KR100576710B1 - Bidirectional module with a transmitter and a receiver and method for manufacturing the same - Google Patents

Abstract

The present invention discloses a bidirectional module comprising a transmitter and a receiver capable of improving electro-optical crosstalk and yield and a method of manufacturing the same. The disclosed invention is a bidirectional module consisting of a transmitter and a receiver, the transmitter comprising a distributed feedback (DFB) laser diode having an external cavity.

Bidirectional Module, Laser Diode, Crosstalk, External Cavity

Description

Bidirectional module with a transmitter and a receiver and method for manufacturing the same}

1 is a plan view of a bidirectional module according to the present invention.

FIG. 2 is a cross-sectional view taken along line II-II ′ of FIG. 1.

(Explanation of symbols for the main parts of the drawing)

10: DFB area 20: passive waveguide area

30: DFB reflection area 40: absorption waveguide area

50: current blocking region 60: photodiode region

100: bidirectional module 100a: transmitter

100b: receiver

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light integrated semiconductor device and a method of manufacturing the same. More particularly, the present invention relates to a bidirectional module having a transmitter and a receiver and a method of manufacturing the same.

The bidirectional module for fiber to the home (FTTH) simultaneously performs the functions of a receiver for receiving a 1.5 μm wavelength signal of an optical line terminal (OLT) and a transmitter for transmitting a signal of 1.3 μm wavelength. In order to perform this function, the bidirectional module requires a 1.3 μm laser diode and a 1.5 μm photodiode. In particular, since the bidirectional module for FTTH must use a single fiber, it must include a photodiode, a laser diode, and a coupler. The laser diode generally includes a distributed feedback laser diode and a DBR. (distributed Bragg reflector) Laser diode is mainly used.

Currently, in order to reduce the price, a PLC (planar lightwave circuit) that forms a bidirectional module by integrating optical devices such as photodiodes, laser diodes, and couplers on one substrate, and a PIC (monolitically integrated whole optical devices) Photonic integrated circuit technology has been proposed. In this case, the PIC technology may include a branch type and an in-line type such as a Y-type branch. This PIC technology is advantageous over the PLC method in terms of cost, but has a disadvantage in that the manufacturing method is complicated.

On the other hand, the in-line bidirectional module of the PIC technology is easy to manufacture and has the advantages of small size, but it is known that the electrical cross-talk (electric cross-talk), optical cross-talk, and process yield is poor.

Accordingly, a technique of inserting a saturable absorber and a semi-insulating layer into an in-line bidirectional module and an electro-optic modulator to remove optical crosstalk added when a 1.5 μm laser diode is modulated Has been proposed.

By interposing the absorber, the SI layer, and the EM as described above, the electrical and optical crosstalk of the bidirectional module could be improved to some extent. However, the conventional in-line bidirectional module uses the DFB and DBR laser diodes as described above. When using the DFB diodes, it is difficult to obtain a single mode yield. The loss has a fatal weakness.

Moreover, bidirectional modules for mounting in the system must be able to withstand external optical perturbations.

Accordingly, the technical problem to be achieved by the present invention is to provide a bidirectional module including a laser diode that can improve the electro-optical crosstalk and yield.

In addition, another technical problem to be achieved by the present invention is to provide a method of manufacturing a bidirectional module including the laser diode.

In order to achieve the above technical problem, the present invention is a bidirectional module consisting of a transmitter and a receiver, the transmitter includes a DFB laser diode having an external cavity.

In addition, according to another aspect of the present invention, a method of manufacturing a bidirectional module includes forming a lower cladding layer on a substrate on which a DFB region, a passive waveguide region, a DFB reflection region, an absorption waveguide region, a current blocking region, and a photodiode region are defined. . A diffraction grating is formed in the lower cladding layer corresponding to the DFB region and the DFB reflecting region, and then a waveguide having a different wavelength for each region is simultaneously formed on the lower cladding layer by a selective area growth (SAG) method. Thereafter, forming an upper cladding layer on the waveguide.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited by the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape and the like of the elements in the drawings are exaggerated to emphasize a more clear description, and the elements denoted by the same reference numerals in the drawings means the same elements.

In this embodiment, an external cavity laser diode is used as the DFB laser diode of the bidirectional module. Such external cavity laser diodes are known to be superior in noise, modulation width and chirp characteristics to DFB laser diodes and are not significantly affected by externally reflected signals. In addition, an external cavity laser can eliminate the use of an optical isolator and is advantageous in packaging with fibers.

Accordingly, the in-line bidirectional module integrated with such an external cavity laser can improve the single mode yield, and can also have a great effect on the speed characteristic, the chirp characteristic and the crosstalk characteristic.

This will be described in more detail with reference to the accompanying drawings, Figures 1 and 2 of the present invention.

As shown in FIG. 1, the bidirectional module 100 includes a DFB region 10, a passive waveguide region 20, a DFB reflecting region 30, an absorbing waveguide region 40, a current blocking region 50, and a photodiode. It consists of an area 60.

The DFB region 10 is designed to oscillate at an optical wavelength of 1.3 mu m. The passive waveguide region 20 is a region in which stable oscillation occurs by adjusting the phase of the light reflected by the DFB reflection region 30 and being fed back. In addition, the waveguides of the passive waveguide region 20 and the DFB reflective region 30 have a band gap energy greater than or equal to the energy corresponding to the oscillation wavelength of the DFB region. The DFB region 10, the passive waveguide region 20, and the DFB reflecting region 30 constitute a 1.3 mu m transmitter region 100a, which becomes an external cavity laser diode.

On the other hand, the absorption waveguide region 40 absorbs 1.3 μm light passing through the DFB reflecting region 30, thereby preventing 1.3 μm light passing through the DFB reflecting region 30 from entering the photodiode region 60. . The current blocking region 50 electrically separates the transmitter regions 10, 20, 30 and the region detecting the 1.5 μm light, that is, the photodiode region 60. Photodiode region 60 detects light of 1.5 μm as is known. Here, the receiver region 100b is defined by the absorption waveguide region 40, the current blocking region 50, and the photodiode region 60.

Here, in order to adjust the light size, a spot size converter (not shown) may be provided outside the DFB region 10. The spot size converter serves to facilitate the operation in packaging the size of the light emitted from the transmitter, that is, the external cavity laser diode 10-30, to the fiber. In addition, as the spot size converter is installed, the reflectances of the transmitter and the receiver become asymmetrical. That is, the reflectance on the transmitter side where the spot size converter is installed becomes low. Accordingly, the output of the laser diode is weighted towards the spot size converter, thereby improving power and optical crosstalk.

A bidirectional module having such a structure is formed in the following manner.

That is, as shown in FIG. 2, a lower cladding layer 120, for example, an N-InP layer 120, is formed on a semi-insulating (SI) substrate 110. In this case, the SI substrate 110 is defined by the DFB region 10, the passive waveguide region 20, the DFB reflection region 30, the absorption waveguide region 40, the current blocking region 50, and the photodiode region 60. It is.

The waveguide 140 is formed on the lower cladding layer 120. The waveguide 140 is formed by a selective area growth (SAG) method that is selectively grown for each region, thereby forming a waveguide having a different wavelength for each region. This SAG method forms a waveguide to have different wavelengths by forming a mask (not shown) at the boundary of each region and selectively growing the waveguide so that different wavelengths are generated for each region before the waveguide is formed. can do. This SAC method is described in detail in Korean Patent Laid-Open Publication No. 2000-19254. Accordingly, the 1.3 μm active layer 140a corresponding to the DFB region 10, the 1.25 μm passive waveguide 140b formed in the passive waveguide region 20, the DFB reflecting region 30, the absorbing waveguide region 40, and the currents. 1.3 μm active layers 140c, 140d and 140e formed in the blocking region 50, and 1.5 μm active layer 140f formed in the photodiode region 60 may be formed.

Meanwhile, the diffraction grating layer 130 should be formed in the DFB region 10 and the DFB reflective region 30. As shown in FIG. 2, the diffraction grating layer 130 may be formed in the N-InP layer 120 under the waveguide 140 or may be formed on the waveguide 140. The diffraction grating layer 130 formed in the DFB region 10 and the DFB reflection region 30 may have the same structure, and the difference in the Bragg wavelength of each diffraction grating may cause the waveguide 140. In the SAG regrowth process to form, it can adjust in the form of a mask.

An upper cladding layer 150, for example, an InP layer, is formed on the waveguide 140. In this case, the upper cladding layer 150 may be separated for each region. Here, the upper cladding layer in the current blocking region serves to block crosstalk between the laser diode region and the photodiode region, and thus, may be formed of an electrically insulating layer. For example, an SI InP layer may be used.

As described in detail above, according to the present invention, in the bidirectional module including the laser diode and the photodiode, a laser diode having an external cavity is used as the laser diode. Since the external cavity laser diode has excellent characteristics in noise characteristics, modulation width characteristics, and chirp characteristics, it is possible to improve the speed characteristics and the communication distance of the bidirectional module. In addition, in the present embodiment, since the external cavity laser diode is composed of the DFB region, the passive waveguide region, and the DFB reflecting region, the laser diode characteristics can be further improved.

In addition, the bidirectional module of the present embodiment can obtain one oscillation light in the DFB laser diode according to the difference in the diffraction grating reflection surface wavelength of the DFB laser diode having the external cavity. Therefore, single mode yield can be improved. Moreover, the bidirectional module of the present embodiment uses a reflective surface made of a diffraction grating, thereby breaking the power balance generated on both sides of the DFB laser diode, thereby improving optical crosstalk.

In addition, the waveguide of the bidirectional module including the external cavity laser diode is formed by the SAG method, thereby simplifying the process.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention. .

Claims (6)

Bidirectional module consisting of a transmitter and a receiver, The transmitter includes a DFB region for oscillating an optical wavelength; A passive waveguide region located at one side of the DFB region; And a distributed feedback laser diode (DFB) having an external cavity located at one side of the passive waveguide and including a DFB reflection region having a grating, wherein the passive waveguide region adjusts the phase of the light reflected and returned from the DFB reflection region. Bidirectional module, characterized in that to cause a stable oscillation. delete The method of claim 1, wherein the receiver, An absorption waveguide region located at one side of the transmitter; A current blocking region located at one side of the absorption waveguide region; And And a photodiode region located at one side of the current blocking region. The bidirectional module according to claim 1, wherein a spot size converter is attached outside the DFB region. Forming a lower cladding layer over the substrate, the DFB region, the passive waveguide region, the DFB reflecting region, the absorbing waveguide region, the current blocking region, and the photodiode region being defined; Forming a diffraction grating in the lower cladding layer corresponding to the DFB region and the DFB reflecting region; Simultaneously forming a waveguide having a different wavelength for each region by a selective area growth (SAG) method on the lower cladding layer; And And forming an upper cladding layer on the waveguide. 6. The method of claim 5, wherein the step of forming the waveguide by the SAG method, the Bragg wavelength difference of the diffraction grating is adjusted.

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