The difference between laser glass and ordinary optical glass

The difference between laser glass and ordinary optical glass

The main advantages of laser glass compared to laser crystals are:

(1) Easy to prepare. By applying the process technology for preparing optical glass and improving it, it is possible to obtain a highly transparent and optically uniform glass, which is relatively easy to produce a large-sized work substrate material, and has a low cost, and a large volume and a high density of activated particles are used for high power. And important advantages of high energy lasers.

(2) The matrix glass is easy to change. The composition and properties of the matrix glass vary widely, and the types and amounts of activators added are not limited, so it is easy to develop into a series of laser glass varieties with various characteristics.

(3) Easy molding processing. Using optical glass thermoforming and cold working processes, laser glass is easily molded into various shapes, such as rods, sheets, wires, etc., and is ground into high-precision optical surfaces to meet the needs of various device structure developments.

(4) Based on the characteristics of the glass structure, that is, short-range order and remote disorder, the structural defects in the glass have little effect on the properties of the glass and are easy to eliminate, so it is easy to obtain a working substance with uniform properties on the isotropic and large volume. . Since bismuth glass can generate laser light at room temperature, the temperature quenching effect is small, and the quantum efficiency of the optical pump absorption effect string and luminescence is currently the main laser glass.

The laser glass consists of two parts, a matrix glass and an activated ion. The various physicochemical properties of laser glass are mainly determined by the matrix glass, and its spectral properties are mainly determined by the activated ions. However, the matrix glass and the activating ions interact with each other, so the activation ions have a certain influence on the physicochemical properties of the laser glass, and the influence of the matrix glass on its spectral properties is sometimes quite important. As the matrix glass of laser glass, optical glass is mostly used at present, but it is not suitable for any kind of optical glass to be used as laser glass.

What are the basic requirements for laser glass? The following are summarized:

(1) The illuminating mechanism that activates ions must have metastable state to form a three-level or four-energy vertical mechanism; and it is required that the metastable state has a long life, so that the number of particles is easy to accumulate and reverse. In order to make the laser glass have higher efficiency and low oscillation value, the four-level is superior to the three-level in terms of the energy level mechanism. When the energy interval between the final state and the ground state is greater than 1000 cm-1, the final energy level is almost empty at room temperature. Therefore, pumping at room temperature is also prone to particle number inversion. At present, various activated ions of laser light have been generated in the glass, preferably Nd3+ ions, which are four-level mechanisms, and the distance between the final state of the laser transition and the ground state energy level is about 1950 cm.

(2) Laser glass must have a variety of spectral properties. Including the absorption spectrum properties, it is required to have a wide and many absorption bands in the radiant light of the excitation source, a high absorption coefficient, and the absorption band and the peak of the radiation band of the light source overlap as much as possible, which is beneficial to make full use of the excitation light source. Energy; fluorescence spectral properties, generally require that its fluorescence band is small and narrow, so that the output energy is not dispersed; at the same time, in order to convert the absorbed excitation light energy into laser energy as much as possible, the quantum efficiency of fluorescence is required to be as high as possible. The internal energy loss is as small as possible.

(3) The laser matrix glass must have good transparency, especially the absorption of the laser wavelength should be as low as possible. The high transparency of the matrix glass allows the energy of the optical pump to be sufficiently absorbed by the activated ions to be converted into a laser. The reduced transparency increases the absorption of the optical pump energy by the substrate and increases the temperature of the laser glass, which brings a series of disadvantages. At present, the radiation band of the optical pump is mostly located in the visible light and near ultraviolet and infrared regions, so it is necessary to select a material that is transparent in this region. It is preferred to use an oxide and a fluoride glass in the inorganic glass. 3. A matrix metal containing a transition metal element such as iron, copper, lead, manganese, diamond, or nickel. Strong absorption in the near ultraviolet to infrared will reduce the transparency of the matrix glass. The main source of laser wavelength absorption in glass is impurities.

(4) Laser glass must have good optical uniformity. The optical non-uniformity of the laser glass causes the light wave to deform and generate a path difference after passing through the glass, which causes the oscillation threshold to improve the efficiency and the divergence angle to increase.

(5) Laser glass must have good thermal stability. During operation of the laser, the non-radiative transition loss of the activated ions and a portion of the optical energy of the ultraviolet and infrared absorption light pump of the matrix glass are converted into thermal energy that raises the temperature of the glass. At the same time, temperature gradients occur in the radial direction of the rod due to differences in endothermic and cooling conditions. In addition to causing a decrease in the optical uniformity of the laser glass to affect the laser performance, these factors may even cause the laser to be damaged by the poor thermo-mechanical properties of the glass.

(6) Laser glass must have good physical and chemical properties. In addition to the above requirements, in order to facilitate the manufacture, processing and use, laser glass is also required to have good physical properties. This includes a small tendency to devitrification and high chemical stability. Have a certain mechanical strength and good light stability and thermal conductivity. Glass having a high degree of devitrification tends to cause glass production, especially in the production process of bulk glass, and it is difficult to obtain a glass having high optical uniformity.