication in electro-optic Q-switched cavity, include: the laser comprises a pumping source, a pumping coupling element, a polarization beam splitter prism, a laser gain medium, a lambda/4 wave plate, an electro-optical switch, a fundamental frequency resonant cavity reflector, a harmonic isolation environment, a frequency doubling crystal and a fundamental frequency/frequency doubling resonant cavity reflector. The utility model realizes the output of subnanosecond pulse green laser with high frequency doubling efficiency by a short cavity structure, intracavity frequency doubling and electro-optical Q-switching mode, and can be directly used in occasions needing the subnanosecond pulse green laser; through the mode of intracavity frequency doubling, realize subnanosecond pulse output, have compact structure, efficient, reliable and stable, advantage such as with low costs.

Description

An electro-optical Q-switched intracavity frequency-doubling sub-nanosecond pulsed green laser

technical field

The invention relates to the technical field of lasers, in particular to an electro-optical Q-switched intra-cavity frequency-doubling sub-nanosecond pulsed green laser.

Background technique

Sub-nanosecond pulsed green laser refers to a green laser with a pulse width of less than 1ns. Compared with the traditional Q-switched nanosecond pulsed laser (10-100ns pulse width), it has the advantages of narrow pulse width and high peak power. For nano-processing applications, it can reduce the heat-affected zone of processing and improve processing efficiency; for laser ranging applications, under the same energy, the ranging accuracy of sub-nanosecond pulse width lasers is higher than that of several nanometers and tens of seconds pulse width lasers. The ranging distance can be increased several times to dozens of times. Compared with infrared pulsed lasers, it has the advantages of short wavelength, etc., and has a wide range of applications in laser marine radar, laser fine processing, laser medical treatment, nonlinear optics, etc. Commonly used methods for generating sub-nanosecond pulsed lasers include passively Q-switched microchip lasers, short-cavity electro-optical Q-switched lasers, mode-locked lasers, cavity emptying, SBS compressed pulse width, and electrically modulated semiconductor lasers. The traditional sub-nanosecond pulsed green laser is generally realized by extra-cavity frequency doubling. Since the frequency doubling efficiency is proportional to the peak power density of the fundamental frequency light, in some applications, in order to improve the frequency doubling efficiency, the fundamental frequency and frequency doubling A shaping optical element is added between the devices, so the entire optical path has disadvantages such as complex structure, low light-to-light conversion efficiency, and large size.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide an electro-optical Q-switched intra-cavity frequency-doubling sub-nanosecond pulsed green laser, which can realize high-efficiency and compact sub-nanosecond pulsed green laser output, so as to meet the requirements of laser micromachining, Applications in laser ranging, laser medical treatment, scientific research and other fields.

In order to solve the above technical problems, the present invention provides an electro-optical Q-switched intra-cavity frequency-doubling sub-nanosecond pulsed green laser, including: a pump source, a pump coupling element, a polarization beam splitting prism, a laser gain medium, and a λ/4 wave plate , electro-optic switch, fundamental frequency resonator mirror, harmonic separation, frequency doubling crystal and fundamental frequency/frequency doubling resonator mirror; the pump light emitted by the pump source is focused into the gain medium through the pump coupling element, and the polarization The beam splitter prism, fundamental frequency resonator mirror and fundamental frequency/frequency doubling resonator mirror form an L-shaped folded resonant cavity. The λ/4 wave plate and the electro-optical switch are on one arm of the folded cavity. on the other arm of the resonator.

Preferably, the output mode of the pump source is spatial light output or fiber coupling output, and the pump mode is pulse pumping or continuous pumping.

Preferably, the pump coupling element adopts a single lens or a lens group structure to couple the pump light into the laser gain medium with a certain spot size.

Preferably, the resonant cavity of the laser adopts an L-shaped folded cavity structure, and the polarization beam splitter prism is used as a folded mirror of the resonator cavity. The smooth surface also needs to be coated with a pump light antireflection coating.

Preferably, the laser gain medium is Nd:YVO ₄ crystal, Nd: GdVO ₄ crystal, Nd: YAG crystal, Nd: YLF crystal, which can output a laser crystal with a wavelength of 1 μm.

Preferably, the laser gain medium and the λ/4 wave plate laser electro-optical switch are placed on one arm of the folded cavity, and work together with the polarization beam splitter prism to realize electro-optical Q-switching; the harmonic separation mirror and the frequency doubling crystal are placed on the other arm of the resonant cavity. On the arm, the polarization matching between the polarized output of the fundamental frequency light and the frequency doubling of the frequency doubling crystal is realized to achieve the maximum frequency doubling efficiency.

Preferably, the laser works in an electro-optical Q-switching manner, and the Q-switching manner may be a pressurized electro-optical Q-switching or a decompressed electro-optical Q-switching.

Preferably, the electro-optical switch can be an RTP electro-optic switch, a BBO electro-optic switch, an LGS electro-optic switch, a LN electro-optic switch or a KD*P electro-optic switch.

Preferably, the frequency doubling method adopts intracavity frequency doubling, and the phase matching method of the frequency doubling crystal can be critical phase matching or non-critical phase matching; the output method of frequency doubling light is to insert harmonics between the polarization beam splitter and the frequency doubling crystal. Separation mirror, the incident angle of the harmonic separation mirror is 45° or other angles, which can realize the passage of fundamental frequency light and the output of frequency doubled light; the frequency doubled crystal is LBO crystal, KTP crystal, PPLN crystal, BBO crystal.

The beneficial effects of the invention are as follows: the invention realizes the sub-nanosecond pulsed green light laser output with high frequency doubling efficiency through the short cavity structure, intra-cavity frequency doubling, and electro-optical Q-switching mode, which can be directly used for the sub-nanosecond pulsed green light required. In the case of lasers; the sub-nanosecond pulse output can be realized by means of intracavity frequency doubling, which has the advantages of compact structure, high efficiency, stability and reliability, and low cost.

Description of drawings

FIG. 1 is a schematic diagram of the structure of the laser of the present invention.

Detailed ways

As shown in Figure 1, an electro-optical Q-switched intracavity frequency-doubling sub-nanosecond pulsed green laser includes: a pump source, a pump coupling element, a polarizing beam splitter prism, a laser gain medium, a λ/4 wave plate, and an electro-optic switch , fundamental frequency resonator mirror, harmonic separator, frequency doubling crystal and fundamental frequency/frequency doubling resonator mirror; the pump light emitted by the pump source is focused into the gain medium by the pump coupling element, and the polarization beam splitting prism is connected to the gain medium. The fundamental frequency resonator mirror and the fundamental frequency/frequency doubling resonator mirror form an L-shaped folded resonator. The λ/4 wave plate and the electro-optical switch are on one arm of the folded cavity. The harmonic separator and the frequency doubling crystal are in the resonator. on the other arm.

The laser of the invention is a semiconductor laser end-pumped, pressurized electro-optical Q-switching, the resonance adopts a three-mirror folded cavity structure, and the sub-nanosecond pulsed green light output can be realized by frequency doubling in the cavity.

The pump source 1 is used to generate a laser with a certain spectral line width, and is used to pump the laser gain medium 2. In order to achieve higher conversion efficiency, the output spectral line should match the absorption spectral line of the laser gain medium 2. This embodiment The output mode of the pump source can be a semiconductor laser with spatial light output, or a semiconductor laser with fiber-coupled output, and the pumping mode is continuous pumping or pulse pumping.

The pump coupling element 2 is used to couple the laser light generated by the pump source 1 into the laser gain medium 2 with a specific spot diameter, so as to realize the mode matching between the pump light and the oscillating light in the resonance, which can be a single lens or a lens composed of multiple lenses. The lens surface is coated with an anti-reflection coating for the pump source 1.

The polarizing beam splitter prism 3 mainly plays two roles in the resonance. First, as a folded mirror of the resonant cavity, it plays the role of turning the optical path. Second, as a polarizer in the resonant cavity, the gain medium generates The laser light becomes linearly polarized light. The right-angle surface of the polarizing beam splitting prism in this embodiment is coated with an anti-reflection film for the pump light and the fundamental frequency laser, and the inclined surface is coated with an anti-reflection film for the pump light. The polarizing beam splitter prism 3 may also be a polarizing plate in the form of a dielectric film.

After the laser gain medium 4 absorbs the pump light of the pump source 1, the population inversion is realized. When the gain in the gain medium is greater than the loss of the resonator, the laser oscillation can be established, which is a necessary element for laser generation. In this embodiment, the laser gain medium is Nd:YVO ₄ crystal.

The λ/4 wave plate 5 and the electro-optic switch 6 play the role of polarization conversion in the resonant cavity to realize the Q-switched pulse output. In this embodiment, the laser is a pressurized electro-optical Q-switching, and the fast axis direction of the λ/4 wave plate 5 forms an included angle of 45° with the direction of the linearly polarized light generated by the laser gain medium 4 and the polarizing beam splitter prism 3, which converts the linearly polarized light into circularly polarized light. When the λ/4 voltage is not applied to the electro-optic switch 6, the circularly polarized light is reflected by the fundamental frequency optical resonator mirror 7, and then becomes linearly polarized light after passing through the λ/4 wave plate 5 again. The light is reflected by the polarizing beam splitter prism 3, and the resonant cavity cannot output laser light to achieve the "door-closing" effect; when the electro-optic switch 6 is applied with a λ/4 wave voltage, the resonance achieves the "opening-door" effect, and a Q-switched pulse is output. The electro-optic switch 6 in this embodiment is an RTP electro-optic switch.

The fundamental frequency resonator reflector 7 is mainly a reflector for realizing fundamental frequency light. In this embodiment, the resonator reflector 7 is a 0° reflector, and the surface may be a plane, a concave surface, or a convex surface.

The harmonic separation mirror is 8 mainly to separate the fundamental frequency light and the frequency doubled light. By coating one surface of the reflector with a coating for the fundamental frequency light antireflection and the frequency doubled light reflection, the frequency doubled light is output to the outside of the resonance. In this embodiment, the incident angle of the harmonic separation mirror is 45°.

The frequency-doubling crystal 9 mainly converts the wavelength of the fundamental frequency light into a frequency-doubling green light output through nonlinear frequency conversion. In this embodiment, the frequency-doubling crystal is an LBO crystal.

The fundamental frequency/frequency doubling resonator mirror 10 mainly realizes the simultaneous reflection of the fundamental frequency light and the frequency doubling light. In this way, the fundamental frequency light can be double-pass frequency doubling in the frequency doubling crystal to improve the frequency doubling efficiency. In this embodiment, the fundamental frequency/doubling frequency resonant cavity reflector 10 is a 0° reflector, and the surface may be a plane, a concave, or a convex surface.

Claims (9)

1. An electro-optically Q-switched intracavity frequency doubling subnanosecond pulse green laser is characterized by comprising: the laser comprises a pumping source, a pumping coupling element, a polarization beam splitter prism, a laser gain medium, a lambda/4 wave plate, an electro-optical switch, a fundamental frequency resonant cavity reflector, a harmonic isolation environment, a frequency doubling crystal and a fundamental frequency/frequency doubling resonant cavity reflector; the pump light emitted by the pump source is focused into the gain medium through the pump coupling element, the polarization beam splitter prism, the fundamental frequency resonant cavity reflector and the fundamental frequency/frequency doubling resonant cavity reflector form an L-shaped folded resonant cavity, the lambda/4 wave plate and the electro-optical switch are arranged on one arm of the folded cavity, and the harmonic isolation environment and the frequency doubling crystal are arranged on the other arm of the resonant cavity.

2. The electro-optically Q-switched intracavity frequency doubling sub-nanosecond pulsed green-light laser of claim 1, wherein the pump source output mode is spatial light output or fiber coupled output, and the pump mode is pulsed pump or continuous pump.

3. The electro-optically Q-switched intracavity frequency doubling sub-nanosecond pulsed green laser of claim 1, wherein the pump coupling element is configured as a single lens or a lens assembly to couple the pump light into the laser gain medium at a certain spot size.

4. The electro-optically Q-switched intracavity frequency doubling subnanosecond pulse green laser device as claimed in claim 1, wherein the resonant cavity of the laser device is an L-shaped folded cavity structure, the polarization beam splitter prism is used as a folded mirror of the resonant cavity, the polarization beam splitter prism simultaneously functions as a polarizer and a folded mirror of the resonant cavity in the resonant cavity, and the light-transmitting surface of the polarization beam splitter prism needs to be coated with a pump light antireflection film.

5. The electro-optically Q-switched intracavity frequency-doubling subnanosecond pulse green laser device as claimed in claim 1, wherein the laser gain medium is Nd: YVO₄Crystal, Nd: GdVO₄Crystal, Nd: YAG crystal, Nd: YLF crystal, can output 1 μm wavelength laser crystal.

6. The electro-optically Q-switched intracavity frequency doubling subnanosecond pulse green laser device as claimed in claim 1, wherein the laser gain medium and the λ/4 wave plate laser electro-optical switch are arranged on one arm of the folding cavity, and are cooperated with the polarization beam splitter prism to realize electro-optical Q-switching; the harmonic separation mirror and the frequency doubling crystal are arranged on the other arm of the resonant cavity, so that the polarization matching of the polarization output of the fundamental frequency light and the frequency doubling of the frequency doubling crystal is realized, and the maximum frequency doubling efficiency is realized.

7. The electro-optically Q-switched intracavity frequency doubling subnanosecond pulsed green-light laser as claimed in claim 1, wherein the laser operates in an electro-optically Q-switched mode, the Q-switched mode being a pressurized electro-optical Q-switched mode or a de-pressurized electro-optical Q-switched mode.

8. The electro-optically Q-switched intracavity frequency-doubled sub-nanosecond pulsed green-light laser of claim 1, wherein the electro-optical on-light is an RTP electro-optical switch, a BBO electro-optical switch, an LGS electro-optical switch, an LN electro-optical switch, or a KD x P electro-optical switch.

9. The electro-optic Q-switched intracavity frequency doubling subnanosecond pulse green laser device as claimed in claim 1, wherein the frequency doubling mode is intracavity frequency doubling, and the phase matching mode of the frequency doubling crystal can be critical phase matching or non-critical phase matching; the output mode of the frequency doubling light is that a harmonic separation mirror is inserted between the polarization beam splitter prism and the frequency doubling crystal, the incident angle of the harmonic separation mirror is 45 degrees or other angles, the passing of the fundamental frequency light can be realized, and the frequency doubling light is output; the frequency doubling crystal is LBO crystal, KTP crystal, PPLN crystal, BBO crystal.

Images