1. Field of the Invention
The present invention relates to an optical coupling device and a master used in fabricating the optical coupling device, more particular, to an integrated type optical coupling device and a master used in fabricating the optical coupling device that an optical alignment between a narrow-pitch multi-channel optical waveguide and an optical fiber array can be easily accurately performed and the fabricating cost thereof can be reduced.
2. Description of the Prior Art
Recently, as an information communication industry is developed, data transmission using a communication network such as Internet is actively increased, thereby large scale, high speed, and high density of a transmission/exchange system for increasing the transmitting amount and the transmitting speed of data has been demanded. According to the demand, the research for integrating the channel to 40 channels greater than the existing 8 or 16 channels in a same area has been progressed. At this case, since the pitch between the channels is reduced from 250 μm to 125 μm, it is difficult to fabricate the system. Accordingly, the implement of the optical device which can easily integrate the channel, can increase optical coupling efficiency with the optical fiber, and can reduce the fabricating cost thereof is needed.
Generally, the optical coupling device for optically coupling with the optical fiber and electrically or optically controlling an optical signal comprises modules formed with a plurality of V-shaped grooves for mounting an optical fiber array, a waveguide element coupled between the modules and formed with a multi-channel optical waveguide, and a controlling means for electrically or optically controlling the optical signal transmitted through the optical waveguide.
In the conventional optical coupling device having the above-mentioned structure, the module and the waveguide element are separately fabricated and are coupled with each other. Accordingly, first, optical coupling loss can be generated due to the variation if a thermal or mechanical impact is applied thereto. Second, since the dynamic stability of the optical fiber is not secured due to the space of the lower portion when the optical fiber is aligned in the V-shaped groove, the length of the V-shaped groove must be relatively long, thereby it is difficult to reduce the size of the structure. Also, third, an expensive optical fiber aligning device must be used in order to make a precise optical alignment between the optical waveguide and the optical fiber array. Fourth, since the optical fiber is fixed by an adhesive to make the active optical alignment with the waveguide element after the intensity of the transmitted light is checked by the channel, the time and technical cost required for aligning the optical fiber array is proportionally increased as the number of the channels is increased.
On the other hand, a master (a metallic pattern) is used in manufacturing the module mounted with the optical fiber and the waveguide element. The multi-step master is fabricated by a patterning process using several masks each having a different exposed location. Accordingly, there is a merit that multi-step structure having a different height proportional to the exposed number is made, but the masks as same number as the exposed number must be fabricated, an accurate location alignment of the mask is need in each of the exposing steps, and it is difficult to accurately adjust the time for exposing the photoresist film and the height of the fine structure.
As an alternative method, a method for fabricating a master, applying the photoresist film thereon, and performing the plating to implement a fine structure having various heights on the same surface is suggested. In this method, since the photoresist film is formed on the master and then is exposed by using the mask, a precise mask aligning technique is needed, the mask fabricating processes as same number as the number of the steps of the mask must be repeatedly performed. Above all, since a precise dimension control determines the precision of the master which is finally fabricated in the master fabricating process, a precise machining technique is needed. In addition, there is a problem that the fine structure fabricated previously is damaged when forming the photoresist on the fabricated master.