WO2003076972A1

WO2003076972A1 - Top-pumped optical device

Info

Publication number: WO2003076972A1
Application number: PCT/KR2003/000491
Authority: WO
Inventors: Jung-Hoon Shin; Nam-Kyoo Park
Original assignee: Luxpert Technologies Co., Ltd.
Priority date: 2002-03-13
Filing date: 2003-03-13
Publication date: 2003-09-18
Also published as: KR20030073727A; KR100442066B1

Abstract

Disclosed is a top-pumped optical device which can efficiently transfer pumping light from a pumping light source toward a gain medium structure. The major characteristic of the present invention is that the top-pumped optical device has a light guiding structure such as a light pipe or an ellipsoidal reflector. According to the present invention, the pumping efficiency of the top-pumped optical device can be enhanced remarkably.

Description

TOP-PUMPED OPTICAL DEVICE

Technical Field

The present invention relates to a top-pumped optical device, and more particularly to an optical device provided with a light guiding structure which can efficiently transfer pumping light from a pumping light source toward a gain medium structure in order to enhance -its pumping efficiency.

Background Art

Generally, in PLCs (Planar Lightwave Circuits) providing a gain by optical pumping, a laser has been mainly used as a pumping light source. The PLCs employ an end-fire method in which light irradiated from the pumping light source is coupled with an optical multiplexer of a gain medium structure of the PLCs by an optical fiber. The laser is expensive, and the PLCs are difficult to be integrated using the end-fire method. Accordingly, in order to solve these problems, a low- cost LED light source is used as a pumping light source. Recently, there is proposed a top-pumping arrangement in which light irradiated from the pumping light source is directed downward onto the gain medium structure disposed below the pumping light source. In the end-fire method, the light from the pumping light source is transferred along an optical waveguide, thus being capable of being coupled with all of the gain medium structures. On the other hand, in the recently developed top-pumping arrangement, the light from the pumping light source is perpendicularly incident onto the optical waveguide. In this case, when the pumping light is not guided into all of the gain medium structures, the actual power of the pumping light may be smaller than the theoretical power of the pumping light from the pumping light source, thus reducing excitation efficiency.

Disclosure of the Invention

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a top-pumped optical device, in which pumping light from a pumping light source can be efficiently transferred to a gain medium structure.

In accordance with a first aspect of the present invention, the above and other objects can be accomplished by the provision of a top-pumped optical device comprising: a substrate; a lower cladding layer formed on the substrate; a gain medium structure formed on the lower cladding layer and excited by absorbing pumping light; a light source disposed above the gain medium structure for pumping the gain medium structure by means of light directed downward therefrom; and a light pipe having a light input plane at its one surface facing the light source and a light output plane at its opposite surface facing the gain medium structure, and serving as a guide for transferring the light from the light source to the gain medium structure.

Preferably, the light pipe may be formed to have an upright column shape. More preferably, the light pipe may be formed to have a circular cylinder shape or a polyhedral column shape, in case that the size of the light source is larger than that of the gain medium structure.

Further, preferably, the light pipe may be hollow or solid. In case that the light pipe is hollow, an optical reflective surface may be formed on an internal surface of the light pipe. In case that the light pipe is solid, the light pipe may be preferably one selected from materials with a refractive index higher than that of the external substance of the light pipe, and provided with an optically reflective surface on its external surface, so that the light from the light source is transferred to the gain medium structure by total internal reflection and reflection at the reflective external surface of the light pipe.

Moreover, preferably, the top-pumped optical device may further comprise an upper cladding layer formed on the gain medium structure. In this case, the upper cladding layer may be made of a material which can transmit the light irradiated from the light source. In accordance with a second aspect of the present invention, there is provided a top-pumped optical device comprising: a substrate; a lower cladding layer formed on the substrate; a gain medium structure formed on the lower cladding layer and excited by absorbing pumping light; a light source disposed above the gain medium structure for pumping the gain medium structure by means of light directed downward therefrom; and an ellipsoidal reflector for surrounding the light source, provided with first and second foci and partially opened at a portion including the second focus, wherein the light source is disposed at the first focus of the ellipsoidal reflector, and the gain medium structure is disposed at the second focus of the ellipsoidal reflector. Further, preferably, the ellipsoidal reflector may be hollow or solid. In case that the ellipsoidal reflector is hollow, an optical reflective surface may be formed on an internal surface of the ellipsoidal reflector. In case that the ellipsoidal reflector is solid, the ellipsoidal reflector may be preferably one selected from materials with a refractive index higher than that of the external substance of the ellipsoidal reflector, and provided with an optical reflective surface on its external surface, so that the light from the light source is transferred to the gain medium structure by total internal reflection and reflection at the reflective external surface of the ellipsoidal reflector.

Brief Description of the Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a schematic cross-sectional view of a top-pumped optical waveguide amplifier in accordance with a first embodiment of the present invention; and

Fig. 2 is a schematic cross-sectional view of a top-pumped optical waveguide amplifier in accordance with a second embodiment of the present invention.

Best Mode for Carrying Out the Invention

Now, with reference to accompanying drawings, preferred embodiments of the present invention are described in detail. The preferred embodiments of the present invention illustrate top-pumped optical waveguide amplifiers, respectively.

[First Embodiment] Fig. 1 is a schematic cross-sectional view of a top-pumped optical waveguide amplifier in accordance with a first embodiment of the present invention. With reference to Fig. 1, a lower cladding layer 110 made of silica is formed on a substrate 100, and a core layer made of a silica-based substance doped with nano-crystals and rare-earth elements is formed on the lower cladding layer

110. Here, the core layer serves as a waveguide 120. An upper cladding layer 130 made of silica is formed on the waveguide 120. The upper cladding layer 130 is made of a material which can transmit pumping light irradiated from a LED pumping light source 150 so that the pumping light reaches the waveguide 120. A light pipe 140 is interposed between the LED light source 150 and the upper cladding layer 130. The light pipe 140 formed to have a conical shape is made of glass and coated with a reflective material, and serves to allow the pumping light from the LED light source 150 to be absorbed into the waveguide 120 by total internal reflection and reflection at the external surface of the light pipe 140 without loss. Although the light pipe 140 in this embodiment of the present invention is formed to have the conical shape, the shape of the light pipe 140 is not limited thereto, but may be an upright column, more particularly an upright circular cylinder or polyhedral column. Further, although the light pipe 140 in this embodiment of the present invention, which is made of glass with refractive index higher than that of external air and has the reflective external surface by the coating, guides the pumping light from the LED light source 150 into the waveguide 120 by the total internal reflection and the reflection at the reflective external surface of the light pipe 140, the light pipe 140 may be a hollow pipe so that an optical reflective surface is formed along the inner wall of the hollow pipe.

[Second Embodiment]

Fig. 2 is a schematic cross-sectional view of a top-pumped optical waveguide amplifier in accordance with a second embodiment of the present invention. Components in Fig. 2, which are substantially the same as those in Fig. 1, are denoted by the same reference numerals, and detailed descriptions thereof will thus be omitted because they are considered to be unnecessary.

With reference to Fig. 2, in the same manner as that of Fig. 1 , the lower cladding layer 1 10, the waveguide 120, and the upper cladding layer 130 are subsequently formed on the substrate 100. The LED light source 150 is surrounded by a partially-opened ellipsoidal reflector 142. The LED light source 150 is disposed at a location of a first focus in the ellipsoidal reflector 142, and the waveguide 120 is disposed at a location of a second focus in the opened region of the ellipsoidal reflector 142. Theoretically, the ellipsoidal reflector 142 is provided with the above-described two focuses. The LED light source 150 disposed at the location of the first focus of the ellipsoidal reflector 142 irradiates light. The light is reflected by the outer wall of the ellipsoidal reflector 142, and thus concentrated on the waveguide 120 disposed at the second focus. The ellipsoidal reflector 142 is made of a solid glass member, and the outer surface of the ellipsoidal reflector 142 is coated with a reflective material so that an optical reflective surface is formed on the outer surface of the ellipsoidal reflector 142.

The ellipsoidal reflector 142 is selected from one of materials with refractive index higher than that of an external substance, so that the light from the LED light source 150 is transferred to the gain medium structure by total internal reflection and reflection at the external surface of the ellipsoidal reflector 142. In case that the ellipsoidal reflector 142, as described above, is solid, the LED light source 150 is inserted and fixed into the ellipsoidal reflector 142. In case that the ellipsoidal reflector 142 is hollow, it is preferable to form an optical reflective surface onto the inner wall of the hollow ellipsoidal reflector. In this case, it is well known to those skilled in the art that a supporter (not shown) for supporting the LED light source 150 at the location of the first focus is required.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. That is, the top-pumped optical device achieved by the present invention is not used only in a waveguide amplifier, but also may be used in a passive PIC (Photonic Integrated Circuit) operated by gain obtained by the optical pumping, such as an optical splitter, an optical demultiplexer, an optical multiplexer, or an AWG (Arrayed Waveguide Grating).

Industrial Applicability

As apparent from the above description, the present invention provides a top-pumped optical device, in which pumping light from a pumping light source can be efficiently transferred to a gain medium structure in order to enhance its pumping efficiency.

Claims

Claims:

1. A top-pumped optical device comprising: a substrate; a lower cladding layer formed on the substrate; a gain medium structure formed on the lower cladding layer and excited by absorbing pumping light; a light source disposed above the gain medium structure for pumping the gain medium structure by means of light directed downward therefrom; and a light pipe having a light input plane at its one surface facing the light source and a light output plane at its opposite surface facing the gain medium structure, and serving as a guide for transferring the light from the light source to the gain medium structure.

2. The top-pumped optical device as set forth in claim 1, wherein the light pipe is formed to have an upright column shape.

3. The top-pumped optical device as set forth in claim 1 , wherein the light pipe is formed to have a circular cylinder shape or a polyhedral column shape, in case that the size of the light source is larger than that of the gain medium structure.

4. The top-pumped optical device as set forth in claim 1 , wherein the light pipe is hollow, and an optical reflective surface is formed on an internal surface of the light pipe.

5. The top-pumped optical device as set forth in claim 1, wherein the light pipe is solid, has refractive index higher than that of external substance of the light pipe, and provided with an optical reflective surface on its external surface so that the light from the light source is transferred to the gain medium structure by total internal reflection and reflection at the reflective external surface of the light pipe.

6. The top-pumped optical device as set forth in claim 1, further comprising an upper cladding layer formed on the gain medium structure, wherein the upper cladding layer is made of a material which can transmit the light irradiated from the light source.

7. A top-pumped optical device comprising: a substrate; a lower cladding layer formed on the substrate; a gain medium structure formed on the lower cladding layer and excited by absorbing pumping light; a light source disposed above the gain medium structure for pumping the gain medium structure by means of light directed downward therefrom; and an ellipsoidal reflector for surrounding the light source, provided with first and second foci and partially opened at a portion including the second focus, wherein the light source is disposed at the first focus of the ellipsoidal reflector, and the gain medium structure is disposed at the second focus of the ellipsoidal reflector.

8. The top-pumped optical device as set forth in claim 7, wherein the ellipsoidal reflector is hollow, and an optical reflective surface is formed on an internal surface of the ellipsoidal reflector.

9. The top-pumped optical device as set forth in claim 7, wherein the ellipsoidal reflector is solid, has refractive index higher than that of external substance of the ellipsoidal reflector, and provided with an optical reflective surface on its external surface so that the light from the light source is transferred to the gain medium structure by total internal reflection and reflection at the reflective external surface of the ellipsoidal reflector.