JPH04207091A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To enable various kinds of problems in an airtight mold due to resin to be solved, production cost to be reduced, and element characteristic and reliability to be improved by providing a multilayer film reflection mirror consisting of a dielectric or a semiconductor at a light output part of a semiconductor laser element. CONSTITUTION:A semiconductor laser element 2 is mounted to a metal stem 1 by using a conductive paste or soldering materials such as AuSn, AuSi, PbSn, and In. Then, the semiconductor laser element 2 and an external connection electrode 3 are connected by a bonding wire 4. A metal wire or a metal ribbon such as Au, Cu, and Al are used for the bonding wire 4 and bonding is performed by supersonic connection, thermocompression, etc. After this, molding is performed by a resin with a flow behavior and resin is cured by heating, emitting light, leaving alone at a low temperature, etc. The semiconductor laser element 2 uses multilayer film reflection mirrors 6A and 6B according to a dielectric or a semiconductor for a reflection mirror at light output part.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a semiconductor laser device that has improved versatility and applicability through lower costs, and particularly relates to a stem and an external device on which a semiconductor laser element is mounted. The present invention relates to a semiconductor laser device in which connection electrodes are integrated by resin molding.

(Conventional technology) Semiconductor lasers are important as light sources for optical transmission, optical information processing, etc., and are coherent and high-speed.

Applications are being developed that take advantage of features such as high output. In optical transmission, they are used as directly modulated light sources that are much faster and have higher output than light-emitting diodes, and in optical information processing, they are regarded as important as small light sources that can provide narrow beams.

Furthermore, when applied to a sensor system, it is possible to construct a system that is faster, more sensitive, and more accurate than a light emitting diode, and studies are actively being conducted on this topic.

FIG. 29 shows an example of a conventional semiconductor laser device, which is a relatively popular semiconductor laser device used in compact disc players and the like.

101 is a metal base for a semiconductor laser mount, 10
2 is a semiconductor laser element. 103 is an electrical signal input terminal to the semiconductor laser element 102, and is connected to the semiconductor laser element 102 by a bonding wire 104. 105 is a metal cap for hermetic sealing, 106 is a glass window for laser light output, 107 is a photodiode for monitoring optical output, 104゛ is a bonding wire, 108 is a monitor output terminal from photodiode 107, 109 is a This is a ground electrode terminal.

The semiconductor laser device shown here has a built-in photodiode for monitoring, so it can be driven only by external electrical operation, and the semiconductor laser element is hermetically sealed, so it does not need to be affected by ambient humidity, etc. It has the characteristics that deterioration is not easily accelerated due to heat transfer, and because the optical system is externally attached, there are relatively few limitations on its uses. In addition, because the number of components is minimized, it is one of the lowest-priced semiconductor laser devices that combines the features of both electrically operated drive and hermetic sealing.

However, even in such a semiconductor laser device, a general popular light emitting diode (Light Emit
ting diodes (hereinafter referred to as LEDs), and moreover, it is not as easy to handle as LEDs. Generally, systems using semiconductor lasers as light sources are expensive systems and are not as popular as sensor systems, remote control systems, etc. that use LEDs as light sources.

This is because the semiconductor laser device shown in Fig. 29 is mounted very large compared to the thickness of the semiconductor laser element, has a complicated mechanism, and uses relatively expensive parts. Yes, there are problems such as high assembly costs,
Furthermore, the optical system installed externally is also expensive, its adjustment is complicated, and the assembly cost is high.

FIG. 30 shows another example of a conventional semiconductor laser device (Japanese Unexamined Patent Publication No. 2-125887). In this example, hermetic sealing is performed using an airtight resin mold to avoid using expensive parts and to reduce assembly costs. In the figure, 10
Reference numeral 7' denotes a photodiode for monitoring, which is designed to be compact and also serves as a submount for a semiconductor laser element, as is generally well known. Also, 11
0 is a resin mold made of a translucent resin, which was subjected to a curing treatment after flow molding.

In such a semiconductor laser device, the parts used are not very expensive, and the assembly process can be simplified, so that an inexpensive semiconductor laser device can be manufactured.

However, in the semiconductor laser device as shown in FIG. 30, although it is possible to reduce the cost, it is difficult to obtain device characteristics equivalent to those of the semiconductor laser device as shown in FIG. 29. That is, in the conventional example shown in FIG. 30, an LED is added to a general semiconductor laser device.
It is simply a combination of resin molds used in other devices, and the problems specific to semiconductor lasers are not taken into account. For this reason, the following problems (1) to (4) are likely to occur.

■Semiconductor lasers require coherent optical amplification using an optical resonator, and require at least a one-dimensional relative reflector. Especially low-priced edge-emitting semiconductor lasers often use crystal cleavage interfaces to create optical resonators; in this case, since the refractive index of the molding resin is higher than air, it is necessary to use crystal cleavage interfaces. is difficult. That is, as the external refractive index increases, the reflectance at the crystal cleavage interface decreases, and mirror loss increases for the semiconductor laser.

For example, if the refractive index of the resin is 1.5, GaAs-based, I
For nP-based semiconductor lasers, the interface reflectance is 10 to 15.
%, which is significantly lower than the approximately 30% for air. As a result, the oscillation threshold of the semiconductor laser device increases significantly, not only does the drive current increase, but in some cases, the laser operation of the device becomes impossible.

■In resin molds, the inside of the mold has a higher refractive index than the surrounding air, so light tends to become trapped, and the output from the rear mirror of the semiconductor laser may be superimposed on the output from the front mirror. This increases the noise component of the optical output due to the presence of lights with different phases, and in some cases causes beat fluctuations of the optical output due to optical homodyne.

(2) As mentioned above, a semiconductor laser requires an optical resonator and operates in the resonator mode. Therefore, when light from the outside, especially self-emitted light, returns, it becomes equivalent to operating in multiple optical resonators, and the operation of going back and forth between the respective optical resonator modes depending on the mode coupling strength, This tends to cause so-called mode jumps and generate noise. Therefore, it is desirable that the self-emitted light is not fed back as much as possible, but in the example shown in FIG. 30, there is a problem in that eight times the light reflected at the light output section is fed back. In resin molds, the mold resin tends to swell and deform due to temperature fluctuations, and as a result, the amount and direction of reflection at the light output part fluctuates slightly, causing the amount of light returned to the semiconductor laser to fluctuate, resulting in mode jumps. The generation of noise due to this also varies in a complex manner.

■Semiconductor lasers are prone to characteristic changes and element deterioration due to stress, and consideration must be given to stress and distortion caused by thermal expansion. Generally, materials with low moisture permeability are used as materials for resin molds, and it is not easy to make these materials have both a coefficient of thermal expansion and light transmittance close to those of semiconductor materials. For this reason, even in LEDs, resin molds are not used when the environmental conditions are extremely severe, and it is difficult to simply apply resin molding technology for LEDs to semiconductor lasers. In addition, since a semiconductor laser is a device that uses high current density injection and has a high heat generation density, care must be taken regarding heat dissipation.

(Problems to be Solved by the Invention) Conventionally, in semiconductor laser devices in which a semiconductor laser element is molded in resin, various problems peculiar to resin molding occur, and in particular, the mirror loss increases and the oscillation threshold value decreases. There is a problem in that noise is generated due to mode jumps due to rising and returning light, swelling and deformation of the mold resin, etc. Therefore, although resin molding can reduce manufacturing costs, it has the drawback of deteriorating device characteristics and reliability.

The present invention has been made in consideration of the above circumstances, and its purpose is to solve various problems in airtight resin molds, reduce manufacturing costs by resin molds, and improve element characteristics and reliability. The object of the present invention is to provide a semiconductor laser device that can be improved.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention employs the following structure.

That is, the present invention (claim 1) provides that a semiconductor laser element mounted on a stem is electrically connected to an external connection electrode, and a part of the stem and the external electrode are molded with a transparent resin together with the semiconductor laser element. The semiconductor laser device is characterized in that a multilayer reflector made of a dielectric or a semiconductor is provided at the light output portion of the semiconductor laser element.

Further, the present invention (claim 2) provides that the semiconductor laser element mounted on the stem is electrically connected to the external connection electrode,
In a semiconductor laser device in which the stem and part of the external electrode are molded with a transparent resin together with the semiconductor laser element, the semiconductor laser element has a periodic structure of refractive index or gain inside, and the periodic structure mainly allows light to be emitted. It is characterized in that the laser operation is performed upon return.

Further, the present invention (claim 9) provides that the semiconductor laser element mounted on the stem is electrically connected to the external connection electrode,
In the semiconductor laser device in which the stem and part of the external electrode are molded together with the semiconductor laser element using a translucent resin, the mold made of the translucent resin includes at least a first mold made of a soft resin and surrounding the first mold. It is characterized by being a multi-layer mold including a second mold made of hard resin.

(Function) According to the present invention (claims 1 and 2), the semiconductor laser element is a laser reflector in which a multilayer reflector made of a dielectric or a semiconductor is provided, or a periodic structure of refractive index or gain inside the element. Since a semiconductor laser device having the above characteristics is used, even if the refractive index around the semiconductor laser device increases in the resin mold, the characteristics of the device will not change significantly. Therefore, it is possible to minimize the deterioration of the characteristics of the semiconductor laser element, and it is possible to use resin molding with fewer problems such as noise, making it possible to realize a semiconductor laser device with excellent versatility, high reliability, and low cost. Become.

Further, according to the present invention (claim 9), the first mold made of a soft resin absorbs distortion, and the second mold made of a hard resin performs the original airtight sealing, so that the semiconductor laser element can be sealed. In addition to ensuring hermetic sealing, it is possible to reduce strain and stress on the element.

(Example) Hereinafter, the present invention will be described in detail with reference to the drawings.

<Example 1-1> Figures 1 and 2 show a schematic configuration of a semiconductor laser device according to a first example of the present invention, with Figure 1 being a perspective view and Figure 2 being a sectional view. be.

In the figure, 1 is a metal stem with good thermal conductivity (for example, Ni-plated C
u), 2 is a semiconductor laser element, 3 is an external connection electrode, 4 is a bonding wire, and 5 is an airtight mold made of translucent resin. In this embodiment, the semiconductor laser element 2 has a multilayer reflector made of dielectric or semiconductor, and suppresses the influence of a decrease in end face reflectance due to resin molding. Note that the specific structure of this semiconductor laser element 2 will be described later.

This device is assembled as follows.

First, the semiconductor laser element 2 is placed on the metal stem 1 using conductive paste, AuSn, or AuSi.

Mount using solder material such as Pb5n or In. At this time, it is preferable to use a mount using a solder material in consideration of heat dissipation of the semiconductor laser element 2, but in the case of an element that can operate with a very low current, it is also possible to mount it with a conductive paste. In addition, although it is mounted directly on the L-shaped metal stem 1 here, a submount with high thermal conductivity may be used in the middle, and the shape, material, size, etc. of the metal stem 1 are determined by its purpose and application. It can be set arbitrarily depending on the situation.

Next, the semiconductor laser element 2 and the external connection electrode 3 are connected using the bonding wire 4.

The bonding wire 4 is a metal wire or metal ribbon made of Au, Cu, A1, etc., and bonding is performed using ultrasonic connection, thermocompression bonding, or the like. At this time, the shape, material, size, extraction position, etc. of the external connection electrode 3 can be arbitrarily set as long as it does not block the optical output of the semiconductor laser element 2. Further, the metal stem 1 and the external connection electrode 3 may be made of the same material or different materials, and may be fixed with a lead frame or the like during the assembly process and then cut at the end.

Thereafter, molding is performed using a fluid resin, and the resin is cured by heating, light irradiation, leaving at low temperature, or the like. The fluid resin is a precursor of a mold resin or a fluidized material using a solvent, and a material that can be cured later is used. Examples of mold resins are epoxy resin, acrylic resin, and silicone resin.

Polyimide resin or the like may be used depending on the purpose.

It should be noted that the package form shown in FIGS. 1 and 2 is merely an example for explaining the embodiment, and it goes without saying that it can be arbitrarily set depending on the purpose and use. Examples of products with different package formats will be described later.

3 is a perspective view showing a schematic structure of the semiconductor laser device 2 used in the embodiment of FIG. 1, and FIG. 4 is a sectional view of the structure. As described above, this semiconductor laser element 2 uses multilayer film reflecting mirrors 6A and 6B made of dielectric or semiconductor for the reflecting mirror of the light output section. As an example of the semiconductor laser device 2, GaInAsP used in optical communication is used here.
/InP-based element.

In FIG. 4, 7 is an n-type InP substrate, 8 is an n-type InP substrate, and 8 is an n-type InP substrate.
Buffer layer, 9 is GaInAsP active layer, 10 is p-type 1
An nP cladding layer, 11 a p-type Ga I nAsP contact layer, and 12 and 13 electrodes. Also, 801,60
Reference numerals 2 and 603 denote dielectric or semiconductor films constituting the multilayer film reflecting mirror, each of which has an optical length (film thickness) of λ/4 to the oscillation wavelength λ of the semiconductor laser element 2. It is formed to be λ/2 grade. For example, 601 is a 5in2 λ/4 film, 602
is a λ/4 film of Si, 603 is a λ/2 film of SiO2,
A repeating structure of 601 and 602 is formed. At this time,
Since 603 is a λ/2 film, optically its presence or absence does not affect the reflectance, etc., but here it is provided as a surface protective film to protect the Si film 602. Formation methods include sputtering, CVD (Chemical
Vapor Deposition method 2, electron beam evaporation method, etc. may be used.

Here, the equivalent refractive index of the semiconductor laser element 2 is n O%
The refractive index of the S102 film 601 is nl, the refractive index of the Si film 602 is 02, the external refractive index is nE, and 601 and 60
When the number of pairs of 2 is N, the reflectance RN is RN − [fl−
(n E/n O) (n +/n 2 ) 2N1/
fl+(n I!/n O>(n +/n 2
)2Nl] 2...... (1) It can be expressed as follows.

As an example, when λ -1,3μm, no-3,2゜nl
-1,5, n2-2.8, R+ -(nh -1,0) -70%R+ -(nE
-1,5) -58% When N-=2, R2-(n+: -1,0) -90%R2= (n
E -1,5) -86%. n, = 1.0
corresponds to the normal case where the surrounding is air, nH-1,5 corresponds to the case when molded with a resin with a relatively high refractive index, and when a multilayer reflector is not used (N-0), as mentioned above, Ro ”' (nt −1,0) −27%R0−(r
+H-1,5)=13%.

As a result, the percentage of reflectance that decreases due to resin molding is 50% or more when a multilayer reflector is not used, less than 20% when a multilayer reflector is attached, and especially 5% or less when N≧2. I know it's worth it. Therefore, when airtightly molding a semiconductor laser device with resin, it is effective to use a multilayer reflector for the semiconductor laser element 2, suppressing the decrease in the reflectance of the laser resonator and reducing the consumption due to the increase in threshold current. It has the advantage of preventing power increase. Also,
As a result, self-thermal distortion caused by internal heat generation, which is particularly large in a resin mold, can be reduced, and a highly reliable semiconductor laser device can be realized even in a resin mold.

Note that the reflectance of the multilayer film reflector varies depending on the material of the dielectric film or semiconductor film, the number of nine layers, etc., and also varies depending on the wavelength of the laser beam. Optimization is possible depending on the purpose of use, such as low power operation or high output operation. Furthermore, it is also possible to expand the reflection wavelength range by gradually changing the configuration (thickness, refractive index, etc.) of the multilayer film.

<Example 1-2> FIGS. 5 and 6 show other examples of the semiconductor laser device 2 used in the example of FIG. Alternatively, this is an example of a semiconductor laser element that has a periodic structure of gain and causes laser oscillation due to the periodic structure. Here, examples having a periodic structure of refractive index are shown, and FIG. 5 is called a distributed feedback semiconductor laser, and FIG. 6 is called a distributed reflection semiconductor laser.

Reference numeral 14 in FIGS. 5 and 6 is a light guide layer, which has a shorter absorption edge wavelength than the active layer 9, and has a cladding layer (7 and 10 in this case).
) with a higher refractive index (for example, the above-mentioned Ga I n
It is composed of an AsP crystal (a mixed crystal with a composition whose absorption edge wavelength is shorter than that of the active layer). Periodic unevenness is provided on the top, bottom, or side surface of this optical guide layer 14 to provide equivalent fluctuations in the refractive index, thereby performing wavelength-selective optical feedback. In principle, these semiconductor laser devices do not require an external reflector and are capable of laser oscillation using only the internal structure of the semiconductor laser device. It has characteristics that can be realized by semiconductor laser devices.

These semiconductor laser elements are capable of oscillation in a single longitudinal mode due to their periodic structure, and in particular, structures with appropriate internal phase adjustment mechanisms, for example, in FIG. Stable single-longitudinal mode oscillation can be achieved using a structure in which the signal is shifted by 4. This internal phase adjustment mechanism is to compensate for the phase change of the reflected light due to the periodic structure of the refractive index, which has a different phase from the incident light, and λ is due to the periodic structure of the refractive index. Bragg reflection wavelength. In practice, in order to operate these semiconductor laser devices with stable single longitudinal mode oscillation, it is necessary to take measures to reduce the reflectance at the output end of the device. This means that in a semiconductor laser device like the one above,
This is because a kind of complex resonator state due to output end reflection tends to cause instability of the oscillation longitudinal mode.

This embodiment has a feature that provides other effects in such a case. That is, in this embodiment, since the semiconductor laser element is hermetically molded with resin, the reflectance of its light output portion is lower than when the surrounding area is air, as described above. Therefore, when a semiconductor laser device having a phase adjustment mechanism as described above is applied as an example, the complex resonator state due to output end reflection can be suppressed and stable single-longitudinal mode oscillation can be obtained relatively easily. It has this effect. Also,
If the light output part is simply molded with resin, the reflectance of the light output part will be reduced to 10 to 15% as mentioned above, but if the light output part is coated and then molded, the reflectance of the light output part will be reduced to 1%.
The following reflectance can be easily obtained.

Such coating is also performed in ordinary semiconductor laser devices, but in this embodiment, a new effect not seen before appears. For low-reflection coatings, the refractive index (no
A common method is to form a single layer of a transparent material with an optical thickness of λ/4 with nE)"2. Here, no is the equivalent refractive index of the semiconductor laser element, and nE is the external refractive index. For example, , no-3,2, nE -1 (air), a material with a refractive index of 1.79 may be used, and GaInAsP
/InP-based semiconductor lasers use silicon nitride as such a low-reflection coating material. At this time, since nE is fixed to approximately 1, the material to be used is limited, and it cannot be said that a material suitable for a semiconductor laser is necessarily used.

For example, in the case of silicon nitride, 5t3N4 is a chemically stable composition, but since the refractive index at that time is not necessarily a desired value, the composition is often shifted to a chemically unstable region. For this reason, leakage current is often generated on the surface of the semiconductor laser element and the element deteriorates over time.

On the other hand, in this example, nE is the refractive index of the molding resin, so the material used for coating is selected according to the material of the semiconductor laser element and the optimal coating method, and the value of nE is adjusted by adjusting the resin material. The advantage is that you can choose. This makes it possible to provide a coating with a low reflection of 1% or less using a material that is chemically stable and suitable for semiconductor lasers. Also,
With this coating, it is possible to protect the semiconductor laser element from the effects of the resin mold, and a high performance and highly reliable semiconductor laser device can be obtained.

<Example 1-3> FIG. 7 shows another example of the semiconductor laser device 2 used in the example of FIG.
This is an embodiment for preventing noise caused by the rear output being superimposed on the output light of the receiver output section). In this example, a multilayer film reflecting mirror 6A similar to that shown in FIG. 3 is used on the front surface, and a metal reflecting mirror with an intermediate insulating film 15 and a metal reflecting film 16 is used on the rear surface. In general, metals have a very high reflectivity for light with a frequency lower than the plasma frequency of free electrons (a wavelength longer than the wavelength of the plasma frequency), and unless the metal film is extremely thin, It is opaque.

FIG. 8 is a cross-sectional view of the structure of the semiconductor laser element shown in FIG. 7, in which 601, 602, and 603 are multilayer reflective mirrors configured in the same manner as in FIG. 4, 15 is an intermediate insulating film, and 16 is a metal reflective film. be. The intermediate insulating film 15 is made of SiO2, Al103. Si3
It is made of a material transparent to the oscillation wavelength of the semiconductor laser element, such as N4, and has a function of preventing short-circuiting of the pn junction due to the metal reflective film 16. In addition, as described later, the metal reflective film 1
It is also possible to adjust the phase of the reflected light from 6.

For example, SiO2 is used as the intermediate insulating film 15, and it is formed to a thickness of about 200 nm by a method such as the above-mentioned CVD method. Further, as the metal reflective film 16, for example, Au, Ag
, vacuum evaporation of metals such as Cu.

Provide a thickness of 1100n or more using a method such as sputtering. At this time, the adhesion strength of the metal reflective film 16 to the intermediate insulating film 15 may not necessarily be strong, so overcoating containing metals such as Ti and Cr may be performed. Conversely, the metal reflective film 16 may be made of Ti, Cr, Mo, W, etc., which have relatively strong adhesion strength, and in this case, it is desirable to attach a cover of Au, Pt, etc. to prevent oxidation corrosion.

These metals may be appropriately selected depending on process cost and desired reflectance.

By using the semiconductor laser device of this example, even in a resin mold, the output from the rear reflector will not be superimposed on the output light from the front reflector, and noise in the output light, especially phase noise and beat noise, will be reduced. There are benefits that do not arise. In addition, the rear metal reflector is not easily affected by external refractive index, so
Another advantage is that the reflectance does not change easily before and after the airtight resin molding. Note that the rear metal reflector may be a multilayer reflective mirror made of a dielectric or semiconductor with a very high reflectance, in which case the ratio of the rear output to the front output is 1.
If it is 0% or less, the noise problem will be relatively small.

<Example 1-4> FIGS. 9 and 10 show other examples of the semiconductor laser device 2 used in the example of FIG. 1, which has a periodic structure inside and is made of resin as in FIG. This embodiment is intended to prevent noise caused by superimposing the rear output light on the front output light, which is likely to occur due to the mold. Here, an example using a periodic structure of refractive index as in FIGS. 5 and 6, and an example using a metal rear reflector as in FIG. 7 are shown, but the periodic structure is a periodic structure of gain. Alternatively, the rear reflector may be a highly reflective multilayer reflector. These matters are similar to the embodiments described above.

In the semiconductor laser devices shown in FIGS. 9 and 10, the reflectance on the light output side is sufficiently reduced as in the case of FIGS. 5 and 6, but the rear reflector becomes highly reflective. , Figure 5,
If treated in the same manner as in the case of FIG. 6, it will be difficult to ensure the stability and reproducibility of the oscillation longitudinal mode. Therefore, special care must be taken in this example and the rear reflector (15 and 16)
It is necessary for the phase of the reflected light from to have a certain phase matching with respect to the internal periodic structure.

That is, it is sufficient that the phase change at the rear reflector has a value equivalent to the phase change of the reflected wave due to the periodic structure. In this case, the reflection due to the periodic structure is the so-called Bragg reflection, and the change in the phase of the reflected light at the rear reflector is (1+2m)π/2(m
″″o, 1°2.3. ). After this,
The reflection phase of the partial reflecting mirror can be changed by adjusting the thickness of the intermediate insulating film 15.

Here, the equivalent refractive index on the semiconductor laser element side is 01, the refractive index of the intermediate insulating film 15 is nz, the thickness is d1, and the complex refractive index of the metal film 16 is 03 (-u30iv3, i is an imaginary unit).
λ is the laser oscillation wavelength in vacuum. Then, define the following relationships.

β−2πdn2/λo −(2)ρ2i
-t(nz-u3) 2+v3 ” 1/1(nz
+u3) 2+v32)-(3)φ23''tan-'
+2 n 2 V.

/ (u 32+v 3' n 2') l... (
4) r lz-(n+-n 2 )/(nl ten n2
) - (5) Using these values, the reflectance Rm and the reflected light phase φm of the rear reflecting mirrors in FIGS. 8, 9, and 10 can be expressed as follows.

Rm = 1rs22+p zx24p2r+zl
)23 C08(llzi+2β))/(l+r+
22 ρ 2i'+2r+2ρ 23 Co9(φ2
3+2β))... (6) φm -tan-'[lρ23(1-rtz2)sin
(φ2.+2β month/ (rtz(1+p23')+p2
i(1+r+□2) Co5(φ2.+2β month)...
... (7) Therefore, the reflectance of the rear reflector and the reflected light phase can be designed and optimized using these equations, and as shown in Fig. 9 and 1.
In the case of figure 0, φm~(1+2m)π/2 (m-0,1
, 2, 3...).

<Example 2-1> Fig. 11 is a perspective view showing a schematic configuration of a second example of the present invention. This is an example in which measures are taken against reflected light.

In the embodiment shown in FIG. 1 described above, since the light output portion of the resin mold is flat, so-called near-end reflected light returning to the semiconductor laser element 2 is likely to occur.

For example, assuming that the refractive index of the molding resin is 1.5 and the reflectance of the optical output part of the semiconductor laser element 2 is 70%, the amount of light coupled back to the semiconductor laser element 2 is -30 dB when the thickness of the molding resin is 70 μm. It will be about. Generally, it is desirable that the return light to the semiconductor laser element is -30 dB or less, and if it is -60 dB or less, there is almost no problem. Therefore, in the case of FIG. 1, the distance from the semiconductor laser element 2 to the inner and outer ends of the molded resin may be set to 70 μm or more, but if it becomes too thick, the beam will spread and direct coupling to an optical fiber or the like will become difficult.

If the thickness of the molding resin is at most 200 μm or less, there will be little problem with ordinary optical fibers.

However, when the reflectance of the leading inner end of the semiconductor laser device is low, for example, in the case of the semiconductor laser devices shown in FIGS. 5 and 6, it is difficult to suppress the reflected return light in the embodiment shown in FIG.

Therefore, in the embodiment shown in FIG. 1, it is possible to use a method of slanting the light emitting surface of the mold resin as a countermeasure against reflected return light. This is because the mold resin output surface of the embodiment shown in FIG. This prevents it from returning to its original position. This makes it possible to suppress reflected return light even when the reflectance at the leading edge of the semiconductor laser element is low. There is a problem in that the wavefront of the beam differs depending on the direction and the direction perpendicular to the direction. Since this may cause astigmatism, it is necessary to use it depending on the purpose, and it is not suitable for boat fishing.

The embodiment shown in FIG. 11 is based on this background,
The light output portion of the molded resin is processed into a spherical shape to reduce the amount of light reflected back to the semiconductor laser element 2. FIG. 12 is a cross-sectional view of the structure of the embodiment shown in FIG. 11, and solid arrows and broken arrows in the figure schematically indicate the traveling direction of light. Although Fig. 12 shows a two-dimensional representation,
As shown in FIG. 11, this is an optical system that is approximately rotationally symmetrical with respect to the light output optical axis because it is processed into a spherical surface. As an example, FIG. 12 shows an optical system that generates parallel light, and in this case, the semiconductor laser element is arranged so that the light output section is at the focal point of the spherical processing section 17. As a result, the output light from the semiconductor laser element 2 becomes substantially parallel light and is output to the outside of the mold resin (solid arrow).

On the other hand, the light reflected at the mold resin boundary is once condensed and then spread as shown by the broken line arrow in the figure, and is greatly expanded while being reflected to the position of the semiconductor laser element 2. Therefore, the density of the reflected light decreases, and the amount of light returning to the semiconductor laser element 2 becomes extremely small. By processing the output surface of the molding resin into a spherical surface in this way, the amount of light returning to the semiconductor laser element 2 can be greatly reduced, making it possible to use a low-noise resin with little mode hop noise as described in the prior art section. A molded semiconductor laser device can be realized. Furthermore, since the spherical surface processing portion 17 also has the effect of a lens, it is effective in simplifying the external optical system and reducing the cost of the entire system.

<Embodiment 3> Up to this point, an edge-emitting type semiconductor laser device has been described, but this can be implemented in the same manner even with a surface-emitting type semiconductor laser device. FIG. 13 shows a third embodiment using a surface-emitting type semiconductor laser element 2', and is shown in the same mounting form as the embodiment of FIG. 12.

FIG. 14 is a cross-sectional view of the structure of the surface-emitting semiconductor laser device 2', in which 7 is an n-type InP substrate, 8' is an n-type 1nP cladding layer, 9 is a GaInAsP active layer, and 10'
is a p-type InP cladding layer, 18A is a multilayer reflector made of an n-type semiconductor, 18B is a multilayer reflector made of a p-type semiconductor,
19 is an Fe-doped semi-insulating 1nP buried layer, 20 is an n-type 1nP carrier blocking layer, and 21 is a p-type 1nP layer.
The contact layer 22 is an insulating protective film. 18A, 18
The multilayer film reflecting mirror B is, for example, I nP, A l l n
These are laminated films of As, Ga1nAsP (composition having a shorter absorption edge wavelength than the active layer 9), etc., and are alternately laminated with a thickness of optical length λ/4 as in the case of FIG. 4.

Here, a multilayer reflector made of an 18A n-type semiconductor is
When a multilayer film reflecting mirror made of p-type semiconductors such as P and Ga I nAsP118B is composed of InP and A I I nAs, carrier injection can be performed efficiently. Further, 8', 9.10' are configured so that the total thickness has an optical length that is an integral multiple of λ/2, and the thicknesses of 8' and 10' are made to be approximately the same. At this time, the active layer 9
Not only one layer but also a plurality of layers may be provided for each optical length of λ/4 in the region between 18A and 18B. The insulating protective film 22 is formed using, for example, 5 in 2 so as to cover the crystal growth interface on the side surface of the semiconductor laser element, thereby suppressing leakage current on the side surface of the element.

In the case of the surface-emitting type semiconductor laser element 2', optical output can be obtained in the normal direction of the semiconductor laser element mount surface, making it possible to simplify the assembly process and improve assembly accuracy compared to the case of the edge-emitting type semiconductor laser element 2. becomes. First of all, in the case of the surface-emitting semiconductor laser device 2', the mounting process of the semiconductor laser device 2', the mounting process such as wire bonding, and the airtight molding process with resin can all be performed on a flat surface, using a lead frame etc. This is because it is easy to carry out the assembly process continuously, and because the mounting accuracy of the semiconductor laser element 2' is almost determined only by the flatness of the mounting surface and the mounting position accuracy, there are basically few factors that reduce the assembly accuracy.

In the case of the edge-emitting semiconductor laser 2, in addition to the mounting accuracy, the flatness of the mounting surface, and the mounting position accuracy, the perpendicularity accuracy of the metal stem 1 and the mounting angle accuracy of the element are important factors. In addition, in the case of a surface-emitting type semiconductor laser device 2', it is easy to provide an insulating protective film by etching the periphery of the device as shown in FIG. This method has advantages such as being able to significantly reduce device short-circuit failures due to swelling of solder or conductive paste, and also being able to easily test device performance in the wafer state. Therefore, by using the surface-emitting type semiconductor laser element 2', it is possible to further reduce the cost, and it is possible to effectively achieve the object of the present invention.

In the following examples, the explanation will be made again using the edge-emitting type semiconductor laser device 2, which shows that the effects of the present invention are not impaired even with a semiconductor laser device under relatively unfavorable conditions. Therefore, it is easy to understand that the present invention can also be applied to a surface-emitting type semiconductor laser device 2'.

<Example 2-2> FIG. 15 shows an example in which reflected return light at the light output portion of the airtight resin mold is suppressed. In this embodiment, the light output portion of the molded resin is subjected to a non-flattening process using unevenness 23 to dissipate reflected light and suppress reflected return light.

FIG. 16 is a cross-sectional view of the structure, and a Fresnel lens or grating lens 23 can be used for the non-flattening process. An advantage of forming the Fresnel lens or grating lens 23 as a non-flattening process is that the height of the uneven portion can be made relatively small, and the convex surfaces can be positioned on the same surface, so that they can be handled in the same way as a flat surface in appearance. Since the output light from the uneven surface is a lens, the output beam can be optically designed, and the configuration of the external optical system can be simplified.

<Embodiment 4-1> FIG. 17 shows a fourth embodiment of the present invention, and is an embodiment in which the stem 1 for mounting the semiconductor laser element 2 and the external connection pins 3 are shaped like leads.

In the figure, 1 is a main lead that also serves as a metal stem, and 24 is a through hole for attachment to a heat sink. The through hole 24 may be provided as needed, and it is not necessarily necessary to provide it if unnecessary. Further, numeral 17 indicates anti-reflection processing of the mold resin, and here, spherical processing is taken as an example.

A feature of this embodiment is that it is easy to perform continuous assembly in the assembly process, and parts of glues 1 and 3 can be assembled by being fixed by a lead frame. Further, as shown in FIG. 18, since the mounting surface of the semiconductor laser element 2 is the tip end surface of the lead 1, the direction in which pressure is applied during assembly is the axial direction of each lead 1.3, which may cause deformation of the lead, mounting, etc. It has the feature of reducing wire bonding defects.

〈Example 4-2〉 Fig. 19 shows a fourth embodiment of the present invention, which is an example of a mounting form different from Fig. 17, in which the stem 1 on which the semiconductor laser element 2 is mounted is made of metal or thermally conductive insulation. This is an embodiment in which a body block is used, and the side surface thereof is exposed on almost the same plane as the mold resin. In the figure, 25 is an insulating post, which is used to fix the external connection bin 3.

In this example, as shown in FIG. 20, since the exposed surface of the stem 1 can be made large, the contact area between the heat sink and the stem 1 is increased when it is attached to the heat sink, thereby effectively dissipating the heat from the semiconductor laser element 2. can be done.

<Example 4-3> FIGS. 21 and 22 correspond to FIGS. 19 and 20, and are examples in which the direction of light output is changed in the same mounting form,
The effect is obtained in the same way as in the example shown in FIG. Note that in these embodiments, the external connection pin 3 is fixed to the stem 1 in advance through the insulating post 25, but this may be formed with a separate lead as shown in FIG. 17. Also,
When the stem 1 is a thermally conductive insulator, the stem 1 may be provided with metallized wiring.

<Example 5> Figure 23 shows a fifth example with a built-in monitor photodiode.
This embodiment is shown in a similar implementation form to the embodiment of FIG. In the figure, 26 is a monitor photodiode, 2
7 is a monitor output terminal, and 28 is a bonding wire, which monitors the output light from the semiconductor laser element 2 by receiving reflected light at the mold resin boundary.

FIG. 24 is a cross-sectional view of the structure of the embodiment shown in FIG. 23, in which a semiconductor laser element 2 and a monitor photodiode 2 are
6 is an example in which the spherical processing portion 17 is arranged confocal. 1st
As shown in Figure 2, when a simple spherical surface outputs parallel light, the reflected light tends to expand and dissipate before reaching the focal point. , and by shifting the focus from the focal point, the configuration shown in the figure is possible. However, the output light at this time does not become parallel light. Conversely, when emphasis is placed on parallel light output, the light output can be monitored by increasing the light receiving area of the photodiode 26, and a confocal arrangement is not necessarily required. Moreover, semiconductor laser device 2. Monitor photodiode 2
An efficient optical output monitor can be designed by appropriately selecting the mounting position of each of the elements 6, the resin refractive index, and the spherical shape.

<Example 6-1> Figure 25 shows semiconductor laser device 2 due to distortion of mold resin.
This is a sixth embodiment for preventing the deterioration of. 29 in the diagram
5 is a first mold made of soft resin, and 5 is a resin mold (second mold) similar to the other embodiments. Here, the first mold is made of, for example, a translucent silicone resin that is highly flexible even after curing, and the second mold is made of, for example, a translucent epoxy resin that is highly moisture resistant. As a manufacturing method, first the semiconductor laser element 2 is mounted and wire bonded, and then the first mold 29 is attached by a botting method and hardened. Thereafter, airtight molding is performed using the second mold 5 as in the other embodiments.

The feature of this embodiment is that the strain between the resin and the semiconductor laser element 2 due to resin molding or heat generation is eliminated by the first mold 2.
9, and the original purpose of the mold, hermetic sealing, is the second.
Since this is carried out using the mold 5, the semiconductor laser element 2, which is sensitive to strain and stress, can be protected while maintaining the characteristics of the resin mold, and a highly reliable resin mold type semiconductor laser device can be realized.

<Example 6-2> FIG. 26 is an improvement of the embodiment shown in FIG. 25, and is an example that can be applied even when the first mold 29 and the second mold 5 have different refractive indexes. In the embodiment shown in FIG. 25, since the first mold 29 is formed by a botting method, its shape is uncertain, and the laser beam is likely to be deformed between the first mold 29 and the second mold 5. Therefore, here, the first mold 29 is also created by a molding method in order to flatten the light output portion.

In this case, even if the first mold 29 and the second mold 5 have different refractive indexes, the present invention can be implemented in the same way as the other embodiments by simply correcting the focal length by the refractive index difference.

<Example 6-3> %! FIG. 27 shows an example in which when the first mold 29 and the second mold 5 have different refractive indexes, the difference in refractive index is actively utilized. Here, it is assumed that the refractive index of the first mold 29 is lower than the refractive index of the second mold 5, and the light output part of the first mold 29 is processed with a concave spherical surface 17', and the second mold 29 is The light output portion of the mold 5 is processed into a convex spherical surface 17' to form two spherical surfaces. By doing this, jfW251ffl.

In addition to the features of the embodiment shown in FIG. 26, the degree of freedom in optical design is increased, and the
It has the characteristic that it can reduce the amount of reflected light between the two.

<Example 6-4> Fig. 28 shows the first mold 29 and the second mold of the embodiment shown in Fig. 27.
This shows a case where the refractive index relationship with the mold 5 is reversed, and the light output portion of the first mold 29 is spherically processed to have a convex shape of 17°. In this embodiment as well, the same effect as in the embodiment shown in FIG. 27 can be obtained.

Note that the present invention is not limited to the above-mentioned embodiments, and its shape, material, etc. can be modified in various ways, and further applications include, for example, incorporating a built-in optical isolator or integrally molding an optical connector. be.

[Effects of the Invention] As detailed above, according to the present invention, the performance and reliability are comparable to those of semiconductor laser devices that are not molded with resin, and while making it possible to add new functionality, This makes it possible to realize a semiconductor laser device that can be manufactured at a low cost.

[Brief explanation of the drawing]

1 to 10 are diagrams for explaining a first embodiment of the present invention, FIGS. 11 and 12 are diagrams for explaining a second embodiment of the present invention, and FIGS. 13 and 14 are diagrams for explaining a second embodiment of the present invention. The figure is a diagram for explaining the third embodiment of the present invention, Figures 15 and 16 are diagrams for explaining the second embodiment of the invention, and Figures 17 to 22 are diagrams for explaining the second embodiment of the present invention. FIGS. 23 and 24 are diagrams for explaining the fifth embodiment of the present invention, and FIGS. 25 to 28 are diagrams for explaining the fourth embodiment of the present invention.
FIGS. 29 and 30 are diagrams for explaining the embodiment of FIG. DESCRIPTION OF SYMBOLS 1... Stem, 2.2'... Semiconductor laser element, 3... External connection electrode, 4... Bonding wire, 5... Airtight mold with resin, 6A, 6B... Multilayer film reflection Mirror, 14... Light guide layer, 15... Intermediate insulating film, 16... Metal reflective film, 17... Spherical surface processing part, 23... Uneven processing part, 26... Photodiode for monitor . Applicant's Representative Patent Attorney Hikosuke Takeshi Suzue Figure 1 Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 11 Figure 13 Figure 14 Figure 15 Figure 16 Figure 18 Fig. 19 Fig. 20 Fig. 21 Fig. 22 Fig. 23 Fig. 24 Fig. 25 Fig. 27 Fig. 29 Fig. 30

Claims (9)

[Claims] (1) A semiconductor laser device in which a semiconductor laser element mounted on a stem is electrically connected to an external connection electrode, and a part of the stem and the external electrode are molded with a transparent resin together with the semiconductor laser element, 1. A semiconductor laser device characterized in that a multilayer reflector made of a dielectric or a semiconductor is provided at a light output portion of a laser element. (2) A semiconductor laser device in which a semiconductor laser element mounted on a stem is electrically connected to an external connection electrode, and a part of the stem and the external electrode are molded with a transparent resin together with the semiconductor laser element, A semiconductor laser device characterized in that a laser element has a periodic structure with a refractive index or gain inside, and a laser operation is performed mainly by optical feedback by the periodic structure. (3) The semiconductor laser according to claim 1 or 2, wherein the semiconductor laser element is provided with a high reflection mirror or a metal reflection mirror for preventing laser light leakage on one side of the optical resonator direction. Device. (4) The light emitting part of the mold made of the transparent resin is subjected to an inclined process, a spherical process, or a non-flattening process to reduce light returning to the semiconductor laser element. 4. The semiconductor laser device according to any one of 3 to 3. (5) The semiconductor laser device according to any one of claims 1 to 4, wherein the stem comprises a lead, and the semiconductor laser element is mounted on the tip end surface of the lead. (6) The stem is made of a metal block, the semiconductor laser element is mounted on a tip end surface or a tip side surface of the metal block, and at least one side surface or two opposing sides of the metal block are exposed; 5. The semiconductor laser device according to claim 1, wherein at least one of the exposed surfaces forms substantially the same plane as a mold surface made of the light-transmitting resin. (7) A light-receiving element for monitoring optical output is molded together with the semiconductor laser element in the light-transmitting resin, and the laser output light reflected by the light emitting part of the mold made of the light-transmitting resin is transmitted to the light-receiving element. 7. The semiconductor laser device according to claim 1, wherein the semiconductor laser device receives light. (8) The mold made of the light-transmitting resin includes a first soft mold that molds at least the semiconductor laser element, and a second hard mold that molds the first mold, the stem, and a part of the external connection electrode. 8. The semiconductor laser device according to claim 1, comprising: a mold. (9) A semiconductor laser device in which a semiconductor laser element mounted on a stem is electrically connected to an external connection electrode, and a part of the stem and the external electrode are molded with a transparent resin together with the semiconductor laser element, A semiconductor laser device characterized in that the mold made of photoresist is a multi-layer mold including at least a first mold made of a soft resin and a second mold made of a hard resin surrounding the first mold.