KR100858217B1 - Optical modulator package for bi-directional data communication - Google Patents

Abstract

An optical modulator package for bi-directional data communication is provided to eliminate a micro-lens by minimizing a gap between a laser diode chip and a 45 degrees slope mirror and a gap a photodiode chip and the 45 degrees slope mirror. A laser diode chip(100), a 45 degrees slope mirror(200), and a receiving photodiode chip(500) are mounted in a package housing. The laser diode chip is fixed on a second sub-mount(300). The second sub-mount and the 45-degrees slope mirror are fixed on a first sub-mount(400). The receiving photodiode chip is installed at a lower part of the 45-degrees slope mirror. A slope of the 45-degrees slope mirror is coated with a single dielectric layer or plural dielectric layers having different refractive indexes in order to reflect a laser beam of a wavelength emitted from the laser diode chip, to emit the reflected laser beam to an external optical fiber, and to transmit the incident laser beam from the optical fiber of the package to the receiving photodiode chip.

Description

Optical modulator package for bi-directional data communication}

The present invention relates to an optical module package for bidirectional communication. In particular, an optical module package for bidirectional communication in which a laser diode chip, a 45 ° tilt mirror, and a photodiode chip for receiving are built in one package housing to simultaneously transmit and receive an optical signal. It is about.

Background Art In recent years, optical communication using light as a medium for information transmission has become common for large-capacity information transmission and high-speed information communication. In recent years, a 10 Gbps (giga bit per sec) electric signal can be easily converted into laser light using a semiconductor laser diode chip having a length of 0.3 mm and a length of about 0.3 mm, respectively. It is easy to convert the optical signal transmitted through the electric signal. Light is an energy wave with very peculiar characteristics. In order for several lights simultaneously in one region to interact with each other, the light to be interacted with must have the same wavelength or have the same light phase. In addition, the direction of travel shall coincide. Therefore, light is very inferior to each other, and the wavelength division multiplexing (WDM) optical communication that transmits light having various wavelengths simultaneously through one optical fiber by using the characteristics of the light is preferred. The optical communication of the WDM method is a very economical communication method in that the optical fiber, which is a signal transmission medium, can be shared, thereby reducing the cost of laying the optical fiber.

In recent years, fiber to the home (FTTH), which connects optical fiber to the inside of a subscriber's home, is becoming more common. In the FTTH method, the optical fiber is drawn inside the subscriber's home for optical communication, and the optical signal is generated inside the subscriber's home and the optical signal transmitted from the base station of the optical communication is converted into an electrical signal. Downlink optical communication is required. As a method of performing the uplink and downlink optical communication, there is a method of separately installing and using an optical fiber for processing an uplink optical signal and an optical fiber for processing a downlink optical signal, but this method causes waste of optical fibers. Therefore, recently, a bidirectional optical communication method for transmitting an uplink optical signal and a downlink optical signal through one strand of optical fiber has been widely adopted. Integrate the light-receiving element that receives the optical signal transmitted downward through the optical fiber and converts it into an electrical signal, and the optical transmission element that converts the electric signal into an optical signal and transmits it through the optical fiber so that optical coupling with one optical fiber occurs. Modules collectively referred to as BiDi module.

1 shows a structure of a conventional general BiDi module.

1, the wavelength of light emitted from the TO-type laser diode 4 installed in the BiDi module housing 1 and transmitting an optical signal upward to the optical fiber 2 is 1550 nm, and the optical fiber 2 is described. The wavelength of light transmitted downward from the light incident on the TO-type light receiving element 5 is assumed to be 1300 nm. In FIG. 1, the 45 ° filter 3 alternately deposits a dielectric film having a relatively high and low refractive index into a plurality of layers to transmit a wavelength of 1550 nm and a wavelength of 1300 nm to reflect the wavelength selectivity. It can be produced to have. Therefore, the laser light having a wavelength of 1550 nm emitted from the TO type laser diode 4 passes through the 45 ° filter 3 as it is, thereby converging the optical signal light to the optical fiber 2 and 1300 emitted from the optical fiber 2. The downward light having a wavelength of nm enters the TO-type light receiving element 5 with a 90 ° angle of travel in a 45 ° filter 3 reflecting light having a wavelength of 1300 nm. Therefore, by using the BiDi module, up and down transmission of signals is simultaneously performed using one optical fiber 2. However, the existing BiDi module is bulky by mounting two TO modules, such as the TO type laser diode 4 and the TO type light receiving element 5, and the optical fiber 2 and the TO type laser diode 4 As well as precise optical alignment of the optical fiber (2) and TO-type light receiving element (5) to be optically aligned, there is a problem that the assembly time and cost for the components for the alignment is increased.

In order to reduce the disadvantages of the conventional BiDi module as shown in FIG. 1, there has been research and development on an integrated BiDi module integrating a laser diode chip, a light receiving element, and a 45 ° filter in one TO type module. Yoon (IEEE PHOTONIC TECHNOLOGY LETTERS, VOL. 16, NO. 8, 2004, p1954) has a semiconductor laser diode chip, a photodiode chip as a light-receiving element, and a 45 ° filter mounted on a single board and assembled into a TO-type package. Yes. The size of the 45 ° filter used by them is approximately 1.2 mm in length and 0.6 mm in thickness. The laser light emitted from the laser diode chip is emitted with a full width at half maximum (FWHM) of about 30 to 40 degrees. Therefore, a lens is required between the semiconductor laser diode chip and the optical fiber to focus the light emitted from the laser diode chip on the cross section of the optical fiber. Since the size of the focusing lens is limited, the distance from the semiconductor laser diode chip of the conventional TO-type package to the lens is typically about 1.1 mm. In this case, the diameter of a lens that is commonly used is about 2 mm at maximum. Therefore, in order for the light emitted from the semiconductor laser diode chip to be focused well by the lens, it is advantageous that the size of the laser light projected on the lens is small, which can be achieved by shortening the length between the light output surface of the semiconductor laser diode chip and the lens. have. In a typical BiDi module, a lens is provided in each of the TO-type laser diode package and the TO-type photodiode package, so that the distance between the light output surface of the semiconductor laser diode chip and the light absorption layer of the photodiode chip from the lens is optimal. Will be set. However, due to the size of the 45 ° filter used in an integrated BiDi module integrating a semiconductor laser diode chip, a photo diode chip and a 45 ° filter on a single substrate, the distance from the laser diode chip to the lens is increased. The problem is that the light emitted from the chip becomes too large. Therefore, in order to solve this problem, a small size lens for reducing the divergence angle of the laser light is required on the substrate. This discussion applies equally to the downward signal light emitted from the optical fiber and incident on the photodiode chip. Therefore, in order to integrate a laser diode chip, a photodiode chip, and a 45 ° filter onto a single substrate, two small lenses called micro lenses must be added. The method of making the 45 ° filter thinner should be at least 1.2 mm long and 0.5 mm thick because the 45 ° filter is less stable when the 45 ° filter is placed on the substrate. In the case of using such a large 45 ° filter, the distance between the laser diode chip and the lens due to the size of the 45 ° filter is a difficult problem to solve, which further raises the need for a micro lens. In addition, since the additional microlens is attached, the bottom area of the substrate for attaching the laser diode chip, the photodiode chip, the 45 ° filter and the additional microlens is increased. According to the papers of Yoon et al., They have a floor area of 2.1 mm x 2.0 mm.

Another method of integrating a laser diode chip, a photodiode chip and a 45 ° filter on a single substrate using an additional microlens was presented by Shimura et al. (IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 16, AUGUST 15, 2006, p1738). Even in these methods, the distance between the laser diode chip and the 45 ° filter and the distance between the photodiode chip and the 45 ° filter are about 0.9 mm, which causes the problem of excessively large laser light. Additional microlenses are used between the diode chip and the 45 ° filter and between the photodiode chip and the 45 ° filter. See also Shimura et al. The substrate area for attaching a laser diode chip, a photodiode chip, a 45 ° filter and an additional microlens exceeds 2.0 mm x 2.0 mm.

As shown in the two reference papers described above, when a microlens is used, the optical path of the laser lights varies depending on the position of the additional microlens. Therefore, for high optical coupling efficiency with the optical fiber, the position of the laser diode chip and the photodiode chip, two micro lenses, and the 45 ° filter must be adjusted very precisely. In order to accurately attach the microlens in the correct position, the size of the microlens itself must also be adjusted very precisely, and the attaching method must also be able to secure a very high level of precision. Will be generated.

Accordingly, an object of the present invention is to solve the problems of the prior art, a laser diode chip, a photo diode chip and a 45 ° filter is integrated in one substrate to enable a two-way optical communication module to enable a two-way optical communication module In order to prevent the spread of the laser light emitted from the diode chip and the laser light emitted from the optical fiber and going to the photodiode chip, the micro lens inserted is deleted to make the alignment of the components easier. Therefore, it is possible to manufacture optical module package for both communication at low cost and to minimize the floor area where laser diode chip, photodiode chip and 45 ° filter are installed. To provide.

The present invention proposes a method of eliminating the need for a micro lens by minimizing the distance between the laser diode chip and the 45 ° filter and the distance between the photodiode chip and the 45 ° filter. To this end, the present invention fabricates a 45 ° tilt mirror for a very small 45 ° filter, and proposes a method of arranging a laser diode chip, a photo diode chip and a 45 ° tilt mirror, and precisely adjusting the position of the laser diode chip and the photo diode chip. By presenting this easy method, a laser diode chip, a photodiode chip, and a 45 ° inclined mirror are assembled on a single substrate, but a method for inexpensively implementing bidirectional optical communication without a microlens is presented. In addition, the present invention proposes a method of easily embedded in a small package such as TO56 by minimizing the floor area where the laser diode chip, photodiode chip and 45 ° tilt mirror are installed.

The optical module package for bidirectional communication according to the present invention can minimize the distance between the laser diode chip and the 45 ° inclination mirror and the distance between the photodiode chip and the 45 ° inclination mirror, eliminating the need for a microlens and thus eliminating the microlens. By removing such a microlens, it is possible to solve the problem of an optical path abnormal due to an abnormal mounting position of the microlens. In addition, in the conventional method, the receiving photodiode chip should be placed upright, but in the present invention, the laser diode chip and the receiving photodiode chip can be assembled in the form of lying down on the floor so that the position of the laser diode chip and the receiving photodiode chip can be assembled. The effect is very easy to adjust.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a schematic structural diagram of an optical module package for bidirectional communication according to an embodiment of the present invention, and FIG. 3 is a plan perspective view of the first submount.

As shown in FIG. 2, the optical module package for bidirectional communication according to the present invention has a wedge-shaped 45 ° inclined mirror 200 having an inclined surface having an inclination angle of 45 ° with respect to the bottom surface on one side of the first submount 400. ) Is installed and the second submount 300 is installed on the side of the 45 ° tilt mirror 200, the laser diode chip (45) on the inclined surface of the 45 ° tilt mirror 200 on the second submount 300. 100) is installed. In this case, the second submount 300 is formed to have an appearance opposite to the 45 ° inclined mirror 200 and is made to mesh with the inclined surface of the 45 ° inclined mirror 200 to allow the laser diode chip 100 to be inclined at 45 ° as much as 45 °. Assembled in a form that can be close to the inclined surface of 200).

As shown in FIG. 3, the first submount 400 is formed in a “c” shape and has a receiving photodiode chip 500 and a receiving photodiode chip submount 600 in a groove penetrating up and down. To be inserted and installed.

The inclined surface of the 45 ° inclined mirror 200 has a characteristic of reflecting light of a wavelength corresponding to the laser light emitted from the laser diode chip 100, and is emitted from an optical fiber not shown in the drawing to form a photodiode chip ( The laser light having a wavelength corresponding to the laser light traveling toward 500) is manufactured to have a transmission characteristic. In the present invention, a first photodiode chip for detecting an external optical signal transmitted through an optical fiber and a second photodiode chip for monitoring an operating state of the laser diode chip 100 are required. The first photodiode chip for detecting the photodiode chip 500 for receiving and the second photodiode chip for monitoring the operating state of the laser diode chip 100 are called the photodiode chip 700 for monitoring. In addition, hereinafter, the laser light emitted from the laser diode chip 100 has a wavelength of 1550 nm, and the laser light traveling from the optical fiber to the receiving photodiode chip 500 has a wavelength of 1300 nm. It is assumed that this wavelength classification is for convenience of explanation only, and is actually applied even if the wavelength is changed. . The laser light of 1550 nm emitted from the laser diode chip 100 is reflected by the 45 ° inclination mirror 200 in the module having the structure thus constructed, and the propagation direction is 90 ° to be transmitted to the upper optical fiber. Since the light has a reversible propagation path, the laser light having a wavelength of 1300 nm emitted from the optical fiber is 45 ° in a direction opposite to the progress of the laser light having a wavelength of 1550 nm traveling from the laser diode chip 100 to the optical fiber. Incident to the inclined mirror 200. Since the 45 ° inclined mirror 200 is transmitted to the 1300 nm laser light emitted from the optical fiber, the 1300 nm laser light arriving at the surface of the 45 ° inclined mirror 200 passes into the 45 ° inclined mirror 200. It is absorbed and proceeds. 45 ° inclined mirror 200 used in the present invention is made of silicon or glass that does not absorb the wavelength of the near infrared region of 1300nm or 1550nm as the base material of the 1300nm wavelength running through the 45 ° inclined mirror 200 The laser light passes through the 45 ° inclined mirror 200 and escapes to the back of the 45 ° inclined mirror 200. The laser light having a wavelength of 1300 nm escaped to the rear of the 45 ° inclined mirror 200 has the same traveling direction as the direction of travel before reaching the 45 ° inclined mirror 200 according to Snell's law. Accordingly, the laser light having a wavelength of 1300 nm transmitted through the 45 ° tilt mirror 200 escapes to the "C" groove of the first submount 400 having a "C" shape. The first submount 400 Since the receiving photodiode chip 500 is attached to the groove of the laser beam having a wavelength of 1300 nm generated from the optical fiber, the receiving photodiode chip 500 receives the optical signal transmitted and received.

The receiving photodiode chip 500 is installed on the receiving photodiode chip submount 600 which is installed on the bottom surface of the 'c'-shaped groove of the first submount 400, and the monitoring photodiode chip ( 700 is installed toward the laser diode chip 100 on one side of the monitoring photodiode chip submount 800 installed above the first submount 400.

Hereinafter, each configuration of the optical module package for bidirectional communication will be described. In order to facilitate understanding in describing each configuration of the present invention, patent application No. 2007-0026558 proposed by the present applicant in connection with the present invention will first be briefly described.

Figure 4 shows the process of manufacturing a 45 ° inclined mirror using the silicon base material proposed in the applicant's patent application No. 2007-0026558.

In the patent application, the semiconductor silicon wafer 2 is sliced from a semiconductor silicon ingot and coated with a photoresist 3, and then a 45 ° inclined surface 111 is formed by a wet etching method, and the original semiconductor silicon polished is polished. After coating the lower surface 4 of the wafer 2 with a metal having a high reflectance or a plurality of layers of dielectric thin films having different levels of refractive index, the semiconductor silicon wafer 2 having the reflective layer formed thereon is cut out by sawing or scribing or the like. 45 ° of inclined mirror (10) will be produced.

In addition, another patent application No. 2007-0120602 of the applicant has a shape of 45 ° inclined mirror according to the size cut out when separating the individual 45 ° inclined mirror from the semiconductor silicon wafer manufactured through the process of FIG. It has been shown that it can be changed in various forms.

Figure 6 shows the path of the light that depends on the direction of the light incident on the 45 ° tilt mirror.

In the 45 ° inclined mirror shown in FIG. 6, each surface of the 45 ° inclined mirror represented by ①, ②, ③, and ④ has a surface ① as shown in Patent Application No. 2007-0120602. The surface ② represents the sawed or scribed surface of the original silicon wafer, the surface ③ represents the etched surface of the original silicon wafer, and the surface ④ represents the polished top surface of the original silicon wafer.

Light from the upper side of the 45 ° inclined mirror passes through the surface of the 45 ° inclined mirror and proceeds to the inside of the inclined mirror, and the laser light penetrating the 45 ° inclined mirror reaches the 45 ° inclined mirror. Depending on the point, different paths will be taken.

As shown in FIG. 6, the light entering the "L" region travels inside the inclined mirror at an angle of 11.7 degrees with respect to the waterline of the inclined surface of the 45 inclined mirror according to Snell's law. When the light traveling inside the inclined mirror meets the lower surface of the inclined mirror, it has an angle of incidence of 33.3 ° with respect to the waterline of the inclined mirror. An incident angle of 33.3 ° is an incident angle corresponding to total reflection when the refractive index of silicon is 3.5 and the refractive index of air is 1. Therefore, the light incident to the "L" region totally reflects from the lower surface of the inclined mirror to reach the ② surface of the 45 ° inclined mirror and then escapes into the air.

Light incident in the vertical direction to the “H” region of the 45 ° inclined mirror is incident at an incidence angle of 45 ° with respect to the inclined plane repair of the inclined mirror. By Snell's law, the light that passes through the slope and travels inside the mirror has an angle of 11.7 ° with respect to the slope of the slope. When this light enters ④, it has an angle of incidence of 11.7 ° with respect to the vertical of ④, and the light escapes into the air with a vertical downward direction in the air.

As described above with reference to FIG. 4, the present applicant forms an inclined surface of a 45 ° inclined mirror on a flat lower surface of a semiconductor wafer such as silicon, and has a refractive index of a material and a structure for forming a reflective surface in the patent application No. 2007-0026558. Another multilayer dielectric thin film is presented. The technique of controlling reflectance and transmittance for specific wavelengths by depositing a dielectric thin film on a flat surface is a very general and well managed process, and thus the transmittance of the 45 ° mirror can be easily controlled. In addition, the applicant of the 2007-0120602 the anti-reflective deposition on the upper surface of the patterned silicon wafer to escape the laser light emitted from the laser diode chip embedded in the module escapes into the air without reflection from the back of the 45 ° tilt mirror Explained.

Hereinafter, a method of manufacturing a 45 ° inclined mirror according to an embodiment of the present invention will be described.

7 is a conceptual diagram illustrating a process of fabricating a 45 ° inclined mirror having wavelength selectivity using a semiconductor silicon wafer according to an embodiment of the present invention.

First, the process of causing the (111) surface of the semiconductor silicon wafer to appear as shown in FIG. 7A is described in detail in the above-described patent applications Nos. 2007-0026558 and 2007-0120602, which will be briefly described in the present invention. First, the semiconductor silicon wafer is cut out at an inclined angle of 9.74 ° from the semiconductor silicon ingot to the (001) plane, a part of the top surface of the cut semiconductor silicon wafer is coated with photoresist, and then the photoresist of the portion to be etched is removed by a photolithography method. When the semiconductor silicon of the portion where the photoresist is removed is etched using the anisotropic etching solution, the etch exposed side surface of the semiconductor silicon wafer becomes the (111) plane. In this case, the etched (111) plane has an inclination angle of 54.74 ° and is cut off to have an inclination angle of 9.74 ° with the (001) plane when the semiconductor silicon wafer is cut out from the ingot. Has a horizontal plane of the semiconductor silicon wafer 2 and an inclination angle of 45.00 ° and 64.48 °, respectively.

Subsequently, as shown in FIG. 7B, a laser diode chip mounted in the module on the lower surface of the exposed wafer having two (111) surfaces having an inclination angle of 45.00 ° and 64.48 ° with respect to the bottom surface of the semiconductor silicon wafer. A dielectric thin film having a characteristic of reflecting with respect to the wavelength of the laser light emitted from and having a characteristic of transmitting with respect to the wavelength of the laser light emitted from the optical fiber is deposited. The dielectric thin film having the wavelength selectivity may be obtained by alternately depositing materials having different refractive indices, but in general, the dielectric thin film may be formed by alternately depositing TiO2 having a refractive index of about 2.2 to 2.8 and SiO2 having a refractive index of 1.35. Thin films can be deposited. Filters having wavelength selectivity, which are fabricated by alternately depositing heterogeneous materials having different refractive indices on glass substrates, have been widely adopted in bidirectional optical communication modules having an existing structure.

In FIG. 7C, when the light emitted from the optical fiber escapes the silicon mirror and proceeds to the air on the upper surface of the silicon wafer, antireflection deposition is performed so that reflection does not occur at the interface between the silicon and the air. Such antireflection deposition can be obtained by controlling the thickness of the above-described dielectric layer of TiO 2 / SiO 2, where laser light emitted from the optical fiber and transmitted into the silicon gradient mirror escapes to the upper surface of the original silicon substrate. Since the upper surface of the semiconductor silicon wafer is a very smooth surface by polishing, it is very easy to deposit a dielectric thin film on such a surface.

The semiconductor silicon wafer thus manufactured is cut out to an appropriate size as shown in (d) of FIG. 7 and then placed so that the etched (111) surface is positioned downward. From the laser diode chip embedded in the module as shown in (e) of FIG. The laser light emitted is reflected, and the laser light emitted from the optical fiber is transmitted to the inside of the inclined mirror and is completed as a 45 ° inclined mirror having a function of discharging into the air through the back of the inclined mirror. In addition, if the 45 ° inclined mirror manufactured as shown in (e) of FIG. 7 is turned upside down as shown in FIG. Can be the second submount. In this case, in order to simply use as a submount of the laser diode chip as shown in (f) of FIG. 7, the process of depositing the dielectric thin film of FIGS. 7b and 7c may be omitted.

Figure 8 shows a three-dimensional view of the 45 ° inclined mirror manufactured by the process of Figure 7 described above.

In the embodiment of the present invention, since the wavelength of the laser light emitted from the laser diode chip mounted in the module is assumed to be 1550 nm and the wavelength of the laser light emitted from the optical fiber is 1300 nm, the upward direction of the 45 ° tilt mirror in FIG. 8 is assumed. The 45 ° inclined plane having the characteristics of reflection has a characteristic of reflection with respect to a wavelength of 1550 nm, and has a characteristic of transmitting with a wavelength of 1300 nm. In addition, the 45 ° inclined plane in the downward direction opposite to the upward inclined plane is in a state where anti-reflective deposition is performed so that 1300 nm laser light emitted from the optical fiber does not cause reflection at the interface between silicon and air.

9 is a conceptual diagram illustrating a process of mounting a 45 ° inclined mirror manufactured by the above process.

As shown in FIG. 9, the first submount 400 has a "-" groove in which a receiving photodiode chip 500 can be inserted into one side thereof, and the first submount 400 is formed therein. It is preferable to manufacture the silicon which is inexpensive and can be easily produced in the "c" shape by a dry or wet etching process.

A 45 ° inclined mirror 200, which is a wavelength selective reflection / transmission mirror, is installed on an upper portion of the first submount 400 having a “?” Shape, and the 45 ° inclined mirror 200 has a first submount 400. A part of the lower surface is installed to be in the "c" groove of). In addition, a second submount 300 having the laser diode chip 100 attached to the upper side of the first submount 400 is installed, wherein the second submount 300 and the 45 ° tilt mirror 200 are installed. The inclined surfaces are installed to be engaged with each other. The receiving photodiode chip submount 600 having the receiving photodiode chip 500 attached thereon is inserted into and coupled to the “c” -shaped groove of the first submount 400. Thereafter, in order to monitor the operating state of the laser diode chip 100, the monitoring photodiode chip 700 and the monitoring photodiode chip submount 800, which are not shown in the drawing, are installed on the first submount 400. The bidirectional optical communication module having the structure as shown in FIG. 2 is completed.

Hereinafter, the light traveling path of the bidirectional optical communication module manufactured by the above method will be described in more detail.

10 is a conceptual diagram showing a path of the laser light emitted from the laser diode chip according to an embodiment of the present invention, Figure 11 is a conceptual diagram showing the path of the laser light emitted from the external optical fiber, Figure 12 is such a bidirectional Simultaneously shows the path of laser light for communication.

Edge emitting laser diode chips, which are widely used for optical communication, emit laser light in opposite directions from the front and rear surfaces of the laser diode chip. Conventional laser diode chips are tuned so that the intensity of the laser light from the front is less than several times to several tens of times greater than the intensity of the laser light from the rear to use the maximum light output for light transmission. The front laser light of the laser diode chip is focused on the optical fiber outside the package to be used for information transmission, and the laser light emitted from the rear is used to drive the photodiode chip for monitoring to monitor the operation state of the laser. Therefore, in the conventional edge emitting laser diode chip, as shown in FIG. 10, laser light is emitted from the front and rear surfaces of the laser diode chip 100.

In the embodiment of the present invention, it is assumed that the laser diode chip 100 emits laser light having a wavelength of 1550 nm, and the 45 ° tilt mirror 200 has a property of reflecting the laser light having a wavelength of 1550 nm. Therefore, the laser light emitted from the front surface of the laser diode chip 100 is reflected by the 45 ° tilt mirror 200 to proceed toward the upper direction of the module. This divergent form of laser light cannot be focused on the optical fiber. Therefore, a lens for focusing the emitted laser light is required. Since this focusing lens is a lens that is commonly used, a detailed description thereof will be omitted. The laser diode chip 100 diverges from the 45 ° tilt mirror 200 and is diverged toward the upper side of the module. The laser light is focused on the optical fiber through the lens not shown in the drawing to perform the optical transmission. Done. At this time, since the 45 ° inclined mirror 200 has a reflection characteristic with respect to 1550 nm, it cannot proceed toward the receiving photodiode chip 500. If some 1550 nm laser light passes through the 45 ° inclined mirror 200, the laser light having a wavelength of 1550 nm may not travel in the direction of the receiving photodiode chip 500 for the reason described below.

Since the present invention is a bidirectional optical communication module for transmitting and receiving information using a single optical fiber, the laser light having a wavelength of 1300 nm transmitted toward the receiving photodiode chip 500 of the present invention is 1550 nm emitted from the laser diode chip 100. It is the same optical fiber as the optical fiber that focuses the laser light of the wavelength.

As shown in FIG. 11, the laser light of 1300 nm wavelength emitted from the optical fiber by the reversibility of the light path reaches the 45 ° mirror 200 along the reverse path of the laser light of 1550 nm wavelength. Since the 45 ° inclined mirror 200 has a property of transmitting about 1300 nm wavelength, laser light having a wavelength of 1300 nm emitted from the optical fiber and reaching the 45 ° inclined mirror 200 does not reflect toward the laser diode chip 100. It will pass through the inclined mirror (200). Since silicon has an absorption of 10 ⁻⁴ / cm or less for light having a wavelength of 1300 nm to 1550 nm, light absorption through the penetration of silicon having a thickness of about 200 μm to 300 μm is very small. Therefore, the light transmitted into the 45 ° mirror 200 is refracted according to each incident angle component in accordance with Snell's law to proceed inside the silicon. The laser light having a wavelength of 1300 nm transmitted through the silicon gradient mirror 200 escapes into the air at the interface of silicon / air. In this case, the rear surface of the 45 ° tilt mirror 200 has the laser light of 1300 nm wavelength through the process of FIG. 7. The antireflective coating is applied to the silicon / air interface to allow air to penetrate without reflection. When the silicon proceeds to air, the laser light is refracted again to restore the direction of travel it had before it arrived at the 45 ° tilt mirror 200.

As shown in FIGS. 10 to 12, laser light having a wavelength of 1550 nm emitted from the laser diode chip 100 using the same 45 ° inclination mirror 200 is reflected from the 45 ° inclination mirror 200 to the optical fiber. The laser light having a wavelength of 1300 nm emitted from an optical fiber in which the laser light having a wavelength of 1550 nm is focused is transmitted through the 45 ° inclined mirror 200 and focused on the receiving photodiode chip 500.

In the above process, the laser light having a wavelength of 1550 nm emitted from the laser diode chip 100 does not proceed to the receiving photodiode chip 500. In some cases, the laser light having a wavelength of 1550 nm may be inclined at 45 °. It can penetrate 200. FIG. 13 illustrates a path of laser light generated when a part of the laser light emitted from the laser diode chip passes through the 45 ° mirror.

As shown in FIG. 13, even though a portion of the laser light emitted from the laser diode chip 100 passes through the 45 ° inclined mirror 200, it cannot proceed in the direction of the receiving photodiode chip 500. For the sake of convenience, only the components having an angle of incidence of 45 ° on the 45 ° tilt mirror 200 will be considered. When both the laser light emitted from the laser diode chip 100 and the laser light emitted from the optical fiber are incident on the 45 ° inclined mirror 200 with a 45 ° incidence angle, the repair of the 45 ° inclined mirror 200 is used as a reference point. Since the laser light emitted from the laser diode chip 100 enters the second quadrant, the refracted light proceeds to the fourth quadrant. In addition, since the laser light entering the 45 ° inclined mirror 200 at the incident angle of 45 ° proceeds in the first quadrant, the refracted light proceeds in the third quadrant. The refraction angle at this time is approximately 11.7 °, which is obtained according to Snell's law when the refractive index of silicon is 3.5. Of the laser light reaching the rear of the 45 ° mirror 200, the laser light originating from the laser diode chip 100 enters the silicon / air interface into two quadrants again, so the laser light that is refracted becomes quadrant four. Is the same as the propagation direction that the laser light had before reaching the 45 ° mirror 200. In accordance with such a discussion, the laser light, starting from the optical fiber and proceeding vertically downward, passes through the 45 ° inclined mirror 200 and proceeds back to the original vertical downward. That is, laser light having a wavelength of 1550 nm emitted from the embedded laser diode chip 100 does not travel in the direction of the receiving photodiode chip 500 even though it passes through the 45 ° mirror 200.

The optical module package for bidirectional communication manufactured by the above method is not suitable for users because each component protrudes outward. Therefore, various types of package housings have been developed that contain a laser diode chip for communication or a photodiode chip for light reception.

14 illustrates an example of a TO-type package housing, and FIG. 15 is a perspective view of an optical module package for bidirectional communication mounted on a TO-type package housing according to an exemplary embodiment of the present invention.

As shown in FIGS. 14 and 15, the TO-type package housing forms a plurality of pupils in a circular stem base 13 of a metal mainly composed of Kovar or iron (Fe). After inserting the electrode pin 15 into the pupil, the electrode pin 15 and the stem base 13 are insulated and sealed using a glass bead 14.

The first submount 400, the second submount 300, the laser diode chip 100, the 45 ° tilt mirror 200, the photodiode chip 500 for receiving, are formed on the stem base 13. An optical module in which the receiving photodiode chip submount 600, the monitoring photodiode chip 700, the monitoring photodiode chip submount 800, and the like are installed is installed.

In addition, a hole is formed in an upper portion of the stem base 13 of this type, and the package housing is manufactured by covering a cap 11 made of metal sealed with a window glass 12 made of glass. This type of package housing is the most suitable type of package housing for mounting the bidirectional module of the present invention because the laser light should be perpendicular to the bottom surface of the stem base 13 on which the optical components such as the laser diode chip 100 are placed. One.

The optical module package for bidirectional communication of the present invention has been described for the convenience of description including a laser diode chip 100, a monitoring photodiode chip 700, and a receiving photodiode chip 500, which are main active components, but in addition to the receiving port Preamplifiers and corresponding capacitors, such as a trans impedance amplifier (TIA) for amplifying the photocurrent received at the diode chip 500, may be added within the TO package housing. In addition, since the laser diode chip 100 is very sensitive to temperature, it may be necessary to control the temperature of the laser diode chip 100 by embedding a thermo electric cooler.

FIG. 16 is a perspective view illustrating an optical module package for bidirectional communication including a thermoelectric device in such a TO-type package housing. FIG.

As shown in FIG. 16, the laser diode chip 100, the monitoring photodiode chip 700, the receiving photodiode chip 500, and the like are simply disposed on the thermoelectric element 16. The temperature can be adjusted. When the thermoelectric element 16 is embedded, a thermistor 17 for measuring the temperature of the upper portion of the thermoelectric element on which the laser diode chip 100 is placed is preferably embedded.

In an embodiment of the present invention, the laser light at 1550 nm wavelength is typically a powerful energy of 0 dBm or more for transmission, whereas the received laser light is a very weak signal, typically -10 dBm or less. Therefore, a part of the laser light having a wavelength of 1550 nm emitted from the embedded laser diode chip 100 may be diffusely reflected inside the module, and such diffusely reflected light may be received by the receiving photodiode chip 500.

17 is a layout view of a receiving photodiode chip for preventing such diffusely reflected light from being received by the receiving photodiode chip.

In general, a receiving photodiode chip 500 for detecting a near infrared wavelength band having a wavelength of 1300 nm or 1550 nm uses InGaAs as a light absorption layer on an InP substrate 510. The InP substrate 510 has an energy bandgap of approximately 1.35 eV and does not absorb light having a wavelength of 1300 nm or 1550 nm. Therefore, the active region 520 of the receiving photodiode chip 500 is directed toward the bottom of the package, and the anode and cathode electrodes of the receiving photodiode chip 500 are positioned below the receiving photodiode chip 500. It is electrically connected in a flip chip bonding method through the submount 600 and the metal ball 540, but reflects to the receiving photodiode substrate surface 530 facing upward for 1550 nm wavelength and transmits for 1300 nm wavelength. When the dielectric thin film 531 is deposited to have the characteristics of 1550 nm laser light that is diffusely reflected, it is possible to minimize the detection of the photodiode chip 500 for reception.

On the other hand, the photodiode chip 500 generally displays the active region 520 through the surface step etching or the coating of the metal ring, but does not display the substrate surface 530 of the photodiode chip 500. It is common. However, when the photodiode chip 500 and the submount 600 block are optically aligned using the flip chip bonding method, the optical alignment becomes difficult if the active region 520 is not displayed on the substrate surface 530. This can be prevented by depositing a metal thin film on the substrate surface 530 of the photodiode chip 500 except for the same position as the active region 520. FIG. 18 is a photodiode chip according to an embodiment of the present invention. This is an example in which the photoactive region is displayed on the substrate surface.

As illustrated in FIG. 18, the substrate surface 530 of the photodiode chip 500 is deposited on the metal thin film 532, but the region opposite to the active region 520 is not deposited on the metal thin film 532. Because of the difference in reflectance between the substrate surface 530 and the position of the photoactive region 520, the photodiode chip 500 may be easily aligned. In addition, since the received optical signal has a vertical downward component and is incident on the opening of the metal thin film 532 on the active region 520, the received optical signal is easily incident on the active region 520 of the photodiode chip 500. Light diffused from the laser diode chip 100 and diffusely reflected inside the module has various paths and angles. The diffusely reflected laser lights entering the metal thin film 532 of the photodiode chip 500 are directed to the photodiode chip 500. Since the laser beam is diffusely reflected in the module, the signal leakage due to the incident light is directly incident to the photodiode chip 500. Metal materials for coating the substrate surface 530 of the photodiode chip 500 with the metal thin film 532 may be titanium, platinum, gold, silver, aluminum, copper, or the like. Combinations are also possible.

In the above-described embodiment of the present invention has been described by taking a 45 ° inclined mirror 200 with a silicon as an example, it is obvious that even if the base material of the 45 ° inclined mirror 200 is glass.

In addition, although the laser light emitted from the laser diode chip 100 embedded in the embodiment of the present invention has a wavelength of 1550 nm, and the laser light received from the optical fiber has a wavelength of 1300 nm, the two wavelengths are interchanged. It is apparent that the present invention can also be applied to any combination of wavelengths that can be separated from the 45 ° tilt mirror 200.

In addition, although the TO-type package is shown in the form of the main package housing of the present invention, it is, of course, applicable to a conventional butterfly, mini deal, mini-flat package.

1 is a structural diagram of a conventional general BiDi module,

2 is an overall structural diagram of an optical module package for bidirectional communication according to the present invention;

3 is a top perspective view of a first submount in accordance with the present invention;

4 is a conceptual diagram illustrating a process of manufacturing a 45 ° inclined mirror using a silicon base material proposed in the present applicant's patent application No. 2007-0026558,

5 is an example of various shapes of a 45 ° inclined mirror manufactured by the applicant of the present patent application No. 2007-0120602,

Figure 6 is a path diagram of light that depends on the direction of the light incident on the 45 ° tilt mirror according to the present invention,

7 is a conceptual diagram illustrating a process of manufacturing a 45 ° inclined mirror having wavelength selectivity using a semiconductor silicon wafer according to the present invention;

8 is a three-dimensional view of the 45 ° inclined mirror according to the present invention,

9 is a conceptual diagram showing a process of mounting a 45 ° tilt mirror in the optical module according to the present invention,

10 is a conceptual diagram showing a path of a laser light emitted from a laser diode chip according to the present invention;

11 is a conceptual diagram showing a propagation path of laser light emitted from an external optical fiber according to the present invention;

12 is a conceptual diagram showing a traveling path of a laser light for bidirectional communication simultaneously according to the present invention;

13 is a path diagram of laser light generated when a portion of the laser light emitted from the diode chip according to the present invention passes through a 45 ° mirror;

14 is an example of a conventional TO-type package housing,

15 is a perspective view of an optical module package for bidirectional communication mounted on a TO-type package housing according to the present invention;

16 is a perspective view of an optical module package for bidirectional communication including a thermoelectric element in a TO-type package housing according to the present invention;

17 is a layout view of a receiving photodiode chip for preventing the diffused light from being received by the receiving photodiode chip according to the present invention;

18 is an example in which the photoactive region is displayed on the substrate surface of the photodiode chip according to the present invention.

※ Explanation of codes for main parts of drawing

100: laser diode chip 200: 45 ° tilt mirror

300: second submount 400: first submount

500: Receiving Photodiode Chip

600: Photodiode Chip Submount for Reception

700: Surveillance Photodiode Chip

800: Surveillance Photodiode Chip Submount

10: package housing 11: cap

12: window glass 13: stem base

14 glass bead 15 electrode

16: thermoelectric element 17: thermistor

Claims (20)

In the optical module package for bidirectional communication in which the laser diode chip 100, the 45 ° tilt mirror 200, and the receiving photodiode chip 500 are embedded in one package housing, The laser diode chip 100 is fixedly installed on the second submount 300, and the second submount 300 and the 45 ° inclined mirror 200 are fixedly installed on the first submount 400. The receiving photodiode chip 500 is installed below the 45 ° tilt mirror 200, The inclined surface of the 45 ° inclined mirror 200 reflects the laser light of the wavelength emitted from the laser diode chip 100 to be emitted to the optical fiber outside the package, and the laser light of the wavelength incident from the optical fiber outside the package transmits through The optical module package for bidirectional communication, characterized in that the coating is coated with a single layer of a dielectric thin film or a multi-layer dielectric thin film of different refractive index so that it can be transferred to the credit photodiode chip (500). The method according to claim 1, The optical module package for bidirectional communication, characterized in that the monitoring photodiode chip 700 for monitoring the operating state of the laser diode chip 100 is installed in the bidirectional communication optical module package. The method according to claim 2, The laser diode chip 100, the 45 ° tilt mirror 200, the monitoring photodiode chip 700, and the receiving photodiode chip 500 are installed on the thermoelectric element 16. Modular package. The method according to claim 1, The optical module package for bidirectional communication, characterized in that the preamplifier for amplifying the optical signal received through the photodiode chip 500 for receiving the bidirectional communication. delete The method according to claim 1, The first sub-mount 400 is an optical module package for bidirectional communication, characterized in that the groove formed in the "c" shape to accommodate the photodiode chip 500 for receiving. The method according to claim 6, The 45 ° inclined mirror 200 is an optical module package for bidirectional communication, characterized in that the lower portion is installed on the upper portion of the "c" shaped groove of the first submount 400. The method according to claim 1, The second submount (300) is an optical module package for bidirectional communication, characterized in that installed on top of the first submount 400 to engage the inclined surface of the 45 ° tilt mirror (200). The method according to claim 1, The reception photodiode chip 500 is disposed so that the active region 520 faces the bottom, and is generated from the laser diode chip 100 embedded in the upper substrate surface 530 of the reception photodiode chip 500. An optical module package for bidirectional communication, characterized in that a dielectric thin film (531) is deposited and coated so as to have reflection characteristics with respect to a laser light wavelength and transmission characteristics with respect to an external input laser wavelength received from an optical fiber. The method according to claim 9, The receiving photodiode chip 500 is an optical module package for bidirectional communication, characterized in that coupled to the receiving photodiode chip submount 600 through flip chip bonding. The method according to claim 1, The receiving photodiode chip 500 is disposed such that the active region 520 faces the bottom, and the position of the active region 520 is displayed on the upper substrate surface 530 of the receiving photodiode chip 500. An optical module package for bidirectional communication. The method according to claim 11, A metal thin film 532 is deposited on the upper substrate surface 530 of the receiving photodiode chip 500, but the metal thin film deposition is omitted at a position corresponding to the lower active region 520. Optical module package for bidirectional communication, characterized in that the location is displayed. The method according to claim 1, The package housing is an optical module package for bidirectional communication, characterized in that the TO-type package housing. The method according to claim 1, The 45 ° inclined mirror 200 is formed by forming an inclined surface having a predetermined angle with respect to the lower surface of the wafer by etching from a semiconductor wafer, and depositing a reflective metal material or a dielectric thin film on the upper and lower surfaces of the polished wafer instead of the inclined surface. Optical module package for bidirectional communication, characterized in that. The method according to claim 14, The 45 ° tilt mirror 200 Slicing the semiconductor wafer 2 from the semiconductor ingot and applying it to the photoresist 3 to form a 45 ° inclined surface 111 by a wet etching method; Forming a coating layer by depositing a dielectric thin film having wavelength selective transmission reflection property on a lower surface of the semiconductor wafer not including the inclined surface (111); The optical module package for bidirectional communication, characterized in that the dielectric thin film coated semiconductor wafer (2) is cut into a 45 ° mirror (200). The method according to claim 15, The 45 ° inclined mirror 200 is deposited on the upper surface of the semiconductor wafer including the inclined surface by depositing a dielectric thin film to have a reflectance lower than the reflection of the semiconductor wafer and the air interface with respect to the wavelength transmitted through the 45 ° inclined mirror 200. The optical module package for bidirectional communication, characterized in that forming. The method according to any one of claims 14 to 16, And the dielectric thin film is formed by alternately depositing a plurality of dielectric thin films having different refractive indices. The method according to claim 14, The 45 ° tilt mirror 200 is the base material of the optical module package for bidirectional communication, characterized in that the silicon or glass. The method according to claim 1, The second submount 300 is an optical module package for bidirectional communication, characterized in that the same structure as the 45 ° tilt mirror (200). The method according to claim 1, The second submount 300 After slicing the semiconductor wafer 2 from the semiconductor ingot and applying it to the photoresist 3, a 45 ° inclined surface 111 is formed by a wet etching method. And cutting the etched semiconductor wafer (2) into a second submount (300) having one surface having an inclination angle of 45 °.

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