KR20010086022A - Tuning of optical devices - Google Patents

Abstract

A method of adjusting an optical device including a waveguide, the method comprising applying localized heating to the device to alter the optical properties of the waveguide.

Description

How to adjust the optical device {TUNING OF OPTICAL DEVICES}

The construction of the planar optical waveguide device is known. These are generally constructed by depositing a layer on top of a silicon substrate that is made photosensitive and has a portion of the deposited (and etched) layer sensitive to light of a selected wavelength to manipulate their optical properties. In this way, often very complex optical waveguide devices can be formed on a silicon substrate.

It is desirable to provide a system of post-treatment of optical waveguides in order to adjust the properties of any complex device on which the waveguide forms part thereof.

The present invention relates to the thermal treatment of waveguides for altering properties.

1 shows schematically the processing of a thermal process of a waveguide;

2 illustrates an application example in an MZI type device.

3 illustrates another form of processing of a waveguide type device.

4 is a method of implementing the present invention. And Figure showing the relationship between.

Explanation of symbols on the main parts of the drawings

1, 100: waveguide 10: multiplexer

14 device 15 non-transmissive layer

According to a first aspect of the invention, a method of adjusting an optical device incorporating a waveguide is provided, the method comprising applying localized heating to the device to alter the optical properties of the waveguide.

Localized heating can be applied by a laser device, such as a UV or infrared laser device.

The device may include a waveguide formed on the substrate.

The method can be used to adjust one arm of an interferometer device.

Localized heating can be used to cause thermal relaxation, thermal diffusion, or structural changes in the device.

In one embodiment, the method can be used to record a grating structure in a waveguide.

In a preferred embodiment, the local thermal treatment of the wafer is performed using an infrared or UV laser device. Suitable thermally sensitive waveguides comprising a negative index grating in a germanosilicate planner waveguide are described in "MV Bazylenko, M Gross, A Simonian, PL Chu, Journal of Vacuum Science and Technology, A14, (2) PP336-345, 1996." and J Canning, D Moss, M Aslund, MBazylenko, Election Letters, 34 (4) pp336-367 (1998) ", and can be prepared by using a hollow cathode plasma enhanced chemical vapor deposition (HEPECVD) process. .

Referring to Figure 1, localized heat is in the region of the waveguide to alter the optical properties. Preferably, the heat treatment used is designed to have at least a different effect on the waveguide 1.

Therefore, when a UV laser is used, it can be used on the silicon substrate 2 through which no UV light passes, as shown by arrow 10, while for an IR laser it can be used from above the waveguide 1 as shown by arrow 12. have.

Localized heating can be used to cause localized changes in device 14. Such changes may include thermal relaxation of internal stresses, thermal diffusion of the material or thermal damage of the material layer.

For example, FIG. 2 may initially be configured on a wafer and for example an add-drop multiplexer constructed using the Mach-Zehnder principle, which is adjusted by heat rather than by UV adjustment of the arm at points 11 and 12. 10) is shown.

When using local radiation, which can cause unwanted effects on the waveguide 100, as shown in FIG. 3, the non-transmissive layer 15 is placed over the waveguide 100 to minimize photosensitive changes in the area of the waveguide 100. Can be formed.

The use of local heating can have many uses. First, as described above, it is used to modify waveguide properties. This use is ideal for example in Mach-Zehnder type devices. Another device may include a multimode device in which each arm can be thermally treated to adjust its properties.

An alternative use for localized heating is localized heating of the substrate / wafer to control or release the stress through damage or annealing of the wafer. For example, it is known to construct an optical waveguide device having an internal waveguide structure using a plasma enhanced chemical vapor deposition process on a silicon substrate. Unfortunately, the formation process will often result in an asymmetric birefringent effect. The first birefringent effect defined as will be due to the peripheral characteristics of the waveguide. The second birefringent effect defined by D will be due to several stresses associated with thermal coefficient mismatch of the substrate and deposition.

In an embodiment of the present invention, localized heating of the above structure can provide a method of altering the overall birefringence in the waveguide by releasing existing stresses or introducing additional stresses. For example, as shown in FIG. "Symbol" of 200 is Opposite of 202, birefringence 204 It can be offset by introducing additional stress in the direction of 200.

Alternatively, localized heating can be used in an anneal form to slowly anneal the entirety of the wafer while simultaneously measuring waveguide properties. In this method, the entirety of the substrate may be thermally annealed on the mount with a localized heating furnace providing more precise annealing than is available through the use of conventional convective heating. In this way, thermal annealing can be closely monitored and changed at any particular point.

The principle of localized heating can also be extended to the actual direct recording of thermally generated device structures using small spot sizes to thermally guide rather than optically induced modifications of the waveguide. Again, it can be used for post processing of waveguides to perform adjustments to the structure of more complex waveguide devices.

One application is the process of polarization control by heating of a substrate. An ideal regex source may be an array of diode bars at 810 nm absorbed by the substrate and waveguide. CO / CO ₂ lasers can be used to heat the surface and affect the internal waveguide. Moreover, the device can be adjusted in the waveguide or the substrate. Preferably, an IR source is used to thermally heat the substrate and prevent damage.

It will be appreciated by those skilled in the art that various modifications and variations can be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as described above. However, this embodiment is for illustrative purposes in all respects and is not limited thereto.

Claims (7)

A method of adjusting an optical device comprising a waveguide, the method comprising applying localized heating to the device to change the optical properties of the waveguide. The method of claim 1, wherein the localized heating is applied by a laser device. The method of claim 2, wherein the laser device is a UV or infrared laser device. 4. A method according to any one of the preceding claims, wherein the method is used to calibrate one arm of an interferometer system. The method according to any one of claims 1 to 4, wherein the method is used for thermal annealing of the substrate on which the waveguide is formed. 6. A method according to any one of the preceding claims, wherein said localized heating results in thermal relaxation, thermal diffusion or damage in said substrate. 7. The method of any one of the preceding claims, further comprising using the heating to record the structure in the waveguide.