CN1782145A - Fs laser crystal of ytterbium doped with strontium gadolinium borate - Google Patents

Abstract

The present invention relates to artificial crystal technology, a especially a kind of femtosecond laser crystal of Yb-doped strontium gadolinium borate and its preparation process. The Yb-doped strontium gadolinium borate crystal is prepared through Czochralski method at growth temperature of 1455 deg C, pulling speed of 0.5-2 mm/hr and crystal rotation speed of 15-30 rpm. The said process can grow high quality and large size laser crystal of Yb-doped strontium gadolinium borate.

Description

Femtosecond laser crystal of ytterbium doped strontium gadolinium borate

The invention relates to the field of artificial crystals and crystal growth in the technical field of photoelectron functional materials, in particular to a femtosecond laser crystal material of a working substance in a solid femtosecond laser.

The femtosecond laser crystal in the background technology is a working substance of a solid femtosecond laser, and refers to a luminescent material which takes a crystal as a substrate, absorbs pump light energy through a discrete luminescent center and converts the pump light energy into laser output. Various physical and chemical properties of the femtosecond laser crystal are mainly determined by the host material, and spectral characteristics, fluorescence lifetime, and the like are determined by the energy level structure of the active ion. Since 1965, the pulse laser technology has rapidly developed since the picosecond level pulse is obtained by using a passive mode-locked ruby laser and enters an ultra-short range. In the 70 s, a team collided ring mode-locked dye laser appeared, and the pulse width of the laser entered the femtosecond stage. In the early 90 s, speeches et al at the university of san andelu, uk, first reported that ultrashort pulses of 60fs were generated using a self-mode-locked titanium-sapphire laser. The titanium gem solid laser has wide tunable range, large fluorescence bandwidth, simple structure, high reliability and no pollution, overcomes the defects of a dye laser, and raises the heat tide of developing a novel solid femtosecond laser internationally.

At present, the most widely used solid femtosecond laser crystal is a titanium gem crystal, which has various better physical and chemical properties and is easy to grow high-quality crystal with high optical quality and large size. However, it has the disadvantage of narrow absorption line, and is not suitable for pumping by LD, which will be the development direction of laser pumping source in future.

The active search for a high-quality laser crystal material with excellent physical, chemical and mechanical properties and high optical quality and large size, which is suitable for LD pumping, is currently ongoing work of scientists in various countries. Ytterbium ion is widely used as an active ion, Yb-doped, due to its superior spectral properties³⁺The laser crystal of the ion has high quantum efficiency and is suitable for InGaAs laser diode pumping; borate is also a popular choice for laser-based materials due to its good physicochemical and mechanical properties.

The invention aims to develop a novel laser crystal which is doped with ytterbium, gadolinium and strontium borate [ Yb: Sr ]₃Gd₂(BO₃)₄]The laser crystal material can be directly used as a flash lamp and an LD pump and has higher conversion efficiency.

Sr is added into the grown Yb₃Gd₂(BO₃)₄The crystal was collected on a four-circle diffractometer and structural analysis showed that it belongs to the orthorhombic system, space group Pnma, unit cell parameters a: 8.755 Å, b: 16.04 Å, c: 7.401 Å, and V: 1040 ųAnd Z is 4, and the refractive index is 1.77 by oil immersion. Wherein ytterbium ion is used as doping ion to replace gadoliniumThe lattice position of the ions, the doping concentration of ytterbium is between 0.5at percent and 25at percent, the fluorescence lifetime (tau) is 3.25 to 1.03ms, the fluorescence lifetime is a function of the concentration of ytterbium ions, and ytterbium ions with different concentrations can be doped according to different requirements. The experimental result shows that the laser crystal can output laser with 1063nm wavelength and can be used as a laser crystal.

Yb:Sr₃Gd₂(BO₃)₄The crystal is a molten compound with the same components, can be grown by a pulling method according to a chemical reaction formula: are weighed, mixed and tabletted in the proportions of (D) and (D)₂O₃Then adding the raw materials according to the required concentration, wherein the raw materials are as follows: yb of₂O₃(purity 99.95%, institute of chemistry for Catharanthus roseus application of the department of Chinese medicine), Gd₂O₃(purity 99.99%, institute of applied chemistry of Catharanthus of Chinese academy of sciences), SrCO₃(purity 99.95%, Shanghai chemical reagent Co., Ltd., China pharmaceutical group), H₃BO₃(purity 99.99%, Beijing chemical plant), platinum crucible is used for growth in inert gas (such as N)₂Ar, etc.) under the atmosphere, the parameters of the crystal growth are about 1450-₃Gd₂(BO₃)₄And (4) crystals.

Sr is added into the grown Yb₃Gd₂(BO₃)₄The crystal is analyzed and tested for absorption spectrum, fluorescence spectrum and fluorescence life, and the result shows that (5 at% Yb is doped³⁺Sr of₃Gd₂(BO₃)₄Crystal as an example): yb of Sr₃Gd₂(BO₃)₄The main absorption peak of the crystal is 977nm, the half-peak width is 8nm, and the absorption transition cross section is 1.65X 10^-20cm²The larger half-peak width at 977nm is very suitable for pumping by InGaAs semiconductor laser, which is beneficial to the absorption of laser crystal to pump light and improves the pumping efficiency. Its emission transition cross section sigma at 1063nm_emIs 0.428X 10^-20cm²The fluorescence lifetime is 1.18. mu.s, since crystals with long fluorescence lifetime can be found aboveThe energy level accumulates more particles, increases energy storage and is beneficial to improving the output power and the output energy of the device. Thus, Yb: Sr₃Gd₂(BO₃)₄The crystal can obtain larger output, and is a laser crystal with high conversion efficiency, low cost, high optical quality and practical application prospect and use value.

Yb:Sr₃Gd₂(BO₃)₄The crystal can be very easily grown into a crystal with good quality by a pulling method and the growth speedThe crystal is hard, has good heat-conducting property and excellent optical property, can be easily pumped by a flash lamp and an LD to obtain laser output, has the laser output wavelength of 1063nm, and can be used as a better laser crystal.

Yb: Sr of the invention₃Gd₂(BO₃)₄The crystal is a molten compound with the same components, can be grown by adopting a pulling method, has short growth period and can obtain high-quality large-size crystals. In the experimental process, a proper solid-phase synthesis method and a better growth condition are found, and crystals with high optical quality and the size of phi 10mm multiplied by 22mm are grown by adopting a pulling method.

Detailed Description

Example 1: czochralski method for growing Yb with doping concentration of 2.0 at%³⁺Yb of (1)₃Gd₂(BO₃)₄And (3) laser crystals.

Accurately weighing SrCO according to the proportion₃、Gd₂O₃、H₃BO₃、Yb₂O₃Mixing, grinding, tabletting, and adding 60 × 40mm³The platinum crucible of (2) was subjected to a solid-phase reaction in a muffle furnace at 900 ℃ for 12 hours, and then heated to 1100 ℃ for 10 hours. Putting the synthesized sample into a pulling furnace, and adopting a pulling method in N₂In the atmosphere, under the conditions of 1455 ℃ of growth temperature, 15rmp of crystal rotation speed and 1mm/h of pulling speed, high-quality Yb with the size of phi 15mm multiplied by 26mm is grown³⁺2.0 at.% of Yb to Sr₃Gd₂(BO₃)₄And (4) crystals.

Example 2: czochralski method for growing Yb with a doping concentration of 5.0 at%³⁺Yb of (1)₃Gd₂(BO₃)₄And (3) laser crystals.

Accurately weighing SrCO according to the proportion₃、Gd₂O₃、H₃BO₃、Yb₂O₃Mixing, grinding, tabletting, and adding 60 × 40mm³The platinum crucible of (2) was subjected to solid-phase reaction in a muffle furnace at 1050 ℃ for 10 hours, and then heated to 1200 ℃ for 20 hours. Putting the synthesized sample into a pulling furnace, and growing high-quality Yb with the size of phi 10mm multiplied by 22mm by adopting a pulling method under the conditions that the growth temperature is 1465 ℃, the crystal rotating speed is 15rmp and the pulling speed is 0.5mm/h in Ar atmosphere³⁺5.0 at.% of Yb to Sr₃Gd₂(BO₃)₄And (4) crystals.

Claims (4)

1. An ytterbium-doped gadolinium strontium borate femtosecond laser crystal is characterized in that: the molecular formula of the crystal is Yb: Sr₃Gd₂(BO₃)₄Belongs to an orthorhombic system, the space group is Pnma, the unit cell parameters are a-8.755 Å, b-16.04 Å, c-7.401 Å and V-1040 ųZ is 4, the refractive index is 1.77, ytterbium ions are used as doping ions to replace the lattice position of gadolinium ions, and the doping concentration of ytterbium is between 0.5 at% and 25 at%.

2. A method for producing a crystal according to claim 1, characterized in that: the crystal is grown by adopting a pulling method, the growth temperature of the crystal is 1450-.

3. Use of a crystal according to claim 1, characterized in that: the crystal is used as a laser working substance in a solid femtosecond laser, and a flash lamp or a laser diode is used as a pumping source to excite and generate laser output with 1063nm wavelength.

4. Use of a crystal according to claim 1, characterized in that: the solid femtosecond laser made of the crystal is used in the fields of informatics, biomedicine and ultrafast science.