JPH05275783A - Optical waveguide type variable-wavelength laser oscillator - Google Patents

Abstract

PURPOSE:To improve an exciting light density when an exciting light is incident from an end face of an optical waveguide and to enhance a conversion efficiency from the exciting light to an oscillation light by using a titanium-doped sapphire single crystal as a board and forming a channel type or flat surface type optical waveguide on a surface of the board. CONSTITUTION:A titanium-doped sapphire single crystal 1 formed on a surface with a channel type or flat surface type optical waveguide 2 is used as an oscillation medium. A titanium-doped sapphire single crystal 1 is formed in an ordinary plate state. A method for forming the waveguide 2 on the crystal 1 has the steps of forming a mask pattern to become an object shape on the surface of the crystal 2 for forming the waveguide 1, vapor-depositing titanium, heating or electric field-diffusing it while holding the deposited titanium at an oxygen partial pressure sufficient to form titanium oxide from the deposited titanium, and then ion beam etching the masked part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength tunable solid-state laser oscillating device used in the fields of optical measurement using coherent light, optical communication, optical information processing, optical processing and the like. Is.

[0002]

2. Description of the Related Art Conventionally, a semiconductor laser has been known as a laser using an optical waveguide. In addition, non-semiconductors, such as those using a metal oxide laser oscillator,
Known are silica glass fiber lasers containing erbium, phosphate glass lasers containing neodymium, and fiber lasers containing sapphire as a base material containing titanium. However, a substrate using a titanium-doped sapphire single crystal as a substrate is not currently known.

As an excitation light source for laser oscillation of a wavelength-tunable solid-state laser using a titanium-doped sapphire single crystal, a conventional argon laser and a YAG laser by flash lamp excitation have been used. Mainly used are second harmonics, second harmonics of semiconductor laser-excited YLF lasers, copper vapor lasers, and flash lamps. They are,
Since the excitation source is a gas laser or a lamp, there is a drawback that the laser device is inevitably increased in size. Further, the laser device is not only affected by the life of the lamp, but also is not easy to maintain. Further, the laser oscillation efficiency is not necessarily high.

A titanium-doped sapphire single crystal is end-face excited with a second harmonic of a semiconductor laser-excited YLF laser or a semiconductor laser-excited YAG laser. Although methods of performing pulse laser oscillation have been proposed, the output by these methods is as low as several hundred μJ and the oscillation threshold is high. Therefore, it is considered to use a high output semiconductor laser or to use a plurality of semiconductor lasers.

Further, it is not easy to stably obtain single mode oscillation. Furthermore, in the case of a single crystal fiber laser,
The cross-sectional area of the waveguide is relatively large as compared with the optical waveguide formed on the surface of the substrate, and it is difficult to make the diameter of the fiber constant.

[0006]

SUMMARY OF THE INVENTION The present invention provides a wavelength tunable laser oscillating device which is free from the above-mentioned problems, has a high light conversion efficiency, is relatively small and is easy to maintain. The purpose is that.

[0007]

That is, the present invention is directed to a wavelength tunable laser oscillation in which a titanium-doped sapphire single crystal is used as a substrate and a channel-type or planar-type optical waveguide is formed on the substrate surface. It relates to the device. With such a configuration, the excitation light density when the excitation light is incident from the end face of the waveguide can be improved, and the conversion efficiency from the excitation light to the oscillation light can be increased. Furthermore, it was found that a single mode oscillation can be stably obtained by providing a diffraction grating on the upper part of the optical waveguide and returning the light wave. Next, the present invention will be described in detail.

The titanium-added sapphire single crystal used in the present invention is a so-called titanium-doped sapphire single crystal in which titanium is added in an amount of 0.01 to 1 atm%, and its shape is usually plate-like, and its size is 1 mm to 10 mm in thickness. , 2-100m
It is about m × 1 to 10 mm.

The method of forming an optical waveguide in this sapphire single crystal is, for example, as follows. First, a mask pattern having a desired shape is formed on the surface of the sapphire single crystal forming the optical waveguide, titanium is vapor-deposited, and the oxygen partial pressure is kept sufficient to turn the vapor-deposited titanium into titanium oxide (Ti ₂ O ₃ ). However, this is a method in which heating or electric field diffusion is performed, and then the masked portion is subjected to ion beam etching, that is, the refractive index of the waveguide is made higher than that of the substrate.

A method of controlling the oxygen partial pressure to heat the aluminum oxide to release the oxide of aluminum to the outside of the single crystal substrate and perform ion beam etching, that is, to make the refractive index of the waveguide smaller than that of the substrate. There is also a method. Further, for example, helium ions are ion-implanted from the surface of the crystal, and about 0.
This is a method in which a portion having a depth of 5 μm or more is made amorphous and the refractive index of the portion is made smaller than that of the upper crystal layer to form a planar waveguide.

The shape of the optical waveguide formed by such a method varies depending on the purpose of use, but for example, the channel type usually has a width and a thickness of 0.5 to 10 μm. The thickness of the planar waveguide is 0.5 to 10 μm.

A sapphire single crystal substrate having an optical waveguide used in one embodiment of the present invention is shown in FIGS.
In the figure, 1 is a sapphire single crystal and 2 is an optical waveguide.

The method of providing the diffraction grating on the upper portion of the optical waveguide in the present invention includes a light wave interference method, a holographic exposure method,
An electron beam exposure method or the like can be used, and the wavelength changes according to the period of the diffraction grating.

A sapphire single crystal substrate provided with a diffraction grating is shown in FIGS. In the figure, 1 is a sapphire single crystal, 2 is an optical waveguide, and 3 is a diffraction grating.

The structure of the present invention is basically composed of an excitation light source section, a wavelength conversion section, and a laser oscillation section, and is formed by appropriately combining a reflection mirror, a lens, a birefringent filter, a prism, a diffraction grating and the like. To be done. The excitation light source section of the present invention uses, for example, a single semiconductor laser or a plurality of semiconductor lasers, and the emitted excitation light is condensed by a condenser lens or the like and sent to the next wavelength conversion section. The configuration of the wavelength conversion unit includes a wavelength conversion element made of a nonlinear optical crystal, such as KTiOPO ₄ , β-B.
Examples thereof include aB ₂ O ₄ , LiNbO ₃ , and KNbO ₃ .
Further, a solid-state laser crystal to which rare earth ions are added may be interposed between the semiconductor laser and the nonlinear optical crystal. The interposition of the solid-state laser crystal has a favorable effect on the oscillation spectrum, beam spreading characteristics and the like.

The rare earth ion-added solid laser crystal used in the present invention is an oxide or a fluoride containing neodymium, such as neodymium-containing yttrium aluminate, yttrium vanadate, or neodymium-containing lanthanum fluoride. And so on.

Next, an example of the configuration of the present invention will be described with reference to the drawings. FIG. 6 shows an example in which one semiconductor laser is used as the excitation light source. The light (wavelength 0.8 μm) emitted from the excitation light source (4 in the figure) passes through the condenser lens (5 in the figure) and the solid laser crystal (6 in the figure) made of neodymium-added oxide or fluoride Wavelength conversion (wavelength 0.532 to 0.5395 μm) is performed by the conversion element (7 in the figure).
Then, the light that has passed through the ordinary mirror and lens is a titanium-doped sapphire single crystal (containing 0.05 atm% titanium, width 5 mm, length 10 mm, thickness 3 mm) in which a channel type waveguide (width 1 μm) is formed. 8) is incident on and excited by the birefringent filter (10 in the figure) and a reflection mirror (9 in the figure) to oscillate as laser light (wavelength 0.7 to 1.1 μm).

The above example is an example in which a single semiconductor laser is used as an excitation light source, but it is also possible to employ a structure in which a plurality of semiconductor lasers are used as excitation light sources and light is condensed by a condenser lens. Is.

FIG. 7 shows an example using a fiber (11 in the figure), and FIG. 8 shows a diffraction grating (12 in the figure) on the optical waveguide.
It is an example using a titanium-added sapphire single crystal provided with.

[0020]

With the structure of the present invention, the light conversion efficiency is high, and since the device can be made relatively small, maintenance is easy.

[Brief description of drawings]

FIG. 1 is a schematic view of a sapphire single crystal substrate on which a channel type optical waveguide is formed.

FIG. 2 is a sectional view of a sapphire single crystal substrate on which the optical waveguide is formed.

FIG. 3 is a schematic view of a sapphire single crystal substrate on which a flat optical waveguide is formed.

FIG. 4 is a schematic view of a sapphire single crystal substrate provided with a diffraction grating.

FIG. 5 is a side view of a sapphire single crystal substrate provided with a diffraction grating.

FIG. 6 is a block diagram of an example using one semiconductor laser as an excitation light source.

FIG. 7 is a block diagram of an example using an optical fiber.

FIG. 8 is a configuration diagram of an example using a titanium-doped sapphire single crystal in which a diffraction grating is provided on an upper portion of an optical waveguide.

[Explanation of symbols]

 1: Sapphire single crystal 2: Optical waveguide 3: Diffraction grating 4: Excitation light source 5: Condenser lens 6: Solid-state laser 7: Wavelength conversion element 8: Titanium-added sapphire single crystal 9: Reflection mirror 10: Birefringence filter 11: Fiber 12: Diffraction grating

Claims (2)

[Claims] 1. A wavelength tunable laser oscillator using a titanium-doped sapphire single crystal as an oscillation medium, on the surface of which a channel-type or planar-type optical waveguide is formed. 2. A wavelength tunable laser oscillator according to claim 1, wherein a diffraction grating is provided above the optical waveguide.