JPH0262958B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention provides a method for disposing a semiconductor PN junction element on a mount, and placing the semiconductor PN junction element on both sides of the mount with the semiconductor PN junction element sandwiched therebetween. This invention relates to an optical module manufacturing method for manufacturing a compact hybrid optical module in which a pair of optical input/output parts, such as an input/output waveguide or an input/output lens system, are arranged optically coupled to an active layer. be.

[Prior art]

As an example of this type of optical module, an example of the module structure of a laser diode optical switch (LD optical SW) having such a semiconductor PN junction element is shown in FIG. Here, 1 is a semiconductor PN junction element,
2, 2' are coupling ball lenses optically coupled to the active layer of the semiconductor PN junction element 1; 3, 3' are coupling focusing rod lenses optically coupled to the ball lens 2; 4, Reference numeral 4' denotes an input/output single mode fiber optically coupled to the rod lens 4, and each of these parts 1 to 3 is arranged on a modularization mount 5. V is a power supply terminal to the semiconductor PN junction element 1, and R is a current limiting resistor. 6
7 is an optical power meter coupled to the optical fiber 4, and 7 is a light source that makes light enter the optical fiber 4.

Conventionally, such optical modules have been manufactured using the following steps. First, the semiconductor PN junction element 1 is fixed to the mount 5, and a forward current equal to or higher than the oscillation threshold current is caused to flow from the current drive terminal V to emit light. After that, the optical axis of the ball lens 2 on one side is adjusted in the three axes directions of x, y, and z, and the semiconductor PN is
The output light from the junction element 1 is made into a parallel beam. Next, the optical axis of the converging rod lens 3 is adjusted so that the deflection of the optical power meter 6 is maximized.
Next, the optical axes of the other lens systems 2', 3', and 4' are aligned by the same procedure. Finally, instead of the optical power meter 6, a light source 7 is connected to the optical fiber 4' at the other end to form a PN as an optical switching element.
After adjusting the optical axes of the lens systems 3, 3' so that the light passing through the junction element 1 is maximized, each of these parts is fixed to a mount 5 to form an optical module.

Therefore, if the semiconductor PN junction element 1 is first fixed to the mount 5 and then the input/output optical waveguide is connected and fixed, the conventional method can be used, but if the input/output waveguide is formed in advance. In the case of manufacturing a hybrid integrated module by mounting an optical SW element in a location where the optical SW element is mounted, the above-mentioned conventional method cannot be applied.

Furthermore, when the LD optical SW element is used without temperature control, the reflectance of both end faces of the semiconductor PN junction element 1 needs to be 1% or less. Therefore,
When the semiconductor PN junction element 1 with low reflectance, which is important in practice, is used as an optical SW element, even if a large current is injected, laser oscillation does not occur, and the device operates as an LED.
Output optical power is very small.

Therefore, even when using the conventional manufacturing method, optical axis adjustment is difficult because the optical power is small. Moreover, when the optical axis is aligned using the optical power emitted by the LED operation, there is a drawback that the adjusted position is different from the optimal coupling position of the waveguide mode of the semiconductor PN junction element 1.

〔the purpose〕

SUMMARY OF THE INVENTION In order to solve these drawbacks, it is an object of the present invention to provide a method for manufacturing an optical module in which optical axis alignment is performed without causing the semiconductor PN junction element to emit light.

[Structure of the invention]

In order to achieve such an object, the present invention includes a semiconductor PN junction element disposed on a mount, and a semiconductor PN junction element disposed on both sides of the semiconductor PN junction element on the mount with the semiconductor PN junction element sandwiched therebetween. In manufacturing an optical module having a pair of optical input/output sections optically coupled to an active layer, the optical axes of the pair of optical input/output sections are aligned in advance, and the optical axes of the optical input/output sections are aligned with each other. The semiconductor PN is arranged such that the PN junction element is located between the pair of optical input/output parts.
determining the positional relationship between the element and the pair of optical input/output sections,
Optical signals modulated at different frequencies are simultaneously applied to both end faces of the semiconductor PN junction element from the pair of input/output sections, so that the terminal voltage change of the semiconductor PN junction element is maximized at each of the frequencies. The position of the semiconductor PN junction element is adjusted, and after the adjustment is completed, the semiconductor PN junction element is fixed on the mount.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

The basic structure of the present invention for detecting the optimum bonding position without causing the semiconductor PN junction element 1 to emit light will be explained with reference to FIG. Here, 7' is a light source laser diode having an oscillation wavelength comparable to that of the semiconductor PN junction element 1, 8 is a DC power supply for applying a bias current _I0 to this laser diode 7', and 9 and 9' are laser diodes. a condensing lens that condenses the output from the diode 7' onto the semiconductor PN junction element 1;
10 is an optical isolator placed between lenses 9 and 9', and 11 is a load resistance of semiconductor PN junction element 1.
An RF amplifier with a gain of 22 dB, for example, is coupled to R _L via a capacitor, and 12 represents a tracking scope that receives the output from the amplifier 11.

For example, 100M from this tracking scope.
Supplying a current fixed at Hz to the measurement light source 7',
The output light is modulated at 100 MHz and is injected into the active layer of the semiconductor PN junction element 1 through 20x objective lenses 9 and 9'. The RF power of the terminal voltage of this element 1 is measured with a tracking scope 12.

FIG. 3 shows the results of measuring the beam spot position dependence of the RF power detected by the terminal voltage of the semiconductor PN junction element 1 in this manner. Here, Δy represents the variation in RF power when the beam spot is displaced in the thickness direction of the active layer, Δx in the parallel direction of the active layer, and Δz in the optical axis direction.

From this result, the amount of displacement in which the RF power drops by 3 dB is
It can be seen that both Δx and Δz are ±5 μm, and Δy is ±1 μm. Therefore, instead of coupling using a lens, a light beam can be injected into the active layer from an input/output optical waveguide with a gap of about 10 μm, and the change in the terminal voltage of this PN junction element can be measured to generate light with high precision. Axis alignment can be performed.

The present invention was made based on such experimental results, and FIG. 4 is a block diagram showing an example of implementing the present invention. Here, 1 is the semiconductor to be fixed after optical axis alignment with the input/output waveguide for coupling.
It is a PN junction element. 13 and 14 are drivers for modulating the laser diodes 7' and 7'' as light sources at frequencies f ₁ and f ₂ , respectively; 15
is a selective level meter that detects RF power by tuning to the modulation frequencies f ₁ and f ₂ , and measures the input level by tuning independently to the signals of frequencies f ₁ and f ₂ from drivers 13 and 14. can do. Numerals 16 and 16' are cores of module input/output waveguides coupled to optical fibers 4 and 4', respectively, and a semiconductor PN junction element 1 is disposed between both cores 16 and 16'. 17 is a lead wire connected to this element 1, 18 is Au
This is a conductive layer for terminals, such as a plating layer.

FIG. 5 shows an example in which the waveguide portion shown in FIG. 4 is formed as an optical waveguide by a CVD method, a sputtering method, or the like. In FIG. 5, 21 is a substrate, which is made of silicon, ceramics, etc. in consideration of thermal conductivity. The above-mentioned conductive layer 18 for terminals is placed on this substrate 21, and a clad layer 22 is placed on the conductive layer 18 using the CVD method.
One continuous core 16, 16' is embedded in the core 2 to form an input/output waveguide. The middle of this waveguide is cut out to the conductive layer 18 using a reactive sputtering method, a dicing machine, or the like. A heat sink 23 is fixed to the notch with a conductive brazing agent such as solder 24. A semiconductor is placed on the heat sink 23.
A PN junction element 1 is mounted, with both end faces facing the input/output waveguide, and its active layer is connected to the core 16,1.
Make it face 6'.

The cladding layer 22 is used as an upper electrode, the lead wire 17 is connected thereto, and the conductive layer 18, which is in a conductive state by the brazing agent 24, is used as a lower electrode.
The voltage between these two electrodes is supplied to a selective level meter 15, and the voltage levels at frequencies f ₁ and f ₂ are measured. For this purpose, the selection level meter 15 is tuned to the frequencies f ₁ and f ₂ by signals from the drivers 13 and 14, and in that state, the light source 7'
and 7″ at frequencies f ₁ and f ₂ , respectively, to transmit optical signals modulated at different frequencies f ₁ and f ₂ from the input and output waveguides to the semiconductor.
Inject into the active layer of the PN junction element 1. Here, since the selection level meter 15 can be tuned independently to f ₁ and f ₂ , the optical axis can be aligned separately on the input side and the output side, and therefore the input and output waveguides and the semiconductor PN junction element can be easily aligned to the optimum position. Therefore, with the soldering agent 23 melted, the semiconductor PN junction element 1 is
is set at an optimal position, and the soldering agent 23 is cooled at that position to fix the element 1. Note that when the gap between the input/output waveguide and the semiconductor PN junction element 1 becomes 10 μm or more, the coupling loss increases, so it is necessary to match the beam spot size.

FIG. 6 shows an example in which an optical fiber is used as the input/output waveguide, and the cores 16, 16' and the cladding 22 are in the form of an optical fiber 30. In this example, first, the optical fiber 30 is fixed on the conductive layer 18 with the fixing layer 31. As the material for the fixing layer 30, adhesive or solder can be used. Next, using a reactive sputtering method or a dicing machine, a notch extending from the optical fiber 30 to the conductive layer 18 is made to expose the conductive layer 18. At this stage, the core 16,
16' is made to protrude and act as a condenser lens.
Next, the optical axis alignment described above is performed while the substrate 21 is heated to melt the brazing agent 24, and then the semiconductor PN junction element 1 is fixed at an optimal position.

In the present invention, since the optical axes of the input and output waveguides are aligned in advance, it is easy to adjust the position of the semiconductor PN junction element. Furthermore, since the adjusted position is fixed using a brazing agent, the manufacturing time of the optical fiber module is short and an extremely compact optical module can be manufactured.

Note that it is obvious that the method of the present invention can easily align the optical axis even in the case of a modular structure in which a lens system is used as an input/output section for a semiconductor PN junction element.

Furthermore, it is clear that the method of the present invention can be effectively applied to the modularization of devices capable of increasing optical output, such as laser devices.

The optical module manufactured by the method of the present invention can have various forms as described below.

(1) Light emitting module By using semiconductor PN junction elements that emit light from both sides of the active layer, light is extracted from the input/output waveguides on both sides.

(2) Switch module Inputs light from the input waveguide to the semiconductor PN junction element, and controls whether or not current flows through the semiconductor PN junction element to extract or block the output light from the output waveguide. Take control.

(3) Amplification module By flowing a forward current below the oscillation threshold through the semiconductor PN junction element, the amplified optical signal is extracted from the output waveguide only when the optical signal is incident from the input waveguide.

An optical module having the above-mentioned functions can be used as one basic structural unit in an optical integrated circuit.

〔effect〕

As explained above, according to the present invention, semiconductor
Since the optical axis alignment is performed by injecting optical signals modulated at different frequencies from both the input and output parts of the PN junction element into the semiconductor PN junction element, there are the following advantages.

(1) Even completely non-reflective elements can be made into modules.

(2) High reliability because no current is injected into the semiconductor PN junction element to cause it to emit light during assembly.

(3) Optical axes on the input and output sides can be adjusted simultaneously.

(4) Production time is short.

(5) High displacement detection sensitivity.

(6) Production automation is easy.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the conventional optical switch module manufacturing method, Figure 2 is a block diagram showing the principle of the measurement system in the present invention for measuring the terminal voltage of a semiconductor PN junction element, and Figure 3 is the same as that of Figure 2. Semiconductor in measurement system
A diagram showing the beam spot position dependence of RF power detected by the terminal voltage of a PN junction element, FIG. 4 is a block diagram showing a system for implementing the optical switch module manufacturing method of the present invention, and FIG. A cross-sectional view showing an example in which a deposited optical waveguide is used as the waveguide in FIG.
FIG. 6 is a cross-sectional view showing an example in which an optical fiber is similarly used as the waveguide. 1... Semiconductor PN junction element, 2... Ball lens,
3... Focusing rod lens, 4... Optical fiber,
5...Module mount, 6...Optical power meter, 7, 7', 7''...Laser diode for light source,
8...DC power supply, 9,9'...Condensing lens, 1
0... Optical isolator, 11... RF amplifier, 1
2... Tracking scope, 13, 14... Driver, 15... Selection level meter, 16, 1
6'...Core of input/output optical waveguide, 17...Lead wire, 18...Conducting layer, 21...Substrate, 22
... Cladding layer, 23 ... Heat sink, 24 ...
...brazing agent, 30...optical fiber, 31...fixing layer.

Claims (1)

[Scope of Claims] 1. A semiconductor PN junction element disposed on a mount, and an active layer of the semiconductor PN junction element disposed on both sides of the mount with the semiconductor PN junction element sandwiched therebetween. In manufacturing an optical module having a pair of optical input/output sections coupled to each other, the optical axes of the pair of optical input/output sections are aligned in advance, and the semiconductor PN junction element is connected to the optical input/output section. A positional relationship between the semiconductor PN element and the pair of optical input/output sections is determined so that the semiconductor PN element and the pair of optical input/output sections are located in the middle of the pair of optical input/output sections; Inject optical signals modulated by each frequency at the same time, adjust the position of the semiconductor PN junction element so that the terminal voltage change of the semiconductor PN junction element is maximized at each of the frequencies, and after the adjustment is completed. A method for manufacturing an optical module, characterized in that the semiconductor PN junction element is fixed on the mount.