JPH0262956B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the manufacture of a laser diode module in which a laser diode chip, a condensing element, and an output optical fiber are mutually fixed in optimal positions.

<Prior Art> FIG. 1 shows an example of the configuration of a conventional laser diode module. The coupling end face of the output optical fiber 1 faces the condensing ball lens 2, and the condensing ball lens 2
faces the active layer of the laser diode chip 3. The laser diode chip 3 is mounted on a heat sink 4, and a current injection wire 5 is connected to the laser diode chip 3. When assembling these to manufacture a laser diode module, the following steps are performed. First, the laser diode chip 3 is bonded to the heat sink 4, the current injection wire 5 is attached to the laser diode chip 3, and a current is passed through it to cause the laser diode chip 3 to emit light. Next, the optical axis of the condensing ball lens 2 is finely adjusted in three directions, that is, the x, y, and z directions perpendicular to each other, so as to be adjusted to an optimal position relative to the active layer of the laser diode chip 3. Furthermore, the optical axis of output optical fiber 1 is set to 3.
By adjusting the directions, the optical axes of the output optical fiber 1, the condensing ball lens 2, and the laser diode chip 3 are aligned with each other, and the spacing between them is optimized, that is, the optical output is They are adjusted so that the maximum amount of light is emitted from the output optical fiber 1 and fixed to each other.

In this way, in the conventional method, the optical axis was adjusted and fixedly assembled while the laser diode was oscillating, so adjustments had to be made with the heat sink 4 attached, and the assembly had to be done with the power turned on. There were drawbacks such as problems with reliability due to failures, and poor manufacturing efficiency. In other words, if the laser diode chip 3 is allowed to oscillate without hermetic sealing, it may deteriorate and its reliability may decrease. , it becomes difficult to adjust the condensing ball lens 2 and the laser diode chip 3 at the same time.

As for the construction method of the laser diode module, in addition to the so-called separate lens method in which the output optical fiber 1 and the condensing ball lens 2 are separated as shown in FIG. 1
A configuration is known in which an element with a light condensing function, such as a microlens, is provided on the coupling end face. This type of construction method is called the advanced lens method, and for example, "Optical and Quantum Electronics Research Group Materials"
OQE76-85” was invited. This method also has the same problems as the individual lens method, which arise from assembly with the laser diode chip emitting light.

In the following embodiments, a tip lens method will be described, but a laser diode module can also be manufactured using an individual lens method using substantially the same procedure.

<Summary of the Invention> In order to solve these problems, the purpose of the present invention is to mutually connect the output optical fiber, the condensing element, and the laser diode chip in an optimal state while the laser diode chip remains in a non-emitting state. An object of the present invention is to provide a method for manufacturing a laser diode module that is fixed to a laser diode module.

According to this invention, the reference light is input from the output end of the output optical fiber, and the reference light is irradiated from the coupling end face of the output optical fiber onto the end face where the active layer of the non-emitting laser diode chip appears. ,
The reflected light from the end face is incident on the output optical fiber, and the intensity of the reflected light emitted from the output optical fiber is measured.The intensity of the reflected light is determined by the refractive index distribution depending on the end face structure of the laser diode chip. The distribution is detected, and based on this, each optical axis of the laser diode chip, output optical fiber, and condensing element is determined.
Adjust the spacing between them to be optimal.

<Embodiment> FIG. 2 is a configuration diagram for explaining an embodiment of the present invention. Reference light from a light source 6 is incident on the output surface of the output optical fiber 1 via a half mirror 7. In this example, the present invention is applied to the tip lens method as described above, and the coupling end face of the output optical fiber 1 is equipped with a light-condensing device such as a microlens formed by etching or the like. Element 8 is attached. The reference light from the output optical fiber 1 is irradiated through the condensing element 8 onto the end face of the laser diode 3 where the active layer is exposed. The reflected light is coupled to the output optical fiber 1 via the condensing element 8, and the reflected light is input to the power meter 9 via the half mirror 7.

Light having the same wavelength as that emitted from the laser diode chip 3 is input from the light source 6 to the output optical fiber 1, and the laser diode is connected so that the beam spot focused by the focusing element 8 hits the active layer of the laser diode chip 3. Adjust the position by slightly moving tip 3. By the way, if the reflected light power when light is perpendicularly incident on a medium with a refractive index n is P, then the variation ΔP in the reflected light power when there is a variation Δn in the refractive index is expressed as follows.

ΔP/P=4/n ₂ −1·Δn (1) From equation (1), it can be seen that the reflected light power varies in proportion to the variation in the refractive index. Therefore, if there is a difference in refractive index between the active layer and the cladding layer of the laser diode chip 3, the active layer can be detected as a change in the reflected light power. That is, the active layer can be detected by measuring the level of the reflected light using the power meter 9 and detecting the intensity distribution of the reflected light based on the refractive index distribution depending on the structure of the end face of the laser diode chip 3.

FIG. 3 shows the structure of a GaAlAs/GaAs double heterostructure buried laser diode. FIG. 4 shows the refractive index profile along line A-A' in FIG. Nn type
A cladding layer 12 of Ga _0.6 Al _0.4 As is formed in the center of the GaAs substrate 11, and a
An active layer 13 of GA _0.95 Al _0.05 As is formed, and a P-type cladding layer 1 of Ga _0.6 Al _0.4 As is formed thereon.
4. P-type GaAs layers are sequentially formed. N-type Ga _0.6 Al _0.4 As cladding layers 16 and 17 are formed on the substrate 11 with the laminated portions of the cladding layer 12, active layer 13, cladding layer 14, and GaAs layer 15 in between and in contact with them. The active layer 13 has a thickness of about 0.2 μm and a width of about 3 μm, and each of the cladding layers 12 and 14 has a thickness of about 2.5 μm. The refractive index of the active layer 13 in this structure is 3.565,
The refractive index of the cladding layers 12, 14, 16, and 17 is 3.32. Therefore, from equation (1), ΔP/P=
0.084, active layer 13 and crazing layer 1
The variation in reflected light power between No. 2 and No. 2 and No. 14 is about 8% or more. Cladding layers 12, 14 and active layer 13
The thickness of the laser beam is approximately 2.5 μm and 0.2 μm, and the size of the irradiated beam spot can be reduced to approximately 2 μm or less by the condensing element 8, so there is no risk of the beam spot being removed from the cladding layer and the active layer. , the active layer 13 can be detected as the position of maximum reflected light power. Note that since the refractive index of the active layer 13 is maximum in the lateral direction as well, the position can be adjusted by the maximum value of the reflected light power. In this way, by converting the reflected light power into an electrical signal using the power meter 9 and incorporating it into a feedback control system for optical axis alignment, it is possible to automatically align the optical axis.

As mentioned above, the present invention can also be applied to an individual lens system in which the condensing element is provided separately from the output optical fiber 1 as shown in FIG.

<Effects> As explained above, according to the present invention, the optical axes of the output optical fiber, the laser diode chip, and the condensing element are aligned in a state in which no current flows through the laser diode chip, that is, in a non-emission state. It has the following advantages.

(1) Reliability is improved because there is no risk of the laser diode chip being degraded by light emission.

(2) High displacement detection sensitivity (3) Optical axis alignment can be easily automated because it does not need to be performed in an inert gas atmosphere.

[Brief explanation of drawings]

Fig. 1 is a block diagram illustrating optical axis alignment of a conventional laser diode module, Fig. 2 is a block diagram illustrating optical axis alignment of the laser diode module manufacturing method of the present invention, and Fig. 3 is a block diagram illustrating optical axis alignment of a conventional laser diode module. Figure 4 is a cross-sectional view showing the structure of Figure 3.
FIG. 3 is a diagram showing a refractive index profile of a cross section taken along the AA line. DESCRIPTION OF SYMBOLS 1... Output optical fiber, 2... Condensing ball lens as a condensing element, 3... Laser diode chip, 4... Heat sink, 5... Current injection wire, 6... Light source, 7... Half mirror, 8... Concentrating element, 9... Power meter, 12, 14... Cladding layer, 13... Active layer.

Claims (1)

[Claims] 1. A coupling end face of an output optical fiber is arranged near the laser diode chip via a condensing element, and these laser diode chips and condensers are arranged so that the output light from the laser diode chip is coupled to the output optical fiber. In a method for manufacturing a laser diode module in which an optical element and an output optical fiber are fixed to each other, a reference light is input from the output end of the output optical fiber, and the reference light is input from the coupling end face of the output optical fiber. The end face of the laser diode chip in a non-emitting state is irradiated, the reflected light from the end face of the laser diode chip is recombined to the output optical fiber, and the reflected light is refracted depending on the structure of the end face of the laser diode chip. The intensity distribution due to the rate distribution is detected at the output end of the output optical fiber, and the optical axes of the laser diode chip, the output optical fiber, and the condensing element and the spacing therebetween are adjusted to be optimal. Features a manufacturing method for laser diode modules.