KR20000025626A - Erbium doped planar amplifier and method for manufacturing optical devices using amplifier - Google Patents

Abstract

PURPOSE: A device and method is provided to be applied to variety of optical devices like WDM and laser by using an eribum doped planar amplifier to reduce transfer loss and contact loss with optical fibers. CONSTITUTION: A device comprises an erbium doped core layer(ED), an erbium-undoped core layer(UD), an inputting element(1) a WDM coupler(2), a wave guide(3), a wave length separator(4), an anti-reflective angled wave guide(5), a lower clad layer(10), and an upper clad layer(12). A method comprises a step of forming the ER-undoped core layer on the lower clad layer; a step of forming defining the optical amplifier area by selectively etching the ER-undoped core layer; and a step of forming the ER-doped core layer at the optical amplifier area. The method further comprises a step of forming the wave guide at the optical amplifier area between the input part and the output part and a step of forming the upper clad layer at the whole structure.

Description

Planar optical amplifier and method of manufacturing optical device using same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of optical device manufacturing, and more particularly, to an erbium-doped planar optical amplifier capable of improving optical amplification characteristics, transmission loss, and connection loss with optical fibers, and an optical device manufacturing method using the same. will be.

Background Art With the development of optical communication technology, planar waveguide technology has been researched and developed for manufacturing integrated optical components such as couplers and amplifiers. Conventional lossless distributors consist of an EDB (erbium doped fiber amplifier) and a fiber type optical splitter. In recent years, erbium doped planar amplifiers (EDPAs), which have the advantage of accepting a large number of channels and manufacturing various functional devices in place of EDFA, have been studied.

Conventional planar optical amplifiers have methods such as flame hydrolysis deposition (FHD), aerosol, plasma enhanced chemical vapor deposition (PECVD), and electron beam deposition (E-beam deposition) on silicon or silica (quartz, glass) substrates. It was formed by a series of processes to form erbium-containing silica and to define channels by exposure and dry etching. The general form of the planar optical amplifier consists of an erbium-doped core layer in which the input stage, the optical amplification region and the output stage all have a transmission loss higher than 1.2 mW / cm, amplification threshold power of 27 mW to 260 mW, and a gain. There are few problems. In particular, the erbium element has an absorption loss of 1550 nm optical signal greater than 1.2 dB / cm and a refractive index difference (Δn) of the core layer is about 1.2%, resulting in large connection loss with the optical fiber and 100% single mode output. This is difficult. Therefore, it is difficult to manufacture functional devices such as a lossless optical splitter using a planar optical amplifier and an optical amplifier for WDM.

The present invention devised to solve the above problems provides a planar optical amplifier and an optical device manufacturing method using the same, which can obtain high gain characteristics by reducing the transmission loss and amplification threshold power of the input and output terminals of the planar optical amplifier. There is a purpose.

Figure 1a is a plan view of a planar waveguide type lossless optical splitter according to an embodiment of the present invention,

1B and 1C are enlarged views of portions A and A ′ of FIG. 1A, respectively;

Figures 2a to 2e, 3a and 3b is a cross-sectional view and a plan view of a planar waveguide type lossless optical splitter manufacturing process according to an embodiment of the present invention.

* Explanation of reference numerals for the main parts of the drawings

ED: Erbium-doped core layer UD: Erbium-undoped core layer

1: input stage 2: WDM combiner

3: optical waveguide of optical amplification area 4: wavelength separator

5: anti-reflective waveguide 6: output stage

7: optical splitter A, A ': inclined connection

10: lower clad layer 12: upper clad layer

M: Mask AM: Align Mark

The present invention for achieving the above object is an erbium-doped core layer (Er-doped core) formed in the optical amplification region on the lower clad layer; An erbium-undoped core layer formed on the lower clad layer except in the optical amplification region; An input terminal formed on the erbium-undoped core layer; An optical waveguide connected to the input terminal and formed in the erbium-doped core layer of the optical amplification region; And an output terminal connected to the optical waveguide and formed at the erbium-undoped core layer.

In addition, the present invention for achieving the above object is a first step of forming an erbium-undoped core layer (Er-undoped core) on the lower clad layer; Selectively etching the erbium-undoped core layer to define an optical amplification region; A third step of forming an erbium-doped core layer in the optical amplification region; Selectively etching the erbium-undoped core layer and the erbium-doped core layer to form an input terminal and an output terminal, each end of which is connected to the optical amplification region, in the erbium-undoped core layer, A fourth step of forming an optical waveguide in the optical amplifier region between the input terminal and the output terminal; And a fifth step of forming an upper cladding layer on the entire structure in which the fourth step is completed.

According to the present invention, an erbium-undoped core layer and an erbium-doped core layer are formed on a single substrate, and the planar waveguide is defined by dry etching so that the waveguides of the input and output terminals except the optical amplification region are erbium-undoped core layers. The present invention provides a planar optical amplifier capable of suppressing signal attenuation of signal light and pumped light by reducing transmission loss to 0.05 dB / cm or less, and an optical device manufacturing method using the same.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention.

1A is a plan view of a planar optical amplifier and a 16-branch multichannel lossless optical splitter using the same according to the present invention, and FIGS. 1B and 1C are enlarged cross-sectional views of portions A and A 'of FIG. 1A, respectively.

As shown in FIG. 1A, a planar optical amplifier structure according to an exemplary embodiment of the present invention has an input terminal 1 and a WDM coupler 2 formed in an erbium-undoped core layer UD on a lower clad layer or a silica substrate. Connected to an optical waveguide (3) in the erbium-doped core layer (ED) and an optical waveguide (3) in the optical amplification region and to an output end (6) formed in the erbium-undoped core layer (UD). Is done.

The WDM combiner 2 couples the signal light (1550 nm wavelength) and the pumping light (980 nm, 1480 nm wavelength) of the input terminal 1.

FIG. 1A is a 980 nm, 1480 nm / 1550 nm Wavelength separator 4 formed in the erbium-undoped core layer UD and located between the output end 6 and the waveguide 3 in the optical amplification region. And a 1x16 planar waveguide type optical splitter 7 is additionally configured.

1A to 1C, 2A to 2E, 3A, and 3B, a planar optical amplifier and a method of manufacturing a lossless distributor including the same according to an embodiment of the present invention will be described.

2A and 3A show a PSG (phosphorous silicate glass) lower cladding layer 9 and GPSG (germano-phosphorous silicate glass) by FHD using oxyhydrogen flame and chloride raw materials on a 3 to 6 inch silicon wafer (not shown), respectively. ) A cross-sectional view and a plan view showing formation of an erbium-undoped core layer UD.

The production of the lower clad layer 9 by the FHD method was performed by reacting SiCl ₄ , BCl ₃ , POCl ₃ with oxyhydrogen salt as a raw material, depositing silica fine particles on a silicon substrate, and heat-treating in a high temperature electric furnace at 1300 ° C. to 1350 ° C. After the silica film is formed, it is annealed at 900 ° C to 1000 ° C for 12 hours to 72 hours. In this manner, the lower clad layer 10 having a refractive index of 1.4460 to 1.4480 in light of 1550 nm wavelength is formed, and the thickness thereof is controlled to 19 μm to 23 μm to prevent loss due to mutual coupling with the silicon substrate.

The erbium-undoped core layer (UD) is formed of SiCl ₄ , BCl ₃ , POCl ₃ as the main raw material, using GeCl ₄ to control the refractive index, and heat-treated at a high density temperature of 1250 ℃ to 1300 ℃ after deposition. Thereafter, annealing is performed at 850 ° C. to 950 ° C. for 12 hours to 72 hours to remove stress generated in the heat treatment phase when forming the erbium-undoped core layer (UD). The refractive index of the erbium-undoped core layers 1 and 6 is 1.4600 to 1.4628 to control the refractive index difference Δn to 0.8 to 1% and the thickness is formed to be 5.9 μm to 6.1 μm.

In the above description, the lower clad layer 10 and the erbium-undoped core layer UD are formed on the silicon substrate as an example. In the case of using the silica substrate, since the substrate itself forms the lower cladding layer 10, when the lower cladding layer 10 is formed on the silicon substrate, the subsequent process proceeds in the same manner as in the manufacturing process using the silica (quartz) substrate.

2B shows a mask M on the erbium-undoped core layer UD to define the formation region of the erbium-doped core layer, respectively, and the exposed erbium-undoped core layer UD. It is sectional drawing which shows what was removed by etching.

The mask M is formed by the following process. First, an aluminum film having a thickness of 2500 m to 4000 m is deposited on the erbium-undoped core layer UD by sputtering, a photoresist pattern (not shown) is formed on the aluminum layer, and the photoresist pattern is etched. The aluminum film is patterned by RIE (reactive ion etching) etching using Cl ₂ , BCl ₃ gas, and then a photoresist pattern is removed to form a mask (M). The mask M formed as described above exposes the erbium-undoped core layer UD in the shape of the light amplification region of FIG. 1A, that is, the erbium-doped core layer ED.

In addition, the etching of the erbium-undoped core layer (UD) is performed using an inductive coupled plasma etching (ICP) dry etching at an etching rate of 2500 Pa / min to 5000 Pa / min using CF ₄ and CHF ₃ gas.

When the erbium-undoped core layer UD is etched in the above process, for the non-reflective connection between the erbium-undoped core layer and the erbium-doped core layer to be formed later, as shown in FIGS. 1A to 1C. Similarly, an angled butt coupling (A, A ') is formed in the waveguide part, and the angle (θ) of the inclined connection is 8 ° to 15 °.

2C and 3B show that after etching the erbium-undoped core layer UD, the aluminum mask M is removed by wet etching, and the smoothness of the etching side of the erbium-undoped core layer UD is maintained. The cross-sectional view and plan view showing a state in which reflow was carried out for 1 hour in an electric furnace at 1180 ° C to 1230 ° C. Reference numeral AM in the plan view of FIG. 3B denotes an alignment mark, and the alignment mark AM is for secondary and tertiary patterning in the region where the erbium-undoped core layer has been removed.

FIG. 2D shows that SiCl ₄ , BCl ₃ , POCl ₃ and erbium-chelate are reacted with a flame in a region where an erbium-undoped core layer is removed to form fine particles, and densified at a temperature of 1220 ° C. to 1280 ° C. After annealing at 900 ° C. to 1000 ° C. for 12 to 72 hours to form an erbium-doped core layer (ED), an etch mask (not shown) is formed on the surface of the erbium-doped core layer (ED) formed in the optical amplification region. (Or not), the erbium-doped core layer deposited on the erbium-undoped core layer (UD) is etched and the etching mask is removed, followed by heat treatment at 1150 to 1200 ° C for 1 to 2 hours. To reflow to make the erbium-doped core layer ED formed in the optical amplification region planarized.

In this case, the erbium-doped core layer ED may be formed by a method such as FHD solution doping using an erbium aqueous solution in addition to the above-mentioned aerosol method and PECVD method. The concentration of the erbium element is adjusted to 0.4 Wt% to 1 Wt% and the refractive index difference (Δn) is 1% to 1.2%, and the thickness is 5.9 μm to 6.1 μm which is the same as the erbium-undoped core layer (UD). To deposit. In particular, the thickness and refractive index of the waveguide are determined in consideration of the matching of the mode field diameter, which is a coupling element between the signal light and the pumping light between the erbium-doped core layer and the erbium-undoped core layer.

Subsequently, an etch mask pattern (not shown) similar to the waveguide shape of FIG. 1A is formed on the erbium-undoped core layer UD and the erbium-doped core layer ED. The undoped core layer UD and the erbium-doped core layer ED are etched to form a WDM coupler 2 at the input terminal 1 of the waveguide as shown in FIG. The wavelength separator 4 is formed in front of the distributor 7 to form a lossless optical splitter structure in the erbium-undoped core layer UD and the erbium-doped core layer ED. In this case, the erbium-undoped core layer (UD) and the erbium-doped core layer (ED) are etched with ICP under the same conditions, and the thickness of 0.5 μm to 1 μm based on the erbium-undoped core layer (UD). Over etching.

The wavelength separator 4 has a function of separating the pumped light (980 / 1480nm) from the amplified signal light, and converged to a radius of curvature of 2 mm or less in order to prevent the reflection loss generated at the rear end. In addition, adjacent to the wavelength separator 4, an antireflective angled waveguide 5 inclined at 30 degrees in longitudinal section is formed.

Figure 1a showing an embodiment of the present invention illustrates the 1x16 lossless splitter in the configuration of the optical splitter 7 and has expandability up to 128 channels. You can change it. The optical splitter 7 formed in the above-described structure can be completely compensated for the distribution loss by designing and manufacturing the total amplification gain of the erbium-doped core layer 3 to 16 kW to 20 kW. In the same manner, multichannel lossless optical splitters such as 1x32 and 1x64 can be manufactured.

In addition, the WDM coupler 2 and the output terminal 6 are formed as shown in FIG. An Erbium doped planar laser (EDPL) may be manufactured by constructing a mirror with a reflective structure without omitting an inclination.

FIG. 2E is a BPSG (boron-phosphorous silicate glass) upper cladding layer 11 having a thickness of 25 μm to 33 μm deposited on the entire surface of the substrate on which the waveguide is formed by FHD, heat treatment at 1150 ° C. to 1180 ° C., and then heat treatment. This is a cross-sectional view showing an annealing state for 72 hours at a temperature of 850 ℃ to 950 ℃ in order to remove the stress generated.

The present invention made as described above forms the waveguide of the input stage (optical signal port, pumping optical port) 1 of the optical amplifier 1 and the WDM coupler 2 as an erbium-doped core layer 1, By forming the optical waveguide 3 in the optical amplification region with the loft core layer ED, the waveguide is formed of a heterogeneous material layer on a single substrate. In addition to the input stage 1, the output stage 6 is also formed of a core layer erbium-doped, and constitutes a multi-channel lossless PLC optical splitter, and the splitter structure of the output stage during channel expansion is modified in consideration of the total gain of the optical amplification region. do.

The wavelength splitter of the output stage composed of an undoped core layer separates the pumped light (980, 1480 nm) wavelength into an amplified optical signal in the 1550 nm band and has a function of a filter. When the insertion loss of a lossless 1x16 (1x32, 1x64, 1x128) optical splitter is 12 kW to 21 kW, the total amplification gain of the erbium-doped core layer (ED) is 16 kW to 25 kW. By designing this, the dissipation loss can be close to 0 Hz.

According to the present invention made as described above, the signal light and the pumping light input of the input stage is coupled in the WDM coupler composed of the erbium-undoped core layer, the transmission loss is lowered to 0.01 0.01 / cm to 0.05 ㏈ / cm. Therefore, it is possible to prevent attenuation of signals of the signal light and the pumping light, and to realize a planar optical amplifier having a high gain characteristic of lowering the critical amplification power of the pumping light to 20 mW or less and improving the gain characteristics of about 0.7 kW / cm to 1 kW / cm. Can be. Therefore, gain characteristics and low transmission loss can be obtained from the planar optical amplifier according to the present invention, and thus it can be applied to various integrated optical devices such as WDM, laser, resonator, etc. using the planar optical amplifier.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made in the art without departing from the technical spirit of the present invention. It will be apparent to those of ordinary knowledge.

Claims (10)

In the planar optical amplifier, An erbium-doped core layer formed in the optical amplification region on the lower clad layer (Er-doped core); An erbium-undoped core layer formed on the lower clad layer in a region other than the optical amplified region; An input terminal formed on the erbium-undoped core layer; An optical waveguide connected to the input terminal and formed in the erbium-doped core layer of the optical amplification region; And An output terminal connected to the optical waveguide and formed in the erbium-undoped core layer Planar optical amplifier comprising a. In the optical device manufacturing method, A first step of forming an erb-undoped core layer on the lower clad layer; Selectively etching the erbium-undoped core layer to define an optical amplification region; A third step of forming an erbium-doped core layer in the optical amplification region; Selectively etching the erbium-undoped core layer and the erbium-doped core layer to form an input terminal and an output terminal, each end of which is connected to the optical amplification region, in the erbium-undoped core layer, A fourth step of forming an optical waveguide in the optical amplifier region between the input terminal and the output terminal; And A fifth step of forming an upper cladding layer on the entire structure in which the fourth step is completed Optical device manufacturing method comprising a. The method of claim 2, In the fourth step, And forming a wavelength divisional multiplier coupler in the erbium-undoped core layer between the input terminal and the optical amplification region, thereby connecting the input terminal and the optical waveguide. The method of claim 3, wherein In the second step, And forming an inclined coupling portion for anti-reflective bonding at an interface between the erbium-undoped core layer and the erbium-doped core layer. The method of claim 4, wherein In the fourth step, And forming a wavelength separator and an optical splitter in the erbium-undoped core layer between the optical waveguide and the output terminal. The method of claim 5, In the fourth step, And forming an anti-reflective gradient waveguide in the erbium-undoped core layer adjacent to the wavelength separator. The method of claim 3, wherein And forming a mirror at an interface between the erbium-undoped core layer and the erbium-doped core layer to produce an EDB (erbium doped planar laser). The method according to any one of claims 2 to 7, The second step, Depositing an aluminum film on the erbium-undoped core layer; Forming a photoresist pattern defining the photo amplification region on the aluminum film; Etching the aluminum layer using the photoresist pattern as an etching mask; Etching the erbium-undoped core layer using the aluminum film as a mask; And Optical device manufacturing method comprising the step of removing the aluminum film. The method of claim 8, After the second step, And a sixth step of reflowing by heat treatment to maintain the smoothness of the erbium-undoped core layer etching side. The method of claim 8, The third step, Forming the erbium-doped core layer on the entire structure of which the second step is completed; Forming an etch mask on the erbium-doped core layer in the optically amplified region; Removing the erbium-doped core layer exposed after the etching mask is formed; And Optical device manufacturing method comprising the step of removing the etching mask.