KR20010073496A - The being Decreased method of Arrayed Waveguide Grating device loss using Ultra-Violet Laser - Google Patents

Abstract

PURPOSE: A method for reducing loss of an arrayed waveguide grating element using an ultraviolet laser is provided to minimize loss due to diffraction of a wavelength multiplexer. CONSTITUTION: The method for reducing loss of an arrayed waveguide grating element using an ultraviolet laser following steps. A quantity of germanium oxide is added to the core layer in order to increase the refractive index of the core layer to the clad layer surrounding around thereof. The germanium oxide absorbs the ultraviolet rays and then the refractive index is increased above a certain value. Using this method, it is designed to increase the refractive index of the slab waveguide locally to maximize the optical coupling efficiency with the arrayed waveguide thereby minimizing the diffraction loss.

Description

The being Decreased method of Arrayed Waveguide Grating device loss using Ultra-Violet Laser}

SUMMARY OF THE INVENTION An object of the present invention is to use a silica material to diffract an element by diffraction in a binding region with an arrayed waveguide in a slab waveguide in order to effectively reduce light loss caused in the design and fabrication method of a wavelength division multiplexer and a demultiplexer, which are flat waveguide elements In order to greatly reduce the loss of the present invention, a method of locally increasing the refractive index using an ultraviolet laser was invented.

Wavelength Division Multiplexer (WDM) is one of the most anticipated technologies for increasing transmission capacity in optical communication systems. This device is designed to increase the transmission capacity of optical fiber by multiplexing and transmitting signals with different wavelengths in one optical waveguide and separating the signals according to the wavelength at the receiving end. The wavelength division optical transmission is a method of transmitting optical signals for each channel by dividing a wide optical frequency band into respective communication channels, which greatly increases information transmission capacity. This method has been made possible by the development of optical integrated circuits.

The wavelength division multiplexing technology developed to date for optical communication mainly includes WDM optical fiber coupler using micro-optic or fused optical fiber coupler technology using various optical components such as prism, diffraction grating and dielectric multilayer filter. have.

In the case of flat waveguide-type arrayed waveguide grating (AWG) -WDM, multiple WDMs can be integrated on the same substrate, and controllability and space of various optical elements such as controllability of channel frequency and channel bandwidth, Fabry-Perot optical filter, etc. Due to various advantages, such as high resolution procedure that cannot be performed on the screen, it is the most widely used method for manufacturing high-density WDM for high speed optical communication.

However, optical WDM devices can be broadly classified into devices using arrayed waveguide grating (AWG), devices using Mach-Zehnder, and devices using Bragg Grating. Among them, AWG devices are being actively researched. Has the disadvantage that the diffraction loss due to the arrayed waveguide is larger than that of other types of devices. Therefore, as a method for greatly improving the loss due to diffraction, a method of improving loss by ultraviolet irradiation that can arbitrarily control the path of light is developed.

In the present invention, various problems occur when fabricating a flat array waveguide grating device, which is a device capable of greatly increasing transmission capacity in an optical communication system. In particular, the optical loss due to diffraction in the combined region of the slab waveguide and the arrayed waveguide deteriorates the overall device characteristics and requires an additional device when applied to the system. As a method for improving the optical loss, the refractive index can be locally increased by irradiating an ultraviolet laser between the slab waveguide and the arrayed waveguide. As the refractive index increases, the optical path in the desired direction can be controlled and the input light can be incident into the array waveguide without loss.

Therefore, it is a development of a method of reducing the loss of the arrayed waveguide grating element using an ultraviolet laser that can significantly improve the optical loss problem generated during fabrication of the arrayed waveguide grating element.

Conventional wavelength multiplexers are being researched using semiconductors or polymer thin films, and in particular, optical integrated circuits using silica are capable of stability, high performance and miniaturization, and because of design flexibility, high reliability and good reproducibility One of the useful ways to build a multiplexer.

The fabrication of wavelength multiplexer using silica is more difficult to manufacture active optical devices because its material characteristics are passive compared to photovoltaic semiconductors and electro-optical integrated circuit devices such as InP / GaAs or LiNbO ₃ . In addition, the material characteristics are stable to environmental changes such as temperature and humidity, and mass production using the existing electronic device process, general purpose, and low price are possible.

The conventional silica plate waveguide type AWG-WDM device is composed of two slab waveguides and arrayed waveguides having a constant path difference. The wavelength multiplexed optical signal at the input end is incident in phase with each arrayed waveguide in the first slab waveguide, and in the arrayed waveguide, a constant phase change occurs due to the path difference between the waveguides, and enters the second slab waveguide. . As the second slab waveguide proceeds, the angular dispersion along the wavelength leads to the output at a specific angle.

When light is incident from the input waveguide to the first slab waveguide, the incident light causes diffraction and the diffracted light is incident on the arrayed waveguide, but some incident light propagates to the part between the arrayed waveguides, causing loss. . For this geometric reason, silica flat panel wavelength multiplexer devices have limitations in reducing losses. The present invention is the development of a new process to overcome these disadvantages.

1 is a cross-sectional structure of a typical silica flat waveguide device as an example to which the present invention is applied. A silica flat waveguide film is fabricated on a silicon substrate using chemical vapor deposition, flame hydrolysis deposition, ion exchange, sol-gel, sputter deposition, and the like.

After depositing a buffer thick film of 15-20 μm or more on silicon, a core layer in which actual light of about 6-8 μm is guided is deposited in the same manner. In core layer silica particulate deposition, germanium, boron and phosphorus are additionally added, which makes the refractive index of the core silica film larger than that of the lower cladding or upper clad silica film, allowing light to be guided along the core layer. Next, a dry-etch mask layer, such as a Cr thin film, is deposited on the core layer, a photo-resist is applied, and then a two-dimensional planar shape of the optical waveguide is formed using a photo-mask. The photoresist and dry mask layers are transferred by photo-lithography and wet-etch. Next, the core silica layer is etched using a square channel channel waveguide using a dry-etch method, and a silica clad waveguide is completed by depositing an upper clad silica fine particle layer of 15-20 μm or more.

As mentioned above, among the various problems that may occur when manufacturing a planar silica array waveguide grating element used in an optical communication system, in particular, optical loss due to low optical coupling efficiency with the array waveguide generated by diffraction in the slab waveguide Not only does this degrade the quality of the finished device, but it also requires additional equipment such as an optical amplifier when applied to an actual optical communication system, which not only increases the volume of the system but also results in economic losses.

In the present invention, in order to minimize the loss due to diffraction in the fabrication of a flat-panel silica wavelength multiplexing optical waveguide device, ultraviolet rays are irradiated at a local position of the slab waveguide to change the refractive index to minimize the loss due to diffraction of the wavelength multiplexer. We have developed a method for this.

1 illustrates a cross-sectional structure of an optical circuit device

2 is a structural example of an arrayed waveguide grating element

3 shows the location and shape of the exposure of an ultraviolet laser to an arrayed waveguide grating element.

2 is a structural example of a general flat array waveguide grating element. The array waveguide grating element is composed of two slab waveguides and arrayed waveguides having a constant path difference. The wavelength multiplexed optical signal at the input end is incident in phase with each arrayed waveguide in the first slab waveguide, and in the arrayed waveguide, a constant phase change occurs due to the path difference between the waveguides, and enters the second slab waveguide. . As the second slab waveguide proceeds, the angular dispersion along the wavelength leads to the output at a specific angle.

3 is a method of minimizing loss by local ultraviolet irradiation of the slab waveguide developed in the present invention.

A large amount of germanium oxide is added to the core layer in the thin film in order to increase the refractive index compared to the cladding layer surrounding the surrounding layer. When the germanium oxide absorbs ultraviolet rays, the refractive index increases by a certain amount or more. Using this method, the refractive index of the slab waveguide is locally increased to maximize the optical coupling efficiency with the arrayed waveguide to minimize the diffraction loss.

In the fabrication of wavelength multiplexers used in optical communication systems, researches on the existing wavelength multiplexers have been conducted using semiconductors or polymer thin films. In particular, optical integrated circuits using silica are capable of stability, high performance and miniaturization. It is one of the useful methods to fabricate wavelength multiplexer because of design flexibility, high reliability and good reproducibility. However, flat waveguide grating device (AWG) has the disadvantage that diffraction loss by array waveguide is larger than other types of devices. . Therefore, if the loss improvement method by UV irradiation that can control the path of light is used as a method to greatly improve the loss caused by such diffraction, the diffraction loss generated in the slab waveguide can be greatly reduced, thereby improving the economics of device fabrication. In addition to improving device performance, it is possible to increase the stability of the system by eliminating the problem of communication failure when applied to the optical communication system.

Claims (3)

Method of Locally Irradiating Ultraviolet Rays to Change the Refractive Index Inside Slab Waveguides in Array Waveguide Grating Devices How to reduce the loss of array waveguide grating element by forming additional waveguide structure inside the waveguide by using ultraviolet rays Loss Control Method According to Location and Shape of UV Laser Irradiation on Slab Waveguide