KR100532183B1 - Optical probe and apparatus for measuring characteristic of planar optical device using the same - Google Patents

Abstract

An optical probe for inputting / outputting an optical signal using an optical fiber to a planar optical waveguide device fabricated on a wafer, and an apparatus for measuring characteristics of the planar optical device using the same. The biggest feature of the present invention is to put an optical signal on the surface of the planar optical element to input or output the optical signal to the optical probe which can fold the direction of the optical signal 90 degrees without loss. Therefore, according to the present invention, the optical characteristics of the device can be measured before processing the planar optical waveguide device fabricated on the wafer into a single device, thereby reducing the processing cost, and the wafer by one alignment of the optical probe and the wafer. The optical characteristics of all the above-mentioned planar waveguide devices can be measured, thereby reducing the measurement cost by reducing the alignment time.

Description

Optical probe and apparatus for measuring characteristic of planar optical device using the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical probe and an apparatus for measuring characteristics of planar optical devices using the same, and particularly, an optical probe that contributes to the reduction of packaging cost by enabling the measurement of the characteristics before the packaging process of the planar optical devices. The present invention relates to a characteristic measuring device of a planar optical device.

1 (a) to (c) is a view showing a manufacturing process of a planar optical waveguide device according to the prior art. In order to fabricate a planar waveguide device such as a 1x2 coupler, a plurality of identical unit planar waveguide devices 110 are formed on the silicon wafer 100 using a semiconductor device manufacturing process. This is shown in Figure 1 (a). Next, as shown in FIG. 1B, each unit plane optical waveguide element 110 is cut, and optical polishing is applied to the cut plane to reduce the loss of the input / output optical signal. Subsequently, as shown in FIG. 1C, the optical fiber arrays 120 and 120 ′ having connectors at the input / output ends are precisely aligned to minimize the coupling loss at the input / output ends, and then the optical fiber is used by using an adhesive such as epoxy. A package for bonding the arrays 120 and 120 'to the planar waveguide device is performed.

In the prior art, after the packaging process, the optical characteristics of the planar waveguide device are measured to determine the pass / fail of the device. However, according to this method, expensive equipment and technicians must precisely align the optical fiber arrays 120 and 120 'and the planar optical waveguide element 110 within a 1 to 2 占 퐉 error, and an expensive package for packaging is required. Consumables (eg, optical fiber arrays and bonding epoxy) are time consuming. For this reason, there arises a problem that whether the unit plane optical waveguide device is defective is confirmed only after the packaging process is performed after the formation of the planar optical waveguide device by the semiconductor process. That is, additional cost and time are required because the packaging process, which takes a significant portion of the cost of the planar waveguide device, is applied only to the defective unit planar waveguide device. Therefore, in order to mass-produce a planar waveguide device, it is necessary to develop and apply a process for selecting a planar waveguide device on a wafer as in a method applied to a manufacturing process of a semiconductor device such as a DRAM. However, when using the method of measuring the optical characteristics of the unit planar optical device using the optical fiber array as in the prior art, there is a disadvantage that the planar optical device placed on the wafer must be cut.

In addition, since the numerical aperture of the optical fiber array is low, as shown in FIG. 2, the optical waveguide 112 of the core 122 and the planar optical waveguide element of the optical fiber array using precision alignment equipment (not shown). Cores 114 should be aligned to within a few micrometers.

Accordingly, an object of the present invention is to provide an optical probe and a planar optical device using the same, in which the optical properties of the unit planar optical device manufactured on the wafer are measured without completely cutting or packaging the planar optical device. It is to provide a characteristic measuring device.

Another object of the present invention is to provide an optical probe and an apparatus for measuring the characteristics of a planar optical device using the same, which can measure the optical characteristics of the planar optical device without precise alignment.

According to an aspect of the present invention, there is provided an optical probe comprising: an end portion at which an input or an output of an optical signal is made; Characterized in that the optical fiber having the other end of the reflective surface for refracting the optical axis of the optical signal approximately 90 degrees.

In the optical probe, the other end may be inclined to be inclined with respect to the axis of the optical fiber so that light passing through the core of the optical fiber is incident at a critical angle at which total reflection is made.

Alternatively, the reflective surface of the other end may be made of a metal coating having excellent reflection characteristics.

Furthermore, it is preferable to select a multimode optical fiber as the optical fiber constituting the optical probe.

According to an aspect of the present invention, there is provided an apparatus for measuring characteristics of a planar optical device, including: a light source; After receiving the optical signal from the light source to its one end, the optical light probe for the input light for refracting the optical axis of the optical signal by approximately 90 degrees on the reflection surface of the other end to enter the input terminal of the planar optical element to be measured Wow; After receiving the optical signal from the output terminal of the planar optical element through its side, the output light for outputting the optical axis of the optical signal in the reflection surface of the other end of about 90 degrees to one end of its own A probe; And a sensing device for sensing an optical signal from the optical probe for output light.

In the characteristic measuring apparatus of the planar optical element, it is preferable to further include an alignment mechanism for aligning the optical probe for input light and the optical probe for output light, respectively.

In addition, adjacent to the other end of the optical probe for the input light and the optical probe for the output light to add a separate optical fiber in parallel with each other and the optical probe for the output light so that the separate optical fiber to act as a cylindrical lens. More preferred.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention. In the drawings, the same reference numerals denote the same components, and redundant description thereof will be omitted.

3 is a schematic diagram of an optical probe 300 for input light according to an embodiment of the present invention. The optical probe 300 for input light is used to input an optical signal to a characteristic measurement target device (not shown) such as a planar optical waveguide, and the optical fiber 310 is fixed by a holder 320 and the optical fiber 310 Input light enters through one end of the optical fiber 310, and the other end of the optical fiber 310 is cut to have a reflective surface 312 formed of an inclined surface inclined approximately 45 degrees with respect to the direction in which the optical signal travels. The reason why the inclined surface is formed at the other end of the optical fiber 310 is that the optical signal traveling through the core 314 of the optical fiber 310 is characterized by a total reflection phenomenon that occurs at the interface between the optical fiber and air without loss of characteristics in the form of output light. In order to be incident toward the device. More specifically, since the total reflection critical angle causing total reflection at the interface between the optical fiber having an effective refractive index of 1.468 and the air having a refractive index of 1.0 is approximately 43 degrees, the angle of the inclined surface is set so that the optical signal is incident on the inclined surface at an angle larger than this angle. The inclined surface then acts as a mirror with high reflectivity. However, when index matching oil is used between an optical fiber and an element to be measured such as a planar optical waveguide to reduce the coupling loss, the total reflection critical angle may be greater than 45 degrees, thereby causing the total reflection phenomenon to disappear. Therefore, a reflective surface having a reflectance of 90% or more may be formed by coating a metal thin film having a high reflectance on the inclined surface. In the optical probe 300 for the input light having the structure as described above, when the optical signal propagated through the optical fiber 310 reaches the other end, the optical signal is rotated at 90 degrees with little loss due to reflection, and then exits the optical fiber 310 to input the characteristic terminal of the characteristic measurement element. Proceed into the air on the side. Reference numeral 316 not described in FIG. 3 denotes a clad of an optical fiber.

In general, when the optical signal is input to the planar waveguide using the optical fiber, the coupling loss increases as the mode size of the optical signal is larger than the mode size of the planar waveguide. Instead, the coupling loss depends on the x and y axes. Decreases. Therefore, for low coupling loss, as shown in FIG. 2, the optical fiber is vertically cut and closely attached to the planar optical waveguide to make the mode sizes of each other similar, and the precision alignment equipment is used to precisely align the center in the x and y axis directions with micrometer or less precision. do.

FIG. 5 is a view illustrating a comparison of mode sizes according to an interval between an end of an optical fiber 310 and a planar optical waveguide in the optical probe for input light shown in FIG. 3. Referring to FIG. 5, since the optical signal deviating from the optical fiber is not parallel light, the mode size of the optical signal becomes larger as the distance D traveling in the air becomes longer. Therefore, as the distance D increases, the coupling loss increases and the dependence of the coupling loss on the x and y axes decreases. Since the optical probe of the present invention is used for the purpose of quickly measuring the basic optical characteristics of devices such as planar optical waveguides and determining defects, even if there is some coupling loss, the mode size of the optical signal deviated from the optical fiber is increased. You can also make the x and y axes less aligned.

4 is a view partially showing an optical probe for input light according to another embodiment of the present invention. Referring to FIG. 4, in order to stably input an optical signal to a measurement target element (not shown) such as a planar optical waveguide, an optical fiber 330 having the same configuration is added to the optical fiber 310 of the optical probe for input light. In this way, the optical fiber 330 may serve as a cylindrical lens having two spherical interfaces in the x-axis direction. Therefore, the optical signal deviating from the optical fiber forms parallel light in which a constant magnitude is maintained in the x-axis direction, and is maintained in a state where the accuracy of alignment required in the x-axis direction is low regardless of the distance. Therefore, when the input terminal and the optical fiber of the device to be measured, such as a planar optical waveguide, are coupled to each other, the precision required for alignment of the x-axis and the z-axis without increasing the coupling loss is reduced to about tens of micrometers.

FIG. 6 is a view showing a comparison of mode sizes according to the spacing between the ends of the optical fiber 330 having the same configuration and the planar optical waveguide, which are parallel to the optical fiber 310 of the optical probe for input light shown in FIG. 3. Unlike in FIG. 5, in FIG. 6, even if the distance D of the optical signal travels in the air becomes long, the mode size of the optical signal does not change significantly, because the optical fibers 310 and 330 have a spherical interface ( This is because the signal light is converted into parallel light by acting as a cylindrical lens having a spherical interface. Reference numeral 334 not described in FIG. 6 is an additional core of the optical fiber 330.

7 is a schematic diagram of an optical probe 350 for output light according to an embodiment of the present invention. The optical probe 350 for output light is used to transmit an optical signal to a sensing device through a signal light output from an output terminal of a characteristic measurement target device (not shown) such as a planar optical waveguide, and a plurality of optical fibers 360 are provided on the holder 370. It is fixed by. The plurality of optical fibers as described above is intended to receive optical signals at once when the number of output stages of the planar optical waveguide is large. In addition, each optical fiber 360 outputs signal light through one end thereof, and has an inclined reflecting surface 362 at its other end as described in detail with reference to FIG. 3. Therefore, when an optical signal propagated through a measurement target element such as a planar optical waveguide is output and reaches the reflection surface 362 at the other end of the optical fiber, the optical path is bent at 90 degrees with little loss, and then the core 364 of the optical fiber 360 is damaged. Proceed through. Unexplained reference numeral 366 is the cladding of the optical fiber 360.

In general, when the optical signal output from the planar waveguide using the optical fiber is combined, the coupling loss decreases as the mode size of the optical fiber is larger than the mode size output from the planar waveguide, and the dependency of the coupling loss on the x and y axes is also reduced. Decreases. Therefore, for low coupling loss and alignment, it is preferable to use a multimode optical fiber (a core diameter: about 62.5 μm) having a large core size, rather than using a single mode optical fiber (a core diameter: about 10 μm) as the optical fiber 360. It is advantageous.

Fig. 8 is a view comparing the numerical aperture of the output stage of the planar optical waveguide and the numerical aperture of the optical probe for output light employing the multimode optical fiber.

Since the numerical aperture of the multimode optical fiber has a higher value than the numerical aperture of the output terminal of the planar optical waveguide, most of the optical signals outside the planar optical waveguide are input to the multimode optical fiber 360. Particularly, as the optical signal output from the planar waveguide device travels in the air, the mode size increases gradually. The spherical interface formed by the clad 366 of the air and the optical fiber 360 has a cylindrical lens. It is solved by playing the role of the lens. That is, the size of the mode gradually decreases as the optical signal passes through the cladding 366 of the optical fiber 360. Therefore, in the optical probe for output light, the dependence of the center of the optical fiber and the planar waveguide on the x, y and z axes is very low.

9 to 11 show the results of measuring the coupling loss between the planar optical waveguide device and the optical probe. That is, FIG. 9 shows coupling loss with respect to the X-axis change of the optical probe at the output terminal, FIG. 10 shows coupling loss with respect to the Y-axis change of the optical probe at the output terminal, and FIG. 11 shows Z-axis change of the optical probe at the output terminal. The coupling loss for each is shown. As can be seen from these figures, there is almost no change in the coupling loss within about 30 ㎛ on the x, y axis, and similar coupling loss within 150 ㎛ in the z-axis.

12 is a diagram illustrating a schematic configuration of an apparatus for measuring characteristics of a planar optical device according to an exemplary embodiment of the present invention. In order to apply the measuring device of the present invention, the input / output terminal of an element such as a planar optical waveguide needs to be partially exposed because the exposure is inevitable in order to couple an optical signal between the optical element and the optical fiber of the probe. Because. On the other hand, the characteristic measuring device of the planar optical device of the present invention, a light source (not shown), the optical probe 300 for the input light shown in FIG. 3, the optical probe 350 for the output light shown in FIG. An alignment mechanism (not shown) for aligning the probes 300 and 350 and an optical signal sensing device (not shown) are provided. For convenience of illustration, the unit plane optical waveguide device 110 is completely cut in order to expose the input / output terminal of the planar waveguide device in FIG. 12, but the inclined surfaces of the optical fibers constituting the optical probes 300 and 350 are inserted. You may be exposed only to the extent possible. In addition, the alignment mechanism is moved to the x, y, z axis with the holder portions of the optical probes 300 and 350 fixed to the input / output terminals of the planar optical waveguide 110 and the optical probes 300 and 350. ).

13 and 14 illustrate a method of measuring optical characteristics of a planar optical waveguide device placed on a wafer by using a characteristic measuring device of a planar optical device according to an embodiment of the present invention. Referring to FIG. 13, in the planar optical waveguide device 110 on the wafer 100, the inclined surfaces of the optical probes 300 and 350 may be inserted into an input / output terminal thereof by using dicing equipment. A degree of trench is dug. Therefore, although the planar waveguide device is placed on the wafer, each input / output end is exposed for the characteristic measuring device of the present invention. Also, an alignment mechanism (not shown) may hold the optical probes 300 and 350, respectively, and x, y so as to align them to both input / output terminals of the respective planar waveguide elements identified by the trenches of FIG. , move in the z direction.

14 is a cross-sectional view taken along the line CC ′ of FIG. 13. Referring to FIG. 14, although the planar optical waveguide 110 on the wafer 100 is exposed to each input / output terminal by a trench formed by making a half cut through a dicing equipment, the planar optical waveguide 110 is exposed through the wafer 100. It is still attached to the planar waveguide device. Using an alignment mechanism (not shown), the optical probes 300 and 350 are moved freely over the wafer 100 to align the optical probes 300 and 350 at both input / output ends of the planar waveguide device separated by grooves. Then, an optical signal is input / output to measure optical characteristics. Although not shown for this purpose, an alignment mechanism equipped with a micrometer capable of fixing the optical probes 300 and 350 and precisely moving the wafer 100 is used. In addition, an alignment pattern may be used to recognize the target planar waveguide device 110 on the wafer 100 and to align the optical probes 300 and 350 to the input and output terminals of the desired planar waveguide device.

Subsequently, an optical signal generated by a light source (not shown) such as a laser diode is input to the planar optical waveguide device 110 through the optical probe 300 for input light, and the optical signal output through the planar optical waveguide device 110. Receives the light back to the optical probe for light 300 to convert the electrical signal through a photodiode to analyze the characteristics of the planar waveguide device 110.

The present invention is not limited to the above embodiments, and it is apparent that many modifications are possible by those skilled in the art within the technical spirit of the present invention.

According to the present invention as described above, it is possible to quickly measure the characteristics of the planar optical device placed on the wafer before the packaging process and determine whether there is a defect, thereby reducing the packaging cost.

1 (a) to (c) is a view showing a manufacturing process of a planar optical waveguide device according to the prior art;

2 is a view for explaining the coupling of the optical waveguide device and the optical fiber using the prior art;

3 is a schematic diagram of an optical probe for input light according to an embodiment of the present invention;

4 is a view partially showing an optical probe for input light according to another embodiment of the present invention;

FIG. 5 is a view showing a comparison of mode sizes of each other with respect to an interval between an end of an optical fiber and a planar optical waveguide in the optical probe for input light shown in FIG. 3; FIG.

FIG. 6 is a view showing a comparison of mode sizes according to a distance between an end of an optical fiber having the same configuration and a plane optical waveguide, which are side by side added to an optical fiber of the optical probe for input light shown in FIG. 3; FIG.

7 is a schematic diagram of an optical probe for output light according to an embodiment of the present invention;

Fig. 8 is a view comparing the numerical aperture of the output stage of the planar optical waveguide and the numerical aperture of the optical probe for output light employing the multimode optical fiber;

9 shows coupling loss with respect to the X-axis change of the optical probe at the output stage;

10 illustrates coupling loss with respect to the Y-axis change of the optical probe at the output stage;

11 illustrates coupling loss with respect to Z-axis change of the optical probe at the output stage;

12 is a view showing a schematic configuration of an apparatus for measuring characteristics of a planar optical device according to an embodiment of the present invention; And

13 and 14 illustrate a method of measuring optical characteristics of a planar optical waveguide device on a wafer by using a characteristic measuring apparatus of a planar optical device according to an exemplary embodiment of the present invention.

Claims (7)

delete delete delete delete A light source; An optical probe for input light for receiving an optical signal from the light source at one end thereof, and then refracting the optical axis of the optical signal at approximately 90 degrees on a reflective surface of the other end thereof to enter the input end of the planar optical element to be measured; An optical probe for output light for receiving the optical signal from the output end of the planar optical element through its side and refracting the optical axis of the optical signal at about 90 degrees on the reflective surface of the other end to output to one end thereof; ; A sensing device for sensing an optical signal from the optical probe for output light; Characteristic measuring apparatus of the planar optical device having a. 6. The apparatus of claim 5, further comprising an alignment mechanism for aligning the optical probe for input light and the optical probe for output light, respectively. The optical fiber of claim 5, wherein a separate optical fiber is further added in parallel with the input light optical probe and the output light optical probe near the other end of the input light optical probe and the output light optical probe. Characteristic measuring apparatus of the planar optical device, characterized in that serves as.