CN108321672B - A High Peak Power Holmium Laser System - Google Patents

Abstract

The invention discloses a holmium laser system with high peak power, which comprises a total reflection device, a laser gain medium, a pumping source, a polarizer, an electro-optic Q-switched crystal and an output mirror which are arranged on a light path in sequence, wherein the electro-optic Q-switched crystal is La doped with MgO in a special proportion₃Ga₅SiO₁₄The crystal has the initial material compounding ratio of MgO 3.3-3.9 mol% and La₂O₃＝31.8‑32.1mol％、Ga₂O₃＝53.7‑53.9mol％、SiO₂10.6-10.7 mol%; the invention adopts La doped with MgO with specific proportion₃Ga₅SiO₁₄The crystal is used as an electro-optic Q-switching crystal, and the problem of low optical damage threshold of the existing mid-infrared band electro-optic Q-switching crystal is solved, so that the output of nanosecond holmium laser with high peak power is realized.

Description

A High Peak Power Holmium Laser System

technical field

The invention relates to a holmium laser system, in particular to a holmium laser system with high peak power, which adopts a special electro-optical Q-switched crystal with high damage threshold.

Background technique

Urinary calculi is a common and frequently-occurring disease in urology. The calculi can be found in any part of the kidney, bladder, ureter and urethra. Urinary calculi are prone to obstruction and infection, often accompanied by severe pain symptoms, which bring great pain to patients. .

Holmium laser lithotripsy was first used in intracavitary lithotripsy in 1995. Compared with other intracavitary lithotripsy, it has obvious advantages. For example, holmium laser can crush stones of various compositions and densities, and the one-time lithotripsy rate is high; The stone does not move during lithotripsy, and the generated debris is small, and the date of clearing the stone is also significantly shortened, which reduces the hospitalization time; the endoscope field of view is not disturbed during holmium laser lithotripsy, and the shock wave effect generated is very weak, so it is not possible It will damage the ureteral mucosa; in addition, because the holmium laser can treat polyps at the same time, the curative effect on the stones wrapped by polyps is obviously better than other methods.

At present, the holmium laser lithotripsy devices on the market are all free-running holmium laser systems. The laser output pulse width is in the order of hundreds of microseconds. It is suitable for huge stones, staghorn stones, upper ureter stones and special components. Stones, etc., often appear ineffective. According to the research of E.Duco Jansen et al., the nanosecond-scale Q-switched holmium laser, due to its narrow pulse width and high peak power, has a very significant improvement in the stone crushing efficiency compared with the free-running holmium laser. For huge stones, staghorn stones, stones with special components, etc., the use of Q-switched holmium laser for lithotripsy is very effective, and at the same time, its thermal damage to biological tissues is low, which reduces the side effects of surgery.

However, there are some technical obstacles for the Q-switched holmium laser technology with high peak power and narrow pulse width. For example, in the near-infrared band (1064nm), there is a mature electro-optical Q-switched crystal KD*P with excellent performance, while in the mid-infrared band, there is a lack of crystals with high light damage threshold and good electro-optical performance; The energy level structure, under the operation of high peak power electro-optical Q-switching, the thermal lens effect and thermal depolarization effect will be very obvious, which will not only significantly reduce the laser efficiency and greatly reduce the peak power, but also deteriorate the beam pattern, which is not conducive to its energy level structure. related applications.

SUMMARY OF THE INVENTION

In view of the deficiencies existing in the prior art, as well as the above-mentioned problems or defects, the purpose of the present invention is to provide a holmium laser system with high peak power, which realizes high threshold and high peak power through a highly magnesium-doped lanthanum silicate crystal. holmium laser output.

In order to achieve the above-mentioned technical purpose and achieve the above-mentioned technical effect, the present invention is realized by the following technical solutions, and an all-inversion device, a laser gain medium, a pump source, a polarizer, an electro-optical Q-switching crystal, and an output mirror are sequentially arranged on the optical path;

Wherein, the electro-optical Q-switching crystal is La ₃ Ga ₅ SiO ₁₄ crystal (LGS crystal) doped with MgO, and the raw materials for preparing the electro-optic Q-switching crystal include MgO, La ₂ O ₃ , Ga ₂ O ₃ , SiO ₂ , each of which is The molar percentages of the raw materials are as follows:

Preferably, in the raw materials for preparing the electro-optical Q-switched crystal, the molar ratio of La ₂ O ₃ and SiO ₂ is 3:1.

Preferably, the laser gain medium is a Cr, Tm, Ho: YAG laser rod, and both ends of the laser rod are coated with an anti-reflection film in a wavelength of 2090 nm.

Preferably, the ion doping concentration of the Cr, Tm, Ho:YAG laser rod is as follows:

Cr: 1.3-1.35mol%;

Tm: 5.8-5.85mol%;

Ho: 0.4-0.41 mol%.

Preferably, the pumping source is a xenon lamp containing a Teflon tight-packed cavity, which together can pump the laser gain medium with high efficiency.

Preferably, the polarizer is a sapphire sheet with three layers of parallel equidistant and placed at Brewster's angle with the optical axis.

Preferably, the output mirror is coated with a 2090nm waveband transflective film, and the transflective film has a transmittance of 10%-15% in the 2090nm waveband.

Preferably, the preparation method of the electro-optical Q-switched crystal comprises the following steps:

1) Weigh MgO, La ₂ O ₃ , Ga ₂ O ₃ , SiO ₂ as starting materials according to the prescribed amount, wherein Ga ₂ O ₃ selects 6N grade for use;

2) After fully mixing the starting materials, briquetting them, putting them into a platinum crucible, and calcining them at 900-1200° C. for 10-15 hours to obtain polycrystalline materials by solid-phase reaction;

3) Put the polycrystalline material into the iridium crucible, place the iridium crucible in the corundum crucible, fill the thermal insulation refractory material in the corundum crucible, seal the furnace body, fill with high-purity nitrogen, and add 2%-5% of Oxygen; use radio frequency heating and fully melt, after melting, keep the temperature in the range of 120°C-140°C for 3-5 hours, and then use the pulling method to grow to obtain an electro-optical Q-switched crystal.

The beneficial effects of the present invention are as follows: the present invention adopts the La ₃ Ga ₅ SiO ₁₄ crystal doped with a specific proportion of MgO as the electro-optical Q-switching crystal, which solves the problem of the low light damage threshold of the current mid-infrared band electro-optical Q-switching crystal, thereby achieving a high peak value Power of nanosecond holmium laser output.

Description of drawings

Figure 1 is a schematic diagram of the structure of a holmium laser system with high peak power;

Description of the labels in the figure: 1- total reflection device, 2-laser gain medium, 3-pump source, 4-polarizer, 5-electro-optical Q-switching crystal, 6-output mirror, 7-high reflection film, 8-increase Permeable membrane, 9-semi-reflective semi-permeable membrane, 10-output laser.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement it with reference to the description.

It should be understood that terms such as "having", "comprising" and "including" as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

Fig. 1 shows an implementation form according to the present invention, which includes:

A laser resonator, which includes an all-inversion device 1 with a central axis on the laser light path and an output mirror 6, which is used to select and amplify light with a certain frequency and moving along the axis of the resonator;

Among them, the total reflection device 1 is composed of a total reflection mirror, the mirror surface is coated with a 2090 nm high-reflection film 7, and the output mirror 6 is coated with a semi-transparent and semi-reflective film 9 with a transmittance of 15% in the 2090 nm band. It is possible to output a Q-switched holmium laser with the highest efficiency while keeping the devices in the cavity from being damaged.

The laser gain medium 2 is a Cr, Tm, Ho:YAG laser rod located in the laser resonator, which is used to absorb the 2090nm holmium laser output by the pump light, and its two ends are coated with an antireflection film 8 in the 2090nm band ; The ion doping concentration of the Cr, Tm, Ho:YAG laser rod is Cr: 1.32 mol%, Tm: 5.82 mol%, Ho: 0.4 mol%, under this doping concentration, cross relaxation will occur between adjacent thulium ions Yu ( ³ H ₄ → ³ F ₄ , ³ H ₆ → ³ F ₄ ), one pump source photon can excite two thulium ions to the ³ F ₄ level, which can effectively improve the efficiency of the laser and avoid the Too high will lead to the appearance of ion clusters, so as to obtain high-efficiency holmium laser output.

The pumping source 3 is a xenon lamp containing a Teflon tight-packed cavity, and jointly performs high-efficiency pumping on the laser gain medium 2 .

The polarizer 4 is a sapphire plate with three layers in parallel and equidistant and placed at Brewster's angle with the optical axis.

The electro-optical Q-switched crystal 5 is a La ₃ Ga ₅ SiO ₁₄ crystal doped with a specific proportion of MgO, and the initial ratio of raw materials is: MgO: 3.7 mol%, La ₂ O ₃ : 31.8 mol %, Ga ₂ O ₃ : 53.9 mol %, SiO ₂ : 10.6mol%; when the concentration of MgO doped in LGS crystal is about 3.7mol%, the crystal will be accompanied by lattice relaxation, which will cause the change of the ionic environment and make the physical properties of the crystal change abruptly, especially That is, its light damage threshold will be increased several times, reaching a level comparable to KD*P. At the same time, the high concentration of MgO doped will cause the light transmittance of the LGS crystal to drop rapidly. Therefore, 3.7mol% MgO in the initial raw material can ensure that the LGS crystal has a high light damage threshold and maintains excellent electro-optic performance and light transmittance. Rate. In the original ingredients for growing LGS crystal, if the ratio of Ga ₂ O ₃ is too low, there may be precipitation of LaGaO ₃ or La ₂ Si ₂ O ₇ , which will form new nuclei in the LGS crystal, making it electro-optical The performance is greatly reduced, and appropriately increasing the ratio of Ga ₂ O ₃ can avoid this situation and increase the growth of crystals to a certain extent. Therefore, when the initial ratio of raw materials is MgO: 3.7 mol%, La ₂ O ₃ : 31.8 mol %, Ga ₂ O ₃ : 53.9 mol %, and SiO ₂ : 10.6 mol %, the grown LGS crystal will have excellent performance in the mid-infrared band. The electro-optical Q-switched crystal can provide conditions for realizing high peak power nanosecond holmium laser output.

The electro-optical Q-switching crystal 5 is a La ₃ Ga ₅ SiO ₁₄ crystal doped with a specific proportion of MgO, and its growth method includes the following steps:

1) Using the high-purity MgO, La ₂ O ₃ , Ga ₂ O ₃ and SiO ₂ of the aforementioned proportions as starting materials, wherein Ga ₂ O ₃ adopts 6N grade;

2) After fully mixing the raw materials, briquetting, putting it into a platinum crucible, calcining at 1150 ° C for 15 hours, and obtaining polycrystalline material by solid-phase reaction;

3) Put the above-mentioned polycrystalline material into the iridium crucible, place the iridium crucible in the corundum crucible, fill the thermal insulation refractory material in the corundum crucible, seal the furnace body, fill with high-purity nitrogen, and add 3% oxygen ; Use radio frequency heating and fully melt, after melting, keep at 140 °C for 5 hours, and then use the pulling method to grow to obtain the final La ₃ Ga ₅ SiO ₁₄ crystal doped with a specific proportion of MgO.

In the present invention, the LGS crystal is used as an optical grade for electro-optical Q-switching applications, and requires high optical properties such as optical uniformity of the crystal. The use of Ga ₂ O ₃ with high purity as a raw material can greatly reduce the scattering particles in the crystal. Improve optical performance. In addition, maintaining an oxygen partial pressure of about 3% during the growth and annealing process can obtain a LGS crystal with a relatively transparent color, and can also improve the light damage threshold of the LGS crystal.

Although embodiments of the present invention have been disclosed above, they are not limited to the applications set forth in the specification and embodiments. It can be fully adapted to various fields suitable for the present invention. Additional modifications can readily be implemented by those skilled in the art. Therefore, the invention is not to be limited to the specific details and illustrations herein shown and described, without departing from the general concept defined by the appended claims and the scope of equivalents.

Claims (7)

1. A holmium laser system with high peak power is characterized in that a total reflection device, a laser gain medium, a pumping source, a polarizer, an electro-optic Q-switched crystal and an output mirror are sequentially arranged on a light path;

wherein the electro-optical Q-switching crystal is La doped with MgO₃Ga₅SiO₁₄The raw materials for preparing the electro-optically Q-switched crystal comprise MgO and La₂O₃、Ga₂O₃、SiO₂The molar percentage of the used amount of each raw material is as follows:

the laser gain medium is a Cr, Tm, Ho, YAG laser rod, and antireflection films with the wave band of 2090nm are plated at two ends of the laser rod.

2. The holmium laser system according to claim 1, characterized in that in the raw material for preparing the electro-optical Q-switched crystal, La₂O₃With SiO₂The molar ratio of the two is 3: 1.

3. The holmium laser system according to claim 1, characterized in that the ion doping concentrations of the Cr, Tm, Ho: YAG laser bars are as follows:

Cr： 1.3-1.35mol％；

Tm： 5.8-5.85mol％；

Ho： 0.4-0.41mol％。

4. the holmium laser system according to claim 1, characterized in that the pump source is a xenon lamp containing a teflon compact cavity.

5. The holmium laser system according to claim 1, characterized in that the polarizer is a white gem plate with three layers parallel and equidistant and placed at brewster's angle to the optical axis.

6. The holmium laser system according to claim 1, characterized in that the output mirror is coated with a 2090nm band transflective film having a transmittance of 10% -15% at 2090nm band.

7. The holmium laser system according to claim 1, characterized in that the preparation method of the electro-optical Q-switching crystal comprises the steps of:

1) weighing MgO and La according to the specified dosage₂O₃、Ga₂O₃、SiO₂As a starting material, wherein Ga₂O₃Selecting 6N grade;

2) fully and uniformly mixing the initial raw materials, briquetting, putting into a platinum crucible, calcining at 900-1200 ℃ for 10-15 hours, and obtaining a polycrystalline material by a solid-phase reaction;

3) putting a polycrystalline material into an iridium crucible, putting the iridium crucible into a corundum crucible, filling a heat-insulating refractory material into the corundum crucible, sealing a furnace body, filling high-purity nitrogen, and adding 2-5% of oxygen; heating by radio frequency and melting fully, preserving heat for 3-5 hours at 120-140 ℃ after melting, and then growing by a pulling method to obtain the electro-optic Q-switched crystal.

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