CN105390929A - All-solid-state laser capable of obtaining single-frequency output at wavelength of 558nm - Google Patents

Abstract

The invention discloses an all-solid-state laser with a single-frequency output of 558nm wavelength, which includes a pumping source system, and the pumping source system includes a laser diode LD, an optical fiber, and a focusing coupling lens system sequentially arranged on the optical path; a Z-shaped The resonant cavity device, the Z-shaped resonant cavity device includes a tail mirror, a concave folding mirror, a yellow light output mirror and a total reflection mirror arranged in sequence in the Z-shaped cavity, and a wave plate and a wave plate are placed between the tail mirror and the concave folding A laser gain medium, a birefringence filter is placed between the concave folding mirror and the yellow light output mirror, and a frequency doubling crystal is placed between the yellow light output mirror and the total reflection mirror. The invention makes full use of the high power density of the fundamental frequency light in the cavity, and adopts the Z-shaped cavity to improve the frequency doubling efficiency, realizes the yellow laser output with single longitudinal mode, low noise, high power and high energy, and successfully solves the problem of Disadvantages of lasers in the prior art.

Description

A 558nm wavelength single-frequency output all-solid-state laser

technical field

The invention belongs to the technical field of lasers, and relates to an all-solid-state single-frequency yellow light laser that obtains a 558nm wavelength output through an intracavity frequency doubling method.

Background technique

The existing laser has the characteristics of monochromaticity, collimation and high brightness, and has a wide range of applications. In particular, lasers in the yellow band have important applications in the medical field. In terms of diagnosis, yellow lasers are ideal for internal total reflection fluorescence imaging systems or flow cytometers or confocal microscopy scanning systems; It can effectively treat diseases such as tinea erythema or capillary or fundus macular degeneration.

Commonly used yellow lasers include Kr ion laser (568nm), dye laser (577nm), copper vapor laser (578nm) and other lasers, but these lasers have inherent shortcomings. Both Kr ion laser and copper vapor laser are gas lasers, which are large in size and consume a lot of power; dye lasers are liquid lasers, and the toxicity of the dye is harmful to the human body, which is not enough to meet the requirements of the instrument. As the research progress and productization of semiconductor lasers gradually mature, optically pumped semiconductor lasers and semiconductor-pumped solid-state lasers have been developed rapidly, with the advantages of good beam quality, small size and long life. But at present, the wavelength of the optically pumped semiconductor yellow laser is relatively limited, and the semiconductor pumped solid-state laser combined with the nonlinear frequency conversion technology makes the yellow broadcasting segment relatively broad.

At present, there have been reports on semiconductor-pumped solid-state yellow lasers at home and abroad. They mainly adopt the following four methods: one is based on the dual-base spectral line oscillation through nonlinear sum frequency (Intracavitysum-frequencydiodeside-pumpedall-solid-stategenerationyellowlaserat589nmwithanoutputpowerof20.5W, "Applied Optics", Vol.52, 2013, 1876-1880), This method has the disadvantages of complex structure, large volume, low efficiency, and large noise. The second is to obtain Stokes light in the 1.1-1.2 μm band based on stimulated Raman scattering, and then obtain it through frequency doubling technology (Self-frequency-doubled BaTeMo2O9Ramanlaser emitting at 589nm, "Optics Express", Vol.21, 2013, 7821-7827); The third is to obtain Stokes light and fundamental frequency light based on stimulated Raman scattering through sum-frequency conversion technology (HighpowerQ-switchedintracavitysum-frequencygenerationandself-Ramanlaserat559nm, "Optics & Laser Technology", 2013, Vol.47, 2013, 43-46), However, Raman lasers have a high threshold and low light-to-light efficiency. Fourth, the base spectrum line based on the 1.1-1.2μm band is directly obtained by frequency doubling technology (Afrequency-doubledNd:YAG/KTPlaserat561nmwithdiodeside-pumping, "LaserPhys", Vol.23, 2013, 5402-5405), this method has a simple structure, However, the single pulse energy and average power are low, and single frequency output cannot be obtained. The yellow light wavelength of 558nm is closer to the sensitive wavelength 555 of the human eye, and is more suitable for retinal coagulation surgery and macular degeneration surgery than other wavelengths. However, the wavelength of 558nm is very difficult to obtain, and the present invention provides an intracavity frequency doubling technique to obtain laser with a wavelength of 558nm.

Contents of the invention

Purpose of the invention: In order to obtain the single-frequency output of 558nm wavelength, the present invention provides a simple in structure, small in size, high in efficiency, and low-noise all-solid-state yellow laser, which can obtain 558nm single-frequency laser output.

Technical solution: The present invention provides an all-solid-state laser with 558nm wavelength single-frequency output, including:

A pumping source system, the pumping source system includes a laser diode LD, an optical fiber and a focusing coupling lens system arranged in sequence on the optical path;

A Z-shaped resonant cavity device, the Z-shaped resonant cavity device includes a tail mirror, a concave folding mirror, a yellow light output mirror and a total reflection mirror arranged in sequence in the Z-shaped cavity, and a A wave plate and a laser gain medium, a birefringence filter is placed between the concave folding mirror and the yellow light output mirror, and a frequency doubling crystal is placed between the yellow light output mirror and the total reflection mirror.

The wave plate includes a first plectrum and a second plectrum sequentially placed before and after the laser gain medium, and both the first plectrum and the second plectrum are quarter-wave plates.

The tail mirror, the first wave plate, the laser gain medium, the second wave plate, the birefringence filter, and the concave folding mirror form the first arm of the Z-shaped cavity; the concave folding mirror and the yellow light output mirror form the second arm of the Z-shaped cavity. Two arms; the yellow light output mirror, the frequency doubling crystal, and the total reflection mirror form the third arm of the Z-shaped cavity.

The length of the first arm of the Z-shaped cavity is 135-145 mm, the length of the second arm of the Z-shaped cavity is 123-133 mm, and the length of the third arm of the Z-shaped cavity is 91-101 mm.

Both sides of the first wave plate and the second wave plate are coated with anti-reflection coatings, their fast axes are perpendicular to each other, and both have an angle of 30°-60° to the polarization direction of the birefringence filter.

The laser gain medium adopts single-end compound growth type Nd:YAG crystal or double-end compound growth type Nd:YAG crystal.

Both the laser gain medium and the frequency doubling crystal are temperature-controlled by a refrigeration device.

The refrigerating device is a circulating water refrigerating device. The laser gain medium and the frequency doubling crystal are placed in a radiator with cooling circulating water, and the heat is conducted to the circulating water through the radiator, and then the heat is carried away by the circulating water.

The rear mirror is a flat mirror, and its surface is coated with an anti-reflection film.

The birefringence filter is made of quartz glass, placed at a Brewster angle of 56°, and its surface is coated with an anti-reflection film.

The frequency doubling crystal adopts lithium triborate or potassium titanyl phosphate.

Working principle: The working process of the 558nm wavelength single-frequency output all-solid-state laser of the present invention is as follows: the pump light emitted by the laser diode LD is transmitted through the optical fiber, and is reshaped and focused by the focusing coupling lens system, and then enters the laser gain medium, and the laser gain medium Through stimulated emission, photons with a central wavelength of 1116nm are generated, and the generated photons are amplified by the feedback of the laser gain medium and the Z-shaped resonant cavity device to generate a standing wave of 1116nm fundamental frequency light with high power density, and at the same time pass through a quarter The wave plate and the birefringence filter eliminate the spatial hole-burning effect of the standing wave of the fundamental frequency light in the cavity, and obtain a single-frequency operation, and then the single-frequency fundamental frequency photons pass through the double-pass frequency doubling of the frequency-doubling crystal to form a 558nm yellow laser and generate it. The yellow light output mirror output.

Beneficial effects: the present invention adopts double-terminal compound growth type Nd:YAG crystal as the gain medium, and designs a Z-shaped torsion cavity that satisfies the dynamic stability of the fundamental mode that is not sensitive to thermal lens effect, and adopts the method of double-pass frequency doubling in the cavity , obtained a single frequency output of 558nm wavelength yellow laser. The invention makes full use of the high power density of the fundamental frequency light in the cavity, and adopts the Z-shaped cavity to improve the frequency doubling efficiency, realizes the yellow laser output with single longitudinal mode, low noise, high power and high energy, and successfully solves the problem of Disadvantages of lasers in the prior art. Compared with the prior art, the length of each arm of the Z-shaped cavity and the radius of curvature of each cavity mirror used in the all-solid-state single-frequency laser with 558nm wavelength output of the present invention can be optimized and selected according to different designs. On the one hand, it can realize The mode change in the laser gain medium and frequency doubling crystal is very small in a wide range, thus greatly reducing the influence of thermal lens effect on laser performance; on the other hand, it can realize a smaller fundamental frequency light spot in the frequency doubling crystal, Thereby achieving higher frequency doubling efficiency. The all-solid-state single-frequency laser with 558nm wavelength output of the present invention has higher output power/energy, and is small in size, good in stability, low in cost and low in noise.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Among them: 1—laser diode LD, 2—optical fiber, 3—focus coupling lens system, 4—tail mirror, 5—first wave plate, 6—laser gain medium, 7—second wave plate, 8—birefringence filter . Cavity second arm, 17—Z cavity third arm.

detailed description

Example 1:

As shown in Figure 1, an all-solid-state laser that obtains a single-frequency output with a wavelength of 558nm includes a pump source system 14, and the pump source system 14 mainly includes a laser diode LD1 and an optical fiber 2 arranged in sequence on an optical path. And a focusing coupling lens system 3, the working mode of the pumping source system 14 is continuous working mode, the maximum continuous pumping power is 50W, and the output center wavelength is 808nm.

The present invention also includes a z-shaped resonant cavity device, which includes a first arm 15 of the z-shaped cavity, a second arm 16 of the z-shaped cavity, and a third arm 17 of the z-shaped cavity. The rear mirror 4 , the first wave plate 5 , the laser gain medium 6 , the second wave plate 7 , the birefringence filter 8 and the concave folding mirror 9 are sequentially arranged in the first arm 15 of the z-shaped cavity. The concave folding mirror 9 and the yellow light output mirror 10 are sequentially arranged in the second arm 16 of the z-shaped cavity. A yellow light output mirror 10 , a frequency doubling crystal 11 and a total reflection mirror 12 are sequentially arranged in the third arm 17 of the Z-shaped cavity.

Further, the bottom surface of the laser gain medium 6 and the frequency doubling crystal 11 are dissipated by the cooling device 13 . The cooling device 13 is a circulating water cooling device. The sides of the laser gain medium 6 and the frequency doubling crystal 11 are respectively wrapped in a copper radiator, and a heat sink is installed at the bottom to connect with the water cooling plate, and the heat is carried away by the cold water circulation.

Preferably, the laser gain medium 6 is a double-terminal compound growth type Nd:YAG crystal with a doping concentration of 1.0at.%, a size of 3×3×10mm ³ , and a non-doped YAG crystal with a length of 2mm at both ends, see The length of the miscellaneous area is 6mm, and the front and rear end faces are coated with anti-reflection coatings for beams with wavelengths of 808nm, 1064nm, 1116nm and 1319nm. The transmittance of 808nm and 1116nm beams is greater than 99.8%, and the transmittance of 808nm and 1319nm beams is greater than 98%. .

Preferably, both sides of the first wave plate 5 and the second wave plate 7 are coated with an anti-reflection coating greater than 95% to 808nm, and the reflectivity of the film to the 1116nm spectral line is greater than 99.8%, and the transmittance to the 1064nm spectral line Greater than 70%, their fast axes are perpendicular to each other and form an angle of 45° with the polarization direction of the birefringence filter 8 .

Preferably, the frequency-doubling crystal 11 is made of lithium triborate (LBO), with a size of 3×3×10mm ³ . Both ends of the crystal are coated with 1116nm and 558nm anti-reflection coatings, and the transmittance is greater than 99.8%. The matching method adopts a type of critical matching , the cutting angle (θ, φ) is (90°, 8°).

Preferably, the birefringent filter 8 is made of quartz glass, placed in the cavity at Brewster's angle (56°), and coated with an anti-reflection film for 1116nm fundamental frequency light, with a transmittance greater than 99.8%.

Preferably, the tail mirror 4 is a plane mirror, and the input surface is coated with a film system with a transmittance greater than 95% to 808nm and a transmittance greater than 70% to the 1064nm spectral line; the output surface is also coated with an anti-reflection coating greater than 95% to the pump light , and the reflectance of the film to the 1116nm spectral line is greater than 99.8%, and the transmittance to the 1064nm spectral line is greater than 70%.

The length of each arm of the Z-shaped cavity adopted in the present invention and the radius of curvature of each cavity mirror can be optimally selected according to different designs.

Preferably, the concave folding mirror 9 has a radius of curvature of 100mm, is coated with a reflective film with a reflectivity greater than 99.8% for the 1116nm spectral line, and greater than 70% for the 1064nm spectral line and 1320nm spectral line.

Preferably, the radius of curvature of the yellow light output mirror 10 is 50 mm, coated with an anti-reflection coating with a transmittance greater than 95% for the 558nm spectral line, and greater than 99.8% for the 1116nm spectral line, and greater than 50% for the 1064nm spectral line. %.

Preferably, the total reflection mirror 12 has a radius of curvature of 50mm, is coated with a reflective film with a reflectivity greater than 99.8% for the 1116nm spectral line and 558nm spectral line, and has a transmittance greater than 50% for the 1064nm spectral line.

Preferably, the length of the first arm 15 of the Z cavity is 140 mm, the length of the second arm 16 of the Z cavity is 128 mm, and the length of the third arm 17 of the Z cavity is 96 mm, with a total length of 364 mm.

Preferably, the core diameter of the optical fiber 2 is 200 μm, and the numerical aperture is 0.22.

Example 2:

Identical substantially with embodiment 1, difference is as follows:

(1) The laser gain medium is a single-ended compound growth type Nd:YAG crystal with a size of 3×3×9mm ³ , in which the front end is a 4mm long non-doped YAG crystal, the length of the doped region is 5mm, and the concentration is 1.lat .%, the front and rear end faces are coated with anti-reflection coatings for beams with wavelengths of 808nm, 1064nm, 1116nm and 1319nm, wherein the transmittance for 1116nm and 1064nm beams is greater than 99.8%, and the transmittance for 808nm and 1319nm beams is greater than 98%.

(2) Frequency doubling crystal 11 is made of potassium titanyl phosphate (KTP), with a size of 3×3×8mm ³ , both ends of the crystal are coated with 1116nm and 558nm anti-reflection coatings, and the transmittance is greater than 99.8%; the matching method adopts a second critical Matching, cutting angle The cutting angle (θ, φ) is (62.8°, 90°).

Claims (11)

1. an all solid laser for 558nm wavelength single-frequency output, is characterized in that, comprising:

One pumping source system (14), described pumping source system (14) be included in light path is settled successively laser diode LD (1), optical fiber (2) and focus on coupled lens system (3);

One Z-type resonator device, described Z-type resonator device is included in tail mirror (4), concave surface refrative mirror (9), gold-tinted outgoing mirror (10) and the total reflective mirror (12) settled successively in Z-type chamber, wave plate and gain medium (6) is placed with between described tail mirror (4) and concave surface refrative mirror (9), be placed with birefringent filter (8) between described concave surface refrative mirror (9) and gold-tinted outgoing mirror (10), between described gold-tinted outgoing mirror (10) and total reflective mirror (12), be placed with frequency-doubling crystal (11).

2. all solid laser of 558nm wavelength single-frequency output according to claim 1, it is characterized in that, described wave plate comprises the first wave plate (5) and the second wave plate (7) that are placed on gain medium (6) front and back successively, and described first wave plate (5) and the second wave plate (7) are quarter-wave plate.

3. all solid laser of 558nm wavelength single-frequency output according to claim 1, it is characterized in that, described tail mirror (4), the first wave plate (5), gain medium (6), the second wave plate (7), birefringent filter (8), concave surface refrative mirror (9) composition Z-type chamber first arm (15); Described concave surface refrative mirror (9), gold-tinted outgoing mirror (10) composition Z-type chamber second arm (16); Described gold-tinted outgoing mirror (10), frequency-doubling crystal (11), total reflective mirror (12) composition Z-type chamber the 3rd arm (17).

4. all solid laser of 558nm wavelength single-frequency output according to claim 3, it is characterized in that, the length of described Z-type chamber first arm (15) is 135 ~ 145mm, the length in Z-type chamber second arm (16) is 123 ~ 133mm, and the length in Z-type chamber the 3rd arm (17) is 91 ~ 101mm.

5. all solid laser of 558nm wavelength single-frequency output according to claim 2, it is characterized in that, described first wave plate (5) and the second wave plate (7) is all two-sided is coated with anti-reflection film, its fast axle is mutually vertical, and all with a folk prescription of birefringent filter (8) to 30 ° of-60 ° of angles.

6. all solid laser of 558nm wavelength single-frequency output according to claim 1, it is characterized in that, described gain medium (6) adopts single-ended composite growth type Nd:YAG crystal or both-end composite growth type Nd:YAG crystal.

7. all solid laser of 558nm wavelength single-frequency output according to claim 1, it is characterized in that, described gain medium (6) and frequency-doubling crystal (11) all carry out temperature control by refrigerating plant (13).

8. all solid laser of 558nm wavelength single-frequency output according to claim 7, it is characterized in that, described refrigerating plant (13) is circulating water refrigerating plant, gain medium (6) and frequency-doubling crystal (11) are positioned over by having in the radiator of cooling circulating water, heat is conducted in recirculated water by radiator, then is carried away by heat by recirculated water.

9. all solid laser of 558nm wavelength single-frequency output according to claim 1, it is characterized in that, described tail mirror (4) is level crossing, and its surface is coated with anti-reflection film.

10. all solid laser of 558nm wavelength single-frequency output according to claim 1, it is characterized in that, described birefringent filter (8) adopts quartz glass, and with Brewster's angle 56 ° placement, its surface is coated with anti-reflection film.

The all solid laser that 11. 558nm wavelength single-frequency according to claim 1 export, it is characterized in that, described frequency-doubling crystal (11) adopts three lithium borates or potassium titanium oxide phosphate.