Chromium-doped lithium magnesium tungstate crystal and its preparation and application

Abstract

The invention discloses a chromium-doped lithium tungstate magnesium crystal as well as a preparation method and an application thereof. The molecular formula of the crystal is Cr3+:Li2Mg2(WO4)3, the crystal belongs to an orthorhombic crystal system and a Pnma space group, and the cell parameter is as follows: Z=4. The crystal grows in a top seeded solvent growth method, the mixture of 75% Li2WO4 and 25% WO3 is used as a fluxing agent, the concentration ratio of the fluxing agent in the growth raw material is 55 to 80 percent, and the growth parameters are as follows: the cooling rate is 0.5 to 5 DEG C / day, the growth temperature is 800 to 880 DEG C, and the rotation speed is 5 to 30 turns / min. The crystal has the characteristics such as moderate mechanical performance, large transmission cross section and the like, the tunable range is 750nm to 1050nm, and the crystal is expected to become a novel tunable laser crystal and can be actually used.

Description

technical field [0001] The invention relates to the technical field of optoelectronic functional materials, in particular to a laser crystal material used as a working substance in a tunable solid-state laser. Background technique [0002] Tunable laser refers to: the pump light excites the active ions in the laser working medium to generate laser. The laser emission peak is a wave packet with a relatively wide wavelength range, or has multiple emission peaks in a certain wavelength range. On this basis, prism tuning method, F-P etalon tuning method, grating tuning method, optical filter tuning method and distributed feedback system tuning method are used to obtain laser output with adjustable wavelength within a certain range. [0003] Since 1963, L.F.Johnson et al. have used flash lamp pumping, in doped Ni 2+ MgF 2 Since the first solid-state tunable laser operation was realized in a crystal (L.F.Johnson, R.E.Dietz and H.J.Guggenheim, J.Phys.Rev.Lett., 11 (1963) 318), sc...

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Problems solved by technology

[0003] Since 1963, L.F.Johnson et al. have used flash lamp pumping, in doped Ni 2+ MgF 2 Since the first solid-state tunable laser operation was realized in a crystal (L.F.Johnson, R.E.Dietz and H.J.Guggenheim, J.Phys.Rev.Lett., 11 (1963) 318), scientists have discovered many solid-state tunable laser crystals, Such as Ti 3+ :Al 2 o 3 、Cr 3+ : Mg 2 SiO 4 、Cr 3+ : LiSrAlF 6 、Cr 3+ : BeAl 2 o 4 etc., but due to various reasons, most tunable laser crystals are limited to laboratory use and cannot be promoted to industrial applications

The solid-state tunable laser crystal that has been studied the most and has entered the application field is Cr 3+ : BeAl 2 o 4 (Alexandrite), Ti 3+ :Al 2 o 3 (titanium-doped sapphire) and Cr 3+ : LiCaAlF 6 、Cr 3+ : LiSrAlF 6 , but they also have some unavoidable defects that limit their application range

Such as: Cr 3+ : BeAl 2 o 4 The main disadvantages of (Alexandrite) crystals are: the tuning range is small, between 700 and 800nm, and the emission cross section is small (6×10 -21 cm 2 ), high pumping threshold, high damage rate and high thermal lens effect, etc. In addition, due to the high toxicity of BeO, it also brings great difficulties to the growth

Ti 3+ :Al 2 o 3 The main disadvantage of the crystal is: the Ti in the crystal 3+ -Ti 4+ The appearance of ion pairs causes absorption in the laser output band, that is, the near-infrared band, which affects its laser performance, and because of its short lifetime of the upper energy level of the laser (only 3.2μs), it is necessary to use short pulse lasers, Q-switched lasers, continuous Pumping with a wave laser or a flash lamp that produces particularly short pulses further limits its applications.

Cr 3+ : LiCaAlF 6 、Cr 3+ : LiSrAlF 6 Crystals have problems such as small absorption coefficient and low laser efficiency pumped by laser diodes (LDs).

[0004] Considering various comprehensive factors used in the use of solid-state tunable laser crystals, there is currently no crystal that can well meet people's needs