DE2723642A1 - Waveguide laser using layer of neodymium aluminium borate - on substrate of gadolinium-lanthanum-aluminium borate - Google Patents

Abstract

Device using a laser-active, waveguide layer (b) on a substrate (a) which has a lower refractive index than layer (b). The substrate (a) consists of Gd1-xLaxAl3(BO3)4, where x is below 1 and pref. 0.485 plus-or-minus 0.1; and layer (b) is NdAl3(BO3)4. The substrate (a) is pref. made via a Pt crucible contg. a bath (c) of KiSO4 and MoO3 in molar ratio 1:3. Bath (c) is heated to 1000-1200 degrees C, and Gd2O3, La2O3, Al2O3, and an excess of B2O3 are dissolved in the bath (c). The bath is then slowly cooled, esp. at ca. 1 degrees K/h to 900 degrees C, with the addn. of seed crystals shortly before satn. is reached. At 900 degrees C the bath is decanted from the crystals. A similar bath (c) is employed to form layer (b) by dissolving Nd2O3, Al2O3 and B2O3 in the bath (c). Substrate crystals (a) are then immersed in the bath for epitaxial growth of layer (b). Used e.g. as waveguide lasers forming a light source or light amplifier in optical integrated circuits. The lasers (a,b) can be economically made by planar technology and are compatible with light emitting diodes.

Description

Epitaxial laser-active layer made of NdAl3 (B03) 4 on a sub-

strat from Gd0.51 5La0.485Al3 (B03) 4.

The invention relates to an arrangement with a wave-guiding, laser-active one Epitaxial layer on a substrate.

Such layers serve, for example, as waveguide lasers, these lasers can be easily integrated as light sources or light amplifiers in optical circuits. With solid-state lasers it is necessary that the laser-active material as a thin layer or as a thin strip on a lower refractive index substrate can.

Such waveguide lasers have the advantage that they like optical circuits can be manufactured inexpensively in planar technology. Furthermore, waveguide lasers are geometrically very well adapted to light-emitting diodes, how to install them as optical pumps.

One already knows waveguide lasers made of Y3Al5012, which with 1.5 % Neodymium is doped. This laser material has due to the low neodymium concentration the principal disadvantage of a small absorption coefficient for the pump wavelength of 800 nm, resulting in a large overall length of more than 1 cm, as well as a low light amplification.

One already knows from stoichiometric neodymium laser substances Lasers can miniaturize these substances to lengths of the order of 1 mm.

From the publication L.R. Chinn, H.Y. P. Hong, Optics Comm., Vol. 15, no. 3 (1975) is neodymium aluminum borate (NAB) with the chemical composition NdAl3 (B03) 4 is known as a laser material.

This material has excellent spectral laser properties a high light gain and an unlimited service life. Also shows NAB no ferroelastic twin domains, such as those in neodymium pentaphosphate, also a stoichiometric neodymium laser material can occur. aside from that Compared to the laser material mentioned last, NAB has a 40% higher neodymium concentration, i.e. lasers from NAB can be miniaturized even further, and NAB is a electro-optical material, i.e. it can be modulated directly.

The mentioned publication also describes the production of NAB single crystals specified. Waveguide lasers made from this material have not been known until now no suitable substrate was found.

The object of the invention is the production of waveguide lasers from NAB to enable.

This task is achieved by a device of the type mentioned at the beginning solved, which according to the invention the features of the characterizing part of claim 1 has.

The substrate for the NAB waveguide laser according to the invention is gadolinium-lanthanum-aluminum-borate provided, i.e. Gd1 xLaxA13 (BO; where x lies between the values 0 and 1.

According to a preferred embodiment of the invention, x has the value 0.485, i.e. Gd0.515La0.485Al3 (B03) 4 is used as the substrate.

The laser-active NAB material can advantageously by epitaxy be applied to the substrate. This method of manufacture offers compared to others Methods have the advantage that the laser-active material is deposited in monocrystalline form, so that the favorable laser properties of the solid material also in the S seal form remain. In the laser-active NAB layer remain the attenuation for the laser wavelength and the line broadening as with the solid material very low.

In particular, the following are applicable to the substrate material according to the invention Advantages attributed to: The lattice adaptation between the substrate material and the laser-active NAB layer material is used to produce epitaxial layers with high quality very suitable. In the preferred embodiment of the invention, i.e. x has the value 0.485, there is the difference between the corresponding grid spacings between substrate and laser layer material for the most unfavorable direction at only 0.2%, so that lattice disorder and stress in the layer system remain low.

Since the substrate material has a chemically similar compound to the Laser layer material occurs during the epitaxial deposition of the laser-active Sdtchtmaterials no undesirable chemical reactions between the substrate material and the substances of the epitaxial bath, i.e. the substrate is for the epitaxial process chemically stable.

The refractive index of the substrate material is smaller than the refractive index the laser-active layer.

The substrate does not contain any fluorescence-quenching ions that would Would reduce light gain. Especially in very thin laser-active layers a reduction in the gain factor could occur due to fluorescence quenching, because the laser-active layer, the light energy is partially lost in that by fluorescence-quenching ions lying in the vicinity of the laser-active layer of the substrate is recorded.

The substrate material itself shows in the range of the laser wavelength no interfering absorption, such absorption by the substrate would reduce the gain factor also reduce the laser-active layer, since the electromagnetic field of the in the laser-active layer guided light falling exponentially into the substrate reaches in.

The following describes the manufacture of an NAB waveguide laser a substrate made of gadolinium-lanthanum-aluminum-borate of the chemical composition Gdo 4ssA1: (.B03) 4 described.

A process can be used as the starting point for the production of the substrate as it is in the publication H.P.Y. Hong, K. Dwight, Mat. Res. Bull. 9 (1974) 1661 - 1666 for the cultivation of NAB crystals is described. This in the pamphlet However, the method described is used for growing larger substrate crystals modified: K2S04 and MoO3 are used in a molar ratio of 1: 3 as a bath in a platinum crucible used. In this bath, the rare earth oxides Gd2O3 and La203, Al203 and a Excess 3203 in a molar ratio of 1: 3: 6 at 1000 to 12000 ° C. Then the Bath solution slowly oversaturated by cooling, cooling takes place with a decrease in temperature of about 1 0K per hour. For the production of substrate crystals with several Seed crystals become mm in size at a point in time shortly before reaching saturation equilibrium immersed in the melt. This point in time must be determined through experiments. As soon as the bath solution has been cooled to about 9000C, the further cooling is carried out the bath solution is accelerated to room temperature, e.g. to approx. 100K / h.

Then the substrate crystals are dissolved out of the solidified bath, e.g. by hot, diluted soda lye.

It is advantageous to have a perforated plate inside the platinum crucible in the bathroom so that it is possible to remove the substrate crystals from the bath at approx. 9000C separate from the crystals, e.g. by decanting the bath. After that, the Crystals cooled to room temperature at approx. 100 K / h. That way it becomes Time-consuming dissolving of the substrate crystals from the solidified bath avoided.

On the substrate crystals produced in this way, laser-active NAB layers grow epitaxially. To do this, a similar procedure is used, such as described above, used: In this case, Nd203, Al203 and B203 are dissolved in the bath. If the substrate crystals are brought into this bath solution, the layer growth takes place the laser-active layer with about 10 to 50 / um / h.

This means that there is a laser-active NAB layer on a substrate made of gadolinium-lanthanum-aluminum-borate been applied. To make a waveguide laser, all you have to do now is resonator mirrors or resonator grids are provided in a known manner.

An incoherent light source is attached for optical pumping, preferably light emitting diodes. With such light sources, the laser-active layer be pumped transversely or longitudinally.

7 claims

Claims (7)

Patent claims arrangement with a laser-active, wave-guiding Layer on a substrate, which has a lower refractive index than the laser-active layer is indicated by the fact that the substrate is made of gadolinium-lanthanum-aluminum-borate Gd1-xLaxAl3 (BO3) with 0 <x <1, and that the laser-active layer consists of Neodymium aluminum borate NdAl3 (BO3) 4. 2. Arrangement according to claim 1, characterized in that the substrate has a composition in the range x - 0.485 + 0.1. 3. A method for producing an arrangement according to one of the claims 1 and 2, characterized in that for substrate production K2S04 and MoO3 in a molar ratio 1: 3 in a platinum crucible can be used as a bath that in this bath at 1000 to 12000C Gd203, La203, Al203 and an excess of B203 are dissolved that then the bath solution is slowly cooled to about 900 ° C, and that shortly before reaching the saturation equilibrium Seed crystals are entered into the bath solution. 4. The method according to claim 3, characterized in that in the bath the rare earth oxides Gd203 and La203 ,. A1203 and B203 in a molar ratio of 1: 3: 6 = rare earth oxides : Al203: B203 are solved. 5. The method according to any one of claims 3 and 4, characterized in that that at about 900 ° C the bath is decanted from the crystals formed. 6. The method according to any one of claims 3 to 5, characterized in that that the cooling to approx. 9000C takes place at a speed of approx. 1K / h. 7. A method for producing an arrangement according to one of the claims 1 and 2, characterized in that for the production of the laser-active NAB layer Substrate crystals are placed in a bath of K2SOi and MoO3 in a molar ratio of 1: 3 be, being in this Bad Nd203, A1203 and B203 are resolved, and that the laser-active NAB layers are formed by epitaxy.